Scientific Publications

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George B. Abadir, Konrad Walus & David L. Pulfrey, Bias-dependent amino-acid-induced conductance changes in short semi-metallic carbon nanotubes, Nanotechnology, Vol. 21(1), pp. 015202 (8pp) (2010)
Abstract    BibTeX    DOI: 10.1088/0957-4484/21/1/015202   
Abstract: We study the interaction between short semi-metallic carbon nanotubes and different amino acids using molecular dynamics and ab initio (density functional theory/non-equilibrium Green's function) simulations. We identify two different mechanisms of nanotube conductance change upon adsorption of amino acids: one due to the change of the coordinates of the nanotube arising from van der Waals forces of interaction with the adsorbed amino acid; and one due to electrostatic interactions, which appear only in the case of charged amino acids. We also find that the transport mechanism and the changes in the conductance of the tube upon amino acid adsorption are bias dependent.
BibTeX:
@article{Abadir2010,
   title = {Bias-dependent amino-acid-induced conductance changes in short semi-metallic carbon nanotubes},
   author = {Abadir, George B. and Walus, Konrad and Pulfrey, David L},
  
   journal = {Nanotechnology},
  
  
   volume = {21},
   number = {1},
   pages = {015202 (8pp)},
   year = {2010},
   keywords = {area:molecular electronics,area:nanotubes,nanotubes},
   area = {molecular electronics,nanotubes}
   doi = {10.1088/0957-4484/21/1/015202},
  
}
George B. Abadir, Konrad Walus & David L. Pulfrey, Basis-set choice for DFT/NEGF simulations of carbon nanotubes, Journal of Computational Electronics, Vol. 8(1), pp. 1--9 (2009)
Abstract    BibTeX    DOI: 10.1007/s10825-009-0263-5   
Abstract: We investigate the effect of the choice of the basis set on the results of ab initio (density functional theory/non-equilibrium Green's function) calculations of the bandgap of semiconducting carbon nanotubes, and near-zero-bias conductance of metallic carbon nanotubes. Both ideal and deformed carbon nanotubes are studied, as well as nanotubes with an adsorbed biomolecule. The results show that the near-zero-bias conductance of armchair nanotubes can be calculated accurately with a minimal basis set, with the exception of the (2,2) tube, where a polarized basis set is necessary to accurately predict the metallic behaviour of this tube. For zigzag tubes, a double-zeta polarized basis set is in general required for accuracy in bandgap and near-zero-bias conductance calculations.
BibTeX:
@article{Abadir2009a,
   title = {Basis-set choice for DFT/NEGF simulations of carbon nanotubes},
   author = {Abadir, George B. and Walus, Konrad and Pulfrey, David L},
  
   journal = {Journal of Computational Electronics},
  
  
   volume = {8},
   number = {1},
   pages = {1--9},
   year = {2009},
   keywords = {Basis sets,Carbon Nanotubes,DFT,NEGF,area:nanotubes},
   area = {nanotubes}
   doi = {10.1007/s10825-009-0263-5},
  
}
George B. Abadir, Konrad Walus & David L. Pulfrey, Comment on "curvature effects on electronic properties of small radius nanotube" [Appl. Phys. Lett. 91, 033102 (2007)], Applied Physics Letters, Vol. 94(17), pp. 176101 (2009)
Abstract    BibTeX    DOI: 10.1063/1.3130094   
Abstract: Zeng et al. 1 studied curvature effects in ͑2,2͒ and ͑3,3͒ carbon nanotubes using the density functional theory/ nonequilibrium Green's function ͑DFT/NEGF͒ approach. The main conclusions were that due to curvature effects, the ͑2,2͒ nanotube is a semiconducting tube with an energy gap of 0.68 eV and the ͑3,3͒ tube exhibits a negative differential conductance at a bias of Ϯ1.8 V. The purpose of this comment is to demonstrate that a different conclusion about the properties of a ͑2,2͒ tube can be reached by choosing a different basis set for the simula-tions. Also, the length of the electrodes used can significantly affect the results. Further, the use of a polarized basis set for a ͑3,3͒ tube indicates an extended range over which there is a negative differential conductance. Figure 1 in Ref. 1 shows the simulated structures for the two aforementioned tubes in the central region of a two-probe system. Each of the electrodes consists of just one period ͑0.2463 nm͒ of each tube. An important assumption in the DFT/NEGF approach is that the electrodes are semi-infinite, meaning that the electrodes are assumed to be re-peated infinitely in the transport direction and that they have bulklike properties. 2 The short electrodes described above may well allow an interaction between the central region and the repeated images of the electrodes. To verify this, we simulated the structures with four periods of each tube in the central region and the same short electrodes using the pack-age ATOMISTIX. 3 In Ref. 1, the basis set used is not men-tioned so we started with the single-zeta ͑SZ͒ basis set ͑the simplest available basis set in ATOMISTIX͒ within the local density approximation that was used in Ref. 1. The results for the transmission coefficient as a function of energy are shown in Fig. 1, and the 0.68 eV gap of the ͑2,2͒ tube is exactly reproduced. The simulations were repeated with the same basis set but the electrode length was increased to two periods ͑0.4926 nm͒. The results are also shown in Fig. 1 and the corresponding gap is only 0.39 eV. Fixing the length of the electrodes and using the double-zeta ͑DZ͒ basis set gives a very narrow gap of 0.1 eV. Finally, including polarization by using both the SZ polarized ͑SZP͒ and the DZ polarized ͑DZP͒ basis sets shows a metallic tube with a zero gap rather than a semiconducting tube with a sizable bandgap, as pre-dicted using the input parameters in Ref. 1. In fact, including polarization in the basis set is essential to accurately describe high-curvature effects. 4 Taking into account all of the above, we suggest that inclusion of polarization in the basis set is necessary for accurate simulation of very small-radius tubes, such as the ͑2,2͒. We note that the DZ set is more complete than the SZP set, 3 and it predicts a small-bandgap tube while the SZP pre-dicts a zero-gap metallic tube, as does the DZP set. This implies that the results of the polarized sets cannot be due to any overcompleteness of the DZP set but rather are a result of the polarization per se. Moreover, barring overcomplete-ness in the basis set, the total energy of the system ͑E tot ͒ should decrease using a more complete basis set, i.e., E tot is variational with the number of basis functions. 5 Indeed, E tot was Ϫ1098.188 Ry for the SZ set, Ϫ1104.014 Ry for the SZP set, Ϫ1107.034 Ry for the DZ set, and Ϫ1109.838 Ry for the DZP set. This assures that the DZP set is not over-complete. We also calculated E tot using the DZ double-polarized ͑DZDP͒ basis set and found it to be Ϫ1109.143 Ry, i.e., it is larger than that predicted by the DZP basis set. This suggests that the DZDP basis set would be an overcomplete basis set for this system. Regarding the second conclusion in Ref. 1, performing the current-voltage calculations using a DZP basis set for a 12-unit-cell ͑3,3͒ tube does indeed indicate a negative con-ductance, though it extends over two voltage ranges: Ϫ2 to Ϫ1.28 and 1.28 to 2 V, instead of the narrow ranges around Ϯ1.8 V, as mentioned in Ref. 1. In conclusion, we have demonstrated that the input simulation parameters can have a profound effect on the re-sults of ab initio simulations. We suggest that inclusion of the polarization in the basis set is necessary for accurate simulation of very small-radius nanotubes, and we point out that overcompleteness is not a problem with ͑2,2͒ tubes when using a DZP basis set. a͒
BibTeX:
@article{Abadir2009,
   title = {Comment on "curvature effects on electronic properties of small radius nanotube" [Appl. Phys. Lett. 91, 033102 (2007)]},
   author = {Abadir, George B. and Walus, Konrad and Pulfrey, David L},
  
   journal = {Applied Physics Letters},
  
   publisher = {AIP},
   volume = {94},
   number = {17},
   pages = {176101},
   year = {2009},
   keywords = {ab initio calculations,area:nanotubes,carbon nanotubes,density functional theory,elemental semiconductors,semiconductor nanotubes},
   area = {nanotubes}
   doi = {10.1063/1.3130094},
  
}
George B. Abadir, Konrad Walus, Robin Turner & David L. Pulfrey, Biomolecular Sensing Using Carbon Nanotubes: A Simulation Study, International Journal of High Speed Electronics and Systems, Vol. 18(4), pp. 879--887 (2008)
Abstract    BibTeX    DOI: 10.1142/S0129156408005849   
Abstract: A simulation study using molecular dynamics and the density-functional-theory/non-equilibrium-Green's-function approach has been carried out to investigate the potential of carbon nanotubes (CNT) as molecular-scale biosensors. Single molecules of each of two amino acids (isoleucine and asparagine) were used as the target molecules in two separate simulations. The results show a significant suppression of the local density of states (LDOS) in both cases, with a distinct response for each molecule. This is promising for the prospect of CNT-based single-molecule sensors that might depend on the LDOS, e.g., devices that respond to changes in either conductance or electroluminescence.
BibTeX:
@article{Abadir2008,
   title = {Biomolecular Sensing Using Carbon Nanotubes: A Simulation Study},
   author = {Abadir, George B. and Walus, Konrad and Turner, Robin and Pulfrey, David L},
  
   journal = {International Journal of High Speed Electronics and Systems},
  
  
   volume = {18},
   number = {4},
   pages = {879--887},
   year = {2008},
   keywords = {Carbon nanotubes,ab initio simulations,area:nanotubes,biosensors,molecular dynamics},
   area = {nanotubes}
   doi = {10.1142/S0129156408005849},
  
}
George B. Abadir, Konrad Walus, Robin Turner & David L. Pulfrey, Effect of Single-Biomolecule Adsorption on the Electrical Properties of Short Carbon Nanotubes, pp. 230--232 (2008)
Abstract    BibTeX    DOI: 10.1109/NANO.2008.75   
Abstract: Further progress in examining the suitability of carbon nanotubes for single-biomolecule sensing has been made via ab initio simulations using the density functional theory/non- equilibrium green's function approach. Adsorption of different amino acids on short carbon nanotubes is predicted to cause different changes in local densities of states, transmission coefficient, and current.
BibTeX:
@inproceedings{Abadir2008a,
   title = {Effect of Single-Biomolecule Adsorption on the Electrical Properties of Short Carbon Nanotubes},
   author = {Abadir, George B. and Walus, Konrad and Turner, Robin and Pulfrey, David L},
   booktitle = {8th IEEE Conference on Nanotechnology},
  
  
  
  
  
   pages = {230--232},
   year = {2008},
   keywords = {Carbon nanotubes,ab initio simulations,area:nanotubes,biosensors,molecular dynamics},
   area = {nanotubes}
   doi = {10.1109/NANO.2008.75},
  
}
Shuji Abe, Modeling of molecular switches and sensors, CICSJ Bulletin, Vol. 27(5), pp. 124 (2010)
BibTeX    URL: https://www.jstage.jst.go.jp/article/cicsj/27/5/27_5_124/_pdf   
BibTeX:
@article{Abe2010,
   title = {Modeling of molecular switches and sensors},
   author = {Abe, Shuji},
  
   journal = {CICSJ Bulletin},
  
  
   volume = {27},
   number = {5},
   pages = {124},
   year = {2010},
   keywords = {area:molecular electronics,molecular electronics,sensor},
   area = {molecular electronics}
  
   url = {https://www.jstage.jst.go.jp/article/cicsj/27/5/27_5_124/_pdf},
}
Somobrata Acharya, Bidisa Das, Umamahesh Thupakula, Katsuhiko Ariga, D.D. Sarma, Jacob Israelachvili & Yuval Golan, A Bottom-Up Approach toward Fabrication of Ultrathin PbS Sheets, Nano Lett., Vol. 13(2), pp. 409--415 (2013)
Abstract    BibTeX    DOI: 10.1021/nl303568d   
Abstract: Two-dimensional (2D) sheets are currently in the spotlight of nanotechnology owing to high-performance device fabrication possibilities. Building a free-standing quantum sheet with controlled morphology is challenging when large planar geometry and ultranarrow thickness are simultaneously concerned. Coalescence of nanowires into large single-crystalline sheet is a promising approach leading to large, molecularly thick 2D sheets with controlled planar morphology. Here we report on a bottom-up approach to fabricate high-quality ultrathin 2D single crystalline sheets with well-defined rectangular morphology via collective coalescence of PbS nanowires. The ultrathin sheets are strictly rectangular with 1.8 nm thickness, 200-250 nm width, and 3-20 micrometer length. The sheets show high electrical conductivity at room and cryogenic temperatures upon device fabrication. Density functional theory (DFT) calculations reveal that a single row of delocalized orbitals of a nanowire is gradually converted into several parallel conduction channels upon sheet formation, which enable superior in-plane carrier conduction.
BibTeX:
@article{Acharya2013,
   title = {A Bottom-Up Approach toward Fabrication of Ultrathin PbS Sheets},
   author = {Acharya, Somobrata and Das, Bidisa and Thupakula, Umamahesh and Ariga, Katsuhiko and Sarma, D D and Israelachvili, Jacob and Golan, Yuval},
  
   journal = {Nano Lett.},
  
   publisher = {American Chemical Society},
   volume = {13},
   number = {2},
   pages = {409--415},
   year = {2013},
   keywords = {DFT calculations,Langmuir monolayers,activation energy,area:nanowires,ballistic transport,coalescence,metal-insulator-transition,nanocrystals,nanowires,oriented attachment,room-temperature,superlattices,suspended graphene,transport,ultrathin sheet},
   area = {nanowires}
   doi = {10.1021/nl303568d},
  
}
Manisha Aggarwal, Ashok Kumar & Inderpreet Kaur, Computational Study on the Electronic Properties of Functionalized Graphene Nanoribbon, International Journal for Science and Emerging Technologies with Latest Trends, Vol. 4(1), pp. 7--12 (2012)
Abstract    BibTeX    URL: http://www.ijsett.com/images/Paper(4)7-12.pdf   
Abstract: Graphene, the starting material for all the carbon nanostructures, has attracted the attention of all the researchers worldwide due to its remarkable electronic and transport properties like quantum Hall effect at room temperature, an ambipolar electric field effect along with ballistic conduction of charge carriers, tunable band gap and high elasticity. Graphene is a flat monolayer 2D system of carbon atoms organized into a honeycomb lattice with sp2 hybridization. Graphene is a zero band gap material which is the defining concept for semiconductor materials and essential for controlling the conductivity by electronic means. However bilayer graphene shows band gap of 0.25 eV when a vertical electric field is applied. A large number of methods have been employed to calculate graphene's properties; one of them is theoretical study using density functional theory (DFT) method. Here in this article we are calculating band structure, density of states and transmission spectrum using density functional theory calculations by varying the length and the width of graphene nanoribbon (GNR). Functionalization studies of GNR have also been conducted using ATK-DFT.
BibTeX:
@article{Aggarwal2012,
   title = {Computational Study on the Electronic Properties of Functionalized Graphene Nanoribbon},
   author = {Aggarwal, Manisha and Kumar, Ashok and Kaur, Inderpreet},
  
   journal = {International Journal for Science and Emerging Technologies with Latest Trends},
  
  
   volume = {4},
   number = {1},
   pages = {7--12},
   year = {2012},
   keywords = {area:graphene,band structure,density functional theory,functionalization,graphene},
   area = {graphene}
  
   url = {http://www.ijsett.com/images/Paper(4)7-12.pdf},
}
Towfiq Ahmed, Jason T. Haraldsen, John J. Rehr, Massimiliano Di Ventra, Ivan Schuller & Alexander V. Balatsky, Correlation dynamics and enhanced signals for the identification of serial biomolecules and DNA bases, Nanotechnology, Vol. 25(12), pp. 125705 (2014)
Abstract    BibTeX    DOI: 10.1088/0957-4484/25/12/125705   
Abstract: Nanopore-based sequencing has demonstrated a significant potential for the development of fast, accurate, and cost-efficient fingerprinting techniques for next generation molecular detection and sequencing. We propose a specific multilayered graphene-based nanopore device architecture for the recognition of single biomolecules. Molecular detection and analysis can be accomplished through the detection of transverse currents as the molecule or DNA base translocates through the nanopore. To increase the overall signal-to-noise ratio and the accuracy, we implement a new 'multi-point cross-correlation' technique for identification of DNA bases or other molecules on the single molecular level. We demonstrate that the cross-correlations between each nanopore will greatly enhance the transverse current signal for each molecule. We implement first-principles transport calculations for DNA bases surveyed across a multilayered graphene nanopore system to illustrate the advantages of the proposed geometry. A time-series analysis of the cross-correlation functions illustrates the potential of this method for enhancing the signal-to-noise ratio. This work constitutes a significant step forward in facilitating fingerprinting of single biomolecules using solid state technology.
BibTeX:
@article{Ahmed2014,
   title = {Correlation dynamics and enhanced signals for the identification of serial biomolecules and DNA bases},
   author = {Ahmed, Towfiq and Haraldsen, Jason T. and Rehr, John J and Ventra, Massimiliano Di and Schuller, Ivan and Balatsky, Alexander V.},
  
   journal = {Nanotechnology},
  
  
   volume = {25},
   number = {12},
   pages = {125705},
   year = {2014},
   keywords = {area:graphene,graphene,nanoribbon},
   area = {graphene}
   doi = {10.1088/0957-4484/25/12/125705},
  
}
Towfiq Ahmed, Jason T. Haraldsen, Jian-Xin Zhu & Alexander V. Balatsky, Next-Generation Epigenetic Detection Technique: Identifying Methylated Cytosine Using Graphene Nanopore, The Journal of Physical Chemistry Letters, Vol. 5(15), pp. 2601--2607 (2014)
Abstract    BibTeX    DOI: 10.1021/jz501085e   
Abstract: DNA methylation plays a pivotal role in the genetic evolution of both embryonic and adult cells. For adult somatic cells, the location and dynamics of methylation have been very precisely pinned down with the 5-cytosine markers on cytosine-phosphate-guanine (CpG) units. Unusual methylation on CpG islands is identified as one of the prime causes for silencing the tumor suppressant genes. Early detection of methylation changes can diagnose the potentially harmful oncogenic evolution of cells and provide promising guideline for cancer prevention. With this motivation, we propose a cytosine methylation detection technique. Our hypothesis is that electronic signatures of DNA acquired as a molecule translocates through a nanopore would be significantly different for methylated and nonmethylated bases. This difference in electronic fingerprints would allow for reliable real-time differentiation of methylated DNA. We calculate transport currents through a punctured graphene membrane while the cytosine and methylated cytosine translocate through the nanopore. We also calculate the transport properties for uracil and cyanocytosine for comparison. Our calculations of transmission, current, and tunneling conductance show distinct signatures in their spectrum for each molecular type. Thus, in this work, we provide a theoretical analysis that points to a viability of our hypothesis.
BibTeX:
@article{Ahmed2014a,
   title = {Next-Generation Epigenetic Detection Technique: Identifying Methylated Cytosine Using Graphene Nanopore},
   author = {Ahmed, Towfiq and Haraldsen, Jason T. and Zhu, Jian-Xin and Balatsky, Alexander V.},
  
   journal = {The Journal of Physical Chemistry Letters},
  
  
   volume = {5},
   number = {15},
   pages = {2601--2607},
   year = {2014},
   keywords = {application,area:graphene,cytosine,graphene},
   area = {graphene}
   doi = {10.1021/jz501085e},
  
}
Brahim Akdim, S.N. Kim, R.R. Naik, B. Maruyama, M.J. Pender & Ruth Pachter, Understanding effects of molecular adsorption at a single-wall boron nitride nanotube interface from density functional theory calculations, Nanotechnology, Vol. 20(35), pp. 355705 (8pp) (2009)
Abstract    BibTeX    DOI: 10.1088/0957-4484/20/35/355705   
Abstract: In this paper, we explored computationally the feasibility of modulating the bandgap in a single-wall BN nanotube (BNNT) upon noncovalent adsorption of organic molecules, combined with the application of a transverse electric field. Effects of analytes' physisorption on the surface of BNNTs regarding structural and electronic properties were delineated. Relatively large binding energies were calculated, however, with minimal perturbation of the structural framework. Electronic structure calculations indicated that the bandgap of BNNTs can be modified by weak adsorption due to the presence of adsorbate states in the gap of the host system. Furthermore, we have shown that the application of a transverse electric field can tune the bandgap by shifting adsorbate states, consistent with calculated current-voltage characteristics.
BibTeX:
@article{Akdim2009,
   title = {Understanding effects of molecular adsorption at a single-wall boron nitride nanotube interface from density functional theory calculations},
   author = {Akdim, Brahim and Kim, S N and Naik, R R and Maruyama, B and Pender, M J and Pachter, Ruth},
  
   journal = {Nanotechnology},
  
  
   volume = {20},
   number = {35},
   pages = {355705 (8pp)},
   year = {2009},
   keywords = {area:nanotubes,boron,dopant,nanotube,nitrogen},
   area = {nanotubes}
   doi = {10.1088/0957-4484/20/35/355705},
  
}
Brahim Akdim & Ruth Pachter, Switching behavior in pi-conjugated molecules bridging nonmetallic electrodes: A density functional theory study, Journal of Physical Chemistry C, Vol. 112(9), pp. 3170--3174 (2008)
Abstract    BibTeX    DOI: 10.1021/jp7110132   
Abstract: We report a first-principles study to investigate the switching behavior in a nitro-oligo(phenylene ethylene) molecule bridged between a silicon slab and a single wall carbon nanotube (SWCNT) mat. Our results suggest that the switching in the device may be driven by conformational changes in the molecule upon the application of an electric field. In addition, we find that the nature of the contact at the interface of the SWCNT mat plays an important role in the switching.
BibTeX:
@article{Akdim2008,
   title = {Switching behavior in pi-conjugated molecules bridging nonmetallic electrodes: A density functional theory study},
   author = {Akdim, Brahim and Pachter, Ruth},
  
   journal = {Journal of Physical Chemistry C},
  
   publisher = {AMER CHEMICAL SOC},
   volume = {112},
   number = {9},
   pages = {3170--3174},
   year = {2008},
   keywords = {area:molecular electronics,area:nanotubes,molecular electronics,nanotubes,switch},
   area = {molecular electronics,nanotubes}
   doi = {10.1021/jp7110132},
  
}
Brahim Akdim, Ruth Pachter, Steve S. Kim, Rajesh R. Naik, Tiffany R. Walsh, Steven Trohalaki, Gongyi Hong, Zhifeng Kuang & Barry L. Farmer, Electronic Properties of a Graphene Device with Peptide Adsorption: Insight from Simulation, ACS Appl. Mater. Interfaces, Vol. 5(15), pp. 7470--7477 (2013)
Abstract    BibTeX    DOI: 10.1021/am401731c   
Abstract: In this work, to explain doping behavior of single-layer graphene upon HSSYWYAFNNKT (P1) and HSSAAAAFNNKT (P1-3A) adsorption in field-effect transistors (GFETs), we applied a combined computational approach, whereby peptide adsorption was modeled by molecular dynamics simulations, and the lowest energy configuration was confirmed by density functional theory calculations. On the basis of the resulting structures of the hybrid materials, electronic structure and transport calculations were investigated. We demonstrate that pi-pi stacking of the aromatic residues and proximate peptide backbone to the graphene surface in P1 have a role in the p-doping. These results are consistent with our experimental observation of the GFET's p-doping even after a 24-h annealing procedure. Upon substitution of three of the aromatic residues to Ala in (P1-3A), a considerable decrease from p-doping is observed experimentally, demonstrating n-doping as compared to the nonadsorbed device, yet not explained based on the atomistic MD simulation structures. To gain a qualitative understanding of P1-3A's adsorption over a longer simulation time, which may differ from aromatic amino acid residues' swift anchoring on the surface, we analyzed equilibrated coarse-grain simulations performed for 500 ns. Desorption of the Ala residues from the surface was shown computationally, which could in turn affect charge transfer, yet a full explanation of the mechanism of n-doping will require elucidation of differences between various aromatic residues as dependent on peptide composition, and inclusion of effects of the substrate and environment, to be considered in future work.
BibTeX:
@article{Akdim2013,
   title = {Electronic Properties of a Graphene Device with Peptide Adsorption: Insight from Simulation},
   author = {Akdim, Brahim and Pachter, Ruth and Kim, Steve S and Naik, Rajesh R and Walsh, Tiffany R and Trohalaki, Steven and Hong, Gongyi and Kuang, Zhifeng and Farmer, Barry L},
  
   journal = {ACS Appl. Mater. Interfaces},
  
   publisher = {American Chemical Society},
   volume = {5},
   number = {15},
   pages = {7470--7477},
   year = {2013},
   keywords = {accurate,area:graphene,binding,distributed multipole analysis,doping,field,graphene,layer graphene,molecular adsorption,molecular dynamics,molecular-dynamics,parameters,peptides,proteins,scattering,transistors},
   area = {graphene}
   doi = {10.1021/am401731c},
  
}
Brahim Akdim, Ruth Pachter & Richard A. Vaia, Tunability in electron transport of molybdenum chalcogenide nanowires by theoretical prediction, Chemical Physics Letters, Vol. 615 pp. 99--104 (2014)
Abstract    BibTeX    DOI: 10.1016/j.cplett.2014.10.011   
Abstract: Transition metal chalcogenide nanowires could comprise an alternative for nanoelectronics application, yet this class of materials is not well-characterized. Here we predict tunability in I-V characteristics of MoX (X = S, Se) nanowires, dependent on chalcogen atom, Li doping, type of electrode, and morphology. We show an intrinsic negative differential resistance (NDR)-like behavior for Mo6S6 nanowires, explained by bands mismatch in the electronic structure calculated by density functional theory (DFT) within the non-equilibrium Green's function formalism. The NDR-like behavior is suppressed upon Li intercalation or for gold leads. The electron transport results are based on optimized configurations using a non-empirical London dispersion-corrected DFT functional.
BibTeX:
@article{Akdim2014,
   title = {Tunability in electron transport of molybdenum chalcogenide nanowires by theoretical prediction},
   author = {Akdim, Brahim and Pachter, Ruth and Vaia, Richard A},
  
   journal = {Chemical Physics Letters},
  
  
   volume = {615},
  
   pages = {99--104},
   year = {2014},
   keywords = {area:2dmat,area:nanowires,area:tmd,dispersion,nanowires,negative differential resistance,transition metal chalcogenide,van der Waals},
   area = {2dmat,nanowires,tmd}
   doi = {10.1016/j.cplett.2014.10.011},
  
}
Zakaria Y. Al Balushi, Ke Wang, Ram Krishna Ghosh, Rafael A. Vilá, Sarah M. Eichfeld, Joshua D. Caldwell, Xiaoye Qin, Yu-Chuan Lin, Paul A. DeSario, Greg Stone, Shruti Subramanian, Dennis F. Paul, Robert M. Wallace, Suman Datta, Joan M. Redwing & Joshua A. Robinson, Two-dimensional gallium nitride realized via graphene encapsulation, Nature Materials, Vol. 15(11), pp. 1166--1171 (2016)
Abstract    BibTeX    DOI: 10.1038/nmat4742   
Abstract: The spectrum of two-dimensional (2D) and layered materials ‘beyond graphene' offers a remarkable platform to study new phenomena in condensed matter physics. Among these materials, layered hexagonal boron nitride (hBN), with its wide bandgap energy (˜5.0–6.0 eV), has clearly established that 2D nitrides are key to advancing 2D devices1. A gap, however, remains between the theoretical prediction of 2D nitrides ‘beyond hBN'2, 3 and experimental realization of such structures. Here we demonstrate the synthesis of 2D gallium nitride (GaN) via a migration-enhanced encapsulated growth (MEEG) technique utilizing epitaxial graphene. We theoretically predict and experimentally validate that the atomic structure of 2D GaN grown via MEEG is notably different from reported theory2, 3, 4. Moreover, we establish that graphene plays a critical role in stabilizing the direct-bandgap (nearly 5.0 eV), 2D buckled structure. Our results provide a foundation for discovery and stabilization of 2D nitrides that are difficult to prepare via traditional synthesis.
BibTeX:
@article{AlBalushi2016,
   title = {Two-dimensional gallium nitride realized via graphene encapsulation},
   author = {Al Balushi, Zakaria Y. and Wang, Ke and Ghosh, Ram Krishna and Vilá, Rafael A. and Eichfeld, Sarah M. and Caldwell, Joshua D. and Qin, Xiaoye and Lin, Yu-Chuan and DeSario, Paul A. and Stone, Greg and Subramanian, Shruti and Paul, Dennis F. and Wallace, Robert M. and Datta, Suman and Redwing, Joan M. and Robinson, Joshua A.},
  
   journal = {Nature Materials},
  
  
   volume = {15},
   number = {11},
   pages = {1166--1171},
   year = {2016},
   keywords = {Electronic properties and materials,Two-dimensional materials,area:2dmat,area:graphene},
   area = {2dmat,graphene}
   doi = {10.1038/nmat4742},
  
}
Y. Al & H.L. Zhang, Construction and Conductance Measurement of Single Molecule Junctions, Acta Physico-chimica Sinica, Vol. 28(10), pp. 2237--2248 (2012)
Abstract    BibTeX    DOI: 10.3866/PKU.WHXB201209102   
Abstract: Molecular electronics has become an important research field in the past decade, and molecular devices can be used as molecular wires, switches, rectifiers, and transistors etc. Construction of metal/molecule/metal (MMM) junctions is the most effective method for investigating the charge transport properties of molecular devices. However, the measurement of individual molecule junctions at the nanoscale is still very challenging because of many technical difficulties. This paper reviews the recent progress and the challenges in the measurement of single molecule conductance, and summarizes investigation of the charge transport mechanism.
BibTeX:
@article{Al2012,
   title = {Construction and Conductance Measurement of Single Molecule Junctions},
   author = {Al, Y and Zhang, H L},
  
   journal = {Acta Physico-chimica Sinica},
  
   publisher = {Peking Univ Press},
   volume = {28},
   number = {10},
   pages = {2237--2248},
   year = {2012},
   keywords = {area:molecular electronics,atomic-force microscopy,break junctions,charge-transport,electrical conductance,electronic devices,metal nanowires,quantum transport,scanning probe,spin,walled carbon nanotubes},
   area = {molecular electronics}
   doi = {10.3866/PKU.WHXB201209102},
  
}
Feras Al-Dirini, Faruque M. Hossain, Mahmood A. Mohammed, Md Sharafat Hossain, Ampalavanapillai Nirmalathas & Efstratios Skafidas, Monolayer MoS2 self-switching diodes, Journal of Applied Physics, Vol. 119(4), pp. 044506 (2016)
Abstract    BibTeX    DOI: 10.1063/1.4940707   
Abstract: This paper presents a new molybdenum disulphide (MoS2) nanodevice that acts as a two-terminal field-effect rectifier. The device is an atomically-thin two-dimensional self-switching diode (SSD) that can be realized within a single MoS2monolayer with very minimal process steps. Quantum simulation results are presented confirming the device's operation as a diode and showing strong non-linear I-V characteristics. Interestingly, the device shows p-type behavior, in which conduction is dominated by holes as majority charge carriers and the flow of reverse current is enhanced, while the flow of forward current is suppressed, in contrast to monolayergraphene SSDs, which behave as n-type devices. The presence of a large bandgap in monolayer MoS2 results in strong control over the channel, showing complete channel pinch-off in forward conduction, which was confirmed with transmission pathways plots. The device exhibited large leakage tunnelling current through the insulating trenches, which may have been due to the lack of passivation; nevertheless, reverse current remained to be 6 times higher than forward current, showing strong rectification. The effect of p-type substitutional channel doping of sulphur with phosphorus was investigated and showed that it greatly enhances the performance of the device, increasing the reverse-to-forward current rectification ratio more than an order of magnitude, up to a value of 70.
BibTeX:
@article{Al-Dirini2016b,
   title = {Monolayer MoS2 self-switching diodes},
   author = {Al-Dirini, Feras and Hossain, Faruque M. and Mohammed, Mahmood A. and Hossain, Md Sharafat and Nirmalathas, Ampalavanapillai and Skafidas, Efstratios},
  
   journal = {Journal of Applied Physics},
  
  
   volume = {119},
   number = {4},
   pages = {044506},
   year = {2016},
   keywords = {Band gap,Diodes,Doping,Field-effect transistors,Graphene,Nano-structures,Rectification,Tunnel-effect diodes,Tunneling,area:2dmat,area:tmd},
   area = {2dmat,tmd}
   doi = {10.1063/1.4940707},
  
