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1.
X-ray photoelectron spectroscopy (XPS) was adopted for the analytical characterization of composite titanium dioxide–poly(vinylidenefluoride) (TiO 2–PVDF) films developed for applications in the photocatalytic degradation of pollutants. The composites were deposited on glass substrates by casting or spin coating from TiO2–PVDF suspensions in dimethylformamide (DMF). XPS data on the TiO2–PVDF surface composition were used to optimize preparation conditions (composition of the TiO2/PVDF suspension, deposition technique) in terms of titanium dioxide surface amount and film stability. The use of spin-coating deposition and the increase of TiO2 amount in the DMF suspensions were found to improve the titanium surface content, although high TiO2/PVDF ratios led to film instability. PVDF–TiO2 films were also used in preliminary photocatalytic degradation tests on isoproturon, a phenylurea herbicide, under solar UV irradiation; the results were compared to direct photolysis to evaluate the catalytic efficiency of immobilized TiO2 and the role played by the PVDF film during the degradation process. 相似文献
2.
The morphology and chemical characteristics of the surface and the interface of TiO 2–muscovite nanocomposites were studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Our results clearly showed that TiO 2 grains formed on the TiO 2 thin film surface, whereas the presence of TiO 2 grains on the interface between TiO 2 thin films and the muscovite substrates was not obvious. While euhedral rutile grains were found in samples doped with Zn ions, none were found in samples doped with Sn ions. The XPS results showed that cations present in the muscovite substrates diffused into the TiO 2 thin films. Etching measurements revealed that diffusion abilities of cation impurities varied: Si and Al diffused more easily than K. The observed differences in chemical composition and oxidation of the elements, especially on the surface and the subsurface, may influence the different crystallization behaviors of elements in TiO 2 thin films and the different active degree of elements diffusing from muscovite substrates. 相似文献
3.
In this study, we will develop the influences of the excess x wt% ( x=0, 1, 2, and 3) Bi 2O 3-doped and the different fabricating process on the sintering and dielectric characteristics of 0.95 (Na 0.5Bi 0.5)TiO 3–0.05 BaTiO 3 ferroelectric ceramics with the aid of SEM and X-ray diffraction patterns, and dielectric–temperature curves. The 0.95 (Na 0.5Bi 0.5)TiO 3–0.05 BaTiO 3+ x wt% Bi 2O 3 ceramics are fabricated by two different processes. The first process is that (Na 0.5Bi 0.5)TiO 3 composition is calcined at 850 °C and BaTiO 3 composition is calcined at 1100 °C, then the calcined (Na 0.5Bi 0.5)TiO 3 and BaTiO 3 powders are mixed in according to 0.95 (Na 0.5Bi 0.5)TiO 3–0.05 BaTiO 3+ x wt% Bi 2O 3 compositions. The second process is that the raw materials are mixed in accordance to the 0.95 (Na 0.5Bi 0.5)TiO 3–0.05 BaTiO 3+ x wt% Bi 2O 3 compositions and then calcining at 900 °C. The sintering process is carried out in air for 2 h from 1120 to 1240 °C. After sintering, the effects of process parameters on the dielectric characteristics will be developed by the dielectric–temperature curves. Dielectric–temperature properties are also investigated at the temperatures of 30–350 °C and at the frequencies of 10 kHz–1 MHz. 相似文献
4.
Polycrystalline (1− x)Ta 2O 5− xTiO 2 thin films were formed on Si by metalorganic decomposition (MOD) and annealed at various temperatures. As-deposited films were in the amorphous state and were completely transformed to crystalline after annealing above 600 °C. During crystallization, a thin interfacial SiO 2 layer was formed at the (1− x)Ta 2O 5− xTiO 2/Si interface. Thin films with 0.92Ta 2O 5–0.08TiO 2 composition exhibited superior insulating properties. The measured dielectric constant and dissipation factor at 1 MHz were 9 and 0.015, respectively, for films annealed at 900 °C. The interface trap density was 2.5×10 11 cm −2 eV −1, and flatband voltage was −0.38 V. A charge storage density of 22.8 fC/μm 2 was obtained at an applied electric field of 3 MV/cm. The leakage current density was lower than 4×10 −9 A/cm 2 up to an applied electric field of 6 MV/cm. 相似文献
5.
In this paper, green and red up-conversion emissions of Er 3+–Yb 3+ co-doped TiO 2 nanocrystals were reported. The phase structure, particle size and optical properties of Er 3+–Yb 3+ co-doped TiO 2 nanocrystals samples were characterized by using X-ray diffraction (XRD), transmission electron microscopy (TEM), UV–vis–NIR absorption spectra and photoluminescence (PL) spectra. Green and red up-conversion emissions in the range of 520–570 nm ( 2H 11/2, 4S 3/2→ 4I 15/2) and 640–690 nm ( 4F 9/2→ 4I 15/2) were observed for the Er 3+–Yb 3+ co-doped TiO 2 nanocrystals. The visible up-conversion mechanism and temperature dependence of up-conversion emission for Er 3+ in TiO 2 nanocrystals were discussed in detail. 相似文献
6.
