Surface core-level shifts on InP(110): Experiments and Madelung energy calculations

Photoelectron spectra of the In 4d and P 2p core levels recorded on clean, cleaved InP(110) surfaces with high resolution reveal surface core-level shifts of similar magnitude on both core levels, in contradiction to recent tight-binding calculations and an experimental study, where only a shift on the indium level was found. We have performed surface core-level-shift calculations which take into account the Madelung shift for the relaxed zinc-blende (110) geometry, and show that this contribution alone can explain the major part of the observed shifts.