The diffusive behavior of Cu on the (111) surface of 4N7-purity material was studied at 890 to 1015C. The results could be described by:

D (cm2/s) = 6.3 x 10-1 exp[-1.18(eV)/kT]

K.Höhne, R.Sizmann: Physica Status Solidi A, 1971, 5[3], 577-89