}
Feras Al-Dirini, Faruque M. Hossain, Mahmood A. Mohammed, Ampalavanapillai Nirmalathas & Efstratios Skafidas, Highly Effective Conductance Modulation in Planar Silicene Field Effect Devices Due to Buckling, Scientific Reports, Vol. 5 pp. 14815 (2015)
Abstract    BibTeX    DOI: 10.1038/srep14815   
Abstract: Silicene is an exciting two-dimensional material that shares many of graphene's electronic properties, but differs in its structural buckling. This buckling allows opening a bandgap in silicene through the application of a perpendicular electric field. Here we show that this buckling also enables highly effective modulation of silicene's conductance by means of an in-plane electric field applied through silicene side gates, which can be realized concurrently within the same silicene monolayer. We illustrate this by using silicene to implement Self-Switching Diodes (SSDs), which are two-dimensional field effect nanorectifiers realized within a single silicene monolayer. Our quantum simulation results show that the atomically-thin silicene SSDs, with sub-10 nm dimensions, achieve a current rectification ratio that exceeds 200, without the need for doping, representing a 30 fold enhancement over graphene SSDs. We attribute this enhancement to a bandgap opening due to the in-plane electric field, as a consequence of silicene's buckling. Our results suggest that silicene is a promising material for the realization of planar field effect devices.
BibTeX:
@article{Al-Dirini2015,
   title = {Highly Effective Conductance Modulation in Planar Silicene Field Effect Devices Due to Buckling},
   author = {Al-Dirini, Feras and Hossain, Faruque M and Mohammed, Mahmood A and Nirmalathas, Ampalavanapillai and Skafidas, Efstratios},
  
   journal = {Scientific Reports},
  
   publisher = {Nature Publishing Group},
   volume = {5},
  
   pages = {14815},
   year = {2015},
   keywords = {Electrical and electronic engineering,Electronic and spintronic devices,Electronic devices,area:2dmat,silicene,transmission pathways},
   area = {2dmat}
   doi = {10.1038/srep14815},
  
}
Feras Al-Dirini, Faruque M. Hossain, Ampalavanapillai Nirmalathas & Efstratios Skafidas, All-Graphene Planar Double Barrier Resonant Tunneling Diodes, Journal of the Electron Devices Society, Vol. 2(5), pp. 118--122 (2014)
Abstract    BibTeX    DOI: 10.1109/jeds.2014.2327375   
Abstract: In this work, we propose an atomically-thin all-graphene planar double barrier resonant tunneling diode that can be realized within a single graphene nanoribbon. The proposed device does not require any doping or external gating and can be fabricated using minimal process steps. The planar architecture of the device allows a simple in-plane connection of multiple devices in parallel without any extra processing steps during fabrication, enhancing the current driving capabilities of the device. Quantum mechanical simulation results, based on non-equilibrium Green's function formalism and the extended Huckel method, show promising device performance with a high reverse-to-forward current rectification ratio exceeding 50 000, and confirm the presence of negative differential resistance within the device's current-voltage characteristics.
BibTeX:
@article{Al-Dirini2014a,
   title = {All-Graphene Planar Double Barrier Resonant Tunneling Diodes},
   author = {Al-Dirini, Feras and Hossain, Faruque M and Nirmalathas, Ampalavanapillai and Skafidas, Efstratios},
  
   journal = {Journal of the Electron Devices Society},
  
   publisher = {Institute of Electrical & Electronics Engineers (IEEE)},
   volume = {2},
   number = {5},
   pages = {118--122},
   year = {2014},
   keywords = {Double barrierer,Extended-Huckel (EHT),NDR,NEGF,area:graphene,graphene,planar diode,rectifier,resonant tunneling},
   area = {graphene}
   doi = {10.1109/jeds.2014.2327375},
  
}
Feras Al-Dirini, Faruque M. Hossain, Ampalavanapillai Nirmalathas & Efstratios Skafidas, All-Graphene Planar Self-Switching MISFEDs, Metal-Insulator-Semiconductor Field-Effect Diodes, Scientific Reports, Vol. 4 pp. 3983 (2014)
Abstract    BibTeX    DOI: 10.1038/srep03983   
Abstract: Graphene normally behaves as a semimetal because it lacks a bandgap, but when it is patterned into nanoribbons a bandgap can be introduced. By varying the width of these nanoribbons this band gap can be tuned from semiconducting to metallic. This property allows metallic and semiconducting regions within a single Graphene monolayer, which can be used in realising two-dimensional (2D) planar Metal-Insulator-Semiconductor field effect devices. Based on this concept, we present a new class of nano-scale planar devices named Graphene Self-Switching MISFEDs (Metal-Insulator-Semiconductor Field-Effect Diodes), in which Graphene is used as the metal and the semiconductor concurrently. The presented devices exhibit excellent current-voltage characteristics while occupying an ultra-small area with sub-10 nm dimensions and an ultimate thinness of a single atom. Quantum mechanical simulation results, based on the Extended Huckel method and Nonequilibrium Green's Function Formalism, show that a Graphene Self-Switching MISFED with a channel as short as 5 nm can achieve forward-to-reverse current rectification ratios exceeding 5000.
BibTeX:
@article{Al-Dirini2014b,
   title = {All-Graphene Planar Self-Switching MISFEDs, Metal-Insulator-Semiconductor Field-Effect Diodes},
   author = {Al-Dirini, Feras and Hossain, Faruque M and Nirmalathas, Ampalavanapillai and Skafidas, Efstratios},
  
   journal = {Scientific Reports},
  
   publisher = {Nature Publishing Group},
   volume = {4},
  
   pages = {3983},
   year = {2014},
   keywords = {application,area:graphene,electrical and electronic engineering,electronic and spintronic devices,electronic properties and devices,graphene,nanoribbon},
   area = {graphene}
   doi = {10.1038/srep03983},
  
}
Feras Al-Dirini, Faruque M. Hossain, Ampalavanapillai Nirmalathas & Efstratios Skafidas, Asymmetrically-gated graphene self-switching diodes as negative differential resistance devices, Nanoscale, Vol. 6(13), pp. 7628--7634 (2014)
Abstract    BibTeX    DOI: 10.1039/C4NR00112E   
Abstract: We present an asymmetrically-gated Graphene Self-Switching Diode (G-SSD) as a new negative differential resistance (NDR) device, and study its transport properties using nonequilibrium Green's function (NEGF) formalism and the Extended Huckel (EH) method. The device exhibits a new NDR mechanism, in which a very small quantum tunnelling current is used to control a much-larger channel conduction current, resulting in a very pronounced NDR effect. This NDR effect occurs at low bias voltages, below 1 V, and results in a very high current peak in the $$ range and a high peak-to-valley current ratio (PVCR) of 40. The device has an atomically-thin structure with sub-10 nm dimensions, and does not require any doping or external gating. These results suggest that the device has promising potential in applications such as high frequency oscillators, memory devices, and fast switches.
BibTeX:
@article{Al-Dirini2014,
   title = {Asymmetrically-gated graphene self-switching diodes as negative differential resistance devices},
   author = {Al-Dirini, Feras and Hossain, Faruque M and Nirmalathas, Ampalavanapillai and Skafidas, Efstratios},
  
   journal = {Nanoscale},
  
   publisher = {The Royal Society of Chemistry},
   volume = {6},
   number = {13},
   pages = {7628--7634},
   year = {2014},
   keywords = {Extended-Huckel (EHT),NEGF,area:graphene,differential resistance,diode,graphene},
   area = {graphene}
   doi = {10.1039/C4NR00112E},
  
}
Feras Al-Dirini, Mahmood A. Mohammed, Md Sharafat Hossain, Faruque M. Hossain, Ampalavanapillai Nirmalathas & Stan Skafidas, Tuneable graphene nanopores for single biomolecule detection, Nanoscale, Vol. 8 pp. 10066--10077 (2016)
Abstract    BibTeX    DOI: 10.1039/C5NR05274B   
Abstract: Solid-state nanopores are promising candidates for next generation DNA and protein sequencing. However, once fabricated, such devices lack tuneability, which greatly restricts their biosensing capabilities. Here we propose a new class of solid-state graphene-based nanopore devices that exhibit a unique capability of self-tuneability, which is used to control their conductance, tuning it to levels comparable to the changes caused by the translocation of a single biomolecule, and hence, enabling high detection sensitivities. Our presented quantum simulation results suggest that the smallest amino acid, glycine, when present in water and in an aqueous saline solution can be detected with high sensitivity, up to a 90% change in conductance. Our results also suggest that passivating the device with nitrogen, making it an n-type device, greatly enhances its sensitivity, and makes it highly sensitive to not only the translocation of a single biomolecule, but more interestingly to intramolecular electrostatics within the biomolecule. Sensitive detection of the carboxyl group within the glycine molecule, which carries a charge equivalent to a single electron, is achieved with a conductance change that reaches as high as 99% when present in an aqueous saline solution. The presented findings suggest that tuneable graphene nanopores, with their capability of probing intramolecular electrostatics, could pave the way towards a new generation of single biomolecule detection devices.
BibTeX:
@article{Al-Dirini2016,
   title = {Tuneable graphene nanopores for single biomolecule detection},
   author = {Al-Dirini, Feras and Mohammed, Mahmood A and Hossain, Md Sharafat and Hossain, Faruque M and Nirmalathas, Ampalavanapillai and Skafidas, Stan},
  
   journal = {Nanoscale},
  
  
   volume = {8},
  
   pages = {10066--10077},
   year = {2016},
   keywords = {area:graphene,transmission pathways},
   area = {graphene}
   doi = {10.1039/C5NR05274B},
  
}
Feras Alzubi & Ronald Cosby, Calculating Young's modulus for a carbon nanotube, (2008)
Abstract    BibTeX    URL: http://adsabs.harvard.edu/abs/2008APS..OSF.C6003A   
Abstract: Young's modulus for an armchair single-wall carbon nanotube was calculated using an atomistic approach and density functional theory (DFT). Atomic forces and total energies for strained carbon nanotube segments were computed using Atomistix's Virtual NanoLab (VNL) and ToolKit (ATK) software. For a maximum strain of one percent, elastic moduli were calculated using both force-strain and energy-strain data. The average values found for Young's modulus were in the range 1.2 to 3.9 TPa depending on the cross-sectional area taken for the carbon nanotube, consideration of Poisson's ratio, and the calculation method used. Three possible choices of cross-sectional area for the carbon nanotube are discussed and parameter and convergence tests for the DFT computations are described.
BibTeX:
@inproceedings{Alzubi2008,
   title = {Calculating Young's modulus for a carbon nanotube},
   author = {Alzubi, Feras and Cosby, Ronald},
   booktitle = {2008 Joint Meeting of the APS Ohio-Region Section, the AAPT Southern Ohio Section, and the ACS Dayton-Section},
  
  
  
  
  
  
   year = {2008},
   keywords = {Young's modulus,area:nanotubes,nanotubes},
   area = {nanotubes}
  
   url = {http://adsabs.harvard.edu/abs/2008APS..OSF.C6003A},
}
David B. Amabilino, Steven De Feyter, Roberto Lazzaroni, Elba Gomar-Nadal, Jaume Veciana, Concepcio Rovira, Mohamed M. Abdel-Mottaleb, Wael Mamdouh, Patrizia Iavicoli, Krystallia Psychogyiopoulou, Mathieu Linares, Andrea Minoia, Hong Xu & Josep Puigmarti-Luis, Monolayer self-assembly at liquid-solid interfaces: chirality and electronic properties of molecules at surfaces, Journal of Physics: Condensed Matter, Vol. 20 pp. 184003 (2008)
Abstract    BibTeX    DOI: 10.1088/0953-8984/20/18/184003   
Abstract: The spontaneous formation of supramolecular assemblies at the boundary between solids and liquids is a process which encompasses a variety of systems with diverse characteristics: chemisorbed systems in which very strong and weakly reversible bonds govern the assembly and physisorbed aggregates which are dynamic thanks to the weaker interactions between adsorbate and surface. Here we review the interest and advances in the study of chiral systemsat the liquid-solid interface, and also the application of this configuration for the study of systems of interest in molecular electronics, self-assembled from the bottom up.
BibTeX:
@article{Amabilino2008,
   title = {Monolayer self-assembly at liquid-solid interfaces: chirality and electronic properties of molecules at surfaces},
   author = {Amabilino, David B and Feyter, Steven De and Lazzaroni, Roberto and Gomar-Nadal, Elba and Veciana, Jaume and Rovira, Concepcio and Abdel-Mottaleb, Mohamed M and Mamdouh, Wael and Iavicoli, Patrizia and Psychogyiopoulou, Krystallia and Linares, Mathieu and Minoia, Andrea and Xu, Hong and Puigmarti-Luis, Josep},
  
   journal = {Journal of Physics: Condensed Matter},
  
  
   volume = {20},
  
   pages = {184003},
   year = {2008},
   keywords = {area:interfaces,interfaces,liquid solid interfaces,molecular electronics},
   area = {interfaces}
   doi = {10.1088/0953-8984/20/18/184003},
  
}
Li-Ping An & Nian-hua Liu, The spin-dependent transport properties of zigzag graphene nanoribbon edge-defect junction, New Carbon Materials, Vol. 27(3), pp. 181--187 (2012)
Abstract    BibTeX    DOI: 10.1016/S1872-5805(12)60012-2   
Abstract: First-principles calculation was performed to investigate the transport properties of edge-defect junctions of graphene with H-terminated or bare edges, which were generated by removing edge carbon atoms from a perfect ribbon. The edge defect changes the electronic transport behavior of a zigzag graphene nanoribbon from spin-degenerated for a perfect ribbon to highly spin-polarized for edge-defective ones at the Fermi level. The electronic local density of states isosurface calculations could help understand the transport results. These junctions could generate spin-polarized currents. Especially, the bare edge-defect junction has a high spin filter efficiency regardless of the external bias. This behavior suggests a possible use of the edge-defective graphene in a spin filter system.
BibTeX:
@article{An2012b,
   title = {The spin-dependent transport properties of zigzag graphene nanoribbon edge-defect junction},
   author = {An, Li-Ping and Liu, Nian-hua},
  
   journal = {New Carbon Materials},
  
  
   volume = {27},
   number = {3},
   pages = {181--187},
   year = {2012},
   keywords = {area:graphene,area:spintronics,edge-defect junction,graphene nanoribbon,spin-dependent transport},
   area = {graphene,spintronics}
   doi = {10.1016/S1872-5805(12)60012-2},
  
}
Rui-Li An, Xue-Feng Wang, P. Vasilopoulos, Yu-Shen Liu, An-Bang Chen, Yao-Jun Dong & Ming-Xing Zhai, Vacancy Effects on Electric and Thermoelectric Properties of Zigzag Silicene Nanoribbons, The Journal of Physical Chemistry C, Vol. 118(37), pp. 21339--21346 (2014)
Abstract    BibTeX    DOI: 10.1021/jp506111a   
Abstract: We study the crystal reconstruction in the presence of monovacancies (MVs), divacancies (DVs), and linear vacancies (LVs) in a zigzag silicene nanoribbon (ZSiNR) with transversal symmetry. Their influence on the electric and thermoelectric properties is assessed by the density functional theory combined with the nonequilibrium Green's functions. In particular, we focus on the spin resolved conductance, magnetoresistance and current-voltage curves. A 5-atom-ring is formed in MVs, a 5-8-5 ring structure in DVs, and a 8-4-8-4 ring structure in LVs. The linear conductance becomes strongly spin-dependent when the transversal symmetry is broken by vacancies, especially if they are located on the ribbon's edges. The giant magnetoresistance can be smeared by asymmetric vacancies. Single spin negative differential resistance may appear in the presence of LVs and asymmetric MVs or DVs. A strong spin Seebeck effect is expected at room temperature in ZSiNRs with LVs.
BibTeX:
@article{An2014,
   title = {Vacancy Effects on Electric and Thermoelectric Properties of Zigzag Silicene Nanoribbons},
   author = {An, Rui-Li and Wang, Xue-Feng and Vasilopoulos, P and Liu, Yu-Shen and Chen, An-Bang and Dong, Yao-Jun and Zhai, Ming-Xing},
  
   journal = {The Journal of Physical Chemistry C},
  
  
   volume = {118},
   number = {37},
   pages = {21339--21346},
   year = {2014},
   keywords = {area:2dmat,area:thermo,nanoribbon,silicene,thermoelectrics,vacancy},
   area = {2dmat,thermo}
   doi = {10.1021/jp506111a},
  
}
Yipeng An, Kedong Wang, Guangrui Jia, Tianxing Wang, Zhaoyong Jiao, Zhaoming Fu, Xingli Chu, Guoliang Xu & Chuanlu Yang, Intrinsic negative differential resistance characteristics in zigzag boron nitride nanoribbons, RSC Advances, Vol. 4(87), pp. 46934--46939 (2014)
Abstract    BibTeX    DOI: 10.1039/C4RA08257E   
Abstract: We investigate the charge transport properties of zigzag boron nitride nanoribbons (ZBNNRs) with various hydrogen passivations by employing density functional theory (DFT) combined with the non-equilibrium Green's function (NEGF) formalism. The calculated results reveal that the ZBNNR-based devices exhibit negative differential resistance (NDR) characteristics except those models whose both edges are passivated, due to the mechanism in which the overlap of bands near the Fermi level between the left and right electrodes gets smaller or disappears under a high bias. The NDR characteristics of the perfect ZBNNRs with one or two bare edges are weakly dependent on their widths. This is one intrinsic NDR characteristic of the ZBNNR-based devices, including some defective structures. The intuitive electronic current channels are plotted and analyzed to better understand the charge transport mechanisms. Our results suggest that the ZBNNR-based structures could be favorable candidates for preparing nanoscale NDR devices.
BibTeX:
@article{An2014a,
   title = {Intrinsic negative differential resistance characteristics in zigzag boron nitride nanoribbons},
   author = {An, Yipeng and Wang, Kedong and Jia, Guangrui and Wang, Tianxing and Jiao, Zhaoyong and Fu, Zhaoming and Chu, Xingli and Xu, Guoliang and Yang, Chuanlu},
  
   journal = {RSC Advances},
  
   publisher = {The Royal Society of Chemistry},
   volume = {4},
   number = {87},
   pages = {46934--46939},
   year = {2014},
   keywords = {area:2dmat,boron nitride BN,nanoribbon,negative differential resistance},
   area = {2dmat}
   doi = {10.1039/C4RA08257E},
  
}
Yipeng An, Kedong Wang, Zhongqin Yang, Zhiyong Liu, Guangrui Jia, Zhaoyong Jiao, Tianxing Wang & Guoliang Xu, Negative differential resistance and rectification effects in step-like graphene nanoribbons, Organic Electronics, Vol. 17 pp. 262--269 (2014)
Abstract    BibTeX    DOI: 10.1016/j.orgel.2014.12.013   
Abstract: Step-like zigzag graphene nanoribbons (ZGNRs) with different step widths are designed, and their electronic transport properties are investigated by using the non-equilibrium Green's function method combined with the density functional theory. The results reveal that one with a small step structure can exhibit better conductive capability and interesting negative differential resistance (NDR) behavior under negative applied biases. More importantly, with the increase of step width, these step-like ZGNR nanojunctions present valuable rectification effects, and show a rule that the rectification ratio increases with increasing the step width. It is also shown that the rectification effect can be further inversed and enhanced through introducing a defect around the step. Transmission spectra, densities of states, energy barriers, transmission eigenstates, and transmission pathways are analyzed subsequently to understand the electronic transport properties of these step-like ZGNR devices, which can be used in developing nanoscale NDR devices and rectifiers.
BibTeX:
@article{An2014b,
   title = {Negative differential resistance and rectification effects in step-like graphene nanoribbons},
   author = {An, Yipeng and Wang, Kedong and Yang, Zhongqin and Liu, Zhiyong and Jia, Guangrui and Jiao, Zhaoyong and Wang, Tianxing and Xu, Guoliang},
  
   journal = {Organic Electronics},
  
  
   volume = {17},
  
   pages = {262--269},
   year = {2014},
   keywords = {Charge transport,First-principles calculation,Graphene nanoribbons,Non-equilibrium Green's function,area:graphene},
   area = {graphene}
   doi = {10.1016/j.orgel.2014.12.013},
  
}
Yipeng An, Tianxing Wang, Zhaoming Fu, Xingli Chu & Guoliang Xu, The electronic transport properties of graphene-like beryllium sulfide nanoribbons, Physics Letters A, Vol. 379(32-33), pp. 1837--1841 (2015)
Abstract    BibTeX    DOI: 10.1016/j.physleta.2015.05.013   
Abstract: The electronic transport properties of zigzag beryllium sulfide nanoribbons (ZBeSNRs) are investigated by first-principles calculations. The results indicate that the electrons flow mainly through the two edges of ZBeSNRs. The electron transmission pathways are analyzed in detail. The ZBeSNRs show the remarkable negative differential resistance (NDR) properties, which are independent of the nanoribbon width due to their very similar band structures. The NDR behavior can be maintained by introducing a Be or S atom vacancy defect. The H-passivated ZBeSNR presents the interesting current-limited effect. The ZBeSNRs could be the promising candidates for the future nano devices, such as NDR devices.
BibTeX:
@article{An2015,
   title = {The electronic transport properties of graphene-like beryllium sulfide nanoribbons},
   author = {An, Yipeng and Wang, Tianxing and Fu, Zhaoming and Chu, Xingli and Xu, Guoliang},
  
   journal = {Physics Letters A},
  
  
   volume = {379},
   number = {32-33},
   pages = {1837--1841},
   year = {2015},
   keywords = {Charge transport,First-principl,Nano electronics,area:2dmat},
   area = {2dmat}
   doi = {10.1016/j.physleta.2015.05.013},
  
}
Yipeng An, Mengjun Zhang, Lipeng Chen, Congxin Xia, Tianxing Wang, Zhaoming Fu, Zhaoyong Jiao & Guoliang Xu, Spin-dependent electronic transport properties of zigzag silicon carbon nanoribbon, RSC Adv., Vol. 5(129), pp. 107136--107141 (2015)
Abstract    BibTeX    DOI: 10.1039/C5RA24276B   
Abstract: Spin-dependent electronic transport properties of the zigzag silicon carbon nanoribbon (Z-SiCNR) are studied by employing the non-equilibrium Green's function method in the framework of density functional theory. It is found that the Z-SiCNR exhibits a variety of exotic physical properties. While the Z-SiCNR in the metallic FM state presents spin filtering and current-limited effects, it is shown that the abnormal oscillation of spin-polarized currents with spin polarization as high as 100% under a certain bias voltage emerges in the half-metallic AFM state. The results demonstrate that tuning the spin state of the zigzag SiC nanoribbon provides a possible avenue to design next generation spin nanodevices with novel functionalities.
BibTeX:
@article{An2015a,
   title = {Spin-dependent electronic transport properties of zigzag silicon carbon nanoribbon},
   author = {An, Yipeng and Zhang, Mengjun and Chen, Lipeng and Xia, Congxin and Wang, Tianxing and Fu, Zhaoming and Jiao, Zhaoyong and Xu, Guoliang},
  
   journal = {RSC Adv.},
  
   publisher = {Royal Society of Chemistry},
   volume = {5},
   number = {129},
   pages = {107136--107141},
   year = {2015},
   keywords = {CONDUCTANCE,GRAPHENE,area:2dmat,area:spin},
   area = {2dmat,spin}
   doi = {10.1039/C5RA24276B},
  
}
Yipeng An, Mengjun Zhang, Tianxing Wang, Guangtao Wang & Zhaoming Fu, Rectifications in organic single-molecule diodes alkanethiolate-terminated heterocyclics, Vol. 380(7-8), pp. 923--926 (2016)
Abstract    BibTeX    DOI: 10.1016/j.physleta.2015.12.035   
Abstract: Based on the non-equilibrium Green's function formalism combined with the ab initio density functional theory, we investigate the rectifying behaviors of the organic single-molecule S(CH2)11-terminated with a variety of heterocyclics (i.e., BIPY, PHE, PHEPY, and PYR) coupled with two semi-infinite Au electrodes. Our quantum transport calculation results show that the BIPY and PHE nanojunctions show the high-efficiency rectifying effects. While, differently, the current-voltage (I-V) curves of PHEPY and PYR nanojunctions display the insulating and linear characters, respectively. The corresponding electronic transport mechanisms are analyzed in detail. Our calculation results demonstrate that these investigated organic single-molecule nanojunctions have the potential applications in rectifiers and molecular wires.
BibTeX:
@book{An2016,
   title = {Rectifications in organic single-molecule diodes alkanethiolate-terminated heterocyclics},
   author = {An, Yipeng and Zhang, Mengjun and Wang, Tianxing and Wang, Guangtao and Fu, Zhaoming},
   booktitle = {Physics Letters A},
  
  
   publisher = {Elsevier B.V.},
   volume = {380},
   number = {7-8},
   pages = {923--926},
   year = {2016},
   keywords = {Charge transport,First-principles calculation,Molecular device,Nanoscale electronics,Non-equilibrium Green's function,Rectifier,area:molecular electronics},
   area = {molecular electronics}
   doi = {10.1016/j.physleta.2015.12.035},
  
}
Yipeng An, Mengjun Zhang, Dapeng Wu, Zhaoming Fu, Tianxing Wang & Congxin Xia, Electronic transport properties of the first all-boron fullerene B 40 and its metallofullerene Sr@B 40, Phys. Chem. Chem. Phys., Vol. 18(17), pp. 12024--12028 (2016)
Abstract    BibTeX    DOI: 10.1039/C6CP01096B   
Abstract: The newly-discovered B40 is the first experimentally observed all-boron fullerene and has potential applications in molecular devices. Herein, we report the electronic transport properties of B40 and its metallofullerene, Sr@B40, using the first-principles technique. We obtain the conductance of B40 fullerene, which is about 130 μS and can be increased by embedding a strontium metal atom in the cage due to the decreased energy gap. Both the current-voltage (I-V) curves of B40 and Sr@B40 present perfect linear characteristics. Intuitively, it is assumed that the electron currents pass through the B40 fullerene mainly along the surface B-B bonds, while two types of new B-Sr-B bond currents and B→Sr→B hopping currents are presented for Sr@B40 due to Sr acting as a bridge. This study provides valuable information for the potential applications of future borospherene-based molecular devices.
BibTeX:
@article{An2016a,
   title = {Electronic transport properties of the first all-boron fullerene B 40 and its metallofullerene Sr@B 40},
   author = {An, Yipeng and Zhang, Mengjun and Wu, Dapeng and Fu, Zhaoming and Wang, Tianxing and Xia, Congxin},
  
   journal = {Phys. Chem. Chem. Phys.},
  
   publisher = {Royal Society of Chemistry},
   volume = {18},
   number = {17},
   pages = {12024--12028},
   year = {2016},
   keywords = {area:fullerenes,boron compounds,transmission pathways},
   area = {fullerenes}
   doi = {10.1039/C6CP01096B},
  
}
Yi-Peng An, Wei Ji & Zhong-Qin Yang, Z-like Conducting Pathways in Zigzag Graphene Nanoribbons with Edge Protrusions, J. Phys. Chem. C, Vol. 116(9), pp. 5915--5919 (2012)
Abstract    BibTeX    DOI: 10.1021/jp3003646   
Abstract: Electronic transport properties of zigzag graphene nanoribbons (ZGNRs) with one or two triangle protrusions at the edges are studied by using density functional theory combined with nonequilibrium Green's function method. We find the protrusion generally breaks down the edge state along the same edge, which carries the most current in the junction. For the graphene ribbons having even number of zigzag chains, however, the protrusions can increase or decrease significantly the conductance with different relative position of the two protrusions, accompanied by negative differential resistance characteristics. The abnormal increase of the conductance is ascribed to the forming of a new Z-like conducting pathway as well as the ruining of the mirror symmetry of the ribbons. In terms of odd ZGNRs, the introduction of edge protrusions only suppresses current flow and linear I-V curves are achieved. These edge-modified ways make the graphene-based nanomaterials present more abundant electronic transport phenomena and can be useful for the design of future nanoelectronic devices.
BibTeX:
@article{An2012,
   title = {Z-like Conducting Pathways in Zigzag Graphene Nanoribbons with Edge Protrusions},
   author = {An, Yi-Peng and Ji, Wei and Yang, Zhong-Qin},
  
   journal = {J. Phys. Chem. C},
  
   publisher = {American Chemical Society},
   volume = {116},
   number = {9},
   pages = {5915--5919},
   year = {2012},
   keywords = {NDR,area:graphene,graphene,negative differential resistance},
   area = {graphene}
   doi = {10.1021/jp3003646},
  
}
Yi-Peng An, Xinyuan Wei & Zhong-Qin Yang, Improving electronic transport of zigzag graphene nanoribbons by ordered doping of B or N atoms, Phys. Chem. Chem. Phys., Vol. 14(45), pp. 15802--15806 (2012)
Abstract    BibTeX    DOI: 10.1039/C2CP42123B   
Abstract: Using an ab initio method, we explored electronic structures and transport properties of zigzag graphene nanoribbons (ZGNRs) with ordered doping of B or N atoms. We find B or N atoms doping can increase significantly the conductance of the ZGNRs with an even number of zigzag chains due to additional conducting channels being induced and the breakdown of parity limitation. The higher the doping concentration, the larger the current amplification factor obtained. For the nanojunctions with one row B (or N) atoms, the current amplification factor can be larger when the doping position is near to the center, while for the junction with two rows, the trend is subtle due to the interactions between the two rows of B (or N) atoms. Negative differential resistive phenomena are found for the case of B doping at low concentrations and the case for N doping. The conductance of the ZGNR with odd numbers of zigzag chains can also be increased by doping of B or N atoms. More interestingly, the B or N doping can almost completely remove the even-odd effect on electronic transport of the ZGNRs. Our studies provide avenues to drastically improve the electronic transport of ZGNRs, helpful for graphene applications.
BibTeX:
@article{An2012c,
   title = {Improving electronic transport of zigzag graphene nanoribbons by ordered doping of B or N atoms},
   author = {An, Yi-Peng and Wei, Xinyuan and Yang, Zhong-Qin},
  
   journal = {Phys. Chem. Chem. Phys.},
  
   publisher = {The Royal Society of Chemistry},
   volume = {14},
   number = {45},
   pages = {15802--15806},
   year = {2012},
   keywords = {NDR,area:graphene,doping,field-effect transistors,negative differential resistance},
   area = {graphene}
   doi = {10.1039/C2CP42123B},
  
}
Yi-Peng An, Chuan-Lu Yang, Mei-Shan Wang, Xiao-Guang Ma & De-Hua Wang, Ab initio investigations of the charge transport properties of endohedral M@C20 (M = Na and K) metallofullerenes, Chinese Physics B, Vol. 19(11), pp. 113402 (2010)
Abstract    BibTeX    DOI: 10.1088/1674-1056/19/11/113402   
Abstract: Using density functional theory and quantum transport calculations based on nonequilibum Green's function formalism, we investigate the charge transport properties of endohedral M@C20 (M = Na and K) metallofullerenes. Our results show that the conductance of C 20 fullerene can be obviously improved by insertion of alkali atom at its centre. Both linear and nonlinear sections are found on the I-V curves of the Au-M@C20 -Au two-probe systems. The novel negative differential resistance behaviour is also observed in Na@C20 molecule but not in K@C20 .
BibTeX:
@article{An2010b,
   title = {Ab initio investigations of the charge transport properties of endohedral M@C20 (M = Na and K) metallofullerenes},
   author = {An, Yi-Peng and Yang, Chuan-Lu and Wang, Mei-Shan and Ma, Xiao-Guang and Wang, De-Hua},
  
   journal = {Chinese Physics B},
  
  
   volume = {19},
   number = {11},
   pages = {113402},
   year = {2010},
   keywords = {area:fullerenes,cluster,conductance,density functional theory,electronic transport,first-principles,metal,metallofullerenes,molecules,negative differential resistance,nonequilibum Green's function},
   area = {fullerenes}
   doi = {10.1088/1674-1056/19/11/113402},
  
}
Yi-Peng An, Chuan-Lu Yang, Mei-Shan Wang, Xiao-Guang Ma & De-Hua Wang, First-principles study of electronic transport properties of C20F20 molecule, Acta Physica Sinica, Vol. 59(3), pp. 2010--2015 (2010)
Abstract    BibTeX    URL: http://www.oalib.com/paper/1447434   
Abstract: Using first-principles density functional theory and non-equilibrium Green's function method, we investigated the electronic transport properties of C20F20 molecule. The calculation shows that the zero bias equilibrium conductance of C20F20 molecule is 0.385 G0. The I-V curve presents good linear characteristic. Under finite bias voltage the molecule displays stable conductance characteristic, and could be made as one steadying resistance molecular device.
BibTeX:
@article{An2010,
   title = {First-principles study of electronic transport properties of C20F20 molecule},
   author = {An, Yi-Peng and Yang, Chuan-Lu and Wang, Mei-Shan and Ma, Xiao-Guang and Wang, De-Hua},
  
   journal = {Acta Physica Sinica},
  
  
   volume = {59},
   number = {3},
   pages = {2010--2015},
   year = {2010},
   keywords = {area:molecular electronics,fullerene,molecular device},
   area = {molecular electronics}
  
   url = {http://www.oalib.com/paper/1447434},
}
Yi-Peng An, Chuan-Lu Yang, Mei-Shan Wang, Xiao-Guang Ma & De-Hua Wang, First-principles study of transport properties of endohedral Li@C20 metallofullerene, Current Applied Physics, Vol. 10(1), pp. 260--265 (2010)
Abstract    BibTeX    DOI: 10.1016/j.cap.2009.06.003   
Abstract: The transport properties of the endohedral Li@C20 metallofullerene are studied using density functional non-equilibrium Green's function method. The equilibrium conductance of Li@C20 metallofullerene becomes larger than that of the empty C20 fullerene molecule. The I-V curve under low-bias voltage shows the characteristic of metallic behavior; another, the novel negative differential resistance behavior is also observed. It is found that the doping effect of Li atom significantly changes the transport properties of C20 fullerene.
BibTeX:
@article{An2010a,
   title = {First-principles study of transport properties of endohedral Li@C20 metallofullerene},
   author = {An, Yi-Peng and Yang, Chuan-Lu and Wang, Mei-Shan and Ma, Xiao-Guang and Wang, De-Hua},
  
   journal = {Current Applied Physics},
  
  
   volume = {10},
   number = {1},
   pages = {260--265},
   year = {2010},
   keywords = {Li@C20 metallofullerene,area:fullerenes,fullerenes},
   area = {fullerenes}
   doi = {10.1016/j.cap.2009.06.003},
  
