ACCOMMODATION OF ARGON AND OXYGEN GASES ON A GAAS(110) SURFACE UNDER AR+ ION-BOMBARDMENT

Intensities of Ar+ ions scattered by Ga and As atoms on the GaAs(110) surface under a sputtering equilibrium condition attained by 7 keV Ar+ ion beam irradiation were measured as a function of Ar and O2 pressures at room temperature. All scattered ion signals decayed linearly as the gas pressure increased, indicating that the surface concentrations of these gases are proportional to the gas pressure. This means that the ratios of the surface accommodation probability to the ion-induced removal cross section of these gases are constant. Results also showed that the As signal decayed faster than the Ga signal as the O2 pressure increased, while these signals decayed with the same slope as the Ar pressure increased. This suggests that an oxygen atom is preferentially trapped at an As vacancy site rather than at a Ga vacancy site on the sputtering front.