SrTiO_3(STO) and TiO_2 are insulating materials with large dielectric constants and opposite signs of the quadratic coefficient of voltage(α). Insertion of a TiO_2 thin film between STO layers increases the linearity of the capacitance in response to an applied voltage, to meet the increasing demand of large-capacitance-density dynamic random access memory capacitors. Both STO and TiO_2 suffer from the problem of high leakage current owing to their almost equivalent and low bandgap energies. To overcome this, the thickness of the thin TiO_2 film sandwiched between the STO films was varied. A magnetron sputtering system equipped with radio frequency and direct current power supply was employed for depositing the thin films. Ti N was deposited as the top and bottom metal electrodes to form a metal–insulator metal(MIM) structure,which exhibited a very large linear capacitance density of 21 fF/um~2 that decreased by increasing the thickness of the TiO_2 film. The leakage current decreased with an increase in the thickness of TiO_2, and for a 27-nm-thick film, the measured leakage current was 2.0 × 10~(-10) A. X-ray diffraction and Raman spectroscopy revealed that Ti N, STO, and TiO_2 films are crystalline and TiO_2 has a dominant anatese phase structure. 相似文献
7.
Na 5PV 2Mo 10O 40 supported on nanoporous anatase TiO 2 particles, TiO 2–PVMo, was used as an efficient photocatalyst for photocatalytic degradation of different dyes by visible light using oxygen as oxidant. This catalyst showed a good catalytic activity in the sonocatalytic and sonophotocatalytic decomposition of different dyes in aqueous solutions. The TiO 2–PVMo composite showed higher photocatalytic and sonocatalytic activity than pure polyoxometalate or pure TiO 2. 相似文献
8.
A series of thin films of copper phthalocyanine derivatives with bromine and alkoxyl substituents [CuPc(OC 8H 17) 4Br m, m=0,1,2,4] were prepared on single-crystal silicon substrates by spin coating. The ellipsometric spectra of the films have been studied on a rotating analyzer–polarizer type of scanning ellipsometer. The optical, dielectric constants and absorption coefficients of the films in 500–800 nm wavelength region were obtained. The results show that the complex refractive index, dielectric constants and absorption coefficient of these thin films are influenced regularly by bromine substituent on conjugated macrocycle. It was found that there are approximately linear relationships between the resonance absorption wavelengths of the films and the average number of bromine atoms substituted on the phthalocyanine ring. 相似文献
9.
We investigated the effects of using different thicknesses of pure and vanadium-doped thin films of TiO_2 as the electron transport layer in the inverted configuration of organic photovoltaic cells based on poly(3-hexylthiophene) P3HT:[6-6] phenyl-(6) butyric acid methyl ester(PCBM). 1% vanadium-doped TiO_2nanoparticles were synthesized via the solvothermal method. Crystalline structure, morphology, and optical properties of pure and vanadium-doped TiO_2 thin films were studied by different techniques such as x-ray diffraction, scanning electron microscopy, transmittance electron microscopy, and UV–visible transmission spectrum. The doctor blade method which is compatible with roll-2-roll printing was used for deposition of pure and vanadium-doped TiO_2 thin films with thicknesses of 30 nm and 60 nm. The final results revealed that the best thickness of TiO_2 thin films for our fabricated cells was 30 nm. The cell with vanadium-doped TiO_2 thin film showed slightly higher power conversion efficiency and great J_(sc) of 10.7 mA/cm~2 compared with its pure counterpart. In the cells using 60 nm pure and vanadium-doped TiO_2 layers, the cell using the doped layer showed much higher efficiency. It is remarkable that the external quantum efficiency of vanadium-doped TiO_2 thin film was better in all wavelengths. 相似文献
10.
The results of the femtosecond time-resolved optical Kerr at 820 nm in GeS 2–In 2S 3 chalcogenide glasses indicate that the response time in GeS 2–In 2S 3 glasses is subpicosecond, which is predominantly due to the distortion of the electron cloud. The value of χ(3) in 0.95GeS 2–0.05In 2S 3 glass is also as large as 2.7 × 10 −13 esu, and it reduces with the addition of In 2S 3, which may be ascribed to the microstructure evolution of GeS 2–In 2S 3 glasses. It is deduced that the intrinsic [Ge(In)S 4] tetrahedral structure units that possess the high hyperpolarizability may do great contribution to the enhancement of third-order optical nonlinearity while [S 3Ge–GeS 3] ethane-like molecular units make no considerable contribution to that in femtosecond time scale. These GeS 2–In 2S 3 and GeS 2–In 2S 3-based chalcogenide glasses would be expected to be the promising materials for all-optical switching devices. 相似文献
11.
