AN AB-INITIO STUDY OF POTASSIUM CHEMISORPTION ON THE GAAS(110) SURFACE

Different possible adsorption sites of potassium atoms on a gallium ar senide (110) surface have been investigated using ab initio self-consi stent unrestricted Hartree-Fock total-energy cluster calculations with Hay-Wadt effective core potentials. The effects of electron correlati on have been included by invoking the concepts of many-body perturbati on theory and are found to be highly significant. We find that the K a tom adsorption at a site modelled with a KGa5As4H12 cluster is most fa voured energetically, followed by K adsorption at the site modelled wi th the KGa4As5H12 cluster. For molecular potassium, a parallel approac h positron modelled by a K2Ga5As4H12 cluster is most favoured energeti cally followed by a vertical approach position modelled by a K2Ga4As5H 14 cluster. The effects of charge transfer from K and K2 to the GaAs s urface as well as the possibilities of metallization are also analysed and discussed.