Spontaneous spin polarization in organic thiophene oligomers

We studied the spin polarization phenomenon of injected charges in organic thiophene oligomer by using extended Su–Schrieffer–Heeger (SSH) model including electron–electron interaction, spin–orbit coupling as well as spin-flip effect. Our simulation shows that a charged carrier is spontaneously spin polarized, which has a lower energy than the non-polarized one. This polarization is related with the amount of injected charges and the polymerization of the molecule.     

The design of spin filter junction in zigzag graphene nanoribbons with asymmetric edge hydrogenation

Using the non-equilibrium Green’s function method combined with the density functional theory, we investigate the electronic transport properties of a heterostructure based on zigzag graphene, This heterostructure consists of H2–NZGNR–H and H–NZGNR–H. Results show that a perfect dual spin filtering effect can be realized with the parallel (P) and antiparallel (AP) magnetiesm configuration, and some magnetic domain walls (DW) at the interface between two component ribbons. The magnetic moments, DOS and PDOS, the transmission pathways and LDOS demonstrate that the edge of C–H2 bonds have important effects for magnetic and spin dependent transport properties compared to the edge of C–H bonds. Our results show that the H2–ZGNR–H/H–NZGNR–H heterostructure holds promise for magneto electronics devices which can keep steady properties when change the widths of the two component ribbons.     

Spin negative differential resistance and high spin filtering behavior realized by devices based on graphene nanoribbons and graphitic carbon nitrides

Using nonequilibrium Green’s functions in combination with the density functional theory, we investigate the spin-dependent electronic transport properties of two nanostructure devices based on graphitic carbon nitrides bridging two zigzag graphene nanoribbons, i.e., center and edge bridged devices, respectively. It is found that the center bridged device behaves spin negative differential resistance properties in different bias ranges for the up and down spin current respectively. The edge bridged device presents obvious negative differential resistance only for the down spin current. Moreover, high spin-filtering efficiency over 80% is obtained in the edge bridged device in the bias range of 0–1.0 V. The magnetic properties of these devices suggest promising applications in spintronics and molecular electronics.     

Enhanced half-metallicity in carbon-chain–linked trigonal graphene

The spin polarization property of a zigzag-edge trigonal graphene (ZTG) linked with different-length carbon chains C_n is investigated theoretically. It has been found that the enhancement of such a property completely depends on that the number of carbon atoms in a chain being odd or even. If it is an even number, the spin polarization is only changed slightly due to the nearly nonmagnetic property of these carbon chains. In contrast, while it is an odd number, the spin polarization is enhanced significantly to a larger energy range, i.e., showing a prominent half-metallicity and perfect spin-filter effects, owing to interactions of the ZTG and carbon chains with the strong ferromagnetism property. Deepgoing analyses show that these results are intimately related to a polyyne-like configuration for carbon chains in nanojunctions and the transition from the bipolar magnetic semiconductor to half-metallicity. Our findings suggest that this simple structure might promise importantly potential applications for developing nano-scale spintronics devices.     

Modulating magnetic ordering of the zigzag-edge trigonal graphene by functionalizations

A pristine zigzag-edge trigonal graphene (ZTG) is a magnetic semiconductor, thus its spin polarization is extremely low. Here, we report the calculated results on enhancing the spin magnetism of a zigzag-edge trigonal graphene (ZTG) by functionalizations, including the heteroatom doping, edge modifications, and introducing topologic defects. It is found that the ZTG features a good tuning ability for functionalizations to improve its spin polarization. When one boron (B) atom is doped to replace one carbon atom in the B sublattice of graphene, a higher spin polarization can be achieved, and the edge modification by Cu, Co, O or B atom can modulate the magnetic ordering significantly due to the spin-polarized charge transfer between the ZTG and terminations, especially for O and Co terminations. And also, the introduced defect (a vacancy and a Stone–Wales defect) can obviously tune local magnetic structures owing to geometrically structural deformations (variations of bond length and bond angle). For these behaviors, in-depth analyses are performed. Our findings suggest that the desirable functionalized ZTG structures might promise importantly potential applications for developing nano-scale spintronics devices.     

砷化镓表面自旋极化光电子发射

本文详细地介绍了在圆偏振光作用下,NEA GaAs表面发射目旋极化光电子的原理,及NEA GaAs表面的制备和装置。介绍了表面Cs-O激活的方法。在用此法激活的NEA GaAs(100)表面上可得到灵敏度为8A/mW,极化度约用35%以上的光电子束。发现清洁的GaAs表面覆盖以50%60%Cs单原子层时,光电子的发射出现第一个极大值,同时发现稳定的发射取决于铯吸附量。     

长波长垂直腔面发射激光器开关及双稳特性

为了研究垂直腔面发射激光器偏振转换特性,基于自旋反转模型,数值研究了正交光注入下1550nm垂直腔面发射激光器频率诱导偏振开关及双稳特性。结果表明,在正交光注入下,连续改变注入光与激光器光场内x线性极化模的频率失谐可诱导产生两类偏振开关和偏振双稳现象,且注入光强与偏振电流的变化都显著影响双稳宽度和激光器的输出特性;合理选择操作条件,可实现对1550nm垂直腔面发射激光器频率诱导偏振开关及双稳的控制。这一结果对垂直腔面发射激光器在全光开关和全光存储等领域的应用具有参考价值。     

感性脉冲电流注入装置的SPICE电路建模

为预测电子设备传导敏感度试验中脉冲电流注入在设备端口产生的干扰强度及波形,建立了感性电流注入装置的SPICE(Simulation Program with Integrated Circuit Emphasis)电路模型.在将装置电路模块化的基础上,应用传输矩阵计算的方法,从实验数据中提取出各模块的电路参数或方程表达式,并转换为SPICE模型,最后再将各模块组合为完整的装置模型.频域和时域的实验显示,模拟结果和测量结果一致性较好.建立的电路模型可用于设计和优化脉冲电流注入试验.     

