Formation of Nanoporous Tin Oxide Layers on Different Substrates during Anodic Oxidation in Oxalic Acid Electrolyte

Figure 7

FE-SEM images of nanoporous tin oxides formed during 1800 s anodization of the high-purity (a–c, f–h) and low-purity (d-e, i-j) Sn foils in a 0.3 M oxalic acid electrolyte at the potential of 6 V (a–e) and 7 V (f–j). Scale bars in inset images indicate 500 nm (b, d, g, and i) and 100 μm (c, e, h, and j).