Morphology and thickness of ultra-thin epitaxial Al2O3 film on Cu-9%Al(111)

We investigated the surface morphology, film thickness and natures of the chemical bonds of oxide films on Cu-9%Al(l 11) single crystal using Auger electron spectroscopy (AES) and a scanning electron microscope (SEM). In the oxide film obtained by introducing 1300 L oxygen at 725degreesC, only At was oxidized and the epitaxial Al2O3 film grew on the clean Cu-9%Al(1 11) surface. The Al2O3 film surface had two morphologies that consisted of a rough surface and a flat one. The rough surface was markedly observed in the sputtered region to obtain a clean surface. The rough surface had a thickness of about 3.0-3.5 nm. On the other hand, the uniform film whose thickness was about 3.5 nm grew on the flat surface. It was considered that the surface roughness of more than 0.5 nm for the Al2O3 film was related to the roughness of the clean surface. Therefore, to grow a flat uniform film over a large area, it is essential to prepare a flat surface prior to oxidation.