Method to produce pyrite
A method for preparing a device having a film on a substrate is disclosed. In the method, a film is deposited on a substrate. The film includes a single-crystalline or poly-crystalline semiconducting thin film. The single-crystalline or poly-crystalline semiconducting thin film is formed by sequential evaporation of a first and a second element. One example device prepared by the method includes a silicon substrate and a film on the substrate, wherein the film includes semiconducting and single- or poly-crystalline pyrite as the compound.
1. A method for preparing a device having a film on a substrate, the method comprising:
(a) providing a substrate;
(b) maintaining a first pressure in a first chamber;
(c) depositing a first element to form a thin film on the substrate in the first chamber;
(d) maintaining a second pressure between 1 mTorr and 1 Torr in the second chamber;
(e) depositing a second element over the film of the first element on the substrate in the second chamber, wherein the second element is a non-metal element and reacts with the first element in the film to form a thin film of a single phase pyrite semiconducting compound;
(f) repeating steps (b) through (e) at least until the thin film of the semiconducting compound is formed on the substrate;
wherein the second pressure is at least one order of magnitude greater than the first pressure; and
wherein the deposition of the second element is conducted between 250° C. and 450° C.
2. The method of claim 1 , wherein the substrate in step (a) is a silicon wafer.
3. The method of claim 1 , wherein the first element is deposited by a method of molecular beam epitaxy.
4. The method of claim 1 , wherein the second element is deposited by a method of molecular beam epitaxy.
5. The method of claim 1 , wherein the second element is sulfur.
6. The method of claim 1 , wherein pyrite is either single-crystalline or polycrystalline.
7. The method of claim 1 , wherein the first and the second elements are deposited under an air-tight condition.
8. The method of claim 1 , wherein the first pressure is less than 1.5×10 −5 Torr in step.
9. The method of claim 1 , wherein the second pressure is greater than three orders of magnitude relative to the first pressure.
10. The method of claim 1 , wherein the deposition of the first element is conducted between 250° C. and 450° C.
11. The method of claim 1 , wherein the thin film of the semiconducting compound has a thickness larger than 25 nanometers.
12. The method of claim 1 , wherein the thin film of the semiconducting compound epitaxially grows on the substrate.