Photoluminescence spectra of clusters of group IV elements embedded in SiO2 matrices

Using a rf co-sputtering technique, SiO₂ films containing C, Si and Ge atoms were prepared and their Raman and photoluminescence spectra were measured. Raman spectra obtained are very broad indicating that the group IV elements are embedded in the form of clusters. The samples containing C clusters showed a very strong photoluminescence peak at around 2.1～2.2eV (visible with naked eye). The films containing Ge and Si clusters showed luminescence peaks at around 1.6～1.8eV. Strong luminescence was not observed for the samples containing well grown microcrystals a few nanometers in diameter.