SURFACE STUDIES OF (0001) AL2O3 AND THE GROWTH OF THIN-FILMS OF CU ON AL2O3

Angle resolved x-ray photoemission spectroscopy has been employed to examine the (1 X 1) unreconstructed and the (square-root 31 X square-root 31) R +/- 9-degrees reconstructed surfaces of (0001) Al2O3 and the bonding of copper to this substrate. Clean (0001) Al2O3 is found to contain at least two chemically distinct species of oxygen, with very subtle differences between the (1 X 1) and the reconstructed faces. Copper initially grows as uniform layers on (1 X 1) Al2O3 but forms clusters after 2-3 atomic layers of metal are deposited at room temperature. The data indicate that copper is donating charge to surface oxygen with Cu-O bonds forming at the interface. However, the thickness of the reaction layer is limited to one atomic layer.