Process for fabricating silicon nanostructures

1. A process for etching a substrate comprising polycrystalline silicon to form polycrystalline silicon nanostructures, the process comprising:

depositing metal on top of the substrate; and

contacting the metallized substrate with an etchant aqueous solution comprising about 2 to about 49 weight percent HF and an oxidizing agent; and

forming a p-n junction within the substrate.

2. The process of claim 1 , further comprising selecting a method of metal deposition and selecting the oxidizing agent such that the process results in formation of an array of nanostructures oriented substantially vertically relative to the top of the substrate.

3. The process of claim 2 , further comprising selecting the method of metal deposition and selecting the oxidizing agent such that the process results in formation of nanostructured arrays in which an average diameter of the nanostructures is less than about 125 nm.

4. The process of claim 1 , further comprising selecting a method of metal deposition and selecting the oxidizing agent such that the process results in formation of nanostructures oriented substantially and approximately perpendicular to the top of the substrate.

5. The process of claim 1 , wherein depositing the metal comprises depositing the metal as a continuous film.

6. The process of claim 1 , wherein the oxidizing agent is oxygen gas and the process further comprises bubbling the oxygen gas through the etchant aqueous solution.

7. The process of claim 1 , wherein the metal deposited on top of the substrate is silver.

8. The process of claim 7 , wherein the silver is deposited by a solution made up of a metal salt.

9. The process of claim 7 , wherein the silver is deposited as a continuous film.

10. The process of claim 1 , wherein the oxidizing agent is hydrogen peroxide.

11. The process of claim 1 , wherein the oxidizing agent is one or more of oxygen, ozone, chlorine, iodine, ammonium perchlorate, ammonium permanganate, barium peroxide, bromine, calcium chlorate, calcium hypochlorite, chlorine trifluoride, chromic acid, chromium trioxide (chromic anhydride), magnesium peroxide, dibenzoyl peroxide, sodium peroxide, dinitrogen trioxide, fluorine, perchloric acid, potassium bromate, potassium chlorate, potassium peroxide, propyl nitrate, sodium chlorate, sodium chlorite, and sodium perchlorate.

12. The process of claim 1 , further comprising removing the metal from the top of the substrate after etching the substrate.

13. The process of claim 1 , further comprising forming a polycrystalline silicon nanostructure produced by the process into a lithium ion battery anode.

14. The process of claim 1 , further comprising forming an optoelectronic device including a polycrystalline silicon nanostructure produced by the process.

15. The process of claim 1 , further comprising forming a photovoltaic cell including a polycrystalline silicon nanostructure produced by the process.