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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 synthesis.However, 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 itself.Here we reported a general and simple method to evaluate the electrical transport performance of graphene by the van der Pauw–hall measurement.By 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 surroundings.Further, 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 comparison.We 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)

Experiment of hall thruster plume effects on different ground experimental conditions

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航空动力学报 2019年第7期34卷 1568-1576页

作者： SU Yang CAI Guobiao HE Bijiao SHANG Shengfei LIU Peng LIANG Wei School of Astronautics Beijing University of Aeronautics and AstronauticsBeijing100191China Science and Technology on Reliability and Environmental Engineering Laboratory Beijing Institute of Spacecraft Environment EngineeringChina Aerospace Science and Technology CorporationBeijing100094China Electric Propulsion Department Shanghai Institute of Space PropulsionChina Aerospace Science and Technology CorporationShanghai201112China

Reducing the influence of back-sputtering effect can effectively improve the accuracy of the measurement of the hall thruster plume effect.Quartz crystal microbalance(QCM)was used to measure the deposition and sputtering distribution of HET-40 thruster plume on two different experimental conditions:case1,using liquid nitrogen heat sinks and case 2,without using liquid nitrogen heat sinks.Meanwhile,X-ray photoelectron spectroscopy(XPS)was used to analyze the composition of the QCM surface after two experiments.The results of the two experiments showed that the sputtering rate under the condition of case 1 was slightly higher than case 2.Especially within the range of 90°to 110°relative to the thruster axis,case 1 experiment result showed sputtering effect,while case 2 experiment showed deposition effect.Through analysis of the experimental results,it can be found that using liquid nitrogen heat sink to reduce the temperature of the inner wall surface of vacuum chamber can effectively adsorb the particles sputtered by the plume and reduce the concentration of back-sputtering particles,leading to the above phenomenon.

关键词： vacuum exhaust plume sputtering effect deposition effect hall thruster HET-40

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

Tunneling planer hall effect in Ni_(81)Fe_(19)/Al_2O_3/Ni_x Fe_(1-x) junction

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Science China Mathematics 1999年第10期42卷 1103-1109页

作者：陈慧余冯永嘉熊曹水 University of Science and Technology of China Hefei China

Tunneling planer hall （TPH） effect in Ni81Fe19/Al2O3/NixFe1-x trilayer junction is different from general planer hall effect in single-layer film or two-layer junction. This effect concerns the spin-polarized transport, so that the TPH voltage depends on the angle between magnetic vectors of two ferromagnetic layers. The TPH effect is reported to be influenced by composition and magnetic properties of FM layers and the thickness of the insulating layer.

关键词： ferromagnet/insulator/ferromagnet trilayer junction planer hall effect magnetic tunneling effect.

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 method.By using the dispersion relation,it is found that unstable modes occur only in discrete bands in k space at cyclotron harmonics.The results indicate that the number of unstable modes increases by increasing the external electric field and decreases by increasing the radial magnetic field.The ion mass does not affect the instability wavelength.Furthermore,the results confirm that there is an instability with short wavelength and high frequency.Finally,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 direction.Also 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

A case study of a world-class research project accomplished in China:discovery of the quantum anomalous hall effect

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National Science Review 2016年第4期3卷 404-408页

作者： Junling Huang Dongbo Shi Lan Xue Venkatesh Narayanamurti Belfer Center for Science and International Affairs John F.Kennedy School of GovernmentHarvard University John A.Paulson School of Engineering and Applied Sciences Harvard University School of Public Policy and Management Tsinghua University School of International and Public Affairs Shanghai Jiao Tong University

INTRODUCTION China has achieved very impressive economic growth in the past three decades,but this success is unlikely to continue unless future economic growth is based on technological innovation,derived from strong and sustainable basic research.The Chinese leadership has clearly recognized the need for the development of world-class research universities and the need for a thorough reform

关键词： hall over very A case study of a world-class research project accomplished in China case

First-Principles Calculation on Geometric,Electronic and Optical Properties of Fully Fluorinated Stanene:a Large-Gap Quantum Spin hall Insulator

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Chinese Physics Letters 2016年第6期33卷 104-107页

作者：武红李峰 Department of Physics Nanjing University of Posts and Telecommunications College of Chemistry and Materials Science Jiangsu Key Laboratory of Biofunctional MaterialsNanjing Normal University

The searches for large-gap quantum spin hall insulators are important for both practical and fundamental inter- ests. In this work, we present a theoretical observation of the two-dimensional fully fluorinated stanene （SnF） by means of density functional theory. Remarkably, a significant spin-orbit coupling is observed for the SnF monolayer in the valence band at the F point, with a considerable indirect band gap of 278 meV. The direct gap of the SnF monolayer is at the F point, which is slightly larger by as much as 381 meV. In addition, the elastic modulus of the SnF monolayer is about 20J/m^2, which is comparable with the in-plane stiffness of black phos- phorus monolayer along the x-direction （~28.94 J/m^2）. Finally, the optical properties of stanene, SnF monolayer and stanene/SnF bilayer are calculated, in which the stanene/SnF bilayer is supposed to be an attractive sunlight absorber.

关键词： of in First-Principles Calculation on Geometric,Electronic and Optical Properties of Fully Fluorinated Stanene:a Large-Gap Quantum Spin hall Insulator hall is for on

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 investigated.The 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 NiMnO6.Rietveld analysis of XRD patterns revealed that all the samples have monoclinic structure with space group P21/n.Positive gradient in the Williamson hall plots revealed the presence of tensile strain in all the samples.The morphological studies revealed that average grain size increases along with appreciable decrease in porosity with Sr doping.The 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,respectively.DRS 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

High Signal-to-Noise Ratio hall Devices with a 2D Structure of Dual δ-Doped GaAs/AlGaAs for Low Field Magnetometry

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Chinese Physics Letters 2015年第12期32卷 167-170页

作者：陈笛赵柏秦张新 Institute of Semiconductors Chinese Academy of Sciences Beijing 100083 Shangdong Wave of Huaguang Photonics LTD dinan 250101

Single arid dual δ-doped GaAs/AlGaAs two-dimensional electron gas （2DEG） hall devices for low magnetic field detection at room temperature are prepared. The sensitivity and noise spectrum of the hall devices are measured for evaluating the signal-to-noise ratio performance. It is observed that the dual δ-doped hall devices achieve a minimum detectable magnetic field as low as 303 n T, which is better than the single δ doped hall device prepared under the same growth condition.

关键词： Signal-to-Noise Ratio hall