EVOLUTION OF THE ELECTRONIC AND GEOMETRIC STRUCTURES OF SIZE-SELECTED Pt AND Pd CLUSTERS DEPOSITED ON Ag(110) OBSERVED BY PHOTOEMISSION

Abstract

Mass-selected Ptn and Pdn (n=1–15) clusters, generated by ion bombardment, are deposited at room temperature in submonolayer quantities on Ag(110) single-crystal surface and characterized by electron spectroscopy (XPS, UPS). Different sites, reflected in the Pt-5d and Pd-4d binding energies, are observed as a function of the substrate temperature, indicating clearly the surface-subsurface atom exchange processes. The monodispersed clusters indicate individual discrete electronic structure features of the Pt-5d and Pd-4d emission. For the monomers virtual bound-state formation as in dilute (3%) PtAg and PdAg alloys is observed. With increasing cluster size, firstly, the increasing splitting between the bonding-like and antibonding-like d-states reflects the increase in cohesive energy due to molecular interaction, and secondly, the shift of the center of gravity of the d-emission towards the Fermi energy indicates the trend to transition-metal formation.