Cs adsorption on ZrC(111): Photoemission spectroscopy study

Room-temperature adsorption of Cs on ZrC(111) surface has been studied by c ore-level photoemission spectroscopy. The work function of the substrate su rface decreases monotonically with Cs adsorption and approaches the Cs meta l value without showing a clear work function minimum. Cs 4d core-level lin eshape analysis reveals that the loss peaks due to overlayer plasmon excita tion are already formed in the initial stages of adsorption. These results suggest that the adsorbed Cs atoms are in a metallic state which is brought about by the formation of Cs islands at low coverages and that adsorption proceeds via growth of these islands.