Core level analysis of the K/GaP(110) interface

The results of a photoelectron spectroscopy study of the K/GaP(110) interface grown at T=120 K are presented for the first time. The analysis shows a big core level shift at lower binding energies (Delta E=1.6 eV at a coverage theta=0.1 ML) for the P 2p core level spectra. We interpret this result in terms of a charge redistribution affecting both types of atoms of the first substrate layer, suggesting some differences from the intuitive picture of strong ionic localised bonding between the alkali and the surface Ga atom.