Metastable alloy formation in lead implanted nickel

Metastable lead-nickel alloys were produced by room temperature random implantations of 240 keV Pb+ ions into Ni (1 1 0) single crystals to a fluence of 1016 cm-2. Rutherford backscattering (RBS)/channeling analysis supplemented with transmission electron microscopy (TEM) showed that the alloy was in form of a supersaturated substitutional solid solution with a peak Pb concentration of 2.4 at.% while a fairly small fraction of the implanted Pb was confined within nanoscale precipitates. The precipitates were found to be mostly single crystalline with size in a range from about 2 to 15 nm although bi-, tri- and even tetracrystals were occasionally observed. Post-implantation annealing at different temperatures up to 860 K leads to a strong outdiffusion of a substantial fraction of the implanted lead. Upon annealing, the lattice occupancy of the originally substitutional lead atoms was found to change to different types of lattice locations (regular and displaced substitutional, octahedral interstitial and random) which appeared to be strongly correlated with the temperature of annealing