SOL-GEL PROCESSING OF SMALL-SIZED CDSE CRYSTAL-DOPED SILICA GLASSES

The sol-gel process has been applied to the preparation of small-sized CdSe-doped silica glasses with a significant quantum-sized effect. Gels synthesized by the hydrolysis of complex solution of Si(OC2H5)4, Cd(CH3COO)2.2H2O and Se were heated above 300-degrees-C in hydrogen-nitrogen atmosphere to form hexagonal CdSe microcrystals. The sizes of CdSe crystals, determined from the line broadening of X-ray diffraction pattern, increased from 3 to 10 nm diameter with increasing temperature of the heat treatment. The optical absorption spectra are red shifted as the crystal size increases, and the gap energy is reciprocally proportional to the square of the crystal size. This result is interpreted in terms of quantum size effect of small crystals and the effective reduced mass is estimated to be 0.36m0 which is about three times larger than that calculated from the theoretical prediction.