Growth mechanism of two-component titania/vanadium oxide thin films from aqueous solutions
Mechanical Properties of Metallic Materials and their Microstructural Origins
Final Report Abstract
This project was dedicated to the incorporation of vanadium into titania (TiO 2) films. The films were deposited from aqueous salt solutions. A further main aim was the structural characterization of the films. Moreover, the optical and electrochromic properties were considered. The deposition mechanisms were investigated and it was demonstrated, that the vanadium content within the films can be enhanced with the corresponding concentration in the deposition solutions. Detailed structural studies by atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) were applied to characterise the structural features of the as-deposited films as well as of the ones after heat treatment up to temperatures of 550 °C. Depending on the film composition the presence of Ti1-xVxO2 solid solutions, V2O5, TiO2 as well as of V-doped TiO2 was detected. The detailed investigation of the as-received titania-based films by UV/Vis spectroscopy demonstrated, that their optical bandgap is located in the UV range and can be decreased from 3.8 to 3.2 eV by increasing the amount of incorporated vanadium. Additionally, the bandgap can be shifted into the visible range to 2.6 eV by further annealing treatment. Based on these results opportunities for bandgap engineering were provided. Therefore, the photocatalytic behaviour of the films was investigated. In this connection, contact angle measurements were carried out. It was demonstrated, that increasing amounts of vanadium within the films are connected with a decrease of the contact angle, which finally results in a superhydrophilic behaviour and qualifies the materials for the set-up of self-cleaning or antifogging surfaces. Beside photocatalysis also the ability of the films with regard to their ability for the intercalation of lithium ions was studied. It was shown, that the intercalation induces electrochromic behavior of the films, which makes them candidates for the production of smart windows.
Publications
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Synthesis of V-doped TiO2 films by chemical bath deposition and the effect of post-annealing on their properties. Thin Solid Films (2012)
Denitsa Shopova-Gospodinova, Lars P.H. Jeurgens, Udo Welzel, Luciana Pitta Bauermann, Rudolf C. Hoffmann, Joachim Bill
