First step of anodization influences the final nanopore arrangement in anodized alumina

Anodic porous alumina is a well-known template material for nanofabrication. To obtain highly ordered nanoporous array, sophisticated and expensive methods are applied. On the other hand there is two-step self organized anodization, which is much cheaper, but obtained alumina arrangement is not ideal. In our paper, influence of the first step of anodization on the final MO structure arrangement is studied in details. Anodizations were carried out in 0.3 M oxalic acid at 35 degrees C at various potentials and durations of the first step of anodization. Second step of the anodization was constant for all the experiments and was 15 mm long. Oxide layer thickness formed during the first step of the anodization was 50, 100, 150 and 200 pm and after oxide removal, remaining concaves were serving as a mask for further growth during second step of the anodization. The longer first step of anodization, the higher regularity ratio and circularity, and lower percentage of defects in the nanoporous array. Anodic porous alumina was formed at four various potentials: 30, 40, 50, 60 V. The best arrangement of nanopores was found for samples anodized at 40 V. Maximum of regularity ratio was corresponding to the minimum of defect content in the MO array. Long enough first step of two-step self-organized anodization in 03 M oxalic acid can provide high-ordered nanoporous template for fabrication of various nanomaterials with new, unique properties. (C) 2011 Elsevier BM. All rights reserved.