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高温超导体的转变温度Tc 正沿着三条路线被提高 .其一是铜氧化合物超导体 ,从 1986年发现镧系的LSCO和钇系的YBCO ,至 1993年Tl 2 2 0 1超导体的Tc 已达到 133K ,而在加压的条件下 ,Hg系的Tc 可达 16 4K .其二是轻主族元素化合物 ,以 2 0 0 1年发现的Tc~ 4 0K的MgB2 为代表 .其三是有机超导体 ,1979年发现的第一个电荷转移盐有机超导体 ,其Tc 在 1K以下 ,后来这类材料的Tc 提高到约10K[1,2 ] .1991年在碱金属A掺杂的A3 C60 大块超导体中 ,观察到的Tc 为 18K .近年来 ,美国贝尔实验室等一些研究机构 … 相似文献
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激光分子束外延制备的BaTiO3及c取向YBa2Cu3O7-δ薄膜的生长模式 总被引:1,自引:0,他引:1
用反射式高能电子衍射(RHEED) 和原子力显微镜(AFM) 研究激光分子束制备的铁电BaTiO3 和高Tc 超导c 取向Y1Ba2Cu3O7 薄膜的生长模式,BTO 铁电薄膜是原子级平整的层状生长模式;c 取向YBCO 超导薄膜是SK生长模式 当薄膜厚度小于5 个原胞时,层状生长,然后是台阶岛状生长.处理SrTiO3 基片表面可以改变c 取向YBCO薄膜的生长模式 相似文献
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氢吸附对掺杂SnO2薄膜电子结构的影响 总被引:1,自引:0,他引:1
应用XPS技术研究了掺杂SnO2薄膜吸附H2前后电子结构的变化,观测到掺杂到Sb和Pd化学状态明显改变,发现掺杂剂Sb对SnO2薄膜Femi能级的影响;同时,分析了掺杂Sb和Pd对SnO2薄膜气敏特性的影响机制。 相似文献
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利用紫外脉冲激光源淀积生长氧化物薄膜的技术,我们在SiTiO3衬底上成功地外延生长了超薄超导YBa0.2Cu3O7薄膜样品.样品YBa0.2Cu3O7层厚度分别为2.4nm至10.8nm(二至九个原胞).四端引线电阻法测量了样品的电阻温度关系和超导转变.超导零电阻温度分别为16K至81K.超薄超导薄膜样品显示当YBa0.2Cu3O7层厚度达到和超过四个原胞层厚(9.6nm)时,厚度变化对样品超导零电阻转变的影响并不十分明显.实验观察到YBa0.2Cu3O7层厚度对样品超导零电阻温度和超导起始转变影响不同.这说明样品中的缺陷对样品性能有着不容忽视的影响.超薄YBa0.2Cu3O7超导薄膜样品的成功制备为进一步的研究提供了有利条件. 相似文献
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本首次报道了用离子注入的方法成功地获得了汞系超导体Hg-1223在SrTiO3衬底上的薄膜材料。LSS理论估算薄膜厚度约为250-350埃。交流磁化率的测量表明其超导转变温度为118K。 相似文献
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有机电致发光器件及其稳定性问题 总被引:2,自引:0,他引:2
有机发光二极管(OLEDs)即将实用化,但其稳定性仍是急需解决的关键问题。文章简要综述了OLEDs及其稳定性问题,着重从OLEDs的失效过程、水汽和氧气、电极材料及其界面对OLEDs稳定性的影响、有机材料本身的稳定性等方面讨论了OLEDs的稳定性。 相似文献
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Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide 总被引:1,自引:0,他引:1
Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs. 相似文献
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A review of schemes for multiple access in fiber optic networks shows that a hybrid of wavelength and code division multiple access (WCDMA) combines the best features of both. In particular, the hybrid scheme retains the large information carrying capacity of wavelength division multiple access (WDMA) and flexibility of code division multiple access (CDMA). In this paper WDMA, optical CDMA (OCDMA), and WCDMA networks are discussed. In OCDMA networks, concept of incoherent and coherent coding including inverse decoding and matched filter is introduced. The delay performance of both WDMA and WCDMA networks, under the simple suboptimum access protocols based on cyclic search, is computed. It has been shown quantitatively that tuning delay significantly affects the delay performance of both WDMA and WCDMA networks. Futhermore, delay performance of WCDMA networks is always better than the WDMA networks for the same tuning delay, load, and number of users. 相似文献
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S. G. Nedel’ko M. A. Krysyuk A. L. Apanasenko L. N. Lymarenko Z. T. Moroz 《Journal of Applied Spectroscopy》1997,64(1):55-61
Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped
with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly
described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation
(5.5·104 Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum
cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics
of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure
crystals is analyzed (preliminarily).
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997. 相似文献
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A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output. 相似文献
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The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper. 相似文献
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We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed. 相似文献
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Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell. 相似文献
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A versatile and low-cost single-beam self-referenced phase-sensitive surface plasmon resonance(SPR)sensing system with ultra-high resolution performance is presented.The system exhibits a root-mean-square phase fluctuation of ±0.0028.over a period of 45 min.i.e.a resolution of±5.2×10-9 refractive index units.The enhanced performance has been achieved through the incorporation of three design elements:a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected,a differential measurement scheme to eliminate spurious signals not related to the sensor response,and the elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulato .Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional fluorescence-based techniques. 相似文献
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Ta2O5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition.The effects of SiO2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated.The results show that SiO2 protective layers exert little influence on the electric field intensity(EFI)distribution,microstructure and microdefect density but increase the absorption slightly.Annealing iS effective on decreasing the microdefect density and the absorption of the films.Both SiO2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT.Moreover,the maximal LIDT of Ta2O5 films is achieved by the combination of SiO2 protective layers and annealing. 相似文献