Sínteses, caracterizações e estudo de pontos quânticos de calcogenetos de cádmio

AUTOR(ES)

Ernesto Soares de Freitas Neto

DATA DE PUBLICAÇÃO

2009

RESUMO

CdS, CdSe, CdSxSe1-x and Cd1-xMnxS quantum dots were successfully grown in the glass matrix SNAB [40SiO2.30Na2CO3.1Al2O3.29B2O3 (mol%)] synthesized by the Fusion Method, when subjected to certain thermal treatment. The glass transition temperature (Tg) of the glass matrix SNAB was found by Differential Scanning Calorimetry (DSC) in order to set the temperature of 560C to be used in thermal treatment, which favored the formation of CdS, CdSe, CdSxSe1-x and Cd1- xMnxS quantum dots. We investigated the optical properties, by Optical Absorption (OA), Photoluminescence (PL) and Raman Scattering, the morphological, by Atomic Force Microscopy (AFM) and the magnetic, by Electron Paramagnetic Resonance (EPR) of the synthesized quantum dots. From the spectra of OA we have determined the dispersion of the size of nanocrystals and, using a theoretical model based on the effective mass approximation, it was possible to estimate the average radius of quantum dots around 2.0 nm. The Raman spectra demonstrated, finally, the formation of CdS, CdSe and CdSxSe1-x quantum dots, and the effect of the lattice contraction of nanocrystals caused by interactions with the host glass matrix. The EPR spectra confirmed the incorporation of Mn2+ ions in CdS nanocrystals, forming Cd1-xMnxS in two different sites: one of them embedded in the core and the other near the surface of nanocrystals. We have concluded from the obtained results, that CdS, CdSe, CdSxSe1-x and Cd1-xMnxS quantum dots grown in a glass system have a great possibility of application in technological devices, such as active elements for lasers, optical amplifiers, LEDs (Light-Emitting Diodes), among others.

ASSUNTO(S)

cdse cd1-xmnxs fotoluminescência microscopia de força atômica quantum dots photoluminescence electronic paramagnetic resonance pontos quânticos cdsxse1-x espalhamento raman fisica raman scattering cds absorção óptica ressonância paramagnética eletrônica optical absorption atomic force microscopy

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