FORMATION OF SMALL-SIZED CDSXSE1-X CRYSTALS IN SOL-GEL-DERIVED SIO2 GLASSES

Silica glasses doped with small-sized CdSxSe1-x crystals were prepared by the sol-gel method. Gels synthesized by the hydrolysis of Si(OC2H5)(4), in the presence of CdSeO4 with NH4SCN dissolved in HNO3 or NH4OH, mere heated in H-2-N-2 atmosphere. The pH value of solutions for CdSeO4 and NH4SCN primarily determined the fraction of anions in CdS2Se1-x crystals. The anion content in crystals was dependent on the pH value of the solvent and/or heat-treatment temperature, and the sulfur fraction changed from 0.1 to 0.6. The optical absorption spectra were red-shifted as the selenium content and the crystal size increased, and the emission spectra showed a sharp band near the absorption edge position and a broad tail extending into the long wavelength, The optical band gap energies increased reciprocally proportional to the square of the crystal size.