VIRTUAL NANOLAB BY QUANTUMWISE

Presentation by:

Kwesi Eshun

Supervisor: Dr. Qiliang Li

ORDER OF PRESENTATION

1. Introduction

2. Structures

3. Models for Simulation and Analysis

4. Perspective: Si/2D Structures (MoS2 or WSe2)

5. P-N Junctions

6. Effective Mass

7. Transistors

8. Uses

9. Conclusion

INTRODUCTION

• A simulation software for nanoscience.

• An Ideal tool for teaching basic concepts of nanotechnology, solid

state physics etc.

• Used by over 150 research groups at leading universities,

government labs in a wide range of application areas.

• More than 600 scientific articles have been published using ATK

(Atomistix ToolKit).

• Has a GUI that can be used for other atomic-scale simulations as

well.

• Runs on a python scripting interface.

• Can be used to calculate and analyze the electronic properties and

structure of nanowires, semiconductors and pn junctions.

Structures

• Molecules eg. Benzene

• Crystals eg Silver(fcc), Si(fcc) etc.

• Fullerenes – carbon nanotubes

Benzene

Ag<111>

Fullerene

MODELS AND ANALYSIS FOR SIMULATION

• Version 12.8.2

New models included that are not found in older versions such

as the Tight-Binding model and Socorro model.

Models used for simulation in current version (13.8 release

candidate) include:

1. DFT-LDA,GGA,MGGA

2. SE- Extended Huckel model

3. SE- Slater Koster model

4. Classical

5. Abinit

New features introduced in the current version are phonon

calculations, Shell-wise Hubbard + U model and many more.

ANALYSIS

Types of analysis:1. Bandstructure

2. IV curve

3. Transmission Spectrum/Pathways

4. Electron Difference Density/Electrostatic Difference Potential

5. Density of States

6. Electron Density

7. Forces

8. Stress

9. Mulliken Population

How-to-Use

1. Create structure using the Builder function.

2. Define lattice parameters or modify structure to suite the simulation using the tools in the Builder

interface. Then send the final structure to the Script Generator for analysis and calculation.

3. In the Script Generator, define model to be used for simulation and and select type of analysis to run. The

Editor tool can be used to manually configure simulation settings.

4. From the Script Generator, send structure to the Job Manager then run simulation.

5. After simulation, results can be analyzed using the Analyzer tool and the 3D structure can also be viewed

with the Viewer tool.

Main VNL window

Steps

1. Builder Menu

Script Generator

2. Script Generator

Calculator to define

model for simulation

Job Manager

Results and Analyzer

PERSPECTIVE: Si/2D structures

Si: Has a band gap of 1.1eV

www.users-phys.au-dk

Silicon GaAs

Using Virtual Nanolab to compare the above results

2D Structures-MoS2

Hexagonal Structure

Nanosheet

MoS2

Nanotube

Monolayer and Double layer MoS2

with VNL

1.8eV

P-N Junctions

P doped

(p-type)

Cl- doped

(n-type)

Diode behavior

(Appl. Phys. Lett. 102, 093104 (2013); doi: 10.1063/1.4794802)

FIG. 1. Calculated current-voltage characteristics at

300K of the constructed p-n junction.

FIG. 2. The electronic structures of Cl-doped (a) and

P-doped (b) MoS2 supercell, compared with undoped

band structures (aligned with doped ones); the

wavefunctions of the lowest conduction band of Cl-doped

(c) and the highest valence band of P-doped (d) at K

point of the Brillouin zone. The arrows indicate the

position of impurity atoms.

Si (111) and Si (100)

<111>

<100>

Bandstructure simulation

of different directions of

Si can be done

Effective Mass

Fig. 1 Effective mass for

Si<111>

Fig. 2 Effective mass for

Si<100>

Si(100) FET

www.quantumwise.com

Doping&Conductance of Si FET

Transmission spectrum with 0 Volt gate

potential of p-doped Si.Conductance as function of the gate

bias

www.quantumwise.com

Uses of VNL

There is a wide range of usage for Virtual Nanolab, including:

1. Graphene

2. Nanowires

3. Magnetic Tunnel Junctions

4. Molecular Electronics

5. Three-Terminal Devices

6. Single-Electron Transistors

Conclusion

1. Most electronic properties of nanostructures can be simulated with

Virtual Nanolab.

2. Provides a vivid understanding of the band properties of semiconductors,

pn junctions.

3. An Ideal tool for teaching basic concepts of nanotechnology, solid state

and device physics.

4. Tutorials can be found on www.quantumwise.com/tutorials