The formation mechanisms of porous silicon prepared from dense silicon monoxide

Porous silicon (PSi) has been widely investigated for use in many applications. PSi is usually prepared through the selective etching of silicon. Recently, PSi has been prepared by reducing dense silicon monoxide (SiO) with magnesium. Although the porosity has been confirmed to be a result of the selective acid dissolution of MgO, the formation mechanisms of the composite of MgO and PSi are not very clear. To better understand the formation mechanisms, we synthesized two types of PSi by reducing compact SiO and disproportionate SiO (d-SiO) with different magnesium content. The BET surface area and pore volume of these PSi samples first increased and then decreased. The highest BET surface area was 304 and 328 m(2) g(-1) for PSi prepared from SiO and d-SiO, respectively. These BET surface areas are among the highest for PSi prepared from dense SiO or silica. An inductive effect of the preformed silicon network in d-SiO was found by contrasting the pore characteristics of the two types of PSi derived from SiO and d-SiO. Accordingly, we suggested two models for the formation mechanisms of PSi from SiO and d-SiO.