SmS phase transition in thin films prepared by reactive evaporation

Preparation and analysis of thin films containing samarium sulfide (SmS) is presented along with a review of relevant SmS properties. Films were deposited onto unheated substrates by the reactive evaporation of samarium in a backpressure of hydrogen sulfide. This technique yields films that contain significant quantities of impurities; however high-quality SmS crystals are also formed. A phase transition in the SmS crystals was observed both by spectrophotometry and x-ray diffraction. The film optical properties can be modeled with an effective medium calculation. The predicted spectra successfully reproduce the observed qualitative features over a wide range of wavelengths.     

Electrochromic and photoluminescence properties of cobalt oxide thin films prepared by spray pyrolysis

Cobalt oxide thin films were prepared by a facile spray pyrolysis technique, using a perfume atomizer with an aqueous solution of hydrated cobalt chloride salt with a molar concentration of 0.025?M as a source of cobalt. The films were deposited onto glass substrates at temperature of 350?°C. The structural, morphological, and electrochromic properties of the obtained films were studied. It was found from X-ray diffraction analysis that the films were polycrystalline in nature with spinel-type cubic structure and preferred orientation along [111] direction. The Scanning Electron Microscopy images revealed a porous structure with the average grain size around 200?nm. The cyclic voltammetry measurements revealed that Cobalt oxide thin film is an anodically coloring electrochromic material with a transmittance variation in the visible range of 31%, and a fast response time (about 2?seconds) and a good cycling stability. These electrochromic performances make cobalt oxide thin film an attractive material for using as an anodic electrochromic material in smart windows devices. The photoluminescence spectra exhibited a strong emission in the visible region confirming the good crystallinity properties of Co₃O₄ thin films.     

CEMS studies of Sn−O thin films prepared by thermal evaporation

Thermal evaporated thin Sn?O films subjected to annealing treatments in air in the range 473–1173 K and in Ar in the range 473–773 K followed by annealings in air up to 1373 K were studied by CEMS (Conversion Electron Mössbauer Spectroscopy). Complementary Mössbauer and X-ray measurements were also performed on SnO powder that underwent the same series of annealings. The presence of the intermediate oxide Sn₃O₄ was detected. A temptative hyperfine characterization for the Sn²⁺ site in Sn₃O₄ is given.     

热蒸发与离子束溅射制备LaF3薄膜的光学特性

研究了钼舟热蒸发工艺和离子束溅射方法制备的单层LaF₃薄膜的特性。首先,采用分光光度计测量了LaF₃薄膜的透射率和反射率光谱,使用不同模型拟合得出薄膜的折射率和消光系数。然后,采用应力仪测量了加热和降温过程中LaF₃薄膜的应力-温度曲线。最后,采用X射线衍射仪测试了薄膜的晶体结构。实验结果表明,热蒸发制备的LaF₃（RH LaF₃）存在折射率的不均匀性,在193 nm,其折射率和消光系数分别为1.687和5×10^-4,而离子束溅射制备的LaF₃（IBS LaF₃）折射率和消光系数分别为1.714和9×10^-4。两种薄膜表现出相反的应力状态,RH LaF₃薄膜具有张应力,而IBS LaF₃具有压应力,退火之后其压应力减小。热蒸发制备的MgF₂/LaF₃减反膜在193 nm透过率为99.4%,反射率为0.04%,离子束溅射制备的AlF₃/LaF₃减反膜透过率为99.2%,反射率为0.1%。     

Electrochromic properties of spray-deposited niobium oxide thin films

Niobium oxide thin films were deposited on the glass and fluorine-doped tin oxide (FTO)-coated glass substrates using simple and inexpensive spray pyrolysis technique. Various preparative parameters like nozzle to substrate distance, spray rate, concentration of sprayed solution were optimized to obtain good substrate-adherent and transparent films. Morphological and structural characterizations of the films were carried out using scanning electron microscopy and X-ray diffraction techniques. Electrochemical characterization of the niobium oxide thin films was carried out using cyclic-voltammetry, chronoamperometry and chronocoulometry.     

