Regularity of nanopores in anodic alumina formed on orientated aluminium single-crystals

On aluminium single crystals with (1 1 1), (1 1 0) and (1 0 0) orientation, nanoporous alumina layers were formed in a two-step anodization process within sulphuric acid. The pore ordering within the hexagonal arrangement of the nanopores was documented by scanning electron microscopy (SEM), described on the basis of defect thermology and analyzed quantitatively by image evaluation. The best ordering was obtained in nanoporous alumina on (1 0 0) aluminium. We supposed that this is caused by the interface energy term within the driving force for the formation of the nanoporous alumina, since – in contrast to (1 1 1) and (1 1 0) aluminium as substrate – in the case of (1 0 0) aluminium the interface energy is minimised in the waved interface between aluminium and hexagonally arranged nanoporous alumina.

► Anodic alumina was formed on (1 1 1), (1 1 0) and (1 0 0) aluminium single crystals.
► The pore ordering of the nanopores was described on the basis of defect thermology and analyzed quantitatively by image evaluation.
► The best ordering was obtained in nanoporous alumina on (1 0 0) aluminium.
► We supposed that the minimisation of the interface energy is the reason for this.