XPS AND LEISS STUDIES OF ION-BOMBARDED GASB, INSB AND CDSE SURFACES

Ion bombardment effects in GaSb, InSb and CdSe crystal surfaces were s tudied with a combination of X-ray photoelectron spectroscopy (XPS) an d low energy ion scattering spectroscopy (LEISS). Both XPS and LEISS s howed that neglecting surface contamination, the composition of the cr ystal surfaces prior to ion bombardment were close to their stoichiome tric values of 1 : 1. During 3 keV Ar+ beam bombardment, XPS analysis showed that the atomic ratios of Sb/Ga, Sb/In and Se/Cd in the bombard ed surfaces decreased from 1 to 0.71, 0.92 and 0.87, respectively. LEI SS results, however, indicated that these ratios increased to 3.33, 1. 63 and 1.32, respectively. The variances between XPS and LEISS measure ments are attributed to a difference in the sampling depth between the two techniques, and give a clear indication of how ion bombardment ch anges the surface composition of these compound semiconductors. These changes may be described in terms of bombardment-induced Gibbsian segr egation.