Synthesis and characterization of boron-oxygen-hydrogen thin films at low temperatures

We have studied the influence of synthesis temperature on chemical composition and mechanical properties of X-ray amorphous boron-oxygen-hydrogen (B-O-H) films. These B-O-H films have been synthesized by RF sputtering of a B-target in an Ar atmosphere. Upon increasing the synthesis temperature from room temperature to 550 °C, the O/B and H/B ratios decrease from 0.73 to 0.15 and 0.28 to 0.07, respectively, as determined by elastic recoil detection analysis. It is reasonable to assume that potential sources of O and H are residual gas and laboratory atmosphere. The elastic modulus, as measured by nanoindentation, increases from 93 to 214 GPa, as the O/B and H/B ratios decreases within the range probed. Hence, we have shown that the effect of impurity incorporation on the elastic properties is extensive and that the magnitude of the incorporation is a strong function of the substrate temperature.     

Fabrication and characterization of nano TiO2 thin films at low temperature

Anatase TiO₂ thin films were successfully prepared on glass slide substrates via a sol–gel method from refluxed sol (RS) containing anatase TiO₂ crystals at low temperature of 100 °C. The influences of various refluxing time on crystallinity, morphology and size of the RS sol and dried TiO₂ films particles were discussed. These samples were characterized by infrared absorption spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission-scanning electron microscopy (FE-SEM) and UV–vis absorption spectroscopy (UV–vis). The photocatalytic activities of the TiO₂ thin films were assessed by the degradation of methyl orange in aqueous solution. The results indicated that titania films thus obtained were transparent and their maximal light transmittance exceeded 80% under visible light region. The TiO₂ thin films prepared from RS-6 sol showed the highest photocatalytic activity, when the calcination temperature is higher than 300 °C. The degradation of methyl orange of RS-6 thin films reached 99% after irradiated for 120 min, the results suggested that the TiO₂ thin films prepared from RS sol exhibited high photoactivities.     

Electrical transport properties of thin cadmium films at low temperatures

We report here the results of an extensive study of localization and electron-electron interaction effects in thin cadmium films with thickness ranging from 80 Å to 350 Å. Measurements of the resistance as a function of both temperature and magnetic field have allowed us to separate the contributions of localization and electron-electron interaction. The low resistive films of thicknesses 300 Å and 350 Å do not show any localization. The resistance of these samples decreases logarithmically with decreasing temperature below 10 K, while a ln(T) increases in resistance is observed for the high resistive films of thickness in the range of 80–120 Å. Magnetoresistance of low resistive samples obeys the expression R(H)/R(O)=AT ⁿ. But, both the resistance and magnetoconductance of the high resistive films are well explained by weak localization and electron-electron interaction effect. From the magnetoconductance measurement, we have calculated the inelastic scattering time ( _i ) and the spin-orbit scattering time ( _so ). The magnitude of spin-orbit scattering time is smaller than the inelastic scattering time. The inelastic scattering has been shown to arise due to the electron-electron scattering and the absolute magnitude of this scattering rate agrees reasonably well with the theory within the temperature range 1.8 KT5 K. At higher temperature (5 K<T20 K), the inelastic scattering time obeys the expression _i T ^–2, due to electronphonon scattering.     

Deposition at low substrate temperatures of high-quality TiO2 films by radical beam-assisted evaporation

We deposited high-quality TiO(2) films by an oxygen-radical beam-assisted evaporation (RBE) method at a lower substrate temperature (Ts) than that for a TiO(2) film deposited by conventional thermal evaporation (TE) with neutral-oxygen gas. The films were then evaluated in terms of refractive index, shift of wavelength of a peak in the reflection curve, and absorption coefficient. The TiO(2) films deposited by RBE at Ts < 473 K showed higher refractive indices, were more compact, and had lower absorption coefficients than the film deposited by TE at Ts = 473 K.     

