Structural and optical properties of Si-nanoclusters embedded in silicon dioxide

In this paper we report on light emission from silicon nanostructures embedded in silicon oxide prepared by rf co-sputtering in argon of pure silicon and silicon dioxide. The concentration of excess silicon was varied in the range 0.5–1.8%. Specimens were subjected to thermal anneals up to 1100 °C in nitrogen atmosphere. The effects of annealing on photoluminescence spectra and crystallization of a-Si as well as the chemical feature of the Si 2p core level were studied. Stable blue and green luminescence was observed with intensities strong enough to be visible to the naked eye from samples which were excited by ultraviolet light. In the as-deposited samples and after anneals below 600 °C, the luminescence around 440 nm is ascribed to structural defects in the SiO 2 film. For anneals above 600 °C the emissions at wavelengths 370, 445 and 537 nm were attributed to excitons bound at structural defects in an interfacial layer between a silicon nanoparticle with crystalline core and surrounding amorphous SiO 2.