Examples of SEM images of a PAA film on Si. The specific PAA film on Si was fabricated by anodic oxidation of an Al film/Si in oxalic acid aqueous solution, using two-step anodization. Images (a) and (b), and the inset of (b) are top view images, while (c) depicts a cross-sectional image. The pore diameter in this sample is approximately 40 nm after pore widening for a duration of 40 min.
Gianneta et al. Nanoscale Research Letters 2013 8:71 doi:10.1186/1556-276X-8-71