Bimodal spatial distribution of pores in anodically oxidized aluminum thinfilms

Though porous anodic aluminum oxide has been the subject of considerable re search since the 1950s, little attention has been devoted to the characteri zation of the self-organization of the pore structures, and fewer of these studies have focused on anodization of thin films. The degree to which thes e structures self-organize, however, could play a vital role in future appl ications of porous anodic aluminum oxide. In this study a model is develope d to describe pore ordering in thin anodized aluminum films. The model is b ased on a radial distribution function approach to describe the interpore s pacings. Idealized one-dimensional and two-dimensional (2D) radial distribu tion functions are combined by linear superposition to approximate experime ntal radial distribution functions. Using these radial distribution functio ns, an order parameter is developed and an improved definition of pore spac ing is constructed. This method confirms that the oxide initially forms wit h a highly frustrated porous structure and reorganizes toward greater 2D or der as the oxide grows into the film. (C) 2000 American institute of Physic s. [S0021-8979(00)07823-3].