Polycrystalline nanopore arrays with hexagonal ordering on aluminum

Nanopore arrays with 6 X 10(8)-5 X 10(10) cm(-2) pore densities were fabric ated by self-organized anodization on aluminum. A two-step anodization proc ess was used to oxidize aluminum in oxalic, sulfuric, and phosphoric acid s olutions. Hexagonally ordered pore arrays were obtained within domains of a few micrometers, which are separated from neighboring domains with differe nt orientation of the pore lattice by domain boundaries, i.e., the nanopore arrays show characteristics analogous to two-dimensional polycrystalline s tructure. The interpore distance can be controlled by changing the electrol yte and/or the applied voltage. (C) 1999 American Vacuum Society. [S0734-21 01(99)20304-1].