高压对高功率脉冲磁控放电等离子体注入与沉积氧化钒薄膜的影响

利用高功率脉冲磁控放电等离子体注入与沉积技术制备了氧化钒薄膜,分别采用X射线衍射仪、原子力显微镜、扫描电子显微镜和电化学分析仪研究了不同高压幅值对氧化钒薄膜的相结构、表面形貌、截面形貌以及耐腐蚀性能的影响。结果表明制备的氧化钒薄膜以VO2(-211)相为主,还含有少量的VO2(111)、VO(220)、VO(222)相。不同高压下氧化钒薄膜表面致密、平整,其表面粗糙度仅为几个纳米,显示出良好的表面质量。氧化钒薄膜表现出典型致密的柱状晶生长形貌,且随着高压增加,氧化钒薄膜膜层厚度有所下降。氧化钒薄膜耐腐蚀性能较纯铝基体有较大提高,腐蚀电位提高0.093V,腐蚀电流下降1～2个数量级;当高压为-15kV时,氧化钒薄膜腐蚀电位最高,腐蚀电流最低,表现出最佳的耐蚀性能。     

Electron back-scattered diffraction of crystallized vanadium dioxide thin films on amorphous silicon dioxide

Crystalline films and isolated particles of vanadium dioxide (VO₂) were obtained through solid phase crystallization of amorphous vanadium oxide thin films sputtered on silicon dioxide. Electron back-scattered diffraction (EBSD) was used to study the crystals obtained in the thin films, to differentiate them from different vanadium oxide stoichiometries that may have formed during the annealing process, and to study their phase and orientation. EBSD showed that the crystallization process yielded crystalline vanadium dioxide thin films, semi-continuous thin films, and films of isolated particles, and did not show evidence of other vanadium oxide stoichiometries present. Indexing of the crystals for the orientation study was performed using EBSD patterns for the tetragonal phase of vanadium dioxide, since it was observed that EBSD patterns for the monoclinic and tetragonal phases of vanadium dioxide are not distinguishable by computer automated indexing. Using the EBSD patterns for the tetragonal phase of vanadium dioxide, orientation maps showed that all VO₂ crystals that were measurable (approximately the thickness of the film) had a preferred orientation with the c-axis of the tetragonal phase parallel to the plane of the specimen.     

Nano-polycrystalline vanadium oxide thin films prepared by pulsed laser deposition

Nano-polycrystalline vanadium oxide thin films have been successfully produced by pulsed laser deposition on Si(100) substrates using a pure vanadium target in an oxygen atmosphere. The vanadium oxide thin film is amorphous when deposited at relatively low substrate temperature (500 degrees C) and enhancing substrate temperature (600-800 degrees C) appears to be efficient in crystallizing VOx thin films. Nano-polycrystalline V3O7 thin film has been achieved when deposited at oxygen pressure of 8 Pa and substrate temperature of 600 degrees C. Nano-polycrystalline VO2 thin films with a preferred (011) orientation have been obtained when deposited at oxygen pressure of 0.8 Pa and substrate temperatures of 600-800 degrees C. The vanadium oxide thin films deposited at high oxygen pressure (8 Pa) reveal a mix-valence of V5+ and V4+, while the VOx thin films deposited at low oxygen pressure (0.8 Pa) display a valence of V4+. The nano-polycrystalline vanadium oxide thin films prepared by pulsed laser deposition have smooth surface with high qualities of mean crystallite size ranging from 30 to 230 nm and Ra ranging from 1.5 to 22.2 nm. Relative low substrate temperature and oxygen pressure are benifit to aquire nano-polycrystalline VOx thin films with small grain size and low surface roughness.     

