The migration of Si on the (001) surface was investigated by analyzing the number density of islands which was formed during deposition. By comparing the data with the predictions of various models, it was deduced that diffusion in the fast direction (along surface dimer rows) was described by:

D(cm2/s) = 1 x 10-3exp[-0.67(eV)/kT]

The associated model involved the assumption of anisotropic bonding and a 1:1000 diffusion anisotropy.

Activation Energy for Surface Diffusion of Si on Si(001): A Scanning-Tunneling-Microscopy Study. Y.W.Mo, J.Kleiner, M.B.Webb, M.G.Lagally: Physical Review Letters, 1991, 66[15], 1998-2001