Formation of Periodic Ripple Structures in Picosecond Pulsed Laser Annealing of Ion-Implanted Silicon

Temporal changes in the self-reflectivity of a picosecond excitation pulse in laser annealing of ion-implanted silicon were measured, and the surface morphologies after annealing were studied. At intensities above the damage threshold, the reflected signal decreases, and simultaneously periodic ripple structures appear around the laser-induced damaged region. These ripple structures are formed by interference between a pulse wave originating as a result of scattering at the damaged point and propagating on the non-damaged surface, and the rear part of the incident pulse wave illuminating the non-damaged surface.