Photoluminescence degradation and passivation mechanisms of Si nanoclusters in silicon oxide matrix

The Si nanoclusters embedded in a silicon oxide matrix were prepared using a laser-assisted chemical vapor deposition (LACVD) system. A degradation of photoluminescence (PL) by irradiating the sample with helium-cadmium (He-Cd) laser was observed. The dependence of PL degradation on long-term irradiation of He-Cd laser was investigated. We found that the He-Cd laser-induced breakage of Si-H-related bonds resulted in the formation of Si dangling bonds such as D centers and Pb centers, which are known to decrease PL intensity. The PL intensity of He-Cd laser-irradiated samples can be increased to that of as-deposited samples after exposing the samples to a H₂ ambient at 400°C for 5 min. Post annealing in H₂ could also help increase PL intensity by passivating the defect centers in as-deposited samples.