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51.
Temperature-dependent photoluminescence (PL) and time resolved photoluminescence (TRPL) are performed to study the PL characteristics and carrier transfer mechanism in asymmetric coupled InGaN/GaN multiple quantum wells (AS-QWs). Our results reveal that abnormal carrier tunnelling from the wide quantum well (WQW) to the narrow quantum well (NQW) is observed at temperature higher than about lOOK, while a normal carrier tunnelling from the NQW to the WQW is observed at temperature lower than 100 K. The reversible carrier tunnelling between the two Q Ws makes it possible to explore new types of temperature sensitive emission devices. It is shown that PL internal quantum efficiency (IQE) of the NQW is enhanced to about 46% due to the assistant of the abnormal carrier tunnelling. 相似文献
52.
A transparent electromagnetic-shielding film based on one-dimensional metal–dielectric periodic structures 下载免费PDF全文
In this study, we designed and fabricated optical materials consisting of alternating ITO and Ag layers. This approach is considered to be a promising way to obtain a light-weight, ultrathin and transparent shielding medium, which not only transmits visible light but also inhibits the transmission of microwaves, despite the fact that the total thickness of the Ag film is much larger than the skin depth in the visible range and less than that in the microwave region. Theoretical results suggest that a high dielectric/metal thickness ratio can enhance the broadband and improve the transmittance in the optical range. Accordingly, the central wavelength was found to be red-shifted with increasing dielectric/metal thickness ratio. A physical mechanism behind the controlling transmission of visible light is also proposed. Meanwhile, the electromagnetic shielding effectiveness of the prepared structures was found to exceed 40 dB in the range from 0.1 GHz to 18 GHz, even reaching up to 70 dB at 0.1 GHz, which is far higher than that of a single ITO film of the same thickness. 相似文献
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采用水热法制备了具有二维层状结构的钙钒青铜(CaxV2O5·nH2O, CVO)水系锌离子电池钒基正极材料, 并通过调控前驱体溶液中碳纳米管的含量, 得到3种钙钒青铜/碳纳米管复合材料(CVO@CNTs). 利用X射线衍射、 热重分析、 扫描电子显微镜和透射电子显微镜等对材料进行了表征. 结果表明, 所制备的CVO呈纳米带形貌, 长约十几微米, 宽约几百纳米, 选区电子衍射测试表明所得材料为单晶结构. 循环伏安测试结果表明, CVO和CVO@CNTs均具有多个氧化还原峰, 储锌机制包括赝电容行为和电池行为. 在放电倍率1C(1C=300 mA/g)测试条件下, CVO纳米带比容量稳定在210.1 mA·h/g; 与CNTs复合后, CVO@CNTs复合材料的电荷转移阻抗降低, 在相同测试条件下表现出更高的比容量和优异的倍率性能. 其中, CVO@CNTs-40表现出最高的比容量, 在1C倍率测试条件下的比容量可达274.3 mA·h/g, 即使在20C的测试条件下放电比容量仍可达85.2 mA·h/g, 且循环1000次后容量保持率能达到92%. 相似文献
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本文应用全对称群的Dirac理论计算了分子H_2X(X=O、S、Se)的结构,并与非相对论的结果比较.对比相对论和非相对论的结果,所得到的分子几何差异不大;而所计算的能量,相对论的比非相对论的要低,并能量随质量增加而降低;相对论值的极化率(A~3)和偶极矩更接近实验值.分子的电性状态为费密子共群的不可约表示E_1,明显地体现不可约表示E1的效应.所以,特别对重元素分子,更要应用相对论方法. 相似文献
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Using the molecular dynamics method, the stability of small He-vacancy clusters is studied under the condition of the high He and low vacancy densities. The result shows that there is a competition between He atoms detrapped and self-interstitial atoms (SIAs) emitted during the clustering of He atoms. When the He number is above a critical value of 9, the SIA emission is predominant. The SIA emission can result in deep capture of He atoms since the binding energy of He to a He-vacancy cluster is increased with the number of SIAs created. The cluster thus grows up. In addition, more SIAs are created when the temperature is elevated. The average volume of a He atom is increased. The cluster expansion takes place at high temperature. 相似文献
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单片机在测量声速实验中的应用郭立群,李将录,万新(哈尔滨师范大学物理系150080)(哈尔滨塑料十二厂)一、引言目前各级各类学校的普通物理实验课普遍开设声速测量实验.声速测量的一般方法有行波法、驻波法、共鸣法等间接测量方法.这些方法都很巧妙,但误差较... 相似文献