Measurements of the contact potential difference were made before and after diffusion annealing, and were used to estimate the diffusivity of Al on clean (l11) surfaces of single crystals of n-type material. It was found that, at between 400 and 700C, the surface diffusivity parallel to the surface could be described by:

D(cm2/s) = 1 x 10-1exp[-0.7(eV)/kT]

The surface diffusivity both parallel and perpendicular to the surface was much greater than the bulk diffusivity.

B.A.Nesterenko, V.A.Zrazhevskii, V.T.Rozumnyuk: Fizika Tverdogo Tela, 1978, 20[5], 1901-3