Angular distribution of GaAs sputtered under oblique Cs + bombardment

Abstract

The angular distribution of Ga and As sputtered from Gallium Arsenide (1 0 0) by a Cs + ion beam was experimentally measured through a collector technique allowing modifications of the energy and incidence angle of the ion beam. The impact energy was varied in the range of 2–10 keV and the angle of incidence from 30° to 60°. The angular distributions of emitted matter are determined by means of SIMS depth profiles. Our series of experiments show an evolution of the preferential direction of emission as well as the spreading around this direction in function of the characteristics of the ion beam. The second objective is the study of the evolution of the stoichiometry of the deposit in function of the emission angle. A decrease of the As/Ga ratio around the preferential direction of emission and an increase of this ratio for oblique emission are observed for different conditions of primary bombardment. Considering that the angular distribution depends on the depth of origin, our results suggest that the Cs + bombardment changes the stoichiometry of the near-surface layers of the sample with an enrichment of As in the outmost layers while the sub-surface region is impoverished in As due to preferential sputtering.