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991.
Determination of retardation parameters of multiple-order wave plate using a phase-sensitive heterodyne ellipsometer 总被引:2,自引:0,他引:2
To characterize the linear birefringence of a multiple-order wave plate (MWP), an oblique incidence is one of the methods available. Multiple reflections in the MWP are produced, and oscillations in the phase retardation measurement versus the oblique incident angle are then measured. Therefore, an antireflection coated MWP is required to avoid oscillation of the phase retardation measurement. In this study, we set up a phase-sensitive heterodyne ellipsometer to measure the phase retardations of an uncoated MWP versus the oblique incident angle, which was scanned in the x-z plane and y-z plane independently. Thus, the effect on multiple reflections by the MWP is reduced by means of subtracting the two measured phase retardations from each other. As a result, a highly sensitive and accurate measurement of retardation parameters (RPs), which includes the refractive indices of the extraordinary ray n(e) and ordinary ray n(o), is obtained by this method. On measurement, a sensitivity (n(e),n(o)) of 10(-6) was achieved by this experiment setup. At the same time, the spatial shifting of the P and S waves emerging from the MWP introduced a deviation between experimental results and the theoretical calculation. 相似文献
992.
A novel lighting system was devised for 3D defect inspection in the wire bonding process. Gold wires of 20 microm in diameter were bonded to connect the integrated circuit (IC) chip with the substrate. Bonding wire defects can be classified as 2D type and 3D type. The 2D-type defects include missed, shifted, or shorted wires. These defects can be inspected from a 2D top-view image of the wire. The 3D-type bonding wire defects are sagging wires, and are difficult to inspect from a 2D top-view image. A structured lighting system was designed and developed to facilitate all 2D-type and 3D-type defect inspection. The devised lighting system can be programmed to turn the structured LEDs on or off independently. Experiments show that the devised illumination system is effective for wire bonding inspection and will be valuable for further applications. 相似文献
993.
A novel fiber-optic biosensor based on a localized surface plasmon coupled fluorescence (LSPCF) system is proposed and developed. This biosensor consists of a biomolecular complex in a sandwich format of . It is immobilized on the surface of an optical fiber where a complex forms the fluorescence probe and is produced by mixing Cy5-labeled antibody and protein A conjugated gold nanoparticles (Au-PA). The LSPCF is excited by localized surface plasmon on the GNP surface where the evanescent field is applied near the core surface of the optical fiber. At the same time, the fluorescence signal is detected by a photomultiplier tube located beside the unclad optical fiber with high collection efficiency. Experimentally, this novel LSPCF biosensor is able to detect mouse immunoglobulin G (IgG) at a minimum concentration of 1 pg/mL (7 fM) during the biomolecular interaction of the IgG with anti-mouse IgG. The analysis is expanded by a discussion of the amplification of the LSPCF intensity by GNP coupling, and overall, this LSPCF biosensor is confirmed experimentally as a biosensor with very high sensitivity. 相似文献
994.
Image enhancement is an essential procedure in machine vision-based inspection. In practical applications, image enhancement is usually a part of image pre-processing, intended to make the following inspection more effective. The image enhancement method is usually selected by trial-and-error or on the basis of experience. This paper presents an automatic procedure for fast and effective image enhancement. The procedure uses multivariate analysis to automatically construct an optimal image enhancement model. First, an optimally enhanced image was selected from the literature as a basis for the model. Then, the image features were identified and Wilks’ statistic was used for feature selection. Next, discriminate functions were built to select the optimal image enhancement method. To verify the model, 53 training images from the literature and 12 test images from a local company were used in an experimental analysis. The model achieved 98.11% accuracy in selecting the most suitable image enhancement method, and the average increase in contrast was 98% for the 53 training images. The enhancement method selection results for the 12 test images were also in agreement with the 53 training images from the literature. The results show that the proposed method is effective and appropriate for quickly improving image contrast. 相似文献
995.
