Defect Generation and Evolution in Laser Processing of Si

In this work concerted experiments and theoretical analysis are applied to conclusively demonstrate the vacancy generation during fast melting and re-growth of Si by laser irradiation. Experiments, based on the positron annihilation spectroscopy and designed to test the theoretical predictions, evidence a vacancy super-saturation after the laser process The dependence on the pulse energy and number of shots of the residual damage, after a multi shot laser irradiation process, is characterised by means of these measurements. Kinetic Monte Carlo simulations of the molten Si re-crystallization show trapping of vacancies in the re-crystallized region. The main outcome of this simulation is the dependence of the vacancy's generation efficiency on under-cooling. The knowledge of this dependence allows us to implement a continuum model (based on kinetics equations for the phase, the free defect and clustered defects) aimed to simulate the damage evolution during the pulse duration and in the time interval between two successive pulses. These continuum kinetic simulations of the full process show a defect evolution in close agreement with the experiments.