The optical and the electronic response of the Ge(111)-c(2 × 8) surface to O2 exposure

This Communication describes a study concerning the interaction of molecular oxygen with a clean Ge(111)-c(2 × 8) surface. This reaction has been studied by in situ monitoring the ellipsometric reflection and the surface conductance. In order to explain the experimental results a model is proposed assuming a gradual disappearance of donor and acceptor surface states. The final stage in the adsorption process is characterized by the saturation of an acceptor surface state related to an optical transition at hv = 1.9 eV