Extended Conjugation in Polyaniline Like Structure Prepared by Plasma Polymerization Suitable for Optoelectronic Applications

Plasma polymerization of aniline is carried out in a radiofrequency plasma reactor and the effect of polymerization time is examined in the structural, optical and optoelectronic properties of deposited films. Conjugated structures of polyaniline like films are obtained with unique and broad optical absorption band in the ultraviolet and entire visible region. The width of the absorption band increases and hence the optical band gap decreases with polymerization time. The optical constants are extracted by Swanepoel method and the optical dispersion parameters are determined by employing the Wemple-DiDomenico single oscillator model. The films exhibit similar thermal stability in air and argon atmosphere in the region of interest for optoelectronic applications. The photoluminescence study suggests, like the chemically synthesized polyaniline, the benzenoid units to be responsible for fluorescence. The fluorescence peaks due to defect states confirm the formation of spectroscopic units in the plasma polyaniline films.     

Effects of In, Al and Sn dopants on the structural and optical properties of ZnO thin films

Effect of In, Al and Sn dopants on the optical and structural properties of ZnO thin films have been investigated by X-ray diffraction technique and optical characterization method. X-ray diffraction patterns confirm that the films have polycrystalline nature. The thin films have (002) as the preferred orientation. This (002) preferred orientation is due to the minimal surface energy which the hexagonal structure, c-plane to the ZnO crystallites, corresponds to the densest packed plane. The grain size values of the films are found to be 29.0, 35.2 and 39.5 nm for In, Al and Sn doped ZnO thin films, respectively. The optical band gaps of the films were calculated. The absorption edge shifts to the lower wavelengths with In, Al and Sn dopants. The inclusion of dopant into films expands also width of localized states as E(UIn)>E(UAl)>E(USn). The refractive index dispersion curves obey the single oscillator model. The dispersion parameters and optical constants of the films were determined. These parameters changed with In, Al and Sn dopants.     

Preparation and characterization of nanorods Sb doped CdO films by sol–gel technique

Pure and antimony (Sb) doped CdO films were grown using sol–gel spin coating technique. The structural properties of the films were investigated using atomic force microscopy. The structure of CdO film is converted from microrods to nanorods with Sb dopant. The analysis of optical absorption revealed that optical bandgap of the films changes with doping. The optical bandgap for 0.1, 0.5, 1.0, and 2.0% Sb doped CdO was determined to be 2.28, 2.30, 2.56, and 2.42 eV, respectively. Other optical constants such as refractive index, extinction coefficient, and dielectric constants were calculated using the optical data. The refractive index dispersion of the films obeys the single oscillator model. The volume and surface energy loss functions were calculated and observed to increase with increase in the photon energy.     

Single oscillator model and refractive index dispersion properties of ternary ZnO films by sol gel method

The optical constants of the NiMnZnO thin films prepared by spin-coating method were determined using transmittance and reflectance spectra. The optical band gap of the NiMnZnO thin films was found to be in the range of 3.20–3.35 eV. The refractive index dispersion of the NiMnZnO films obeys the single oscillator model. The dispersion energy and oscillator energy values of the NiMnZnO films were found to be in the range of 6.46–9.85 and 4.82–5.54 eV, respectively. The real and imaginary parts of the dielectric constants of the NiMnZnO films were determined. The reflectance spectra of the NiMnZnO films give a peak and the presence of this peak is due to the photoexcitation process, in which, the electrons are excited from valence band to the conduction band. The obtained results suggest that the optical constants and refractive dispersion energy parameters of the films are controlled by the molar ratios of NiMnZnO films.     

混合溶剂对可录型光盘中吲哚类菁染料薄膜性能的影响

本文采用紫外可见光谱、FT-IR及AFM等手段,研究了混合溶剂对光盘记录介质吲哚类菁染料薄膜光学性能、稳定性和表面结构的影响.发现在不同混合溶剂下涂出的相同膜厚的染料薄膜,其光学性能和表面形貌都有很大的差异.不同的混合溶剂都存在一个最佳混合体积比,染料在此体积比下旋涂出膜的光学性能和表面形貌均优于单一溶剂下涂出的膜.对比不同混合溶剂涂出的膜的光学性质及AFM的观测结果,发现二丙酮醇与氯仿在等体积比混合、四氟丙醇与氯仿在7:3体积下混合时效果最好,易得到反射率高,表面较平整的染料薄膜.     

