Porous Anodic Alumina Films Grown on Al(111) Single Crystals

The microstructure and crystallographic orientation of aluminum have a significant effect on the morphology of porous alumina films grown on the surface of Al by anodizing. Most existing works regarding the regularities of aluminum anodizing consider metal foils as isotropic media. The novelty of this study lies in the characterization of porous alumina coatings formed on aluminum single crystals with the same orientation, Al(111). Experiments are carried out in 0.3 M oxalic acid in a wide range of anodizing voltages of 20–140 V. Using scanning electron and atomic force microscopy, the dependence on the anodizing voltage of the degree of porous ordering with the formation of a hexagonal array, as well as height-profile parameters of the metal–oxide interface, are shown. The thickness-to-charge ratio for the used anodizing conditions is determined.