Adsorption Properties of Xe on Ag/Cu(111) System: Real-Time Photoemission Investigation

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We discuss here the adsorption process of rare gas atoms on a heterogeneous surface, Xe on Ag submonolayer partially covering Cu(111) surface. As a function of the Xe dosing, we have monitored in real-time the evolution of the Xe 4d core levels and of the LEED patterns, as well as the modification of the Shockley state band. We confirmed that the reduction in the density of states near the Fermi level strongly promotes the adsorption of Xe atoms on the surface. More interesting, it seems that the Xe overlayer on the Ag monolayer exhibits a disordered structure, which differs substantially from those observed for Xe on most of the single-crystal metal surfaces, where the Xe atoms form generally an epitaxial layer with hexagonally close-packed structure. Additionally, the commensurate (9 × 9) reconstruction characterizing the 1 ML Ag/Cu(111) is preserved after adsorption of Xe, and consequently leads to a band back-folding of shifted interface state on the 1 ML Ag islands covered by Xe. This finding is essential to understanding the effect of the surface characteristics on the adsorption properties of rare gases on metal systems.