In situ generation of gaseous precursors for chemical vapor deposition of a chalcogenide

1. A method for forming a chalcogenide film on a substrate comprising:

disposing an ammonium halide solid and an elemental solid together in a heated reaction environment at a common temperature;

forming hydrogen halide gas in the heated reaction environment by heating the ammonium halide solid at the common temperature, said common temperature causing ammonium halide solid to decompose into the hydrogen halide gas;

exposing the an elemental solid to the a hydrogen halide gas in the a heated reaction environment at about ambient pressure and at the a temperature at which the hydrogen halide gas is formed, to promote the elemental solid to evolve into an elemental halide-based gas;

exposing the elemental halide-based gas to a chalcogen gas provided in the heated reaction environment, at a temperature at which the elemental halide-based gas is reactive with the chalcogen gas to produce a solid chalcogenide reaction product; and

providing a substrate in the heated reaction environment for deposition thereon of a solid film of the solid chalcogenide reaction product that results from exposure of the elemental halide-based gas to the chalcogen gas in the heated reaction environment.

2. The method of claim 1 further comprising forming the chalcogen gas by heating a chalcogen solid in the heated reaction environment at a temperature that causes the chalcogen solid to evaporate into the chalcogen gas.

3. The method of claim 1 wherein the elemental solid exposure to a hydrogen halide gas while heating the elemental solid in a heated reaction environment is conducted at a temperature at which the hydrogen halide gas promotes the elemental solid to evolve into an elemental halide-based gas by the chemical reaction:

M(s)+ n HX(g)→MX n (g)+ n/ 2H 2 (g),

where M(s) is the elemental solid, X is a halogen, HX(g) is a hydrogen halide gas selected from HF, HCl, HBr, and HI, MX(g) is the elemental halide-based gas, and H 2 (g) is the hydrogen gas.

4. The method of claim 3 wherein the elemental halide-based gas exposure to a chalcogen gas provided in the heated reaction environment is conducted at a temperature at which the elemental halide-based gas is reactive with the chalcogen gas to produce a solid chalcogenide reaction product by the chemical reaction:

MX n (g)+ n/ 2Y(g)+ n/ 2H 2 (g)→MY n/2 (s)+ n HX(g),

where M is an element, X is a halogen selected from fluorine, chlorine, bromine, and iodine, MX n (g) is the elemental halide-based gas, Y is a chalcogen, Y(g) is the chalcogen gas, H 2 (g) is hydrogen gas, MY n/2 (S) is the chalcogenide reaction product, and HX(g) is a hydrogen halide gas.

5. The method of claim 3 wherein the elemental solid, M(s), comprises an elemental solid selected from Si, Ge, Sn, Pb, As, Sb, Bi, Ti, Zr, Hf, V, Nb, Ta, Mn, Re, Fe, Co, and Ni.

6. The method of claim 3 wherein the elemental solid, M(s), comprises a metal.

7. The method of claim 1 wherein the hydrogen halide gas formation by heating an ammonium halide solid in the heated reaction environment is conducted at a temperature that causes the ammonium halide solid to decompose into the hydrogen halide gas by the chemical reaction:

NH 4 X(s)→NH 3 (g)+HX(g),

where X is a halogen, NH 4 X(s) is an ammonium halide solid selected from NH 4 Cl, NH 4 F, NH 4 Br, and NH 4 I, NH 3 (g) is gaseous ammonia, and HX(g) is the hydrogen halide gas.

8. The method of claim 4 wherein the chalcogen gas, Y(g), comprises a chalcogen selected from S, Se, and Te.

9. The method of claim 1 wherein the elemental solid comprises Ti(s), the hydrogen halide gas comprises HCl(g), the elemental halide-based gas comprises TiCl x (g), the chalcogen gas comprises S(g), and the solid chalcogenide reaction product comprises TiS 2 (s).

10. The method of claim 1 wherein the elemental solid comprises a transition metal and wherein the solid chalcogenide reaction product comprises a transition metal dichalcogenide.

11. The method of claim 10 wherein the substrate comprises a substrate material selected from silicon and mica.

12. The method of claim 1 wherein the exposure of the elemental halide-based gas to a chalcogen gas in the heated reaction environment is conducted for a duration that produces on the substrate a solid chalcogenide reaction product film having a thickness of about one chalcogenide molecular layer.

13. The method of claim 1 further comprising a first step of flowing a gas through the heated reaction environment to purge oxygen from the heated reaction environment.

14. A method for forming a chalcogenide film on a substrate comprising: disposing an elemental solid powder and an ammonium halide solid powder in a heated reaction environment in a powder mixture of the elemental solid powder and the ammonium halide solid powder;

heating the powder mixture of the elemental solid powder and the ammonium halide solid powder in the heated reaction environment at a temperature that causes the ammonium halide solid to decompose into the hydrogen halide gas and promotes the elemental solid to evolve into an elemental halide-based gas;

exposing the elemental halide-based gas to a chalcogen gas provided in the heated reaction environment, at a temperature at which the elemental halide-based gas is reactive with the chalcogen gas to produce a solid chalcogenide reaction product; and

providing a substrate in the heated reaction environment for deposition thereon of a solid film of the solid chalcogenide reaction product that results from exposure of the elemental halide-based gas to the chalcogen gas in the heated reaction environment.

15. The method of claim 14 further comprising dehydrating the powder mixture of the elemental solid powder and the ammonium halide solid powder before disposing the powder mixture of the elemental solid powder and the ammonium halide solid powder in the heated reaction environment.

16. A method for forming a chalcogenide film on a substrate comprising:

disposing in a heated reaction environment an ammonium halide solid, a chalcogen solid, an elemental solid, and a substrate, the ammonium halide solid and elemental solid at a common temperature;

forming hydrogen halide gas in the heated reaction environment by heating the ammonium halide solid in the heated reaction environment at the common temperature, said common temperature causing ammonium halide solid to decompose into the hydrogen halide gas;

exposing the elemental solid to the hydrogen halide gas in the heated reaction environment at about ambient pressure and at the a temperature at which the hydrogen halide gas is formed, to promote the elemental solid to evolve into an elemental halide-based gas;

forming a chalcogen gas in the heated reaction environment by heating the chalcogen solid in the heated reaction environment at a temperature that causes the chalcogen solid to evaporate into the chalcogen gas; and

exposing the elemental halide-based gas to the chalcogen gas in the heated reaction environment at a temperature at which the elemental halide-based gas is reactive with the chalcogen gas to produce a solid chalcogenide reaction product that can deposit on the substrate in the heated reaction environment.

17. The method of claim 16 wherein the hydrogen halide gas comprises a hydrogen halide gas selected from HF, HCl, HBr, and HI.

18. The method of claim 16 wherein the elemental solid comprises an elemental solid selected from Si, Ge, Sn, Pb, As, Sb, Bi, Ti, Zr, Hf, V, Nb, Ta, Mn, Re, Fe, Co, and Ni.

19. The method of claim 16 wherein the chalcogen gas comprises a chalcogen gas selected from S, Se, and Te.