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A general and simple method for evaluating the electrical transport performance of graphene by the van der Pauw–hall measurement

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Science Bulletin 2018年第22期63卷 1521-1526页

作者： Fangzhu Qing Yang Shu Linsen Qing Yuting Niu He Guo Shuyi Zhang Chunlin Liu Changqing Shen Wanli Zhang Samuel S.Mao Wenjuan Zhu Xuesong Li State Key Laboratory of Electronic Thin Films and Integrated Devices &School of Electronic Science and Engineering University of Electronic Science and Technology of ChinaChengdu 610054China Chengdu Institute of Biology Chinese Academy of SciencesChengdu 610041China National Engineering Research Center of Electromagnetic Radiation Control Materials University of Electronic Science and Technology of ChinaChengdu 610054China Institute of New Energy Shenzhen 518031China Department of Mechanical Engineering University of California at BerkeleyBerkeleyCA 94720USA Department of Electrical and Computer Engineering University of Illinois at Urbana-ChampaignUrbanaIL 61801USA

Expected for many promising applications in the field of electronics and optoelectronics, a reliable method for the characterization of graphene electrical transport properties is desired to predict its device performance or provide feedback for its ***, the commonly used methods of extracting carrier mobility from graphene field effect transistor or hall-bar is time consuming, expensive, and significantly affected by the device fabrication process other than graphene *** we reported a general and simple method to evaluate the electrical transport performance of graphene by the van der Pauw–hall *** annealing graphene in vacuum to remove the adsorbed dopants and then exposing it in ambient surroundings, carrier mobility as a function of density can be measured with the increase of carrier density due to the dopant re-adsorption from the ***, the relationship between the carrier mobility and density can be simply fitted with a power equation to the first level approximation, with which any pair of measured carrier mobility and density can be normalized to an arbitrary carrier density for *** experimentally demonstrated the reliability of the method, which is much simpler than making devices and may promote the standard making for graphene characterization.

关键词： Graphene Van der Pauw hall Chemical vapor deposition (CVD)

Neutral excitation and bulk gap of fractional quantum hall liquids in disk geometry

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Chinese Physics B 2019年第6期28卷 20-26页

作者： Wu-Qing Yang Qi Li Lin-Peng Yang Zi-Xiang Hu Department of Physics Chongqing UniversityChongqing 401331China Department of Physics South University of Science and Technology of ChinaShenzhen 518055China School of Physics and Technology Wuhan UniversityWuhan 430072China

For the numerical simulation of the fractional quantum hall(FQH) effects on a finite disk, the rotational symmetry is the only symmetry that is used in diagonalizing the Hamiltonian. In this work, we propose a method of using the weak translational symmetry for the center of mass of the many-body system. With this approach, the bulk properties, such as the energy gap and the magneto-roton excitation are consistent with those in the closed manifolds like the sphere and torus. As an application, we consider the FQH phase and its phase transition in the fast rotated dipolar fermions. We thus demonstrate the disk geometry having versatility in analyzing the bulk properties beside the usual edge physics.

关键词： fractional quantum hall bulk states edge states magneto-roton dipolar–dipolar interaction

The E×B drift instability in hall thruster using 1D PIC/MCC simulation

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Chinese Physics B 2020年第2期29卷 366-373页

作者： Zahra Asadi Mehdi Sharifian Mojtaba Hashemzadeh Mahmood Borhani Zarandi Hamidreza Ghomi Marzdashti Physics Department Yazd UniversitySafaiyehYazdIran Faculty of Physics Shahrood University of TechnologyShahroodIran Laser and Plasma Research Institute Shahid Beheshti UniversityG.C.EvinTehranIran

The E×B drift instability is studied in hall thruster using one-dimensional particle in cell(PIC)simulation *** using the dispersion relation,it is found that unstable modes occur only in discrete bands in k space at cyclotron *** results indicate that the number of unstable modes increases by increasing the external electric field and decreases by increasing the radial magnetic *** ion mass does not affect the instability ***,the results confirm that there is an instability with short wavelength and high ***,it is shown that the electron and ion distribution functions deviate from the initial state and eventually the instability is saturated by ion trapping in the azimuthal *** for light mass ion,the frequency and phase velocity are very high that could lead to high electron mobility in the axial direction.

