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Chinese Physics Letters 2002年第10期19卷 1480-1482页

作者：王岩国沈峰等 BeijingLaboratoryofelectronMicroscopy InstituteofPhysicsandCenterforCondensedMatterPhysicsChineseAcademyofSciencesPoBox2724Beijing100080 BeijingLaboratoryofelectronMicroscopy InstituteofPhysicsandC

The local potential distribution in a specular spin valve structure with nano-oxide layers has been mapped by using off-axis electron holography in a field emission gun transmission electron microscope. A potential jump of 3-4 V across the metal/oxide interface was detected for the first time. The presence of the potential barrier confirms the formation of the metal/insulator/metal structure, which contributes to the increasing mean free path of spin-polarized electrons via the specular reflection of spin-polarized electrons at the metal/oxide interface. It leads to nearly double enhancement of the magnetoresistance ratio from 8% to 15%.

关键词： Determination Potential Barrier Metal/Oxide Interface Specular Spin Valve Structure Nano-oxide Layers electron holography

Controllable synthesis of elongated hexagonal bipyramid shaped La(OH)3 nanorods and the distribution of electric property by off-axis electron holography

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Nano Research 2016年第9期9卷 2561-2571页

作者： Zhiwei Wen Chongyun Liang Han Bi Yuesheng Li Renchao Che Laboratory of Advanced Materials Department of Materials ScienceiChEMCollaborative Innovation Center of Chemistry for Energy MaterialsDepartment of ChemistryFudan UniversityShanghai 200438China

Rare earth oxides/hydroxides are important emerging materials owing to their unique properties. Shape-controlled synthesis of elongated hexagonal bipyramid shaped La(OH)3nanorods with different aspect ratios and trigram-shaped LaCO3OH nanosheets was systematically carried out by controlling the reaction conditions. Hydrazine and polyvinylpyrrolidone (PVP) surfactants used in synthesis are assumed to play a key “dual-template” role in determining the aspect ratio and shape of the resulting nanostructures. Elongated hexagonal bipyramid shaped La(OH)3nanorods were found to grow along the preferred orientation [0001]. Six equivalent crystallographic facets, (Formula presented.), and (Formula presented.) lattice planes, were found to be exposed on the side surfaces on each nanorod as confirmed by combined transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and selected area electron diffraction (SAED) analyses. A double-polarization phenomenon was found to occur at the nanorod surfaces by employing off-axis electron holography, implying that the material could be used as an effective dielectric microwave absorber. La(OH)3nanorods with larger aspect ratios exhibit better absorption properties with respect to the maximum reflection loss and effective absorbing bandwidth. Thus, a novel method towards the reasonable design of bipyramid shaped La(OH)3nanorods exhibiting tunable microwave absorption properties is proposed based on our synthesis strategy. [Figure not available: see fulltext.] © 2016, Tsinghua University Press and Springer-Verlag Berlin Heidelberg.

关键词： controllable synthesis elongated hexagonal bipyramid lanthanum hydroxide electric property electron holography microwave absorption

Determination of Mean Inner Potential by electron holography Along with electron Dynamic Simulation

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Chinese Physics Letters 2003年第12期20卷 2214-2217页

作者：王岩国刘红荣杨奇斌张泽 BeijingLaboratoryofelectronMicroscopy InstituteofPhysicsandCenterforCondensedMatterPhysicsChineseAcademyofSciencesPOBox603Beijing100080 InstituteofModernPhysics XiangtanUniversityXiangtan411105

Off-axis electron holography in a field-emission-gun transmission electron microscope and electron dynamic simulation is used to determine the mean inner potential of copper. The phase shift of object wave versus specimen thickness is calculated up to 30 nm using electron dynamic formula, and the sample thickness is decided by match of the experimental and calculated phase shift. Based on the measured phase shift, the calculated mean inner potential of Cu is 21.2 V, which agrees with the reported values within the experimental error.

关键词： electrons Copper Phase shift electron holography Dynamic simulation

Determination of Inelastic Mean Free Path by electron holography Along with electron Dynamic Calculation

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Chinese Physics Letters 2003年第6期20卷 888-890页

作者： WANGYan-Guo LIUHong-Rong YANGQi-Bin ZHANGZe BeijingLaboratoryofelectronMicroscopy InstituteofPhysicsandCenterforCondensedMatterPhysicsChineseAcademyofSciencesBeijing100080 InstituteofPhysics XiangtanUniversityXiangtan411105

Off-axis electron holography in a field emission gun transmission-electron microscope and electron dynamic calculation are used to determine the absorption coefficient and inelastic mean free path (IMFP) of copper. Dependence of the phase shift of the exit electron wave on the specimen thickness is established by electron dynamic simulation. The established relationship makes it possible to determine the specimen thickness with the calculated phase shift by match of the phase shift measured in the reconstructed phase image. Based on the measured amplitudes in reconstructed exit electron wave and reference wave in the vacuum, the examined IMFP of electron with energy of 200 kV in Cu is obtained to be 96 nm.

