氧化钨多孔薄膜的制备及光学性质

多孔结构可以使氧化钨薄膜的气敏、电致变色等性能得到增强,但目前多孔氧化钨薄膜的制备仍存在困难。本文采用W和Al双靶磁控溅射的方法得到了W-Al合金薄膜后,把合金薄膜浸入NaOH溶液中处理,其中的Al被腐蚀同时W被氧化,从而得到了多孔的氧化钨薄膜。利用SEM观察多孔氧化钨薄膜样品的表面形貌,用XPS分析样品中W的价态,用XRD分析样品的晶体结构,用紫外-可见-近红外分光光度计测量样品的光学性质。结果显示:制得的多孔氧化钨薄膜的平均孔径在100nm左右,呈海绵状疏松结构;薄膜中W的价态以+5价为主;薄膜属于非晶相;在可见光区域,多孔氧化钨薄膜具有较高的透过率,而在近红外区域则具有近似平直的透过率曲线。     

甩胶喷雾热分解法制备ITO薄膜及光电性能研究

按In:Sn(物质的量比)=9:1,InCl3·4H2O和SnCl4·5H2O为前驱物,采用自制甩胶喷雾热分解制备薄膜装置在普通玻璃衬底上沉积了ITO薄膜,结果表明,采用自制甩胶喷雾热分解制备薄膜新装置成功制备出ITO薄膜。该装置结构简单、操作方便。制备ITO薄膜优化条件为:甩胶转速800r/min、衬底温度250℃、退火温度450℃、载气为空气、流量为7L/min、液体雾化速度0.2ml/min、雾粒速度3.5m/s。薄膜的沉积时间为5min,薄膜厚度约1000nm,最低电阻率为0.75*10-4Ω·cm,薄膜在可见光范围(波长在400-700nm)内平均透光率为87.2%。衬底温度在200℃以上时呈现立方相结构。     

Morphology-controlled flame synthesis of single, branched, and flower-like α-MoO3 nanobelt arrays

We report an atmospheric, catalyst-free, rapid flame synthesis technique for growing single, branched, and flower-like α-MoO(3) nanobelt arrays on diverse substrates. The growth rate, morphology, and surface coverage density of the α-MoO(3) nanobelts were controlled by varying the flame equivalence ratio, the source temperature, the growth substrate temperature, and the material and morphology of the growth substrate. This flame synthesis technique is a promising, alternative way to synthesize one-dimensional metal oxide nanostructures in general.     

Growth mechanism of ZnO nanostructures in wet-oxidation process

Zinc (Zn) thin films were prepared by direct current magnetron sputtering as precursors with different deposition times. Zinc oxide (ZnO) nanostructures such as nanowires, nanobelts and nanoblades were then synthesized from the Zn precursors by wet-oxidation process. The microstructures of the Zn precursor and ZnO nanostructures have been studied by scanning electronic microscopy and X-ray diffractometry. The optoelectronic properties were analyzed by photoluminescence measurement. It was found that the Zn precursor film with a porous top layer consisting of well-crystallized Zn grains is an essential for formation of ZnO nanowires. Along with time dependence study and temperature dependence studies, the ZnO nanostructure growth mechanisms during the wet-oxidation process are proposed: water vapor has a major influence on the initial stage, and the final dimensions of the nanostructure are controlled by the vapor-solid process.     

Hot-wire chemical vapor deposition of WO3−x thin films of various oxygen contents

We present the synthesis of tungsten oxide (WO_3−x) thin films consisting of layers of varying oxygen content. Configurations of layered thin films comprised of W, W/WO_3−x, WO₃/W and WO₃/W/WO_3−x are obtained in a single continuous hot-wire chemical vapor deposition process using only ambient air and hydrogen. The air oxidizes resistively heated tungsten filaments and produces the tungsten oxide species, which deposit on a substrate and are subsequently reduced by the hydrogen. The reduction of tungsten oxides to oxides of lower oxygen content (suboxides) depends on the local water vapor pressure and temperature. In this work, the substrate temperature is either below 250 °C or is kept at 750 °C. A number of films are synthesized using a combined air/hydrogen flow at various total process pressures. Rutherford backscattering spectrometry is employed to measure the number of tungsten and oxygen atoms deposited, revealing the average atomic compositions and the oxygen profiles of the films. High-resolution scanning electron microscopy is performed to measure the physical thicknesses and display the internal morphologies of the films. The chemical structure and crystallinity are investigated with Raman spectroscopy and X-ray diffraction, respectively.     