关键词： plasma hall thruster particle in cell(PIC)simulation drift instability

High-Quality InSb Grown on Semi-Insulting GaAs Substrates by Metalorganic Chemical Vapor Deposition for hall Sensor Application

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Chinese Physics Letters 2019年第1期36卷 52-55页

作者： Xin Li Yu Zhao Min Xiong Qi-Hua Wu Yan Teng Xiu-Jun Hao Yong Huang Shuang-Yuan Hu Xin Zhu School of Nano Technology and Nano Bionics University of Science and Technology of China Key Laboratory of Nanodevices and Applications Suzhou Institute of Nano-Tech and Nano-BionicsChinese Academy of Sciences School of Physical Science and Technology Shanghai Tech University Suzhou Matrix Opto Co. Ltd

High-quality InSb epilayers are grown on semi-insulting GaAs substrates by metalorganic chemical vapor deposition using an indium pre-deposition technique. The influence of Ⅴ/Ⅲ ratio and indium pre-deposition time on the surface morphology, crystalline quality and electrical properties of the InSb epilayer is systematically investigated using Nomarski microscopy, atomic force microscopy, high-resolution x-ray diffraction, hall measurement and contactless sheet resistance measurement. It is found that a 2-μm-thick InSb epilayer grown at 450℃ with a Ⅴ/Ⅲ ratio of 5 and an indium pre-deposition time of 2.5s exhibits the optimum material quality, with a root-meansquare surface roughness of only 1.2 nm, an XRD rocking curve with full width at half maximum of 358 arcsec and a room-temperature electron mobility of 4.6 × 10~4 cm^2/V·s. These values are comparable with those grown by molecular beam epitaxy. hall sensors are fabricated utilizing a 600-nm-thick InSb epilayer. The output hall voltages of these sensors exceed 10 mV with the input voltage of 1 V at 9.3 mT and the electron mobility of 3.2 × 10~4 cm^2/V·s is determined, which indicates a strong potential for hall applications.

关键词： hall Sensor Application Metal organic chemical vapor deposition Gallium arsenide

Traveling Wave Solutions of the Incompressible Ideal hall Magnetohydrodynamics

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Chinese Physics Letters 2016年第6期33卷 71-73页

作者：吴启鑫夏振伟杨维纮 Department of Modern Physics University of Science and Technology of China

The solutions of incompressible ideal hall magnetohydrodynamics are obtained by using the traveling wave method. It is shown that the velocity and magnetic field parallel to the wave vector can be arbitrary constants. The velocity and magnetic field perpendicular to the wave vector are both helical waves. Moreover, the amplitude of the velocity perpendicular to the wave vector is related to the wave number and the circular frequency. In addition, further studies indicate that, no matter whether the uniform ambient magnetic field exists or not, the forms of the travelling wave solutions do not change.

关键词： hall et on is Traveling Wave Solutions of the Incompressible Ideal hall Magnetohydrodynamics of MHD

Structural stability improvement, Williamson hall analysis and band-gap tailoring through A-site Sr doping in rare earth based double perovskite La2NiMnO6

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Rare Metals 2019年第9期38卷 805-813页

作者： Shah Aarif Ul Islam Mohd Ikram Solid State Research Laboratory Department of PhysicsNational Institute of TechnologySrinagar

The structural,morphological and optical properties of single-phase polycrystalline La2-xSrxNiMnO6(x=0,0.3 and 0.5),synthesized by solid state reaction were *** samples were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM)/energy dispersive analysis of X-rays(EDAX),Raman spectroscopy and diffuse reflectance spectroscopy(DRS)to elucidate the role of A-site Sr-doping in double perovskite La2 *** analysis of XRD patterns revealed that all the samples have monoclinic structure with space group P21/*** gradient in the Williamson hall plots revealed the presence of tensile strain in all the *** morphological studies revealed that average grain size increases along with appreciable decrease in porosity with Sr *** Ni/Mn antisite disorder was introduced in the La2 NiMnO6 by Sr-doping confirmed by an increase in the full width at half maximum(FWHM)and decrease in intensity of the Raman modes at around 540 and 665 cm-1 which correspond to the antisymmetric stretching and symmetric stretching modes,*** results reveal that the band gap in La2 NiMnO6 can be tuned down by Sr-doping to a value of1.37 eV(very close to 1.40 eV,considered as optimum value for better efficiency of a solar cell).Thus,Sr-doped La2 NiMnO6 may be of prime importance for applications in solar cells.

