1. VIRTUAL NANOLAB BY QUANTUMWISE
Presentation by:
Sheng Yu
Supervisor: Prof. Qiliang Li

2. Strain engineering monolayer MoS2 by crystal Al2O3

3. Outline
● Create Al2O3/MoS2 interface structure A. Create MoS2 monolayer B. Create Al2O3 C. Merge to Al2O3/MoS2 interface structure ● Optimization the Al2O3/MoS2 interface structure ● Simulation on the structure under La=Lb=9.5Å A. Total Energy B. Bandstructure ● Calculation of the strain strength A. Investigate Total Energy vs. La=Lb B. Find La=Lb with minimum total energy C. Calculate Strain = (La-Lao)/Lao. Lao is lattice parameter of original MoS2 monolayer

4. ● Create Al2O3/MoS2 monolayer structure
① Jobs command window ② The jobs you have already finished
③ The jobs you are going to analyze ④ Analysis window

5. ● Create Al2O3/MoS2 monolayer structure A. Create MoS2 monolayer
Drag MoS2.py into Builder
Find material resources at:

6. ● Create Al2O3/MoS2 monolayer structure A. Create MoS2 monolayer
Fit the unit cell
Drag to select right 3 atoms, Press Delete.

7. ● Create Al2O3/MoS2 monolayer structure A. Create MoS2 monolayer
Change the lattice type to hexagonal
La=Lb=3.1604Å

8. ● Create Al2O3/MoS2 monolayer structure B. Create Al2O3
Drag Al2O3.cif into Builder

9. La=Lb=4.785Å
Al2O3 has hexagonal lattice type with parameter of La=4.785Å
MoS2 also has hexagonal lattice type with parameter of Lb=3.1604Å
The lattice parameter ratio is La/Lb= 1.514
Therefore I suggest a quasi-superlattice structure with 2 unit cells of Al2O3 and 3 unit cells of MoS2.

10. ● Create Al2O3/MoS2 monolayer structure
C. Merge to Al2O3/MoS2 interface structure
Repeat unit cell of Al2O3 by 2 × 2 × 1
La=Lb=9.57Å

11. ● Create Al2O3/MoS2 monolayer structure
C. Merge to Al2O3/MoS2 interface structure
Repeat unit cell of MoS2 by 3 × 3 × 1
La=Lb=9.481Å

12. ● Create Al2O3/MoS2 monolayer structure
C. Merge to Al2O3/MoS2 interface structure
We set La=Lb=9.5Å for both Al2O3 and MoS2

13. ● Create Al2O3/MoS2 monolayer structure
C. Merge to Al2O3/MoS2 interface structure
We set La=Lb=9.5Å for both Al2O3 and MoS2

14. ● Create Al2O3/MoS2 monolayer structure
C. Merge to Al2O3/MoS2 interface structure
Merge Al2O3 and MoS2 together

15. ● Create Al2O3/MoS2 monolayer structure
C. Merge to Al2O3/MoS2 interface structure
Increase the Lc of unit cell to 35Å
Move MoS2 to make more space between MoS2/Al2O3

16. ● Create Al2O3/MoS2 monolayer structure
C. Merge to Al2O3/MoS2 interface structure
Center the atoms in the unit cell
Change the lattice type back to hexagonal

17. ● Optimization
Go to script Generator
Optimization

18. ● Optimization
Set the method to GGA
Do not constrain the unit cell

19. ● Optimization Save your program by your directory Go to Job Manager
After optimization, the separation between Al2O3 and MoS2 is 3.13Å

20. Simulation of the structure
In running the program
Drag your optimized structure to Script Generator

21. Simulation of the structure
Choose Bandstructure and Total Energy under Analysis
Set the basic parameters of Bandstrucuture

22. Simulation of the structure
Save and run

23. ● Calculate the strain strength A. Investigate Total Energy vs. La=Lb
Drag your optimized structure to Builder
Change La=Lb=9.51Å

24. ● Calculate the strain strength A. Investigate Total Energy vs. La=Lb
In the Script Generator, choose Bandstructure and Total Energy. Save and run!

25. ● Calculate the strain strength A. Investigate Total Energy vs. La=Lb
Set La=Lb=9.49Å
In the Script Generator, choose Bandstructure and Total Energy.
Save and run!

26. ● Calculate the strain strength
B. Find La=Lb with minimum total energy
C. Calculate strain induced by interface
Compare the total energy of 3 structures, we find the structure with Lc=9.50Å
has the minimum total energy.
Therefore the strain effect of Al2O3 on MoS2 monolayer is:
(Lc/3 – Lb)/Lb = 0.198%

27. Display the bandstructure of Al2O3/MoS2 system.

28. Transmission spectrum of perfect sheets of graphene and MoS2:
Opening a band gap in silicene and bilayer graphene with an electric field:
Effective mass of electrons in silicon:
Sheng Yu
Phone number:
Engineering Building 3702