Single crystals with an initial impurity content of less than 1ppm were used, and the diffusion profiles were determined by means of radiotracer and sectioning techniques. Transition metal diffusion occurred via vacancies, and the results for temperatures of between 352 and 441C indicated an activation energy of 1.01eV.

A.P.Batra, J.P.Hernandez, L.M.Slifkin: Physical Review B, 1980, 22[2], 734-42