Size effects on the linewidths of the Auger spectra of Cu clusters

We discuss the role of the size distribution of Cu clusters deposited on graphite in determining the broadening and the shifting of the Auger L3VV Lineshapes observed when the average cluster size decreases. In our interpretation this broadening is only due to the superposition of various narrow Auger lines relative to the various cluster dimensional classes, each shifted towards lower kinetic energies because their small sizes. The Auger peak shifts are mainly due to the change in the valence band and core levels as the cluster size decreases. The model used to reproduce the Auger line broadening, following the Cini-Sawatzky approach, takes into account the broad distribution of the different diameters.