Self-organized formation of hexagonal pore structures in anodic alumina

The morphology and formation conditions of ordered hexagonal pore arrays in anodic alumina are discussed. The ordered arrangement of pores is shown to form by a self-organized process starting from randomly distributed pore positions at the surface of the alumina. The influence of the pretreatment of the aluminum substrate and the anodizing conditions on the growth kinetics and the tendency to form hexagonal pore structures were investigated. Homogeneous etching conditions are required in order to obtain regular pore arrays. This observation corresponds to the finding that hexagonal pore arrays are related to a smooth etching front and a homogeneous depth of neighboring pores.