AES study of electron-beam-induced interactions between oxygen and the Ge(111) surface

For a Ge(111) surface irradiated by an electron beam of 1.5-keV energy and current density of 2 μA mm−2, it was found that beam-assisted oxygen adsorption at pressures <10−9 Torr always resulted in carbon-contaminated overlayers and was probably due to dissociation of physisorbed CO. The sticking coefficient s of CO was 0.08. At oxygen pressures ≳10−6 Torr, carbon-free coverages could be formed, even without irradiation. s for oxygen was 6×10−4 for beam-assisted and 1.5×10−4 for nonassisted adsorption. Electron impact desorption followed a first-order rate equation and the desorption cross section for oxygen was 6×10−20 cm2.