The adsorption and diffusion of Ge adatoms upon fully-relaxed (100) 2 x 1 surfaces was studied by using molecular dynamics methods, Tersoff's potential for the description of Ge-Si interactions, simple transition-state theory, and lattice-gas simulators. It was found that there were 6 local minima for adsorption at the surface, and the associated activation energies were determined. The resultant diffusivity could be described by:

D(cm2/s) = 4.3 x 10-4 exp[-0.73(eV)/kT]

It was also found that the adatom diffusion was anisotropic in nature, and that the direction of easy diffusion was perpendicular to the dimers of the original surface; that is, parallel to the dimer rows. A comparison with Si adatom diffusion showed that Ge adatom diffusion was less anisotropic, and that Ge adatoms diffused between 2 and 3 times more slowly than did Si adatoms (on a given surface). The diffusion coefficients for Ge and Si adatom migration perpendicular to the dimer rows were found to be described by:

Ge: D(cm2/s) = 2.8 x 10-3 exp[-1.17(eV)/kT]

Si: D(cm2/s) = 4.8 x 10-3 exp[-1.20(eV)/kT]

D.Srivastava, B.J.Garrison: Physical Review B, 1992, 46[3], 1472-9