Simulation of Na, K, Cs and Cs(O) adsorption on GaAs(1Â 1Â 0) and (1Â 0Â 0) surfaces: towards predictable electronic structure of activation layer

Ab-initio full-potential linearized augmented-plane-wave method is used to elucidate interaction of the surface states of a GaAs substrate with different adsorbates. Simulation of the electronic structure of clean ideal and relaxed GaAs (1 0 0) and (1 1 0) surfaces as well as surfaces with thin overlayers of alkali metals was performed to obtain the coverage dependence of the work function. Results are found to be in satisfactory agreement with experimental data. The role of oxygen during cesium adsorption is also studied. The formation of activation layer and its electronic structure are discussed.