Contribution à l'élaboration de l'oxyde de titane par le procédé sol-gel

Abstract

The present work consists in the elaboration and the characterization of TiO2 thin films by sol-gel method. Particular attention is paid to the influence of temperatures, the annealing atmosphere, the thickness, the nature of the substrates and doping with Fe element on the different structural, morphological, optical, dielectric and chemical properties. The different samples are characterized by the X-ray diffraction (XRD), atomic force microscopy (AFM), Raman spectroscopy, FTIR spectroscopy, spectroscopic ellipsometry, UV-Visible spectroscopy, m-lines spectroscopy and hydrophilic measurements. The structural study shows that the crystallization of the films occurs for critical thicknesses. The thermal annealing under various atmospheres (air and oxygen) and the presence of buffer layers between the TiO2 film and the substrate are important factors affecting the formation and improving the structure of anatase and rutile phases. The phase transformation anatase-rutile occurs at high temperature (800°C). The SnO2 interfacial layer and the high doping level (7% at.) have the effect of decreasing the temperature of this transformation. The morphological study shows, in general, a uniform growth with relatively low roughness, which bodes the optical quality of the films obtained. The optical study shows that the values of the refractive indices derived using the sem-infinite, Fourouhi-Bloomer and EMA models are in good agreement with those of the literature. The study of the optical gap obtained by spectroscopic ellipsometry and the UV-visible spectroscopy reveals some variation depending on various parameters. The waveguiding measurements show that TiO2 films deposited directly on the glass behave as single-mode waveguides in the two polarizations (TM and TE). When SnO2 and ZnO films are used as buffer layers, we note the disappearance of TM modes. The dielectric study shows that the approach based on the Kramers-Kronig analysis and Maxwell's equations is proved acceptable in comparison with other known models. The analysis of wetting water shows the super-hydrophilicity of TiO2/verre and TiO2/(ZnO/glass) samples.