3d core level shifts on Ge(001), clean and after exposure to NH3 and H2O

Abstract The 3d core level shifts were analysed on clean, NH 3 − and OH ( + H)-covered Ge(001). Even before curve fitting, the adsorbate-induced changes prove that two surface components of equal intensity exist on the clean surface, one shifted by 450 meV towards lower binding energy (BE) and one overlapping with the bulk contribution. We attribute the former to the dimer up-atoms, the latter to the down-atoms. During initial adsorption of NH 3 on the down-atoms, a component at −530 meV towards higher BE appears. The component at 450 meV is conserved, even upon completion of monolayer adsorption. OH ( + H) quenches the 450 meV component and induces one at −560 meV and one overlapping with the bulk component. We attribute them to GeOH and GeH, respectively.