The diffusivity of Cu impurity was studied in amorphous samples which had been prepared by MeV Si implantation. The 0.0022mm-thick layers were first annealed at 500C and then implanted with 200keV Cu ions, which restored a 300nm-thick surface layer to the as-implanted state. The Cu concentration profiles were measured by using 4He back-scattering. After diffusion at temperatures of between 150 and 270C (table 149), solution partitioning was detected at sharp phase boundaries between the annealed and Cu-implanted layers. The partition coefficient could be as high as 8. The diffusion coefficient in annealed amorphous material was 2 to 5 times larger than that in as- implanted amorphous material. The activation energies were 1.39 and 1.25eV, respectively. Defects played an important role.

A.Polman, D.C.Jacobson, S.Coffa, J.M.Poate, S.Roorda, W.C.Sinke: Applied Physics Letters, 1990, 57[12], 1230-2