Method for synthesis of two-dimensional dichalcogenide semiconductors

1. A method of making a transition metal dichalcogenide, comprising:

depositing a transition metal onto a substrate to form an epitaxial transition metal layer;

depositing a chalcogen onto the epitaxial transition metal layer by chemical vapor deposition; and

reacting the chalcogen with the epitaxial transition metal layer to form a transition metal dichalcogenide;

wherein the step of reacting the chalcogen with the epitaxial transition metal layer is performed at a temperature of between about 300° C. and 550° C.

2. The method of claim 1 , wherein the step of depositing a transition metal onto a substrate comprises vapor phase deposition.

3. The method of claim 1 , wherein the substrate comprises at least one of aluminum oxide (Al 2 O 3 ), aluminum nitride (AIN), gallium nitride (GaN), gallium arsenide (GaAs), or titanium dioxide (TiO 2 ).

4. The method of claim 1 , wherein the substrate comprises a crystalline layer.

5. The method of claim 4 , wherein the crystalline layer comprises a material having a Miller index of (100) or (110).

6. The method of claim 4 , wherein the crystalline substrate comprises at least one of AIN(100), GaN(100), GaAs(100), or TiO 2 (110).

7. The method of claim 4 , wherein the substrate further comprises a base layer, wherein the crystalline layer is disposed on the base layer.

8. The method of claim 7 , wherein the base layer comprises at least one of silicon or aluminum oxide (Al 2 O 3 ).

9. The method of claim 8 , wherein the silicon has a Miller index of (111).

10. The method of claim 1 , wherein the transition metal comprises at least one of molybdenum, tungsten, or tantalum.

11. The method of claim 1 , wherein the chalcogen comprises at least one of sulfur or selenium.

12. The method of claim 1 , wherein the transition metal dichalcogenide comprises molybdenum disulfide or tungsten diselenide.

13. The method of claim 1 , wherein the epitaxial transition metal layer comprises a monolayer.

14. The method of claim 1 , wherein the epitaxial transition metal layer comprises between 1 and 5 monolayers.

15. The method of claim 1 , wherein the transition metal dichalcogenide comprises between 1 and 5 monolayers.

16. The method of claim 1 , further comprising:

heating the chalcogen, wherein the step of heating the chalcogen is performed before the step of depositing the chalcogen onto the epitaxial transition metal layer.

17. The method of claim 16 , wherein the chalcogen is heated to a temperature of at least about 200° C. to produce a vapor for reacting with the epitaxial transition metal layer.

18. The method of claim 1 , wherein a carrier gas is used to deliver the chalcogen to the epitaxial transition metal layer.

19. The method of claim 18 , wherein the carrier gas comprises an inert gas.

20. The method of claim 18 , wherein the carrier gas comprises argon.

21. The method of claim 1 , further comprising:

monitoring growth of the epitaxial transition metal layer.

22. The method of claim 21 , wherein the step of monitoring growth of the epitaxial transition metal layer comprises measuring the thickness of the epitaxial transition metal layer with an oscillator.

23. A method of making a transition metal dichalcogenide, comprising:

depositing a transition metal onto a substrate to form an epitaxial transition metal layer;

delivering a chalcogen into a reaction chamber containing the epitaxial transition metal layer;

depositing the chalcogen onto the epitaxial transition metal layer by chemical vapor deposition; and

reacting the chalcogen with the epitaxial transition metal layer, wherein the chalcogen is reacted with the epitaxial transition metal layer at a temperature sufficient to cause the formation of a transition metal dichalcogenide, wherein the temperature is less than about 600° C.

24. The method of claim 23 , wherein the substrate comprises a crystalline layer.

25. The method of claim 24 , wherein the crystalline layer comprises a material having a Miller index of (100) or (110).

26. The method of claim 24 , wherein the crystalline substrate comprises at least one of AIN(100), GaN(100), GaAs(100), or TiO 2 (110).

27. The method of claim 23 , wherein the step of reacting the chalcogen with the epitaxial transition metal layer is performed at a temperature of between about 300° C. and 550° C.

28. The method of claim 23 , further comprising:

heating the chalcogen, where the step of heating the chalcogen is performed before the step of delivering the chalcogen into the reaction chamber.

29. The method of claim 28 , wherein the chalcogen is heated to a temperature of at least about 200° C. to produce a vapor for reacting with the epitaxial transition metal layer.

30. A method of making a transition metal dichalcogenide, comprising:

depositing at least one of molybdenum, tungsten, or tantalum onto a substrate to form an epitaxial transition metal layer, wherein the substrate comprises a crystalline layer;

heating a chalcogen, wherein the chalcogen comprises at least one of sulfur or selenium;

depositing the chalcogen onto the epitaxial transition metal layer by chemical vapor deposition; and

reacting the chalcogen with the epitaxial transition metal layer at a temperature of between about 300° C. and 600° C. to form a transition metal dichalcogenide.

31. The method of claim 30 , wherein the crystalline layer comprises a material having a Miller index of (100) or (110).

32. The method of claim 30 , wherein the crystalline substrate comprises at least one of AIN(100), GaN(100), GaAs(100), or TiO 2 (110).

33. The method of claim 30 , wherein the step of reacting the chalcogen with the epitaxial transition metal layer is performed at a temperature of between about 300° C. and 500° C.

34. The method of claim 30 , wherein the chalcogen is heated to a temperature of at least about 200° C. to produce a vapor for reacting with the epitaxial transition metal layer.