BULK VERSUS SURFACE TRANSPORT OF NICKEL AND COBALT ON SILICON

We compare directly the rates of bulk versus surface transport for Ni in and on Si(111) by depositing a laterally confined dot of Ni on one side of a double-polished and UHV cleaned Si wafer and then measuring the lateral Aug er profile on the reverse side following annealing and quenching. Ni reaches the far side of the wafer at temperatures as lo w as 550 degrees C via bulk diffusion with no measurable contribution from surface paths, which are short circuited by numerous, fast bulk p aths. Similar results are found for Ni and Co on Si(111) and Si(100). Implications for silicide reactions in general are described.