Structure of the Al/Al2O3 interface

The structure of the interface between aluminum and its amorphous surface oxide has been examined by high resolution electron microscopy. The interface was generated on (111) and (110) Al surfaces with oxide films grown by thermal oxidation in air or by anodization. The roughness of the interface consists of a long-range component originating in the native coarseness of the Al surface, and of a short-range component descriptive of the undulations of the interface over atomic-scale lateral distances. The short-range roughness arose from the presence of ledges on the aluminum at the interface. The ledge heights generally did not exceed two interplanar spacings.