Solar-light photoamperometric and photocatalytic properties of quasi-transparent TiO2 nanoporous thin films

Transparent photocatalytic surfaces are of ever increasing importance for many applications on self-cleaning windows and tiles in everyday applications. Here, we report the formation and photocatalytic testing of a quasi-transparent thin and nanoporous titania films deposited on glass plates. Sputtered Ti thin films were anodized in fluoride-ion-containing neutral electrolytes to form optically semitransparent nanoporous films, which transformed to be completely transparent after thermal annealing. The nanoporous films were studied at different stages, such as before and after anodization, as well as after thermal annealing using scanning electron microscopy (SEM), X-ray diffraction (XRD), and UV-vis and Raman spectroscopy. It was observed that anodization at 20 V of high-temperature deposited titanium films resulted in regular nanopore films with pore diameters of 30 nm. Structural investigations on the transparent nanopore arrays reveal the presence of anatase phase TiO(2) even after annealing at 500 °C, which was confirmed by XRD and Raman spectroscopy measurements. The solar-light induced photocatalytic decomposition of stearic acid and photoconductivity characteristics of these nanoporous thin films are also presented.     

Tensile deformation of nanostructured TiO2 at low temperatures

Nanostructured TiO₂ with an average grain size of 40 nm was synthesized by the gas condensation technique followed by consolidation and sintering. Pellets of 15 mm diameter and 0.5 mm in thickness were deformed plastically by a gas pressure forming technique. Gas ressures were varied between 100 and 250 kPa, resulting in stresses in the range of 2 to 20 MPa; deformation temperatures varied from 700 to 800°C. After deformation with strains ϵ up to 0.1 the samples did not show any evidence of crackformation. The total deformation at the center of the sample disk, i.e. the apex height, was larger than 2 mm and strain rates were as large as 4 x 10⁻⁶ s⁻¹. These experiments show for the first time that nanostructured ceramics can be deformed plastically under tensile stresses below half the melting point. Although the total strain is still small, larger deformation and net shape forming should be possible by this technique, enabling technological applications of nanostructured ceramics.     

Effects of mineral tourmaline particles on the photocatalytic activity of TiO2 thin films

Titania composite thin films (T/TiO2) containing tourmaline particles were prepared by a sol-gel method, using alkoxide solutions as precursor. The tourmaline particles and thin films were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and so on. The effects of tourmaline on the photocatalytic activity of TiO2 were measured with methyl orange as an objective photodegradation substance. The results showed that the photocatalytic degradation of methyl orange conformed to the first-order kinetic equation and the composite thin films had better photocatalytic activity due to the cooperation of polarity and the far infrared emission of tourmaline. The T/TiO2 thin films including 0.5 wt% tourmaline exhibited better photocatalytic activity when heat-treated at 250 degrees C for 3 h, than pure TiO2 thin films under the ultraviolet irradiation.     

微波等离子体低温制备氮杂二氧化钒薄膜

选用V2O5为前驱物,通过在玻璃片上镀膜,采用微波等离子体增强法,在低温条件下,成功制备了氮杂二氧化钒薄膜.通过X射线衍射(XRD),FT-IR对样品进行表征,结果表明:合成的样品为多晶氮杂二氧化钒.相变温度测试结果表明:退火工艺可以降低相变温度,同时提高薄膜的结晶度;改变氮气流量,相变温度先降低后升高,当氮气流量为20ml/min时,相变温度可以降低至40℃.     

TiO2功能薄膜的制备及影响其光催化活性的因素

近些年来，TiO2功能薄膜以其卓越的性能，尤其是优异的光催化性能引起研究人员的广泛关注，本文根据国内外近期TiO2功能薄膜的研究现状，对化学气相沉积法，水解一沉淀法，液相沉积法，溶胶－凝胶法，原子层沉积法，溅射法，激光辅助分子束沉积法等化学和物理制备方法进行评述，并比较详细地探讨了表面羟基含量，膜的厚度和孔径，结晶形态，基片种类，掺杂和光强度等因素对TiO2薄膜光催化性能的影响。     

锐钛矿型TiO2薄膜的低温制备及性能研究

采用液相沉积法,在低温下制备TiO2薄膜,研究了制备条件对薄膜中TiO2的晶型、薄膜厚度、透光性、亲水性及光催化活性的影响.结果表明,在90℃下制备的TiO2为锐钛矿型,薄膜的厚度与反应温度、沉积时间、HBO3的加入量及反应物浓度有关,所制备的薄膜具有良好的光诱导超亲水特性和光催化活性,在可见光区的透光率＞80%.     