}
Yi-Peng An, Chuan-Lu Yang, Mei-Shan Wang, Xiao-Guang Ma & De-Hua Wang, First-Principles Study of Electronic Transport Properties of Dodecahedrane C20H20 and Its Endohedral Complex Li@C20H20, The Journal of Physical Chemistry C, Vol. 113(35), pp. 15756--15760 (2009)
Abstract    BibTeX    DOI: 10.1021/jp904202c   
Abstract: The charge transport properties of the dodecahedrane C20H20 molecule and its endohedral complex Li@C20H20 are studied using density functional nonequilibrium Green's function method. Their zero bias equilibrium conductances and characteristics of current-voltage curves are first determined. The I-V curves under finite bias voltage confirm that the electrical conductivity will be improved by inserting the Li atom into the C20H20 molecule. The present results also show that the hydrogen atoms outside of the molecule are not beneficial to the electronic transport. Some potential applications of these two molecules are suggested.
BibTeX:
@article{An2009,
   title = {First-Principles Study of Electronic Transport Properties of Dodecahedrane C20H20 and Its Endohedral Complex Li@C20H20},
   author = {An, Yi-Peng and Yang, Chuan-Lu and Wang, Mei-Shan and Ma, Xiao-Guang and Wang, De-Hua},
  
   journal = {The Journal of Physical Chemistry C},
  
   publisher = {American Chemical Society},
   volume = {113},
   number = {35},
   pages = {15756--15760},
   year = {2009},
   keywords = {area:fullerenes,fullerenes,molecular electronics},
   area = {fullerenes}
   doi = {10.1021/jp904202c},
  
}
Yi-Peng An, Chuan-Lu Yang, Mei-Shan Wang, Xiao-Guang Ma & De-Hua Wang, First-principles study of structure and quantum transport properties of C[sub 20] fullerene, The Journal of Chemical Physics, Vol. 131(2), pp. 24311 (2009)
Abstract    BibTeX    DOI: 10.1063/1.3159024   
Abstract: Using first-principles density-functional theory and nonequilibrium Green's function formalism for quantum transport calculation, we study the electronic and transport properties of C20 fullerene molecule. Our results show that the equilibrium conductance of C20 molecule is near 1G0. It is found that the I-V curve displays a linear region centered about V=0 and nonlinear behavior under higher bias voltages and an obvious negative differential resistance phenomenon in a certain bias voltage range. The mechanism for the negative differential resistance behavior of C20 is suggested. The present findings could be helpful for the application of the C20 molecule in the field of single molecular devices or nanometer electronics.
BibTeX:
@article{An2009a,
   title = {First-principles study of structure and quantum transport properties of C[sub 20] fullerene},
   author = {An, Yi-Peng and Yang, Chuan-Lu and Wang, Mei-Shan and Ma, Xiao-Guang and Wang, De-Hua},
  
   journal = {The Journal of Chemical Physics},
  
   publisher = {AIP},
   volume = {131},
   number = {2},
   pages = {24311},
   year = {2009},
   keywords = {Green's function methods,ab initio calculations,area:fullerenes,density functional theory,fullerenes,molecular electronics},
   area = {fullerenes}
   doi = {10.1063/1.3159024},
  
}
Yi-Peng An & Zhong-Qin Yang, Spin-filtering and switching effects of a single-molecule magnet Mn(dmit)[sub 2], Journal of Applied Physics, Vol. 111(4), pp. 43713 (2012)
Abstract    BibTeX    DOI: 10.1063/1.3686722   
Abstract: We investigated spin-dependent transport properties of a single-molecule magnet Mn(dmit)2 with a coplanar or perpendicular conformation using first-principles density functional theory combined with nonequilibrium Green's function method. It was found that the current flowing through the junction comprised of two Au leads and a Mn(dmit)2 molecule is high spin-polarized, up to a high efficiency of 82%, if the two ligands of the molecule are orientated in the same plane. The current is strongly suppressed when a ligand is rotated and perpendicular to the other. These results suggest that Mn(dmit)2 is a potential candidate for spin filters or molecular switches.
BibTeX:
@article{An2012a,
   title = {Spin-filtering and switching effects of a single-molecule magnet Mn(dmit)[sub 2]},
   author = {An, Yi-Peng and Yang, Zhong-Qin},
  
   journal = {Journal of Applied Physics},
  
   publisher = {AIP},
   volume = {111},
   number = {4},
   pages = {43713},
   year = {2012},
   keywords = {area:molecular electronics,area:spintronics,molecular electronics,molecular switch,single-molecule magnet,spin filter,spin polarised transport},
   area = {molecular electronics,spintronics}
   doi = {10.1063/1.3686722},
  
}
Yi-Peng An & Zhong-Qin Yang, Abnormal electronic transport and negative differential resistance of graphene nanoribbons with defects, Applied Physics Letters, Vol. 99(19), pp. 192102 (2011)
Abstract    BibTeX    DOI: 10.1063/1.3660228   
Abstract: Electronic transport properties of zigzag graphene nanoribbons (GNRs) with two kinds of triangular defects are explored by using an ab-initio method. At a certain bias, the current of the GNR with an upward-triangle defect can be surprisingly larger than that of the perfect GNR due to the defect-induced symmetry breaking and more conductive channels. Dissimilarly, if the orientation of the triangle is changed rightward, the current is depressed much and shows negative differential resistance behavior. Our findings indicate that defect designs can be an efficient way to tune the electronic transport of GNR nanodevices.
BibTeX:
@article{An2011a,
   title = {Abnormal electronic transport and negative differential resistance of graphene nanoribbons with defects},
   author = {An, Yi-Peng and Yang, Zhong-Qin},
  
   journal = {Applied Physics Letters},
  
   publisher = {AIP},
   volume = {99},
   number = {19},
   pages = {192102},
   year = {2011},
   keywords = {Fermi level,NDR,ab initio calculations,area:graphene,defect states,graphene,nanostructured materials,negative differential resistance},
   area = {graphene}
   doi = {10.1063/1.3660228},
  
}
Yi-Peng An, Zhong-Qin Yang & Mark A. Ratner, High-efficiency switching effect in porphyrin-ethyne-benzene conjugates, Journal of Chemical Physics, Vol. 135(4), pp. 44706 (2011)
Abstract    BibTeX    DOI: 10.1063/1.3615492   
Abstract: We have explored the electronic transport properties of porphyrin-ethyne-benzene conjugates using an ab initio method. The results indicate that these ethyne-bridged phenyl porphyrin molecules can be used as candidates for molecular switching devices. The coplanar conformation of phenyl and porphyrin moieties allows a far larger current than the perpendicular conformation due to the near vanishing overlap of the frontier molecular orbitals (pi channels) in the porphyrin and phenyl parts in the latter. Higher current ratios of ON/OFF states can be obtained if amino or nitro substituent is placed at the position meta to the bridge connecting the pi systems of the molecule. The substituent group affects the electronic state energy of the entire molecule in coplanar conformation, while only affecting the local part in perpendicular conformation. More complex ethyne-bridged diphenyl porphyrin molecules are found to yield more complex and interesting switching effects. Our results suggest that such molecular wires composed of appropriate pi-conjugated molecules, can generally display perfect switching function and the efficiency can be tuned flexibly by adding certain substituent groups to the conjugates.
BibTeX:
@article{An2011,
   title = {High-efficiency switching effect in porphyrin-ethyne-benzene conjugates},
   author = {An, Yi-Peng and Yang, Zhong-Qin and Ratner, Mark A},
  
   journal = {Journal of Chemical Physics},
  
   publisher = {AIP},
   volume = {135},
   number = {4},
   pages = {44706},
   year = {2011},
   keywords = {ab initio calculations,area:molecular electronics,controlled conductance,dependence,electrical conductivity transitions,electron-transfer,geometry,molecular electronics,organic compounds,resistance,single-molecule junction,transistor,transport,wires},
   area = {molecular electronics}
   doi = {10.1063/1.3615492},
  
}
Benoy Anand, Mehmet Karakaya, Gyan Prakash, S. Siva Sankara Sai, Reji Philip, Paola Ayala, Anurag Srivastava, Ajay K. Sood, Apparao M. Rao & Ramakrishna Podila, Dopant-configuration controlled carrier scattering in graphene, RSC Adv., Vol. 5(73), pp. 59556--59563 (2015)
Abstract    BibTeX    DOI: 10.1039/C5RA05338B   
Abstract: Controlling optical and electronic properties of graphene via substitutional doping is central to many fascinating applications. Doping graphene with boron (B) or nitrogen (N) has led to p- or n-type graphene; however, the electron mobility in doped-graphene is severely compromised due to increased electron-defect scattering. Here, we demonstrate through Raman spectroscopy, nonlinear optical and ultrafast spectroscopy, and density functional theory that the graphitic dopant configuration is stable in graphene and does not significantly alter electron–electron or electron–phonon scattering, that is otherwise present in doped graphene, by preserving the crystal coherence length (La).
BibTeX:
@article{Anand2015,
   title = {Dopant-configuration controlled carrier scattering in graphene},
   author = {Anand, Benoy and Karakaya, Mehmet and Prakash, Gyan and Sankara Sai, S. Siva and Philip, Reji and Ayala, Paola and Srivastava, Anurag and Sood, Ajay K. and Rao, Apparao M. and Podila, Ramakrishna},
  
   journal = {RSC Adv.},
  
   publisher = {Royal Society of Chemistry},
   volume = {5},
   number = {73},
   pages = {59556--59563},
   year = {2015},
   keywords = {area:graphene},
   area = {graphene}
   doi = {10.1039/C5RA05338B},
  
}
David Q. Andrews, Revital Cohen, Richard P. Van Duyne & Mark A. Ratner, Single molecule electron transport junctions: Charging and geometric effects on conductance, Journal of Chemical Physics, Vol. 125(17), pp. 174718 (2006)
Abstract    BibTeX    DOI: 10.1063/1.2363182   
Abstract: A p-benzenedithiolate (BDT) molecule covalently bonded between two gold electrodes has become one of the model systems utilized for investigating molecular transport junctions. The plethora of papers published on the BDT system has led to varying conclusions with respect to both the mechanism and the magnitude of transport. Conductance variations have been attributed to difficulty in calculating charge transfer to the molecule, inability to locate the Fermi energy accurately, geometric dispersion, and stochastic switching. Here we compare results obtained using two transport codes, TRANSIESTA-C and HÜCKEL-IV, to show that upon Au-S bond lengthening, the calculated low bias conductance initially increases by up to a factor of 30. This increase in highest occupied molecular orbital (HOMO) mediated conductance is attributed to charging of the terminal sulfur atom and a corresponding decrease in the energy gap between the Fermi level and the HOMO. Addition of a single Au atom to each terminal of the extended BDT molecule is shown to add four molecular states near the Fermi energy, which may explain the varying results reported in the literature.
BibTeX:
@article{Andrews2006,
   title = {Single molecule electron transport junctions: Charging and geometric effects on conductance},
   author = {Andrews, David Q and Cohen, Revital and Van Duyne, Richard P and Ratner, Mark A},
  
   journal = {Journal of Chemical Physics},
  
   publisher = {AIP},
   volume = {125},
   number = {17},
   pages = {174718},
   year = {2006},
   keywords = {TranSIESTA-C,area:molecular electronics,molecular electronics},
   area = {molecular electronics}
   doi = {10.1063/1.2363182},
  
}
David Q. Andrews, Richard P. Van Duyne & Mark A. Ratner, Stochastic Modulation in Molecular Electronic Transport Junctions: Molecular Dynamics Coupled with Charge Transport Calculations, Nano Letters, Vol. 8(4), pp. 1120--1126 (2008)
Abstract    BibTeX    DOI: 10.1021/nl073265l   
Abstract: The experimental variation in conductance that can be expected through dynamically evolving Au-molecule-Au junctions is approximated using molecular dynamics to model thermal fluctuations and a nonequilibrium Green's function code (Hückel-IV 2.0) to calculate the charge transport. This generates a statistical set of conductance data that can be used to compare directly with experimental results. Experimental measurements on Au-single molecule junctions show a large variation in conductance values between different identically prepared junctions. Our computational results indicate that the Au-Au and the Au-molecule fluctuations provide extensive geometric freedom and an associated broad distribution in calculated conductance values. Our results show agreement with experimental measurements of the low bias voltage conductance and conductance distribution for both thiol-Au and amine-Au linker structures.
BibTeX:
@article{Andrews2008a,
   title = {Stochastic Modulation in Molecular Electronic Transport Junctions: Molecular Dynamics Coupled with Charge Transport Calculations},
   author = {Andrews, David Q and Duyne, Richard P Van and Ratner, Mark A},
  
   journal = {Nano Letters},
  
  
   volume = {8},
   number = {4},
   pages = {1120--1126},
   year = {2008},
   keywords = {area:molecular electronics,molecular electronics},
   area = {molecular electronics}
   doi = {10.1021/nl073265l},
  
}
David Q. Andrews, Gemma C. Solomon, Randall H. Goldsmith, Thorsten Hansen, Michael R. Wasielewski, Richard P. Van Duyne & Mark A. Ratner, Quantum Interference: The Structural Dependence of Electron Transmission through Model Systems and Cross-Conjugated Molecules, Journal of Physical Chemistry C, Vol. 112(43), pp. 16991--16998 (2008)
Abstract    BibTeX    DOI: 10.1021/jp805588m   
Abstract: We report on a class of molecules that exhibit nonlinear current/voltage behavior in the low bias tunneling regime. This interesting behavior is attributed to quantum interference. Using site models, we show that interference features, while common, do not necessarily occur at experimentally relevant energies, hindering realization in transport measurements. Calculations made using a nonequilibrium Green's function code show that quantum interference can be experimentally relevant in cross-conjugated molecules. A detailed bond length analysis of cross-conjugated molecules gives insight into why these molecules have interference at energetically accessible regions. The interference features are shown to be stable to both an electronic dephasing analysis and geometric fluctuations provided by molecular dynamics.
BibTeX:
@article{Andrews2008,
   title = {Quantum Interference: The Structural Dependence of Electron Transmission through Model Systems and Cross-Conjugated Molecules},
   author = {Andrews, David Q and Solomon, Gemma C and Goldsmith, Randall H and Hansen, Thorsten and Wasielewski, Michael R and Van Duyne, Richard P and Ratner, Mark A},
  
   journal = {Journal of Physical Chemistry C},
  
   publisher = {AMER CHEMICAL SOC},
   volume = {112},
   number = {43},
   pages = {16991--16998},
   year = {2008},
   keywords = {area:molecular electronics,interference,molecular electronics},
   area = {molecular electronics}
   doi = {10.1021/jp805588m},
  
}
Abbas Arab, A.V. Davydov, Dimitrios A. Papaconstantopoulos & Q. Li, Monolayer MoS2 Nanoribbons as a Promising Material for Both n-type and p-type Legs in Thermoelectric Generators, Journal of Electronic Materials, Vol. 45(10), pp. 5253--5263 (2016)
Abstract    BibTeX    DOI: 10.1007/s11664-016-4725-9   
Abstract: First-principles calculations have been performed to study the thermoelectric properties of monolayer MoS2 armchair nanoribbons (ACNRs). The electronic behavior of nanoribbons is dominated by the presence of edge states that are dependent on the number of zigzag chains across the nanoribbon. In addition, it is found that the phonon thermal conductance of monolayer MoS2 ACNRs is smaller than monolayer films due to phonon edge scattering. This effect is more pronounced in narrower nanoribbons, which leads to a higher ZT value compared to a monolayer MoS2 sheet. The effects of sulfur vacancy and edge roughness on the thermoelectric properties of MoS2 ACNRs have also been studied. We found that edge roughness decreased ZT values compared to those of perfect nanoribbons, as its impact on electrical conductance is more severe than on phonon thermal conductance. Sulfur vacancy, however, improved ZT in some subbands. It is shown that ZT values as high as 4 for electron-doped and 3 for hole-doped nanoribbons can be achieved at T = 500 K. The ability to achieve high ZT values for both p-type and n-type nanoribbons makes monolayer MoS2 ACNR a promising candidate for future solid-state thermoelectric generators.
BibTeX:
@article{Arab2016,
   title = {Monolayer MoS2 Nanoribbons as a Promising Material for Both n-type and p-type Legs in Thermoelectric Generators},
   author = {Arab, Abbas and Davydov, A. V. and Papaconstantopoulos, Dimitrios A and Li, Q.},
  
   journal = {Journal of Electronic Materials},
  
  
   volume = {45},
   number = {10},
   pages = {5253--5263},
   year = {2016},
   keywords = {MoS2 Nanoribbon,Thermoelectric generation,ZT,area:2dmat,area:tmd,seebeck coefficient},
   area = {2dmat,tmd}
   doi = {10.1007/s11664-016-4725-9},
  
}
Abbas Arab & Qiliang Li, Anisotropic thermoelectric behavior in armchair and zigzag mono- and fewlayer MoS2 in thermoelectric generator applications, Scientific Reports, Vol. 5 pp. 13706 (2015)
Abstract    BibTeX    DOI: 10.1038/srep13706   
Abstract: In this work, we have designed and simulated new thermoelectric generator based on monolayer and few-layer MoS2 nanoribbons. The proposed thermoelectric generator is composed of thermocouples made of both n-type and p-type MoS2 nanoribbon legs. Density Functional Tight-Binding Non-Equilibrium Green's Function (DFTB-NEGF) method has been used to calculate the transmission spectrum of MoS2 armchair and zigzag nanoribbons. Phonon transmission spectrum are calculated based on parameterization of Stillinger-Weber potential. Thermoelectric figure of merit, ZT, is calculated using these electronic and phonon transmission spectrum. Monolayer and bilayer MoS2 armchair nanoribbons are found to have the highest ZT value for p-type and n-type legs, repectively. Moreover, we have compared the thermoelectric current of doped monolayer MoS2 armchair nanoribbons and SZi thin films. Results indicate that thermoelectric current of MoS2 monolayer nanoribbons is several orders of magnitude higher than that of Si thin films.
BibTeX:
@article{Arab2015,
   title = {Anisotropic thermoelectric behavior in armchair and zigzag mono- and fewlayer MoS2 in thermoelectric generator applications},
   author = {Arab, Abbas and Li, Qiliang},
  
   journal = {Scientific Reports},
  
  
   volume = {5},
  
   pages = {13706},
   year = {2015},
   keywords = {area:2dmat,area:thermo,area:tmd},
   area = {2dmat,thermo,tmd}
   doi = {10.1038/srep13706},
  
}
Masaaki Araidai & Masaru Tsukada, Theoretical calculations of electron transport in molecular junctions: Inflection behavior in Fowler-Nordheim plot and its origin, Physical Review B, Vol. 81(23), pp. 235114 (2010)
Abstract    BibTeX    DOI: 10.1103/PhysRevB.81.235114   
Abstract: We investigated the origin of an inflection behavior appearing in Fowler-Nordheim (F-N) plot of current-voltage characteristics for molecular junctions using two different levels of calculation methods: nonequilibrium Green's-function technique combined with the density-functional theory and tight-binding approximation. Although the inflection has so far been interpreted from the naive model that the charge transport mechanism transits from a direct to the F-N tunneling, our results indicated that the inflection does not necessarily mean the transition between the two regimes. We found from the close examination of the relation between the behavior of the F-N curve and the transmission function that the inflection takes place when the molecular level responsible for electric currents approaches to the edge of the bias window. While our interpretation for the inflection drastically differ from the conventional model, the F-N plots obtained from our calculations showed closely similar behavior as those from the recent experiments.
BibTeX:
@article{Araidai2010,
   title = {Theoretical calculations of electron transport in molecular junctions: Inflection behavior in Fowler-Nordheim plot and its origin},
   author = {Araidai, Masaaki and Tsukada, Masaru},
  
   journal = {Physical Review B},
  
   publisher = {American Physical Society},
   volume = {81},
   number = {23},
   pages = {235114},
   year = {2010},
   keywords = {area:molecular electronics,molecular electronics},
   area = {molecular electronics}
   doi = {10.1103/PhysRevB.81.235114},
  
}
Masaaki Araidai & Masaru Tsukada, Diffusion processes in single-atom electromigration along a gold chain: First-principles calculations, Physical Review B, Vol. 80(4), pp. 45417 (2009)
Abstract    BibTeX    DOI: 10.1103/PhysRevB.80.045417   
Abstract: Electromigration of a single atom along a chain of gold atoms was investigated by first-principles calculations based on the nonequilibrium Green's-function technique combined with density-functional theory. In the case of electromigration of a gold atom, we found that the potential barrier along the migration pathway decreases as the applied bias voltage is increased and the migration direction is the same as that of electron flow. By considering the case of electromigration of a sulfur atom along the gold chain, we determined that the electron flow around the migrating atom is responsible for single-atom electromigration. The calculated electromigration rate for the gold atom indicated that the electromigration takes place at temperatures above room temperature.
BibTeX:
@article{Araidai2009,
   title = {Diffusion processes in single-atom electromigration along a gold chain: First-principles calculations},
   author = {Araidai, Masaaki and Tsukada, Masaru},
  
   journal = {Physical Review B},
  
   publisher = {APS},
   volume = {80},
   number = {4},
   pages = {45417},
   year = {2009},
   keywords = {Green's function methods,ab initio calculations,area:molecular electronics,density functional theory,electromigration,gold,molecular electronics,sulphur},
   area = {molecular electronics}
   doi = {10.1103/PhysRevB.80.045417},
  
}
Masaaki Araidai, Takahiro Yamamoto & Kenji Shiraishi, Asymmetric behavior of current-induced magnetization switching in a magnetic tunnel junction: Non-equilibrium first-principles calculations, Applied Physics Express, Vol. 7(4), pp. 45202 (2014)
Abstract    BibTeX    DOI: 10.7567/APEX.7.045202   
Abstract: We investigated the microscopic mechanisms of current-induced magnetization switching (CIMS) in an Fe/MgO(001)/Fe/Ta magnetic tunnel junction using non-equilibrium first-principles calculations. We found that the change in the magnetization configuration from antiparallel (AP) to parallel (P) can be realized with a lower electrical power than that from P to AP. From detailed analyses of the density of states subject to a finite bias voltage, we clarified that the asymmetric behavior originates from the difference in the electron scattering processes between switching directions.
BibTeX:
@article{Araidai2014,
   title = {Asymmetric behavior of current-induced magnetization switching in a magnetic tunnel junction: Non-equilibrium first-principles calculations},
   author = {Araidai, Masaaki and Yamamoto, Takahiro and Shiraishi, Kenji},
  
   journal = {Applied Physics Express},
  
  
   volume = {7},
   number = {4},
   pages = {45202},
   year = {2014},
   keywords = {Fe-MgO-Fe-Ta,MTJ,area:spintronics,graphene,magnetic tunnel junction},
   area = {spintronics}
   doi = {10.7567/APEX.7.045202},
  
}
Yoshihiro Asai & Hisao Nakamura, Non-Equilibrium Transport Theory Applied to Nano Electronics Problems, ECS Transactions, Vol. 64(14), pp. 63--69 (2014)
Abstract    BibTeX    DOI: 10.1017/CBO9781107415324.004   
Abstract: Theory of non-equilibrium transport has progressed a lot. The selfconsistent theory of both electric and phonon (and hence heat) currents including the electro-phonon coupling effects between them has been developed and it provides us useful information of the heat generation and the heat dissipation effects accompanying the currents. It will be a useful basic theory for the device simulator, if it could be combined with a large scale electronic structure method something like the DFTB method with which micron meter scale devices can be handled within realistic computational resources. The progress in this direction would be very fruitful for both semiconductor physics and device physics. Yet another useful example is a more material oriented study. In terms of the standard first principle Non-Equilibrium Green Function (NEGF) method, for an example, we discuss channel and electrode material dependence in electric current versus bias voltage profile of the resistive random access memory cell.
BibTeX:
@article{Asai2014,
   title = {Non-Equilibrium Transport Theory Applied to Nano Electronics Problems},
   author = {Asai, Yoshihiro and Nakamura, Hisao},
  
   journal = {ECS Transactions},
  
  
   volume = {64},
   number = {14},
   pages = {63--69},
   year = {2014},
   keywords = {ReRAM,area:interfaces},
   area = {interfaces}
   doi = {10.1017/CBO9781107415324.004},
  
}
Adila Syaidatul Binti Azman, Performance evaluation of multiple-channel armchair graphene nanoribbon field-effect transistor, (2014)
Abstract    BibTeX    URL: http://portal.fke.utm.my/fkelibrary/files/adilasyaidatulbintiazman/2014/   
Abstract: Optimized performance with maximized packing density and ability to deliver sufficient current are highly desirable in electronic devices like transistor. By 2015, it is predicted that the transistors will be manufactured with 9 nm technology. The dimensions of the transistors are so small that the conventional metal-oxide semiconductor field-effect transistors (MOSFETs) are no longer able to retain Moore's law due to short-channel effect. Hence, new materials such as strained silicon, high-k metal, silicon nanowire, carbon nanotube (CNT), graphene and graphene nanoribbon (GNR) are introduced. A number of studies have demonstrated various ways of fabricating array-channel graphene-based field-effect transistors (FETs). This thesis describes the performance evaluation of armchair graphene nanoribbon field-effect transistor (AGNR FET) with multiple channels. Energy band structures, transmission spectra, density of states and current-voltage (I-V) characteristic curves of single and multiple-channel AGNR FETs are extracted from the simulation using Atomistix Tool Kit (ATK) software version 13.8.1 from Quantum Wise. From the study, it is proven that the energy band gap of armchair graphene nanoribbon (AGNR) increases as the nanoribbon width is decreased. Its density of states and transmission coefficient also increase linearly with the number of conducting channels. It is also proven that the multiple-channel AGNR FET exhibits higher ON current compared to single-channel AGNR FET. The outcomes of this study indicate the feasibility of using multiple conducting channels AGNR FET.
BibTeX:
@phdthesis{Azman2014,
   title = {Performance evaluation of multiple-channel armchair graphene nanoribbon field-effect transistor},
   author = {Azman, Adila Syaidatul Binti},
  
  
  
  
  
  
  
   year = {2014},
   keywords = {FET,area:graphene,graphene},
   area = {graphene}
  
   url = {http://portal.fke.utm.my/fkelibrary/files/adilasyaidatulbintiazman/2014/},
}
Adila Syaidatul Binti Azman, Z. Johari & R. Ismail, Performance evaluation of dual-channel armchair graphene nanoribbon field-effect transistor, pp. 138--141 (2014)
Abstract    BibTeX    DOI: 10.1109/SMELEC.2014.6920815   
Abstract: Graphene has become a potential successor to silicon in electronic devices. In this paper, the performance of dual-channel armchair graphene nanoribbon field-effect transistor (AGNR FET) is investigated. Both physical and electrical properties of dual-channel AGNR FET are simulated using Atomistic Tool Kit from Quantum Wise. Their band structures and transmission spectra are analyzed. Current-voltage characteristic is then extracted and the performance of single and dual-channel AGNR FETs is compared. From the simulation, it is found that dual-channel AGNR FET exhibits significant improvement in ON current over two fold. Results obtained will give insight in the implementation of dual-channel AGNR FET for performance enhancement in future electronic devices.
BibTeX:
@inproceedings{Azman2014a,
   title = {Performance evaluation of dual-channel armchair graphene nanoribbon field-effect transistor},
   author = {Azman, Adila Syaidatul Binti and Johari, Z and Ismail, R},
   booktitle = {2014 IEEE International Conference on Semiconductor Electronics},
  
  
  
  
  
   pages = {138--141},
   year = {2014},
   keywords = {Arrays,Electrodes,Field effect transistors,Graphene,ON current,Performance evaluation,Photonic band gap,area:graphene,armchair graphene nanoribbon,atomistic tool kit,band structures,current-voltage characteristic,dual-channel,dual-channel armchair graphene nanoribbon field-ef,electrical properties,electronic devices,field effect transistors,field-effect transistor,graphene,nanoribbons,performance evaluation,physical properties,single channel AGNR FET,transmission spectra},
   area = {graphene}
   doi = {10.1109/SMELEC.2014.6920815},
  
}
V.M.K. Bagci & C.C. Kaun, Recognizing nucleotides by cross-tunneling currents for DNA sequencing, Physical Review E, Vol. 84(1), pp. 11917 (2011)
Abstract    BibTeX    DOI: 10.1103/PhysRevE.84.011917   
Abstract: Using first-principles calculations, we study electron transport through nucleotides inside a rectangular nanogap formed by two pairs of gold electrodes which are perpendicular and parallel to the nucleobase plane. We propose that this setup will enhance the nucleotide selectivity of tunneling signals to a great extent. Information from three electrical probing processes offers full nucleotide recognition, which survives the noise from neighboring nucleotides and configuration fluctuations.
BibTeX:
@article{Bagci2011,
   title = {Recognizing nucleotides by cross-tunneling currents for DNA sequencing},
   author = {Bagci, V M K and Kaun, C C},
  
   journal = {Physical Review E},
  
   publisher = {Amer Physical Soc},
   volume = {84},
   number = {1},
   pages = {11917},
   year = {2011},
   keywords = {DNA,area:molecular electronics,bases,molecule,nanopore,nucleotides,transverse electronic transport},
   area = {molecular electronics}
   doi = {10.1103/PhysRevE.84.011917},
  
}
Ping Bai, C.C. Chong, E.P. Li & Z. Chen, A molecular diode based on conjugated co-oligomers, International Journal of Nanoscience, Vol. 5(4-5), pp. 535--540 (2006)
Abstract    BibTeX    DOI: 10.1142/S0219581X06004759   
Abstract: A molecular diode based on a conjugated co-oligomer composed of p-type and n-type segments is investigated using the first principles method. The co-oligomer is connected to Au electrodes to form an Au-oligomer-Au system. The infinite system is dealt with a finite structure confined in a device region and effects from semi-infinite electrodes. Density functional theory and nonequilibrium Green's function are used to describe the device region self-consistently. The current-voltage (I-V) characteristics of the constructed system are calculated and a rectification behavior is observed. The energy gap and the spatial orientation of molecular orbitals, and the transmission functions are calculated to analyze the I-V characteristics of the molecular diode.
BibTeX:
@article{Bai2006,
   title = {A molecular diode based on conjugated co-oligomers},
   author = {Bai, Ping and Chong, C C and Li, E P and Chen, Z},
  
   journal = {International Journal of Nanoscience},
  
  
   volume = {5},
   number = {4-5},
   pages = {535--540},
   year = {2006},
   keywords = {TranSIESTA-C,area:molecular electronics,molecular electronics},
   area = {molecular electronics}
   doi = {10.1142/S0219581X06004759},
  
}
Ping Bai, Kai-Tak Lam, Erping Li & Ken Kai-fu Chang, A Comprehensive Atomic Study of Carbon Nanotube Schottky Diode Using First Principles Approach, pp. 749--752 (2007)
Abstract    BibTeX    DOI: 10.1109/IEDM.2007.4419055   
Abstract: In this paper, Carbon nanotube (CNT) Schottky diodes are investigated from the atomic perspective using the first principles DFT-NEGF method. Two atomic models are built based on experimental setting. The atomic behaviors of the CNT Schottky diodes are explored through density of states and charge transfer of the atomic models. The electron transport properties of the CNT diodes are analyzed through transmission function, energy gap shifting and I-V characteristics.
BibTeX:
@inproceedings{Bai2007a,
   title = {A Comprehensive Atomic Study of Carbon Nanotube Schottky Diode Using First Principles Approach},
   author = {Bai, Ping and Lam, Kai-Tak and Li, Erping and Chang, Ken Kai-fu},
   booktitle = {Electron Devices Meeting, 2007. IEDM 2007. IEEE International},
  
  
   publisher = {IEEE, 345 E 47th St, New York, NY 10017 USA},
  
  
   pages = {749--752},
   year = {2007},
   keywords = {DFT-NEGF method,I-V characteristics,Schottky diodes,area:nanotubes,atomic models,carbon nanotube Schottky diode,carbon nanotubes,charge exchange,charge transfer,comprehensive atomic study,energy gap shifting},
   area = {nanotubes}
   doi = {10.1109/IEDM.2007.4419055},
  
}
Ping Bai, E. Li, Kai-Tak Lam, O. Kurniawan & W.S. Koh, Carbon nanotube Schottky diode: an atomic perspective, Nanotechnology, Vol. 19 pp. 115203 (2008)
Abstract    BibTeX    DOI: 10.1088/0957-4484/19/11/115203   
Abstract: The electron transport properties of semiconducting carbon nanotube (SCNT) Schottky diodes are investigated with atomic models using density functional theory and the non-equilibrium Green's function method. We model the SCNT Schottky diode as a SCNT embedded in the metal electrode, which resembles the experimental set-up. Our study reveals that the rectification behaviour of the diode is mainly due to the asymmetric electron transmission function distribution in the conduction and valence bands and can be improved by changing metal-SCNT contact geometries. The threshold voltage of the diode depends on the electron Schottky barrier height which can be tuned by altering the diameter of the SCNT. Contrary to the traditional perception, the metal-SCNT contact region exhibits better conductivity than the other parts of the diode.
BibTeX:
@article{Bai2008,
   title = {Carbon nanotube Schottky diode: an atomic perspective},
   author = {Bai, Ping and Li, E and Lam, Kai-Tak and Kurniawan, O and Koh, W S},
  
   journal = {Nanotechnology},
  
  
   volume = {19},
  
   pages = {115203},
   year = {2008},
   keywords = {Schottky diode,area:nanotubes,nanotubes},
   area = {nanotubes}
   doi = {10.1088/0957-4484/19/11/115203},
  
