Nanoisland formation of small Ag n -clusters on HOPG as determined by inner-shell photoionisation spectroscopy

XPS (3d) and Auger spectra (MNN) of deposited Agn-clusters on a non-sputtered HOPG surface have been measured. Most of the XPS and Auger spectra appear very similar to the corresponding bulk spectrum, caused by a high mobility and agglomeration of the clusters on the inert carbon surface, independent of the initial cluster size. The metallic fingerprint of the cluster-agglomerated islands is sustained under UHV conditions for several days. Oxidised Ag-islands reveal a positive binding energy shift in distinct contrast to the negative XPS shift usually observed for silver oxide bulk compounds. The XPS binding energy shift has been used for estimation of the diameter of the cluster-assembled nanoislands (6–9nm) using an electrostatic model.