Optical properties of rubrene thin film prepared by thermal evaporation

Rubrene thin films are deposited on quartz substrates and silver nanoparticles(Ag NPs) films by the thermal evaporation technique. The optical properties of rubrene thin film are investigated in a spectral range of 190 nm–1600 nm. The analysis of the absorption coefficient(α) reveals direct allowed transition with a corresponding energy of 2.24 e V. The photoluminescence(PL) peak of the rubrene thin film is observed to be at 563 nm(2.21 e V). With the use of Ag NPs which are fabricated by radio-frequency(RF) magnetron sputtering on the quartz, the PL intensity is 8.5 times that of as-deposited rubrene thin film. It is attributed to the fact that the surface plasmon enhances the photoluminescence.     

Thermal stability of Ag films in air prepared by thermal evaporation

The thermal stability of silver films in air has been studied. Pure Ag films, 250 nm in thickness, were prepared on glass substrates by thermal evaporation process, and subsequently annealed in air for 1 h at temperatures between 200 and 400 °C. The structure and morphology of the samples were investigated by X-ray diffraction, Raman spectra and atomic force microscopy. It is found that the crystallization enhances for the annealed films, and film surface becomes oxidized when annealing temperature is higher than 350 °C. The electrical and optical properties of the films were studied by van der Pauw method and spectrophotometer, respectively. Reflectance drops sharply as Ag films are annealed at temperatures above 250 °C. Film annealed at 250 °C has the maximum surface roughness and the minimum reflectance at 600 nm optical wavelength. Film annealed at 200 °C has the minimum resistivity, and resistivity increases with the increasing of the annealing temperature when temperature is above 200 °C. The results show that both oxidization on film surface and agglomeration of silver film result in infinite of electrical resistivity as the annealing temperature is above 350 °C.     

Synthesis and characterization of ZnO thin films by thermal evaporation

ZnO thin films have been successfully synthesized by thermal evaporation of pure zinc at 900 °C under the flow of different percentages of argon and oxygen gases. The films were characterized by X-ray diffraction (XRD), variable pressure scanning electron microscopy (VPSEM), energy dispersive X-ray spectroscopy (EDS) and UV–vis spectroscopy. The aim of this paper is to study the influence of the oxygen percentage on the structural and morphological properties of the ZnO films. VPSEM results show that very thick needle structures were produced at high oxygen percentages. EDS results revealed that only Zn and O are present in the sample, indicating a composition of pure ZnO. XRD results showed that the ZnO synthesized under different quantities of oxygen were crystalline with the hexagonal wurtzite structure. UV–vis spectroscopy results indicated that the optical band gap energies from the transmission spectrum are between 3.62 and 3.69 eV for ZnO thin films.     

Electrochromic properties of nano-structured nickel oxide thin film prepared by spray pyrolysis method

In this study, we present a simple method to improve the electrochromic properties of a nickel oxide thin film. The method involves a three-step process—(a) conducting indium tin oxide (ITO) nano-particles were first sprayed onto a conducting substrate to form a porous nano-structured ITO layer, (b) nickel oxide film was then deposited onto the nano-structured ITO layer by a spray pyrolysis technique, and (c) the substrate, ITO nano-particles layer and nickel oxide film were annealed at high temperature of 300 °C to improve adhesion of these three layers. The microstructure of the resulting electrochromic cell was investigated using scanning electron microscopy. It is evident that the nickel oxide film covers the surface of the ITO nano-particle layer and forms a nano-structured nickel oxide (NSNO) film. The switching time and contrast were characterized by Autolab PGSTAT12 potentiostat and Jasco V-570 spectrophotometer. The results suggest that the transmittance contrast and switching time of NSNO are slightly superior to those of a conventional nickel oxide (CNO) film. However, the cycling durability of NSNO can be much better than that of CNO.     