TiO 2-doped WO 3 thin films were deposited onto fluorine-doped tin oxide coated conducting glass substrates using spray pyrolysis technique at 525 °C. The volume percentage of TiO 2 dopant was varied from 13% to 38%. The thin film samples were transparent, uniform and strongly adherent to the substrates. Electrochromical properties of TiO 2-doped WO 3 thin films were studied with the help of cyclic voltammetry (CV), chronoamperometry (CA) and chronocoulometry (CC) techniques. It has been found that TiO 2 doping in WO 3 enhances its electrochromic performance. Colouration efficiency becomes almost double and samples exhibit increasingly high reversibility with TiO 2 doping concentrations, in the studied range. 相似文献
12.
Optical properties of SnO 2 thin films in the 4–60 eV energy range are determined by reflection electron energy loss spectroscopy. Bulk and surface electron loss functions, real and imaginary parts of the dielectric function, refraction index, extinction and absorption coefficients are obtained from the analysis of the electron energy loss spectra. Electronic transitions are identified through the interpretation of the optical data. The samples (250–500 nm thick) were produced by ion beam-induced chemical vapor deposition. It is found that the compacity of the SnO 2 thin films affects their optical properties and therefore the relative intensity of the observed electronic transitions. The advantages of this method to determine optical properties of thin films are discussed. Inelastic mean free paths (6.2, 17 and 41 Å for electrons traveling in SnO 2 with kinetic energies of 300, 800 and 2000 eV, respectively) are obtained from the corresponding inelastic electron scattering cross-sections. 相似文献
13.
By means of X-ray diffraction, BET nitrogen adsorption, UV-Vis-NIR transmission spectroscopy, transmission electron microscope, scanning electron microscope, X-ray photoelectron spectroscopy and photodegradation of methylene blue, effects of Ag doping on the microstructure and photocatalytic activity of TiO 2 films prepared by sol–gel method were studied. It is found that with a suitable amount (2–4 mol%), the Ag dopant increases the photocatalytic activity of TiO 2 films. The mechanism can be attributed to that (1) anatase grain sizes decrease with Ag doping and the specific surface areas of doped TiO 2 films increase, the charge transfer in TiO 2 films is promoted; (2) by enhancing the electron–hole pairs separation and inhibiting their recombination, the Ag dopant enhances the charge pair separation efficiency for doped TiO 2 films. 相似文献
14.
Atomic layer deposition of hafnium dioxide (HfO 2) on silicon substrates was studied. It was revealed that due to low adsorption probability of HfCl 4 on silicon substrates at higher temperatures (450–600 °C) the growth was non-uniform and markedly hindered in the initial stage of the HfCl 4–H 2O process. In the HfI 4–H 2O and HfI 4–O 2 processes, uniform growth with acceptable rate was obtained from the beginning of deposition. As a result, the HfI 4–H 2O and HfI 4–O 2 processes allowed deposition of smoother, more homogeneous and denser films than the HfCl 4–H 2O process did. The crystal structure developed, however, faster at the beginning of the HfCl 4–H 2O process. 相似文献
15.
制备Cu掺杂的纳米Sn O2/Ti O2溶胶,采用旋涂法在载玻片上镀膜,经干燥、煅烧制得Cu掺杂的Sn O2/Ti O2薄膜,通过对比实验探讨掺杂比例、条件、复合形式等对结构和性能的影响。采用XRD、SEM、EDS、UVVis等测试手段对样品进行表征,并以甲基橙为探针考察了其光催化降解性能。XRD测试结果显示薄膜的晶型为锐钛矿型,结晶度较高。SEM谱图显示薄膜表面无明显开裂,粒子分布均匀,粒径约为20 nm。EDS测试结果表明薄膜材料中含有Cu元素,谱形一致。UV-Vis吸收光谱表明Cu掺杂以及Sn O2/Ti O2的复合使得在近紫外区的光吸收比纯Ti O2明显增强。光催化实验表明Cu掺杂后使得Sn O2/Ti O2复合薄膜对甲基橙的光催化降解效率进一步提高,Sn O2/Ti O2复合薄膜的光催化活性在10%Cu掺杂时达到最高。 相似文献
16.
