Optical properties of silicon nanocrystallites prepared by excimer laser ablation in inert gas

Optical properties of silicon (Si) nanocrystallites prepared by excimer laser ablation in constant-pressure inert gas have been studied in relation to the particle size. Visible photoluminescence (PL) bands in the red and green spectral regions appear at room temperature after an oxidation process. The red PL band is independent of the particle size and is stable without degradation by excitation light irradiation. It is concluded that the red PL is emitted from the surface states of the oxidized Si nanocrystallites. In contrast, the green PL band depends on the particle size. The green PL intensity decreases during excitation light irradiation in air, and then recovers in the subsequent vacuum evacuation. These results suggest that the origin of the green PL is associated with a quantum confinement effect of Si nanocrystallites.