Growth and structural characterisation of vanadium oxide ultrathin films on TiO2 (110)

The research activity of our group in the last few years has mainly been devoted to the study of ultrathin vanadium oxide films deposited on a (110)-oriented TiO₂ single crystal, in order to prepare systems which may be largely thought of as simplified models for the investigation of the structure/properties relationships in real world catalysts, sensing and optical devices. The main objective of our work consists of setting up reproducible synthesis routes for the deposition of vanadium oxide ultrathin films on TiO₂ (110), through strict control of the reaction parameters. The films obtained are then characterised from a chemical, electronic and structural point of view, and their properties are compared to those of their bulk-related phases. Results are presented concerning growth procedures and structural and electronic properties of vanadium oxide ultrathin films on titania, with a stoichiometry ranging from VO₂, down to approximately VO. In particular, it will be shown that the oxidation product of metallic vanadium in an oxygen or water atmosphere (in the 10⁻⁶ mbar range) retains the rutile lattice structure typical of stoichiometric VO₂, despite the increasing degree of oxygen defectiveness and the electronic properties, very similar to those pertaining to bulk V₂O₃. The peculiar behaviour of vanadium oxide on titania demonstrates how important the epitaxial influence of the substrate is on the nature of the overlayer. These results could represent a good starting point to understand why vanadium oxides on TiO₂ show an enhanced catalytic activity and selectivity in many industrially relevant reactions.     

Optical properties of thin films of amorphous vanadium oxides

The results of an experimental investigation of the optical properties of anodic vanadium oxide films are presented. It is shown that films of different phase composition (VO₂, V₂O₅, or a mixture of two phases) can be obtained, depending on the oxidation regime, and that the absorption and transmission spectra are modified significantly in accordance. The optical properties of the oxides, whose composition is close to stoichiometric vanadium dioxide, demonstrate the occurrence of a metal-semiconductor phase transition in the amorphous films. The results presented are important both from the standpoint of technical applications of thin film systems based on anodic vanadium oxides and for more detailed understanding of the physical mechanism of the metal-semiconductor phase transition and the influence of structural disorder on the transition. Pis’ma Zh. Tekh. Fiz. 25, 81–87 (April 26, 1999)     

Chemical bath deposition and characterization of electrochromic thin films of sodium vanadium bronzes

Thin yellow-orange films of sodium vanadium oxide bronzes have been prepared from a sodium–vanadium solution (1:1) at 75 °C and pH = 3. The composition, structure and morphology of the films have been studied by XRD, IR spectroscopy, TG and SEM–EDX analyses. It has been established that the prepared films are a phase mixture of hydrated NaV₆O₁₅ (predominant component) and Na_1.1V₃O_7.9 with total water content of 10.58%.The sodium vanadium bronze thin films exhibit two-step electrochromism followed by color change from yellow-orange to green, and then from green to blue. The cyclic voltammetry measurements on the as-deposited and annealed vanadium bronze films reveal the existence of different oxidation/reduction vanadium sites which make these films suitable for electrochromic devices. The annealing of the films at 400 °C changes the composition, optical and electrochemical properties     

氧化钒薄膜热敏特性的研究

为研究氧化钒薄膜在非致冷红外微测辐射热计中的应用,综述了制备工艺等诸多因素对氧化钒热敏特性的影响,对其机理进行了探究,结果表明掺杂和新的制备工艺是调整氧化钒热敏特性较为有效的方法.     

晶粒尺寸对氧化钒薄膜电学与光学相变特性的影响

采用直流对靶磁控溅射方法制备氧化钒薄膜,通过改变热处理温度获得了具有不同晶粒尺寸的相变特性氧化钒薄膜,对氧化钒薄膜相变过程中电阻和红外光透射率随温度的突变性能进行研究.结果表明:经300℃和360℃热处理后,薄膜内二氧化钒原子分数达到40%,氧化钒薄膜具有绝缘体-金属相变特性,薄膜的晶粒尺寸分别为50nm和100nm;...     

