SEM images of macroporous silicon formed by metal-assisted chemical etching. SEM images of Au-coated (111) silicon after chemical etching in 15 mol dm−3 HF/1 mol dm−3 H2O2 for 1 min using (a, b) polystyrene honeycomb mask and (c to e) photoresist honeycomb mask. The periodicity of the openings of the mask was 3 μm in both cases. (b, e) Cross-sectional images of macroporous silicon shown in (a) and (d).
Asoh et al. Nanoscale Research Letters 2012 7:406 doi:10.1186/1556-276X-7-406