Metal-alumina interface: Influence of the metal electronegativity and of the substrates stoichiometry

The first stages of metal-alumina interfaces have been investigated depending on metal deposit thickness. The modified Auger parameter (alpha') variation has been analyzed for a series of metals (Pd, Cu, Ni and Cr) of decreasing electronegativity. It appears that atoms with low electronegativity (Cr) promote the formation of an oxide phase at the interface, whereas atoms with a higher electronegativity (close to oxygen (Pd)) induce an electronic transfer from the oxide substrate to the metal deposit. In the latter case, an interaction between the deposited metal atoms and the cations of the surface seems to determine the electronic transfer.