}
Ping Bai, E. Li, Shuowang Yang & P.A. Collier, Theoretical investigation of metal-molecule interface with terminal group, pp. 116--118 (2004)
Abstract    BibTeX    DOI: 10.1109/NANO.2004.1392268   
Abstract: We studied the metal/molecule interface linkage effects through metal-molecule-metal systems by first principles method, which is based on the density functional theory (DFT) with norm conserving nonlocal pseudopotentials and nonequilibrium Green's functions (NEGF's) to calculate the charge distribution for open metal-molecule-metal systems. Metal electrodes were described through 3-D atomic model instead of a non-atomic (like jellium model) description of the electrodes. Several open systems were constructed, optimized and simulated. Sulphur atom (S) and cyano-group (CN) were employed to connect electrodes Au and molecule borazine. The current-voltage (I-V) characteristics, density of states (DOS), and the transmission function (TF) of constructed systems were investigated. Results show that transmission properties of the systems are affected a lot by the terminal group. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) are shifted and the magnitudes of TF are changed. Simulated I-V characteristics show that the system with terminal group CN presents better conductance.
BibTeX:
@inproceedings{Bai2004,
   title = {Theoretical investigation of metal-molecule interface with terminal group},
   author = {Bai, Ping and Li, E and Yang, Shuowang and Collier, P A},
   booktitle = {Nanotechnology, 4th IEEE Conference on},
  
  
  
  
  
   pages = {116--118},
   year = {2004},
   keywords = {TranSIESTA-C,area:molecular electronics},
   area = {molecular electronics}
   doi = {10.1109/NANO.2004.1392268},
  
}
Ping Bai, Er Ping Li, Chee Ching Chong & Zhikuan Chen, Effects of metal-molecule interface conformations on the electron transport of single molecule, Current Applied Physics, Vol. 6(3), pp. 531--535 (2006)
Abstract    BibTeX    DOI: 10.1016/j.cap.2005.11.054   
Abstract: The electron transport effects of molecule locations on the metal interface are investigated through metal-molecule-metal systems using the first principles method, based on density functional theory with norm conserving non-local pseudopotentials and non-equilibrium Green's functions. Three kinds of molecule-metal interface conformations are studied. These include locating the molecule on the top, at the hollow site and on the bridge of metal surface atoms. Au-molecule-Au open systems are constructed and numerically examined where Au electrodes are described through a 3-D atomic model. The current-voltage characteristics, density of states and transmission functions of constructed systems are calculated and analyzed. Simulated results show that the on-atom contact exhibits the best molecule-metal coupling when an external bias lower than 1.4 V is applied. The bridge contact has a similar coupling as the hollow contact with a small difference at larger external bias. This may partially explain why experimental results have poor repeatability.
BibTeX:
@article{Bai2006a,
   title = {Effects of metal-molecule interface conformations on the electron transport of single molecule},
   author = {Bai, Ping and Li, Er Ping and Chong, Chee Ching and Chen, Zhikuan},
  
   journal = {Current Applied Physics},
  
  
   volume = {6},
   number = {3},
   pages = {531--535},
   year = {2006},
   keywords = {TranSIESTA-C,area:molecular electronics,molecular electronics},
   area = {molecular electronics}
   doi = {10.1016/j.cap.2005.11.054},
  
}
Ping Bai, E.P. Li, E.A. Ong, P. Collier & K.P. Loh, Atomic study of molecular wires composed of thiophene oligomers, physica status solidi (a), Vol. 204(6), pp. 1876--1881 (2007)
Abstract    BibTeX    DOI: 10.1002/pssa.200675302   
Abstract: In this paper, we study the electron conductance of thiophene oligomers based molecular wires through atomic structures using the first principles method based on density functional theory and nonequilibrium Green's function. The molecular wires are built by sandwiching various thiophene oligomers between two metal electrodes via terminal groups at atomic levels. The effects of alkyl substituents on the thiophene oligomers are modelled by varying inter-ring angles of the oligomers. Thiophene dimers, tetramers and hexamers are used to studied thiophene size effects. The projected orbitals, energy gaps, transmission functions and current-voltage characteristics of the molecular wires are calculated and analyzed. Results show that the molecular wires with the planar structures of thiophene oligomers have larger electron transmission functions, hence better electronic conductance than those with twist structures. The conductance of molecular wires decreases when the chain length of the thiophene oligomer increases. The results can provide guidance for design of thiophene molecular electronic wires and other devices.
BibTeX:
@article{Bai2007,
   title = {Atomic study of molecular wires composed of thiophene oligomers},
   author = {Bai, Ping and Li, E P and Ong, E A and Collier, P and Loh, K P},
  
   journal = {physica status solidi (a)},
  
  
   volume = {204},
   number = {6},
   pages = {1876--1881},
   year = {2007},
   keywords = {area:molecular electronics,molecular wire},
   area = {molecular electronics}
   doi = {10.1002/pssa.200675302},
  
}
Ping Bai, Shuo-Wang Yang, Er-Ping Li & Ping Wu, Investigation of electron transport of open molecular structures based on first principles theory, International Journal of Nanoscience, Vol. 3(4-5), pp. 533--540 (2004)
Abstract    BibTeX    DOI: 10.1142/S0219581X04002346   
Abstract: We study the electron transport of thiolated benzene and borazine using ab initio method Transiesta through 3D atomic metal-molecule-metal structures. The calculation is based on well-established density functional theory (DFT) and nonequilibrium Green's functions (NEGF). DFT with norm conserving nonlocal pseudopotentials is used to define the atomic core and NEGF are used to calculate the charge distribution where the contributions of scattering sates and bound states to charge density are naturally accounted. The transmission functions and I-V characteristics are presented. Simulation results show that the conductance through benzene is about four times larger than through borazine. Negative differential resistance behavior is observed with borazine while saturation feature appears with benzene.
BibTeX:
@article{Bai2004a,
   title = {Investigation of electron transport of open molecular structures based on first principles theory},
   author = {Bai, Ping and Yang, Shuo-Wang and Li, Er-Ping and Wu, Ping},
  
   journal = {International Journal of Nanoscience},
  
  
   volume = {3},
   number = {4-5},
   pages = {533--540},
   year = {2004},
   keywords = {TranSIESTA-C,area:molecular electronics},
   area = {molecular electronics}
   doi = {10.1142/S0219581X04002346},
  
}
Zhaoqiang Bai, Yongqing Cai, Lei Shen, Guchang Han & Yuanping Feng, High-performance giant-magnetoresistance junctions based on the all-Heusler architecture with matched energy bands and Fermi surfaces, Applied Physics Letters, Vol. 102(15), pp. 152403 (2013)
Abstract    BibTeX    DOI: 10.1063/1.4802581   
Abstract: We present an all-Heusler architecture which could be used as a rational design scheme for achieving high spin-filter efficiency in the current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) devices. A Co2MnSi/Ni2NiSi/Co2MnSi trilayer stack is chosen as the prototype of such an architecture, of which the electronic structure and magnetotransport properties are systematically investigated by first principles approaches. Well matched energy bands and Fermi surfaces between the all-Heusler electrode-spacer pair are found, which, in combination with the electrode half-metallicity, indicate large bulk and interfacial spin-asymmetry, high spin-filter efficiency, and consequently good magnetoresistance performance. Transport calculations further confirm the superiority of the all-Heusler architecture over the conventional Heusler/transition-metal structure by comparing their transmission coefficients and interfacial resistances of parallel conduction electrons, as well as the macroscopic current-voltage characteristics. We suggest future theoretical and experimental efforts in developing high-performance all-Heusler CPP-GMR junctions for the read heads of the next generation high-density hard disk drives.
BibTeX:
@article{Bai2013a,
   title = {High-performance giant-magnetoresistance junctions based on the all-Heusler architecture with matched energy bands and Fermi surfaces},
   author = {Bai, Zhaoqiang and Cai, Yongqing and Shen, Lei and Han, Guchang and Feng, Yuanping},
  
   journal = {Applied Physics Letters},
  
   publisher = {AIP},
   volume = {102},
   number = {15},
   pages = {152403},
   year = {2013},
   keywords = {Fermi surface,ab initio calculations,area:interfaces,area:nvm,area:semi,area:spintronics,band structure,cobalt alloys,giant magnetoresistance,interfaces,manganese alloys,multilayers,nickel alloys,semi,silicon alloys,spin,spin systems},
   area = {interfaces,nvm,semi,spintronics}
   doi = {10.1063/1.4802581},
  
}
Zhaoqiang Bai, Yongqing Cai, Lei Shen, Ming Yang, Viloane Ko, Guchang Han & Yuanping Feng, Magnetic and transport properties of Mn[sub 3 - x]Ga/MgO/Mn[sub 3 - x]Ga magnetic tunnel junctions: A first-principles study, Applied Physics Letters, Vol. 100(2), pp. 22408 (2012)
Abstract    BibTeX    DOI: 10.1063/1.3676195   
Abstract: Magnetic and transport properties of Mn[3-x]Ga/MgO/Mn[3-x]Ga (0textless=xtextless=1) magnetic tunnel junctions are studied using first-principles approach based on density functional theory and non-equilibrium Green's function. Perpendicular magnetization, of which the magnetic anisotropy energy reaches more than 1 meV/unit-cell, is confirmed to be energetically favoured by both Mn2Ga and Mn3Ga thin films. Furthermore, despite high spin-polarization at the Fermi energy for both these compounds as reported, our transport calculation shows considerable disparity in the transmission behaviour between Mn2Ga/MgO/Mn2Ga(001) and Mn3Ga/MgO/Mn3Ga(001) magnetic tunnel junctions: huge optimistic tunneling magnetoresistance ratio of 103% for the former, and nevertheless, no tunneling magnetoresistance effect absolutely for the latter. This phenomenon is attributed to the symmetry selective filtering effect of the MgO spacer. On this premise, Mn[3-x]Ga compounds with low Mn concentration are predicted to be promising candidate materials to serve as the electrodes of spin-transfer torque devices in the next-generation data storage technique.
BibTeX:
@article{Bai2012,
   title = {Magnetic and transport properties of Mn[sub 3 - x]Ga/MgO/Mn[sub 3 - x]Ga magnetic tunnel junctions: A first-principles study},
   author = {Bai, Zhaoqiang and Cai, Yongqing and Shen, Lei and Yang, Ming and Ko, Viloane and Han, Guchang and Feng, Yuanping},
  
   journal = {Applied Physics Letters},
  
   publisher = {AIP},
   volume = {100},
   number = {2},
   pages = {22408},
   year = {2012},
   keywords = {Fermi level,Green's function methods,MIM structures,ab initio calculations,area:interfaces,area:nvm,area:semi,area:spintronics,density functional theory,gallium alloys,magnesium compounds,magnetic multilayers,magnetic thin films,manganese alloys,perpendicular magnetic anisotropy,spin polarised transport,tunnelling magnetoresistance},
   area = {interfaces,nvm,semi,spintronics}
   doi = {10.1063/1.3676195},
  
}
Zhaoqiang Bai, Y.H. Lu, L. Shen, V. Ko, G.C. Han & Y.P. Feng, Transport properties of high-performance all-Heusler Co2CrSi/Cu2CrAl/Co2CrSi giant magnetoresistance device, Journal of Applied Physics, Vol. 111(9), pp. 93911 (2012)
Abstract    BibTeX    DOI: 10.1063/1.4712301   
Abstract: Transport properties of giant magnetoresistance (MR) junction consisting of trilayer Co2CrSi/Cu2CrAl/Co2CrSi Heusler alloys (L21) are studied using first-principles approach based on density functional theory and the non-equilibrium Green's function method. Highly conductive channels are found in almost the entire k-plane when the magnetizations of the electrodes are parallel, while they are completely blocked in the antiparallel configuration, which leads to a high magnetoresistance ratio (the pessimistic MR ratio is nearly 100%). Furthermore, the calculated I-V curve shows that the device behaves as a good spin valve with a considerable disparity in currents under the parallel and antiparallel magnetic configurations of the electrodes. The Co2CrSi/Cu2CrAl/Co2CrSi junction could be useful for high-performance all-metallic current-perpendicular-to-plane giant magnetoresistance reading head for the next generation high density magnetic storage.
BibTeX:
@article{Bai2012a,
   title = {Transport properties of high-performance all-Heusler Co2CrSi/Cu2CrAl/Co2CrSi giant magnetoresistance device},
   author = {Bai, Zhaoqiang and Lu, Y H and Shen, L and Ko, V and Han, G C and Feng, Y P},
  
   journal = {Journal of Applied Physics},
  
   publisher = {AIP},
   volume = {111},
   number = {9},
   pages = {93911},
   year = {2012},
   keywords = {Green's function methods,MTJ,ab initio calculations,aluminium alloys,area:interfaces,area:nvm,area:spintronics,chromium alloys,cobalt alloys,copper alloys,density functional theory,electrodes,giant magnetoresistance,magnetic storage,silicon alloys,spin,spin valves},
   area = {interfaces,nvm,spintronics}
   doi = {10.1063/1.4712301},
  
}
Zhaoqiang Bai, Lei Shen, Yongqing Cai, Qingyun Wu, Minggang Zeng, Guchang Han & Yuan Ping Feng, Magnetocrystalline anisotropy and its electric-field-assisted switching of Heusler-compound-based perpendicular magnetic tunnel junctions, New Journal of Physics, Vol. 16(10), pp. 103033 (2014)
Abstract    BibTeX    DOI: 10.1088/1367-2630/16/10/103033   
Abstract: Employing density functional theory combined with the non-equilibrium Green's function formalism, we systematically investigate the structural, magnetic and magnetoelectric properties of the Co2FeAl(CFA)/MgO interface, as well as the spin-dependent transport characteristics of the CFA/MgO/CFA perpendicular magnetic tunnel junctions (p-MTJs). We find that the structure of the CFA/MgO interface with the oxygen-top FeAl termination has high thermal stability, which is protected by the thermodynamic equilibrium limit. Furthermore, this structure is found to have perpendicular magnetocrystalline anisotropy (MCA). Giant electric-field-assisted modifications of this interfacial MCA through magnetoelectric coupling are demonstrated with an MCA coefficient of up to 1E-7 erg / V cm. In addition, our non-collinear spin transport calculations of the CFA/MgO/CFA p-MTJ predict a good magnetoresistance performance of the device.
BibTeX:
@article{Bai2014,
   title = {Magnetocrystalline anisotropy and its electric-field-assisted switching of Heusler-compound-based perpendicular magnetic tunnel junctions},
   author = {Bai, Zhaoqiang and Shen, Lei and Cai, Yongqing and Wu, Qingyun and Zeng, Minggang and Han, Guchang and Feng, Yuan Ping},
  
   journal = {New Journal of Physics},
  
  
   volume = {16},
   number = {10},
   pages = {103033},
   year = {2014},
   keywords = {Heusler alloy,area:interfaces,area:nvm,area:spintronics,magnetic crystalline anisotropy,magnetic tunnel junction,magnetoelectric effect,non-collinear spin transport},
   area = {interfaces,nvm,spintronics}
   doi = {10.1088/1367-2630/16/10/103033},
  
}
Zhaoqiang Bai, Lei Shen, Qingyun Wu, Minggang Zeng, Jian-Sheng Wang, Guchang Han & Yuan Ping Feng, Boron diffusion induced symmetry reduction and scattering in CoFeB/MgO/CoFeB magnetic tunnel junctions, Physical Review B, Vol. 87(1), pp. 014114---- (2013)
Abstract    BibTeX    DOI: 10.1103/PhysRevB.87.014114   
Abstract: By first-principles analysis, we investigate the effect of thermal annealing on structural stability of CoFeB/MgO(thin)/CoFeB magnetic tunnel junctions. The calculated phonon dispersion indicates that Mg3B2O6 (kotoite) is a stable spacer after annealing due to B diffusion into MgO. The calculated tunneling magnetoresistance (TMR) of CoFe/kotoite/CoFe is 210%, which is in good agreement with the available experimental value and 2 orders of magnitude lower than the predicted values of CoFe/MgO/CoFe junctions. The physics of this more realistic TMR value is the change in symmetry from C4v of MgO to C2v of kotoite. Such symmetry reduction induces scattering and weakens the tunneling transmission of the Δ1-like Bloch states. Our calculations also reveal that the tunneling transmission is sensitive to the electrode/spacer interfacial chemical bonding. Residual boron, localized at the interface due to insufficient annealing temperature, can further reduce the TMR.
BibTeX:
@article{Bai2013,
   title = {Boron diffusion induced symmetry reduction and scattering in CoFeB/MgO/CoFeB magnetic tunnel junctions},
   author = {Bai, Zhaoqiang and Shen, Lei and Wu, Qingyun and Zeng, Minggang and Wang, Jian-Sheng and Han, Guchang and Feng, Yuan Ping},
  
   journal = {Physical Review B},
  
   publisher = {American Physical Society},
   volume = {87},
   number = {1},
   pages = {014114----},
   year = {2013},
   keywords = {MTJ,area:interfaces,area:nvm,area:semi,area:spintronics,boron,complex bandstructure,diffusion,magnetic tunnel junction,magnetoresistance,room-temperature,spin,transmission eigenstates,transmission pathways},
   area = {interfaces,nvm,semi,spintronics}
   doi = {10.1103/PhysRevB.87.014114},
  
}
Sun Young Baik, Yong Jae Cho, Young Rok Lim, Hyung Soon Im, Dong Myung Jang, Yoon Myung, Jeunghee Park & Hong Seok Kang, Charge-Selective Surface-Enhanced Raman Scattering Using Silver and Gold Nanoparticles Deposited on Silicon-Carbon Core-Shell Nanowires, ACS Nano, Vol. 6(3), pp. 2459--2470 (2012)
Abstract    BibTeX    DOI: 10.1021/nn204797b   
Abstract: The deposition of silver (Ag) or gold (Au) nanoparticles (NPs) on vertically aligned silicon-carbon (Si-C) core-shell nanowires (NWs) produces sensitive substrates for surface-enhanced Raman spectroscopy (SERS). The undoped and 30% nitrogen (N)-doped graphitic layers of the C shell (avg thickness of 20 nm) induce a higher sensitivity toward negatively (-) and positively (+) charged dye molecules, respectively, showing remarkable charge selectivity. The Ag NPs exhibit higher charge selectivity than the Au NPs. The Ag NPs deposited on p- and n-type Si NWs also exhibit (-) and (+) charge selectivity, respectively, which is higher than that of the Au NPs. The X-ray photoelectron spectroscopy analysis indicates that the N-doped graphitic layers donate more electrons to the metal NPs than the undoped ones. More distinct electron transfer occurs to the Ag NPs than to the Au NPs. First principles calculations of the graphene-metal adducts suggest that the large electron transfer capacity of the N-doped graphitic layers is due to the formation of a N-textgreaterAg coordinate bond involving the lone pair electrons of the N atoms. We propose that the more (-) charged NPs on the N-doped graphitic layers prefer the adsorption of (+) charged dyes, enhancing the SERS intensity. The charge selectivity of the Si NW substrates can also be rationalized by the greater electron transfer from the n-type Si to the metal NPs.
BibTeX:
@article{Baik2012,
   title = {Charge-Selective Surface-Enhanced Raman Scattering Using Silver and Gold Nanoparticles Deposited on Silicon-Carbon Core-Shell Nanowires},
   author = {Baik, Sun Young and Cho, Yong Jae and Lim, Young Rok and Im, Hyung Soon and Jang, Dong Myung and Myung, Yoon and Park, Jeunghee and Kang, Hong Seok},
  
   journal = {ACS Nano},
  
   publisher = {American Chemical Society},
   volume = {6},
   number = {3},
   pages = {2459--2470},
   year = {2012},
   keywords = {N-doped graphitic layers,area:nanowires,charge selectivity,electron transfer,first principles calculations,silicon nanowires,silver nanoparticles,surface-enhanced Raman scattering},
   area = {nanowires}
   doi = {10.1021/nn204797b},
  
}
Anirban Bandyopadhyay & Somobrata Acharya, A 16-bit parallel processing in a molecular assembly, Proceedings of the National Academy of Sciences, Vol. 105(10), pp. 3668--3672 (2008)
Abstract    BibTeX    DOI: 10.1073/pnas.0703105105   
Abstract: A machine assembly consisting of 17 identical molecules of 2,3,5,6-tetramethyl-1-4-benzoquinone (DRQ) executes 16 instructions at a time. A single DRQ is positioned at the center of a circular ring formed by 16 other DRQs, controlling their operation in parallel through hydrogen-bond channels. Each molecule is a logic machine and generates four instructions by rotating its alkyl groups. A single instruction executed by a scanning tunneling microscope tip on the central molecule can change decisions of 16 machines simultaneously, in four billion (4ˆ16) ways. This parallel communication represents a significant conceptual advance relative to today's fastest processors, which execute only one instruction at a time.
BibTeX:
@article{Bandyopadhyay2008,
   title = {A 16-bit parallel processing in a molecular assembly},
   author = {Bandyopadhyay, Anirban and Acharya, Somobrata},
  
   journal = {Proceedings of the National Academy of Sciences},
  
  
   volume = {105},
   number = {10},
   pages = {3668--3672},
   year = {2008},
   keywords = {area:molecular electronics,molecular switch},
   area = {molecular electronics}
   doi = {10.1073/pnas.0703105105},
  
}
Anirban Bandyopadhyay, Ranjit Pati, Satyajit Sahu, Ferdinand Peper & Daisuke Fujita, Massively parallel computing on an organic molecular layer, Nature Physics, Vol. 6(5), pp. 369--375 (2010)
Abstract    BibTeX    DOI: 10.1038/nphys1636   
Abstract: Modern computers operate at enormous speeds - capable of executing in excess of 10ˆ13 instructions per second - but their sequential approach to processing, by which logical operations are performed one after another, has remained unchanged since the 1950s. In contrast, although individual neurons of the human brain fire at around just 10ˆ3 times per second, the simultaneous collective action of millions of neurons enables them to complete certain tasks more efficiently than even the fastest supercomputer. Here we demonstrate an assembly of molecular switches that simultaneously interact to perform a variety of computational tasks including conventional digital logic, calculating Voronoi diagrams, and simulating natural phenomena such as heat diffusion and cancer growth. As well as representing a conceptual shift from serial-processing with static architectures, our parallel, dynamically reconfigurable approach could provide a means to solve otherwise intractable computational problems.
BibTeX:
@article{Bandyopadhyay2010,
   title = {Massively parallel computing on an organic molecular layer},
   author = {Bandyopadhyay, Anirban and Pati, Ranjit and Sahu, Satyajit and Peper, Ferdinand and Fujita, Daisuke},
  
   journal = {Nature Physics},
  
   publisher = {Nature Publishing Group},
   volume = {6},
   number = {5},
   pages = {369--375},
   year = {2010},
   keywords = {area:molecular electronics,molecular switch},
   area = {molecular electronics}
   doi = {10.1038/nphys1636},
  
}
L. Banerjee, A. Mukhopadhyay, A. Sengupta & H. Rahaman, Performance analysis of uniaxially strained monolayer black phosphorus and blue phosphorus n-MOSFET and p-MOSFET, Journal of Computational Electronics, Vol. 15(3), pp. 919--930 (2016)
Abstract    BibTeX    DOI: 10.1007/s10825-016-0846-x   
Abstract: In this work, we present a comput ational study on the possibility of strain engineering in monolayer Black Phosphorus (black P) and Blue Phosph orus (blue P) based MOSFETs. The material properties like band structure, carrier effective masses, carrier densities at band extrema are evaluated using Generalized Gradient Approximation (GGA) in Density Functional Theory (DFT). Thereafter self-consistent Non-Equilibrium Green's Function (NEGF) simulations are carried out to study the device performance metrics (such as output characteristics, ON currents, transconductance etc.) of such strained blac k P and blue P based MOSFETs. Our simulations show that carrier effective masses in blue P are more sensitive to strain applied in both zigzag and armchair directions. Blue P is more responsive in strain engineering for n-MOS and p-MOS. Except for black P based FETs with strain in armc hair direction, overall the blue P (black P) n- MOSFET (p-MOSFET) show moderate to signific ant improvement in performance with tensile (compressive) strain in the transport directions
BibTeX:
@article{Banerjee2016,
   title = {Performance analysis of uniaxially strained monolayer black phosphorus and blue phosphorus n-MOSFET and p-MOSFET},
   author = {Banerjee, L. and Mukhopadhyay, A. and Sengupta, A. and Rahaman, H.},
  
   journal = {Journal of Computational Electronics},
  
  
   volume = {15},
   number = {3},
   pages = {919--930},
   year = {2016},
   keywords = {Black phosphorus,Blue phosphorus,Density functional theory (DFT),MOSFET,Nonequilibrium Green's function (NEGF),Strain,area:2dmat},
   area = {2dmat}
   doi = {10.1007/s10825-016-0846-x},
  
}
Qiaoliang Bao, Zhisong Lu, Jun Li, Kian Ping Loh & Chang Ming Li, Theoretical and Experimental Studies of Electronic Transport of Dithienothiophene, The Journal of Physical Chemistry C, Vol. 113(28), pp. 12530--12537 (2009)
Abstract    BibTeX    DOI: 10.1021/jp902804f   
Abstract: Electronic transport through metal-dithieno[3,2-b:2',3'-d]thiophene (DTT) junctions with two interface geometries were studied experimentally by conducting probe atomic force microscopy on a self-assembled monolayer of DTT sandwiched between pairs of Au contacts and studied theoretically by using the fully self-consistent nonequilibrium Green's function combined with the density functional theory to calculate the transport current in the DTT nanostructures. The experimental and simulation results reveal a similar electrical transport nature of a steplike current-voltage (I-V) curve and negative differential resistance (NDR). The characteristics of the I-V curves were elucidated with evolution of the transmission spectra, and the dependence of transmission peaks on the spatial distribution of renormalized molecular orbitals were further analyzed. In two designed test molecular schemes, the highest occupied molecular orbital (HOMO) is mainly responsible for the transmission resonance at a lower external bias voltage, while the interface states originating from coupling between the electrode surface and DTT molecule are suggested to produce the NDR peak in an asymmetrical metal-DTT junction. The study of electronic transport of monomers at the molecular scale in this work demonstrates a new mechanistic approach to engineer and optimize organic material-based electronic devices.
BibTeX:
@article{Bao2009,
   title = {Theoretical and Experimental Studies of Electronic Transport of Dithienothiophene},
   author = {Bao, Qiaoliang and Lu, Zhisong and Li, Jun and Loh, Kian Ping and Li, Chang Ming},
  
   journal = {The Journal of Physical Chemistry C},
  
   publisher = {American Chemical Society},
   volume = {113},
   number = {28},
   pages = {12530--12537},
   year = {2009},
   keywords = {area:molecular electronics,molecular electronics},
   area = {molecular electronics}
   doi = {10.1021/jp902804f},
  
}
James Barker, Gregor Bollerhey & Jan Hamaekers, A Multilevel Approach to the Evolutionary Generation of Polycrystalline Structures, Computational Materials Science, Vol. 114 pp. 54--63 (2015)
Abstract    BibTeX    DOI: 10.1016/j.commatsci.2015.11.018   
Abstract: The Poisson–Voronoi tessellation is commonly used as an approximation to the microstructure of polycrystalline material. Although simple, this approximation fails to respect basic physical properties observed empirically, including the generally lognormal distribution of grain sizes. Stochastic approximations such as genetic algorithms can be used to adjust a Poisson–Voronoi tessellation to better reflect such a distribution. We apply techniques from multilevel optimisation to give a new approach to the evolutionary generation of polycrystalline structures, in a way that allows approximation of a target lognormal grain size distribution with unit mean and arbitrary variance. Results obtained through this method indicate almost perfect distribution fitting, show up to two orders of magnitude improvement in the number of evolutionary steps required for an acceptable fit, and suggest a reduction of the overall problem complexity from Θ(N3) to Θ(N2).
BibTeX:
@article{Barker2015,
   title = {A Multilevel Approach to the Evolutionary Generation of Polycrystalline Structures},
   author = {Barker, James and Bollerhey, Gregor and Hamaekers, Jan},
  
   journal = {Computational Materials Science},
  
  
   volume = {114},
  
   pages = {54--63},
   year = {2015},
   keywords = {Computational generation of polycrystalline struct,Genetic algorithm,Grain size distribution,Improvement of computational performance,Multilevel optimisation,area:VNL},
   area = {VNL}
   doi = {10.1016/j.commatsci.2015.11.018},
  
}
S. Barzilai, F. Tavazza & L.E. Levine, Sensitivity of gold nano-conductors to voids, substitutions, and electric field: ab initio results, Journal of Materials Science, Vol. 50(1), pp. 412--419 (2015)
Abstract    BibTeX    DOI: 10.1007/s10853-014-8600-x   
Abstract: Gold nanowires are good candidates for nano-electronics devices. A previous study has shown that the beryllium-terminated BeO (0001) surface may be a useful platform for supporting gold nano-conductors, since it preserves the nano wire configuration and does not restrict its conductivity. Here, we used ab initio simulations to determine the sensitivity of potential gold nano-conductors to the presence of point defects, O2 substitutions and to an applied perpendicular electric field, as in field effect transistors. We found that the presence of the point defects causes only small changes in the atomic bond lengths of the NW, does not alter the NW configuration, but may affect the overall conductivity. Single or double voids on the same channel reduce the conductance by 28 % at most, but when the voids arrange in a way that only one channel remains for conductance, it reduces by factor of two to ˜1 G0 (G0 = 2e 2/h). The presence of a single O2 molecule as a substitution reduces the electron availability in the neighboring Au atoms, in most cases reducing the conductance. The perpendicular electric field, which is typical for field effect transistors, affects the electron density distribution, shifts and changes the conductance spectra profile, but does not decrease the conductivity.
BibTeX:
@article{Barzilai2015,
   title = {Sensitivity of gold nano-conductors to voids, substitutions, and electric field: ab initio results},
   author = {Barzilai, S and Tavazza, F and Levine, L E},
  
   journal = {Journal of Materials Science},
  
   publisher = {Springer US},
   volume = {50},
   number = {1},
   pages = {412--419},
   year = {2015},
   keywords = {Au,area:nanowires,gold,nano conductor,nanowires},
   area = {nanowires}
   doi = {10.1007/s10853-014-8600-x},
  
}
S. Barzilai, F. Tavazza & L.E. Levine, Effect of wire configuration and point defects on the conductance of gold nano-conductors, Modelling and Simulation in Materials Science and Engineering, Vol. 22(3), pp. 35006 (2014)
Abstract    BibTeX    DOI: 10.1088/0965-0393/22/3/035006   
Abstract: Gold nanowire (NW) chains are considered a good candidate for nano-electronics devices because they exhibit remarkable structural and electrical properties. One promising nano-conductor candidate is called 'Hexa1'. It has a two-dimensional, one atom thick structure and was found to spontaneously form during simulations of gold NWs elongations. It is stable and a good conductor when adsorbed on a suitable substrate. In this study, we deepened the investigation of such a NW structure, to explore the effect of the NWs length, point defects and NW junctions on its conductance. We found that the conductance is not affected by the NW length, and that conveniently placed point defects can be used to create resistors. We also found that direction changes in circuits produce conductance bottle necks, therefore decreasing the conductance. However, this decrease can be easily overcome by adding a few atoms to the NW junction.
BibTeX:
@article{Barzilai2014,
   title = {Effect of wire configuration and point defects on the conductance of gold nano-conductors},
   author = {Barzilai, S and Tavazza, F and Levine, L E},
  
   journal = {Modelling and Simulation in Materials Science and Engineering},
  
  
   volume = {22},
   number = {3},
   pages = {35006},
   year = {2014},
   keywords = {ab initio calculations,area:nanowires,conductance,gold nanowire,junction},
   area = {nanowires}
   doi = {10.1088/0965-0393/22/3/035006},
  
}
S. Barzilai, F. Tavazza & L.E. Levine, Ab initio study of the mechanical and transport properties of pure and contaminated silver nanowires, Journal of Physics: Condensed Matter, Vol. 25(32), pp. 325303 (2013)
Abstract    BibTeX    DOI: 10.1088/0953-8984/25/32/325303   
Abstract: The mechanical properties and conductance of contaminated and pure silver nanowires were studied using density functional theory (DFT) calculations. Several nanowires containing O 2 on their surfaces were elongated along two different directions. All of the NWs thinned down to single atom chains. In most simulations, the breaking force was not affected by the presence of the O 2 , and similar fracture strengths of ˜1nN were computed for the pure and impure NWs. When the O 2 became incorporated in the single atom chain, the fracture occurred at the Ag-O bond and a lower fracture strength was found. All of the simulations showed that the impurity interacted with the silver atoms to reduce the electron density in its nearby vicinity. A variety of conductance effects were observed depending on the location of the impurity. When the impurity migrated during the elongation to the thinnest part of the NW, it reduced the conductance significantly, and an ˜1 G0 conductance (usually associated with a single atom chain) was calculated for three- and two-dimensional structures. When the impurity was adjacent to the single atom chain, the conductance reduced almost to zero. However, when it stayed far from the thinnest part of the NW, the impurity had only a small influence on the conductance.
BibTeX:
@article{Barzilai2013c,
   title = {Ab initio study of the mechanical and transport properties of pure and contaminated silver nanowires},
   author = {Barzilai, S and Tavazza, F and Levine, L E},
  
   journal = {Journal of Physics: Condensed Matter},
  
  
   volume = {25},
   number = {32},
   pages = {325303},
   year = {2013},
   keywords = {area:nanowires,conductance,deformation,failure,geometry optimization,gold nanowires,impurities,mechanical properties,molecules,nanowires},
   area = {nanowires}
   doi = {10.1088/0953-8984/25/32/325303},
  
