真空还原制备的VO2热致相变薄膜Raman光谱和红外光谱研究

报道了利用真空还原制备的VO2薄膜的红外透射光谱和Raman光谱,并进行370－900nm波段的光透射测试以及900nm波长的热滞回线特性测试,表明所制备VO2薄膜具有优良的热致相变光学特性,结晶状态不同的薄膜其Raman谱位置有明显改变,室温时的红外光谱表现出较好的红外振动特性。讨论了薄膜结晶状态对Raman位移的影响以及VO2薄膜的红外光谱。     

电致变色纳米氧化镍薄膜的溶胶-凝胶法制备与表征

以无水氯化镍、乙醇为前驱液,加入适量的丁醇和柠檬酸为稳定剂,通过回流、水解得到稳定的溶胶;采用浸渍-提拉的方法在ITO导电玻璃上形成均匀的膜层;分析了溶胶制备中加水量的影响;研究了热处理温度对制备膜层的结构、光透过率的影响;对经过不同处理的膜层进行X射线衍射、透射电子显微镜、扫描电子显微镜、热重分析等研究表明:在空气中加热到350℃、保温30min薄膜分解为稳定的具有立方结构的NiO纳米晶;以氢氧化钾水溶液为电解质的循环伏安、电致变色实验结果表明制备的纳米氧化镍薄膜具有良好的电致变色特性.     

Cr掺杂ZnO薄膜晶体结构及光学性能的研究

采用磁控溅射法在载玻片上制备了不同Cr掺杂浓度的ZnO薄膜,并对其紫外发光性能做了初步研究.XRD结果表明,所制备的样品具有纤锌矿结构,呈c轴择优取向生长;透射谱表明,改变Cr掺杂浓度可以使ZnO薄膜的吸收边向短波方向移动,并且薄膜的禁带宽度连续可调;光致发光(PL)谱表明,所有样品的PL谱由发光中心位于370nm的紫外发光峰组成,且该峰的峰位蓝移,与吸收边缘移动的结果吻合.2.0%(原子分数,下同)的Cr掺杂可以提高ZnO的紫外发光强度,而过量的Cr掺杂反而会降低其紫外发光强度.     

Band gap engineering in PbSe thin films from near-infrared to visible region by photochemical deposition method

Lead selenide (PbSe) thin films have been synthesized by the established photochemical deposition technique using lead nitrate and lead acetate as sources for the metal ions and sodium seleno sulphate as the selenium source along with triethanolamine, ammonia and hydrazine hydrate as complexing agents. A comprehensive study of the effect of substrate materials on physical properties of as deposited PbSe thin films is reported in this work. Two substrates were used in this investigation, namely soda lime glass slides and gold coin corning glass slides. The solution is irradiated with UV light and the photochemical reactions in the aqueous solution resulted in highly adherent metallic thin films. X-ray diffraction (XRD), scanning electron microscopy, optical and electrical measurement techniques were used for film characterization. The XRD analysis confirmed that all films were cubic, regardless of the cationic precursors and substrates used. The scanning electron microscope micrographs showed variations in morphology. The optical studies revealed that the films have good absorption in the visible region. The remarkable success of our effort was that we have been able to modify optical band gap of PbSe thin films over a wide spectral range by a cost effective route. The band gaps estimated from the transmission spectra were in the range 1.32–1.40 eV for films deposited on soda lime glass substrates and 1.46–1.55 eV for corning glass substrates. The room temperature conductivity of the PbSe films were in the range of 3.71 × 10^?7–513 × 10^?7 (Ω cm)^?1. The as deposited PbSe thin films with low transmittance in the visible region coupled with an appreciable reflectance in infrared region were found to satisfy the basic requirements for solar control coatings for window glazing applications in warm climates. Through this work we established that irrespective of metal salts, soda lime glass substrate was superior to corning glass substrate.     

阴极电沉积高c轴取向ZnO薄膜及其光学性能的研究

以硝酸锌水溶液为电沉积液,采用两步法电沉积技术在ITO导电玻璃上电沉积出透明致密的ZnO薄膜.利用电势-pH计算和循环伏安实验得到适宜的溶液pH值和电沉积电势,采用X射线衍射、热重-差热、光致发光谱和透射光谱对ZnO薄膜的结构、组成和光学性能进行了表征.结果表明,所制备的ZnO薄膜在c轴方向上具有高度的择优取向性质,平均粒径为纳米级,性能稳定、单一,发光性能良好,可见光区透射率较高.此类产品在太阳能电池和光电子器件等光学材料方面具有很高的应用价值.     

