Etude de l’influence de terre rare (Er3+) sur les propriétés structurales, optiques et magnétiques des couches minces et xérogels de TiO2.

Abstract

The thin films and xerogels of titanium oxide (TiO2), undoped and doped with erbium (Er3+) have been synthesized by the sol-gel process. The xerogels have been characterized by DSC and Raman. The results show that: the maximum crystallization is at 339 °C of undoped TiO2, whereas for the one doped with 0.1 at.% Erbium, the first maximum is observed at 301°C. And finally for the other cases (0.5, 1 and 3 at.% erbium) the crystallization starts from 351°C with a double exothermic.The XRD and Raman characterization of the TiO2 thin films shows that the samples obtained crystallize only in the quadric anatase system in the chosen temperature range. According to the latter, we observe that the grain size varies gradually with the increase of erbium. The study of the morphology by the SEM and the AFM confirms that the films, thus elaborated are homogeneous, without cracking, of nanometric structure and having a very low roughness (~1 nm). The UV-Vis spectra of the obtained thin films show that the reflection has a significant influence on the refractive index, the density and the porosity. Thereby, photoluminescence spectra (PL) reveal the characteristic bands of erbium emission between 520-570 nm and 640-680 nm, and the intensity of the PL spectrum increases with the erbium ratio. From the results of the m-lines spectroscopy, we notice that the thin layers have two guided modes: TE0 and TE1. Further, the results of the vibratory sample magnetometer (VSM) of the undoped TiO2 thin films indicate a ferromagnetic behavior at room temperature and doping with erbium (Er3+) leads to an elevation of the magnetic saturation moment (Ms). Finally, the photocatalytic tests illustrate a good efficiency in the degradation of MO. The thin films of Er3+:TiO2 have good structural properties, photoluminescence characteristics, very good guiding behavior and diluted magnetic semiconductor structure. Accordingly, our thin films are promising for possible applications in optoelectronic devices.