The dynamics of surface rearrangements in Si adatom diffusion on the Si{100}(2x1) surface

The Si adatom adsorption and diffusion on the fully relaxed Si{100}(2X1) surface is studied by a combination of molecular dynamics simulations with Tersoff's potential for the Si interactions, a simplified transition state theory of Voter and lattice gas simulations. Six local minima for adsorption are found on the surface and the activation energies between each are determined. The Arrhenius behavior for the macroscopic diffusion is found to be D = 5.67 X 10^-3 exp(-0.75 eV/kT) cm²/s. In addition, it is found that the adatom diffusion is strongly anisotropic in nature and the direction of easy diffusion is perpendicular to the dimers (i.e., parallel to the dimer rows) of the original surface. The minimum energy path for the diffusion is found to be activated by the local unreconstruction (dimer opening) of the otherwise fully reconstructed surface.