APPLICATION OF THE AUGER PARAMETER IN THE CHARACTERIZATION OF SMALL COPPER PARTICLES SUPPORTED ON INSULATORS

A simple electrostatic model permits the estimation of Auger parameter shifts of core-ionized atoms in compounds with respect to the free atom in the gas phase. It is shown that the Auger parameter shift is a function of the number, distance, electronic polarizability and local geometry of the nearest-neighbour ligands around the core-ionized atom. We have investigated the relationship between the Cu Auger parameter shifts and the nuclearity of Cu clusters entrapped in A zeolites. It is shown that our model is useful to estimate this dependence. The model has also been applied with success to rationalize Auger parameter data on small copper clusters supported on alpha-Al2O3 (0001) surfaces and polycrystalline ZnO and graphite. We demonstrate that the screening properties of metal bulk and clusters of very low nuclearity are very similar.