Soft solution synthesis of ZnO films with developed superstructures

A novel and simple two-step solution approach to prepare ZnO thin film consisted of 3D flower-like superstructure was demonstrated. The uniform, nano-dimensional scale and sphere-like ZnO crystals were first prepared on the borosilicate glass substrate in mild solution at 95 degrees C for 3 h, then introduced into 0.02 mol L(-1) hexamethylenetetramine (HMT, C6H12N4) aqueous solution and heated at the same temperature for 3 d. The obtained ZnO thin films were characterized by XRD, SEM and photoluminescence. The results indicated that the thin film with 3D flower-like superstructure possessed high crystallinity, high surface-volume ratio microstructure and excellent photoluminescence property. It is a potential way to prepare nano-structured materials by the mentioned simple and novel two-step solution synthesis process.     

Phase formation and morphology control of niobium oxide nanopillars

Nanopillar metal oxide thin films offer versatility as ultra high surface area supports and conductors. Metal oxide properties (e.g. stability, conductivity) can be tuned via phase and composition control to achieve desired application-specific functionality. Here we demonstrate phase control of high surface area thin films grown by glancing angle deposition and transformed to desired phases through high temperature annealing in a reducing environment. The post-annealed properties such as stoichiometry, phase, and morphology are shown to be largely dependent on initial film structure and hydrogen forming gas flow rate. Initially amorphous films of approximate stoichiometry Nb₂O₅ are transformed to NbO₂ or NbN_xO_1−x through annealing. Transformation to oxygen-deficient phases is more easily achieved for films of higher initial porosity. Higher forming gas flow rates result in both increased oxygen removal and significantly less physical degradation of nanostructures. A phase map is included as a guide to phase formation and morphology control in annealed nanopillar niobium oxide films.     

Atomic layer deposition on biological macromolecules: metal oxide coating of tobacco mosaic virus and ferritin

Decoration of nanoparticles, in particular biomolecules, gathered high attention in recent years.(1-7) Of special interest is the potential use of biomolecules as templates for the fabrication of semiconducting or metallic nanostructures.(1-7,26) In this work we show the application of atomic layer deposition, a gas-phase thin film deposition process, to biological macromolecules, which are frequently used as templates in nanoscale science, and the possibility to fabricate metal oxide nanotubes and thin films with embedded biomolecules.(1-13).     

ITO及WO3在电解液中的交流阻抗特性

采用表面过程法拉第阻纳表达式方法与等效电路方法，研究透明ITO平面电极及带WO3薄膜层的ITO平面电极处于1mol LiClO4丙烯碳酸酯电解液中的电化学阻抗谱．分析显示WO3薄膜层有效地阻止了表面吸附参量对ITO电极反应的影响，使电极反应仅受电极电位的影响，并且随WO3薄膜在电解液中浸泡时间的增加，WO3薄膜的常相位角元件的特性最终回归为电容效应．     

Fabrication of diamond microstructures for microelectromechanical systems (MEMS) by a surface micromachining process

Selective polycrystalline diamond thin film has been grown on a silicon dioxide/silicon substrate using high pressure microwave plasma-assisted chemical vapor deposition from a gas mixture of methane and hydrogen at a substrate temperature of 950°C. A simple process flow has been developed to fabricate diamond microstructures such as diamond beams and cantilever beams using surface micromachining and photolithography for the first time. Scanning electron and optical microscopy has been used to characterize the surface micromachined diamond microstructures.     

