Síntese in-situ de nanocristais de calcogenetos (Te>sup<0>/sup<, CdS) em vidros teluritos e fosfatos para aplicações em fotônica

Abstract

The work presents the study of the reduction of Te 4+ to Te 0 in tellurite glasses doped with PbS and PbO/ZnS and seeks to induce, in a controlled manner, this redox process through the microfabrication technique using a pulsed laser on a femtosecond scale, with the goal of produce a planar waveguide. The study of tellurium reduction in the vitreous matrix becomes very important and promising, since the controlled reduction of tellurium can generate changes in the refractive index (waveguides) and/or darkening of the sample (data storage and photosensitive materials). The tellurite glass samples were synthesized by varying the matrix composition and the dopants concentration and their thermal and structural properties were determined through various characterization techniques, such as differential scanning calorimetry (DSC), X-ray diffraction (XRD), Raman scattering spectroscopy, transmission electron microscopy (TEM), selected area electronic diffraction (SAED) and X-ray photoelectron spectroscopy (XPS). The tellurite glasses doped with sulfides showed, in most samples, brown or black color (darkening effect). After analysis by Raman spectroscopy and SAED, the presence of Te 0 in the samples was found, indicating that the S 2ions cause the Te 4+ reduction in the vitreous matrix, causing the darkening effect. The femtosecond laser microfabrication technique was used in transparent samples to achieve a localized reduction of Te 4+ in the volume of the glass. The work also investigates the formation of quantum dots (QDs) of CdS in phosphate-based oxyfluoride glasses and their respective photoluminescent properties. Absorption, emission, and excitation spectra were obtained, and the results indicate the formation of QDs in the matrix. However, it was not possible, with the methods employed in this work, to control the formation and growth of CdS QDs.