Preparation of high-quality organic semiconductor nanoparticle films by solvent-evaporation-induced self-assembly

Organic semiconductor nanoparticles are expected to be used in organic optical and electronic devices due to their unique optical and electrical properties. However, no method has been reported for the preparation of high-quality organic nanoparticle films without remaining additives and being capable of dealing with binary nanoparticle blends. We developed a simple approach to fabricate high-quality organic semiconductor nanoparticle films from their aqueous solutions by solvent-evaporation-induced self-assembly. Only volatile solvents are employed in the nanoparticle solutions, so the self-assembled nanoparticle films are free of additives. Moreover, this method is also suitable for fabricating thin films containing binary nanoparticles. Therefore, it paves the way for potential applications of organic semiconductor nanoparticles in nanoscale optical and electronic devices.     

Organic electroluminescent and nonlinear optical materials

The multilayer electroluminescent(EL) devices composed of vacuum-sublimed organic films are discussed with the aims of achieving high luminance and proposing an optical micro-cavity. For the former purpose, requirements for confinements of carriers and excitons within the thin emissive layer are shown by taking accounts of ionization potentials, electron affinities and excitation energies in organic thin films. Concerning the interference effect of emitted light, we show the variation in the intensity of emission and a strongly directional light from the micro-cavity. Second-order nonlinear optical(NLO) films are designed by preparing noncentrosymmetric LB multilayers composed of an pyrazine derivative with large hyperpolarizability and arachidic acid. Third-order nonlinear optical(NLO) films are proposed by using polyarylenevinylene films. In order to fabricate excellent third-order nonlinear optical(NLO) films, highly oriented polyarylenevinylene films are prepared by using a LB technique.     

Preparation and trans–cis isomerization of azobenzene-containing TiO2/ormosils hybrid films derived at a low temperature sol–gel process for photonic applications

Azobenzene-containing TiO₂/γ-glycidoxypropyltrimethoxysilane and methyltrimethoxysilane hybrid films are prepared by combining a low temperature sol–gel process and a spin-coating technique. The trans–cis isomerization of azobenzene small molecules inside organic–inorganic hybrid films is induced by a photoirradiation under UV light. It is noted that below a baking temperature of 150 °C is necessary for the hybrid films in optical storage or optical switching applications. The change of the refractive index and thickness of the hybrid films with real-time heating temperature are observed by using a prism coupling technique. The structural properties of the hybrid films are also characterized and investigated by thermal gravimetric analysis, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The results indicate that the as-prepared hybrid films might allow directly integrating the optical storage or optical switching devices with the waveguide devices on the same chip.     

The fabrication of novel optical diffusers based on UV-cured polymer dispersed liquid crystals

Polymer dispersed liquid crystals (PDLCs) with different sizes of the LC droplets are prepared based on the ultraviolet (UV) light curable acrylate monomers/LCs composites to fabricate the optical diffuser films. To acquire light diffusers with high optical performance, the effects of the monomer structure and the UV light intensity on the micro-structure of the PDLC films are studied. Results show that the PDLC films could exhibit a strong light scattering at the premise of maintaining high transmittance in the visible region. As the LC droplets are spherically dispersed in the polymer networks, when the size of LC droplets is about 3.0 μm, the haze can reach 88.5% and the transmittance is nearly 90.0%, which can be used as a bottom diffuser film. While when the size of LC droplets is about 10.0 μm, the haze and transmittance are 39.2% and 90.2%, respectively; hence, it can be a good choice for a top diffuser film. With the advantages of simple preparation, roll-to-roll industrial production and tunable optical properties, it is supported that the films based on UV-cured PDLC films can be applied as outstanding optical diffuser films in the liquid crystal display industry.     

