Fabrication of nanoporous alumina by two-step anodization and studyof their structural properties

Anodic nanoporous alumina (NPA) is known to be a low cost material suitable for fabrication of templates for the growth of a variety of nanostructured materials, membranes and sensors. In this work, nanoporous alumina was prepared in 0.4 M oxalic acid by a two-step anodization process. The properties of nanoporous alumina film grown on aluminum foil were studied by atomic force microscopy (AFM), scanning electron microscopy (SEM) and optical microscopy. The microscopy investigations confirm the pore formation in the produced layers and the process of anodization allows consistent fabrication of nanoporous alumina. The effect of anodization process parameters on the size of the nanopores and the distance between them were studied and good agreement with published data was found. Hence a desired diameter of the pores and the distance between of it can be obtained by adjusting the electrolyte and oxidation voltage.