Segregation Effects in Cu-Implanted Si after Laser-Pulse Melting

Cu-implanted Si crystals were irradiated with $Q$-switched ruby-laser single pulses. After irradiation with energy density in excess of 1.0 J/${\mathrm{cm}}^2$, the Cu atoms accumulate at the sample surface. Thermal annealing in the 500-800°C range casues a migration of Cu inside the specimen, in agreement with diffusion coefficient and solid solubility values. The results indicate the formation of a liquid layer induced by laser irradiation. The solid-liquid interface movement during freezing qualitatively justifies the observed surface accumulation.