Theory of oxygen chemisorption on GaAs(110)

Using a localized-orbital representation, we have calculated the electronic structure of oxygen chemisorbed on the GaAs (110) surface in various bonding configurations. Two principal results which emerge are (i) that the effects of chemisorption on the surface species are strongly affected by allowing the surface to relax, and (ii) that molecularlike correlations persist and are important for localized nonbonding orbitals in the adsorbate. Our results provide detailed interpretations of x-ray photoemission spectroscopy, ultraviolet photoemission spectroscopy, and electron-loss spectroscopy studies of the oxidation of GaAs(110), and a comparison with all the experimental data strongly indicates that in the initial stages of oxidation ${\mathrm{O}}_2$ chemisorbs principally on the surface As, with the surface maintaining its relaxed configuration.