Chun-Yuan Huang Tzu-Min Ou Shu-Ting Chou Meng-Chyi Wu Shih-Yen Lin Jim-Yong Chi 《Nanotechnology, IEEE Transactions on》2007,6(6):589-594
In this paper, we report that low-density InAs/GaAs quantum dots (QDs) can be formed by postgrowth annealing the samples with 1.5-monolayer (ML) InAs coverage, which is thinner than the critical layer thickness for the Stranski-Krastanov growth. The annealing procedure was performed immediately after the deposition of the InAs layer. The effects of annealing time and annealing temperature on the dot density, dot size, and optical characteristics of the QDs were investigated. The optimum annealing conditions to obtain low-density QDs are longer than 60 s and higher than 500degC . Meanwhile, no luminescence can be observed for the wetting-layer, which may suggest that the postgrowth annealing will make the wetting layer thinner and thus reduce the effects of wetting layer on carrier relaxation and recombination. On the other hand, we observe that a decrease of the PL intensity at the annealing conditions of 60 s and 515degC , which is possibly due to the increasing surface dislocations resulted from the In adatom desorption at higher annealing temperature. 相似文献
996.
Keh-Moh Lin Ru-Li Lin Wen-Tse Hsiao Sin-Wei Wu Chia-Yuan Chou 《Journal of Materials Science: Materials in Electronics》2017,28(7):5144-5153
In this study, Ag nanowire (AgNW) was used to fabricate ITO/AgNW/ITO (IAI) and ZnO/AgNW/ZnO (ZAZ) hybrid transparent electrodes. The covered area ratio of AgNW showed that when AgNW concentration n AgNW ≥ 2.0 mg/mL, AgNW easily agglomerated during the spin-coating. Meanwhile, Haacke index and haziness measurements also indicated that for application with high optical demands, the AgNW concentration should be ≤2.0 mg/mL for both ZnO or ITO systems. In this study, when n AgNW = 2.0 mg/mL, the sheet resistant of ZAZ electrodes was 10.5 Ω/sq while the transmittance (including glass) was 72.7% in the visible region. For IAI electrodes, the sheet resistant was 18.8 Ω/sq and transmittance (including glass) was 78.2% in the visible region. Further analysis implied that the sheet resistance of hybrid electrodes could be as low as 10 Ω/sq by optimizing AgNW distribution as well as using suitable annealing techniques. 相似文献
997.
Sodium-ion batteries have received remarkable attention as next-generation high-performance electrochemical energy storage devices because of their cost effectiveness and the broad geographical distribution of sodium. As a critical component of sodium-ion batteries, anode materials, especially nanostructured anodes, have a significant effect on the electrochemical performance of sodium-ion batteries. Recent research indicates that phosphorus and metal phosphides show great promise as anode candidates for sodium-ion batteries because of their low cost and relatively high theoretical gravimetric and volumetric specific capacities. In this review, we systematically summarize recent research progress on state-of-the-art nanostructured phosphorus and phosphides, including the synthetic strategies, Na-storage mechanisms, and the relationship between the nanostructure and electrochemical performance. Moreover, we present an overview of future challenges and opportunities based on current developments. 相似文献
998.
