Fabrication and temperature-dependent photoluminescence of silicon-silicon oxide core-shell nanoparticle thin film.

A novel Si nanocrystals embedded SiO2 thin film has been fabricated by the synthesis of Si-SiO2 core-shell (Si@SiO2) nanoparticles via the surface SiO2 coating of Si nanocrystals and the followed drop-coating on a silicon wafer. The resultant Si@SiO2 nanoparticles had a mean diameter of 30.43 +/- 2.63 nm and a mean shell thickness of 13.16 nm. They exhibited a stronger peak around 360 nm and a weaker green-yellow emission around 530 nm. The 360 nm peak could be attributed to the electron-hole recombination in the Si cores and that via the oxide-related defects originally present on the surface of oxide-passivated Si cores, while the green-yellow emission might be attributed to the transfer of the electron-hole pairs generated in the Si cores across the core-shell interface and the followed recombination in the SiO2 shells. The resultant Si@SiO2 nanoparticle thin film had a mean grain size of about 100 nm. It showed not only blue emission and green-yellow emission but also red emission which might be due to the transfer of the electron-hole pairs generated in the Si cores across the core-shell interface and the followed recombination via the Si==O double bonds at the particle surface. Because blue emission was significant relatively, both the Si@SiO2 nanoparticles and Si@SiO2 nanoparticle thin film still exhibited bright blue fluorescence under UV excitation. In addition, by investigating the temperature dependence of photoluminescence in the temperature range of 77 to 297 K, the nature of photoluminescence from the Si@SiO2 nanoparticle thin film was also clarified.