快速热处理制备相变氧化钒薄膜及其特性研究

采用直流对靶磁控溅射在Si<100>基底上沉积金属V薄膜, 然后分别在纯氧气环境和纯氮气环境下进行快速热处理制备具有 金属-半导体相变特性的氧化钒(VO_X)薄膜, 热处理条件分别为纯氧气环境下430℃/40 s, 450℃/40 s, 470℃/40 s, 450℃/30 s, 450℃/50 s, 纯氮气环境下500℃/15 s. 用X射线衍射仪、X射线光电子能谱、原子力显微镜 和扫描电子显微镜对薄膜的结晶结构、钒的价态和组分以及微观形貌进行分析. 利用四探针薄膜电阻测量方法和THz时域频谱技术分析薄膜的电学特性和光学特性. 结果表明: 金属V薄膜经过纯氧气环境450℃/40 s快速热处理 后形成了具有低相变特性的VO_X薄膜, 升温前后薄膜方块电阻变化幅度达到两个数量级, THz透射强度变化幅度较小. 为了提高薄膜的相变特性, 对制备的VO_X薄膜采用纯氮气环境500℃/15 s快速热处理, 薄膜的相变特性有了明显提升, 相变前后方块电阻变化达到3个数量级, THz透射强度变化达到56.33%.     

Gas sensing properties of zinc oxide nanostructures prepared by thermal evaporation

Progress has been achieved in the synthesis, structural characterization and physical properties investigation of nanostructures. We have focused our attention on zinc oxide nanostructures. We report on the growth of ZnO nanostructures using vapour phase technique. We have synthesized, depending on the growth conditions, different nanostructures such as wires and combs of zinc oxide. ZnO nanowires electrical properties have been characterised in presence of different gases, the results highlight remarkable response to acetone and ethanol with detection limits lower than 1 ppm. PACS 73.63.Bd; 74.78.Na     

Aluminium oxide thin films prepared by plasma-enhanced chemical vapour deposition

Thin films of aluminium oxide have been deposited on glass, quartz, Si(100), steel, nickel, and aluminium by plasma-enhanced chemical vapour deposition (PECVD) using aluminium acetylacetonate (Al(acac)₃) as precursor. The deposits are hard (up to 2370 HK) and show good adherence to the substrates. The influence of various experimental parameters on deposition rate, film composition and hardness has been studied. The bias turned out to be the most effective parameter.On leave from Beijing Solar Energy Research Institute, Beijing, P.R. China     

Development of porous metal oxide thin films by co-evaporation

This paper focuses on the development of mixed metal oxide thin films and physical characterization of the films. The films were produced by co-evaporation of titanium oxide and tungsten oxide powders. This allowed the development of titanium oxide-tungsten oxide films as analyzed using XPS. Examination in the SEM and AFM showed that the films were nanoporous with the pore size and pore orientation varying as a function of the deposition angle. UV-vis spectra of the films show an increase of transmittance with increasing deposition angle which is attributed to the structure and porosity of the films. Raman analysis indicated that the as-deposited films have broad and weak Raman characteristics, attributed to the nanocrystal nature of the films and the presence of defects, and the peak broadening deceases after annealing the film, as expected.     

Electrochromic properties of nanocrystalline WO3 thin films grown on flexible substrates by plasma-assisted evaporation technique

Thin films of Tungsten trioxide (WO₃) were deposited on ITO-coated flexible Kapton substrates by plasma-assisted activated reactive evaporation (ARE) technique. The influence of growth and microstructure on optoelectrochromic properties of WO₃ thin films was studied. The nanocrystalline WO₃ films grown at substrate temperature of 250°C were composed of vertically elongated cone-shaped grains of size 65 nm with relative density of 0.71. These WO₃ films demonstrated higher optical transmittance of 85% in the visible region with estimated optical band gap of 3.39 eV and exhibited better optical modulation of 66% and coloration efficiency of 52.8 cm²/C at the wavelength of 550 nm.     

Characterization of AgInS2 thin films prepared by vacuum evaporation

We characterized AgInS₂ thin films prepared by vacuum evaporation. In the case of thin films annealed at 400 °C, diffraction peaks were observed only for the chalcopyrite AgInS₂ phase. The chemical composition of the thin films annealed at 400 °C was 26.5 at% Ag, 23.8 at% In, and 49.7 at% S. PL spectra of the AgInS₂ thin films at 10.7 K showed peaks at 1.70, 1.80, and 1.83 eV. The PL peak at1.80 eV was attributed to sulfur deficiency.     

