Effect of high-power nanosecond and femtosecond laser pulses on silicon nanostructures

The effect of high-power nanosecond (20 ns) and femtosecond (120 fs) laser pulses on silicon nanostructures produced by ion-beam-assisted synthesis in SiO2 layers or by deposition onto glassy substrates is studied. Nanosecond annealing brings about a photoluminescence band at about 500 mn, with the intensity increasing with the energy and number of laser pulses. The source of the emission is thought to be the clusters of Si atoms segregated from the oxide. In addition, the nanosecond pulses allow crystallization of amorphous silicon nanoprecipitates in SiO2. Heavy doping promotes crystallization. The duration of femtosecond pulses is too short for excess Si to be segregated from SiO2. At the same time, such short pulses induce crystallization of Thin a-Si films on glassy substrates. The energy region in which crystallization is observed for both types of pulses allows short-term melting of the surface layer.