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 (√3×√3)R30o surface alloy, Bi-(p×√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 (√3×√3)R30o Ag2Bi alloy and Bi(110) thin film are shifted to lower binding energy by ∼0.6 eV and ∼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 ∼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.