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TiO2 Thin Films (tio2 + thin_film)
Selected AbstractsMononuclear Mixed ,-Ketoester-alkoxide Compound of Titanium as a Promising Precursor for Low-Temperature MOCVD of TiO2 Thin Films,CHEMICAL VAPOR DEPOSITION, Issue 6 2003R. Bhakta A monomeric titanium complex suitable for liquid-injection MOCVD applications is synthesized and its molecular structure is determined by single-crystal X-ray diffraction. [Ti(OiPr)2 -(tbaoac)2] (see Figure), (tbaoac),=,tertiarybutylacetoacetonate), is a volatile alkoxide-(beta)diketonate precursor that has a low melting point and very good solubility in common organic solvents. [source] Effect of annealing on the structural, electrical and optical properties of nanostructured TiO2 thin filmsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 9 2009S. Sankar Abstract Nanostructured titanium dioxide thin films were prepared using reactive pulsed laser ablation technique. Effects of annealing on the structural, morphological, electrical and optical properties are discussed. The structural, electrical and optical properties of TiO2 films are found to be sensitive to annealing temperature and are described with GIXRD, SEM, AFM, UV-Visible spectroscopy and electrical studies. X-ray diffraction studies showed that the as-deposited films were amorphous and at first changed to anatase and then to rutile phase with increase of annealing temperature. Optical constants of these films were derived from the transmission spectra and the refractive index dispersion of the films, subjected to annealing at different temperatures, is discussed in terms of the single oscillator-Wemple and Didomenico model. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Electronic Manifestation of Cation-Vacancy-Induced Magnetic Moments in a Transparent Oxide Semiconductor: Anatase Nb:TiO2ADVANCED MATERIALS, Issue 22 2009Shixiong Zhang Nb-doped anatase TiO2 thin films grown by pulsed-laser deposition show Kondo scattering in elctronic-transport measurements, providing evidence for the formation of magnetic moments. The origin of magnetism is attributed to cation (Ti) vacancies, confirmed by X-ray absorption spectroscopy and first-principle calculations. The Ti vacancies are controlled by oxygen partial pressure during growth. [source] Application of ion beam techniques for preparation of metal ion-implanted TiO2 thin film photocatalyst available under visible light irradiation: metal ion-implantation and ionized cluster beam methodJOURNAL OF SYNCHROTRON RADIATION, Issue 2 2001Hiromi Yamashita Transparent TiO2 thin film photocatalysts have been prepared on silica glass plate by an ionized cluster beam (ICB) method. In order to improve the electronic properties of these photocatalysts, transition metal ions V+, Cr+, Mn+, Fe+) were implanted into the TiO2 thin films at high energy acceleration using an advanced metal ion-implantation technique. The combination of these ion beam techniques can allow us to prepare the TiO2 thin film photocatalysts which can work effectively under visible light (, > 450 nm) and/or solar light irradiation. The investigation using XAFS and ab initio molecular calculation suggests that the substitution of octahedrally coordinated Ti ions in TiO2 lattice with implanted metal ions is important to modify TiO2 to be able to adsorb visible light and operate under visible light irradiation. [source] Effect of the substrate temperature on the properties of the RF sputtered TiO2 thin filmsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 9 2010I. Ben Mbarek Abstract Titanium dioxide (TiO2) thin films were deposited by RF magnetron sputtering on glass and silicon substrates at different substrate temperatures (20, 100, 200 and 300 °C). The structural and morphological characteristics of the films were investigated by X ray Diffractometry (XRD) and Atomic Force Microscopy (AFM) while the optical properties of the films were studied by optical spectroscopy. It was shown that at room temperature, TiO2 films grown on glass were amorphous following the substrate structure. At higher temperatures, XRD detected only a nanocrystalline rutile TiO2 structure. This indicated that the transition temperature toward the most stable TiO2 phase was obtained from 100 °C and the crystallinity was enhanced at higher growth temperature. For TiO2 films grown on Si substrates, only a nanocrystalline anatase TiO2 structure was obtained at room temperature. At higher temperatures, we noticed the appearance of other secondary phases related to rutile, anatase and brookite structures. From AFM images, we noticed that at room temperature, the films were porous. With increasing the temperature, the structure of the films became crystallized showing a columnar structure. Film growth and structural properties were discussed in terms of the Thornton model. From optical analysis, the films were transparent with an indirect band gap and a refraction index which reached 3.09 eV and 2.7, respectively. The reflectance and transmittance spectra showed, not only that there was a little translation from UVB to UVA and near-visible range, but also a decrease of reflection with a temperature increase indicating that the films could be used as anti-reflection coatings. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Titanium dioxide thin films deposited by the sol-gel technique starting from titanium oxy-acetyl acetonate: gas sensing and photocatalyst applicationsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 9 2010A. Maldonado Abstract Titanium dioxide (TiO2) thin films were deposited onto sodocalcic glass plates by the sol-gel technique, starting from a non-alkoxide route, namely, titanium oxy-acetyl acetonate as Ti precursor. Film thickness effect on both the gas sensing and photocatalytic degradation performance was studied. The as-deposited films were annealed in air at 400 °C. All the X-ray spectra of the films show a very broad-peak centered in a 2, angle around 30°. In the case of the thinnest films the surface morphology is uniform and very smooth, whereas for the thickest films the corresponding surface is covered by grains with a rod-like shape with a length on the order of 140 nm. The films were tested both for two straightforward applications: ultraviolet assisted-degradation of methylene blue dissolved in water, at different times, as well as gas sensor in a controlled propane (C3H8) atmosphere. As the film thickness increases, the degradation of methylene blue (MB) also increases. The thickest TiO2 thin films after being exposed by 5 hours to the catalytic degradation, promoted by ultraviolet illumination, showed a final MB solution degradation in the order of 48%. This reult can be associated with the increase in the effective exposed area of the TiO2 thin films. On the other hand, the exposition of the films to a controlled propane atmosphere produced a significant change in the surface electrical resistance of the films at operating temperatures of 200 °C and above. In fact, in the case of the thickest TiO2 films, a dramatic electrical resistance change of non-exposed and propane exposed , 560 to 0.7 M, ,, was registered. The results show that TiO2 films deposited by an economical deposition technique, as is the case of the sol-gel technique, could have an important potential in industrial applications. