Photoluminescence from low thermal budget silicon nano-crystals in silica

We have developed a novel method to fabricate Si nanocrystals in a silica matrix with a considerably reduced thermal budget using pulsed laser deposition. Normally, Si nanocrystals are formed through phase separation by annealing a Si-rich SiO2 film at 1100 degrees C; we show Si nanocrystal formation in as-deposited films at 550 degrees C. We suggest the mechanism for this is through surface diffusion during deposition. We also show the ability to vary the size of these nanocrystals by adjusting the deposition conditions and can increase their size through annealing. If the nanocrystals are small they have excellent photoluminescence properties however larger nanocrystals have poor luminescence.