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Lattice deformation in epitaxial Fe3O4 films on MgO substrates studied by polarized Raman spectroscopy

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Chinese Physics B 2020年第8期29卷 234-238页

作者： Yang Yang Qiang zhang Wenbo Mi xixiang zhang Beijing National Laboratory for Condensed Matter Physics Institute of PhysicsChinese Academy of SciencesBeijing 100190China PSE Division King Abdullah University of Science and Technology(KAUST)Thuwal 23955-6900Kingdom of Saudi Arabia Tianjin Key Laboratory of Low Dimensional Materials Physics and Preparation Technology School of ScienceTianjin UniversityTianjin 300354China

The lattice structures of epitaxial Fe3O4 films deposited on MgO were studied systematically using polarized Raman spectroscopy as a function of film thickness,where interesting phenomena were ***,the spectral conflict to the Raman selection rules(RSRs)was observed under cross-sectional configuration,which can be attributed to the tetragonal deformation in the growth direction due to the lattice mismatch between Fe3O4 and ***,the blue shift and broadening of Raman peaks evidenced the decrease of the tensile strain in Fe3O4 films with decreasing ***,distinct from the other Raman modes,the lowest T2g mode exhibited asymmetric lineshape,which can be interpreted using the spatial correlation *** increased correlation length introduced in the model can well explain the enhanced peak asymmetry feature with decreasing *** results provide useful information for understanding the lattice structure of epitaxial Fe3O4 film.

关键词： polarized Raman scattering Fe3O4 film tetragonal deformation spatial correlation model

Joint multiple parameters estimation for coherent chirp signals using vector sensor array

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Science in China(Series F) 2008年第1期51卷 93-100页

作者： WEN Zhong LI LiPing CHEN TianQi zhang xixiang School of Electronic Engineering University of Electronic Science and Technology of China Chengdu 610054 China

In this paper, an algorithm is proposed to estimate starting frequency （SF）, chirp rate （CR）, 2-D direction-of-arrivals （DOA） and polarization of coherent chirp signals with vector sensor arrays. The fractional Fourier transformation （FRFT） is used to estimate SF and CR of chirp signals in this method. And a new correlation matrix is reconstructed to suppress the noise. The property of the vector sensor array is employed to solve the problem of insufficient rank from signal coherence. The L-shaped uniform array of expend aperture is used to improve the precision of es- timation, and the method of solving the ambiguity of angle under the condition of coherent signals is presented. The performance of this algorithm is compared with that of spatial smoothing method to verify the efficacy of this approach.

关键词： vector sensor array FRFT coherence

Comparison between Top and Bottom NiO-pinning Spin Valves: Effect of Interfacial Roughness on Specular Reflection

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Journal of Materials Science & Technology 2006年第3期22卷 397-400页

作者： Liang SUN Jun DU Xiaoshan WU Shiming ZHOU xixiang zhang An HU National Laboratory of Solid State Microstructures Department of Physics Nanjing University Nanjing 210093 China State Key Laboratory for Surface Physics Fudan University Shanghai 200433 China Department of Physics Hong Kong University of Science ＆ Technology Kowloon Hong Kong China

Top and bottom NiO-pinning spin valves of Si/Ta/NiO/Co/Cu/Co/Ta and Si/Ta/Co/Cu/Co/NiO/Ta were prepared by magnetron sputtering, and X-ray diffraction and giant magnetoresistance （GMR） ratio were measured in the temperature range from 5 to 300 K. For the bottom spin valve, the interracial roughness at NiO/Co is much smaller than that of Co/NiO in the top one. The Co/Cu and Cu/Co interfaces have the same roughness in the bottom and the top spin valves. NiO, Co, and Cu layers have （111） preferred orientations in the top one and random orientations in the bottom one. The GMR ratio of the bottom spin valve is larger than that of the top one at all temperatures and their difference increases with decreasing temperature.