}
S. Barzilai, F. Tavazza & L.E. Levine, Disparate effects of an O2 internal impurity on the elongation and quantum transport of gold and silver nanowires, Journal of Applied Physics, Vol. 114(7), pp. 74315 (2013)
Abstract    BibTeX    DOI: 10.1063/1.4818956   
Abstract: In this work, we investigated the effects of an internal O2 impurity on the conductance of elongated gold and silver nanowires (NWs) using density functional theory calculations. We found that the O2 interacts with these metallic NWs very differently. In the case of gold NWs, the presence of an internal oxygen molecule locally strengthens the wire, therefore, forcing the phase transformations connected to the thinning process (3D to 2D and 2D to single atom chain) to occur far from the oxygen. As a consequence, towards the end of the elongation, the internal O2 is located far from the main conductance channel and therefore has little influence on the conductance of the NW. In contrast, in silver NWs, the presence of an internal oxygen molecule involves a larger charge transfer from the metallic atoms to the oxygen, therefore, weakening the Ag-Ag binding. During the initial stages of the elongation, several metallic bonds adjacent to the impurity break, so that in most simulations the NW thinning takes place near the O2. This thinning mechanism places the O2 near the main conductance channel, therefore, significantly reducing the conductivity of the elongated silver NWs. For both metals, our findings agree well with the published experimental results.
BibTeX:
@article{Barzilai2013d,
   title = {Disparate effects of an O2 internal impurity on the elongation and quantum transport of gold and silver nanowires},
   author = {Barzilai, S and Tavazza, F and Levine, L E},
  
   journal = {Journal of Applied Physics},
  
  
   volume = {114},
   number = {7},
   pages = {74315},
   year = {2013},
   keywords = {area:nanowires,conductance,electric admittance,geometry optimization,impurities,mechanical properties,molecules,nanowires},
   area = {nanowires}
   doi = {10.1063/1.4818956},
  
}
S. Barzilai, F. Tavazza & L.E. Levine, First-principle modeling of gold adsorption on BeO (0001), Surface Science, Vol. 609(0), pp. 39--43 (2013)
Abstract    BibTeX    DOI: 10.1016/j.susc.2012.10.017   
Abstract: Gold nanowire chains are considered a good candidate for nanoelectronic devices since they exhibit remarkable structural and electrical properties. For practical engineering devices, alpha-wurtzite BeO may be a useful platform for supporting these nanowires, since the atom separation of the BeO (0001) surface is compatible with the Au-Au atom spacing. However, its influence on the nanowire conductivity is unknown. Here, ab initio simulations of adsorption of one gold atom on cleaved BeO (0001) surfaces have been performed to find the most favorable adsorption site. An attractive adsorption was obtained for all the studied sites, but the most favorable site was above the oxygen for the O-terminated surface and above the Be-Be bridge for the Be-terminated surface. A relatively high electron density is observed in the AuO and AuBe bonds, and the local density of states exhibits high peaks in the vicinity of the Fermi energy.
BibTeX:
@article{Barzilai2013a,
   title = {First-principle modeling of gold adsorption on BeO (0001)},
   author = {Barzilai, S and Tavazza, F and Levine, L E},
  
   journal = {Surface Science},
  
  
   volume = {609},
   number = {0},
   pages = {39--43},
   year = {2013},
   keywords = {BeO,ab initio calculations,adsorption,area:nanowires,band-structure,chains,conductance,geometry optimization,molecules,oxide,substrate,surfaces},
   area = {nanowires}
   doi = {10.1016/j.susc.2012.10.017},
  
}
S. Barzilai, F. Tavazza & L.E. Levine, Sensitivity of gold nano-conductors to common contaminations: ab initio results, Journal of Materials Science, Vol. 48(19), pp. 6619--6624 (2013)
Abstract    BibTeX    DOI: 10.1007/s10853-013-7460-0   
Abstract: Gold nanowire chains are considered a good candidate for nanoelectronic devices because they exhibit remarkable structural and electrical properties. A previous study shows that the beryllium-terminated BeO (0001) surface may be a useful platform for supporting nano gold conductors, since it preserves the nano-wire configuration, does not restrict its conductivity, and even enhances it. However, the influence of contamination on the conductivity of such conductors is unknown. Here, ab initio simulations were performed to determine the effect of commonly adsorbed contaminants (H2O and O2) on the conductivity of gold nano-conductors. We found that the presence of adsorbed impurities does not alter the good conductive ability of the conductors under examination.
BibTeX:
@article{Barzilai2013b,
   title = {Sensitivity of gold nano-conductors to common contaminations: ab initio results},
   author = {Barzilai, S and Tavazza, F and Levine, L E},
  
   journal = {Journal of Materials Science},
  
   publisher = {Springer US},
   volume = {48},
   number = {19},
   pages = {6619--6624},
   year = {2013},
   keywords = {area:nanowires,ballistic conductance,impurities,metallic nanowire},
   area = {nanowires}
   doi = {10.1007/s10853-013-7460-0},
  
}
S. Barzilai, F. Tavazza & L.E. Levine, Structure stability and electronic transport of gold nanowires on a BeO (001) surface, Modelling and Simulation in Materials Science and Engineering, Vol. 21(7), pp. 75003 (2013)
Abstract    BibTeX    DOI: 10.1088/0965-0393/21/7/075003   
Abstract: Gold nanowires (NWs) exhibit remarkable structural and electrical properties, making them good candidates for practical nanoelectronic devices. For such engineering applications, alpha-wurtzite BeO may be a useful platform for supporting these NWs, because gold atoms are attracted to this surface and the atom separation of the BeO (001) surface is compatible with the Au-Au atom spacing. However, the influence of this substrate on the NW conductivity and structure is not known. Here, the stability and conductance of several Au NW configurations on BeO (001) surfaces are investigated using ab initio simulations. It was found that the beryllium-terminated surface preserves the configuration for most of the NWs while the oxygen-terminated surface changes and even repels most of the NW configurations. The electronic structure and the transmission properties of the stable cases showed small changes in the electronic structure of gold NWs due to the presence of the BeO substrate. These changes do not restrict the conduction of the NWs and even enhance it by increasing the capacity of the existing transmission channels, and forming new conduction paths.
BibTeX:
@article{Barzilai2013e,
   title = {Structure stability and electronic transport of gold nanowires on a BeO (001) surface},
   author = {Barzilai, S and Tavazza, F and Levine, L E},
  
   journal = {Modelling and Simulation in Materials Science and Engineering},
  
  
   volume = {21},
   number = {7},
   pages = {75003},
   year = {2013},
   keywords = {BeO substrate,adsorption,area:nanowires,band structure,chains,conductance,geometry optimization,junctions,molecules,nanowires,structural stability,transmission pathways},
   area = {nanowires}
   doi = {10.1088/0965-0393/21/7/075003},
  
}
S. Barzilai, F. Tavazza & L.E. Levine, The effect of internal impurities on the mechanical and conductance properties of gold nanowires during elongation, Modelling and Simulation in Materials Science and Engineering, Vol. 21(2), pp. 025004---- (2013)
Abstract    BibTeX    DOI: 10.1088/0965-0393/21/2/025004   
Abstract: The conductance and mechanical properties of contaminated gold nanowires (NWs) were studied using first principle calculations. Nanowires containing internal impurities of H 2 O or O 2 were elongated along two different directions. It was found that both impurities interact with the gold atoms and affect the properties of the NWs. From a mechanical viewpoint, the impurities increase the bond strength in their vicinity and, throughout the entire elongation, remain surrounded by gold atoms. The impurities do not migrate to the surface and never end up in the single atom chain. The NW fracture always occurs at an Au-Au bond, far from the impurity. Therefore, the impurities do not affect the fracture strength but do decrease the strain at fracture. A variety of conductance effects were observed depending on the type and location of the impurity, and the O 2 has the most significant impact. The O 2 reduces the conductance when it is close to the gold atoms in the main pathway. However, at the late stages of the elongation, both impurities are located far from the main pathway and have little influence on the conductance.
BibTeX:
@article{Barzilai2013,
   title = {The effect of internal impurities on the mechanical and conductance properties of gold nanowires during elongation},
   author = {Barzilai, S and Tavazza, F and Levine, L E},
  
   journal = {Modelling and Simulation in Materials Science and Engineering},
  
  
   volume = {21},
   number = {2},
   pages = {025004----},
   year = {2013},
   keywords = {area:nanowires,atomic wire,defects,deformation,mechanical properties,nanowire,plasticity,quantum wire,structural failure},
   area = {nanowires}
   doi = {10.1088/0965-0393/21/2/025004},
  
}
Anirban Basak, S.K. Manhas, Gaurav Kapil, Sudeb Dasgupta & Neeraj Jain, A Simulation Study of the Effect of Platinum Contact on CNT Based Gas Sensors Using Self-Consistent Field with NEGF Method, pp. 169--172 (2012)
Abstract    BibTeX    URL: https://www.researchgate.net/publication/274835334   
Abstract: The electronic structure of the pi electrons of the CNT is highly affected by the presence of foreign molecules. This property can be utilized in CNT based gas sensing applications. In this work, we study bare zigzag CNT, NO2 adsorbed zigzag CNT, and Pt contacted NO2 adsorbed zigzag CNT to find the effectiveness of zigzag CNT and Pt in making a NO2 gas sensor. We find that bare zigzag CNT is a good material for NO2 detection and platinum make Schottky contact with zigzag CNT which can be used for gas sensing applications.
BibTeX:
@inproceedings{Basak2012,
   title = {A Simulation Study of the Effect of Platinum Contact on CNT Based Gas Sensors Using Self-Consistent Field with NEGF Method},
   author = {Basak, Anirban and Manhas, S K and Kapil, Gaurav and Dasgupta, Sudeb and Jain, Neeraj},
   booktitle = {SISPAD},
  
  
  
  
  
   pages = {169--172},
   year = {2012},
   keywords = {area:nanotubes,nanotube,sensor},
   area = {nanotubes}
  
   url = {https://www.researchgate.net/publication/274835334},
}
H. Basch, R. Cohen & M.A. Ratner, Interface geometry and molecular junction conductance: Geometric fluctuation and stochastic switching, Nano Letters, Vol. 5(9), pp. 1668--1675 (2005)
Abstract    BibTeX    DOI: 10.1021/nl050702s   
Abstract: Metal/molecule/metal transport junctions can transport charge in the elastic scattering (Landauer) regime if the injection gap is large and the molecule is relatively short. Stochastic switching and broad conduction peak distributions have been observed in such junctions. We examine the effect of altering interface geometry on transport, using density functional calculations. For most structures, variations in conductance of order 0-300% are found, but when an atomic wire of Au binds to the molecule, symmetry changes can modify currents by a factor of 10ˆ3.
BibTeX:
@article{Basch2005,
   title = {Interface geometry and molecular junction conductance: Geometric fluctuation and stochastic switching},
   author = {Basch, H and Cohen, R and Ratner, M A},
  
   journal = {Nano Letters},
  
  
   volume = {5},
   number = {9},
   pages = {1668--1675},
   year = {2005},
   keywords = {TranSIESTA-C,area:molecular electronics,molecular electronics},
   area = {molecular electronics}
   doi = {10.1021/nl050702s},
  
}
Golibjon R. Berdiyorov, Optical properties of functionalized Ti3C2T2 (T = F, O, OH) MXene: First-principles calculations, AIP Advances, Vol. 6(5), pp. 055105 (2016)
Abstract    BibTeX    DOI: 10.1063/1.4948799   
Abstract: Role of surface termination on the dielectric and optical properties of Ti3C2T2 (T = F, O, OH) MXene is studied using first-principles density functional theory. The results show that the surface functionalization has a significant impact on the optical properties of the MXene. For example, in the visible range of the spectrum, the oxidized sample shows larger absorption, whereas surface fluorination results in weaker absorption as compared to pristine MXene. In the ultraviolet energy range, all functional groups lead to the enhancement of both absorption and reflectivity of the material. Dielectric properties of MXene are also sensitive to the surface functionalization. Our findings demonstrate the importance of surface termination on the optical properties of the MXene.
BibTeX:
@article{Berdiyorov2016j,
   title = {Optical properties of functionalized Ti3C2T2 (T = F, O, OH) MXene: First-principles calculations},
   author = {Berdiyorov, Golibjon R.},
  
   journal = {AIP Advances},
  
  
   volume = {6},
   number = {5},
   pages = {055105},
   year = {2016},
   keywords = {Absorption spectra,MXenes,Materials properties,Optical properties,Photons,Reflectivity,area:2dmat,grimme},
   area = {2dmat}
   doi = {10.1063/1.4948799},
  
}
Golibjon R. Berdiyorov, Effect of lithium and sodium ion adsorption on the electronic transport properties of Ti3C2 MXene, Applied Surface Science, Vol. 359 pp. 153--157 (2015)
Abstract    BibTeX    DOI: 10.1016/j.apsusc.2015.10.050   
Abstract: MXenes are found to be promising electrode materials for energy storage applications. Recent theoretical and experimental studies indicate the possibility of using these novel low dimensional materials for metal-ion batteries. Herein, we use density-functional theory in combination with the nonequilibrium Green's function formalism to study the effect of lithium and sodium ion adsorption on the electronic transport properties of the MXene, Ti3C2. Oxygen, hydroxyl and fluorine terminated species are considered and the obtained results are compared with the ones for the pristine MXene. We found that the ion adsorption results in reduced electronic transport in the pristine MXene: depending on the type of the ions and the bias voltage, the current in the system can be reduced by more than 30%. On the other hand, transport properties of the oxygen terminated sample can be improved by the ion adsorption: for both types of ions the current in the system can be increased by more than a factor of 4. However, the electronic transport is less affected by the ions in fluorinated and hydroxylated samples. These two samples show enhanced electronic transport as compared to the pristine MXene. The obtained results are explained in terms of electron localization in the system.
BibTeX:
@article{Berdiyorov2015,
   title = {Effect of lithium and sodium ion adsorption on the electronic transport properties of Ti3C2 MXene},
   author = {Berdiyorov, Golibjon R.},
  
   journal = {Applied Surface Science},
  
   publisher = {Elsevier B.V.},
   volume = {359},
  
   pages = {153--157},
   year = {2015},
   keywords = {DFT,Electronic transport,MXenes,area:2dmat},
   area = {2dmat}
   doi = {10.1016/j.apsusc.2015.10.050},
  
}
Golibjon R. Berdiyorov, Effect of surface functionalization on the electronic transport properties of Ti 3 C 2 MXene, EPL (Europhysics Letters), Vol. 111(6), pp. 67002 (2015)
Abstract    BibTeX    DOI: 10.1209/0295-5075/111/67002   
Abstract: The effects of surface functionalization on the electronic transport properties of the MXene compound Ti3C2 are studied using density-functional theory in combination with the nonequilibrium Green's function formalism. Fluorinated, oxidized and hydroxylated surfaces are considered and the obtained results are compared with the ones for the pristine MXene. It is found that the surface termination has a considerable impact on the electronic transport in MXene. For example, the fluorinated sample shows the largest transmission, whereas surface oxidation results in a considerable reduction of the electronic transmission. The current in the former sample can be up to 4 times larger for a given bias voltage as compared to the case of bare MXene. The increased transmission originates from the extended electronic states and smaller variations of the electrostatic potential profile. Our findings can be useful in designing MXene-based anode materials for energy storage applications, where enhanced electronic transport will be an asset.
BibTeX:
@article{Berdiyorov2015c,
   title = {Effect of surface functionalization on the electronic transport properties of Ti 3 C 2 MXene},
   author = {Berdiyorov, Golibjon R.},
  
   journal = {EPL (Europhysics Letters)},
  
  
   volume = {111},
   number = {6},
   pages = {67002},
   year = {2015},
   keywords = {2-DIMENSIONAL TITANIUM CARBIDE,ANODE,HIGH VOLUMETRIC CAPACITANCE,INTERCALATION,LITHIUM-ION BATTERIES,TRANSITION-METAL CARBIDES,area:2dmat},
   area = {2dmat}
   doi = {10.1209/0295-5075/111/67002},
  
}
Golibjon R. Berdiyorov, H. Bahlouli & F.M. Peeters, Effect of substitutional impurities on the electronic transport properties of graphene, Physica E: Low-dimensional Systems and Nanostructures, Vol. 84 pp. 22--26 (2016)
Abstract    BibTeX    DOI: 10.1016/j.physe.2016.05.024   
Abstract: Density-functional theory in combination with the nonequilibrium Green's function formalism is used to study the effect of substitutional doping on the electronic transport properties of hydrogen passivated zig-zag graphene nanoribbon devices. B, N and Si atoms are used to substitute carbon atoms located at the center or at the edge of the sample. We found that Si-doping results in better electronic transport as compared to the other substitutions. The transmission spectrum also depends on the location of the substitutional dopants: for single atom doping the largest transmission is obtained for edge substitutions, whereas substitutions in the middle of the sample give larger transmission for double carbon substitutions. The obtained results are explained in terms of electron localization in the system due to the presence of impurities.
BibTeX:
@article{Berdiyorov2016h,
   title = {Effect of substitutional impurities on the electronic transport properties of graphene},
   author = {Berdiyorov, Golibjon R. and Bahlouli, H. and Peeters, F. M.},
  
   journal = {Physica E: Low-dimensional Systems and Nanostructures},
  
   publisher = {Elsevier},
   volume = {84},
  
   pages = {22--26},
   year = {2016},
   keywords = {Density functional,Doping,Graphene,Transmission,area:graphene},
   area = {graphene}
   doi = {10.1016/j.physe.2016.05.024},
  
}
Golibjon R. Berdiyorov, H. Bahlouli & F.M. Peeters, Theoretical study of electronic transport properties of a graphene-silicene bilayer, Journal of Applied Physics, Vol. 117(22), pp. 225101 (2015)
Abstract    BibTeX    DOI: 10.1063/1.4921877   
Abstract: Electronic transport properties of a graphene-silicene bilayer system are studied using density-functional theory in combination with the nonequilibrium Green's function formalism. Depending on the energy of the electrons, the transmission can be larger in this system as compared to the sum of the transmissions of separated graphene and silicene monolayers. This effect is related to the increased electron density of states in the bilayer sample. At some energies, the electronic states become localized in one of the layers, resulting in the suppression of the electron transmission. The effect of an applied voltage on the transmission becomes more pronounced in the layered sample as compared to graphene due to the larger variation of the electrostatic potential profile. Our findings will be useful when creating hybrid nanoscale devices where enhanced transport properties will be desirable.
BibTeX:
@article{Berdiyorov2015a,
   title = {Theoretical study of electronic transport properties of a graphene-silicene bilayer},
   author = {Berdiyorov, Golibjon R. and Bahlouli, H. and Peeters, F. M.},
  
   journal = {Journal of Applied Physics},
  
  
   volume = {117},
   number = {22},
   pages = {225101},
   year = {2015},
   keywords = {Density functional theory,Fermi levels,Graphene,Silicon,Transport properties,area:graphene,area:interfaces},
   area = {graphene,interfaces}
   doi = {10.1063/1.4921877},
  
}
Golibjon R. Berdiyorov, Fedwa El-mellouhi, M.E. Madjet, F.H. Alharbi, F.M. Peeters & S. Kais, Effect of halide-mixing on the electronic transport properties of organometallic perovskites, Solar Energy Materials and Solar Cells, Vol. 148 pp. 2--10 (2016)
Abstract    BibTeX    DOI: 10.1016/j.solmat.2015.11.023   
Abstract: Using density-functional theory in combination with the nonequilibrium Green's function formalism, we study the effect of iodide/chloride and iodide/bromide mixing on the electronic transport in lead based organometallic perovskite CH3NH3PbI3, which is known to be an effective tool to tune the electronic and optical properties of such materials. We found that depending on the level and position of the halide-mixing, the electronic transport can be increased by more than a factor of 4 for a given voltage biasing. The largest current is observed for small concentration of bromide substitutions located at the equatorial sites. However, full halide substitution has a negative effect on the transport properties of this material: the current drops by an order of magnitude for both CH3NH3PbCl3 and CH3NH3PbBr3 samples.
BibTeX:
@article{Berdiyorov2016e,
   title = {Effect of halide-mixing on the electronic transport properties of organometallic perovskites},
   author = {Berdiyorov, Golibjon R. and El-mellouhi, Fedwa and Madjet, M. E. and Alharbi, F. H. and Peeters, F. M. and Kais, S.},
  
   journal = {Solar Energy Materials and Solar Cells},
  
   publisher = {Elsevier},
   volume = {148},
  
   pages = {2--10},
   year = {2016},
   keywords = {Density functional theory,Electronic transport,Green's functions,Hybrid perovskite,area:interfaces},
   area = {interfaces}
   doi = {10.1016/j.solmat.2015.11.023},
  
}
Golibjon R. Berdiyorov, Fedwa El-Mellouhi, M.E. Madjet, F.H. Alharbi & S.N. Rashkeev, Electronic transport in organometallic perovskite CH3NH3PbI3: The role of organic cation orientations, Applied Physics Letters, Vol. 108(5), pp. 053901 (2016)
Abstract    BibTeX    DOI: 10.1063/1.4941296   
Abstract: Density functional theory in combination with the nonequilibrium Green's function formalism is used to study the electronic transport properties of methylammonium lead-iodide perovskite CH3NH3PbI3. Electronic transport in homogeneous ferroelectric and antiferroelectric phases, both of which do not contain any chargeddomain walls, is quite similar. The presence of chargeddomain wall drastically (by about an order of magnitude) enhances the electronic transport in the lateral direction. The increase of the transmission originates from the smaller variation of the electrostatic potential profile along the chargeddomain walls. This fact may provide a tool for tuning transport properties of such hybrid materials by manipulating molecular cations having dipole moment.
BibTeX:
@article{Berdiyorov2016l,
   title = {Electronic transport in organometallic perovskite CH3NH3PbI3: The role of organic cation orientations},
   author = {Berdiyorov, Golibjon R. and El-Mellouhi, Fedwa and Madjet, M. E. and Alharbi, F. H. and Rashkeev, S. N.},
  
   journal = {Applied Physics Letters},
  
  
   volume = {108},
   number = {5},
   pages = {053901},
   year = {2016},
   keywords = {Charge carriers,Dielectric oxides,Domain walls,Materials properties,Transport properties,area:interfaces,perovskites},
   area = {interfaces}
   doi = {10.1063/1.4941296},
  
}
Golibjon R. Berdiyorov, K. Harrabi, U. Mehmood, F.M. Peeters, N. Tabet, J. Zhang, I.A. Hussein & M.A. McLachlan, Derivatization and diffusive motion of molecular fullerenes: Ab initio and atomistic simulations, Journal of Applied Physics, Vol. 118(2), pp. 025101 (2015)
Abstract    BibTeX    DOI: 10.1063/1.4923352   
Abstract: Using first principles density functional theory in combination with the nonequilibrium Green's function formalism, we study the effect of derivatization on the electronic and transport properties of C60backslashrbackslashnfullerene. As a typical example, we consider [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), which forms one of the most efficient organic photovoltaic materials in combination with electron donating polymers. Extra peaks are observed in the density of states (DOS) due to the formation of new electronic states localized at/near the attached molecule. Despite such peculiar behavior in the DOS of an isolated molecule, derivatization does not have a pronounced effect on the electronic transport properties of the fullerene molecular junctions. Both C60 and PCBM show the same response to finite voltage biasing with new features in the transmission spectrum due to voltage induced delocalization of some electronic states. We also study the diffusive motion of molecular fullerenes in ethanolbackslashrbackslashnsolvent and inside poly(3-hexylthiophene) lamella using reactive molecular dynamics simulations. We found that the mobility of the fullerene reduces considerably due to derivatization; the diffusion coefficient of C60 is an order of magnitude larger than the one for PCBM.
BibTeX:
@article{Berdiyorov2015b,
   title = {Derivatization and diffusive motion of molecular fullerenes: Ab initio and atomistic simulations},
   author = {Berdiyorov, Golibjon R. and Harrabi, K. and Mehmood, U. and Peeters, F. M. and Tabet, N. and Zhang, J. and Hussein, I. A. and McLachlan, M. A.},
  
   journal = {Journal of Applied Physics},
  
  
   volume = {118},
   number = {2},
   pages = {025101},
   year = {2015},
   keywords = {Diffusion,Ethanol,Fullerenes,Solvents,Transport properties,area:molecular electronics},
   area = {molecular electronics}
   doi = {10.1063/1.4923352},
  
}
Golibjon R. Berdiyorov, Ali Kachmar, Fedwa El-Mellouhi, Marcelo A. Carignano & Mohamed El-Amine Madjet, Role of Cations on the Electronic Transport and Optical Properties of Lead-Iodide Perovskites, The Journal of Physical Chemistry C, Vol. 120(30), pp. 16259--16270 (2016)
Abstract    BibTeX    DOI: 10.1021/acs.jpcc.6b01818   
Abstract: Using density functional theory in combination with the nonequilibrium Green's function formalism we study the role of organic (methylammonium, MA) and inorganic (cesium, Cs) cations on the electronic transport and optical properties of single crystal lead-iodide perovskite. Both dispersive interactions (i.e., van der Waals interactions) and spin–orbit coupling are taken into account in describing the properties of the considered systems. Despite sizable difference in the lattice parameters and the electric polarization of the system, both MAPbI3 and CsPbI3 show similar electronic transport properties. A small difference in the transmission originates from the variations of the electrostatic potential along the electronic transport direction. These two samples also exhibit similar optical and dielectric properties when they are in the same crystalline phase. Our finite temperature first-principles molecular dynamics simulations in combination with static density functional theory calculations also reveal ...
BibTeX:
@article{Berdiyorov2016g,
   title = {Role of Cations on the Electronic Transport and Optical Properties of Lead-Iodide Perovskites},
   author = {Berdiyorov, Golibjon R. and Kachmar, Ali and El-Mellouhi, Fedwa and Carignano, Marcelo A. and El-Amine Madjet, Mohamed},
  
   journal = {The Journal of Physical Chemistry C},
  
  
   volume = {120},
   number = {30},
   pages = {16259--16270},
   year = {2016},
   keywords = {area:interfaces,perovskites},
   area = {interfaces}
   doi = {10.1021/acs.jpcc.6b01818},
  
}
Golibjon R. Berdiyorov & M.E. Madjet, Structural, electronic transport and optical properties of functionalized quasi-2D TiC2 from first-principles calculations, Applied Surface Science, Vol. 390 pp. 1009--1014 (2016)
Abstract    BibTeX    DOI: 10.1016/j.apsusc.2016.08.179   
Abstract: Using the first-principles density functional theory, we study the effect of surface functionalization on the structural and optoelectronic properties of recently proposed quasi-two-dimensional material TiC2 [T. Zhao, S. Zhang, Y. Guo, Q. Wang, Nanoscale 8 (2016) 233]. Hydrogenated, fluorinated, oxidized and hydroxylated surfaces are considered. Significant changes in the lattice parameters and partial charge distributions are found due to the surface termination. Direct contribution of the adatoms to the system density of states near the Fermi level is obtained, which has a major impact on the optoelectronic properties of the material. For example, surface termination results in larger absorption in the visible range of the spectrum. The electronic transport is also affected by the surface functionalization: the current in the system can be reduced by an order of magnitude. These findings indicate the importance of the effects of surface passivation on optoelectronic properties of this quasi-2D material.
BibTeX:
@article{Berdiyorov2016f,
   title = {Structural, electronic transport and optical properties of functionalized quasi-2D TiC2 from first-principles calculations},
   author = {Berdiyorov, Golibjon R. and Madjet, M. E.},
  
   journal = {Applied Surface Science},
  
   publisher = {Elsevier B.V.},
   volume = {390},
  
   pages = {1009--1014},
   year = {2016},
   keywords = {Optical properties,area:2dmat,density functional theory,electronic transport,surface functionalization},
   area = {2dmat}
   doi = {10.1016/j.apsusc.2016.08.179},
  
}
Golibjon R. Berdiyorov, Mohamed E. Madjet & Khaled A. Mahmoud, Ionic sieving through Ti3C2(OH)2 MXene: First-principles calculations, Applied Physics Letters, Vol. 108(11), pp. 113110 (2016)
Abstract    BibTeX    DOI: 10.1063/1.4944393   
Abstract: Recent experiments revealed a great potential of MXene nanosheets for water desalination applications as ultrathin, high-flux, and size/charge-selective sieving membranes. Here, we conduct first-principles density functional theory calculations to explore possible mechanisms for the charge-selective ionic transport through Ti3C2(OH)2 MXene. We find that the charge selectivity originates from the charged nature of the MXene layers. For example, due to the electrostatic interactions, ions of different charge states have different energy barriers for the intercalation between the MXene layers. In addition, the system shows dynamic response to the intercalating ions, even in their hydrated states, by changing the interlayer spacing. Our findings highlight the importance of membranesurfacecharges on the ion sieving performance.
BibTeX:
@article{Berdiyorov2016k,
   title = {Ionic sieving through Ti3C2(OH)2 MXene: First-principles calculations},
   author = {Berdiyorov, Golibjon R. and Madjet, Mohamed E. and Mahmoud, Khaled A.},
  
   journal = {Applied Physics Letters},
  
  
   volume = {108},
   number = {11},
   pages = {113110},
   year = {2016},
   keywords = {Density functional theory,Double layers,Electrostatics,MXenes,Sodium,Surface charge,area:interfaces,area:materials},
   area = {interfaces,materials}
   doi = {10.1063/1.4944393},
  
}
Golibjon R. Berdiyorov & Mohamed El-Amine Madjet, First-principles study of electronic transport and optical properties of penta-graphene, penta-SiC 2 and penta-CN 2, RSC Adv., Vol. 6(56), pp. 50867--50873 (2016)
Abstract    BibTeX    DOI: 10.1039/C6RA10376F   
Abstract: Using density functional theory in combination with the nonequilibrium Green's function formalism we study the electronic transport properties, optical properties and atomic partial charges of the recently proposed isostructural materials: penta-graphene (PG), pentagonal silicon dicarbide (p-SiC2) and pentagonal carbon nitride (p-CN2). Enhanced electronic transport is obtained in p-SiC2 as compared to PG due to the delocalization of the electronic states and smaller variations of the electrostatic potential. This enhancement occurs despite a smaller contribution of Si atoms to the density of states of the system. Penta-SiC2 also displays improved dielectric and optical properties as compared to its all-carbon analogue. For example, larger absorption is obtained in both the visible and the ultraviolet spectral ranges. Strong variation in the atomic partial charge distribution was found in p-SiC2. On the contrary, p-CN2 was not found to exhibit improved optoelectronic properties compared to PG, except for larger partial charges on the surface of the sample. Our findings demonstrate the potential of p-SiC2 in optoelectronic applications.
BibTeX:
@article{Berdiyorov2016i,
   title = {First-principles study of electronic transport and optical properties of penta-graphene, penta-SiC 2 and penta-CN 2},
   author = {Berdiyorov, Golibjon R. and Madjet, Mohamed El-Amine},
  
   journal = {RSC Adv.},
  
   publisher = {Royal Society of Chemistry},
   volume = {6},
   number = {56},
   pages = {50867--50873},
   year = {2016},
   keywords = {area:2dmat,penta-graphene},
   area = {2dmat}
   doi = {10.1039/C6RA10376F},
  
}
Golibjon R. Berdiyorov, M.V. Milosevic, F.M. Peeters & Adri C.T. van Duin, Stability of CH3 molecules trapped on hydrogenated sites of graphene, Physica B: Condensed Matter, Vol. 455 pp. 60--65 (2014)
Abstract    BibTeX    DOI: 10.1016/j.physb.2014.07.046   
Abstract: We study the effect of a hydrogen atom on the thermal stability of a trapped CH3 molecule on graphene using ReaxFF molecular dynamics simulations. Due to the hydrogen-molecule interaction, enhanced pinning of the CH3 molecule is observed when it is positioned adjacent to the graphene site with the hydrogen atom. We discuss the formation process of such a stable configuration, which originates from different adhesion and migration energies of the hydrogen atom and the CH3 molecule. We also studied the effect of the CH3-H configuration on the electronic transport properties of graphene nanoribbons using first principles density-functional calculations. We found that the formation of the CH3-H structure results in extra features in the transmission spectrum due to the formation of strongly localized states, which are absent when the CH3 molecule is trapped on pristine graphene. Our findings will be useful in exploiting gas sensing properties of graphene, especially for selective detection of individual molecules.
BibTeX:
@article{Berdiyorov2014,
   title = {Stability of CH3 molecules trapped on hydrogenated sites of graphene},
   author = {Berdiyorov, Golibjon R. and Milosevic, M V and Peeters, F. M. and van Duin, Adri C T},
  
   journal = {Physica B: Condensed Matter},
  
  
   volume = {455},
  
   pages = {60--65},
   year = {2014},
   keywords = {Electronic transport,Graphene,Molecular dynamics,area:graphene},
   area = {graphene}
   doi = {10.1016/j.physb.2014.07.046},
  
