X-ray photoelectron spectroscopy study of rhodium particle growth on different alumina surfaces

X-ray photoelectron spectroscopy (XPS) was used to investigate Rh particle formation on Al2O3 substrates. Rhodium was deposited in situ by electron be am evaporation on single crystalline alumina specimens which had been clean ed by heating in air. The (0001), (<1(1)over bar 02>) and (<11(2)over bar 0 >) orientations of alumina were used with no further treatment. In addition , these substrates were also Ar+-ion sputtered before deposition, to modify the surface structure. The Ph growth was monitored by means of the modifie d Auger parameter (MAP), the binding energy (BE) and the Full Width at Half Maximum (FWHM) of the Ph 3d(5/2) peak. The results for the very early stag es of growth on the six substrates exhibit differences which are also refle cted in the charge transfer between Ph and alumina, as obtained from the MA P data. Differences in the charge transfer are explained by details of the substrate nature which might differ on individual samples. (C) 1999 Elsevie r Science B.V. All rights reserved.