ANGULAR-DISTRIBUTION OF PARTICLES SPUTTERED FROM GAAS BY AR-BOMBARDMENT( AND XE+ ION)

We report the measurement on the angular distribution of Ga and As par ticles ejected from GaAs (100) surface bombarded with normally inciden t 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-a mbience 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 pronoun ced 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 concentratio n is higher at the outermost layer than in subsurface region beneath t he outermost layer. It is also demonstrated that As atoms were segrega ted at outermost surface even at a sputtering temperature as low as -1 20 degrees C.