High-resolution photoemission onAg∕Au(111): Spin-orbit splitting and electronic localization of the surface state

We present a detailed photoemission study of the surface state dispersion in 0–10 ML thin Ag films on Au(111). The dispersion of the $L$-gap Shockley-type surface state changes monotonically from the one of Au towards the one of Ag with increasing layer thickness indicating an extension of the wave function into the solid. High resolution photoemission (PES) enables an insight into decreasing spin-orbit splitting of the surface state in Ag-covered-Au(111). The photoemission data have been well reproduced by ab initio band structure calculations using the WIEN2K code. The dependence of the binding energy on the increasing silver film thickness is indicative of the localization of the surface state at the surface by comparing it with the calculated electron density of the surface state. Measurements on 10 ML $\mathrm{Ag}∕\mathrm{Au}\left(111\right)$ reveal the $d$-band states of Ag, but one still observes $sp$-related quantum well states of silver within the projected $sp$-band gap of gold.