Angular distribution of particles sputtered from GaAs by Ar+ and Xe+ ion bombardment

We report the measurement on the angular distribution of Ga and As particles ejected from GaAs (100) surface bombarded with normally incident 1, 2 and 3 keV Ar+ and Xe+ ions at room temperature and -120 degrees C. Sputter ejected material was collected onto an Al foil under UHV-ambience and was subsequently analyzed by electron probe microanalysis (EPMA) to obtain its angular distribution. Every angular distribution, except for those of As obtained with 1 keV Ar+ and Xe+ bombardments, showed over-cosine tendency. The over-cosine tendency was more pronounced with increasing sputtering energy, independent of the ion species. A preferential ejection of Ga in the forward direction was discerned for both Ar+ and Xe+ bombardments, suggesting that the As concentration is higher at the outermost layer than in subsurface region beneath the outermost layer. It is also demonstrated that As atoms were segregated at outermost surface even at a sputtering temperature as low as -120 degrees C.