The effects of ordering on the morphology of two-layer alumite—Forming a patterned interface

Two-layer alumite has been synthesized by three-step anodizing such that the 1st layer was formed by commonly known two-step anodizing at a prescribed voltage and the 2nd layer was formed at two-times higher anodizing voltage, in suitable electrolytes. When the 2nd layer is formed at an ordering voltage, alternate pores of the 1st layer continue growing through the 2nd layer, in a regular pattern. The neighboring pores cease their growth, possibly due to upward flow and thickening of barrier oxide at the new cell boundaries. The growing pores in the 2nd layer are equi-distant provided that the 1st layer is also formed under ordering conditions. If the 2nd layer is formed under non-ordering conditions the regular pattern at the interface is completely lost. Employing the two-layer alumite, nanowires by the 1st layer can be grown such that alternate pores remain empty, providing a new superlattice.