# Sentaurus Materials Workbench Reference Manual¶

## Introduction¶

Sentaurus Materials Workbench helps you to create material references and to set up input files for atomistic calculations using DFT calculations, or empirical potentials, or both. It can automate defect generation and includes several techniques and recipes to increase the accuracy of calculations. Furthermore, from the atomistic calculation results, Sentaurus Materials Workbench analyzes the results and generates the Sentaurus model parameters that can be used for different TCAD tools, but in particular for dopant diffusion and reaction simulations with Sentaurus Process, and band structure generation needed for Sentaurus Device.

Note

The SMW scripts need to import the package explicitly. In other words, be sure to include a from SMW import * at the beginning of the scripts.

There are different modules or workflows under Sentaurus Materials Workbench. The following lists provides a list of its main capabilities.

## Material specifications¶

Using MaterialSpecifications objects you can define computational settings for your calculations. Sentaurus Materials Workbench comes with a MaterialSpecificationsDatabase with predefined MaterialSpecifications for industry relevant materials. This database should be the starting point for most applications.

## Bandstructure calibration¶

The BandstructureCalibration class extract band structure parameters such as effective masses “k.p” parameters used in Sentaurus tools from first principle calculations. Typical outflow for bandstructure calibration is outlined as follows:

1. A nanowire are built by SMW, and its band structure are calculated by first principle. Here the nanowire can have different cross-sections such as circular cross section with a given diameter, and rectangular cross-sections with given width and heights. The nanowire surface is passivated by Hydrogen atoms.
2. Nanowire with the same shape are created and band structures are calculated with Sentaurus tools. Here the Sde are used to create the nanowire geometry, and SBand are used to calculate band structure. bulk Silicon effective masses are used as initial parameters.
3. SMW adjust the effective masses iteratively until the band structure from SBand match the first principle band structures.

The BandstructureCalibration class can consider Silicon nanowires with different type of cross-sections using CircularNanowireParameters and RectangularNanowireParameters. Both conduction band and valence band parameters can be fitted using NanowireEffectiveMassModel and NanowireKDotPModel.

## Single defect specification and convergence studies¶

For an overview of how to specify particular defects and perform convergence studies you can read Notes.

The available classes are:

## Band diagram extraction¶

The class BandDiagramExtraction extract band diagram from first principle calculations of multilayer 2D structures. The averaged conduction/valence bandedge, bandgaps and work functions/electron affinity in each layer can be extracted. To extract work functions, vacuum energy needs to be calculated. In order to calculate vacuum energy for every layer, the multilayer structure are divided into single layers with vacuum. The outflow for band diagram extraction is outlined as follows:

1. Built a multilayer 2D structure. Single layers are also created corresponding to each individual layers in the multilayer structure.
2. Perform First principle calculation for multilayer and single layers. Banddiagram related properties such as effective potential, chemical potential, fat bandstructure, projected density of states are calculated.
3. Extract vacuum energy, chemical potential, bandedges.

## Defect characterization and migration¶

A typical outflow for defect characterization and diffusion, is outlined as follows:

1. A reference system is created or used. Users set up DFT or force-field calculation input files for the reference host materials with no defect, perform convergence analysis, and find the proper setup that generates well converged results. Using this reference setup, users obtain the optimized lattice parameters and atomic positions. The ChargedPointDefect can be used to provide a structured and automated way to perform such convergence studies.
2. Alternative, users can utilize a precalculated material reference already available in the Material specifications. This is the suggested start for faster, simpler calculations.
3. Sentaurus Materials Workbench takes this reference setup and, as requested by the user, generates the calculation procedures for various possible defect structures in the supported crystal structures, running them as different tasks. It also generates the proper tasks for the lattice vibrational mode frequencies of the defect structures and transition states.
4. Sentaurus Materials Workbench can also generate the migration paths between the above-obtained stable defect structures as instructed by users, and submits the path optimization nudged elastic band (NEB) tasks. It also checks the convergence and consistency of such calculations.
5. Finally, Sentaurus Materials Workbench compiles the atomistic results and calculates the formation energies, migration energies, vibrational entropies and other related quantities. With such information it calculates the Sentaurus Process continuum and KMC model parameters from all of the DFT results.
6. Sentaurus Materials Workbench compiles the atomistic results and calculates the formation energies. Sentaurus Materials Workbench also checks the convergence and consistency of the calculation.

Examples and an overall view of the creation and use of defect lists can be read in Operating with defect lists.

For a detailed explanation on single defect characterization and/or convergence studies for different supercell sizes, please refer to ChargedPointDefect.

Information on already available materials and how to define the material specifications needed for different Sentaurus Material Workbench modules is available at MaterialSpecifications and Material specifications.

Specific information on how to create, characterize and perform defect calculations can be read at the following classes:

The calculations performed with the above lists can be used together with writeSentaurusParameters to produce Sentaurus Process input files. The extraction functions are:

## Multilayer Builder¶

For an overall explanation on the multilayer builder features see Notes.

The available classes are: