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1.
Mina NeghabiAbbas Behjat 《Current Applied Physics》2012,12(2):597-601
Organic light emitting diodes (OLEDs) of ITO/PEDOT:PSS/TPD:Alq3:C60/Al with different C60 concentrations (0-6.0 wt.%) have been fabricated. The physical parameters including electrical and optical properties of the samples have been measured by Luminance-current-voltage (L-I-V) characteristics and optical absorbance. The current-voltage characteristics indicate that field-emission tunneling injection dominates in the diodes at high applied voltages. It is found that with increasing the concentration of C60, the injection barrier for holes slightly reduces and the hole’s mobility increases over two orders of magnitude. Also, electroluminescence enhances with the presence of C60 in the blend; optimum current efficiency occurs at 3 wt% C60. The method provides a simple way of increasing the efficiency of OLEDs. 相似文献
2.
Saturation of extrinsic photoconductivity in GaP:N(Zn, Te) diodes could be achieved by excitation with a TEA-CO2-laser. At wavelengths in the 10 m range intensities of several 100 kW/cm2 being near the damage threshold were applied. Carrier lifetimes of 60 ps at 4.2 K and 200 ps at 77 K could be estimated. The only conceivable mechanism explaining these short time constants is the capture of infrared excited holes by ionized shallow acceptors in the highly compensated p-side of the diode. 相似文献
3.
本文报道把热能直接转换电能的热磁发电技术所用一级相变新材料Mn1.2Fe0.8P0.4Si0.6的磁性和热磁发电性能.用高能球磨机械合金化技术和固相烧结合成方法制备了Mn1.2Fe0.8P0.4Si0.6化合物.磁性测量结果表明,该化合物呈现从铁磁状态变为顺磁状态的一级相变,居里温度为337K,并伴随巨大的磁化强度的变化.根据该材料的这一特性,设计制作了热磁发电演示装置,测定了热流引起材料的相变而产生的电流,并研究了固定磁场中热致磁转变产生的电流随热流温度和样品质量的变化.研究结果表明Mn1.2Fe0.8P0.4Si0.6化合物具有很好的热磁发电性能,可作为热磁发电材料. 相似文献
4.
In deep level transient spectroscopy (DLTS) exponentiality of level population changes in thermal emission as well as in capture processes is assumed. This is however, contrary to what is often observed in experiment. In this paper a model for interpretation of DLTS data in the case of non-exponential capture of electrons is proposed. It is assumed that the height of the capture of carrier changes locally according to the Gaussian distribution This model is applied to the case of deep electron trap with thermal activation energy equal to ΔEB = 0.39 eV, observed in VPE GaAs0.62P0.38. Te. This model provides a capture barrier as well as a capture cross-section which are different from the ones predicted by the exponential transient model i.e., the ones derived from the slope of capacitance changes due to the filling pulse versus pulse duration at very short times. 相似文献
5.
Minority carrier lifetimes in nitrogen implanted GaAs1-x
P
x
(x=0.4; 0.65) were measured at 77K by an optical phase shift method as a function of nitrogen dose and annealing temperature
in order to investigate the dependence of the lifetime on the concentration of nitrogen isoelectronic traps. A large increase
in the lifetime was observed after nitrogen implantation followed by annealing at and above 800°C. The maximum lifetimes were
22ns for GaAs0.35P0.65 and 6.7 ns for GaAs0.6P0.4. They were obtained by implantation to a dose of 5×1013 cm−2 in GaAs0.35P0.65 and 1013 cm−2 in GaAs0.6P0.4. The lifetime after nitrogen implantation followed by annealing was longer by a factor of 6–7 than that of the unimplanted
sample. 相似文献
6.
