The evolution of the electronic structure at the Bi/Ag(111) interface studied using photoemission spectroscopy

The growth of Bi on Ag(111) induces different surface structures, including. (root 3 x root 3)R30 degrees surface alloy, Bi-(p x root 3) overlayer and Bi(110) thin film, as a function of increasing Bi coverage. Here we report the study of electronic states of these structures using core level and valence band photoemission spectroscopy at room temperature. The sp-derived Shockley surface state on Ag(111) is rapidly quenched upon deposition of Bi, due to the strong variation of the in-plane surface potential in the Ag2Bi surface alloy. The Bi 4f core levels of the. (root 3 x root 3)R30 degrees Ag2Bi alloy and Bi(110) thin film are shifted to lower binding energy by similar to 0.6 eV and similar to 0.3 eV compared with the Bi bulk value, respectively. Mechanisms inducing the core level shifts are discussed as due to a complex superposition of several factors. As Bi coverage increases and a Bi(110) overlayer forms on Ag(111), a new state is observed at similar to 0.9 ML arising from electronic states localized at the Ag-Bi interface. Finally the change of work function as a function of coverage is discussed on the basis of a charge transfer model.