}
Justin P. Bergfield, Henry M. Heitzer, Colin Van Dyck, Tobin J. Marks & Mark A. Ratner, Harnessing Quantum Interference in Molecular Dielectric Materials, ACS nano, Vol. 9(6), pp. 6412--6418 (2015)
Abstract    BibTeX    DOI: 10.1021/acsnano.5b02042   
Abstract: We investigate the relationship between dielectric response and charge transport in molecule-based materials operating in the quantum coherent regime. We find that quantum interference affects these observ- ables differently, for instance, allowing current passing through certain materials to be reduced by orders of magnitude without affecting dielectric behavior (or band gap). As an example, we utilize ab initio electronic structure theory to calculate conductance and dielectric constants of cross-conjugated anthraquinone (AQ)-based and linearly conjugated anthracene (AC)-based materials. In spite of having nearly equal fundamental gaps, electrode bonding configurations, and molecular dimensions, we find a ∼1.7 order of magnitude (∼50-fold) reduction in the conductance of the AQ-based material relative to the AC-based material, a value in close agreement with recent measurements, while the calculated dielectric constants of both materials are nearly identical. From these findings, we propose two molecular materials in which quantum interference is used to reduce leakage currents across a ∼25 Å monolayer gap with dielectric constants larger than 4.5.
BibTeX:
@article{Bergfield2015,
   title = {Harnessing Quantum Interference in Molecular Dielectric Materials},
   author = {Bergfield, Justin P and Heitzer, Henry M and Dyck, Colin Van and Marks, Tobin J and Ratner, Mark A},
  
   journal = {ACS nano},
  
  
   volume = {9},
   number = {6},
   pages = {6412--6418},
   year = {2015},
   keywords = {CONDUCTANCE,CROSS-CONJUGATED MOLECULES,DENSITY,ELECTRON-TRANSPORT,GAP,GENERALIZED GRADIENT APPROXIMATION,JUNCTIONS,PI-SYSTEM,SINGLE-MOLECULE,TRANSMISSION AMPLITUDES,area:molecular electronics,cross-conjugated polymers,currents,density functional theory,dielectric constant materials,molecular dielectric material,nonequilibrium quantum transport,quantum interference},
   area = {molecular electronics}
   doi = {10.1021/acsnano.5b02042},
  
}
M. Aruna Bharathi, K. Venkateswara Rao & M. Sushama, Synthesis, Characterization and Density Functional Study of LiMn1.5Ni0.5O4 Electrode for Lithium ion Battery, Journal of Nano- and Electronic Physics, Vol. 6(1), pp. 1005 (2014)
Abstract    BibTeX    URL: http://jnep.sumdu.edu.ua/download/numbers/2014/1/articles/en/jnep_2014_V6_01005.pdf   
Abstract: This paper analyses material issues of development of Li-ion batteries to store electrical energy. The performance of the battery is improved by developing the high energy density cathode materials at Nano level. This paper explains the synthesis of most interesting cathode material Lithium Manganese Spinel and its derivatives like transition metal oxide (LiNi0.5Mn1.5O4) using Co-Precipitation chemical method; it is one of the eco-friendly ,effective, economic and easy preparation method. The structural features of LiNi0.5Mn1.5O4 was characterized by XRD - analysis indicated that prepared sample mainly belong to cubic crystal form with Fd3m space group ,with lattice parameter a 8.265 and average crystal size of 31.59 nm and compared the experimental results with computation details from first principle computation methods with Quantum wise Atomistix Tool Kit (ATK),Virtual Nano Lab. First principle computation methods provide important role in emerging and optimizing this electrode material. In this study we present an overview of the computation approach aimed at building LiNi0.5Mn1.5O4 crystal as cathode for Lithium ion battery. We show each significant property can be related to the structural component in the material and can be computed from first principle. By direct comparison with experimental results, we assume to interpret that first principle computation can help to accelerate the design & development of LiNi0.5Mn1.5O4 as cathode material of lithium ion battery for energy storage.
BibTeX:
@article{Bharathi2014,
   title = {Synthesis, Characterization and Density Functional Study of LiMn1.5Ni0.5O4 Electrode for Lithium ion Battery},
   author = {Bharathi, M Aruna and Rao, K Venkateswara and Sushama, M},
  
   journal = {Journal of Nano- and Electronic Physics},
  
  
   volume = {6},
   number = {1},
   pages = {1005},
   year = {2014},
   keywords = {Band structure,Co-precipitation,DFT,Density of states,Li-ion Battery,LiNi0.5Mn1.5O4,Transmission spectrum,XRD,area:battery,area:materials},
   area = {battery,materials}
  
   url = {http://jnep.sumdu.edu.ua/download/numbers/2014/1/articles/en/jnep_2014_V6_01005.pdf},
}
Baoan Bian, Bing Chu, Zhuomao Zhu & Yapeng Zheng, Effect of inserted Cu layer on CoFe/Cu/MgO/CoFe magnetic tunnel junction, International Journal of Modern Physics B, Vol. 29(24), pp. 1550171 (2015)
Abstract    BibTeX    DOI: 10.1142/S0217979215501714   
Abstract: In this paper, we carried out first-principles calculations based on density functional theory and nonequilibrium Green's function to investigate the tunneling magnetoresistance effect in CoFe/Cu/MgO/CoFe magnetic tunnel junctions. Insertion of a nonmagnetic Cu layer between the tunnel barrier and the electrode is shown to result in the inverse and oscillation of the tunneling magnetoresistance as a function of the Cu layer at different bias voltage. The inverse phenomenon is discussed in terms of the conductance and the tunneling probability of electron at zero bias voltage. We suggest that the oscillation of tunneling magnetoresistance results from quantum well state formed in nonmagnetic Cu layer which can bring about the multiple scattering of tunneling electrons due to influence of the bias voltage on the oscillation period of the tunneling magnetoresistance. Read More: http://www.worldscientific.com/doi/abs/10.1142/S0217979215501714
BibTeX:
@article{Bian2015,
   title = {Effect of inserted Cu layer on CoFe/Cu/MgO/CoFe magnetic tunnel junction},
   author = {Bian, Baoan and Chu, Bing and Zhu, Zhuomao and Zheng, Yapeng},
  
   journal = {International Journal of Modern Physics B},
  
  
   volume = {29},
   number = {24},
   pages = {1550171},
   year = {2015},
   keywords = {000umberto,Tunneling magnetoresistance,area:spintronics,first-principles calculations,magnetic tunnel junction},
   area = {spintronics}
   doi = {10.1142/S0217979215501714},
  
}
K. Bikshalu, M.V. Manasa, V.S.K. Reddy, P.C.S. Reddy & K. Venkateswara Rao, Comparison of Atomic Level Simulation Studies of MOSFETs Containing Silica and Lantana Nanooxide Layers, Journal of Nano- And Electronic Physics, Vol. 5(4), pp. 4058 (2013)
Abstract    BibTeX    URL: http://jnep.sumdu.edu.ua/en/component/content/full_article/1135   
Abstract: The intense downscaling of a Metal Oxide Semiconductor Field Effect Transistor (MOSFET) to nano range for improving the device performance requires a high-k dielectric material instead of conventional silica (SiO2) as to avoid Quantum Mechanical Tunneling towards the gate terminal which leads to unnecessary gate current. Out of all the rare earth oxide materials, since lanthana (La2O3) has significantly high dielectric constant (k) and bandgap, we've chosen it as oxide layer for one of the MOSFETs. In this work, we simulated two MOSFETs - one with nano SiO2 oxide layer and other with nano La2O3 oxide layer in the atomic level to analyze and compare the transmission spectra, I-V characteristics and Channel conductance of both the MOSFETs.
BibTeX:
@article{Bikshalu2013,
   title = {Comparison of Atomic Level Simulation Studies of MOSFETs Containing Silica and Lantana Nanooxide Layers},
   author = {Bikshalu, K and Manasa, M V and Reddy, V S K and Reddy, P C S and Rao, K Venkateswara},
  
   journal = {Journal of Nano- And Electronic Physics},
  
  
   volume = {5},
   number = {4},
   pages = {4058},
   year = {2013},
   keywords = {Channel conductance,I-V characteristics,MOSFET,Nano oxide layer,Quantum mechanical tunneling,Transmission spectra,area:semi},
   area = {semi}
  
   url = {http://jnep.sumdu.edu.ua/en/component/content/full_article/1135},
}
Ravi K. Biroju, Gone Rajender & P.K. Giri, On the origin and tunability of blue and green photoluminescence from chemically derived graphene: Hydrogenation and oxygenation studies, Carbon, Vol. 95 pp. 228--238 (2015)
Abstract    BibTeX    DOI: 10.1016/j.carbon.2015.08.036   
Abstract: We report on the identification of structural defects and oxygenated functional groups responsible for blue and green photoluminescence (PL) from the chemically derived graphene (CDG) thin films with the help of Raman imaging/spectroscopy, high resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FTIR) and PL analyses. In particular, we probe the role of in-plane and edge oxygenated functionalities on the evolution of visible PL emissions from CDGs after controlled hydrogenation and oxygenation studies. The assignments of the various PL bands were corroborated from thermogravimetric and FTIR analyses in the CDGs and are directly correlated with the Raman analysis. Our studies reveal that the PL emission spectrum in CDGs can be tuned by controlled hydrogen and oxygen treatments. Two green emission bands in the range of ???497-502 nm and ???534-551 nm are assigned to the COOH and C=O sub-band energy states belonging to the edge sites, while the blue emission is attributed to the localised states of sp2/sp3 domains and epoxy related in-plane functional groups in the CDG materials. Our study demonstrates the tunability of PL spectrum from CDG materials through selective manipulation of the functional groups at the in-plane defects and edge sites.
BibTeX:
@article{Biroju2015,
   title = {On the origin and tunability of blue and green photoluminescence from chemically derived graphene: Hydrogenation and oxygenation studies},
   author = {Biroju, Ravi K. and Rajender, Gone and Giri, P. K.},
  
   journal = {Carbon},
  
   publisher = {Elsevier Ltd},
   volume = {95},
  
   pages = {228--238},
   year = {2015},
   keywords = {area:graphene},
   area = {graphene}
   doi = {10.1016/j.carbon.2015.08.036},
  
}
S.M. Biswal, B. Baral, D. De & A. Sarkar, Study of effect of gate-length downscaling on the analog/RF performance and linearity investigation of InAs-based nanowire Tunnel FET, Superlattices and Microstructures, Vol. 91 pp. 319--330 (2016)
Abstract    BibTeX    DOI: 10.1016/j.spmi.2016.01.021   
Abstract: In this paper, we present a simulation study to report the effect of gate-length downscaling on the analog/RF performance and linearity investigation of InAs-based nanowire (NW) Tunnel FET (TFET). The different RF/analog and linearity figure of merits such as gm, RO, gm∗RO, fT, fmax, GBW and 1-dB compression point of a NW TFET are extracted and the influence of gate-length downscaling on these parameters is analyzed. The RF/analog performance parameters obtained from InAs TFET is compared with an InAs MOSFET of identical dimension. Results reveal that superior RF and Linearity performance was obtained with gate-length downscaling for both devices under consideration. However, advantages of achieving improved RF performance with gate-length downscaling diminishes in terms of poor analog performance with gate-length downscaling for both the devices. This clearly indicates a trade-off between the analog and RF performance of a down-scaled InAs-based NW TFET and MOSFET. The results reveal that InAs TFET provides better fT, fmax and linearity performance in the saturation region than its MOSFET counterpart. It provides a reasonable RO, gm∗RO at lower values of gate-overdrive voltage as compared to the InAs MOSFET. Therefore, this paper concludes that InAs NW TFETs have enormous potential to be a promising contender to the conventional bulk MOSFETs for realization of future generation low-power analog/RF applications. textcopyright 2016 Elsevier Ltd. All rights reserved.
BibTeX:
@article{Biswal2016,
   title = {Study of effect of gate-length downscaling on the analog/RF performance and linearity investigation of InAs-based nanowire Tunnel FET},
   author = {Biswal, S M and Baral, B and De, D and Sarkar, A},
  
   journal = {Superlattices and Microstructures},
  
   publisher = {Elsevier Ltd},
   volume = {91},
  
   pages = {319--330},
   year = {2016},
   keywords = {1-dB compression point,Cut-off frequency gain bandwidth product,InAs Tunnel FET,Transconductance,Transconductance generation factor,area:nanowires,area:semi},
   area = {nanowires,semi}
   doi = {10.1016/j.spmi.2016.01.021},
  
}
Anders Blom, Umberto Martinez Pozzoni, Troels Markussen & Kurt Stokbro, First-principles simulations of nanoscale transistors, Vol. 2015-Octob pp. 52--55 (2015)
Abstract    BibTeX    DOI: 10.1109/SISPAD.2015.7292256   
Abstract: We describe the transport characteristics of a 50 nm (gate length) 2D InAs tunnel field-effect n-i-n transistor in a double-gate fin-like geometry (fin width 2.3 nm) by means of atomic-scale simulations. In particular, we compare results from density functional theory (DFT) using the Meta-GGA exchange correlation potential with those from a tight-binding Hamiltonian. For the first time we show that the two methods give comparable results, proving the predictive power of atomic-scale simulations for this type of devices, and that it is possible to accurately study realistic ultrascaled devices with first-principles methods.
BibTeX:
@inproceedings{Blom2015,
   title = {First-principles simulations of nanoscale transistors},
   author = {Blom, Anders and Pozzoni, Umberto Martinez and Markussen, Troels and Stokbro, Kurt},
   booktitle = {International Conference on Simulation of Semiconductor Processes and Devices, SISPAD},
  
  
  
   volume = {2015-Octob},
  
   pages = {52--55},
   year = {2015},
   keywords = {FinFET,QWpaper,area:semi,atomistic,density-functional theory,first-principles,simulation,transistor,ultrascaled device},
   area = {semi}
   doi = {10.1109/SISPAD.2015.7292256},
  
}
Anders Blom & Kurt Stokbro, Atomistic modeling of semiconductor interfaces, Journal of Computational Electronics, Vol. 12(4), pp. 623--637 (2013)
Abstract    BibTeX    DOI: 10.1007/s10825-013-0531-2   
Abstract: A strong contributing factor to the success of silicon has been a parallel development of accurate modeling tools. For the efficient introduction of new device architectures at the nanoscale, it is necessary to develop similar tools that can handle all the relevant aspects of the new physical properties that will be utilized. This is a very challenging task, as we are dealing not only with many new materials and even more combinations of elements materials, but also effects due the small device sizes and even reduced dimensionality in the form of confinement. In this article we turn our attention to the topic of simulating interfaces from first principles, on the atomic scale. As device dimensions shrink, interfaces start to play a dominating role, and need to be treated as an active part of the device, and not just as an invisible boundary between different materials. We will review the theoretical framework for computing properties of single interfaces, and provide several examples of the types of simulations that can be performed. A concluding separate section is dedicated to computing band offsets.
BibTeX:
@article{Blom2013,
   title = {Atomistic modeling of semiconductor interfaces},
   author = {Blom, Anders and Stokbro, Kurt},
  
   journal = {Journal of Computational Electronics},
  
   publisher = {Springer US},
   volume = {12},
   number = {4},
   pages = {623--637},
   year = {2013},
   keywords = {Band offset,Density functional theory (DFT),Electron transport,Interfaces,Non-equilibrium Green's functions (NEGF),QWpaper,Review,Scattering,Transistor,Tunneling,area:interfaces,area:semi},
   area = {interfaces,semi}
   doi = {10.1007/s10825-013-0531-2},
  
}
Anders Blom & Kurt Stokbro, Towards realistic atomic-scale modeling of nanoscale devices, pp. 1487--1492 (2011)
Abstract    BibTeX    DOI: 10.1109/NANO.2011.6144584   
Abstract: On the nanoscale, electrical currents behave radically different compared to on the microscale. As the active regions become comparable to or smaller than the mean-free path of the material, it becomes necessary to describe the electron transport by quantum-mechanical methods instead of using classical relations like Ohm's law. Over the past decade, methods for computing electron tunneling currents in nanosized junctions have evolved steadily, and are now approaching a sophistication where they can provide real assistance in the development of novel semiconductor materials and devices. At the same time, the industry's demand for such solutions is rising rapidly to meet the challenges both above and under the 16 nm node. In this paper we provide an overview of the current state-of-the-art of the field of how to model electrical currents on the nanoscale, using atomic-scale simulations.
BibTeX:
@inproceedings{Blom2011,
   title = {Towards realistic atomic-scale modeling of nanoscale devices},
   author = {Blom, Anders and Stokbro, Kurt},
   booktitle = {Nanotechnology (IEEE-NANO), 2011 11th IEEE Conference on},
  
  
  
  
  
   pages = {1487--1492},
   year = {2011},
   keywords = {QWpaper,Review,active regions,area:graphene,area:molecular electronics,area:nanotubes,area:semi,atomic-scale modeling,atomic-scale simulation,electron mobility,electron transport,electron tunneling current,nanoelectronics,nanoscale devices,nanoscale electrical currents,nanosized junctions,quantum-mechanical method,semiconductor device,semiconductor device models,semiconductor materials,technology CAD (electronics),tunnelling},
   area = {graphene,molecular electronics,nanotubes,semi}
   doi = {10.1109/NANO.2011.6144584},
  
}
Oliver Böhm, Stephan Pfadenhauer, Roman Leitsmann, Philipp Plänitz, Eduard Schreiner & Michael Schreiber, ReaxFF+ A New Reactive Force Field Method for the Accurate Description of Ionic Systems and Its Application to the Hydrolyzation of Aluminosilicates, The Journal of Physical Chemistry C, Vol. 120(20), pp. 10849--10856 (2016)
Abstract    BibTeX    DOI: 10.1021/acs.jpcc.6b00720    URL: http://pubs.acs.org/doi/abs/10.1021/acs.jpcc.6b00720   
Abstract: In this paper we present a powerful extension of the reactive force field method ReaxFF, which we call ReaxFF+. It combines the charge equilibrium scheme with the bond order principle. The main advantage of this procedure is the correct distinction and description of covalent and ionic bonds. It allows reactive molecular dynamic simulations in ionic gases and liquids. To demonstrate the accuracy of this new method, we study the hydrolyzation of aluminosilicates. Comparing the results with experimental and ab initio data, we can prove the high accuracy of our method. This shows that ReaxFF+ is a powerful force field simulation tool for reactions in acidic or alkaline environments.
BibTeX:
@article{Bohm2016,
   title = {ReaxFF+ A New Reactive Force Field Method for the Accurate Description of Ionic Systems and Its Application to the Hydrolyzation of Aluminosilicates},
   author = {Böhm, Oliver and Pfadenhauer, Stephan and Leitsmann, Roman and Plänitz, Philipp and Schreiner, Eduard and Schreiber, Michael},
  
   journal = {The Journal of Physical Chemistry C},
  
  
   volume = {120},
   number = {20},
   pages = {10849--10856},
   year = {2016},
   keywords = {area:materials,atkclassical,reaxff},
   area = {materials}
   doi = {10.1021/acs.jpcc.6b00720},
   url = {http://pubs.acs.org/doi/abs/10.1021/acs.jpcc.6b00720},
}
Mads Brandbyge, Kurt Stokbro, Jeremy Taylor, Jose-Luis Mozos & Pablo Ordejon, Origin of current-induced forces in an atomic gold wire: A first-principles study, Physical Review B, Vol. 67(19), pp. 193104 (2003)
Abstract    BibTeX    DOI: 10.1103/PhysRevB.67.193104   
Abstract: We address the microscopic origin of the current-induced forces by analyzing results of first principles density functional calculations of atomic gold wires connected to two gold electrodes with different electrochemical potentials. We find that current induced forces are closely related to the chemical bonding, and arise from the rearrangement of bond charge due to the current flow. We explain the current induced bond weakening/strengthening by introducing bond charges decomposed into electrode components.
BibTeX:
@article{Brandbyge2003,
   title = {Origin of current-induced forces in an atomic gold wire: A first-principles study},
   author = {Brandbyge, Mads and Stokbro, Kurt and Taylor, Jeremy and Mozos, Jose-Luis and Ordejon, Pablo},
  
   journal = {Physical Review B},
  
   publisher = {American Physical Society},
   volume = {67},
   number = {19},
   pages = {193104},
   year = {2003},
   keywords = {TranSIESTA-C,area:molecular electronics,area:nanowires},
   area = {molecular electronics,nanowires}
   doi = {10.1103/PhysRevB.67.193104},
  
}
Yongqing Cai, Zhaoqiang Bai, Hui Pan, Yuan Ping Feng, Boris I. Yakobson & Yong-Wei Zhang, Constructing metallic nanoroads on a MoS2 monolayer via hydrogenation, Nanoscale, Vol. 6(3), pp. 1691--1697 (2014)
Abstract    BibTeX    DOI: 10.1039/c3nr05218d   
Abstract: Monolayer transition metal dichalcogenides recently emerged as a new family of two-dimensional materials potentially suitable for numerous applications in electronic and optoelectronic devices due to the presence of a finite band gap. Many proposed applications require efficient transport of charge carriers within these semiconducting monolayers. However, constructing a stable conducting nanoroad on these atomically thin semiconductors is still a challenge. Here we demonstrate that hydrogenation on the surface of a MoS2 monolayer induces a semiconductor-metal transition, and strip-patterned hydrogenation is able to generate a conducting nanoroad. The band-gap closing arises from the formation of in-gap hybridized states mainly consisting of Mo 4d orbitals, as well as the electron donation from hydrogen to the lattice host. Ballistic conductance calculations reveal that such a nanoroad on the MoS2 surface exhibits an integer conductance, indicating small carrier scattering, and thus is ideal for serving as a conducting channel or an interconnect without compromising the mechanical and structural integrity of the monolayer.
BibTeX:
@article{Cai2014,
   title = {Constructing metallic nanoroads on a MoS2 monolayer via hydrogenation},
   author = {Cai, Yongqing and Bai, Zhaoqiang and Pan, Hui and Feng, Yuan Ping and Yakobson, Boris I and Zhang, Yong-Wei},
  
   journal = {Nanoscale},
  
   publisher = {Royal Society of Chemistry (RSC)},
   volume = {6},
   number = {3},
   pages = {1691--1697},
   year = {2014},
   keywords = {MoS2,area:nanotubes,conductance},
   area = {nanotubes}
   doi = {10.1039/c3nr05218d},
  
}
Yongqing Cai, Aihua Zhang, Yuan Ping Feng & Chun Zhang, Switching and rectification of a single light-sensitive diarylethene molecule sandwiched between graphene nanoribbons, The Journal of Chemical Physics, Vol. 135(18), pp. 184703 (2011)
Abstract    BibTeX    DOI: 10.1063/1.3657435   
Abstract: The "open" and "closed" isomers of the diarylethene molecule that can be converted between each other upon photo-excitation are found to have drastically different current-voltage characteristics when sandwiched between two graphene nanoribbons (GNRs). More importantly, when one GNR is metallic and another one is semiconducting, strong rectification behavior of the "closed" diarylethene isomer with the rectification ratio textgreater10ˆ3 is observed. The surprisingly high rectification ratio originates from the band gap of GNR and the bias-dependent variation of the lowest unoccupied molecular orbital of the diarylethene molecule, the combination of which completely shuts off the current at positive biases. Results presented in this paper may form the basis for a new class of molecular electronic devices.
BibTeX:
@article{Cai2011a,
   title = {Switching and rectification of a single light-sensitive diarylethene molecule sandwiched between graphene nanoribbons},
   author = {Cai, Yongqing and Zhang, Aihua and Ping Feng, Yuan and Zhang, Chun},
  
   journal = {The Journal of Chemical Physics},
  
   publisher = {AIP},
   volume = {135},
   number = {18},
   pages = {184703},
   year = {2011},
   keywords = {area:graphene,graphene nanoribbon,molecular electronic states,nanostructured materials,optical materials,rectification},
   area = {graphene}
   doi = {10.1063/1.3657435},
  
}
Yongqing Cai, Miao Zhou, Minggang Zeng, Chun Zhang & Yuan Ping Feng, Adsorbate and defect effects on electronic and transport properties of gold nanotubes, Nanotechnology, Vol. 22(21), pp. 215702 (2011)
Abstract    BibTeX    DOI: 10.1088/0957-4484/22/21/215702   
Abstract: First-principles calculations have been performed to study the effects of adsorbates (CO molecules and O atoms) and defects on electronic structures and transport properties of Au nanotubes (Au(5, 3) and Au(5, 5)). For CO adsorption, various adsorption sites of CO on the Au tubes were considered. The vibrational frequency of the CO molecule was found to be very different for two nearly degenerate stable adsorption configurations of Au(5, 3), implying the possibility of distinguishing these two configurations via measuring the vibrational frequency of CO in experiments. After CO adsorption, the conductance of Au(5, 3) decreases by 0.9 G 0 and the conductance of Au(5, 5) decreases by approximately 0.5 G 0 . For O-adsorbed Au tubes, O atoms strongly interact with Au tubes, leading to around 2 G 0 of drop in conductance for both Au tubes. These results may have implications for Au-tube-based chemical sensing. When a monovacancy defect is present, we found that, for both tubes, the conductance decreases by around 1 G 0 . Another type of defect arising from the adhesion of one Au atom is also considered. For this case, it is found that, for the Au(5, 3) tube, the defect decreases the conductance by nearly 1 G 0 , whereas for Au(5, 5), the decrease in conductance is only 0.3 G 0 .
BibTeX:
@article{Cai2011,
   title = {Adsorbate and defect effects on electronic and transport properties of gold nanotubes},
   author = {Cai, Yongqing and Zhou, Miao and Zeng, Minggang and Zhang, Chun and Feng, Yuan Ping},
  
   journal = {Nanotechnology},
  
  
   volume = {22},
   number = {21},
   pages = {215702},
   year = {2011},
   keywords = {adsorbed molecules,area:nanotubes,gold nanotube,vacancies},
   area = {nanotubes}
   doi = {10.1088/0957-4484/22/21/215702},
  
}
Serkan Caliskan, Tuning the spin dependent behavior of monatomic carbon wires between nickel electrodes, Physics Letters A, Vol. 377(28-30), pp. 1766--1773 (2013)
Abstract    BibTeX    DOI: 10.1016/j.physleta.2013.05.007ggallium   
Abstract: Abstract Spin polarized Density Functional Theory combined with Non-Equilibrium Green's Function Formalism is applied to investigate the spin dependent transport in carbon based monatomic systems. Both one-dimensional linear and ring structures sandwiched between spin polarized nickel electrodes are examined. Incorporating of nickel electrodes and rings leads to interesting spin dependent properties. The influence of electrode structure is also addressed, using the Ni(100) pyramidal and plane electrodes. It is revealed that spin dependent behavior is largely determined by the atomic arrangement of the monatomic system, and that both the transport and magnetic properties can be tuned by odd/even disparity and/or appropriate ring(s). The mechanisms governing the spin dependent properties in these structures are discussed.
BibTeX:
@article{Caliskan2013,
   title = {Tuning the spin dependent behavior of monatomic carbon wires between nickel electrodes},
   author = {Caliskan, Serkan},
  
   journal = {Physics Letters A},
  
  
   volume = {377},
   number = {28-30},
   pages = {1766--1773},
   year = {2013},
   keywords = {area:molecular electronics,area:spintronics,monatomic wires,nickel lead,spin dependent transport},
   area = {molecular electronics,spintronics}
   doi = {10.1016/j.physleta.2013.05.007ggallium},
  
}
Serkan Caliskan & M. Canturk, Spin dependent transport behavior in small world networks, The European Physical Journal B - Condensed Matter and Complex Systems, Vol. 85(9), pp. 1--8 (2012)
Abstract    BibTeX    DOI: 10.1140/epjb/e2012-30253-5   
Abstract: Density functional theory (DFT) combined with the non equilibrium Green's function formalism (NEGF) is applied to perform spin polarized transport calculations on small world network (SWN) systems consisting of atomic wires. Including the spin property in SWN structures leads to interesting electrical properties. It is revealed that the emerging spin polarization depends mainly on the SWN geometry given by the asymmetric distribution of loops joining the arbitrary atoms on the main chain. The spin-asymmetric behavior which yields the spin polarization is found to be largely determined by those loops which are close to the electrodes. However, spin polarization may vanish for a specific SWN structure due to symmetry.
BibTeX:
@article{Caliskan2012,
   title = {Spin dependent transport behavior in small world networks},
   author = {Caliskan, Serkan and Canturk, M},
  
   journal = {The European Physical Journal B - Condensed Matter and Complex Systems},
  
   publisher = {Springer Berlin / Heidelberg},
   volume = {85},
   number = {9},
   pages = {1--8},
   year = {2012},
   keywords = {area:molecular electronics,area:spintronics,atomic chain,carbon atomic wire,coherent transport,complex networks,generalized gradient approximation,nanomaterials,nanowires,point-contact,quantized conductance,quantum wire,semiconductors,spin,spintronics,transmission},
   area = {molecular electronics,spintronics}
   doi = {10.1140/epjb/e2012-30253-5},
  
}
Serkan Caliskan & S. Guner, The role of Co atoms in spin dependent electronic properties of graphite-like ZnO structures, Journal of Magnetism and Magnetic Materials, Vol. 373 pp. 96--102 (2015)
Abstract    BibTeX    DOI: 10.1016/j.jmmm.2014.05.039   
Abstract: A first principles study is employed to reveal the electronic properties of graphite-like Co doped ZnO structures composed of atomic layers when spin property of electrons is involved. The influence of Co atoms, which are substituting the Zn atoms, was addressed through distinct atomic arrangements formed by specific atomic configurations and various Co concentrations. We obtained that the spin dependent behavior is largely determined by the atomic arrangement which can crucially impact the electronic structure for a certain spin orientation. It was observed that atomic configuration is an essential factor which may reduce or enhance the minority-spin energy gap relative to majority one. It was shown that the emerging spin polarization can be manipulated by the atomic arrangement of the layered structures. Both the spin polarization and the magnetic moment were found to be contributed by both Co and O atoms. The stability of a system via formation energy, the role of Co dopants positioned at different Zn sites, the number of both Co atoms and layers in a supercell, and the mechanisms governing the spin dependent behavior of these structures are discussed.
BibTeX:
@article{Caliskan2015b,
   title = {The role of Co atoms in spin dependent electronic properties of graphite-like ZnO structures},
   author = {Caliskan, Serkan and Guner, S},
  
   journal = {Journal of Magnetism and Magnetic Materials},
  
  
   volume = {373},
  
   pages = {96--102},
   year = {2015},
   keywords = {Density functional theory,Density of state,Doped ZnO,First principles,area:2dmat,area:spintronics},
   area = {2dmat,spintronics}
   doi = {10.1016/j.jmmm.2014.05.039},
  
}
Serkan Caliskan & S. Guner, First principles study on the spin dependent electronic behavior of Co doped ZnO structures joining the Al electrodes, Journal of Alloys and Compounds, Vol. 619 pp. 91--97 (2014)
Abstract    BibTeX    DOI: 10.1016/j.jallcom.2014.09.037   
Abstract: Employing first principles, Co doped ZnO systems between the Al electrodes were investigated through the Density Functional Theory combined with Non Equilibrium Green's Function Formalism. Electronic transport properties of these systems, in the presence of spin property, were revealed using substitutional Co atoms in a supercell. Spin resolved electronic behavior was observed to be crucially governed by atomic configuration, defined by doping position and concentration, of the system joining the electrodes. Using this feature, one can manipulate both the electronic transport and magnetic properties of an Al-Co doped ZnO-Al device structure. A nonlinearity was exhibited in current-voltage characteristics for Co doped ZnO systems attached to the Al electrodes, which implies a Schottky-like contact at the interface. The induced magnetic moment and spin polarization in the system, yielding the spin dependent transport, were elucidated.
BibTeX:
@article{Caliskan2014,
   title = {First principles study on the spin dependent electronic behavior of Co doped ZnO structures joining the Al electrodes},
   author = {Caliskan, Serkan and Guner, S},
  
   journal = {Journal of Alloys and Compounds},
  
  
   volume = {619},
  
   pages = {91--97},
   year = {2014},
   keywords = {Al electrodes,Density Functional Theory,Doped ZnO,First principles,Spin dependent behavior,area:interfaces,area:spintronics},
   area = {interfaces,spintronics}
   doi = {10.1016/j.jallcom.2014.09.037},
  
}
Serkan Caliskan & F. Hazar, First principles study on the spin unrestricted electronic structure properties of transition metal doped InN nanoribbons, Superlattices and Microstructures, Vol. 84 pp. 170--180 (2015)
Abstract    BibTeX    DOI: 10.1016/j.spmi.2015.05.004   
Abstract: In the present study, first principles calculations were carried out to reveal the spin unrestricted electronic structure behavior of both pure and transition metal (TM) atom (V and Co) doped InN nanoribbons (InN-NRs). The influence of a substitutionally doped TM atom on the electronic structure nature was examined. The role of a TM dopant together with its location, governing the characteristic of spin dependent electronic property of a doped InN-NR, was addressed. The relevant properties were extracted through Hubbard correction for In-d, N-p and TM-d states. We observed that a single TM dopant diminished the spin dependent energy gap and can result in a significant induced magnetic moment in an InN-NR system. It was exposed that TM dopants can play an essential role in the spin unrestricted electronic behavior and spin polarization, which can be tuned through a V or Co atom at a certain position.
BibTeX:
@article{Caliskan2015,
   title = {First principles study on the spin unrestricted electronic structure properties of transition metal doped InN nanoribbons},
   author = {Caliskan, Serkan and Hazar, F},
  
   journal = {Superlattices and Microstructures},
  
  
   volume = {84},
  
   pages = {170--180},
   year = {2015},
   keywords = {Energy gap,First principles,InN nanoribbon,Spin,area:graphene,area:materials,area:spin},
   area = {graphene,materials,spin}
   doi = {10.1016/j.spmi.2015.05.004},
  
