RbF/Ge(111) interface formation studied by LEED, XPS and UPS

The interface formation between rubidium fluoride (RbF) and the Ge(111)c(2×8) surface has been studied by low-energy electron diffraction, x-ray photoelectron spectroscopy, and ultraviolet photoelectron spectroscopy as a function of growth temperature. Three interface types have been identified. Sublimation of RbF at 750 K leads to a (3×1) symmetry with three domains induced by a chemisorbed submonolayer of Rb. An epitaxial RbF overlayer is observed at 500 K with rubidium bound to the substrate (F-Rb-Ge). Island growth mode is observed at room temperature. A disordered layer of RbF is then formed, with two types of interfacial bonding: Rb-F-Ge and F-Rb-Ge. The stability of the RbF film under the irradiation of various beams is also discussed.