Characterization of TiO2 films obtained by a wet chemical process

TiO₂ has an easily tunable bandgap and a great absorption dye ability being widely used in many fields and in a number of fascinating applications. In this study, a wet chemical route, particularly a sol gel method using spin-coating is adopted to deposit TiO₂ thin films onto soda lime glass and silicon substrates. TiO₂ films were prepared by using an alcoholic solution of analytical reagent grade TiCl₄ as titanium precursor at various experimental conditions. The accent was put on the conditions of preparation (spin time, spin speed, precursor concentration, number of coating layers etc), doping and on the post-deposit treatment namely the drying and the crystallization. The results showed a strong dependence on the drying temperature and on the temperature and duration of the crystallization. We found that the solution preparation and its color are important for getting a reproducible final product. The Raman spectra recorded at room temperature, showed the characteristic peaks of anatase which appear at 143 and around 396 cm⁻¹. These peaks confirm the presence of TiO₂.

The X-ray diffraction (XRD) was used to identify the crystalline characteristic of TiO₂ while the chemical states and relative amounts of the main elements existing in the samples were investigated by X-ray Photoelectron Spectroscopy (XPS). The morphology of the samples was visualized by AFM. We show by this work the feasibility to obtain different nanostructured TiO₂ by changing the concentration of the solution. Photocatalytic activity of TiO₂ films was evaluated. Rhodamine B is a recalcitrant dye and TiO₂ was successfully tested for its oxidation. An abatement of 60% was obtained under sunlight for an initial concentration of 10 mg/l.