Polycrystalline and Monocrystalline Pore Arrays with Large Interpore Distance in Anodic Alumina

We have prepared hexagonally arranged pore arrays with large interpore distance ( 200 – 460 nm ) by using two kinds of techniques: a self‐organization process and a prepattern guided anodization on aluminum. The self‐organized pore arrays were produced by anodizing aluminum in an aqueous phosphoric acid solution ( H 3 PO 4 : CH 3 OH : H 2 O = 1 : 10 : 89 ) , and show a polycrystalline, i.e., poly‐domain, feature. Within each domain of several micrometers, the arrays are hexagonally arranged with an interpore distance of 460 nm , while the domains are oriented randomly in plane. A monocrystalline pore array structure with variable interpore distance was prepared based on electron‐beam lithography and a subsequent anodization in oxalic acid solution. With a well‐designed set of anodization parameters, the prepattern can act as the initiation points and guide the pore growth in the anodic film. Very high aspect ratios (∼500) can be achieved.