纳米TiO2薄膜的低温制备与光谱特性研究

以钛酸丁酯为原料,采用改进溶胶-凝胶法,通过浸渍-提拉工艺在低温条件下制备了锐钛矿纳米TiO2薄膜。利用X射线衍射、紫外-可见光吸收光谱、傅里叶变换红外光谱对所制备的TiO2薄膜的晶型结构和光谱特性进行了分析,并利用紫外光照降解亚甲基蓝溶液来评价所制备薄膜的光催化活性。结果表明:经过陈化和水浴处理后,钛酸丁酯完全水解,所得TiO2薄膜为锐钛矿结构,对紫外光表现出较强的吸收特性。低温水浴处理有利于提高薄膜的光催化活性。     

Preparation and characterization of TiO2 thin films by the sol-gel process

Titanium dioxide (TiO₂) thin films have been prepared on microscope slide by the sol-gel process. The preparation of covering solution is investigated with the method of orthogonal experimental design, and the heat treatment temperature and time, which influenced on the films properties are discussed. And the TiO₂ thin films had been studied by the means of differential thermal analysis (DTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM).     

Influence of physico-structural properties on the photocatalytic activity of sol-gel derived TiO2 thin films

Sol-gel TiO₂ films were deposited from various sols and heat-treated at different temperatures. Fourier transform infrared spectroscopy, ellipsometry, X-ray diffraction, and scanning electron microscopy methods have been used to study physico-structural properties of the films. These properties are discussed with respect to the experimental parameters. It is shown that, depending on sol formulations and annealing temperatures, a large range of crystallite size, crystallization degree, film porosity, and surface morphology can be covered. The photocatalytic properties of the films have been studied in relation to their physico-structural properties through the photodecomposition of malic acid. This study shows that the photocatalytic activity undergoes a complex dependence on the physico-structural properties.     

非晶硅薄膜晶化过程的研究

多晶硅薄膜具有较高的电迁移率和稳定的光电性能,是制备微电子器件、薄膜晶体管、大面积平板液晶显示的优质材料.多晶硅薄膜被公认为是制备高效、低耗、最理想的薄膜太阳能电池的材料.因此,如何制备多晶硅薄膜是一个非常有意义的研究课题.固相法是制备多晶硅薄膜的一种常用方法,它是在高温退火的条件下,使非晶硅薄膜通过固相相变而成为多晶硅薄膜.本文采用固相法,利用X-ray衍射及拉曼光谱,对用不同方法制备的非晶硅薄膜的晶化过程进行了系统地研究.     

Enhanced photocatalytic activity of C-N-codoped TiO2 films prepared via an organic-free approach

An organic-free sol-gel method was developed to synthesize crack-free, high surface roughness and visible-light-active C-N-codoped TiO(2) films. These films were subsequently evaluated for its photodegradation efficient using stearic acid as the model pollutant compound. The current approach avoids the use of hazardous organic solvents and employs carbon black as the carbon source as well as a template to increase the surface roughness. The presence of carbon and nitrogen species in TiO(2) was studied and discussed. The concentrations of carbon and nitrogen dopants in the TiO(2) films were affected by calcination temperature and the concentration of carbon black. Optimal visible light photocatalytic activity was observed for C-N-codoped TiO(2) film at 10.0 wt.% C, which was more than double that of the N-doped TiO(2) film. The enhancement in visible light photocatalytic activities of the C-N-codoped TiO(2) films was attributed to the synergistic effects of carbon and nitrogen dopants, and high surface roughness of the prepared films.     

Synthesis of nanocrystalline TiO2 thin films by liquid phase deposition technique and its application for photocatalytic degradation studies

A transparent, high purity titanium dioxide thin film composed of densely packed nanometer sized grains has been successfully deposited on a glass substrate at 30°C from an aqueous solution of TiO₂-HF with the addition of boric acid as a scavenger by liquid phase deposition technique. From X-ray diffraction measurement, the deposited film was found to be amorphous and turns crystalline at 500°C. The deposited film showed excellent adherence to the substrate and was characterized by homogeneous flat surface. TiO₂ thin films can be used as a photocatalyst to clean up organohalides, a class of compound in pesticides that pollute the ground water. Photocatalytic degradation experiments show that indanthrene golden orange dye undergoes degradation efficiently in presence of TiO₂ thin films by exposing its aqueous solution to ultraviolet light. The suitable surface structure and porosity increases the photocatalytic activity. It was also observed that hemin doped TiO₂ thin films break up organohalides at a surprisingly high rate under visible light.     

Defective TiO2 prepared via synchronous crystallization and constraint reduction strategy with enhanced photocatalytic activity

Journal of Materials Science: Materials in Electronics - Defects (oxygen vacancy and Ti3+) play crucial roles in determining band structure, light absorption, and catalytic activity of TiO2....