Optimization of Initiation Sites of Tunnel Pits on Aluminum Foil Using Self-Ordered Concave Structures

The self-ordered concave structures fabricated on aluminum surface by aluminum anodic oxidation and oxide removal procedures were applied to control the pit initiation sites for tunnel etching of aluminum foil, where the tunnel pits would be correspondingly generated under the sites of self-ordered concave structures. The obtained sizes of the tunnel pits were 100–600 nm in width and 1.6 μm in length, which were mainly determined by the interpore distances of the concave structures and the tunnel etching conditions. Based on this process, the distribution of the tunnel pits on aluminum surface was improved observably, so that a high aspect ratio was successfully achieved.