X-ray standing wave study of wet-etch sulphur-treated InP(100) surfaces

Abstract

Normal incidence X-ray standing wave (NIXSW) measurements are presented for sulphur terminated InP(100) surfaces, prepared by wet-etch in (NH 4) 2S solution followed by UHV anneal. Standing wave profiles for sulphur 1s photoyield in three planes (220, 311 and 31 1 ) indicate that sulphur is close to the phosphorus site. Coherent positions and fractions are compared with the predictions of a number of models of the surface, including novel 2×2 structures. The experimental data can be reproduced by a general two-dimer model, but it is more likely that the data are reflecting significant disorder.