关键词： Spin valve Specular reflection Interfacial roughness

Achieving room-temperature M_(2)-phase VO_(2) nanowires for superior thermal actuation

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Nano Research 2021年第11期14卷 4146-4153页

作者： Yong-Qiang zhang Kai Chen Hao Shen Yue-Cun Wang Mohamed Nejib Hedhili xixiang zhang Ju Li Zhi-Wei Shan Center for Advancing Materials Performance from the Nanoscale State Key Laboratory for Mechanical Behavior of MaterialsXi’an Jiaotong UniversityXi’an710049China Physical Science and Engineering Division King Abdullah University of Science and Technology(KAUST)Thuwal23955-6900Saudi Arabia Departments of Nuclear Science and Engineering and Materials Science and Engineering Massachusetts Institute of TechnologyCambridgeMA02139USA

Vanadium dioxide (VO_(2)) has emerged as a promising micro-actuator material for its large amplitude and high work density across the transition between the insulating (M_(1) and M_(2)) and metallic (R) phase. Even though M_(2)–R transition offers about 70% higher transformation stress than M_(1)–R structural phase transition, the application of the M_(2) phase in the micro-actuators is hindered by the fact that previously, M_(2) phase can only stay stable under tensile stress. In this work, we propose and verify that by synthesizing the VO_(2) nanowires under optimized oxygen-rich conditions, stoichiometry change can be introduced into the nanowires (NWs) which in turn yield a large number free-standing single-crystalline M_(2)-phase NWs stable at room temperature. In addition, we demonstrate that the output stress of the M_(2)-phase NWs is about 65% higher than that of the M_(1)-phase NWs during their transition to R phase, quite close to the theoretical prediction. Our findings open new avenues towards enhancing the performance of VO_(2)-based actuators by using M_(2)–R transition.

关键词： single crystalline vanadium dioxide(VO_(2))nanowires metal-insulator transition room-temperature M_(2)phase micro-actuator martensitic transformation transformation strain

Develop a 3D neurological disease model of human cortical glutamatergic neurons using micropillar-based scaffolds

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Acta Pharmaceutica Sinica B 2019年第3期9卷 557-564页

作者： Cheng Chen Xin Dong Kai-Heng Fang Fang Yuan Yao Hu Min Xu Yu Huang xixiang zhang Danjun Fang Yan Liu Institute for Stem Cell and Neural Regeneration School of PharmacyNanjing Medical UniversityNanjing211166China Key Laboratory of Targeted Intervention of Cardiovascular Disease Collaborative Innovation Center for Cardiovascular DiseaseTranslational MedicineSchool of PharmacyNanjing Medical UniversityNanjing211166China Department of Biological Engineering Utah State UniversityLoganUT84322USA Physical Sciences and Engineering Division(PSE) King Abdullah University of Science and TechnologyThuwal23955-6900Kingdomof Saudi Arabia Institute for Stem Cell and Regeneration Chinese Academy of SciencesBeijing100101China

Establishing an effective three-dimensional(3D) in vitro culture system to better model human neurological diseases is desirable, since the human brain is a 3D structure. Here, we demonstrated the development of a polydimethylsiloxane(PDMS) pillar-based 3D scaffold that mimicked the 3D microenvironment of the brain. We utilized this scaffold for the growth of human cortical glutamatergic neurons that were differentiated from human pluripotent stem cells. In comparison with the 2D culture, we demonstrated that the developed 3D culture promoted the maturation of human cortical glutamatergic neurons by showing significantly more MAP2 and less Ki67 expression. Based on this 3D culture system,we further developed an in vitro disease-like model of traumatic brain injury(TBI), which showed a robust increase of glutamate-release from the neurons, in response to mechanical impacts, recapitulating the critical pathology of TBI. The increased glutamate-release from our 3D culture model was attenuated by the treatment of neural protective drugs, memantine or nimodipine. The established 3D in vitro human neural culture system and TBI-like model may be used to facilitate mechanistic studies and drug screening for neurotrauma or other neurological diseases.

