A tracer technique using radioactive 56Ni* was applied to investigate the growth mechanisms of Ni2Si, NiSi and NiSi2 on Si〈100〉 and Si〈111〉 wafers. A thin Ni* tracer layer initially at the Ni-Si interface was observed to migrate and spread during the growth of nickel silicides at 350, 450 and 800 °C. These data are discussed, together with other results from 31Si* tracer work and xenon marker experiments. Ni appears to be the dominant moving species in all cases, diffusing both substitutionally and by grain boundary paths (in comparable amounts) for Ni2Si and substitutionally for NiSi and NiSi2. © 1982.