A. Agliolo Gallitto M. Guccione M. Li Vigni 《Physica C: Superconductivity and its Applications》2000,330(3-4):141-149
We report a detailed investigation of harmonic generation at microwave frequencies in Ba0.6K0.4BiO3 crystals. Second- and third-harmonic signals are investigated as a function of temperature, external magnetic field and input power level, at temperatures close to Tc. The experimental data are discussed in the framework of a phenomenological theory, based on the two-fluid model, which assumes that the microwave and the static fields, penetrating the sample within the penetration depth, perturb the partial concentrations of the normal and condensate fluids. We show that the enhanced nonlinear effects detected near Tc in Ba0.6K0.4BiO3 and YBa2Cu3O7 crystals may have the same origin. However, in order to account for the experimental data of Ba0.6K0.4BiO3, one needs to involve a distribution of Tc over the crystal. 相似文献
7.
Xia Liu Hang Song Hong Jiang Lianzhen Cao Xiaojuan Sun Yiren Chen 《Solid State Communications》2011,151(12):904-907
InAs0.6P0.4 epilayers grown on InP (100) substrates using two-step growth method by LP-MOCVD were investigated. A low temperature (450 °C) In0.18Ga0.82As buffer layer was introduced to relax the lattice mismatch between the InAs0.6P0.4 epilayer and the InP substrate. The influence of In0.18Ga0.82As buffer layer thickness and epilayer’s growth temperature on crystalline quality of InAs0.6P0.4 epilayer was characterized by Scanning electron microscopy, X-ray diffraction, Hall measurements, Transmission electron microscopy and Photoluminescence. The experimental results showed that the crystalline quality of InAs0.6P0.4 epilayers could be greatly improved by optimizing the In0.82Ga0.18As buffer layer thicknesses and the InAs0.6P0.4 epilayer’s growth temperatures. It was found that, when In0.82Ga0.18As buffer layer thickness was 100 nm and InAs0.6P0.4 epilayer’s growth temperature was 580 °C, the InAs0.6P0.4 epilayer exhibited the best crystalline quality and properties. 相似文献
8.
Nonpolar a-plane light-emitting diode with an in-situ SiNx interlayer on r-plane sapphire grown by metal-organic chemical vapour deposition
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We report on the growth and fabrication of nonpolar a-plane light emitting diodes with an in-situ SiNx interlayer grown between the undoped a-plane GaN buffer and Si-doped GaN layer. X-ray diffraction shows that the crystalline quality of the GaN buffer layer is greatly improved with the introduction of the SiNx interlayer. The electrical properties are also improved. For example, electron mobility and sheet resistance are reduced from high resistance to 31.6 cm2/(V·s) and 460 Ω/口 respectively. Owing to the significant effect of the SiNx interlayer, a-plane LEDs are realized. Electroluminescence of a nonpolar a-plane light-emitting diode with a wavelength of 488nm is demonstrated. The emission peak remains constant when the injection current increases to over 20 mA. 相似文献
9.
The absorption and photoluminescent spectra of nitrogen doped GaAs1?χPχ epitaxial layers were studied in the alloy composition range 0.58 ? χ ? 0.77. The structure in the absorption and luminescent spectra are analysed. 相似文献
10.
The interaction of deuterium with Ce0.6Zr0.4O2, synthesised by a co-precipitation technique, is discussed on the basis of the sample's bulk and surface composition and the presence of trace amounts of silicon. Redox cycling resulted in surface cerium enrichment, which, however, only moderately affected the interaction of the material with D2. Addition of a trace amount of chloride ion to the oxide surface promoted both H/D scrambling and vacancy creation. Chloride ion was also found to prevent the surface cerium enrichment induced by redox cycling. 相似文献
11.
有机异质结连接层因其具有良好的透光性能、制备工艺和有机电致发光器件(Organic light-emitting diodes,OLEDs)完全兼容的优点,被广泛应用于叠层OLEDs中。在叠层OLEDs中,连接层可产生电荷,其工作性能是影响叠层OLEDs性能的关键因素之一。为了获得最佳性能的有机异质结连接层,本文制备了结构为glass/ITO/tris(8-hydroxyquinoline) aluminum(Alq_3)(60 nm)/C_(60)(x nm)/CuPc(y nm)/N,N′-bis(naphthalen-1-yl)-N,N′-bis (phenyl)-be-nzidine(NPB)(40 nm)/Al (100 nm)的有机器件,直接获得了有机异质结连接层C_(60)/CuPc产生的器件电流。通过结构优化发现,结构为C_(60)(30 nm)/CuPc(10 nm)的连接层具有最强的电荷产生能力,并对最优结构连接层形成的物理机制作了合理的解释.本文获得的结果可为理解有机异质结连接层工作机理以及制备高性能叠层OLEDs提供理论基础。 相似文献
12.
