Élaboration et caractérisation de couches minces à base d’oxydes.

Abstract

In this work, we are interested in the study of thin films based on metal oxides elaborated by two chemical methods namely the pyrolysis spray and the sol-gel dip - coating. Our study is first focused on the effect of solvent on the properties of thin CuO films. Thin CuO films were prepared by the pyrolysis spray method using two different solvents: water and methanol. The structural, microstructural, morphological and optical characterizations of CuO thin films were carried out. The crystalline structure analysis using the XRD diffraction technique shows three characteristic peaks (002), (111) and (020) of the monoclinic CuO phase. The position of the peaks are shifted to the lowest angles, indicating the effect of tensile stress in the prepared films. The micro-Raman analysis confirms the results of XRD. The SEM observation shows that the morphology of the film strongly depends on the nature of the used solvent. The optical characterization of CuO- (distilled water) sample shows a low transmittance compared to that prepared with methanol. This behavior is attributed to the simultaneous effects of thickness and solvent. Then, our study has been focused on the effect of experimental parameters and the addition of metal oxides (ZnO and NiO) on the properties of TiO2 thin films prepared by the sol-gel method. The structural characterization by means of micro-Raman spectroscopy shows vibration modes corresponding to the anatase phase of TiO2. Thin TiO2films and its compounds are characterized by micro-Raman, SEM, m-lines and Uvvisible techniques. Micro-Raman analysis shows that the TiO2 thin films are characterized by the modes of vibration of the Anatase phase. ZnO and NiO cause the decay of TiO2 vibration modes. The SEM observation shows that the addition of ZnO pushes the crystalline degradation (amorphization) of the TiO2 anatase phase. While UV.Vis analysis shows an increase in the optical gap due to the effect of amorphization and Burstein-Moss. The waveguide measurements reveal simple guided modes in both polarizations (TE0 and TM0) in all samples from which the refractive index and the thickness are calculated. A decreasing refractive index profile was observed when ZnO and NiO are introduced into thin films of pure TiO2. The photocatalytic activity is evaluated by the degradation of MB. The obtained results show that the thin films of pure TiO2 are the best photocatalytic materials.