Influence of In doping on electro-optical properties of ZnO films

Thin metallic films of Zn and In/Zn were deposited onto glass substrates by thermal evaporation under vacuum. The metallic films were submitted to a thermal oxidation in air, at 623 K, for different oxidation times (30–90 min), in order to be oxidized. Structural and morphological analyses (X-ray diffraction, transmission electron microscopy and scanning electron microscopy) revealed that the obtained undoped and In-doped ZnO thin films possess a polycrystalline structure. Transmission spectra were recorded in spectral domain from 280 to 1400 nm. The influence of In doping and oxidation parameters as well, on the optical parameters (transmittance, optical bandgap, Urbach energy) were analysed. It was clearly evidenced that by In doping, the optical properties of ZnO films were improved. The temperature dependence of electrical conductivity was studied using surface-type cells with Ag electrodes. The obtained results indicate that In-doped ZnO films exhibit an enhancement of electrical conductivity with few orders of magnitude when compared with non-doped ones.     

前驱体浓度对超声雾化热解法制备ZnO薄膜性能的影响

采用超声雾化技术,以醋酸锌水溶液为前驱体溶液,在加热的玻璃衬底上制备得到ZnO薄膜.研究了不同前驱体溶液浓度和不同加热温度条件下制得的ZnO薄膜的微观结构和光学性能.测试结果表明,ZnO薄膜为六角纤锌矿结构,在合适的条件下可以制备出沿(002)晶面取向生长的样品,具有优良的均匀性和致密性.同时在可见光区也表现出80%以上的高透过率.     

Oligoethylene-glycol-functionalized polyoxythiophenes for cell engineering: syntheses, characterizations, and cell compatibilities

A series of methyl- or benzyl-capped oligoethylene glycol functionalized 2,5-dibromo-3-oxythiophenes are synthesized and successfully polymerized by either Grignard metathesis (GRIM) polymerization or reductive coupling polymerization to yield the corresponding polymers in reasonable yields and molecular weights with narrow molecular weight distribution. These synthesized polyoxythiophenes exhibit high electroactivity and stability in aqueous solution when a potential is applied. Polyoxythiophenes from different polymerization approaches display different colors after purification and spectroelectrochemical studies confirm that the difference of color is from the difference of doping state. Little cytotoxicity is observed for the polymers by in vitro cell compatibility assay. NIH3T3 fibroblast cells are well attached and proliferate on spin-coated films. These results indicate that oligoethylene-glycol-functionalized polyoxythiophenes are promising candidates as conducting biomatierals for biomedical and bioengineering applications.     

Optical characterization of transparent nickel oxide films deposited by DC current reactive sputtering

In this paper, we characterize high transparency p-type semiconducting NiO thin films deposited by Direct Current Reactive Magnetron Sputtering from a pure Ni target in a mixture of oxygen and argon gases on Corning glass/SnO₂:F substrates at different oxygen contents ranging from 0% at 30%. The influence of the O₂/Ar ratio and thickness on transmittance has been examined using ultraviolet-visible spectroscopy. The results show that whatever the oxygen proportion into the discharge, the nickel oxide films exhibit a polycrystalline structure. At low oxygen content, the preferential orientation is (111), for stoichiometric films the XRD diagram is powder-like whereas the preferential orientation is (200) for higher oxygen content. For low and high oxygen content, the transmittance is low. Thanks to plasma method and its ability to tune the oxygen content in the discharge and therefore the film composition, we have been able to explore carefully the intermediate zone and obtain transparent films. The optical absorption coefficient α has been calculated from the transmittance and the variation of (αhν)² versus the photon energy (hν) for nickel oxide is presented. The optical band gap energy has been evaluated and varies from 3.2 to 3.8 eV.     

Ellipsometry on sputter-deposited tin oxide films: optical constants versus stoichiometry, hydrogen content, and amount of electrochemically intercalated lithium

Tin oxide thin films were deposited by reactive radio-frequency magnetron sputtering onto In(2)O(3):Sn-coated and bare glass substrates. Optical constants in the 3002500-nm wavelength range were determined by a combination of variable-angle spectroscopic ellipsometry and spectrophotometric transmittance measurements. Surface roughness was modeled from optical measurements and compared with atomic-force microscopy. The two techniques gave consistent results. The fit between experimental optical data and model results could be significantly improved when it was assumed that the refractive index of the Sn oxide varied across the film thickness. Varying the oxygen partial pressure during deposition made it possible to obtain films whose complex refractive index changed at the transition from SnO to SnO(2). An addition of hydrogen gas during sputtering led to lower optical constants in the full spectral range in connection with a blueshift of the bandgap. Electrochemical intercalation of lithium ions into the Sn oxide films raised their refractive index and enhanced their refractive-index gradient.     

