Figure 6.

Pore diameter as a function of etching time of a barrier layer for PAA formed using the three synthesis condition schemes: Type I – in 0.3 M oxalic acid at a constant voltage of 50 V; type II – in 0.3 M oxalic acid at a constant voltage of 40 V; type III – in 1.5 M sulfuric acid at a constant voltage of 20 V. The temperature was held at 15 °C in all cases. The inset is a schematic describing the reaction occurring and correlating this to the three distinct trend regions (regions 1–3) for type I.