ENERGETICS AND STRUCTURE OF ORDERED SB OVERLAYERS AND SB CLUSTERS ON GAAS(110) PROBED BY AB-INITIO CALCULATIONS

Ab initio density-functional theory calculations of Sb-covered GaAs(11 0) surfaces are performed for different coverages, different 2D transl ational symmetries, and various structural models. The highest adsorpt ion energy is found for monolayer coverage (THETA = 1), 1 x 1 translat ional symmetry, and the epitaxial continued layer structure. The energ y gains for similar structures in the submonolayer case with lower tra nslational symmetry are slightly smaller. Our results indicate a tende ncy for the formation of anisotropic islands for THETA < 1 growing tog ether in an ordered overlayer for THETA = 1.