Process for fabricating nanowire arrays
A process is provided for etching a silicon-containing substrate to form nanowire arrays. In this process, one deposits nanoparticles and a metal film onto the substrate in such a way that the metal is present and touches silicon where etching is desired and is blocked from touching silicon or not present elsewhere. One submerges the metallized substrate into an etchant aqueous solution comprising HF and an oxidizing agent. In this way arrays of nanowires with controlled diameter and length are produced.
1. A process for etching a substrate comprising polycrystalline silicon to form structures, comprising the steps of: (a) depositing metal on top of the substrate, and (b) contacting the metallized substrate with an etchant aqueous solution comprising about 2 to about 49 weight percent HF and an oxidizing agent, wherein the process results in nanowire arrays in which the average diameter of the nanowires is less than about 125 nm.
2. A process as described in claim 1 , wherein the oxidizing agent is oxygen gas bubbled through the etchant aqueous solution.
3. A process as described in claim 1 , wherein the metal deposited in step (a) is silver.
4. A process as described in claim 3 , wherein the silver is deposited by sputtering.
5. A process as described in claim 3 , wherein the silver is deposited as a continuous film.
6. A process as described in claim 1 , further comprising depositing nanoparticles of one of silicon dioxide and iron oxide on the top of the substrate prior to depositing the metal on the top of the substrate.
7. A process as described in claim 1 , further comprising depositing polystyrene nanoparticles of on the top of the substrate prior to depositing the metal on the top of the substrate.
8. A process as described in claim 1 , wherein the oxidizing agent is hydrogen peroxide.
9. A process as described in claim 1 , wherein the process results in an array of nanowires oriented substantially vertically relative to the top of the substrate.
10. A process as described in claim 1 , wherein the process results in an array of tapered nanowires having a greater diameter proximate the substrate and a lesser diameter proximate tips of the nanowires.
11. A process as described in claim 1 , further comprising forming a nanowire array produced by the process into a lithium ion battery anode.
12. A process as described in claim 1 , wherein the process results in nanowire arrays in which the average diameter of the nanowires is less than about 100 nm.