Ab initio studies of Cs on GaAs (100) and (110) surfaces

GaAs with an atomic monolayer of Cs is one of the best known photoemissive materials. The results of density functional theory calculations of Cs adsorption on the GaAs(100)-$(4\ifmmode\times\else\texttimes\fi{}2)$ gallium-terminated reconstructed surface and the GaAs(110) surface are presented in this work. Coverage of up to 4 Cs ${\mathrm{atoms}/\mathrm{nm}}^{2}$ on GaAs surfaces has been studied to predict the work-function reduction and adsorption energies accurately. The high mobility of Cs atoms on the (110) surface allows formation of ordered structures, whereas the low mobility of Cs of the (100) surface causes amorphous growth.