Adatom and rest-atom contributions in Ge(111)<i>c</i>(2×8) and Ge(111)-Sn(7×7) core-level spectra

Abstract

We have identified the adatom contribution in the Ge 3d core-level spectra from the clean Ge(111)c(2\ifmmode\times\else\texttimes\fi{}8) surface, shifted 0.17 eV to higher binding energy compared to the bulk. This adatom component vanishes in the Ge(111)-Sn(7\ifmmode\times\else\texttimes\fi{}7) surface core-level spectra where Sn occupies the adatom site. Moreover we report the observation of an earlier proposed difference between the rest atoms in the c(2\ifmmode\times\else\texttimes\fi{}8) structure, and also a shift to lower binding energy for the rest atoms in both structures studied.