Direct synthesis of aligned cis-rich polyacetylene films using low-temperature nematic liquid crystals

Liquid crystal polymerization method has been extended so as to cover synthesis of cis-rich polyacetylene films with high alignment. Three kinds of liquid crystal mixtures which maintain nematic phase at lower temperature than 0 °C have been developed by using a series of liquid crystals of phenylcyclohexane derivatives because of their well-confirmed inertness towards Ti(OBu)₄ - AlEt₃ catalyst. It has been implied from DSC measurements that catalyst solutions using three, five and six component systems permit low-temperature polymerizations ranging from −20 to −30 °C, from −40 to −60 °C and from −10 to −45 °C, respectively. Polyacetylene films synthesized by using five and six component liquid crystals with and without an external magnetic force have high cis contents of 85 – 94 %. High alignment of fibril morphology of the films has also been confirmed through SEM observations. Measurements of electrical conductivity of the films upon iodine doping yielded a maximum conductivity of 1.6 × 10⁴ S/cm and electrical anisotropy of 7.0.     

Interaction between Electrical Arc and Nd: YAG Laser Radiation

This paper describes the stabilization and guidance of plasma plumes through the interaction with low power laser radiation. The stabilization and guidance have been found to be governed by several physical effects. One effect is the localized rise of electrical conductivity. As the laser provides a channel of increased conductivity an alignment and a stabilisation of the electrical arc can be obtained. This feature can be exploited to achieve more efficient and flexible plasma processes. Investigations on plasma guidance with respect to different laser wavelengths and interaction modes will be presented by means of example in welding and EDM.     

Effect of annealing temperature on optical band-gap of amorphous indium zinc oxide film

The effect of annealing temperature on the electrical and optical properties of indium zinc oxide (IZO) (In₂O₃:ZnO = 90:10 wt.%) thin films has been investigated. The IZO thin films were deposited on glass substrates by radio frequency magnetron sputtering and then subjected to annealing in a mixed ambient of air and oxygen at 100, 200 and 300 °C. All the IZO films were found to have amorphous structure. With the increase of the annealing temperature, the carrier concentration decreased and the resistivity increased. The average transmittance of IZO thin films decreased slightly with annealing temperature. Interestingly, a systematic reduction of the optical band-gap from 3.79 eV to 3.67 eV was observed with annealing temperature. The change in optical band-gap was observed to be caused predominantly by Burstein-Moss band-gap widening effect suggesting unusual absence of band narrowing effect. The effects on optical and electrical properties of IZO films have been discussed in detail.     

Optical and electrical properties and photoexcited laser oscillation of composite film based on π-conjugated polymers

The optical and electrical properties of polymer composite films based on poly(2-methoxy-5-dodecyloxy-p-phenylenevinylene) (MDDOPPV) and poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT) have been studied. The optical properties, such as, absorption and photoluminescence (PL) spectra, PL efficiency, and PL lifetime of the polymer composite films, have been clarified. Utilizing the polymer composite thin film consisting of 50%-F8BT as an emission layer, the multimode lasing from a microcapillary structure with low threshold energy by pulsed photo-pumping and the high current density injection have been demonstrated.     

Solder engineering for optoelectronic packaging

In addition to providing electrical connections, solder is useful in the formation of passive, precision alignments for optoelectronic packaging. Different designs have demonstrated micrometer-level alignment accuracies, and the aligned structures are becoming more and more complex. Solder engineering has been successfully introduced into the field of optoelectronics, and it is expected to be applied to many other areas demanding low-cost, precision alignments.     

Preparation and Properties Of ZnO:Al (ZAO) Thin Films Eposited by DC Reactive Magnetron Sputtering

采用磁控溅射技术制备了ZnO:Al(ZAO)薄膜。研究了不同的工艺参数对薄膜的组织结构和光电特性的影响.实验结果表明，多晶ZAO薄膜具有（001）择优取向且呈柱状生长，能量机制决定其微观生长状态。讨论了薄膜的内应力，高的沉积温度和低的溅射功率可有效减小薄膜的内应力。优化的ZAO薄膜电阻率和在可见光区的平均透射率可分别达到310-4-410-4cm和80%以上。     

Study of 4,4′-bis(4-dimethylaminostyryl) benzene based diodes

The electrical and optical characteristics of 4,4′-bis(4-dimethyl amino styryl) benzene (DMASB), a new derivative of poly(p-phenylene vinylene) (PPV) have been investigated for use as an active layer in light emitting diodes (LEDs). Analysis of photoluminescence and Raman spectra shows that the oligomer has properties close to those of PPV and the incorporated amino groups do not change significantly the optical absorption of PPV. The current–voltage characteristics of the DMASB based diodes show rectifying behavior, which is dependent on the nature of metals used for the electrodes. Analysis of the polymer–metal interfaces reveals that chemical interactions between the polymer and the metals have occurred and these results are related to the electrical behaviour of the diodes.     

