Back-scattered electron SEM images of n-type SiNWs (a) before and (b) after acid treatment. The white dots (marked by white arrows) denote the metal catalyst droplets for n-type SiNW VLS growth. After acid treatment, the white dots are almost absent.
Xie et al. Nanoscale Research Letters 2012 7:621 doi:10.1186/1556-276X-7-621