Ti1-xVxO2薄膜的制备及光电性能

用溶胶凝胶法制备了Ti1-xVxO2薄膜，用X射线衍射分析了Ti1-xVxO2的结晶性能，用Lambda紫外－可见光光度计测量了吸收光谱，用ZC36高阻仪测量了Ti1-xVxO2薄膜样品的电性能，结果表明，钒含量的增加导致Ti1-xVxO2薄膜光学吸收限红移，在形成固溶体后薄膜的电阻率随钒含量增加而下降，在x=0.15时，V2O5相的出现使Ti1-zVxO2薄膜的电阻出现一峰值，Ti1-xVxO2薄膜电阻率的这种变化规律是由于V的3d电子的引入和薄膜结晶性的变化。     

Sol–gel derived PZT films doped with vanadium pentoxide

The present research investigated the sol–gel preparation, dielectric and ferroelectric properties of PZT films doped with 5 mol% vanadium oxide. Stable PZTV sols can be readily formed, and homogeneous, micrometer thick and pinhole-free PZTV films were obtained by using spin coating followed with rapid annealing. The X-ray diffraction patterns revealed that no parasitic or secondary phases were formed in the sol–gel PZT films with the addition of vanadium oxide. The material doped with vanadium pentoxide showed enhanced dielectric constant and remanent polarization with reduced loss tangent and coercive field.     

双靶磁控溅射制备掺W氧化钒薄膜的研究

用双靶磁控溅射制备了掺钨氧化钒薄膜。Ｘ射线电子谱（ＸＰＳ）对所沉积的薄膜进行了分析,发现掺Ｗ氧化钒薄膜的相结构比较复杂。通过特征峰标定了这些相。用面积灵敏度因子方法得到Ｗ掺杂量的结果。原子力显微镜给出了薄膜的表面形貌。其表面形貌特征随沉积条件的不同有一定的变化。     

Work function of vanadium dioxide thin films across the metal-insulator transition and the role of surface nonstoichiometry

Vanadium dioxide (VO(2)) undergoes a sharp metal-insulator transition (MIT) in the vicinity of room temperature and there is great interest in exploiting this effect in novel electronic and photonic devices. We have measured the work function of vanadium dioxide thin films across the phase transition using variable temperature Kelvin force microscopy (KFM). The work function is estimated to be ～5.15 eV in the insulating phase and increases by ～0.15 eV across the MIT. We further show that the work function change upon the phase transition is highly sensitive to near-surface stoichiometry studied by X-ray photoelectron spectroscopy. This change in work function is distinct from bulk resistance-versus temperature trends commonly used to evaluate synthesis protocols for such vanadium oxide films and optimize stoichiometry. The results are pertinent to understanding fundamental electronic properties of vanadium oxide as well as charge injection phenomena in solid-state devices incorporating complex oxides containing multivalence cations.     

Efficiency improvement of multicrystalline silicon solar cells after surface and grain boundaries passivation using vanadium oxide

The aim of this work is to investigate the effect of vanadium oxide deposition onto the front surface of multicrystalline silicon (mc-Si) substrat, without any additional cost in the fabrication process and leading to an efficient surface and grain boundaries (GBs) passivation that have not been reported before. The lowest reflectance of mc-Si coated with vanadium oxide film of 9% was achieved by annealing the deposited film at 600 °C. Vanadium pentoxide (V₂O₅) were thermally evaporated onto the surface of mc-Si substrates, followed by a short annealing duration at a temperature ranging between 600 °C and 800 °C, under O₂ atmosphere. The chemical composition of the films was analyzed by means of Fourier transform infrared spectroscopy (FTIR). Surface and cross-section morphology were determined by atomic force microscope (AFM) and a scanning electron microscope (SEM), respectively. The deposited vanadium oxide thin films make the possibility of combining in one processing step an antireflection coating deposition along with efficient surface state passivation, as compared to a reference wafer. Silicon solar cells based on untreated and treated mc-Si wafers were achieved. We showed that mc-silicon solar cells, subjected to the above treatment, have better short circuit currents and open-circuit voltages than those made from untreated wafers. Thus, the efficiency of obtained solar cells has been improved.     

