Figure 5From: Fabrication of Porous Anodic Alumina with Ultrasmall Nanopores a 5 μm × 5 μm AFM images PAA fabricated in 0.3 M oxalic acid under 40 V for 10 h, b the relationship between nanoparticle size/pore diameter and anodizing potentials, 500 nm × 500 nm AFM images of PAAs re-anodized under c 20 V and d 40 V for 1 h after 20-s anodization at 5 VBack to article page