基底温度对电子束蒸发制备氧化铝薄膜的影响

为了考察基底温度对氧化铝薄膜折射率以及沉积厚度的影响情况,在不同基底温度环境下,通过离子辅助电子束蒸发方式,在玻璃基底上制备了同一Tooling因子条件下所监测到相同厚度的Al2O3薄膜,利用分光光度计测量光谱透过率,依据光学薄膜相关理论,计算了基底温度在25℃～300℃范围内获得的膜层实际物理厚度为275.611 nm～348.447 nm,以及膜层折射率的变化。通过对实验结果的数值计算和曲线模拟,给出了基底温度对于薄膜的折射率和实际厚度的影响情况。     

Optical properties of TiO2-MnO2 thin films prepared by electron-beam evaporation

The optical constants and thickness of TiO₂-MnO₂ films (with MnO₂ concentration of 0, 1, and 5%) prepared by electron-beam evaporation are determined. A considerable dependence of the optical properties of thin TiO₂ films on the manganese concentration is observed. It is found that thin films are indirect gap semiconductors with gap width E _g = 3.43 eV (TiO₂), 2.89 eV (TiO₂-MnO₂ (1%)), and 2.73 eV (TiO₂-MnO₂ (5%)).     

热沉积法制备纳米二硫化钼薄膜及其光电特性研究

以M oS2粉末为原料,以氩气为携载气体,在400～600℃温度范围内利用热蒸发方法在硅衬底表面制备了不同厚度的M oS2薄膜．利用X射线衍射和扫描电子显微镜分析了M oS2薄膜的结构和表面形貌,发现M oS2薄膜由多晶M oS2粒子组成,颗粒均匀,平均纳米颗粒尺寸约为60 nm ．利用紫外可见光光谱仪测量了其吸收特性,发现样品在720 nm附近有很强的吸收．应用霍尔效应和伏安法研究了M oS2/Si样品的接触特性和电子的运输特性,发现该异质结具有良好的整流特性,即正向电压下电流随电压呈指数增长,而在反向偏压下漏电流很小,电子迁移率可达到6．730×102 cm2/（V · s）．实验结果表明MoS2薄膜具有良好的电学特性,可用来制备晶体管和集成电路等器件．     

Preparation and characterization of ZnO thin films prepared by thermal oxidation of evaporated Zn thin films

In this paper, the experimental results regarding some structural, electrical and optical properties of ZnO thin films prepared by thermal oxidation of metallic Zn thin films are presented.Zn thin films (d=200–400 nm) were deposited by thermal evaporation under vacuum, onto unheated glass substrates, using the quasi-closed volume technique. In order to obtain ZnO films, zinc-coated glass substrates were isochronally heated in air in the 300–660 K temperature range, for thermal oxidation.X-ray diffraction (XRD) studies revealed that the ZnO films obtained present a randomly oriented hexagonal nanocrystalline structure. Depending on the heating temperature of the Zn films, the optical transmittance of the ZnO films in the visible wavelength range varied from 85% to 95%. The optical band gap of the ZnO films was found to be about 3.2 eV. By in situ studying of the temperature dependence of the electrical conductivity during the oxidation process, the value of about 2×10⁻² Ω⁻¹ m⁻¹ was found for the conductivity of completely oxidized ZnO films.     

Transparent conductive oxide thin films of CdTe-doped indium oxide prepared by pulsed-laser deposition

Transparent conducting oxide thin film CdTe-doped indium oxide (In₂O₃) has been grown by pulsed-laser deposition from a target of CdTe powder embedded in metallic indium. The electro-optical and structural properties were investigated as a function of oxygen partial pressure (PO₂) and substrate temperature (T_s). A film deposited at T_s=420 °C and PO₂=4 Pa shows the minimum resistivity 7.5×10⁻⁴ Ω cm, its optical transmission is 83% and the carrier concentration was 8.9×10²⁰ cm³. The optical band gap and the average roughness of that sample were 3.6 eV and 6.45 Å, respectively. X-ray diffraction studies indicated that the films were polycrystalline. This material is a good candidate for being used as transparent conductor in the CdTe–CdS solar cell.