Different possible adsorption sites of cesium atoms on a gallium arsenide (110) surface have been investigated using ab initio self-consistent unrestricted Hartree-Fock total-energy cluster calculations with Hay-Wadt effective-core potentials. The effects of electron correlation have been included by invoking the concepts of many-body perturbation theory and are found to be highly significant. We find that the Cs atom adsorption at a site modeled with a ${\mathrm{CsGa}}_5$${\mathrm{As}}_4$${\mathrm{H}}_{12}$ cluster is most favored energetically followed by Cs adsorption at a site modeled with the ${\mathrm{CsGa}}_4$${\mathrm{As}}_5$${\mathrm{H}}_{12}$ cluster. For molecular cesium, a site modeled by a ${\mathrm{Cs}}_2$${\mathrm{Ga}}_6$${\mathrm{As}}_9$${\mathrm{H}}_{21}$ cluster is most favored energetically. However, here all four sites considered remain competitive energetically at the correlated levels of theory. The effects of charge transfer from Cs and ${\mathrm{Cs}}_2$ to the GaAs surface and the possibilities of metallization are also analyzed and discussed.

• Received 28 July 1994

DOI:https://doi.org/10.1103/PhysRevB.50.14255