AL INTERMEDIATE OXIDATION-STATES OBSERVED BY CORE-LEVEL PHOTOEMISSIONSPECTROSCOPY

Aluminum oxidation states in stoichiometric or substoichiometric confi guration are studied by core level photoemission spectroscopy on diffe rent substrates (SiO2, graphite). They are compared with recent result s reported for the interface Si-Al-n+O. Three Al oxidation states have been identified and their space distribution (binding energy, intensi ty, 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-- interm ediate oxidation state is shown to be confined at the interface; on th e contrary, the Al1+-O oxidation state and the stoichiometric oxide (a lumina) are present beyond the interface region. From the attenuation of the substrate core level peak, the deposition morphology and the at tenuation length of the photoelectrons have been deduced. (C) 1995 Ame rican Institute of Physics.