The effect of Rb coverage on the oxidation of [formula omitted] interfaces

Abstract

Core-level and valence-band photoemission and work-function measurements have been used to investigate the effect of Rb coverage on the oxidation of Rb InSb (111) interfaces as a function of oxygen exposure at room temperature. The results show that a rapid oxygen uptake at low oxygen exposures is basically independent of the Rb coverage. For low Rb coverages, the oxygen adsorption is mainly related to the chemisorbed atomic oxygen and/or the oxidation of Sb on the surface, which is associated with an increase in the work function. In the case of high Rb coverages, the oxidation of the Sb atoms takes place at the interface between the peroxide (Rb 2O 2) and the substrate at low oxygen exposures, causing an initial decrease in the work function. The O 2− 2 ion appears to have four features in the valence band. The O − 2 species of the superoxide (RbO 2) located in the topmost layer is stabilized only after a certain amount of O 2 has been dosed to the surface. At high oxygen exposure the intensity ratio of O − 2 to O 2− 2 increases with Rb coverage.