SEM images of macroporous silicon etched in TMAH at various times. SEM images of macroporous silicon after chemical etching in 25 wt.% TMAH for (a) 10, (b) 20, (c) 30, and (d) 40 min. The inset shows a high-magnification image of each specimen. The Au-assisted chemical etching of (111) silicon was conducted in 15 mol dm−3 HF/1 mol dm−3 H2O2 for 1 min through a photoresist honeycomb mask. (e) SEM image of Au-coated (100) silicon after metal-assisted chemical etching and subsequent chemical etching in 25 wt.% TMAH for 20 min.
Asoh et al. Nanoscale Research Letters 2012 7:406 doi:10.1186/1556-276X-7-406