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Optical properties of TiO2 thin films prepared by chemical spray pyrolysis from aqueous solutionsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3-4 2010R. Ayouchi Abstract Titanium dioxide (TiO2) is known to have three different kinds of polymorphous crystalline forms: rutile, anatase, and brookite. The rutile phase is always formed at higher temperatures, while the anatase phase is formed at lower temperatures and transformed into rutile phase above 800 ºC. Various deposition techniques have been developed for depositing TiO2 thin films, including evaporation, sputtering, chemical vapour deposition and thermal oxidation of titanium. Among them, the Chemical Spray Pyrolysis (CSP) technique has many advantages, such as good conformal coverage, the possibility of epitaxial growth and the application to large area deposition. Also, this method is low cost and it is easy to control the deposition growth parameters. In the present work, TiO2 thin films have been deposited on p-Si (001) and fused silica substrates by Chemical Spray Pyrolysis (CSP) method from aqueous solution containing titanium (IV) isopropoxide (Ti[OCH(CH3)2]4. As-deposited thin films show anatase polycrystalline structure, and rutile phase formed for films annealed at 750ºC. SEM images have confirmed a smooth and crack-free surface with low surface roughness. X-ray photoelectron spectroscopy (XPS) combined with 4 keV Ar+ depth profiling has shown that crystallized films correspond to TiO2. Residual carbon coming from the organic precursor solution is only detected at the surface of the film. Thin films deposited on fused silica were highly transparent (more than 85%), with an indirect optical band gap of 3,43 and 3,33 eV for as-deposited and annealed films, respectively, and refractive indexes in the range between 2.01,2.29. Spectroscopic Ellipsometry (SE) also has been used to extract optical parameters. SE data fitted to triple-layer physical model revealed the same tendency to increase refractive index in annealed films. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Structural and spectroscopic study of the Fe doped TiO2 thin films for applications in photocatalysisPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue S1 2009N. R. Mathews Abstract In this work we are presenting the results of structural and optical investigations of TiO2 and Fe doped TiO2 films using XRD, XPS, UV-VIS transmittance spectroscopy, and the application of these films in photocatalysis is demonstrated. Fe-doped TiO2 films were prepared by sol-gel method. The concentration of Fe utilized for doping ranged from 0.5 to 4% by atomic weight. For lower concentrations of Fe the transformation from amorphous-to-polycrystalline occurred at 400 °C. However, as the Fe concentration was increased to 4% this transformation occurred only after annealing at 600 °C. The average grain size for 4% Fe doped sample was in the range of 13 nm. In the case of pure TiO2 the XPS analysis showed only the presence of Ti 4+, where the 4% Fe doped film showed the presence of two species of Ti atoms; one of unperturbed Ti atoms and another of negatively charged surface of Ti atoms due to the interaction with Fe atoms in the anatase lattice of TiO2. The optical band gap was found to decrease with Fe concentration. The resistivity was found to decrease by one order after doping. The 4% Fe doped TiO2 films showed an increased photocatalytic activity. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Effects of using multi-component electrolytes on the stability and properties of solar cells sensitized with simple organic dyesPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 2 2010M. Giannouli Abstract In this paper we present experimental results for electrochemical (dye-sensitized) solar cells that were prepared in our laboratory in order to examine some of the major factors affecting the efficiency and the stability of such cells. Nanostructured TiO2 thin films were prepared and sensitized using an organic dye. For the purpose of this study three different types of electrolytes were developed: a standard-type electrolyte containing potassium iodide and iodine in propylene carbonate (PC) and two novel, multi-component electrolytes containing potassium iodide and iodine dissolved in varying mixtures of PC and EG (ethylene glycol). It was demonstrated that the combined properties of the two solvents in the multi-component electrolytes enhance the efficiency and improve considerably the stability of the cells. Copyright © 2010 John Wiley & Sons, Ltd. [source] TiO2 DLAR coatings for planar silicon solar cellsPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 1 2003B. S. Richards Abstract In this paper we demonstrate that a double-layer anti-reflection (DLAR) coating can be fabricated using only titanium dioxide (TiO2). Two TiO2 thin films were deposited onto planar silicon wafers using a simple atmospheric pressure chemical vapour deposition (APCVD) system under different deposition conditions. Weighted average reflectances of 6.5% (measured) and 7.0% (calculated) were achieved for TiO2 DLAR coatings in air and under glass, respectively. An increase in the short-circuit current density of , Jsc,=,2.5,mA/cm2 can be expected for an optimised TiO2 DLAR coating when compared with a commercial TiO2 single-layer anti-reflection coating. Copyright © 2003 John Wiley & Sons, Ltd. [source] | |||||||||||||