关键词： electrons Phase shift electron holography absorption coefficients reference wave PHASE IMAGING mean free path Electric waves

In-situ potential mapping of space charge layer in Ga N nanowires under electrical fi eld by off-axis electron holography

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Progress in Natural Science:Materials International 2016年第2期26卷 163-168页

作者： Xiao Chen Yanguo Wang Jie Guo Jikang Jian Lin Gu Zhihua Zhang Liaoning Key Materials Laboratory for Railway Dalian Jiaotong University Beijing National Laboratory of Condensed Matter Physics Institute of Physics Chinese Academy of Sciences School of Physics Science and Technology Xinjiang University Collaborative Innovation Center of Quantum Matter

In situ potential mapping of space charge（SC） layer in a single Ga N nanowire（NW） contacted to the Au metal electrode has been conducted using off-axis electron holography in order to study the space distribution of SC layer under electric biases. Based on the phase image reconstructed from the complex hologram the electrostatic potential at the SC layer was clearly revealed; the SC width was estimated to be about 76 nm under zero bias condition. In order to study dynamic interrelation between the SC layer and bias conditions, the variation of the electrostatic potential due to change of the SC widths respond to the different bias conditions have also been examined. The measured SC layers are found to vary between68 nm and 91 nm, which correspond to the saturated SC layers at the Ga N-Au contact under the forward and reverse bias conditions, respectively. By plotting the square widths of the SC layer against the applied voltages, donor density of Ga N NWs was derived to be about 4.3*10;cm;. Our experiments demonstrate that in-situ electron holography under electric fi eld can be a useful method to investigate SC layers and donor density in single NW and other heterostructures.

关键词： Space charge layer electron holography In-situ TEM Semiconductor nanowire Semiconductor-metal contact

Size-Dependent Oxidation-Induced Phase Engineering for MOFs Derivatives Via Spatial Confinement Strategy Toward Enhanced Microwave Absorption

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Nano-Micro Letters 2022年第6期14卷 294-307页

作者： Hanxiao Xu Guozheng Zhang Yi Wang Mingqiang Ning Bo Ouyang Yang Zhao Ying Huang Panbo Liu School of Chemistry and Chemical Engineering μNorthwestern Polytechnical UniversityXi’an 710129People’s Republic of China Key Laboratory of Magnetic Materials and Devices Ningbo Institute of Materials Technology&EngineeringChinese Academy of SciencesNingbo 315201People’s Republic of China MIIT Key Laboratory of Semiconductor Microstructure and Quantum Sensing Nanjing University of Science and TechnologyNanjing 210094People’s Republic of China Department of Mechanical and Materials Engineering University of Western OntarioLondonON N6A 5B9Canada

Precisely reducing the size of metal-organic frameworks(MOFs)derivatives is an effective strategy to manipulate their phase engineering owing to size-dependent oxidation;however,the underlying relationship between the size of derivatives and phase engineering has not been clarified so ***,a spatial confined growth strategy is proposed to encapsulate small-size MOFs derivatives into hollow carbon *** realizes that the hollow cavity shows a significant spatial confinement effect on the size of confined MOFs crystals and subsequently affects the dielectric polarization due to the phase hybridization with tunable coherent interfaces and heterojunctions owing to size-dependent oxidation motion,yielding to satisfied microwave attenuation with an optimal reflection loss of-50.6 d B and effective bandwidth of 6.6 ***,the effect of phase hybridization on dielectric polarization is deeply visualized,and the simulated calculation and electron holograms demonstrate that dielectric polarization is shown to be dominant dissipation mechanism in determining microwave *** spatial confined growth strategy provides a versatile methodology for manipulating the size of MOFs derivatives and the understanding of size-dependent oxidation-induced phase hybridization offers a precise inspiration in optimizing dielectric polarization and microwave attenuation in theory.

关键词： Size-dependent oxidation Phase engineering Coherent interface Dielectric polarization electron holography

Metastable noble gas atoms in strong-field ionization experiments

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High Power Laser Science and Engineering 2016年第3期4卷 74-100页

作者： J.E.Calvert A.J.Palmer I.V.Litvinyuk R.T.Sang Australian Attosecond Science Facility Center for Quantum Dynamics School of Natural Sciences Griffith University

The interactions of strong-field few-cycle laser pulses with metastable states of noble gas atoms are examined. Metastable noble gas atoms offer a combination of low ionization potential and a relatively simple atomic structure, making them excellent targets for examining ionization dynamics in varying experimental conditions. A review of the current work performed on metastable noble gas atoms is presented.

