Charge transfer and redistribution in the formation of the K/GaP(110) interface: a photoelectron spectroscopy study

We present the results of a photoelectron spectroscopy study of the K/GaP(110) interface grown at T = 120 K. We have investigated the system looking at the Ga 3d and P 2p core level spectra by analysing their lineshape. This analysis shows that the transferred charge in the adatom-substrate bonding formation affects the electronic and chemical environment of both surface Ga and P atoms. The results suggest relevant differences with the intuitive picture of strong ionic localized bonding between the alkali atom and surface Ga. They are instead more consistent with a delocalized redistributed valence charge between the adsorbate and the substrate. We also conclude that the system at ML is metallic, with an increasing disorder and inhomogeneity at the highest coverage studied. The similarities and differences with the Na/GaP(110) and the other alkali metal/GaAs(110) systems are discussed.