Effects of heat treatment on morphological, optical and electrical properties of ITO films by sol-gel technique

Indium-tin-oxide（ITO） films were prepared on the quarts glass by sol-gel technique. Effects of different heat treatment temperatures and cooling methods on the morphological, optical and electrical properties of ITO films were measured by TG/DTA, IR, XRD, SEM, UV-VIS spectrometer and four-probe apparatus. It is found that the crystallized ITO films exhibit a polycrystalline cubic bixbyite structure. The heat treatment process has significant effects on the morphological, optical and electrical properties of ITO films. Elevating the heat treatment temperature can perfect the crystallization process of ITO films, therefore the optical and electrical properties of ITO films are improved. But the further increasing of heat treatment temperature results in the increment of ITO films＇ resistivity. Compared with ITO films elaborated by furnace cooling, those prepared through air cooling have following characteristics as obviously decreased crystalline size, deeply declined porosity, more compact micro-morphology, improved electrical property and slightly decreased optical transmission.     

Dark and photoconductive properties of hydroxymethylferrocene

The dark electrical conduction properties of hydroxymethylferrocene have been studied as a function of voltage at different sample cell temperatures by using sandwich-cell configuration. The analysis of the results has been based on the space charge limited conduction (SCLC) theory. The distribution of traps in this material has been found to be single discrete level type. Photoconductivity in this material has been studied as a function of the intensity of exciting light source (mercury lamp; 125 W) and sample cell temperature. The results have been compared with the results of ferrocene and, in some cases, with other ferrocene derivatives. An unusual temperature-dependence of photocurrent has been observed. The possible origin of this observation has been discussed.     

Synthesis,characterization, mesomorphic and electrical properties of tetrakis(alkylthio)-substituted lutetium(III) bisphthalocyanines

The synthesis of new lutetium(III) bisphthalocyanines substituted with alkylthio groups (1–5) is described. These compounds (Pc₂Lu) are soluble in most common organic solvents and have been fully characterized (elemental analysis, FT-IR, UV–Vis spectroscopy, mass spectrometry). The thermal stabilities of the Pc compounds were determined by thermogravimetric analysis (TGA). The mesogenic properties of these new materials forming columnar-hexagonal (Col_h) mesophases were studied by differential scanning calorimetry (DSC), optical microscopy and X-ray diffraction. The compounds 2–5 exhibit a double clearing point. DC electrical properties of these compounds in different phases were determined by measuring I–V characteristics and dark current of their thin films on interdigital electrodes. The measurements were carried out in ambient air, in vacuum and in high purity nitrogen (N₂) flow in the temperature range between 300 and 420 K. Dark current measurements obtained in the crystal, liquid crystal (LC) and isotropic liquid phases were in agreement with the phase transitions of these compounds obtained by DSC and optical microscopy results. The relation between the phase transition and conductivity of the Pc₂Lu derivatives were investigated. Also, the influence of the nature of the substituted group (alkylthia and alkoxy) upon the DC electrical properties of the Pc₂Lu derivatives was investigated. The DC conductivities and the thermal activation energies depending on alkyl chain lengths of these compounds were found to be in the range of 10^?8 to 10^?5 S/cm and 0.12–0.38 eV in solid phase.     

Photoconductivity in Langmuir—Blodgett multilayer structures of phthalocyaninato-polysiloxane

The electrical and photoelectrical properties of planar photodiodes based on phthalocyaninato-polysiloxane (PcPS) are presented. Sandwich structures consisting of thin PcPS Langmuir—Blodgett films have been prepared between semi-transparent gold and aluminum electrodes. These structures possess pronounced rectifying behavior. The photocurrent spectra exhibit peaks at 550 and 700 nm. The wavelength dependence of the photoconductivity clearly differs from the linear optical properties.     

Organic metals and semiconductors: The chemistry of polyacetylene, (CH)x,and its derivatives

Polyacetylene, (CH)_x, is the simplest organic polymer. Both the cis- and trans-forms may be prepared as silvery, flexible, polycrystalline, semiconducting films. The cis-films can be stretched to over three times their original length with partial alignment of the (CH)_x fibrils. Through chemical or electrochemical doping, the electrical conductivity of the films can be increased over twelve orders of magnitude with properties ranging from insulator (σ < 10^?10 ohm^?1 cm^?1) to semiconductor, to metal (σ > 10³ ohm^?1 cm^?1). By the use of donors or acceptors, n-type or p-type polymer, respectively, is produced. When doped, the partly aligned (CH)_x film shows marked anisotropic electrical and optical properties. The more chemically oriented aspects of (CH)_x and its derivatives and those physical studies which are most illustrative of the effects of doping will be discussed.     

Synthesis of aza-analogues of poly(isothianaphthene)

The reaction of phthalic anhydride with phosphorus pentasulfide which gives poly(isothianaphthene) (PITN) has been extended to some other anhydrides and its derivatives (phthalimides and phthalhydrazide). The reaction with anhydrides leads to polymers, while the reaction with other derivatives can lead to thio, dithio compounds or polymers. Contrary to theoretical predictions, aza-analogues of PITN do not seem to have better electrical properties. The most conductive is polyisoindol with conductivity of 10⁻⁴ S/cm, which is still 100 times lower than PITN synthesized under similar conditions.     

