Optical properties of CdS nanocrystals-doped in silica glasses prepared by the sol-gel method

Nano-sized CdS semiconductor particles have been prepared in the porous SiO₂ glasses by a sol-gel process. The xerogel have been used as a template for particles growing within the pore of this amorphous material. The control of porous structure formation was carried out by the use of organic directing agents and processing conditions. The CdS phase was characterized by X-ray diffraction and micro-Raman spectroscopy. The optical properties such as absorption and fluorescence spectra of these CdS nanocrystallines embedded in the silica glass matrix are presented. The improvement of nanocrystal quality and the sharpening of the size distribution by thermal annealing are also investigated versus time and temperature of treatment. The fluorescent spectrum shift from 467 nm to 398 nm and absorption spectrum shift from 470 to 280 nm are observed by change of the temperature treatment. It is shown that we can keep a control on the crystalline, size and size distribution of the CdS nanocrystals in the silica glasses by sol-gel method. The dielectric constant of this material is measured