采用脉冲激光沉积法 (PLD), 以石英玻璃为衬底制备了钽掺杂TiO 2薄膜并研究了薄膜样品的光电性质. 沉积氧气分气压从0.3 Pa变化到0.7 Pa时薄膜样品的帯隙变化范围是3.26 eV到3.49 eV. 通过测量电阻率随温度的变化关系确定了薄膜内部的主要导电机理. 在150 K到210 K温度范围内, 热激发导电机理是主要的导电机理; 而在10 K到150 K范围内; 电导率随温度的变化复合Mott的多级变程跳跃模型 (VRH); 在210 K到300 K范围内, 电阻率和exp( b/T) 1/2呈正比关系.
关键词:
2')" href="#">Ta掺杂TiO 2
脉冲激光沉积法
薄膜
导电机理 相似文献
17.
An inverted structure of polymer solar cells based on Poly(3-hexylthiophene)(P3HT):[6-6] Phenyl-(6) butyric acid methyl ester(PCBM) with using thin films of TiO_2 nanotubes and nanoparticles as an efficient cathode buffer layer is developed. A total of three cells employing TiO_2 thin films with different thickness values are fabricated. Two cells use layers of TiO_2 nanotubes prepared via self-organized electrochemical-anodizing leading to thickness values of 203 and 423.7 nm, while the other cell uses only a simple sol–gel synthesized TiO_2 thin film of nanoparticles with a thickness of 100 nm as electron transport layer. Experimental results demonstrate that TiO_2 nanotubes with these thickness values are inefficient as the power conversion efficiency of the cell using 100-nm TiO_2 thin film is 1.55%, which is more than the best power conversion efficiency of other cells. This can be a result of the weakness of the electrochemical anodizing method to grow nanotubes with lower thickness values. In fact as the TiO_2 nanotubes grow in length the series resistance(Rs) between the active polymer layer and electron transport layer increases, meanwhile the fill factor of cells falls dramatically which finally downgrades the power conversion efficiency of the cells as the fill factor falls. 相似文献
18.
采用旋涂法制备了多层聚乙二醇/二氧化钛(PEG/TiO 2)一维光子晶体膜,通过控制旋涂时间、旋涂速度和聚乙二醇溶液质量浓度,制备出具有不同光子禁带的PEG/TiO 2一维光子晶体膜。制备的PEG/TiO 2膜对有机溶剂二甲亚砜(DMSO)和强碱溶液有双重响应。 相似文献
19.
Ba 0.65Sr 0.35TiO 3 (BST) thin films were deposited by RF sputtering with a very thin Ba 0.65Sr 0.35RuO 3 (BSR) seeding-layer on Pt/Ti/SiO 2/Si substrate. The crystallization of BST thin films and the surface morphology of BSR seeding-layer were characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM), respectively. XRD patterns show that the BSR seeding-layer affected the orientation of BST thin film, which is highly a-axis textured. It was also found that the BSR seeding-layer had a marked influence on the dielectric properties of BST thin films. Comparing with BST thin films directly deposited on Pt electrode, the dielectric relaxation can be suppressed and dielectric constant increased due to a possible reduction of interface oxygen vacancies at BST/BSR interface. Moreover, J– V measurement indicates that the leakage current density of BST thin films on BSR seeding-layer were greatly reduced compared with that of BST thin films directly on Pt electrodes. The pyroelectric coefficient of BST thin films with BSR seeding-layer is 7.57 × 10 −7 C cm −2 K −1 at 6 V/μm at room temperature (RT). Our results reveal that high pyroelectric property of BST thin film could be achievable using BSR seeding-layer as a special buffer. 相似文献
20.
采用匀胶法制备了厚度在微米量级的 Si/[TiO 2/Al 2O 3] 2TiO 2和Si/[TiO 2/MgO] 2/TiO 2 多层介质膜反射镜. 采用太赫兹(THz)时域透射光谱系统获得了多层膜的时域透射谱. 用传输矩阵法模拟了Si/[TiO 2/Al 2O 3] 2TiO 2 和Si/[TiO 2/MgO] 2/TiO 2两种分布式布拉格反射镜 (DBR)的反射相移和相位穿透深度等光学特性. 设计了两种结构为 DBR/LT-GaAs/DBR的对称THz光学微腔结构并模拟了腔结构的辐射光谱. 结果表明:通过引入谐振腔, 两种DBR组成的微腔器件在谐振波长处的强度分别提高了19和14倍. 其中Si/[TiO 2/Al 2O 3] 2TiO 2/LT-GaAs (12 μm)/ [TiO 2/Al 2O 3] 2TiO 2腔的辐射光谱存在两个峰, 分别位于208和248 μm, 并分析了出现两个谐振峰的原因. 探讨了通过引入介质谐振腔实现对THz源的辐射特性进行调控的可行性.
关键词:
分布式布拉格反射镜
光子晶体
穿透深度
太赫兹微腔 相似文献
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