}
Serkan Caliskan & A. Laref, Spin transport properties of n-polyacene molecules (n=1-15) connected to Ni surface electrodes: Theoretical analysis, Scientific Reports, Vol. 4 pp. 7363 (2014)
Abstract    BibTeX    DOI: 10.1038/srep07363   
Abstract: Using non-equilibrium Green function formalism in conjunction with density functional theory, we explore the spin-polarized transport characteristics of several planar n-acene molecules suspended between two semi-infinite Ni electrodes via the thiol group. We examine the spin-dependence transport on Ni-n-acenes-Ni junctions, while the number of fused benzene rings varies between 1 and 15. Intriguingly, the induced magnetic moments of small acene molecules are higher than that of longer acene rings. The augmentation of fused benzene rings affects both the magnetic and transport features, such as the transmission function and conductance owing to their coupling to the Ni surface contacts via the anchoring group. The interplay between the spin-polarized transport properties, structural configuration and molecular electronic is a fortiori essential in these attractive molecular devices. Thus, this can conduct to the engineering of the electron spin transport in atomistic and molecular junctions. These prominent molecules convincingly infer that the molecular spin valves can conduct to thriving molecular devices.
BibTeX:
@article{Caliskan2014b,
   title = {Spin transport properties of n-polyacene molecules (n=1-15) connected to Ni surface electrodes: Theoretical analysis},
   author = {Caliskan, Serkan and Laref, A},
  
   journal = {Scientific Reports},
  
  
   volume = {4},
  
   pages = {7363},
   year = {2014},
   keywords = {Magnetic devices,application,area:molecular electronics,area:spintronics,organic-inorganic nanostructures},
   area = {molecular electronics,spintronics}
   doi = {10.1038/srep07363},
  
}
Serkan Caliskan & A. Laref, The anchoring effect on the spin transport properties and I-V characteristics of pentacene molecular devices suspended between nickel electrodes, Phys. Chem. Chem. Phys., Vol. 16(26), pp. 13191--13208 (2014)
Abstract    BibTeX    DOI: 10.1039/C3CP54319F   
Abstract: Spin-polarized transport properties are determined for pentacene sandwiched between Ni surface electrodes with various anchoring ligands. These calculations are carried out using spin density functional theory in tandem with a non-equilibrium Green's function technique. The presence of a Se atom at the edge of the pentacene molecule significantly modifies the transport properties of the device because Se has a different electronegativity than S. Our theoretical results clearly show a larger current for spin-up electrons than for spin-down electrons in the molecular junction that is attached asymmetrically across the Se linker at one side of the Ni electrodes (in an APL magnetic orientation). Moreover, this molecular junction exhibits pronounced NDR as the bias voltage is increased from 0.8 to 1.0 V. However, this novel NDR behavior is only detected in this promising pentacene molecular device. The NDR in the current-voltage (I-V) curve results from the narrowness of the density of states for the molecular states. The feasibility of controlling the TMR is also predicted in these molecular device nanostructures. Spin-dependent transmission calculations show that the sign and strength of the current-bias voltage characteristics and the TMR could be tailored for the organic molecule devices. These molecular junctions are joined symmetrically and asymmetrically between Ni metallic probes across the S and Se atoms (at the ends of the edges of the pentacene molecule). Our theoretical findings show that spin-valve phenomena can occur in these prototypical molecular junctions. The TMR and NDR results show that nanoscale junctions with spin valves could play a vital role in the production of novel functional molecular devices.
BibTeX:
@article{Caliskan2014a,
   title = {The anchoring effect on the spin transport properties and I-V characteristics of pentacene molecular devices suspended between nickel electrodes},
   author = {Caliskan, Serkan and Laref, A},
  
   journal = {Phys. Chem. Chem. Phys.},
  
   publisher = {The Royal Society of Chemistry},
   volume = {16},
   number = {26},
   pages = {13191--13208},
   year = {2014},
   keywords = {area:molecular electronics,nickel,pentacene,spin transport},
   area = {molecular electronics}
   doi = {10.1039/C3CP54319F},
  
}
Can Cao, L.N. Chen, D. Zhang, W.R. Huang, S.S. Ma & H. Xu, Electronic properties and conductance suppression of defected and doped zigzag graphene nanoribbons, Solid State Communications, Vol. 152(1), pp. 45--49 (2012)
Abstract    BibTeX    DOI: 10.1016/j.ssc.2011.10.004   
Abstract: By using the first-principles calculation based on density functional theory, we investigate the electronic structures and transport properties of the defected and doped zigzag graphene nanoribbons (ZGNRs). The effects of multivacancies defects and impurities have been considered. The results show that band structures of ZGNRs can be tuned strongly and currents drop drastically due to the defect and impurities. Moreover, the notable suppression of conductance can be found near the Fermi level, leading to the negative differential resistance (NDR) behavior under low bias. This effect presents a possibility in novel nanoelectronics devices application.
BibTeX:
@article{Cao2012,
   title = {Electronic properties and conductance suppression of defected and doped zigzag graphene nanoribbons},
   author = {Cao, Can and Chen, L N and Zhang, D and Huang, W R and Ma, S S and Xu, H},
  
   journal = {Solid State Communications},
  
  
   volume = {152},
   number = {1},
   pages = {45--49},
   year = {2012},
   keywords = {area:graphene,defect,electronic structures and transport property,first-principles,graphene nanoribbons,impurity},
   area = {graphene}
   doi = {10.1016/j.ssc.2011.10.004},
  
}
Can Cao, Ling-na Chen, Weirong Huang & Hui Xu, Electronic Transport of Zigzag Graphene Nanoribbons with Edge Hydrogenation and Oxidation, The Open Chemical Physics Journal, Vol. 4 pp. 1--7 (2012)
Abstract    BibTeX    DOI: 10.2174/1874412501204010001   
Abstract: By using non-equilibrium Green's functions in combination with the density-functional theory, we study the effect of zigzag graphene nanoribbons with edge hydrogenation and oxidation on transport properties. We find that for the ferromagnetic (FM) configuration the ZGNRs with CH2-CH group exhibit spin diode effect in which only one spin can occur under positive bias while the other spin occurs under negative bias. In the antiferromagnetic (AF) state the symmetric ZGNRs with CH2-CH group show the spin filter effect within some specific energy windows. However, the asymmetric ZGNRs with CH2-CH group do not show such a spin filter effect. We also find that the symmetric and asymmetric ZGNRs with C2O-CH group in AF configurations show similar transport behaviors at the Fermi level. Such ZGNRs might be exploited in spintronic nanodevices.
BibTeX:
@article{Cao2012a,
   title = {Electronic Transport of Zigzag Graphene Nanoribbons with Edge Hydrogenation and Oxidation},
   author = {Cao, Can and Chen, Ling-na and Huang, Weirong and Xu, Hui},
  
   journal = {The Open Chemical Physics Journal},
  
  
   volume = {4},
  
   pages = {1--7},
   year = {2012},
   keywords = {area:graphene,area:spintronics,first-principles,graphene,spin filter,spin-diode effect,transport properties},
   area = {graphene,spintronics}
   doi = {10.2174/1874412501204010001},
  
}
Can Cao, Ling-Na Chen, Meng-Qiu Long, Wei-Rong Huang & Hui Xu, Electronic transport properties on transition-metal terminated zigzag graphene nanoribbons, Journal of Applied Physics, Vol. 111(11), pp. 113708 (2012)
Abstract    BibTeX    DOI: 10.1063/1.4723832   
Abstract: By using non-equilibrium Green's functions in combination with the density-functional theory, we investigate the spin transport properties of molecular junctions based on 3d transition terminated zigzag graphene nanoribbons. The results show that the electronic transport properties are strongly depending on the type of terminated atom at the edge of ribbon. The currents of spin-up and spin-down display different behaviors, and the spin-filter effects can be observed. These unconventional doping effects could be used to design novel nanospintronics devices.
BibTeX:
@article{Cao2012b,
   title = {Electronic transport properties on transition-metal terminated zigzag graphene nanoribbons},
   author = {Cao, Can and Chen, Ling-Na and Long, Meng-Qiu and Huang, Wei-Rong and Xu, Hui},
  
   journal = {Journal of Applied Physics},
  
   publisher = {AIP},
   volume = {111},
   number = {11},
   pages = {113708},
   year = {2012},
   keywords = {Fermi level,Green's function methods,area:graphene,area:spintronics,density functional theory,doping,graphene,nanoribbons,spin polarised transport},
   area = {graphene,spintronics}
   doi = {10.1063/1.4723832},
  
}
Can Cao, Ling-Na Chen, Meng-Qiu Long & Hui Xu, Rectifying performance in zigzag graphene nanoribbon heterojunctions with different edge hydrogenations, Physics Letters A, Vol. 377(31-33), pp. 1905--1910 (2013)
Abstract    BibTeX    DOI: 10.1016/j.physleta.2013.05.004   
Abstract: Using nonequilibrium Green's functions in combination with the density functional theory, we investigated the electronic transport behaviors of zigzag graphene nanoribbon (ZGNR) heterojunctions with different edge hydrogenations. The results show that electronic transport properties of ZGNR heterojunctions can be modulated by hydrogenations, and prominent rectification effects can be observed. We propose that the edge dihydrogenation leads to a blocking of electronic transfer, as well as the changes of the distribution of the frontier orbital at negative/positive bias might be responsible for the rectification effects. These results may be helpful for designing practical devices based on graphene nanoribbons.
BibTeX:
@article{Cao2013,
   title = {Rectifying performance in zigzag graphene nanoribbon heterojunctions with different edge hydrogenations},
   author = {Cao, Can and Chen, Ling-Na and Long, Meng-Qiu and Xu, Hui},
  
   journal = {Physics Letters A},
  
  
   volume = {377},
   number = {31-33},
   pages = {1905--1910},
   year = {2013},
   keywords = {area:graphene,edge hydrogenation,electronic transport property,rectifying effect,zigzag graphene nanoribbon heterojunction},
   area = {graphene}
   doi = {10.1016/j.physleta.2013.05.004},
  
}
Can Cao, Mengqiu Long & Xiancheng Mao, Symmetry-Dependent Spin Transport Properties and Spin-Filter Effects in Zigzag-Edged Germanene Nanoribbons, Journal of Nanomaterials, Vol. 2015 pp. 810659 (2015)
Abstract    BibTeX    DOI: 10.1155/2015/810659   
Abstract: We performed the first-principles calculations to investigate the spin-dependent electronic transport properties of zigzag-edged germanium nanoribbons (ZGeNRs). We choose of ZGeNRs with odd and even widths of 5 and 6, and the symmetry-dependent transport properties have been found, although the ? mirror plane is absent in ZGeNRs. Furthermore, even-? and odd-? ZGeNRs have very different current-voltage relationships. We find that the even 6-ZGeNR shows a dual spin-filter effect in antiparallel (AP) magnetism configuration, but the odd 5-ZGeNR behaves as conventional conductors with linear current-voltage dependence. It is found that when the two electrodes are in parallel configuration, the 6-ZGeNR system is in a low resistance state, while it can switch to a much higher resistance state when the electrodes are in AP configuration, and the magnetoresistance of 270% can be observed.
BibTeX:
@article{Cao2015a,
   title = {Symmetry-Dependent Spin Transport Properties and Spin-Filter Effects in Zigzag-Edged Germanene Nanoribbons},
   author = {Cao, Can and Long, Mengqiu and Mao, Xiancheng},
  
   journal = {Journal of Nanomaterials},
  
  
   volume = {2015},
  
   pages = {810659},
   year = {2015},
   keywords = {area:2dmat},
   area = {2dmat}
   doi = {10.1155/2015/810659},
  
}
Can Cao, Meng-qiu Long, Xiao-jiao Zhang & Xian-cheng Mao, Giant magnetoresistance and spin-filtering effects in zigzag graphene and hexagonal boron nitride based heterojunction, Physics Letters A, Vol. 379(24-25), pp. 1527--1531 (2015)
Abstract    BibTeX    DOI: 10.1016/j.physleta.2015.03.036   
Abstract: The spin-dependent electronic transport properties of heterojunction constructed by bare zigzag graphene nanoribbon and hexagonal boron nitride nanoribbon are investigated by the non-equilibrium Green's function method in combination with the density functional theory. The results show that the giant magnetoresistance effect can be realized in the heterojunction, and the magnetoresistance ratio can reach to 106. Moreover, it is found that the heterojunction is a good spin-filtering device with nearly 100% spin filtering efficiency at a wide bias voltage region in both ferromagnetic and antiferromagnetic magnetic configurations.
BibTeX:
@article{Cao2015,
   title = {Giant magnetoresistance and spin-filtering effects in zigzag graphene and hexagonal boron nitride based heterojunction},
   author = {Cao, Can and Long, Meng-qiu and Zhang, Xiao-jiao and Mao, Xian-cheng},
  
   journal = {Physics Letters A},
  
  
   volume = {379},
   number = {24-25},
   pages = {1527--1531},
   year = {2015},
   keywords = {Electronic transport property,Giant magnetoresistance,Heterojunction,Rectifying effect,Spin-filtering effect,area:2dmat,area:materials},
   area = {2dmat,materials}
   doi = {10.1016/j.physleta.2015.03.036},
  
}
Valentina Cauda, Paolo Motto, Denis Perrone, Gianluca Piccinini & Danilo Demarchi, pH-triggered conduction of amine-functionalized single ZnO wire integrated on a customized nanogap electronic platform, Nanoscale Research Letters, Vol. 9 pp. 53 (2014)
Abstract    BibTeX    DOI: 10.1186/1556-276X-9-53   
Abstract: The electrical conductance response of single ZnO microwire functionalized with amine-groups was tested upon an acid pH variation of a solution environment after integration on a customized gold electrode array chip. ZnO microwires were easily synthesized by hydrothermal route and chemically functionalized with aminopropyl groups. Single wires were deposited from the solution and then oriented through dielectrophoresis across eight nanogap gold electrodes on a platform single chip. Therefore, eight functionalized ZnO microwire-gold junctions were formed at the same time, and being integrated on an ad hoc electronic platform, they were ready for testing without any further treatment. Experimental and simulation studies confirmed the high pH-responsive behavior of the amine-modified ZnO-gold junctions, obtaining in a simple and reproducible way a ready-to-use device for pH detection in the acidic range. We also compared this performance to bare ZnO wires on the same electronic platform, showing the superiority in pH response of the amine-functionalized material.
BibTeX:
@article{Cauda2014,
   title = {pH-triggered conduction of amine-functionalized single ZnO wire integrated on a customized nanogap electronic platform},
   author = {Cauda, Valentina and Motto, Paolo and Perrone, Denis and Piccinini, Gianluca and Demarchi, Danilo},
  
   journal = {Nanoscale Research Letters},
  
  
   volume = {9},
  
   pages = {53},
   year = {2014},
   keywords = {Aminopropyl functionalization,Gold-ZnO-gold,Nanogap electrodes,ZnO wire,area:nanowires,pH-responsive behavior},
   area = {nanowires}
   doi = {10.1186/1556-276X-9-53},
  
}
Oscar Cespedes, May Wheeler, Timothy Moorsom & Michel Viret, Unexpected Magnetic Properties of Gas-Stabilized Platinum Nanostructures in the Tunneling Regime, Nano Letters, Vol. 15(1), pp. 45--50 (2014)
Abstract    BibTeX    DOI: 10.1021/nl504254d   
Abstract: Nanostructured materials often have properties widely different from bulk, imposed by quantum limits to a physical property of the material. This includes, for example, superparamagnetism and quantized conductance, but original properties such as magnetoresistance in nonmagnetic molecular structures may also emerge. In this Letter, we report on the atomic manipulation of platinum nanocontacts in order to induce magnetoresistance. Platinum is a paramagnetic 5d metal, but atomic chains of this material have been predicted to be magnetically ordered with a large anisotropy. Remarkably, we find that a gas flow stabilizes Pt atomic structures in a break junction experiment, where we observe extraordinary resistance changes over 30000% in a temperature range up to 77 K. Simulations indicate that this behavior may stem from a previously unknown magnetically ordered, low-energy state in platinum oxide atomic chains. This is supported by measurements in Pt/PtOx superlattices revealing the presence of a ferromagnetic moment. These properties open new paths of research for atomic scale "dirty" magnetic sensors and quantum devices.
BibTeX:
@article{Cespedes2014,
   title = {Unexpected Magnetic Properties of Gas-Stabilized Platinum Nanostructures in the Tunneling Regime},
   author = {Cespedes, Oscar and Wheeler, May and Moorsom, Timothy and Viret, Michel},
  
   journal = {Nano Letters},
  
  
   volume = {15},
   number = {1},
   pages = {45--50},
   year = {2014},
   keywords = {Magnetoresistance,area:molecular electronics,area:spintronics,nanocontact,platinum oxide,spin-dependent tunneling},
   area = {molecular electronics,spintronics}
   doi = {10.1021/nl504254d},
  
}
Mayank Chakraverty, P.S. Harisankar & Vaibhav Ruparelia, Simulation of Electrical Characteristics of Gate All around Silicon Nanowire Field Effect Transistor using Extended Hückel Theory Based Semi Empirical Approach, IOSR Journal of Electronics and Communication Engineering (IOSR-JECE), (2016)
Abstract    BibTeX    URL: http://www.iosrjournals.org/iosr-jece/papers/Conf.15010/Volume 1/X.ECE-133.pdf   
Abstract: Gate All Around (GAA) FET stands out as one of the most promising FET designs to replace the currently planar MOSFETs due to its ability to provide better gate control and better immunity to short channel effects. .This paper reports the electrical characteristics of GAA Silicon Nanowire Field Effect Transistor obtained using Extended Huckel Theory based Semi Empirical Method. The physics behind the Semi Empirical method has been presented in brief. The nanowire transistor has been simulated with two different gate dielectrics (SiO2 & ZrO2) and the electrical characteristics resulting from the two structures have been compared for power efficiency. A comparison of off-state current and off-state channel conductance between the two nanowire transistor structures has been presented towards the end of the paper that demonstrates that ZrO2 gate dielectric based silicon nanowire transistor is power efficient than its counterpart with SiO2 gate dielectric.
BibTeX:
@article{Chakraverty2016a,
   title = {Simulation of Electrical Characteristics of Gate All around Silicon Nanowire Field Effect Transistor using Extended Hückel Theory Based Semi Empirical Approach},
   author = {Chakraverty, Mayank and S, Harisankar P and Ruparelia, Vaibhav},
  
   journal = {IOSR Journal of Electronics and Communication Engineering (IOSR-JECE)},
  
  
  
  
  
   year = {2016},
   keywords = {Extended Huckel,Gate All Around,Gate Dielectric,MOSFETs,Nanowire,Semi Empirical,industrial},
  
  
   url = {http://www.iosrjournals.org/iosr-jece/papers/Conf.15010/Volume 1/X.ECE-133.pdf},
}
Mayank Chakraverty, P.S. Harisankar, Kinshuk Gupta, Vaibhav Ruparelia & Hisham Rahman, Simulation of Electrical Characteristics of Silicon and Germanium Nanowires Progressively Doped to Zener Diode Configuration Using First Principle Calculations, pp. 421--428 (2016)
Abstract    BibTeX    DOI: 10.1007/978-81-322-2728-1_38    URL: http://link.springer.com/10.1007/978-81-322-2728-1_38   
Abstract: The effect of incorporating pairs of dopant atoms of opposite polarities into the nanowire lattice on the electrical behavior of nanowires has been presented in this paper. The dopants used are boron and phosphorus atoms. Intrinsic silicon nanowire is incapacitated with boron-phosphorus dopant atom pairs in a progressive manner, starting from one pair to nine dopant-atom pairs. The nanowire is simulated each time an additional dopant pair is introduced in the nanowire lattice to obtain current-voltage characteristics. These characteristics have been compared with that obtained by introducing similar dopants in an intrinsic germanium nanowire lattice. The power efficiencies of both intrinsic and doped silicon and germanium nanowires have been discussed towards the end of the paper.
BibTeX:
@incollection{Chakraverty2016,
   title = {Simulation of Electrical Characteristics of Silicon and Germanium Nanowires Progressively Doped to Zener Diode Configuration Using First Principle Calculations},
   author = {Chakraverty, Mayank and Harisankar, P S and Gupta, Kinshuk and Ruparelia, Vaibhav and Rahman, Hisham},
   booktitle = {Lecture Notes in Electrical Engineering 372},
  
   editor = {Satapathy, Chandra Suresh and Rao, Bheema N and Kumar, Srinivas S and Raj, Dharma C and Rao, Malleswara V and Sarma, K G V},
   publisher = {Springer India},
  
  
   pages = {421--428},
   year = {2016},
   keywords = {CNT,First principle,ITRS,Incapacitation,MOSFET,NGEF,area:nanowires,area:semi,industrial},
   area = {nanowires,semi}
   doi = {10.1007/978-81-322-2728-1_38},
   url = {http://link.springer.com/10.1007/978-81-322-2728-1_38},
}
Mayank Chakraverty & H.M. Kittur, Microstructure processing and micromagnetic simulations of magnetic tunnel junction based low power magnetic memories, pp. 1--6 (2014)
Abstract    BibTeX    DOI: 10.1109/AICERA.2014.6908165   
Abstract: Magnetoresistive memory (MRAM) is one of the forerunners of the nanotechnology enabled memories lined to replace the traditional memories like Flash, DRAM and SRAM. MRAMs are based on the phenomenon of spin dependent tunneling in magnetic tunnel junctions (MTJs). It stores data in the magnetization of a magnetic layer as opposed to electrical charge in conventional RAMs. Yet the read-out of MRAM is electrical. It is claimed to offer something close to the speed of SRAM, with a density approaching that of single-transistor DRAM and the ability to store information when power is removed, like flash memory or EEPROM. This paper works out the microstructure processing steps in the fabrication of an MTJ based MRAM cell in two distinct versions. The technicalities of the two MTJ based MRAM cell configurations have been discussed in this paper. The I-V characteristics and TMR ratios of the widely investigated Fe/MgO/Fe magnetic tunnel junction have also been evaluated using first principle LSDA band-structure calculations. Micro magnetic simulations of the MTJ demonstrate the magnetic switching in the two ferromagnetic layers. The resulting hysteresis loop has been presented at the end of the paper.
BibTeX:
@inproceedings{Chakraverty2014a,
   title = {Microstructure processing and micromagnetic simulations of magnetic tunnel junction based low power magnetic memories},
   author = {Chakraverty, Mayank and Kittur, H M},
   booktitle = {Emerging Research Areas: Magnetics, Machines and Drives (AICERA/iCMMD), 2014 Annual International Conference on},
  
  
  
  
  
   pages = {1--6},
   year = {2014},
   keywords = {Copper,DRAM,EEPROM,Fe-MgO-Fe,I-V characteristics,Iron,MRAM devices,MTJ based MRAM cell,Magnetic fields,Magnetic tunneling,Magnetization,Magnetoresistive RAM,SRAM,TMR ratios,Transistors,Tunneling magnetoresistance,area:nvm,area:semi,area:spintronics,ferromagnetic layers,first principle LSDA band-structure calculations,flash memory,hysteresis loop,iron,low-power electronics,magnesium compounds,magnetic switching,magnetic tunnel junction,magnetic tunnel junctions,magnetic tunnelling,magnetisation,magnetization,magnetoresistive memory,micro magnetic simulations,microfabrication,microstructure processing steps,nanotechnology enabled memories,spin dependent tunneling,tunnel magnetoresistance},
   area = {nvm,semi,spintronics}
   doi = {10.1109/AICERA.2014.6908165},
  
}
Mayank Chakraverty & Harish M. Kittur, Comparison of tunnel currents through SiO2, HfO2, Ta2O5, ZrO2 and Dy2O3 dielectrics in MOS devices for ultra large scale integration using first principle calculations, pp. 1--6 (2013)
Abstract    BibTeX    DOI: 10.1109/AICERA-ICMiCR.2013.6575936   
Abstract: The work presented in this paper focuses on the effects of high leakage current in field effect transistors and the possible ways to play down with the leakage currents. This paper combines density functional theory and non equilibrium Green's function formalism to perform atomic scale calculation of tunnel currents through SiO2, HfO2, Ta2O5ZrO2 and DY2O3 dielectrics in MOSFETs. The tunnel currents for different bias voltages applied to Si/Insulator/Si systems have been obtained along with tunnel conductance v/s bias voltage plots for each system and the plots have been analyzed with reference to the presently used bulk Si/SiO2/Si systems that have SiO2 as the gate dielectric material. The results justify the use of high dielectric constant materials as gate dielectric in FET devices so as to enable further downscaling of MOSFETs with reduced gate leakage currents thereby enabling ultra large scale integration.
BibTeX:
@inproceedings{Chakraverty2013,
   title = {Comparison of tunnel currents through SiO2, HfO2, Ta2O5, ZrO2 and Dy2O3 dielectrics in MOS devices for ultra large scale integration using first principle calculations},
   author = {Chakraverty, Mayank and Kittur, Harish M},
   booktitle = {Emerging Research Areas and 2013 International Conference on Microelectronics, Communications and Renewable Energy (AICERA/ICMiCR), 2013 Annual International Conference on},
  
  
  
  
  
   pages = {1--6},
   year = {2013},
   keywords = {CMOS,Gate Leakage current,MOSFET,MOSFETS,Silicon,area:interfaces,area:semi,dielectrics,drive current,insulators,leakage currents,logic gates,threshold voltage,transconductance,tunnel current},
   area = {interfaces,semi}
   doi = {10.1109/AICERA-ICMiCR.2013.6575936},
  
}
Mayank Chakraverty & H.M. Kittur, Evidence of hysteresis from first principle DFT simulations of I-V curves in Pt/TiO(2-x) - TiO2/Pt memristive systems, pp. 379--383 (2012)
Abstract    BibTeX    DOI: 10.1109/ICDCSyst.2012.6188749   
Abstract: The memristor is an electrical circuit element that is similar to a resistor but has the potential to maintain state between turning power on and off. These memristors are about half the size of the transistors found in current flash storage technology, allowing capacity of these devices to double. This paper discusses the basics of memristors, which is an electrical circuit element, and presents the first principle simulation results of Pt/TiO2-x - TiO2/Pt system where the central region has a boundary separating TiO2-x and TiO2 regions. This barrier is progressively shifted towards the TiO2-x region with applied bias to gradually increase the thickness of TiO2 region. A comparison of the electrical characteristics of the device when the TiO2 region is extended towards TiO2-x region is also presented. The basis of memristive behavior, the nonlinear hysteresis curve of memristor, has been obtained based upon the simulation results.
BibTeX:
@inproceedings{Chakraverty2012,
   title = {Evidence of hysteresis from first principle DFT simulations of I-V curves in Pt/TiO(2-x) - TiO2/Pt memristive systems},
   author = {Chakraverty, Mayank and Kittur, H M},
   booktitle = {Devices, Circuits and Systems (ICDCS), 2012 International Conference on},
  
  
  
  
  
   pages = {379--383},
   year = {2012},
   keywords = {DRAM,I-V curve,Pt-TiO2-x-TiO2-Pt,area:interfaces,electrical characteristics,electrical circuit element,first principle DFT simulations,flash storage technology,hysteresis,memristive systems,memristor,memristors,nonlinear hysteresis curve,platinum,titanium compounds,transistors},
   area = {interfaces}
   doi = {10.1109/ICDCSyst.2012.6188749},
  
}
Mayank Chakraverty & Harish M. Kittur, First Principle Study of Tunnel Currents through CeO2, Y2O3, TiO2 and Al2O3 Dielectrics in MOSFETs for Ultra Large Scale Integration, Advanced Materials Research, Vol. 584 pp. 428--432 (2012)
Abstract    BibTeX    DOI: 10.4028/www.scientific.net/AMR.584.428   
Abstract: High gate leakage current, as a central problem, has decelerated the downscaling of minimum feature size of the field effect transistors In this paper, a combination of density functional theory and non equilibrium Green's function formalism has been applied to the atomic scale calculation of the tunnel currents through CeO2, Y2O3, TiO2 and Al2O3 dielectrics in MOSFETs. The tunnel currents for different bias voltages applied to Si/Insulator/Si systems have been obtained along with tunnel conductance v/s bias voltage plots for each system. The results are in agreement to the use of high dielectric constant materials as gate dielectric so as to enable further downscaling of MOSFETs with reduced gate leakage currents thereby enabling ultra large scale integration. When used as dielectric, TiO2 exhibits extremely low tunnel currents followed by Y2O3 while CeO2 and Al2O3 exhibit high tunnel currents through them at certain bias voltages.
BibTeX:
@article{Chakraverty2012a,
   title = {First Principle Study of Tunnel Currents through CeO2, Y2O3, TiO2 and Al2O3 Dielectrics in MOSFETs for Ultra Large Scale Integration},
   author = {Chakraverty, Mayank and Kittur, Harish M},
  
   journal = {Advanced Materials Research},
  
  
   volume = {584},
  
   pages = {428--432},
   year = {2012},
   keywords = {CMOS,FIBL,MOSFET,ULSI,area:interfaces,area:semi,leakage current,threshold voltage},
   area = {interfaces,semi}
   doi = {10.4028/www.scientific.net/AMR.584.428},
  
}
Mayank Chakraverty & Harish M. Kittur, First Principle Simulations of Fe/MgO/Fe Magnetic Tunnel Junctions for Applications in Magnetoresistive Random Access Memory Based Cell Phone Architectures, International Journal of Micro and Nano Systems, Vol. 2(1), pp. 1--6 (2011)
Abstract    BibTeX    URL: http://www.academia.edu/4344549/   
Abstract: Fe/MgO/Fe magnetic tunnel junctions (MTJs) have been reported to have very high tunnel magnetoresistance (TMR) ratios. In this work, we present the results of First Principle simulations of Fe/MgO/Fe MTJs with LSDA as the exchange correlation. The I-V characteristics in the antiparallel magnetization state exhibit strong features. The bias dependence of the TMR ratio shows nearly 100% TMR ratios for bias voltages up to 1.5 Volts. The MgO thickness dependence of the tunnel resistance shows the expected exponential increase in the tunnel resistance. The write energy per bit and power consumption have been computed for a bias voltage of 0.5 Volts. The Fe/MgO/Fe MTJs are the most widely used MTJs, integrated with NMOS transistors, in the form of MTJ based Magnetoresistive Random Access Memory (MRAM) which is an advanced memory technology operating at the nano scale. MRAMs are spintronic devices.
BibTeX:
@article{Chakraverty2011,
   title = {First Principle Simulations of Fe/MgO/Fe Magnetic Tunnel Junctions for Applications in Magnetoresistive Random Access Memory Based Cell Phone Architectures},
   author = {Chakraverty, Mayank and Kittur, Harish M},
  
   journal = {International Journal of Micro and Nano Systems},
  
  
   volume = {2},
   number = {1},
   pages = {1--6},
   year = {2011},
   keywords = {LSDA,MTJ,TMR,area:interfaces,area:nvm,area:spintronics,first Principle,spin},
   area = {interfaces,nvm,spintronics}
  
   url = {http://www.academia.edu/4344549/},
}
Mayank Chakraverty, H.M. Kittur & P.A. Kumar, First Principle Simulations of Various Magnetic Tunnel Junctions for Applications in Magnetoresistive Random Access Memories, Nanotechnology, IEEE Transactions on, Vol. 12(6), pp. 971--977 (2013)
Abstract    BibTeX    DOI: 10.1109/TNANO.2013.2274902   
Abstract: This paper reports the first principle simulations of Fe/MgO/Fe, Fe/Y2O3/Fe, Fe/HfO2/Fe, and Fe/Al2O3/Fe magnetic tunnel junctions (MTJs). From the device-level and circuit-level simulations carried out in this paper, the Fe/MgO/Fe configuration has been found to be the best. From the device-level simulations, all the four configurations of MTJs have been compared with regards to the bias dependence of tunnel magnetoresistance ratios (TMRs), insulator thickness dependence of TMR, and insulator thickness dependence of parallel and antiparallel state resistances. Finally, from the circuit-level simulations, the static and switching power dissipations have been computed along with the delay time estimation.
BibTeX:
@article{Chakraverty2013a,
   title = {First Principle Simulations of Various Magnetic Tunnel Junctions for Applications in Magnetoresistive Random Access Memories},
   author = {Chakraverty, Mayank and Kittur, H M and Kumar, P A},
  
   journal = {Nanotechnology, IEEE Transactions on},
  
  
   volume = {12},
   number = {6},
   pages = {971--977},
   year = {2013},
   keywords = {Atomic layer deposition,Density functional theory (DFT),Fe-Al2O3-Fe,Fe-HfO2-Fe,Fe-MgO-Fe,Fe-Y2O3-Fe,Insulators,Iron,MRAM,Magnetic separation,Magnetic tunneling,Resistance,Tunneling magnetoresistance,antiparallel state resistances,area:interfaces,area:nvm,area:semi,area:spintronics,circuit-level simulations,device-level simulations,hafnium compounds,insulator thickness dependence,iron,local spin density approximation (LSDA),magnesium compounds,magnetic tunnel junction (MTJ),magnetic tunnel junctions,magnetoresistive random access memories,random-access storage,tunnel magnetoresistance ratios,yttrium compounds},
   area = {interfaces,nvm,semi,spintronics}
   doi = {10.1109/TNANO.2013.2274902},
  
