Formation of Small-Sized CdS//xSe//1-x Crystals in Sol-Gel-Derived SiO//2 Glasses
Silica glasses doped with small-sized CdS//xSe//1-x crystals were prepared by the sol-gel method. Gels synthesized by the hydrolysis of Si(OC//2H//5)//4, in the presence of CdSeO//4 with NH//4SCN dissolved in HNO//3 or NH//4OH, were heatedin H//2-N//2 atmosphere. The pH value of solutions for CdSeO//4 and NH//4SCN primarily determined the fraction of anions in CdS//xSe//1-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 sizeincreased, and the emission spectra showed a sharp band near the absorption edge position and a broad tail extending into the long wavelength. The optical bandgap energies increased reciprocally proportional to the square of the crystal size.
Masayuki Nogami.?Yoshihiro Abe.?