Preparation of nanostructure Ni doped CdO thin films by sol gel spin coating method

The nanostructure Ni-doped CdO films have been prepared by sol gel spin coating method. Atomic force microscopy results indicate that the CdO films are formed from the nanoparticles and the grain size is changed with nickel content. X-ray diffraction patterns of the films indicate that the undoped and Ni-doped CdO films have polycrystalline structure with a cubic sodium chloride structure, showing two main characteristic peaks assigned to the (111) and (200) planes. The optical band gap values of undoped and Ni-doped CdO films were determined by optical absorption method. The E_g values of the CdO films were found to be in the range of 2.26–2.60 eV. The E_g values of the CdO films increase with the content of Ni dopant (up to 6% Ni). It is evaluated that the optical band gap and grain size of the CdO film can be controlled by doping with nickel atoms.     

Indium and aluminium-doped ZnO thin films deposited onto FTO substrates: nanostructure,optical, photoluminescence and electrical properties

The microstructure, optical, photoluminescence and electrical properties of ZnO based films deposited onto FTO glass substrates by ultrasonic spray pyrolysis have been investigated. For comparison and a better understanding of physical properties of indium- and aluminum-doped ZnO and undoped ZnO thin films, X-ray diffraction analysis, photoluminescence spectra, optical, SEM texture and electrical conductivity analyses were performed. The AZO and IZO films exhibit the nanofiber structure with diameters 260 and 400 nm. X-ray diffraction showed all samples to be polycrystalline with hexagonal ZnO. The optical band gaps of the films were varied by Al and In dopants. The photoluminescence spectra of the films show a weak broad in the visible range and shifted to green emission for indium doping and to the green blue emission for aluminum as dopant. The width of the PL spectra for aluminum-doped films is too large compared to those of the indium-doped ones. The electrical conductivity of the ZnO film changes with Al and In dopants. The position of donor levels changes with In and Al dopants and approaches the conduction band level with the metal dopants. The obtained results suggest that the metal doping has a clear effect upon the growth, optical, photoluminescence and electrical conductivity properties of the ZnO films.     

Recognition of the carbon thin films sub-structures: thermo-optical measurements

Carbon thin films oxidation was investigated on-line by high-sensitivity optical transmission (OT) method. The films have been prepared by common vacuum arc discharge and subsequently air oxidized at linear heating rates until temperatures of their complete gasification. The shape of the optical curves acquired was interpreted in light of deduced partial optical changes, each of them being ascribed by simple sigmoidal dependence. The dependencies converted to their derivative form ordered respective to the temperature scale conveniently represent an inter-relationship among the sequentially evolved films’ optical events, considered as being closely related to the individual carbon-replenishing steps. The dependencies correspond well to the ones obtained on thicker films by means of the thermogravimetry (TG) measurements.     

TixV1-xO2薄膜的光学及相变特性

采用射频磁控溅射方法,在c-Al2O3(0001)基底上制备了不同钒钛比例的TixV1-xO2(0≤x≤1)薄膜,利用X射线衍射(XRD)、拉曼(Raman)光谱、紫外-可见-近红外(UV-Vis-NIR)光谱对薄膜结构及光学性能进行测试分析,计算薄膜的太阳能智能调节率和光学带隙.实验结果及分析表明:随着Ti含量的增加,薄膜的红外调节特性和热滞特性逐渐减弱直至消失;薄膜样品的光学带隙随着Ti含量的增加而变宽,光响应范围发生蓝移;其光学带隙随着V含量的增加而变窄,光响应范围发生红移.     

Synthesis and Characterization of Highly Oriented Sol-Gel (Pb, La) TiO3 Thin Film Optical Waveguides

The preparation and the optical characteristics of highly oriented PLT thin films are investigated. PLT films fabricated on MgO(100) and c-plane sapphire substrates have highly grown in (100) and (111) orientations, respectively. PLT films with high La content have a near cubic structure and weak anisotropy of refractive indices. The optical propagation losses of PLT films decrease as the La content of the films increases due to a complex interaction of surface roughness reduction and a reduction in the anisotropy refractive index. However, optical scattering in thicker sol-gel PLT thin film waveguides occurs by the internal scattering mechanism from the defects and the interfaces rather than by the surface scattering mechanism.     

