Al Intermediate Oxidation-States Observed by Core-Level Photoemission Spectroscopy

Aluminum oxidation states in stoichiometric or substoichiometric configuration are studied by core level photoemission spectroscopy on different substrates (SiO2, graphite). They are compared with recent results reported for the interface Si-Al-n+O. Three Al oxidation states have been identified and their space distribution (binding energy, intensity, and width) is determined in the region from the interface with the substrate up to the surface of a thick overlayer. The Al-2+O-- intermediate oxidation state is shown to be confined at the interface; on the contrary, the Al1+-O oxidation state and the stoichiometric oxide (alumina) are present beyond the interface region. From the attenuation of the substrate core level peak, the deposition morphology and the attenuation length of the photoelectrons have been deduced. (C) 1995 American Institute of Physics.