Carbon‐Coated Na3.32Fe2.34(P2O7)2 Cathode Material for High‐Rate and Long‐Life Sodium‐Ion Batteries 下载免费PDF全文
Mingzhe Chen Lingna Chen Zhe Hu Qiannan Liu Binwei Zhang Yuxiang Hu Qinfen Gu Jian‐Li Wang Lian‐Zhou Wang Xiaodong Guo Shu‐Lei Chou Shi‐Xue Dou 《Advanced materials (Deerfield Beach, Fla.)》2017,29(21)
Rechargeable sodium‐ion batteries are proposed as the most appropriate alternative to lithium batteries due to the fast consumption of the limited lithium resources. Due to their improved safety, polyanion framework compounds have recently gained attention as potential candidates. With the earth‐abundant element Fe being the redox center, the uniform carbon‐coated Na3.32Fe2.34(P2O7)2/C composite represents a promising alternative for sodium‐ion batteries. The electrochemical results show that the as‐prepared Na3.32Fe2.34(P2O7)2/C composite can deliver capacity of ≈100 mA h g?1 at 0.1 C (1 C = 120 mA g?1), with capacity retention of 92.3% at 0.5 C after 300 cycles. After adding fluoroethylene carbonate additive to the electrolyte, 89.6% of the initial capacity is maintained, even after 1100 cycles at 5 C. The electrochemical mechanism is systematically investigated via both in situ synchrotron X‐ray diffraction and density functional theory calculations. The results show that the sodiation and desodiation are single‐phase‐transition processes with two 1D sodium paths, which facilitates fast ionic diffusion. A small volume change, nearly 100% first‐cycle Coulombic efficiency, and a pseudocapacitance contribution are also demonstrated. This research indicates that this new compound could be a potential competitor for other iron‐based cathode electrodes for application in large‐scale Na rechargeable batteries. 相似文献
999.
Topological Quantum Phase Transition and Superconductivity Induced by Pressure in the Bismuth Tellurohalide BiTeI 下载免费PDF全文
Yanpeng Qi Wujun Shi Pavel G. Naumov Nitesh Kumar Raman Sankar Walter Schnelle Chandra Shekhar Fang‐Cheng Chou Claudia Felser Binghai Yan Sergey A. Medvedev 《Advanced materials (Deerfield Beach, Fla.)》2017,29(18)
A pressure‐induced topological quantum phase transition has been theoretically predicted for the semiconductor bismuth tellurohalide BiTeI with giant Rashba spin splitting. In this work, evolution of the electrical transport properties in BiTeI and BiTeBr is investigated under high pressure. The pressure‐dependent resistivity in a wide temperature range passes through a minimum at around 3 GPa, indicating the predicted topological quantum phase transition in BiTeI. Superconductivity is observed in both BiTeI and BiTeBr, while resistivity at higher temperatures still exhibits semiconducting behavior. Theoretical calculations suggest that superconductivity may develop from the multivalley semiconductor phase. The superconducting transition temperature, Tc, increases with applied pressure and reaches a maximum value of 5.2 K at 23.5 GPa for BiTeI (4.8 K at 31.7 GPa for BiTeBr), followed by a slow decrease. The results demonstrate that BiTeX (X = I, Br) compounds with nontrivial topology of electronic states display new ground states upon compression. 相似文献
1000.
Yutsung Tsai Zhaodong Chu Yimo Han Chih‐Piao Chuu Di Wu Alex Johnson Fei Cheng Mei‐Yin Chou David A. Muller Xiaoqin Li Keji Lai Chih‐Kang Shih 《Advanced materials (Deerfield Beach, Fla.)》2017,29(41)
Semiconductor heterostructures have played a critical role as the enabler for new science and technology. The emergence of transition‐metal dichalcogenides (TMDs) as atomically thin semiconductors has opened new frontiers in semiconductor heterostructures either by stacking different TMDs to form vertical heterojunctions or by stitching them laterally to form lateral heterojunctions via direct growth. In conventional semiconductor heterostructures, the design of multijunctions is critical to achieve carrier confinement. Analogously, successful synthesis of a monolayer WS2/WS2(1?x )Se2x /WS2 multijunction lateral heterostructure via direct growth by chemical vapor deposition is reported. The grown structures are characterized by Raman, photoluminescence, and annular dark‐field scanning transmission electron microscopy to determine their lateral compositional profile. More importantly, using microwave impedance microscopy, it is demonstrated that the local photoconductivity in the alloy region can be tailored and enhanced by two orders of magnitude over pure WS2. Finite element analysis confirms that this effect is due to the carrier diffusion and confinement into the alloy region. This work exemplifies the technological potential of atomically thin lateral heterostructures in optoelectronic applications. 相似文献