13.
正如人们所知, 可以通过电场或者设计非对称的半导体异质结构来调控体系的结构反演不对称性(SIA)和Rashba自旋劈裂. 本文研究了Al0.6Ga0.4N/GaN/Al0.3Ga0.7N/Al0.6Ga0.4N量子阱中第一子带的Rashba 系数和Rashba自旋劈裂随Al0.3Ga0.7N插入层(右阱)的厚度ws以及外加电场的变化关系, 其中GaN层(左阱)的厚度为40-ws Å. 发现随着ws的增加, 第一子带的Rashba系数和Rashba自旋劈裂首先增加, 然后在ws>20 Å 时它们迅速减小, 但是ws>30 Å时Rashba自旋劈裂减小得更快, 因为此时kf也迅速减小. 阱层对Rashba系数的贡献最大, 界面的贡献次之且随ws变化不是太明显, 垒层的贡献相对比较小. 然后, 我们假ws=20 Å, 发现外加电场可以很大程度上调制该体系的Rashba系数和Rashba自旋劈裂, 当外加电场的方向同极化电场方向相同(相反)时, 它们随着外加电场的增加而增加(减小). 当外加电场从-1.5×108 V·m-1到1.5×108 V· m-1变化时, Rashba系数随着外加电场的改变而近似线性变化, Rashba自旋劈裂先增加得很快, 然后近似线性增加, 最后缓慢增加. 研究结果表明可以通过改变GaN层和Al0.3Ga0.7N层的相对厚度以及外加电场来调节Al0.6Ga0.4N/GaN/Al0.3Ga0.7N/Al0.6Ga0.4N量子阱中的Rashba 系数和Rashba自旋劈裂, 这对于设计自旋电子学器件有些启示. 相似文献
14.
Miniature optically pumped cavity NH3 Far-infrared laser was studied theoretically, with the length of the FIRL cavity as short as 1.5cm, the dependences of FIRL output power and laser lineshape on operating gas pressure and output coupling condition, and on the effect of laser line saturation broadening were calculated.Supported by the National Natural Science Foundation of China. 相似文献
15.
Zn1−xMnxFe2O4 (x = 0, 0.2 and 0.4) nanomaterials were synthesized by sol–gel citrate method and studied structural and gas sensing properties. The structural characteristics of synthesized nanomaterials were studied by X-ray diffraction measurement (XRD) and transmission electron microscope (TEM). The results revealed that the particle size is in the range of 30–35 nm for Mn–Zn ferrite with good crystallinity. The gas sensing properties were studied towards reducing gases like LPG, CH4, CO and ethanol and it is observed that Mn–Zn ferrite shows high response to ethanol at relatively lower operating temperature. The Zn0.6Mn0.4Fe2O4 nanomaterial shows better sensitivity towards ethanol at an operating temperature 300 °C. Incorporation of 1.5 wt.% Pd improved the sensitivity, selectivity, response time and reduced the operating temperature from 300 °C to 230 °C for ethanol sensor. The response time of 200 ppm ethanol in air is about 10s. 相似文献
16.
