Preparation of Semiconducting Sulfides Microcrystalline-Doped Silica Glasses by the Sol-Gel Process,
AICHI INST OF TECH TOYOTA (JAPAN)
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The sol-gel process has been applied successfully to the preparation of small-particle-size ZnS, CdS or PbS-doped silica glasses with a significant quantum size effect. Gels prepared through the hydrolysis of complex solutions Of SiOC2H54 and acetate of Zn, Cd or Pb were heated at 500 to 900oC, then reacted with H2S gas to form fine microcrystals doped glasses. From X-ray diffraction analyses and transmission electron micrographs, these crystals were cubic ZnS, hexagonal CdS and cubic PbS crystal, respectively, and their sizes were 2 to 8 nm in diameter. In the optical absorption spectra, the absorption edge exhibited a blue shift compared with those of the bulk sulfides crystals. Size dependence of energy shift was discussed in relation to size quantization of electron-hole in microcrystals. The nonlinearity was estimated to be 1. 5 x 1010 esu for 2 CdS doped glass.