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 Theta = 1 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.