CHEMICALLY DEPOSITED ZnS-NiS-CuS OPTICAL FILTERS WITH WIDE RANGE SOLAR CONTROL CHARACTERISTICS

Successive chemical bath depositions of ZnS (substrate film) with NiS (neutral density absorber film) and CuS (u.v. and i.r. absorber film) on glass substrates are described. These films exhibit a wide range of solar control characteristics. The use of such optical filters enable energy saving in space conditioning of buildings and offor visible transmittance of 7% - 28%, depending on the thickness of NiS and CuS films which is controlled by the durations of deposition     

感光溶胶—凝胶法制备光波导薄膜微图案

利用溶胶-凝胶法制备了有机-无机杂化光敏性SiO2-TiO2材料,在单晶硅基片上旋转涂膜,经前烘、紫外光固化、淋洗、后烘等步骤,在硅片上得到复制有掩模微图案的薄膜。用紫外-可见光-近红外分光光度计测试了薄膜的光透过吸收性质,用Fourier红外光谱仪测试了不同紫外光辐照时间下薄膜的红外振动吸收光谱,用高倍光学显微镜和扫描电子显微镜(SEM)观察制备得到的薄膜微图案。结果表明:薄膜在紫外可见光区域的光透过率约为90%,紫外光照能促使不同的官能团间发生缩聚反应,80℃前烘温度处理以及15min左右的紫外光辐照能够得到清晰、精确的薄膜微图案。     

Dispersion-free highly accurate color recognition using excitonic 2D materials and machine learning

Dispersion is accepted as a fundamental step required for analyzing broadband light. The recognition of color by the human eye, its digital reproduction by a camera, or detailed analysis by a spectrometer all utilize dispersion; it is also an inherent component of color detection and machine vision. Here, we present a device (called artificial eye or, A-Eye) that accurately recognizes and reproduces tested colors, without any spectral dispersion. Instead, A-Eye uses N = 3–12 transmissive windows each with unique spectral features resulting from the broadband transmittance and excitonic peak-features of 2D transition metal dichalcogenides. Colored light passing through (and modified by) these windows and incident on a single photodetector generated different photocurrents, and these were used to create a reference database (training set) for 1337 “seen” and 0.55 million synthesized “unseen” colors. By “looking” at test colors modified by these windows, A-Eye can accurately recognize and reproduce “seen” colors with zero deviation from their original spectra and “unseen” colors with only ∼1 % median deviation, using the k-NN algorithm. A-Eye can continuously improve color estimation by adding any corrected guesses to its training database. A-Eye’s accurate color recognition dispels the notion that dispersion of colors is a prerequisite for color identification and paves the way for ultra-reliable color-recognition by machines with reduced engineering complexity.     

Study of the conditions affecting dye adsorption on titania films and of their effect on dye photodegradation rates

Nanocrystalline titania films have been deposited on glass slides by the sol-gel technique in the presence of surfactant, which plays the role of template of the nanostructure. Several different dyes, both anionic and cationic, have been adsorbed on these films from aqueous solutions. Some of these dyes were adsorbed at large quantities some at lower quantities. Some of them were adsorbed in monomeric form and others formed aggregates. Aggregates are easily distinguished by absorption spectrophotometry, since absorption of light is observed at a different wavelength than monomer absorption in a dilute solution. In all cases, aggregation demonstrated a hypsochromic shift, indicating repulsive interactions, which are justified in view of the fact that titania surface is charged and that adsorbed molecules are aligned in parallel. The above titania films are hydroxylated. Therefore, cationic dyes were readily adsorbed. Anionic dyes could be adsorbed only from aqueous solutions brought at low pH. Photodegradation rates of adsorbed dyes were generally fast since these films are efficient photocatalysts. Nevertheless, photodegradation of an adsorbed dye was faster when the quantity of the dye was smaller. When the adsorbed dyes formed aggregates, aggregation had adverse effect on photodegradation rates.     

超声辅助SILAR法生长纳米晶ZnO多孔薄膜及其光学性能研究

将超声辐照技术引入连续离子层吸附与反应(SILAR)法,提出超声辅助连续离子层吸附与反应(UA-SILAR)液相成膜技术.以锌氨络离子([Zn(NH₃)₄]²⁺)溶液为前驱体,在90℃下沉积得到ZnO薄膜,对其晶体结构,微观形貌、透过光谱和光致发光性能进行表征, 并考察了超声辐照和沉积循环次数对薄膜形貌、结构和光学特性的影响.结果表明,所得薄膜由彼此交联、尺寸均匀的ZnO晶粒组成,呈现典型的多孔特征,同时具有高结晶性和强c轴取向性.由于多孔结构对入射光的散射作用,薄膜在可见光区具有低透射率(约20%);在紫外光激发下,薄膜具有较强的近带边发射和很弱的蓝带发射,体现出薄膜较高的光学质量;薄膜生长过程中超声辐照的引入可对薄膜的结晶性能和微观结构产生显著的影响.     

