Oxidation of GaAs(100) and GaAs(311) surfaces

Abstract

The interaction of unexcited, molecular oxygen with Ga(100)-(4 × 1) and GaAs(311)-(1 × 1) surfaces, which were prepared in situ by simultaneous ion bombardment and annealing at approximately 560° C, was studied by using Auger electron spectroscopy and by following the intensity decrease of elastically backscattered electrons of 2 keV. The uptake versus exposure curves measured with (100)-(4 × 1) and with cleaved (110) surfaces, which were recorded for comparison, were found to be identical. Since the initial oxidation stages are known to depend on the surface composition GaAs(100)-(4 × 1) surfaces, which were described as a disordered (100)-c(8 × 2) structure, should contain Ga and As surface atoms in equal quantities. On (311) oriented surfaces, on the other hand, the main oxygen uptake was found to set in at the same exposures as observed with (100) and (110) oriented surfaces but then to remain smaller by approximately 20% after identical but larger exposures.