A direct comparison was made of the rates of bulk versus surface transport for Ni, in and on Si(111), by depositing a laterally confined dot of Ni onto one side of a doubly-polished and ultra-high vacuum-cleaned Si wafer and measuring the lateral Auger profile on the reverse side following annealing and quenching. It was found that the Ni reached the far side of the wafer, at temperatures as low as 550C, via bulk diffusion with no measurable contribution from surface paths; which were short-circuited by numerous fast bulk paths. Similar results were found for Ni and Co on Si(111) and Si(100).

M.Y.Lee, P.A.Bennett: Physical Review Letters, 1995, 75[24], 4460-3