Absolute absorption measurements of polymer films for optical waveguide applications by photothermal deflection spectroscopy

A self‐contained experimental technique is proposed for measuring the absolute optical absorption spectra, thermal diffusivity, and thermal conductivity of polymer thin films. The technique is based on photothermal deflection spectroscopy and provides sensitivity that is high enough to quantify the very small optical absorption losses in polymer films used for optical waveguide applications. The capabilities of the technique are demonstrated with measurements performed on thin films of poly(methyl methacrylate) and a fluorinated polymer (CYTOP). An error analysis is presented, and the factors are discussed that influence the accuracy of the technique. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2717–2726, 2001     

沉积电位对电沉积ZnS薄膜的影响

采用电沉积方法,在不同沉积电位条件下,在氧化锡铟(ITO)导电玻璃上沉积制备了ZnS薄膜,利用XRD、SEM和UV-VIS测试技术对在不同沉积电位所制备薄膜的晶相结构、表面微观形貌和光学性能进行了表征.研究结果表明:沉积电位在1.5 V—1.7 V范围内制备的ZnS薄膜呈非晶态,其可见光透过率从60 %降低到20 %,薄膜的光学带隙约为3.97 eV.在沉积电位为2.0 V条件下所沉积薄膜为ZnS结晶相和金属Zn混合相,薄膜透过率显著降低.     

Development of an optical ammonia sensor based on polyaniline/epoxy resin (SU-8) composite

Polyaniline (PANI)/glycidyl ether of bisphenol A (SU-8) composite film is elaborated in order to detect ammonia gas. These composite films are characterized by ultraviolet-visible (UV-vis) spectroscopy, Fourier transformed infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The sensitivity to ammonia is measured by optical absorption changes. The ammonia sensing properties of PANI/SU-8 composite films are studied, and then are compared to pure PANI films elaborated by chemical way. Experimental results show that the PANI/SU-8 optical sensor has simultaneously a rapid response to ammonia gas and regenerates easily, that is advantageous compared to pure PANI films.     

Contradictory ageing behaviour and optical property of iodine doped and H2SO4 doped pulsed DC plasma polymerized aniline thin films

Polymerization of aniline in the presence of H₂SO₄ and iodine vapour is carried out using pulsed DC glow discharge plasma. The as prepared iodine doped plasma polymerized aniline films are found to be highly crystalline due to some crystal structure formed by the iodine incorporated into the film and the ex-situ H₂SO₄ doped films are found to be amorphous. However, the structure of the iodine doped films transforms to amorphous one while that of the ex-situ H₂SO₄ doped films transforms to crystalline one due to the effect of ageing. The optical band gap of the samples decreases depending upon the level of doping and annealing, having minimum optical band gap for iodine doped plasma polymerized aniline. Due to ageing, the optical property of the H₂SO₄ doped film is found to become superior while for iodine doped films a negligible change of the optical property has been noticed even after six months of ageing.     

高折射率有机/无机纳米杂化透明膜层材料的制备与性质研究

采用溶胶-凝胶法,将钛酸酯和硅烷偶联剂(KH-560)进行共水解,经涂膜、固化,制备了一系列含有无机二氧化钛纳米相的无机/有机杂化膜层材料,通过不同方法对杂化膜层的微结构、光学、机械和热性质进行了表征.结果表明,所得到的有机/无机纳米复合膜层,在可见光范围内的透过率均在90%以上,同时具有较好的耐热性和较高的折射率(nd=1.47~1.73),并且膜层与基材的附着性好,铅笔硬度达到4~5H.     

Optical properties of nanostructure boron doped NiO thin films

Boron doped NiO films were prepared by sol–gel method. The effects of B content on the morphological and optical properties of NiO films were studied with atomic force microscopy, and optical characterization method. The average transmittance at the visible region is reached to 75 % for lower doped films (0.1 and 0.2 % B), whereas, the recorded average value of transmittance was about 62 % for doped film with 1 % B throughout the region. The optical energy gap value for pure NiO film was found to be 3.73 eV. These values were affected by B doping with non-monotonic variation and reached to 3.64 eV for 0.1 % B doped NiO. Also, the refractive index dispersion and dielectric constants of the NiO films were studied throughout the investigated range of wavelengths. The obtained results indicate that the optical parameters of the NiO film are controlled with boron doping.