Pulsed laser irradiation of lead-implanted single-crystal copper films

Abstract

We have studied the effect of pulsed laser annealing on single-crystal copper films implanted with lead to a concentration far in excess of equilibrium solid solubility. A Nd:YAG frequency-doubled 50-ns-pulsed laser was used, with power density up to 2.4 J/cm2. Channeling of 2-MeV helium ions was used to determine the concentration profile and degree of substitutionality of the lead both before and after laser irradiation. The near-surface region is melted if irradiated with a laser pulse of adequate energy density. The Pb atoms are redistributed and some accumulate near the sample surface. The fraction of Pb atoms which remain substitutional is nearly the same for as-implanted and laser-irradiated samples. This indicates that the rapid quenching following laser annealing (∼1011 K/sec) is almost as effective in retaining Pb atoms in metastable solution in Cu as the original effective quenching (∼1014 K/sec) following Pb implantation. Furnace annealing at 250°C for 30 min greatly reduces the substitutional fraction of Pb atoms, as expected.