}
Mayank Chakraverty, P. Arun Kumar & Harish M. Kittur, Performance Analysis of Fe/SiO2/Fe MTJ and Ni/Al2O3/Ni MTJ based Magnetoresistive Random Access Memories, Journal of VLSI Design Tools & Technology, Vol. 2(2), pp. 1 (2012)
Abstract    BibTeX    URL: http://journal.uniten.edu.my/ojs3/index.php/ijecct/article/view/137   
Abstract: This paper reports the first principle simulations of Fe/SiO2/Fe and Ni/Al2O3/Ni magnetic tunnel junctions (MTJs). A performance analysis has been done based upon the device-level simulations of the two magnetic tunnel junctions followed by the circuit level simulations of magnetoresistive random access memory (MRAM) cell operating with the two MTJs respectively. From the device-level simulations, the two MTJs have been compared with regard to the bias dependence of TMR ratios, insulator thickness dependence of TMR ratios and insulator thickness dependence of parallel and anti-parallel state resistances taking the relative magnetizations of the two ferromagnetic films of the MTJs into consideration. From the circuit-level simulations, the static and switching power dissipations have been computed along with the delay time estimation.
BibTeX:
@article{Chakraverty2012b,
   title = {Performance Analysis of Fe/SiO2/Fe MTJ and Ni/Al2O3/Ni MTJ based Magnetoresistive Random Access Memories},
   author = {Chakraverty, Mayank and Kumar, P Arun and Kittur, Harish M},
  
   journal = {Journal of VLSI Design Tools & Technology},
  
  
   volume = {2},
   number = {2},
   pages = {1},
   year = {2012},
   keywords = {MTJ,area:interfaces,area:nvm,area:spintronics,spin},
   area = {interfaces,nvm,spintronics}
  
   url = {http://journal.uniten.edu.my/ojs3/index.php/ijecct/article/view/137},
}
Anuja Chanana & Santanu Mahapatra, Density functional theory based study of chlorine doped WS2-metal interface, Applied Physics Letters, Vol. 108(10), pp. 103107 (2016)
Abstract    BibTeX    DOI: 10.1063/1.4943267   
Abstract: Investigation of a TMD-metal interface is essential for the effective functioning of monolayer TMD based field effect transistors (FETs). In this work, we employ Density Functional Theory (DFT) calculations to analyze the modulation of the electronic structure of monolayer WS2 with chlorine doping and the relative changes in the contact properties when interfaced with gold and palladium. We initially examine the atomic and electronic structures of pure and doped monolayer WS2 supercell and explore the formation of mid gap states with band splitting near the conduction band edge. Further we analyze the contact nature of the pure supercell with Au and Pd. We find that while Au is physiosorped and forms n-type contact, Pd is chemisorped and forms p-type contact with a higher valence electron density. Next, we study the interface formed between the Cl-doped supercell and metals and observe a reduction in the Schottky barrier height (SBH) in comparison to the pure supercell. This reduction found is higher for Pd in comparison to Au which is further validated by examining the charge transfer occurring at the interface. Our study confirms that Cl doping is an efficient mechanism to reduce the n-SBH for both Au and Pd which form different types of contact with WS2.
BibTeX:
@article{Chanana2016,
   title = {Density functional theory based study of chlorine doped WS2-metal interface},
   author = {Chanana, Anuja and Mahapatra, Santanu},
  
   journal = {Applied Physics Letters},
  
  
   volume = {108},
   number = {10},
   pages = {103107},
   year = {2016},
   keywords = {Band gap,Charge transfer,Doping,Gold,Interface structure,area:2dmat,area:tmd},
   area = {2dmat,tmd}
   doi = {10.1063/1.4943267},
  
}
Anuja Chanana & Santanu Mahapatra, Theoretical Insights to Niobium-Doped Monolayer MoS2-Gold Contact, IEEE Transactions on Electron Devices, Vol. 62(7), pp. 2346--2351 (2015)
Abstract    BibTeX    DOI: 10.1109/ted.2015.2433931   
Abstract: We report a first principles study of the electronic properties for a contact formed between Nb-doped monolayer MoS2 and gold for different doping concentrations. We first focus on the shift of energy levels in band structure and the density of states with respect to the Fermi level for a geometrically optimized 5x5 MoS2 supercell for both pristine and Nb-doped structures. The doping is achieved by substituting Mo atoms with Nb atoms at random positions. It is observed that for an experimentally reported sheet hole doping concentration of (1.8)10ˆ14 cmˆ-2, the pristine MoS2 converts to degenerate p-type semiconductor. Next, we interface this supercell with six layers of (111) cleaved surface of gold to investigate the contact nature of MoS2-Au system. By careful examination of projected band structure, projected density of states, effective potential and charge density difference, we demonstrate that the Schottky barrier nature observed for pure MoS2-Au contact can be converted from n-type to p-type by efficient Nb doping.
BibTeX:
@article{Chanana2015,
   title = {Theoretical Insights to Niobium-Doped Monolayer MoS2-Gold Contact},
   author = {Chanana, Anuja and Mahapatra, Santanu},
  
   journal = {IEEE Transactions on Electron Devices},
  
   publisher = {Institute of Electrical & Electronics Engineers (IEEE)},
   volume = {62},
   number = {7},
   pages = {2346--2351},
   year = {2015},
   keywords = {MoS2,Schottky barrier,TMD,area:graphene,area:interfaces,doping,niobium},
   area = {graphene,interfaces}
   doi = {10.1109/ted.2015.2433931},
  
}
Anuja Chanana & Santanu Mahapatra, First principles study of metal contacts to monolayer black phosphorous, Journal of Applied Physics, Vol. 116(20), pp. 204302 (2014)
Abstract    BibTeX    DOI: 10.1063/1.4901998   
Abstract: Atomically thin layered black phosphorous (BP) has recently appeared as an alternative to the transitional metal di chalcogenides for future channel material in a MOS transistor due to its lower carrier effective mass. Investigation of the electronic property of source/drain contact involving metal and two-dimensional material is essential as it impacts the transistor performance. In this paper we perform a systematic and rigorous study to evaluate the Ohmic nature of the side-contact formed by the monolayer BP (mBP) and metals (gold, titanium and palladium), which are commonly used in experiments. Employing the Density Functional Theory (DFT), we analyse the potential barrier, charge transfer and atomic orbital overlap at the metal-mBP interface in an optimized structure to understand how efficiently carriers could be injected from metal contact to the mBP channel. Our analysis shows that gold forms a Schottky contact with a higher tunnel barrier at the interface in comparison to the titanium and palladium. mBP contact with palladium is found to be purely Ohmic, where as titanium contact demonstrates an intermediate behaviour.
BibTeX:
@article{Chanana2014,
   title = {First principles study of metal contacts to monolayer black phosphorous},
   author = {Chanana, Anuja and Mahapatra, Santanu},
  
   journal = {Journal of Applied Physics},
  
  
   volume = {116},
   number = {20},
   pages = {204302},
   year = {2014},
   keywords = {MOS transistor,Ohmic contact,Schottky barrier,area:2dmat,area:interfaces,black phosphorous,metal contacts},
   area = {2dmat,interfaces}
   doi = {10.1063/1.4901998},
  
}
Bagavathi Chandrasekara, Nanotransistors from metal and metalloid compound nanotubes, International Journal of Scientific & Engineering Research, Vol. 4(2), pp. 1--4 (2013)
Abstract    BibTeX    URL: http://www.academia.edu/4409843/   
Abstract: The escalating trend of chip integration and miniaturization has dared the designers to seek to a nascent phenomenon to save the Moore's law. Due to continuous reduction in device size, the so-far-unseen quantum effects have dominated the device physics. The solution to this crisis is nanoelectronics. Nano structures are used to develop new devices by utilizing the quantum effects. III group compounds have been known for their special properties as semiconductors in electronics. By including nanoscale nature with III group compounds, greater advantages can be obtained. III group nitride nanotubes have been investigated in many works. The nanotubes under discussion are boron nitride nanotubes and gallium nitride nanotubes. The phenomenon used for analysis in this work is Density Functional Theory (DFT). The characteristics of a device can be deduced from the electronic cloud structure around the device through density functional theory. In this work, III group nitride nanotubes are employed as transistor channels and their characteristics are scrutinized through simulation studies.
BibTeX:
@article{Chandrasekara2013,
   title = {Nanotransistors from metal and metalloid compound nanotubes},
   author = {Chandrasekara, Bagavathi},
  
   journal = {International Journal of Scientific & Engineering Research},
  
  
   volume = {4},
   number = {2},
   pages = {1--4},
   year = {2013},
   keywords = {area:nanotubes,boron-nitride,density functional theory,gallium nitride,nanotube,nanotube transistor,simulation of nanomaterials,third group nanotubes,transistor},
   area = {nanotubes}
  
   url = {http://www.academia.edu/4409843/},
}
Bagavathi Chandrasekara & K.A. Narayanankutty, Gallium Nitride Nanotube and its Application as Transistors, International Journal of Computer Applications, Vol. 47 pp. 888--975 (2012)
Abstract    BibTeX    DOI: 10.5120/7259-0347   
Abstract: In search of opto-electronic nano materials, we often come across Gallium Nitride nanotubes (GaN-NT) with excellent electrical and optical characteristics. Gallium Nitride nanotubes are predominantly semiconducting and have been less explored in its application as a transistor channel through Density Functional Theory (DFT). Comparing Gallium Nitride nanotubes with Boron Nitride nanotubes (BN-NT) and Carbon nanotubes (CNT), we have obtained distinguishing features of Gallium Nitride nanotubes. In this work, Transistor simulation with Gallium Nitride nanotubes has been reported with the nanotube as channel. Properties of various configurations of nanotubes are compared among Carbon, Boron Nitride and Gallium Nitride nanotubes.
BibTeX:
@article{Chandrasekara2012,
   title = {Gallium Nitride Nanotube and its Application as Transistors},
   author = {Chandrasekara, Bagavathi and Narayanankutty, K A},
  
   journal = {International Journal of Computer Applications},
  
  
   volume = {47},
  
   pages = {888--975},
   year = {2012},
   keywords = {Boron Nitride nanotubes,Density Functional Theory (DFT),GaN nanotube transistor,Gallium Nitride nanotubes,area:nanotubes,bond rotation},
   area = {nanotubes}
   doi = {10.5120/7259-0347},
  
}
Po-Hao Chang, Haiying Liu & Branislav K. Nikolic, First-principles versus semi-empirical modeling of global and local electronic transport properties of graphene nanopore-based sensors for DNA sequencing, Journal of Computational Electronics, Vol. 13(4), pp. 847--856 (2014)
Abstract    BibTeX    DOI: 10.1007/s10825-014-0614-8   
Abstract: Using first-principles quantum transport simulations, based on the nonequilibrium Green function formalism combined with density functional theory (NEGF+DFT), we examine changes in the total and local electronic currents within the plane of graphene nanoribbon with zigzag edges (ZGNR) hosting a nanopore which are induced by inserting a DNA nucleobase into the pore. We find a sizable change of the zero-bias conductance of two-terminal ZGNR + nanopore device after the nucleobase is placed into the most probable position (according to molecular dynamics trajectories) inside the nanopore of a small diameter D=1.2 nm. Although such effect decreases as the nanopore size is increased to D=1.7 nm, the contrast between currents in ZGNR + nanopore and ZGNR + nanopore + nucleobase systems can be enhanced by applying a small bias voltage Vbtextless0.1 V. This is explained microscopically as being due to DNA nucleobase-induced modification of spatial profile of local current density around the edges of ZGNR. We repeat the same analysis using NEGF combined with self-consistent charge density functional tight-binding (NEGF+SCC-DFTB) or self-consistent extended Huckel (NEGF+SC-EH) semi-empirical methodologies. The large discrepancy we find between the results obtained from NEGF+DFT vs. those obtained from NEGF+SCC-DFTB or NEGF+SC-EH approaches could be of great importance when selecting proper computational algorithms for in silico design of optimal nanoelectronic sensors for rapid DNA sequencing.
BibTeX:
@article{Chang2014,
   title = {First-principles versus semi-empirical modeling of global and local electronic transport properties of graphene nanopore-based sensors for DNA sequencing},
   author = {Chang, Po-Hao and Liu, Haiying and Nikolic, Branislav K},
  
   journal = {Journal of Computational Electronics},
  
   publisher = {Springer US},
   volume = {13},
   number = {4},
   pages = {847--856},
   year = {2014},
   keywords = {DNA sequencing,First-principles quantum transport,Graphene nanoribbons,Nanopores,application,area:graphene},
   area = {graphene}
   doi = {10.1007/s10825-014-0614-8},
  
}
Po-Hao Chang, Troels Markussen, Søren Smidstrup, Kurt Stokbro & Branislav K. Nikolić, Nonequilibrium spin texture within a thin layer below the surface of current-carrying topological insulator Bi2Se3: A first-principles quantum transport st, Physical Review B, Vol. 92(20), pp. 201406 (2015)
Abstract    BibTeX    DOI: 10.1103/PhysRevB.92.201406   
Abstract: We predict that unpolarized charge current injected into a ballistic thin film of prototypical topological insulator (TI) Bi2Se3 will generate a noncollinear spin texture S(r) on its surface. Furthermore, the nonequilibrium spin texture will extend into an ≅2-nm-thick layer below the TI surfaces due to penetration of evanescent wave functions from the metallic surfaces into the bulk of TI. Averaging S(r) over a few angstroms along the longitudinal direction defined by the current flow reveals a large component pointing in the transverse direction. In addition, we find an order of magnitude smaller out-of-plane component when the direction of injected current with respect to Bi and Se atoms probes the largest hexagonal warping of the Dirac-cone dispersion on the TI surface. Our analysis is based on an extension of the nonequilibrium Green's functions combined with density functional theory (NEGF+DFT) to situations involving noncollinear spins and spin-orbit coupling. We also demonstrate how DFT calculations with a properly optimized local orbital basis set can precisely match putatively more accurate calculations with a plane-wave basis set for the supercell of Bi2Se3.
BibTeX:
@article{Chang2015,
   title = {Nonequilibrium spin texture within a thin layer below the surface of current-carrying topological insulator Bi2Se3: A first-principles quantum transport st},
   author = {Chang, Po-Hao and Markussen, Troels and Smidstrup, Søren and Stokbro, Kurt and Nikolić, Branislav K.},
  
   journal = {Physical Review B},
  
   publisher = {American Physical Society},
   volume = {92},
   number = {20},
   pages = {201406},
   year = {2015},
   keywords = {QWpaper,Topological insulators,area:spin,area:spintronics},
   area = {spin,spintronics}
   doi = {10.1103/PhysRevB.92.201406},
  
}
Mausumi Chattopadhyaya, Md. Mehboob Alam, Debasis Sarkar & Swapan Chakrabarti, Electrically Controlled Eight-Spin-Qubit Entangled-State Generation in a Molecular Break Junction, ChemPhysChem, Vol. 15(9), pp. 1747 (2014)
Abstract    BibTeX    DOI: 10.1002/cphc.201400029   
Abstract: The generation of spin-based multi-qubit entangled states in the presence of an electric field is one of the most challenging tasks in current quantum-computing research. Such examples are still elusive. By using non-equilibrium Green's function-based quantum-transport calculations in combination with non-collinear spin density functional theory, we report that an eight-spin-qubit entangled state can be generated with the high-spin state of a dinuclear Fe(II) complex when the system is placed in a molecular break junction. The possible gate operation scheme, gating time, and decoherence issues have been carefully addressed. Furthermore, our calculations reveal that the preservation of the high spin state of this complex is possible if the experimentalists keep the electric-field strength below 0.78 $V nmˆ-1$. In brief, the present study offers a unique way to realize the first example of a multi-qubit entangled state by electrical means only.
BibTeX:
@article{Chattopadhyaya2014a,
   title = {Electrically Controlled Eight-Spin-Qubit Entangled-State Generation in a Molecular Break Junction},
   author = {Chattopadhyaya, Mausumi and Alam, Md. Mehboob and Sarkar, Debasis and Chakrabarti, Swapan},
  
   journal = {ChemPhysChem},
  
   publisher = {WILEY-VCH Verlag},
   volume = {15},
   number = {9},
   pages = {1747},
   year = {2014},
   keywords = {NEGF,area:molecular electronics,area:spintronics,entanglement,quantum interference,quantum transport},
   area = {molecular electronics,spintronics}
   doi = {10.1002/cphc.201400029},
  
}
Mausumi Chattopadhyaya, Md. Mehboob Alam, Sabyasachi Sen & Swapan Chakrabarti, Electrostatic Spin Crossover and Concomitant Electrically Operated Spin Switch Action in a Ti-Based Endohedral Metallofullerene Polymer, Physical Review Letters, Vol. 109(25), pp. 257204---- (2012)
Abstract    BibTeX    DOI: 10.1103/PhysRevLett.109.257204   
Abstract: Herein, we predict that a 1D chain of Ti@C32-C2-Ti@C32 (TEMF) will act as a spin switch in the presence of an electric field. The spin resolved density of states analyses reveal that, surprisingly, both the low- and high-spin states of TEMF are half-metal; however, the metallic density of states comes from the opposite spin channels of the two spin states. More remarkably, it is found that the electric field driven spin crossover between the low and high state in TEMF is achievable at field strength 1.04 V/nm, which eventually leads to the realization of the first ever electrically operated spin switch device.
BibTeX:
@article{Chattopadhyaya2012,
   title = {Electrostatic Spin Crossover and Concomitant Electrically Operated Spin Switch Action in a Ti-Based Endohedral Metallofullerene Polymer},
   author = {Chattopadhyaya, Mausumi and Alam, Md. Mehboob and Sen, Sabyasachi and Chakrabarti, Swapan},
  
   journal = {Physical Review Letters},
  
   publisher = {American Physical Society},
   volume = {109},
   number = {25},
   pages = {257204----},
   year = {2012},
   keywords = {area:fullerenes,area:molecular electronics,area:spintronics,atomic chain,fullerenes,molecular electronics,spin switch},
   area = {fullerenes,molecular electronics,spintronics}
   doi = {10.1103/PhysRevLett.109.257204},
  
}
Mausumi Chattopadhyaya, Sabyasachi Sen, Md. Mehboob Alam & Swapan Chakrabarti, On site Coulomb repulsion dominates over the non-local Hartree-Fock exchange in determining the band gap of polymers, Journal of Physics and Chemistry of Solids, Vol. 75(2), pp. 212--223 (2014)
Abstract    BibTeX    DOI: 10.1016/j.jpcs.2013.09.018   
Abstract: The present study deals with the relative performance of the various density functional approaches in evaluating the band gap of polymer materials. Several density functional approximations that includes pure generalized gradient approximated (GGA) functional, meta-GGA, hybrid and range separated hybrid functionals have been used to evaluate the electrical band gap or transport gap of the studied polymers and compared with that obtained using Hubbard U corrected GGA functional (GGA+U). It has been observed that the experimental band gap of the polymers studied is satisfactorily reproducible when GGA+U approach is adopted. The band gap analyses further suggest that range separated hybrid functional, CAM-B3LYP, largely overestimates the band gap of all the polymers studied while the performance of hybrid B3LYP functional and other range separated hybrid functional like HSE is moderate. Better performance of the GGA+U method clearly indicates that short range coulomb correlation plays more significant role over the non-local Hartree-Fock (HF) exchange in determining the electrical band gap of polymer materials. It is also noticeable that the Hubbard U parameter used for the various polymers under consideration is relatively large, indicating the semi-empirical nature of the GGA+U level of calculations. The present finding will help us design new low band gap polymer through estimating band gap by the GGA+U method and this could be very useful for solar cell research.
BibTeX:
@article{Chattopadhyaya2014,
   title = {On site Coulomb repulsion dominates over the non-local Hartree-Fock exchange in determining the band gap of polymers},
   author = {Chattopadhyaya, Mausumi and Sen, Sabyasachi and Alam, Md. Mehboob and Chakrabarti, Swapan},
  
   journal = {Journal of Physics and Chemistry of Solids},
  
  
   volume = {75},
   number = {2},
   pages = {212--223},
   year = {2014},
   keywords = {ab initio calculations,area:materials,electronic structure,polymers},
   area = {materials}
   doi = {10.1016/j.jpcs.2013.09.018},
  
}
Satyendra Singh Chauhan, Pankaj Srivastava & Rajnish Kurchania, Half-Metallicity in Doped Armchair Graphene Nanoribbons - An Ab Initio Approach, Journal of Computational and Theoretical Nanoscience, Vol. 8 pp. 729--735 (2011)
Abstract    BibTeX    DOI: 10.1166/jctn.2011.1745   
Abstract: We present a comprehensive theoretical study based on density functional theory for stability, electronic and transport properties of armchair graphene nanoribbons. We have tested boron, beryllium, lithium, magnesium, fluorine, oxygen and nitrogen as substitutional dopant in the center of armchair graphene nanoribbons. It is observed that oxygen atom as substitutional dopant in armchair graphene nanoribbons is energetically more favorable and it also minimizes the band gap in all tested widths of armchair graphene nanoribbons (AGNRs). Moreover the oxygen doping at the center of ribbon predicts the half-metallicty in AGNRs. The transport properties are found to be influenced by edge doping of oxygen in AGNRs. These substitutional oxygen atoms act as scattering centers for the electronic transport along the nanoribbons. Since transmission is sensitive to O doping, so our results point towards the relative suitability of O doped armchair edge for sensor applications.
BibTeX:
@article{Chauhan2011,
   title = {Half-Metallicity in Doped Armchair Graphene Nanoribbons - An Ab Initio Approach},
   author = {Chauhan, Satyendra Singh and Srivastava, Pankaj and Kurchania, Rajnish},
  
   journal = {Journal of Computational and Theoretical Nanoscience},
  
  
   volume = {8},
  
   pages = {729--735},
   year = {2011},
   keywords = {area:graphene,area:spintronics,doping,graphene nanoribbons,half-metallicity},
   area = {graphene,spintronics}
   doi = {10.1166/jctn.2011.1745},
  
}
Satyendra Singh Chauhan, Pankaj Srivastava & A.K. Shrivastava, Band gap engineering in doped graphene nanoribbons: An ab initio approach, Solid State Communications, Vol. 154(0), pp. 69--71 (2013)
Abstract    BibTeX    DOI: 10.1016/j.ssc.2012.10.030   
Abstract: We present first principle study for stability and electronic properties of armchair graphene nanoribbons (AGNRs). We have investigated the stability and electronic properties of armchair graphene nanoribbons whose edges are doped with (i) s-type elements, Mg (ii) p-type elements, B and S, and (iii) 3d-type TMs, Ti and Mn, atoms using density functional theory. We predict that transition metals as substitutional dopant in AGNRs are energetically more favorable and minimize the band gap. The edges of the AGNRs are chemically more active and they can accommodate appropriate dopants to obtain different electronic properties having the same geometrical structure of the ribbon. Our results suggest that such materials can be used for nanoelectronic and spintronic applications.
BibTeX:
@article{Chauhan2013,
   title = {Band gap engineering in doped graphene nanoribbons: An ab initio approach},
   author = {Chauhan, Satyendra Singh and Srivastava, Pankaj and Shrivastava, A K},
  
   journal = {Solid State Communications},
  
  
   volume = {154},
   number = {0},
   pages = {69--71},
   year = {2013},
   keywords = {area:graphene,band gap,density functional theory,graphene nanoribbons,stability},
   area = {graphene}
   doi = {10.1016/j.ssc.2012.10.030},
  
}
Satyendra Singh Chauhan, Pankaj Srivastava & Ashwani Kumar Shrivastava, Electronic and transport properties of boron and nitrogen doped graphene nanoribbons: an ab initio approach, Applied Nanoscience, Vol. 4 pp. 1--7 (2013)
Abstract    BibTeX    DOI: 10.1007/s13204-013-0220-2   
Abstract: Graphene nanoribbons (GNRs) are expected to display extraordinary properties in the form of nanostructures. The effect of boron and nitrogen substitutional doping at four successive positions on electronic and transport properties of zigzag graphene nanoribbons (ZGNRs) is studied using spin-unpolarized density functional theory. It has been observed that the electronic structures of the doped ZGNRs are different from those of pristine ZGNRs. We have also calculated the transformation energy in the form of total energy. The substitutional boron atom at the nanoribbons edges suppresses the energy band near Fermi level by changing properties of material from metallic to semi-metallic in ZGNRs which can be explained as a consequence of the edge polarization effects. At all doping positions, N-doped ZGNRs are n-type while B-doped ZGNRs are p-type semiconductors. These substitutionally B- and N-doped impurities act as scattering centers for transport in GNRs. Due to unusual properties of these nanomaterials, they can be used in carbon-based nanoelectronics devices.
BibTeX:
@article{Chauhan2013a,
   title = {Electronic and transport properties of boron and nitrogen doped graphene nanoribbons: an ab initio approach},
   author = {Chauhan, Satyendra Singh and Srivastava, Pankaj and Shrivastava, Ashwani Kumar},
  
   journal = {Applied Nanoscience},
  
   publisher = {Springer-Verlag},
   volume = {4},
  
   pages = {1--7},
   year = {2013},
   keywords = {area:graphene,boron,density functional theory,doping,graphene nanoribbons,nitrogen},
   area = {graphene}
   doi = {10.1007/s13204-013-0220-2},
  
}
Satyendra Singh Chauhan, Pankaj Srivastava & Ashwani Kumar Shrivastava, Band Gap Engineering in Zigzag Graphene NanoribbonsAn Ab Initio Approach, Journal of Computational and Theoretical Nanoscience, Vol. 9(8), pp. 1084--1089 (2012)
Abstract    BibTeX    DOI: 10.1166/jctn.2012.2147   
Abstract: We present first principles study based on spin polarized density functional theory for electronic properties of armchair graphene nanoribbons (AGNRs) and Bloch state study in zigzag graphene nanoribbons (ZGNRs) passivated with hydrogen atoms. We have investigated the spin-dependent band structure of zigzag graphene nanoribbons. It is observed that these zigzag ribbons are metallic without spin consideration while band gap opens up when spin included. We have also plotted conduction and valence band Bloch states for various textlessItextgreaterktextless/Itextgreater-points and observed that the two spincomponents are localized on opposite sides of the ribbon.
BibTeX:
@article{Chauhan2012,
   title = {Band Gap Engineering in Zigzag Graphene NanoribbonsAn Ab Initio Approach},
   author = {Chauhan, Satyendra Singh and Srivastava, Pankaj and Shrivastava, Ashwani Kumar},
  
   journal = {Journal of Computational and Theoretical Nanoscience},
  
  
   volume = {9},
   number = {8},
   pages = {1084--1089},
   year = {2012},
   keywords = {Bloch states,area:graphene,area:spintronics,armchair,band gap,electronic properties,stability,zigzag},
   area = {graphene,spintronics}
   doi = {10.1166/jctn.2012.2147},
  
}
Satyendra Singh Chauhan, Pankaj Srivastava & A.K. Shrivastava, Effect of Vacancy on Electronic and Transport Properties of Graphene Nanoribbons: An Ab Initio Approach, Journal of Computational and Theoretical Nanoscience, Vol. 9(12), pp. 2215--2216 (2012)
Abstract    BibTeX    DOI: 10.1166/jctn.2012.2641   
Abstract: We report a spin-unpolarized density functional theory study of electronic and transport properties of zigzag graphene nanoribbons (ZGNRs) defected with one and two vacancy atoms. The pristine and vacancy defected structures of 8 ZGNRs are found to be metallic. The one atom vacancy ZGNRs is energetically more stable. The localized states appear when there are vacancies inside the ZGNRs, which affects its transmission. In case of two vacancies in the ZGNRs the additional peak in DOS is observed close to the Fermi level and the transmission decreases further. Hence, our results point towards the relative suitability of these materials in nanoelectronics applications.
BibTeX:
@article{Chauhan2012a,
   title = {Effect of Vacancy on Electronic and Transport Properties of Graphene Nanoribbons: An Ab Initio Approach},
   author = {Chauhan, Satyendra Singh and Srivastava, Pankaj and Shrivastava, A K},
  
   journal = {Journal of Computational and Theoretical Nanoscience},
  
  
   volume = {9},
   number = {12},
   pages = {2215--2216},
   year = {2012},
   keywords = {area:graphene,defect,electronic,graphene nanoribbons,metallic,stability,transport},
   area = {graphene}
   doi = {10.1166/jctn.2012.2641},
  
}
An-Bang Chen, Xue-Feng Wang, P. Vasilopoulos, Ming-Xing Zhai & Yu-Shen Liu, Spin-dependent ballistic transport properties and electronic structures of pristine and edge-doped zigzag silicene nanoribbons: large magnetoresistance, Physical Chemistry Chemical Physics, Vol. 16(11), pp. 5113 (2014)
Abstract    BibTeX    DOI: 10.1039/c3cp55447c   
Abstract: The electronic structure and conductance of substitutionally edge-doped zigzag silicene nanoribbons (ZSiNRs) are investigated using the nonequilibrium Green's function method combined with the density functional theory. Two-probe systems of ZSiNRs in both ferromagnetic and antiferromagnetic states are considered. Doping effects of elements from groups III and V, in a parallel or antiparallel magnetic configuration of the two electrodes, are discussed. By switching on and off the external magnetic field, we may convert the metallic ferromagnetic ZSiNRs into insulating antiferromagnetic ZSiNRs. In the ferromagnetic state, even- or odd-width ZSiNRs exhibit a drastically different magnetoresistance. In an odd-width edge-doped ZSiNR a large magnetoresistance occurs compared to that in a pristine ZSiNR. The situation is reversed in even-width ZSiNRs. These phenomena result from the drastic change in the conductance in the antiparallel configuration.
BibTeX:
@article{Chen2014,
   title = {Spin-dependent ballistic transport properties and electronic structures of pristine and edge-doped zigzag silicene nanoribbons: large magnetoresistance},
   author = {Chen, An-Bang and Wang, Xue-Feng and Vasilopoulos, P and Zhai, Ming-Xing and Liu, Yu-Shen},
  
   journal = {Physical Chemistry Chemical Physics},
  
   publisher = {Royal Society of Chemistry (RSC)},
   volume = {16},
   number = {11},
   pages = {5113},
   year = {2014},
   keywords = {area:graphene,area:spintronics,electronic structure,magnetoresistance,nanoribbon,silicene,spintronics,transport},
   area = {graphene,spintronics}
   doi = {10.1039/c3cp55447c},
  
}
Changpeng Chen, Ziqing Zhu, Dace Zha, Meilan Qi & Jinping Wu, The magnetic and transport properties of edge passivated silicene nanoribbon by Mn atoms, Chemical Physics Letters, Vol. 646 pp. 148--152 (2016)
Abstract    BibTeX    DOI: 10.1016/j.cplett.2016.01.027    URL: http://linkinghub.elsevier.com/retrieve/pii/S0009261416000403   
Abstract: The effect of chemical doping on the ZSiNRs with Mn as passivating element replacing H atoms at one edge are investigated by first-principles calculations. The structures optimized in the typical ferromagnetic and antiferromagnetic coupling show that the system leads to an AFM state and achieve half-metallic properties. Also, our first principle approach based on the Keldysh non-equilibrium Green's function method gives the spin-dependent transport properties of the device. When the system changes from parallel to antiparallel configuration. The spin-up current increases rapidly while the spin-up current is still depressed. Further, it is found that the system is a quite good spin filtering device with nearly 80% spin filtering efficiency at a wide bias voltage region and therefore suitable for applications. The mechanisms for these phenomena are proposed in detail.
BibTeX:
@article{Chen2016,
   title = {The magnetic and transport properties of edge passivated silicene nanoribbon by Mn atoms},
   author = {Chen, Changpeng and Zhu, Ziqing and Zha, Dace and Qi, Meilan and Wu, Jinping},
  
   journal = {Chemical Physics Letters},
  
   publisher = {Elsevier B.V.},
   volume = {646},
  
   pages = {148--152},
   year = {2016},
   keywords = {000review,Silicene nanoribbons,area:2dmat,area:spin},
   area = {2dmat,spin}
   doi = {10.1016/j.cplett.2016.01.027},
   url = {http://linkinghub.elsevier.com/retrieve/pii/S0009261416000403},
}
Jie Chen, Xue-Feng Wang, Panagiotis Vasilopoulos, An-Bang Chen & Jian-Chun Wu, Single and Multiple Doping Effects on Charge Transport in Zigzag Silicene Nanoribbons, ChemPhysChem, Vol. 15(13), pp. 2701--2706 (2014)
Abstract    BibTeX    DOI: 10.1002/cphc.201402171   
Abstract: A non-equilibrium Green's function technique combined with density functional theory is used to study the spin-dependent electronic band structure and transport properties of zigzag silicene nanoribbons (ZSiNRs) doped with aluminum (Al) or phosphorus (P) atoms. The presence of a singl