AFM topography maps of S1 (a to c) and S2 (d to f) samples. Insets (a,d) illustrate FFT of corresponding AFM maps. Surface height profiles along dashed lines are shown on (c,f). Maps (a,d) have enhanced, contrasted for convenience.
Kladko et al. Nanoscale Research Letters 2012 7:289 doi:10.1186/1556-276X-7-289