Effect of TMAH concentration on the morphology of macroporous silicon. SEM images of macroporous silicon after chemical etching in 1 wt.% TMAH for (a) 10, (b) 20, and (c) 30 min. The inset shows a high-magnification image of each specimen. (d) Tilted image taken at an angle of 45° to the surface. The conditions for Au-assisted chemical etching of (111) silicon were the same as those in Figure 5.
Asoh et al. Nanoscale Research Letters 2012 7:406 doi:10.1186/1556-276X-7-406