Angular distribution of Ga+ ions desorbed by 3-keV ion bombardment of GaAs(110)

Angular distributions of Ga+ ions desorbed from GaAs(110) surfaces by 3-keV Ar+-ion bombardment under low-dose conditions have been determined. The distributions exhibit a high degree of anisotropy along the 100 crystallographic direction with smaller peaks observed in several other specific directions. Using simple geometric analyses and with microscopic insight extracted from results of molecular-dynamics computer simulations on Si(110), we have been able to identify the scattering mechanisms that give rise to these peaks. The most dominant feature is found to arise from a specific collision sequence wherein a surface atom is ejected by direct collisions with a second-layer atom along the bond direction. This mechanism is interesting in that it contrasts with the channeling and blocking mechanisms previously reported for fcc metals. The positions of other peaks in the angular distributions have been determined with use of simple geometrical arguments. We also examine the expected effect of the known GaAs(110) surface reconstruction on the observed patterns. These results should prove useful for testing molecular-dynamics calculations on ion-bombarded GaAs targets and may ultimately lead to a new approach to examining the surface structure of these types of complex materials.