Photoluminescence enhancement by localized surface plasmons in AlGaN/GaN/AlGaN double heterostructures
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Alexander Y. Polyakov Jin‐Hyeon Yun Haeng‐Keun Ahn Alexander S. Usikov Eugene B. Yakimov Sergey A. Tarelkin Nikolai B. Smirnov Kirill D. Shcherbachev Heikki Helava Yuri N. Makarov Sergey Yu Kurin Sergey I. Didenko Boris P. Papchenko In‐Hwan Lee 《固体物理学:研究快报》2015,9(10):575-579
Double heterostructures AlGaN/GaN/AlGaN grown by hydride vapor phase epitaxy and designed for use as light emitting diodes for 360 nm wavelength were patterned by shallow nanoholes and injected with Ag/SiO2 or Al nanoparticles. A 1.8 times increase in the photoluminescence and microcathodoluminescence signal from the GaN active region was observed for 100 nm diameter Al nanoparticles, the efficiency decreased compared to the reference planar samples for small Al nanoparticles of 30–40 nm diameter, and a moderate increase of 1.2 times was detected for Ag/SiO2 nanoparticles. The observed phenomena are explained by the GaN emitter coupling with localized surface plasmons produced by metallic nanoparticles. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献
17.
利用热压法将TiO2微粒掺入至YAG:Ce荧光粉和硅树脂中制备出远程荧光粉膜并封装成白光发光二极管(LED)器件, 通过荧光粉相对亮度仪、双积分球测试系统和可见光光谱分析系统对样品的光色性能及机理进行了研究. 结果表明: TiO2的散射效应能够显著提高蓝光的利用率和黄光的透射强度, 白光LED器件的光通量在TiO2浓度为0.966 g/cm3 时达到最高值415.28 lm(@300 mA, 9.3 V), 提高了8.15%, 相关色温从冷白6900 K逐渐变化至暖白3832 K. TiO2的掺入不仅提高了远程荧光粉膜的发射强度和白光LED器件的光通量, 同时能调控其相关色温. 相似文献
18.
在发光二极管(LED)的透明电极层上制作单层六角密排的聚苯乙烯(polystyrene, PS) 纳米球, 研究提高GaN基蓝光LED的出光效率. 采用自组装的方法在透明电极铟锡氧化物层上制备了直径分别约为250, 300, 450, 600和950 nm的PS纳米球, 并且开展了电致发光的研究. 结果表明, 在LED的透明电极层上附有PS纳米球能有效地提高LED的出光效率; 当PS纳米球的直径与出射光的波长比较接近时, LED的出光效率最优. 与参考样品相比, 在20 mA和150 mA工作电流下, 附有PS纳米球的样品的发光效率分别增加1.34倍和1.25倍. 三维时域有限差分方法计算表明, 该出光增强主要归因于附有PS纳米球的LED结构可以增大LED结构的光输出临界角, 从而提高LED的出光效率. 因此, 这是一种低成本的实现高效率LED的方法. 相似文献
19.
We report a study of the magnetotransport properties of the Co2Cr0.6Fe0.4Al Heusler alloy grown by means of the arc-melting technique. X-ray diffraction and energy dispersive X-ray spectroscopy have been used to analyze the crystallographic structure and the sample stoichiometry. Temperature-dependent magnetization measurements have been carried out in the range 300-850 K. Co2Cr0.6Fe0.4Al is theoretically predicted to have full positive spin polarization at the Fermi level, and as a consequence its spin-dependent transport properties are being intensively studied. Low field magnetoresistance exceeding 30% has been observed very recently in Co2Cr0.6Fe0.4Al compact pellets. We have performed magnetoresistance and magnetostriction measurements in both the as-grown alloy and compact pellets made of mechanically milled Co2Cr0.6Fe0.4Al. The as-grown and the milled sample show negligible anisotropic magnetostriction (25 μst at saturation), whilst only the milled sample exhibits magnetoresistance (0.65% at 300 K). These results permit us to discard the magnetostrictive effects as the magnetoresistance source. 相似文献
20.
Light‐Emitting Diodes: Highly Efficient and Stable Luminescence from Microbeans Integrated with Cd‐Free Quantum Dots for White‐Light‐Emitting Diodes (Part. Part. Syst. Charact. 10/2015)
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Wei Chen Kai Wang Junjie Hao Dan Wu Shang Wang Jing Qin Chen Li Wanqiang Cao 《Particle & Particle Systems Characterization》2015,32(10):917-917