The adatom diffusion barrier, the exchange barrier to incorporation, and the energy gain due to incorporation into the As layer were calculated, for a Si adatom on a Si(111) surface which was passivated by an As surfactant layer, by using an  ab initio  total energy and force method. It was found that the activation energies for surface diffusion and exchange were similar in magnitude, and were much smaller than the activation energy for the re-exchange process. It was proposed that adatoms were rapidly incorporated into the As layer, and that the effective diffusivity was determined by the re-exchange process.

Re-Exchange Controlled Diffusion in Surfactant-Mediated Epitaxial Growth - Si on As-Terminated Si(111). K.Schroeder, B.Engels, P.Richard, S.Blügel: Physical Review Letters, 1998, 80[13], 2873-6