Synthesis of silicon nanoparticles and impurity doping by laser ablation

We have utilized pulsed-laser ablation in ambient inert gas to synthesize silicon (Si) nanoparticles and to perform surface modification and impurity doping. The dynamical growing process of Si nanoparticles has been investigated by measuring time-resolved light emission induced by the second pulsed-laser irradiation with a delayed time. It was found from the time-resolved measurements that the onset of the formation of Si nanoparticles appears at around I ms, dependent on inert gas pressure and laser fluence. We demonstrate that light emission can be controlled by adding hydrogen or oxygen gas to inert gas. It is also demonstrated that the thermal quenching which has been serious problem in Er-doped semiconductors can be removed in 1.54 mum photoluminescence of Er-doped Si nanocrystallites. These results suggest that laser ablation is useful not only for synthesis of nanostructured materials such as nanoparticles and nanowires/nanotubes, but for their surface modification and impurity doping that are important techniques for realizing functional nanostructures.