Síntese, caracterização e estudo de nanocristais semicondutores de Bi2Te3 dopados com íons magnéticos de cromo em matrizes vítreas

Abstract

In this dissertation work, bismuth telluride (Bi2Te3) nanocrystals doped with different concentrations of chromium (Cr) were grown in the matrix with nominal composition 40SiO2.30Na2CO3.1Al2O3.29B2O3 (mol%) by the fusion method. To confirm the formation of these nanocrystals, experimental measurements of Transmission Electron Microscopy (MET), X-Ray Diffraction (DR-X), UV-VIS Spectroscopy and Electronic Paramagnetic Resonance (RPE) were performed. Transmission Electron Microscopy images confirmed the formation of Bi2-xCrxTe3 nanocrystals with estimated grid parameter d = 0.322 nm, attributed to the crystalline plane (015). X-ray diffractograms showed the displacement of the diffraction peaks of the crystalline plane (015) of Bi2-xCrxTe3 nanocrystals to greater angles with increasing Cr3+ ions concentration. UV-VIS spectra showed the shift of optical absorption bands for different heat treatment times at 500 oC and the presence of the bands at 440, 630, 660 and 685 nm attributed to 500oC ions. Studies using the Tanabe-Sugane diagram for optical absorption spectra have provided evidence of incorporation of 500oC ions into octahedral sites of the Bi2Te3 semiconductor crystal structure. Electronic Paramagnetic Resonance Spectra, corresponding to + ½↔- ½, electronic transition, showed the thin line of Cr3+ ions when incorporated into Bi2Te3 nanocrystals.