Etude des propriétés structurales et optiques de nano-cristaux semi-conducteurs à grand gap synthétisés par voie sol-gel modifiée

Abstract

This thesis concerns the development and characterization of thin films of ZnO and TiO2, which were conducted at temperatures close to room temperature using the sol-gel method with a deposition technique ""Dip Coating."" The Both samples were prepared by two different solutions: the first is to add the precursor of zinc acetate dihydrate and the solvent 2-methoxyethanol with monoethanolamine as a stabilizer, while the second is to dissolve the titaniaume IV propoxide in ethanol (solvent) with the addition of HCl as catalyst. Structural characterization of thin films of ZnO and TiO2 was carried out by X-ray diffraction. It confirmed first, the formation of crystallites for both samples irradiated by UV light for 84 hours and 155 hours in the case of ZnO and TiO2, respectively, and secondly to determine their crystal structures and their small size does not exceed a few of nanometers. Characterization by measurement of optical absorption in the UV – visible domain, showed a shift of absorption edge for ZnO and TiO2 layers to high energies (short wavelengths) compared to that of bulk crystal of the latter two. This discrepancy is due to quantum confinement effect induced by size reduction. A second optical characterization by photoluminescence measurement showed that the samples prepared exhibit intense emission bands in the visible and near UV. This observation led us to practical applications in area of optic and photovoltaic.