Microporous silicon

Abstract

Virtually all porous silicon structures studied to date via electrochemical etching are mesoporous or macroporous, rather than microporous. Very high surface area (540-840 m2/g) porous silicon structures with high micropore content have now been demonstrated by wafer anodization in very concentrated hydrofluoric acid, metal-assisted stain etching, galvanic etching, and silica reduction. The smallest electrochemically generated pores to date are probably "supermicropores" lying in the range of 1-2 nm diameter since they do not exhibit molecular sieving over the 0.4-0.85 nm molecule size range. Highly microporous silicon could be advantageous for a number of specific applications such as hydrogen storage, gettering, explosives, and gas sensing, but the low chemical stability of the material could pose challenges with its industrial exploitation.