Oxidation of GaAs(110) with NO2: A molecular beam study

Abstract

We describe time-resolved modulated molecular beam measurements of the adsorption of NO2 on the GaAs(110) surface. These measurements provide a quantitative description of the gas–surface interaction; thermal NO2 has a nearly unity sticking probability, dissociating to form NO (which quickly desorbs) and a surface oxide of ∼1/3 ML saturation coverage. The NO2 dissociation probability is strongly controlled by the defect density, the oxygen coverage, and the surface temperature. We have characterized the competition between the processes leading to oxygen deposition, i.e., desorption and diffusion of NO 2 to reactive defects. The barrier energies Ediff=6±2 kcal/mol and Edes=9±2 kcal/mol provide an interesting example of the transition from defect-dominated surface chemistry, typical of low Miller index metal surfaces to defect- insensitive diffusion-limited chemistry, which we argue is generic to corrugated semiconductor surfaces.