In situ fabrication of Bi2S3 nanocrystal film for photovoltaic devices

A facile wet-chemical method to prepare Bi₂S₃ thin films with flake nanostructures directly on ITO glass substrate is presented in this paper for the first time. The product was characterized by X-ray powder diffractometer (XRD), Raman spectrometer, scanning electron microscope (SEM), and atomic force microscope (AFM). The one-step solvothermal elements treatment on the ITO substrate spare time to form film by spin-coating process and the film could be tightly attached to the ITO electrode. A conjugated polymer, poly 3-hexylthiophene (P3HT), was then spin-coated on the as-prepared Bi₂S₃ film to form an inorganic-organic hybrid thin film. The photovoltaic performance of the resulting solar cell device was also investigated.     

Growth condition dependence of zinc oxide nanostructures on Si substrates in an electrochemical process

Zinc oxide nanostructures were synthesized in an aqueous solution of hexamine and zinc nitrate by an electrochemical process. The effects of growth conditions, including electrical potential, growth temperature and template size, on morphology and composition of the nanostructures were systematically investigated. A negative potential enhanced the growth of single crystalline ZnO nanowire arrays while a positive potential caused nano-disks of ZnO and ZnO₂ composites to grow on the substrate. The applied negative potential also helped room temperature growth of ZnO nanowires with a reduced growth rate. Similar growth behavior was observed on a bare substrate and that with pre-defined polymer template.     

Aluminum contact to nickel silicide using a thin tungsten barrier

An aluminum film in contact with NiSi is not stable in the temperature range around 450 °C usually applied for aluminum contact sintering. We used thin (about 2 kÅ) self-supported silicon substrates to investigate the interaction of aluminum films with NiSi by mega-electronvolt ⁴He⁺ backscattering spectrometry. The thin substrate enables us to distinguish between the aluminum and the silicon signals, to isolate them, and to analyze the reaction. It is found that the aluminum reacts with the silicide and forms an NiAl₃ layer in direct contact with the silicon substrate. Simultaneously, a rise in the Schottky barrier height of the contact is observed. A thin layer (250 Å) of tungsten placed as a barrier between the aluminum and the silicide is shown to inhibit the aluminum-silicide reaction. A process is described to prepare a reliable aluminum contact to NiSi on a silicon substrate in a single annealing step.     

Fabrication of high frequency ZnO thin film SAW devices on silicon substrate with a diamond-like carbon buffer layer using RF magnetron sputtering

Diamond-like carbon (DLC) film is a promising candidate for surface acoustic wave (SAW) device applications because of its higher acoustic velocity. A zinc oxide (ZnO) thin film has been deposited on DLC film/Si substrate by RF magnetron sputtering; the optimized parameters for the ZnO sputtering are RF power density of 0.55 W/cm², substrate temperature of 380 °C, gas flow ratio (Ar/O₂) of 5/1 and total sputter pressure of 1.33 Pa. The results showed that when the thickness of the ZnO thin films was decreased, the phase velocity of the SAW devices increased significantly.     

Preparation and properties of surface textured ZnO: Al films by direct current pulse magnetron sputtering

Transparent conductive surface textured Al-doped zinc oxide (ZnO:Al, AZO) thin films were prepared on glass substrates by direct current pulse magnetron sputtering at substrate temperature of 270 °C and post-etching in NaOH solution at room temperature. The effects of Ar flow rate on the structural, optical, electrical properties and light trapping ability were investigated systematically. With the increasing of Ar flow rate from 10 to 50 sccm, different surface features ranging from honeycomb-like to crater-like structures were observed. The relationship between surface textured structures and Ar flow rate was discussed. The AZO film deposited with Ar flow rate in 50 sccm displayed fine optoelectronic properties, improved figure of merit and effective surface textured structures for light trapping, which could be applied as a transparent conducting electrode in silicon-based thin film solar cells.     