Structural,electrical, and optical properties of reactively sputtered SnO<Subscript>2</Subscript> thin films

SnO₂ thin films prepared by reactive rf magnetron sputtering have been investigated to examine the effect of deposition parameters on its crystallinity and electrical and optical properties. Of particular interest was whether the nonequilibrium nature of sputtering could create large departures from the bulk defect properties, especially in amorphous films. Two deposition parameters were examined: substrate temperature (T_sub) and oxygen content. The films were characterized by X-ray diffraction (XRD), optical transmission, four point probe electrical conductivity, and Hall effect measurements. The crystallinity was found to be enhanced by the incease in each of the three processing variables. Below a substrate temperature of 300 °C a large processing window for depositing amorphous SnO₂ was found.     

Nanopowder synthesis of aluminum doped cadmium oxide via sol-gel calcination processing

The structural, optical and electrical properties of undoped and Al-doped CdO powder nanostructures prepared by sol-gel calcinations method have been investigated. X-ray diffraction (XRD) results revealed that pure and Al-doped CdO have the polycrystalline with face centered cubic (FCC) structure. The crystallite size for undoped and 5, 10, 15, 20% of Al-doped CdO samples were found to be 17.2, 15.9, 16.1, 16.3 and 16.8 nm, respectively. The optical band gap of the samples were determined from the diffused reflectance spectra and E_g values for undoped and 5, 10, 15, 20% of Al-doped CdO samples were found to be 1.89, 2.07, 2.03, 2.07 and 2.12 eV, respectively. The electrical conductivities of pure and Al-doped CdO were measured in the temperature range (290-420 K) and their temperature dependence was analyzed according to Arrhenius relation. The electrical conductivity results indicate that the electrical conductivity mechanism is controlled by thermally activated processes. The results showed that sol-gel calcinations technique can be effectively used to produce undoped and doped nanopowders.     

大气等离子喷涂Al2O3-3%TiO2涂层的性能

利用两种中频交流磁控溅射电源,溅射Al2O3含量为2%的两块氧化锌铝陶瓷靶材,在不同衬底温度的条件下制备得到了ZAO薄膜。研究了不同衬底温度条件下不同靶材和溅射电源对ZAO薄膜结构、电学和光学性能的影响。结果表明,制备得到的ZAO薄膜均具有c轴择优取向生长的晶体结构,在衬底温度为240℃时,得到的ZAO薄膜的电阻率低至1.4×10-3Ω·cm,可见光平均透过率在82%以上。     

Dynamical aspects of photo-induced phase transition in polydiacetylenes

Dynamics of the photo-induced phase change has been investigated in thin solid films of polydiacetylene (PDA). It was found that a visible light pulse can cause a fast photochromic conversion associated with the bond structure change in PDAs. This novel phase transition has been proved to be mediated by photo-generated electrons (or holes) on the backbones and not by optically active excitons. On this basis, we have succeeded in dye-sensitization of the photo-induced phase transition by utilizing the carrier injection from the adjacent dye layer into the PDA layer.     

Influence of machining errors on form errors of microlens arrays in ultra-precision turning

Ultra-precision turning is widely used in machining microlens arrays. Machining errors have an effect on the form accuracy of the whole microlens array, but they have not been fully studied, especially the effect on the optical performance. A machining error model of microlens arrays is built to analyse the coordinate distortions and form errors easily based on multi-body system theory and a homogeneous transformation matrix. The simulative and experimental results verified the influence of three major machining errors (tool alignment errors (∆x, ∆y), tool nose radius error (∆R) and squareness error (∆θ) from the proposed approach. Through the simulation and experimental approach, this study describes the distribution of the form errors as axisymmetric; the form error of the centre part of the row and column cells is minimal, whereas that of the diagonal cells is the maximum. The optical performance of the cells has the same correlation as the form errors. Based on the above study, a horizontal off-centring machining method is proposed to achieve high form accuracy and uniform optical performance.     

Modification of physical properties of iridium with a surface monolayer graphite film as a result of intense diffusion of potassium atoms

Methods of thermionic emission and measurements of the brightness and true temperatures have been used to study the effect of intense diffusion of potassium atoms in iridium on the variation of the electrical, optical, and emission properties of iridium. It has been shown that after the intense diffusion of potassium atoms through the interphase boundary between the surface and the bulk of the Ir(111) face the work function of iridium decreases from 5. 8 to 5. 3 eV, whereas the integral emissivity, spectral emissivity, and electrical resistance increase by ∼10, ∼30, and ∼20%, respectively.     

Electronic properties and crystal structure of orderable Cu<Subscript>3</Subscript>Pd alloy

Transmission electron microscopy has been used to study the microstructure of ordering Cu₃Pd alloys. The effect of atomic ordering of the alloys on their electrical, magnetic, and optical properties has been studied.