共查询到18条相似文献,搜索用时 93 毫秒
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石墨烯是一种特殊的二维材料,其独特的能带结构允许人们通过电场来调控其载流子的类型和浓度,因此,在构建双极型纳米电子器件方面具有潜在应用前景.本文基于紧束缚格点模型,利用非平衡格林函数方法及Landauer-Büttiker公式,研究了石墨烯p-n结在磁场中的电输运热耗散问题.在强磁场作用下,结的两边均处于量子霍尔相,存在拓扑保护的手性边缘态.直觉上,这种拓扑保护的手性边缘态应当是无热耗散的.但本文研究发现,当有耗散源时,尽管手性边缘态受到拓扑保护,热耗散却依然可以发生.对于完美的石墨烯,单极结输运时热耗散发生在体系边缘;偶极结输运时在体系边缘和结的界面处均可以发生热耗散.当无序存在时,无论单极结还是偶极结,无序均能增强热耗散.此外,本文还研究了不同位置处的电子能量分布,发现热耗散是否发生只取决于电子是否处于非平衡分布.这些结果表明拓扑只能保护电子的传播方向,却不能禁止热耗散的发生. 相似文献
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基于正在建设的大连自由电子激光装置,研究了基因算法在注入器优化设计中的系统应用。与传统的注入器优化方法相比较,基因算法在多变量、多目标注入器优化问题中具有优化效率高、优化结果精确的优势;通过采用权重因子的方法将多目标问题转化为单目标优化问题,大大简化了基因算法优化流程;光阴极注入器对束流稳定性要求严格,通过基因算法优化使束流的到达时间抖动控制到150 fs,满足束流稳定性的要求。 相似文献
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不同Cs、O电流比激活对GaAs光阴极灵敏度和稳定性的影响 总被引:1,自引:0,他引:1
鉴于不同的铯氧电流激活GaAs光阴极时会对激活过程和结果产生不同的影响,从而影响GaAs光阴极的灵敏度和稳定性.以固定铯源电流,改变氧源电流的方式获取不同铯、氧电流比,激活同类GaAs光阴极,得到了3组实验数据.对数据进行分析,结果表明:同类光阴极在相同条件下激活时,光电流出现的时间几乎一致,并且首个光电流峰值也非常接近;激活时ICs/IO=1.07是目前获得高灵敏度、高稳定性GaAs光阴极的最佳电流比,而ICs/IO=1.10时光阴极灵敏度低但稳定性好,ICs/IO=1.03时光阴极灵敏度高但稳定性差.双偶极层模型认为Cs、O激活后GaAs表面形成了稳定均匀的GaAs-O-Cs:Cs-O-Cs双偶极层,并达到了负电子亲和势,这一点与实验数据的分析结果相一致.该方法可用于提高GaAs光阴极灵敏度和稳定性. 相似文献
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Numerical simulation of the magnetoresistance effect controlled by electric field in p–n junction 下载免费PDF全文
The magnetoresistance effect of a p–n junction under an electric field which is introduced by the gate voltage at room temperature is investigated by simulation. As auxiliary models, the Lombardi CVT model and carrier generationrecombination model are introduced into a drift-diffusion transport model and carrier continuity equations. All the equations are discretized by the finite-difference method and the box integration method and then solved by Newton iteration.Taking advantage of those models and methods, an abrupt junction with uniform doping is studied systematically, and the magnetoresistance as a function of doping concentration, SiO_2 thickness and geometrical size is also investigated. The simulation results show that the magnetoresistance(MR) can be controlled substantially by the gate and is dependent on the polarity of the magnetic field. 相似文献
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Dependences of spin polarization on the control parameters in the spin-polarized injection through the magnetic p-n junction 下载免费PDF全文
Effective spin-polarized injection from magnetic semiconductor (MS)
to nonmagnetic semiconductor (NMS) has been highlighted in recent
years. In this paper we study theoretically the dependence of
nonequilibrium spin polarization (NESP) in NMS during spin-polarized
injection through the magnetic p-n junction. Based on the theory in
semiconductor physics, a model is established and the boundary
conditions are determined in the case of no external spin-polarized
injection and low bias. The control parameters that may influence the
NESP in NMS are indicated by calculating the distribution of spin
polarization. They are the doping concentrations, the equilibrium
spin polarization in MS and the bias. The effective spin-polarized
injection can be realized more easily by optimizing the above
parameters. 相似文献
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HUANG Yanhong Lü Huibin HE Meng ZHAO Kun CHEN Zhenghao CHENG Bolin ZHOU Yueliang JIN Kuijuan DAI Shouyu & YANG Guozhen Beijing National Laboratory for Condensed Matter Physics Institute of Physics Chinese Academy of Sciences Beijing China 《中国科学G辑(英文版)》2005,48(3)
Since the discoveries of high Tc superconductors and colossal magnetoresistance, enormous efforts have been devoted to investigating the perovskite oxide materials. The fabrication of artificial crystalline materials through layer-by-layer epitaxial growth with full control over the composition and structure at the atomic level has become one of the most exciting areas of research in condensed matter physics and materials science. In related research, much attention has been paid to the new de… 相似文献