Ion-plasma modification of the properties of anodic films of transition metal oxides

We have studied the effect of high-frequency (13.56 MHz) capacitive discharge in argon on thin films of amorphous vanadium and niobium oxides grown by electrochemical oxidation in an electrolyte. The results of X-ray diffraction, spectrophotometric, and electrical measurements show that the plasma processing leads to modification of the electrical properties (growth in the electron conductivity), structure (crystallization), and optical characteristics (optical density variation in the short-wavelength range) of the oxide films.     

Vacancy-induced electronic states in substoichiometric V2 −x Mo x O3 ±y thin films and powders—A soft X-ray emission study

Vanadium oxide as well as molybdenum oxide thin films have been found to show electrochromism and metal insulator transitions. Incorporation of vanadium ion into molybdenum oxide lattice not only changes the lattice parameters but also shows prominent spectral changes in X-ray emission spectra. K_β1-3 emission spectra of vanadium in different alloy films of V₂O₅-MoO₃ system have been studied here and these have been compared with the X-ray emission spectra of similar composition of V₂O₅-MoO₃ powders. For K_β1-3 emission, the difference in values of asymmetry indices of thin films and powders is marginal, although considerable tailing towards high energy is observed in thin films. By curve fitting procedure, the K_β1-3 emission spectra have been resolved to several gaussian peaks, and these have been explained on the basis of vacancy-induced electronic states, crossover transitions advocated in molecular orbital theory and plasmon oscillation.     

P-type transparent Ti-V oxides semiconductor thin film as a prospective material for transparent electronics

In this paper electrical and optical properties of mixed titanium and vanadium oxides (Ti-V oxides) thin films have been outlined. Thin films were deposited by sputtering of mosaic Ti-V target in reactive oxygen plasma using high energy magnetron sputtering process. From elemental analysis results, 19 at.% of vanadium was incorporated into thin films and X-ray diffraction investigations displayed their amorphous behavior. However, images obtained by the use of an atomic force microscope displayed a densely packed nanocrystalline structure. It has been found that V addition considerably improves the electrical conduction of prepared Ti-V oxide thin films as compared to undoped TiO₂ and results in p-type electrical conduction. Resistivity of Ti-V oxides thin films was found at the order of 10⁵ Ω cm. Optical measurements have shown the average transmission coefficient of about 73% in the visible spectral range and that the position of fundamental absorption edge has been shifted by 40 nm towards the longer wavelength as compared to the undoped TiO₂. The results testified that the prepared Ti-V oxides thin films might be considered as a p-type transparent oxide semiconductors for future application in transparent electronics.     

Oxidation phase growth diagram of vanadium oxides film fabricated by rapid thermal annealing

Thermal evaporation deposited vanadium oxide films were annealed in air by rapid thermal annealing (RTP). By adjusting the annealing temperature and time, a series of vanadium oxide films with various oxidation phases and surface morphologies were fabricated, and an oxidation phase growth diagram was established. It was observed that different oxidation phases appear at a limited and continuous annealing condition range, and the morphologic changes are related to the oxidation process.     

氧化钒薄膜制备与特性研究

用磁控反应溅射法制备出具有红外敏感特性的氧化钒薄膜,进行了薄膜光电特性的测试.通过AFM和XRD对薄膜的结构和特性进行分析研究,并给出了沉积参数对薄膜性能的影响.     

Layer-by-layer nanostructured hybrid films of polyaniline and vanadium oxide

Supramolecular structures of polyaniline (PANI) and vanadium oxide (V2O5) have been assembled via the electrostatic layer-by-layer (ELBL) technique. Strong ionic interactions and H-bonding impart unique features to the ELBL films, which are distinct from cast films obtained with the same materials. The interactions were manifested in UV-vis and Fourier transform infrared spectroscopy data. They are enhanced by the intimate contact between the components, as the films are molecularly thin, with 25 A per PANI/V2O5 bilayer.