Abstract
Composite films of carbon and SiO2 were prepared by a rf cosputtering technique and their photoluminescence and absorption spectra were measured. A strong and broad photoluminescence peak located around 2.2 eV (visible to the naked eye) was observed for the samples with relatively low carbon concentrations. The blue shift of the photoluminescence peak observed with decreasing carbon concentration and the increased absorption in the UV region strongly suggest that carbon clusters comparable to or smaller than C60 formed in the SiO2 matrices are responsible for the strong photoluminescence.