SURFACE COMPOSITIONAL CHANGES OF INP DUE TO KRYPTON ION-BOMBARDMENT

Sputtering of the (110) and (100) surfaces of InP by Kr+ ions resulted in a preferential loss of the phosphorus species leaving an In-enriched surface. The equilibrium Kr+ -sputtered surface composition of InP was determined by means of Auger electron spectroscopy. The sputtered surface composition ratio was independent of crystal orientation and ion energy (between 0.5 and 5 keV). Owing to a lack of other experimental krypton sputtering data, the experimentally obtained surface composition ratios were compared to the Sigmund theory for preferential sputtering in the linear cascade regime. A comparison with the Sigmund spike model showed the absence of spike effects in this krypton ion energy regime. A reasonable agreement was obtained between the experimental results and the Sigmund predictions. There was a correlation between the angle of incidence of the bombarding Kr+ ions and the final surface composition: The preferential sputtering effect became less with increasing angle of incidence theta(i) (measured from the surface normal). The results show that the ratio of the phosphorus to indium compositions, namely X(P)s/X(In)s is-proportional-to (cos theta(i)-a with a congruent-to 0.24, and where theta(i) is the angle of incidence of the ion beam with respect to the sample normal. This result is explained in terms of a model using the angle dependence of the sputtering yield of the constituent elements.