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Abstract: Multilayered TiO2(Fe3+, PEG) films were deposited on glass and SiO2/glass substrates by sol–gel dipping method. The influence of Fe3+ and PEG(polyethylene glycol) concentrations, the number of layers, the thermal treatment time and the temperature on the optical and microstructural properties of the TiO2 films were studied. As-deposited TiO2(Fe3+, PEG) films were very porous, but after the thermal treatment at 500°C, the PEG decomposed and burned out to porosity decreasing. Homogeneous nanostructured films were obtained, where the amorphous and the anatase phases coexist. XRD analysis showed that no rutile phase is observed in the films deposited on SiO2/glass as compared with those deposited directly on glass and that the presence of the anatase phase in the films without PEG is more evident in the three-layers film. The XRD intensity of the main peak of anatase from 25° decreases with the increase of PEG concentration. The optical gap of the TiO2(Fe3+, PEG) films is found in 2.52–2.56eV range and does not essentially depend on the PEG content. [Copyright &y& Elsevier]

Tin-doped indium oxide (ITO) thin films have been deposited by sol–gel process using ‘sols’ of indium and tin isopropoxides. The thickness of one deposited ITO layer is approximately 50 nm. The desired thickness was obtained by 1–5 successive depositions. The XTEM cross-sectional view of an ITO sample with five depositions showed a clear delimitation of the layers with an alternating structure dense/porous ITO layers. The void fraction in porous regions varies between 20 and 25%. Cubic bixbyite In2O3 nanocrystals with size of 10–20 nm and no phases separation of tin oxide were observed. The optical properties of the films have been investigated by optical transmission and spectroscopic ellipsometry. Reliable optical constants and porosity are obtained only with the model of internal structure based on XTEM results. [Copyright &y& Elsevier]

TiO2 based nanustructured coatings have been prepared by sol–gel method on glass and SiO2/glass substrates. The films were thermally treated in oxidative and reductive conditions at 500 °C. The influence of the substrate and of the thermal treatment on the optical properties of the films was studied. The samples were characterized by spectroscopic ellipsometry (SE), scanning electron microscopy (SEM), Rutherford backscattering spectroscopy (RBS) and Raman spectroscopy. SE results supported by other optical and structural measurements have proven the transformation of CuO from as-prepared samples into Cu2O in samples heated in oxidative conditions and into metallic Cu in samples heated in reductive conditions as well as the transformation of the amorphous TiO2 in anatase. [Copyright &y& Elsevier]

The gels which are precursors of TiO2 porous materials are prepared by the controlled hydrolysis-condensation of titanium isopropoxide by polymeric method. In the present work, a study of the influence of different experimental conditions (water/alkoxide ratio, solvent/alkoxide ratio and temperature) on the structure and texture of the polymeric gels obtained with the same type of alkoxide has been investigated. The structural and textural modifications for the unsupported materials have been detected using DTA/TGA, XRD, specific surface area and pore size computerized measurements. The optical properties of the supported materials deposited on silicon wafers have been investigated using ellipsometric method. Supported and unsupported porous materials with different structure and texture have been obtained depending on different experimental and thermal treatment conditions. [ABSTRACT FROM AUTHOR]

Titania films doped with low amount of vanadium were deposited on different substrates (microscope glass, microscope glass covered with SiO 2 barrier layer, and silicon wafer with a thermally grown layer of SiO 2 ) by dip coating from solutions prepared by sol-gel and microwave (MW) assisted sol-gel syntheses. The selected molar composition was 99.95:0.05 which corresponds to 0.03 at% of V. The films were characterized by Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), X-ray diffraction (XRD) and Spectroscopic Ellipsometry (SE). The deposited films thermally treated at 450 °C, presented homogeneous and continuous nanostructured surfaces and good adherence to the substrates used. All samples crystallized in anatase phase and have good optical properties. The highest transmission value was obtained for the V-doped TiO 2 films (T > 90%) deposited from solutions prepared by microwaves assisted sol-gel method. Based on the obtained results it was concluded that the method of preparation has higher influence on the properties of the resulted films than the substrates used. [ABSTRACT FROM AUTHOR]

Nb doped titania (TiO 2 :Nb) multilayered films (1–10 layers) with anatase structure were obtained by the low-cost sol–gel and dipping method on microscope glass substrates, followed by thermal treatment at 450 °C for 1 h. After each layer deposition, an intermediate annealing step was performed at 300 °C for 30 min. Doping TiO 2 sol–gel films with a low amount of Nb (0.8 at%) allows obtaining an improved CO sensor able to operate under environmental atmosphere (air). It was found that the sensor sensitivity is less dependent on the film thickness but is significantly influenced by Nb doping at the optimal working temperature of 400 °C. Good recovery characteristics were obtained for a wide CO detection range, between 0 and 2000 ppm. The gas-sensing behavior of the films was correlated with the structural, chemical and morphological properties of the multi-layered structures. [ABSTRACT FROM AUTHOR]

