An investigation was made of the diffusive behavior of a single Ga adatom, on the (100)-c(4 x 4) surface, by using the local-density approximation and the all-electron projector augmented wave method. The ground-state geometry of the (100)-c(4 x 4) surface was determined by using the projector augmented wave method, and was found to agree with experimental data and with previous calculations. The binding energy for a lone Ga adatom on this reconstruction was calculated as a function of the surface position. On the basis of these data, 3 relatively stable adsorption sites were identified. In order of increasing energy, these sites were site-1 (center of the missing dimer position), site-2 (between dimer rows and adjacent to a center dimer) and site-3 (between dimer rows, adjacent to an edge dimer). The surface diffusion activation energies were also estimated. The smallest was 0.14eV, for the 3 → 2 transition, and the largest was 0.45eV, for the 2 → 3 transition. Kinetic Monte Carlo simulations which incorporated these data indicated that diffusion on this surface took place mainly via diffusion pathways that passed through the strongest binding site (site-1). This site effectively controlled diffusion in directions that were parallel or perpendicular to the dimer rows.

Ab initio calculation of binding and diffusion of a Ga adatom on the GaAs(001)-c(4 x 4) surface J.G.LePage, M.Alouani, D.L.Dorsey, J.W.Wilkins, P.E.Blöchl: Physical Review B, 1998, 58[3], 1499-505