PREPARATION AND CHARACTERIZATION OF HGXCD1-XS AND PBXCD1-XS QUANTUM DOTS AND DOPED THIN-FILMS

Thin silica and silica-titania films doped with sulfide nanocrystals o f controlled size were fabricated by a method based on the preparation of colloidal particles and their introduction into a glassy matrix th rough the sol-gel method. Colloidal sols of composition HgxCd1-xS and PbxCd1-xS (with x ranging from 0 to 1) were prepared and used to dope alkoxide solutions for the deposition of thin silica and silica-titani a films. Optical absorption spectra were taken on both precursor collo idal sols and derived doped films. X-ray diffraction characterization gave structural information on the nature and size of particles in pow ders obtained by precipitation from colloidal sol and in doped films. The advantages and limits of the investigated systems are discussed in light of possible applications. The nonlinear properties of the most interesting PbS-doped planar waveguides have been investigated in the near-infrared, at 1.064 mu m. A reversible nonlinear effect was measur ed, with n(2) values ranging from -5 to -20 x 10(-9) cm2/kW.