Amorphous and crystalline oxides on aluminium

In order to study the transition from amorphous to crystalline aluminium oxides, high purity aluminium was oxidized in dried oxygen of atmospheric pressure at 673 and 913 K. The morphology of the oxide layers produced was investigated by optical microscopy methods (phase and interference contrast) and scanning and transmission electron microscopy. The crystallinity was determined using electron (micro)diffraction methods. The existence of a hitherto undescribed transition aluminium oxide was established. Interface coarsening resulting from the formation of “tops” and “depressions” or “dimples”, as consequences of vacancy creation and injection in the substrate surface layers, was quantified by Auger depth profiling. The X-ray photoelectron spectroscopy technique revealed differences in the coordination of the aluminium cation between the amorphous and crystalline oxides.