关键词： COLTRIMS electron holography high power lasers ionization regime metastable atoms spin polarized targets

Hierarchical coupling effect in hollow Ni/NiFe2O4-CNTs microsphere via spray-drying for enhanced oxygen evolution electrocatalysis

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Nano Research 2020年第2期13卷 437-446页

作者： Xuefeng Yu Guanyu Chen Yizhe Wang Jiwei Liu Ke Pei Yunhao Zhao Wenbin You Lei Wang Jie Zhang Linshen Xing Jingjun Ding Guangzhou Ding Min Wang Renchao Che Laboratory of Advanced Materials Department of Materials Science and Collaborative Innovation Center of Chemistry for Energy Materials(iChem)Fudan UniversityShanghai 200438China Materials Genome Institute International Centre of Quantum and Molecular Structuresand Physics DepartmentShanghai UniversityShanghai 200444China College of Materials and Environmental Engineering Hangzhou Dianzi UniversityHangzhou 310012China

Design and fabrication of cost-effective transition metal and their oxides-based nanocomposites are of paramount significance for metal-air batteries and ***,the traditional optimized designs for nanostructure are complicated,low-efficient and underperform for wide-scale ***,a novel hierarchical framework of hollow Ni/NiFe2O4-CNTs compositemicrosphere forcibly-assembled by zero-dimensional(OD)Ni/NiFo204 nanoparticle(electron *** density functional theory(DFT)calculation indicates the epitaxial Ni further enriches the intrinsic electrons contents of NiFe204 and thus accelerates absorption/desorption kinetics of OER *** work hereby paves a facile route to construct the hollow composite microsphere with excellent OER electrocatalytic activity based on non-noble metal oxide/CNTs.

关键词： spray-drying novel structure oxygen evolution reaction(OER) electron holography composite microsphere

Three-dimensional magnetization reconstruction from electron optical phase images with physical constraints

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Science China(Physics,Mechanics & Astronomy) 2024年第11期67卷 122-132页

作者： Boyao Lyu Shihua Zhao Yibo Zhang Weiwei Wang Fengshan Zheng Rafal E.Dunin-Borkowski Jiadong Zang Haifeng Du Anhui Province Key Laboratory of Low-Energy Quantum Materials and Devices High Magnetic Field LaboratoryHefei Institutes of Physical ScienceChinese Academy of SciencesHefei 230031China Science Island Branch Graduate School of University of Science and Technology of ChinaHefei 230026China Department of Physics and Astronomy University of New HampshireDurham 03824USA Department of Physics The City College of New YorkNew York 10031USA Physics Program Graduate Center of the City University of New YorkNew York 10016USA Department of Chemistry University of New HampshireDurham 03824USA Institutes of Physical Science and Information Technology Anhui UniversityHefei 230601China Spin-X Institute Center for Electron MicroscopySchool of Physics and OptoelectronicsState Key Laboratory of Luminescent Materials and DevicesGuangdong-Hong Kong-Macao Joint Laboratory of Optoelectronic and Magnetic Functional MaterialsSouth China University of TechnologyGuangzhou 511442China Ernst Ruska-Centre for Microscopy and Spectroscopy with electrons Forschungszentrum JülichJülich 52425Germany

The ability to characterize three-dimensional(3D)magnetization distributions in nanoscale magnetic materials and devices is essential to fully understand their static and dynamic magnetic *** contrast techniques in the transmission electron microscope(TEM),such as electron holography and electron ptychography,can be used to record two-dimensional(2D)projections of the in-plane magnetic induction of 3D nanoscale *** the 3D magnetic induction can in principle be reconstructed from one or more tilt series of such 2D projections,conventional tomographic reconstruction algorithms do not recover the 3D magnetization within a sample ***,we use simulations to describe the basis of an improved model-based algorithm for the tomographic reconstruction of a 3D magnetization distribution from one or more tilt series of electron optical phase images recorded in the *** algorithm allows a wide range of physical constraints,including a priori information about the sample geometry and magnetic parameters,to be *** also makes use of minimization of the micromagnetic energy in the loss *** demonstrate the reconstruction of the 3D magnetization of a localized magnetic soliton—a hopfion ring—and discuss the influence of noise,choice of magnetic constants,maximum tilt angle and number of tilt axes on the *** algorithm can in principle be adapted for other magnetic contrast imaging techniques in the TEM,as well as for other magnetic characterization techniques,such as those based on X-rays or neutrons.

关键词： three-dimensional magnetization vector field tomography differentiable programming electron holography micromagnetism

Anisotropic edge enhancement in optical scanning holography with spiral phase filtering

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Chinese Optics Letters 2016年第1期14卷 21-25页

作者： Kelly K. Dobson 贾伟 Ting-Chung Poon Bradley Department of Electrical and Computer Engineering Virginia TechBlacksburgVA 24061USA Lab of Information Optics and Optoelectronic Technology Shanghai Institute of Optics and Fine MechanicsChinese Academy of SciencesShanghai 201800China

Anisotropic edge enhancement is simulated using a spiral phase plate （SPP） in optical scanning holography （OSH）. We propose to use a delta function and an SPP as the pupil functions to realize anisotropic edge enhancement. The interference of these two pupils is used to two-dimensionally scan an object to record its edge-only information. This is done in three ways： first, by shifting the SPP, second, by using two offset SPPs of same charge, and finally, by using two oppositely charged SPPs. Our computer simulations show the capability of selectively enhancing the edges of a given obiect.

关键词： Delta functions electron holography holography Scanning Surface plasmon resonance