Effect of pressure annealing on formation of light-emitting Si nanocrystals in Si rich SiO2

Four types of Si rich SiO2 layers on the Si substrates have been prepared by Si ion implantation or by magnetron co‐sputtering of the Si and SiO2 targets. The types differed from each other in the contents of excess Si, which were about 5 at%, 15 at%, 25 at% and 35 at%. High temperature (up to 1100 °C) anneals of the samples were performed in neutral ambient under normal or elevated (up to 1.5 GPa) hydrostatic pressures. Photoluminescence spectroscopy, Raman scattering and electron diffraction were used for the characterizations. For the lowest concentration of the excess Si the high‐pressure annealing prevents the formation of the light‐emitting Si nanocrystals, but stimulates an appearance of the centers luminescing in the visible range. These centers are believed to be numerous Si nanoclusters, segregated from the oxide network. Increase in Si content provides during the high‐pressure anneals the formation of the quantum‐size Si nanocrystals able to emit strong PL near the wavelength of 800 nm. The effect of the high‐pressure annealing is ascribed to the enhanced energetically favorable segregation of Si from the oxide network. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)