Ion angle dependence in the preferential sputtering of InP

The dependence of the equilibrium Ar +-sputtered surface composition of InP on the angle of incidence of the Ar + ions was investigated by means of Auger electron spectroscopy. Phosphorus atoms were preferentially sputtered from InP leaving an In-enriched surface. There is a correlation between the angle of incidence of the bombarding Ar + ions and the final surface composition: The preferential sputtering effect became less with increasing angle of incidence θ i (measured from the surface normal). The results show that the ratio of the phosphorus-to-indium compositions, viz. C s p C s In ∝( cos θ i) −a with a = 1.7. This ratio was independent of crystal orientation and ion energy (between 0.5 and 5 keV). The results are in qualitative agreement with other published data. A similar fit to another set of reported data gave a = 1.1.