Deposition and characterization of a novel integrated ZnO nanorods/thin film structure

One-dimensional (1-D) ZnO (zinc oxide) nanostructures have received a lot of attention due to their superior properties. Various techniques have been developed to synthesize ZnO nanorods at high-temperature process using vapor–liquid–solid (VLS) mechanism. In this paper, we report a novel process to synthesize integrated ZnO nanorods/thin film structures using an RF magnetron sputter deposition under different deposition parameters and substrate conditions. The substrate used was glass plated with electroless Cu prepared using various conditions. The resulting specimens are analyzed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The effect of the copper surface roughness was found to be significant. ZnO nanorods were found only when the copper layer is rough enough. The roughness of the copper in general increases with the plating time and/or the ratio of V_HCHO/V_Cu used in the plating bath. Post-plating annealing of the copper was also found to increase the surface roughness of the copper.     

Elaboration and characterization of Fe1-xO thin films sputter deposited from magnetite target

Majority of the authors report elaboration of iron oxide thin films by reactive magnetron sputtering from an iron target with Ar-O₂ gas mixture. Instead of using the reactive sputtering of a metallic target we report here the preparation of Fe_1-xO thin films, directly sputtered from a magnetite target in a pure argon gas flow with a bias power applied. This oxide is generally obtained at very low partial oxygen pressure and high temperature. We showed that bias sputtering which can be controlled very easily can lead to reducing conditions during deposition of oxide thin film on simple glass substrates. The proportion of wustite was directly adjusted by modifying the power of the substrate polarization. Atomic force microscopy was used to observe these nanostructured layers. Mössbauer measurements and electrical properties versus bias polarization and annealing temperature are also reported.     

Preparation of size-controlled tungsten oxide nanoparticles and evaluation of their adsorption performance

The present study investigated the effects of particle size on the adsorption performance of tungsten oxide nanoparticles. Nanoparticles 18-73 nm in diameter were prepared by evaporation of bulk tungsten oxide particles using a flame spray process. Annealing plasma-made tungsten oxide nanoparticles produced particles with diameters of 7-19 nm. The mechanism of nanoparticle formation for each synthetic route was examined. The low-cost, solid-fed flame process readily produced highly crystalline tungsten oxide nanoparticles with controllable size and a remarkably high adsorption capability. These nanoparticles are comparable to those prepared using the more expensive plasma process.     

Preparation of inorganic solid state thin film for electrochromic application

All oxide solid state ITO (indium tin oxide)/Li_yWO_3−x/Li_1−zMn₂O₄/ITO stacked structure was deposited on a silica glass substrate by pulsed laser deposition for its electrochromic application. The Li doped amorphous tungsten trioxide Li_yWO_3−x thin film prepared at room temperature and in oxygen pressure of 7 Pa got the color of blue due to the mixture valence state of tungsten. We found that the amorphous Li_1−zMn₂O₄ thin film was suitable for the electrochromic application in spite of the low ion conductivity along in-plane direction. The ITO electrode thin film deposited at room temperature showed the relatively high transmittance and the usable conductivity. The transmittance at a wavelength of 750 nm for the ITO/Li_yWO_3−x/Li_1−zMn₂O₄/ITO stacked film changed from 50% to 80% by the applied voltage, while the transmittance at around 450 nm did not change. The blue-colored electrochromic property could be observed for the all oxide solid state film.     

化学气相沉积制备纳米结构碳化钨薄膜

采用氟化钨(WF6)和甲烷(CH4)为前驱体,采用等离子体增强化学气相沉积(PECVD)方法制备具有纳米结构的碳化钨薄膜。采用SEM、XRD、EDS等方法表征了碳化钨薄膜的形貌、晶体结构和化学组成。通过表征,表明在前驱体混合气体中的甲烷与氟化钨气体的流量比(碳钨比)为20、基底温度为800℃的条件下得到的碳化钨薄膜是由直径为20～35nm的圆球状纳米晶构成。通过分析影响薄膜的晶体结构、化学组成的因素后,认为要得到具有纳米晶结构的碳化钨薄膜,主要应控制前驱体气体中的碳钨比以及基底温度。