Figure 2From: Template-free fabrication of silicon micropillar/nanowire composite structure by one-step etchingCross-sectional SEM images. Silicon samples are etched in the solution containing 4.6 M HF, 0.02 M AgNO3, and 0.05 M KMnO4 for different reaction times. (a) 15 min; (b) 45 min; (c) 90 min.Back to article page