OPTICAL AND ELECTRICAL PROPERTIES OF PURE AND RARE-EARTH-DOPEDnc-Si/SiO2COMPOSITES PREPARED BY RF COSPUTTERING

Photoluminescence and optical absorption spectra from silicon nanoparticles embedded inSiO2are presented. The material was synthesized by RF cosputtering. The samples were prepared with a variety of Si volume concentrations and annealing temperatures. The results are discussed by correlating them with the preparation conditions, the nanostructure, and comparing them with the results obtained for porous silicon. The conductivity, photoconductivity and minority carriers diffusion length were also obtained for samples with different Si content and average size of the nanostructure. The study gives information about the percolation threshold and the electrical transport mechanisms in the composite. Eu- and Er-doped samples were finally prepared and studied for their PL response. A clear correlation between the enhancement of theEr+3infrared emission and the presence of the silicon nanostructure is shown. In the case of Eu-doped samples, emissions fromEu+3orEu+2are observed depending on the characteristics of the host (when exciting with 514.5 nm laser radiation). Degenerate four-wave mixing signals suggest a strong interaction between the free carriers of the silicon nanostructure and the Eu ions that can promote the emission fromEu+2under illumination.