By codoping with a donor–acceptor pair through a two-step chemical method we have succeed to obtain p-type ZnO thin films on glass. Firstly, a thin undoped ZnO seed layer was deposited by sol–gel method followed by the deposition of In–N codoped ZnO film obtained through the hydrothermal technique. The influence of post-deposition annealing temperature (100 °C, 300 °C and 500 °C) on the samples was investigated from a structural, chemical, morphological and optoelectrical point of view. X-ray diffractometry (XRD), infrared ellipsometry and X-ray photoelectron spectroscopy (XPS) analyses have confirmed the codoped nature of the ZnO thin films. The XRD pattern analysis has established the films have wurtzite nanocrystalline structure, the crystallite sizes varying between 10 nm and 13 nm with the annealing temperature. Continuous and homogenous films with nanorods surface morphology has been obtained, as visualized by scanning electron microscopy measurements. Hall Effect measurements have established that all samples, regardless of annealing temperature, showed p-type conduction due to the successful incorporation of nitrogen in the film, with the highest carrier concentration registered at 500 °C. This is in good correlation with the nitrogen content in the films as revealed from XPS. In all samples, the XPS depth profiling has shown a nitrogen gradient with higher elemental concentration at the surface. [ABSTRACT FROM AUTHOR]

The transparent conductive oxide films with controlled type of conduction are of great importance and their preparation is intensively studied. In our work, the preparation of such films based on doped ZnO was realized in order to achieve controlled type of conduction and high concentration of the charge carriers. Sol–gel method was used for films preparation and several dopants were tested (Sn, Li, Ni). Multilayer deposition was performed on several substrates: SiO 2 /Si wafers, silica-soda-lime and/or silica glasses. The structural and morphological characterization of the obtained films were done by scanning electron microscopy, X-ray diffraction, X-ray fluorescence, X-ray photoelectron spectroscopy and atomic force microscopy respectively, while spectroscopic ellipsometry and transmittance measurements were done for determination of optical properties. The selected samples with the best structural, morphological and optical properties were subjected to electrical measurement (Hall and Seebeck effect). In all studied cases, samples with good adherence and homogeneous morphology as well as monophasic wurtzite type structure were obtained. The optical constants (refractive index and extinction coefficient) were calculated from spectroscopic ellipsometry data using Cauchy model. Films with n- or p-type conduction were obtained depending on the composition, number of deposition and thermal treatment temperature. [ABSTRACT FROM AUTHOR]

Abstract: Multilayered titania (TiO2) films have been prepared via sol–gel dip-coating method from a tetraethyl-orthotitanate solution that contains 2g of polyethylene glycol (PEG) with different molecular weight (6000, 20,000 and 35,000). The films were deposited on fluorine doped tin oxide (FTO) coated glass and annealed by a thermal treatment at 450°C for 30min. We demonstrated how the structure, the morphology and the optical properties of the films can be controlled by varying the PEG molecular weight and number of depositions. The correlation between these parameters and the film properties was investigated. Sol–gel deposited and PEG doped TiO2 films demonstrate better properties for their use in solar cell applications, by enhancing the transmittance value in the 380–540nm range. [Copyright &y& Elsevier]

Abstract: Multilayered TiO2 films were obtained by sol–gel and dipping deposition on quartz substrate followed by thermal treatment under NH3 atmosphere. In an attempt to understand the close relationship between microstructural characteristics and the synthesis parameters, a systematic research of the structure and the morphology of NH3 modified TiO2 sol–gel films by XRD and Atomic Force Microscopy is reported. The surface morphology has been evaluated in terms of grains size, fractal dimension and surface roughness. For each surface, it was found a self-similar behavior (with mean fractal dimension in the range of 2.67–3.00) related to an optimum morphology favorable to maintain a nano-size distribution of the grains. The root mean square (RMS) roughness of the samples was found to be in the range of 0.72–6.02 nm. [Copyright &y& Elsevier]

TiO2-based nanostructured Fe3+-doped coatings have been prepared by the sol–gel method on glass substrates. The coatings were characterized by X-ray diffraction and spectroellipsometry methods. The influence of Fe3+ dopant concentration, number of coatings, and calcination temperature on the films structure was established. The antibacterial activity against E. coli, has been studied applying the so-called antibacterial-drop test. The bactericidal activity for the above bacteria cells was estimated by relative number of bacteria survived calculated from the number of viable cells which form colonies on the nutrient agar plates. The coatings exhibited a high antibacterial activity, which was enhanced with the increase of the temperature of thermal treatment and formation of anatase crystalline structure. The long thermal treatment results in rutile crystalline structure formation followed by the decrease in the antibacterial activity of the coating. [Copyright &y& Elsevier]