Transformation to amorphous state of metals by ion implantation: P in Ni

The amorphization of Ni single crystals by P ion implantation was studied via in situ Rutherford backscattering and channeling experiments. Both the P-implant and the Ni-disorder profiles were analyzed. At 90 K, no P mobility was found under implantation. The fluence dependence of the disorder level is analyzed in terms of amorphous-cluster formation above a threshold P concentration. The radius of the clusters is four interatomic distances, i.e., the correlation length of a typical amorphous lattice as determined in structure-sensitive experiments. The amorphous fraction α in the implanted layer is α=0.5 when x∼0.12 (${\mathrm{Ni}}_{1\mathrm{-}\mathrm{x}}$ ${\mathrm{P}}_{\mathrm{x}}$) and α=1 when x∼0.15. At 300 K, short-range P motion occurs during implantation. Amorphous clusters are formed even at low P concentrations (x∼0.05). The P-to-Ni ratio in the clusters is that of the eutectic, and we found α=1 at the eutectic composition. There is evidence that the amorphization mechanism described in this paper also holds for other metal-metalloid systems.