EVIDENCE FOR SURFACE DERELAXATION INDUCED BY METALS ON III-V COMPOUNDSEMICONDUCTORS - CS INP(110)/

High resolution In 4d core and valence level photoemission spectra fro m InP(110) show that a new peak is induced by Cs adsorption, and that the surface core level (SCL) peak shifts towards larger separations fr om the bulk line with Cs coverage. While the presence of the Cs-induce d peak is related to charge transfer processes on the basis of spectra which show emission above the valence band maximum, the increase in S CL is interpreted, by recourse to tight-binding calculations, as due t o a lifting of the bond angle rotation-relaxation of the clean surface . These findings provide a consistent interpretation of changes in the electronic structure of the surface upon alkali metal deposition, and a basis for a valid model function for investigations of Fermi level movement through core level line shape analysis.