Optical and structural properties of Mg doped ZnO thin films by chemical bath deposition method

The chemical bath deposition method has often been employed to successfully deposit pure and Mg doped ZnO thin films on a glass substrate. The impact of Mg creates a strained stress in ZnO films affecting its structural and optical properties. XRD patterns revealed that all thin films possess a polycrystalline hexagonal wurtzite structure and Mg doped ZnO thin films (002) plane peak position is shifted towards a lower angle due to Mg doping. From the SEM image, it is understood that the Mg doped ZnO thin films are uniformly coated and are seen as dense rods like pillers deposited over the film. The energy dispersive X-ray analysis confirmed the presence of Mg in doped ZnO thin films. The transmittance spectra exhibit that it is possible for Mg doping to enhance ZnO thin films. The optical energy gap of the films was assessed by applying Tauc’s law and it is observed to show an increasing tendency with an improvement in Mg doping concentrations. The optical constants such as reflectance, index of refraction, extinction coefficient and optical conductivity are determined by using transmission at normal incidence of light by using wavelength range of 200–800 nm. In PL spectra, the band edge emission shifted to the blue with increasing amount of Mg doping.     

Spray deposition and characterization of nanostructured Li doped NiO thin films for application in dye-sensitized solar cells

Transparent conducting Li (0-5?wt%) doped NiO thin films with preferential growth along the (111) plane were deposited onto glass substrates by pyrolytic decomposition of nickel nitrate and lithium chloride precursors at 500?°C in air. The effect of Li concentration on the structural, optical and transport properties of NiO thin films was studied by x-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), spectral transmittance, photoluminescence and linear four-probe resistivity. Activation energies as a function of Li concentration were deduced from the temperature dependent resistivity data measured in the range 300-448?K. The figure of merit was deduced by combining the spectral transmittance and sheet resistance values. The variation in properties of NiO thin film due to Li doping are discussed based on the above results. A dye-sensitized solar cell has also been fabricated for the optimized Li doped NiO thin film and the results are presented.     

Studies on polycrystalline Cd0.96Zn0.04Te thin films prepared by vacuum evaporation

Polycrystalline Cd_0.96Zn_0.04Te thin films are deposited onto glass substrates (Corning 7059) kept at room temperature by vacuum evaporation. The films exhibit zinc blende structure with predominant (1 1 1) orientation. The rms roughness of the films evaluated by atomic force microscope is 3.7 nm. The band gap energy of the films measured by optical transmittance measurement is 1.539 eV. The photoluminescence (PL) spectrum of the films shows intense emission due to free and bound exciton recombination and no emission associated with crystal imperfection and PL line shapes give indications of the high quality of the layers. These films have been implanted with properly mass analyzed Boron ions (¹⁰B⁺) and the effect of implantation has been analyzed by X-ray diffraction, Raman scattering and optical transmittance measurements and the results are explained on the basis of the implantation induced surface roughness and lattice disorder.     

高可见光透过、高紫外截止镀膜玻璃的制备

为了提高镀膜玻璃的可见光透过率, 本研究通过反胶束溶液刻蚀法制备出一种新型玻璃基板, 即表面多孔玻璃。玻璃表面形成了蜂窝状的多孔膜层, 减小了对可见光的反射率, 从而使可见光平均透过率提高了7%。通过一系列射频磁控溅射实验, 探索了可见光平均透过率高, 紫外阻隔率最高的最佳工艺条件。在此条件下, 分别在制备的表面多孔玻璃和普通玻璃上镀CeO₂/TiO₂防紫外线膜, 并采用紫外-可见分光光度计、SEM、XRD、XPS等测试手段对样品进行了分析表征。结果表明, 在相同的镀膜条件下, 当镀膜后表面多孔玻璃与镀膜普通玻璃的紫外光阻隔率均为99%时, 表面多孔玻璃镀膜后的可见光平均透过率为85%, 而普通玻璃镀膜后的可见光平均透过率仅为79%。此外, 玻璃表面上的孔结构还提高了薄膜与基板的接触面积, 使膜基结合力提高2倍左右。     

Fabrication of high quality zinc-oxide layers through electrohydrodynamic atomization

Zinc oxide (ZnO) is a useful material in the fabrication of many electronic devices because of its wide band-gap, excellent transparency and high electron mobility. Thin films of ZnO have been fabricated where an alcosol solution containing 7 wt.% ZnO nano-particles was synthesized and subjected to controlled flow through a metal capillary exposed to an electric field at the ambient temperature to generate an electrohydrodynamic jet, which subsequently disintegrated into droplets thereby depositing a uniform thin film of zinc oxide on the glass substrates with an average thickness of 115 nm at a constant substrate speed of 0.25 mm/s. Pure and perfectly uniform transparent films with an average transmittance of 88% have been deposited with wurtzite crystal structure and an electrical resistivity of approximately 64 Ω.cm.