关键词： Double perovskite Monoclinic Williamson hall analysis Band gap tailoring

A method to measure the in situ magnetic field in a hall thruster based on the Faraday rotation effect

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Plasma Science and Technology 2019年第8期21卷 69-73页

作者： Liang HAN Jun GAO Tao CHEN Yuntian CONG Zongliang LI Beijing Institute of Control Engineering Beijing 100094People’s Republic of China

This paper presents a method to measure the in situ magnetic field in a hall thruster by optical non-invasive means, based on the optical Faraday rotation *** method does not affect the discharge of the ***, its time ... 详细信息

关键词： hall thruster in situ magnetic field electron transport photo-detector

Inverse spin hall effect in ITO/YIG exited by spin pumping and spin Seebeck experiments

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Chinese Physics B 2019年第1期28卷 550-554页

作者： Kejian Zhu Weijian Lin Yangtao Su Haibin Shi Yang Meng Hongwu Zhao Beijing National Laboratory for Condensed Matter Physics Institute of Physics Chinese Academy of Sciences School of Physical Sciences University of Chinese Academy of Sciences Songshan Lake Materials Laboratory

Spin currents, which are excited in indium tin oxide(ITO)/yttrium iron garnet(YIG) by the methods of spin pumping and spin Seebeck effect, are investigated through the inverse spin hall effect(ISHE). It is demonstrated that the ISHE voltage can be generated in ITO by spin pumping under both in-plane and out-of-plane magnetization ***, it is observed that the enhancement of spin hall angle and interfacial spin mixing conductance can be achieved by an appropriate annealing process. However, the ISHE voltage is hardly seen in the presence of a longitudinal temperature gradient. The absence of the longitudinal spin Seebeck effect can be ascribed to the almost equal thermal conductivity of ITO and YIG and specific interface structure, or to the large negative temperature dependent spin mixing conductance.

关键词： spin pumping spin Seebeck effect inverse spin hall effect

Roles of initial current carrier in the distribution of field-aligned current in 3-D hall MHD simulations

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Science China(Technological Sciences) 2008年第3期51卷 323-336页

作者： ZHANG XianGuo PU ZuYin MA ZhiWei ZHOU XuZhi Institute of Space Physics and Applied Technology School of Earth and Space SciencePeking UniversityBeijing 100871China Institute of Plasma Physics Chinese Academy of SciencesHefei 230031China Institute of Fusion Theory and Simulation School of ScienceZhejiang UniversityHangzhou 310027China

A three-dimensional (3-D) hall MHD simulation is carried out to study the roles of initial current carrier in the topology of magnetic field, the generation and distribu- tion of field aligned currents (FACs), and the appearance of Alfvén waves. Consid- ering the contribution of ions to the initial current, the topology of the obtained magnetic field turns to be more complex. In some cases, it is found that not only the traditional By quadrupole structure but also a reversal By quadrupole structure appears in the simulation box. This can explain the observational features near the diffusion region, which are inconsistent with the hall MHD theory with the total ini- tial current carried by electrons. Several other interesting features are also emerged. First, motions of electrons and ions are decoupled from each other in the small plasma region (hall effect region) with a scale less than or comparable with the ion inertial length or ion skin depth di=c/ωp. In the non-hall effect region, the global magnetic structure is shifted in +y direction under the influence of ions with initial y directional motion. However, in the hall effect region, magnetic field lines are bent in ?y direction, mainly controlled by the motion of electrons, then By is generated. Second, FACs emerge as a result of the appearance of By. Compared with the prior hall MHD simulation results, the generated FACs shift in +y direction, and hence the dawn-dusk symmetry is broken. Third, the Walén relation in our simulations is consistent with the Walén relation in hall plasma, thus the presence of Alfvén wave is confirmed.

关键词： collisionless magnetic reconnection hall MHD simulation field aligned current (FAC) Alfvén wave hall effects