排序方式: 共有42条查询结果,搜索用时 15 毫秒
11.
报道了一种新型的CdGeAs2晶体择优腐蚀剂,配方为:H2O2(30;): NH4OH(含NH325;-28;): NH4Cl(5mol/L): H2O=1 mL: 1.5 mL: 1.5 mL: 2 mL.将经机械研磨、物理抛光和溴甲醇化学抛光处理后的表面平整无划痕的CdGeAs2晶片,在40 ℃下超声振荡腐蚀数分钟,采用金相显微镜和SEM进行蚀坑观察.结果表明,新型腐蚀剂对CdGeAs2晶体(204)和(112)晶面择优腐蚀效果显著,蚀坑取向一致,具有很强的立体感;(204)晶面蚀坑呈三角锥形,(112)晶面蚀坑呈五边形,从晶体结构上对蚀坑形成机理进行了分析讨论. 相似文献
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Control of chaos by a delayed continuous feedback is studied experimentally in a gas discharge plasma. The power spectrum, the maximum of Lyapunov exponents and the time series of the signals all indicate that the period-1 unstable periodic orbit is controlled successfully. The dependence of the control on the delay time and the feedback gain as well as the strength of white noise is also investigated in detail. The experimental results show that the scaling index of the control versus the strength of white noise is 1.995, which is very close to that obtained from the simple logistic map. 相似文献
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三山岛金矿F3断裂带的水文地质工程地质特征及灾害防治 总被引:1,自引:0,他引:1
本文对三山岛金矿F3断裂带的构造、岩性和水动力学特征进行了研究,对矿坑开挖中的突水和坑道碎屑流的成因做了探讨,并在水文地质结构、水化学、水同位素及水文地热学的综合研究基础上,对未来的二期井下工程开挖中可能出现的工程地质问题进行了预测,提出了防治方案。 相似文献
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里德堡原子具有大的极化率、低的场电离阈值和大的电偶极矩,对外部电磁场十分敏感,可以用来测量电场强度特别是微波电场的强度. 利用里德堡原子的量子干涉效应(电磁诱导透明和Autler-Townes效应)测量微波电场强度的灵敏度远高于传统采用偶极天线测量微波电场的灵敏度. 此外,里德堡原子电场计 可以溯源到标准物理量,不需要额外校准; 采用玻璃探头,对待测电场干扰少; 灵敏度也不依赖于探头的物理尺寸. 同时,该电场计还可以实现对微波电场的偏振方向的测量, 实现亚波长和近场区域电场成像与测量. 通过选择不同的里德堡能级,可以实现1-500 GHz超宽频段范围内微波电场强度的测量. 主要综述基于里德堡原子的电场精密测量研究, 详细介绍了里德堡原子电场计的原理与实验进展, 并简单讨论了其发展方向. 相似文献
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Analysis of tensile strain enhancement in Ge nano-belts on an insulator surrounded by dielectrics 下载免费PDF全文
Ge nano-belts with large tensile strain are considered as one of the promising materials for high carrier mobility metal- oxide-semiconductor transistors and efficient photonic devices. In this paper, we design the Ge nano-belts on an insulator surrounded by Si3N4 or SiO? for improving their tensile strain and simulate the strain profiles by using the finite difference time domain (FDTD) method. The width and thickness parameters of Ge nano-belts on an insulator, which have great effects on the strain profile, are optimized. A large uniaxial tensile strain of 1.16% in 50-nm width and 12-nm thickness Ge nano-belts with the sidewalls protected by Si3N4 is achieved after thermal treatments, which would significantly tailor the band gap structures of Ge-nanobelts to realize the high performance devices. 相似文献
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性能优越的Si基高效发光材料与器件的制备一直是Si基光电集成电路中最具挑战性的课题之一.Si基Ge材料不仅与成熟的硅工艺相兼容,而且具有准直接带特性,被认为是实现Si基激光器最有希望的材料.对Si基Ge材料N型掺杂的研究有利于提示出其直接带发光增强机理.本文研究了N型掺杂Si基Ge材料导带电子的晶格散射过程.N型掺杂Si基Ge材料具有独特的双能谷(Γ能谷与L能谷)结构,它将通过以下两方面的竞争关系提高直接带导带底电子的占有率:一方面,处于Γ能谷的导带电子通过谷间光学声子的散射方式散射到L能谷;另一方面,处于L能谷的导带电子通过谷内光学声子散射以及二次谷间光学声子散射或者直接通过谷间光学声子散射的方式跃迁到Γ能谷.当掺杂浓度界于10~(17)cm~(-3)到10~(19)cm~(-3)时,适当提高N型掺杂浓度有利于提高直接带Γ能谷导带底电子占有率,进而提高Si基Ge材料直接带发光效率. 相似文献
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以双介孔分布MCM-41分子筛为载体,采用等体积浸渍法制备了钴基催化剂,并考察了还原-氧化预处理方式对催化剂结构及费托合成催化性能的影响。新鲜催化剂经预处理之后,XRD结果显示钴物种主要以单质钴形式存在,且主要以面心立方钴晶型出现,晶粒粒径由原来的8.4nm增加到22.6nm,由于晶粒粒径的增大,拉曼峰呈现蓝移特征。SEM及TEM表征表明,预处理后催化剂中钴物种在载体中有较好的分散性。H2-TPR结果表明,新鲜催化剂经还原-氧化预处理后钴物种的还原温度降低,钴物种-载体间作用力增强。费托合成反应结果显示,经预处理后催化剂较新鲜催化剂活性低,甲烷选择性提高,但C5~18的选择性明显提高,尤其是C5~11的选择性可达到新鲜催化剂的两倍。 相似文献
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Plasmon-induced transparency effect in hybrid terahertz metamaterials with active control and multi-dark modes 下载免费PDF全文
Yuting Zhang 《中国物理 B》2022,31(6):68702-068702
We numerically demonstrate a photo-excited plasmon-induced transparency (PIT) effect in hybrid terahertz (THz) metamaterials. The proposed metamaterials are regular arrays of hybrid unit cells composed of a metallic cut wire and four metallic split-ring resonators (SRRs) whose gaps are filled with photosensitive semiconductor gallium arsenide (GaAs) patches. We simulate the PIT effect controlled by external infrared light intensity to change the conductivity of GaAs. In the absence of photo excitation, the conductivity of GaAs is 0, thus the SRR gaps are disconnected, and the PIT effect is not observed since the dark resonator (supported by the hybrid SRRs) cannot be stimulated. When the conductivity of GaAs is increased via photo excitation, the conductivity of GaAs can increase rapidly from 0 S/m to 1×106 S/m and GaAs can connect the metal aluminum SRR gaps, and the dark resonator is excited through coupling with the bright resonator (supported by the cut wire), which leads to the PIT effect. Therefore, the PIT effect can be dynamically tuned between the on and off states by controlling the intensity of the external infrared light. We also discuss couplings between one bright mode (CW) and several dark modes (SRRs) with different sizes. The interference analytically described by the coupled Lorentz oscillator model elucidates the coupling mechanism between one bright mode and two dark modes. The phenomenon can be considered the result of linear superposition of the coupling between the bright mode and each dark mode. The proposed metamaterials are promising for application in the fields of THz communications, optical storage, optical display, and imaging. 相似文献