Metal-oxide interaction for metal clusters on a metal-supported thin alumina film

The interaction between deposited metal clusters and a thin model alumina f ilm grown on NiAl(110) have been studied using X-ray absorption spectroscop y (XAS) and core and valence photoelectron spectroscopy. A lower limit for the fundamental gap of the supported alumina film is determined, and found to be slightly lower than that of alumina surfaces. O 1s XAS shows that new states appear in the fundamental gap upon metal deposition. Al 2p X-ray ph otoelectron spectra from the alumina film are also sensitive to metal depos ition, whereas spectra from Al atoms at the substrate-oxide interface appea r unaffected. The present data demonstrate the existence of gap states in t he pristine film, and we discuss the effects of these states for the proper ties of this film as a model oxide substrate. (C) 1999 Elsevier Science B.V . All rights reserved.