直接电流注入技术对高场强辐射场的模拟与实践

本文介绍了高场强电磁兼容安全裕度测试工具的一个替代技术:直接电流注入技术。文中通过理论计算和试验测试,分析和验证了直接电流注入技术中注入功率与产生场强的关系及直接电流注入技术模拟高场强辐射场的可行性,为进一步研究和应用直接电流注入技术提供了依据和基础。     

手机传导骚扰抗扰度测试的分析与建议

以电流钳注入法为例,对影响手机传导骚扰抗扰度测试的环境噪声干扰、测试布置、校准方法等因素进行了分析,着重阐述了注入钳校准时的两种阻抗环境,以及为了提高手机传导骚扰抗扰度性能,在研发设计中应采取的措施。     

直接注入模式可见光和红外传感器的注入效率

固体成像传感器包括可见光CCD,IRCCD,CMOS和红外焦平面阵列,其信号由光电二极管经注入栅沟道直接输入到转移级是基本的注入模式.本文总结了近30年来的发展成果,阐述了直接注入效率的理论和基本公式,得出在取样频率低的情况下,增大注入栅的跨导和光电二极管的阻抗是提高注入效率的最有效方法;在光电二极管低阻抗的情况下,采用电流镜像直接注入新设计,其注入栅的跨导可趋于无限大,因而可使注入效率接近100%.分析了电路的新设计方法,研制了64元线列InSb电流镜像直接注入电路.初步测试表明,注入效率与理论分析接近.     

椭圆偏振光注入下VCSELs的偏振开关特性研究

本文基于自旋反转模型,理论研究了椭圆偏振光注入下垂直腔面发射激光器(VCSELs)的偏振开关特性。研究结果表明:在X偏振模占主导的VCSELs中,采用椭圆偏振光注入时,随着注入偏转角度θ的增大,VCSELs发生偏振开关所需的最小注入系数(ηin min)值将呈现减小的趋势;当注入偏转角度θ值固定时,随着注入光与VCSELs中心频率之间的频率失谐量从负值变化到正值,ηin min值总体呈现出先减小后增大的趋势,而ηin min的极小值出现在了注入光的频率靠近VCSELs的Y偏振模频率的附近。因此,改变注入偏转角度及注入频率失谐量均可以实现对VCSELs的偏振开关的有效调控。     

Energy level alignment and interactive spin polarization at organic/ferromagnetic metal interfaces for organic spintronics

Energy level alignment and spin polarization at tetracyanoquinodimethane/Fe and acridine orange base/Fe interfaces are investigated by means of photoelectron spectroscopy and X-ray magnetic circular dichroism (XMCD), respectively, to explore their potential application in organic spintronics. Interface dipoles are observed at both hybrid interfaces, and the work function of Fe is increased by 0.7 eV for the tetracyanoquinodimethane (TCNQ) case, while it is decreased by 1.2 eV for the acridine orange base (AOB) case. According to XMCD results, TCNQ molecule has little influence on the spin polarization of Fe surface. In contrast, AOB molecule reduces the interfacial spin polarization of Fe significantly. Induced spin polarization of the two organic molecules at the interfaces is not observed. The results reveal the necessity of investigating the magnetic property changes of both the OSC and the FM during the process of energy level alignment engineering.     

超光滑基片表面散射的理论研究

从理论和数值模拟两个方面对超光滑表面的散射电磁场进行了分析研究。从极化电流源的散射出发,推导了基片表面背向散射电磁场的微分散射分布。通过与经典散射理论的比较,发现在入射角和散射角都较小时,结论与经典散射理论相一致,但是在入射角或者散射角较大时,两者存在差异,原因是理论中考虑了阴影遮蔽效应,导致了入射光或散射光必须透过两...     

A Passive Optical Fiber Current Sensor Based on YIG

A research on passive optical fiber current sensor based on magneto-optical crystal and a new design of light path of the sensor head are presented. Both methods of dual-channel optical detection of the polarization state of the output light and signal processing are proposed. Signal processing can obtain the linear output of the current measurement of the wire more conveniently. Theoretical analysis on the magnetooptical fiber current sensor is given, followed by experiments. After that, further analysis is made according to the results, which leads to clarifying the exiting problems and their placements.     

可变偏振光注入垂直腔面发射激光器的频率诱导偏振双稳

为了探索垂直腔面发射激光器偏振敏感的双稳演 化规律,进一步拓展其在光信息处理领域方面的应 用,本文采用自旋反转模型,数值研究了可变偏振光注入下1 550 nm垂直腔面发射激光器频率诱导偏振双 稳的特性。研究结果表明:在可变偏振角度光注入下,通过沿不同路径扫描频率失谐,垂直 腔面发射激光 器的两个正交偏振分量可在负失谐和正失谐区域产生频率诱导的偏振双稳。对于一确定的注 入强度,注入 光偏振角度的增加可导致负失谐区域的偏振双稳宽度逐渐扩展,而正失谐区域双稳宽度无明 显的变化;给 定适当的注入光角度,较大的注入强度更易于在负失谐区域展宽偏振双稳宽度。此外,在注 入光偏振角度 和注入强度均一定时,不同偏置电流情况下激光器偏振分量的频率诱导双稳宽度存在较大差 异,系统可以 通过合理地调节注入光偏振角以及偏置电流等参量实现对频率诱导偏振双稳的灵活控制。