Electrochemical Formation of Porous Silicon with Medium-Sized Pores

Medium-sized pores of which diameter was over 100 nm were successfully prepared by anodization in 3 wt% HF aqueous solution containing KMnO4 and surfactant. The presence of an appropriate oxidizing agent and a surfactant was indispensable for the formation of medium-sized pores, but the concentration dependence was not significant. Similar method was applied to the p+-type silicon and led to the pore widening.