SEM images of a porous silicon specimen. ( a) Top-view micrograph showing pores with an average diameter of 60 nm and a mean distance between the pores of 50 nm. ( b) The cross-sectional image demonstrates that the effective mean pore distance is less than 50 nm due to the occurring side branches.
Granitzer et al. Nanoscale Research Letters 2012 7:384 doi:10.1186/1556-276X-7-384