Self-ordered Porous Anodic Alumina Templates by a Combinatory Anodization Technique in Oxalic and Selenic Acids

A combinatory two-step anodization technique is presented to prepare self-ordered porous anodic alumina (PAO) templates. The first and second anodization steps are performed in oxalic and selenic acid at 40 V and 45 V, respectively, giving rise to 13-nm-diameter PAOs with high ordering and porosity of 1.4%. The anodization time for the second step is also changed to investigate the effect of the oxide layer thickness on the pore ordering, using field-emission scanning electron microscopy and fast Fourier transform analyses. Increasing the anodization time from 20 min to 1 h considerably improved the ordering and hexagonal domain structures. Further increasing the anodization time up to 8 h continuously deteriorated the ordering of the PAOs, although the nanopore growth rate remained almost constant. The fabrication of small-diameter PAOs in selenic acid is discussed and related to the electric field concentration at the oxide-electrolyte interface at the bottom of pores.

Automated summary

A combinatory two-step anodization technique is proposed to prepare high-order 13-nm-diameter PAO templates, with different anodization times affecting pore ordering. Increasing the anodization time for the second step can enhance the ordering and structure of PAOs, but excessively long anodization times lead to deterioration of ordering.