X-RAY PHOTOELECTRON DIFFRACTION AND SURFACE CORE-LEVEL SHIFT STUDY OFCLEAN INP(001)

A clean InP(001) surface treated by ion-bombardment and annealing (IBA ) has been studied by X-ray photoelectron diffraction (XPD) and synchr otron radiation based photoemission spectroscopy (SRPES). The XPD patt ern of In 3d(5/2) (measured at 550 from the surface normal) is compare d with a calculated XPD pattern obtained from a single-scattering clus ter simulation. Our results indicate that IBA-treated InP(001) exhibit s a (2 x 4) surface reconstruction. That is, the two-fold and four-fol d directions correspond to the [<1(1)over bar>0] and [110] axes, respe ctively. For the SRPES study, In 4d core-level spectra (h nu = 70 eV) were collected at a variety of photoemission angles. Four spin-orbit d oublets were necessary to obtain a high-quality fit to the photoemissi on spectra. As the detection angle was changed toward the surface para llel, a component having a lower binding energy by 0.70 eV than that o f the bulk undergoes a dramatic intensity increase. On the basis of th e energy shift and polar angle dependence of this component, we sugges t that it arises from surface-layer indium atoms bonded to other indiu m atoms. The origins of other components are discussed. (C) 1998 Elsev ier Science B.V. All rights reserved.