关键词： 3D culture Cortical glutamatergic neurons Human pluripotent stem cells Cell differentiation Disease modeling Traumatic brain injury Neural protective drugs Drug screening

Large Barocaloric Effect with High Pressure-Driving Efficiency in a Hexagonal MnNi0.77Fe0.23Ge Alloy

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Chinese Physics Letters 2020年第7期37卷 47-50页

作者： Qingqi Zeng Jianlei Shen Enke Liu Xuekui Xi Wenhong Wang Guangheng Wu xixiang zhang Institute of Physics Chinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China Songshan Lake Materials Laboratory Dongguan 523808China Physical Science and Engineering Division(PSE) King Abdullah University of Science and Technology(KAUST)Thuwal 23955-6900Saudi Arabia

The hydrostatic pressure is expected to be an effective knob to tune the magnetostructural phase transitions of hexagonal MM’X alloys(M and M’denote transition metals and X represents main group elements).We perform magnetization measurements under hydrostatic pressure on an MM’X martensitic MnNi0.77Fe0.23Ge *** magnetostructural transition temperature can be efficiently tuned to lower temperatures by applying moderate pressures,with a giant shift rate of-151 K/GPa.A temperature span of 30 K is obtained under the pressure,within which a large magnetic entropy change of-23 J·kg-1K-1 in a field change of 5 T is induced by the mechanical energy gain due to the large volume ***,a decoupling of structural and magnetic transitions is observed at low temperatures when the martensitic transition temperature is lower than the Curie *** results show a multi-parameter tunable caloric effect that benefits the solid-state cooling.

关键词： temperature. transitions martensitic

Dual non-diffractive terahertz beam generators based on all-dielectric metasurface

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Frontiers of Optoelectronics 2021年第2期14卷 201-210页

作者： Chunyu LIU Yanfeng LI Xi FENG xixiang zhang Jiaguang HAN Weili zhang Center for Terahertz Waves College of Precision Instrument and Optoelectronics EngineeringKey Laboratory of Optoelectronics Information and Technology(Ministry of Education of China)Tianjin UniversityTianjin 300072China Physical Science and Engineering Division King Abdullah University of Science and TechnologyThuwal 23955-6900Saudi Arabia School of Electrical and Computer Engineering Oklahoma State UniversityStillwaterOK 74078USA

The applications of terahertz(THz)technology can be greatly extended using non-diffractive beams with unique field distributions and non-diffiactive transmission ***,we design and experimentally demonstrate a set of dual non-diffractive THz beam generators based on an all-dielectric *** kinds of non-diffractive beams with dramatically opposite focusing properties,Bessel beam and abruptly autofocus-ing(AAF)beam,are considered.A Bessel beam with longdistance non-diffractive characteristics and an AAF beam with low energy during transmission and abruptly increased energy near the focus are generated for x-and^-polarized incident waves,*** two kinds of beams are characterized and the results agree well with *** addition,we show numerically that these two kinds of beams can also carry orbital angular momentum by further imposing proper angular phases in the *** believe that these metasurface-based beam generators have great potential use in THz imaging,communications,non-destructive evaluation,and many other fields.

关键词： terahertz(THz)wave all-dielectric metasurface Bessel beam abruptly autofocusing(AAF)beam vortex beam

Terahertz spoof surface-plasmon-polariton subwavelength waveguide

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Photonics Research 2018年第1期9卷 18-23页

作者： YING zhang YUEHONG XU CHUNXIU TIAN QUAN XU XUEQIAN zhang YANFENG LI xixiang zhang JIAGUANG HAN WEILI zhang Center for Terahertz Waves and College of Precision Instrument and Optoelectronics Engineering Tianjin University and the Key Laboratory of Optoelectronics Information and Technology Tianjin Ministry of Education of China Tianjin 300072 China Physical Science and Engineering Division King Abdullah University of Science and Technology Thuwal 23955-6900 Saudi Arabia School of Electrical and Computer Engineering Oklahoma State University Stillwater Oklahoma 74078 USA

Surface plasmon polaritons(SPPs) with the features of subwavelength confinement and strong enhancements have sparked enormous interest. However, in the terahertz regime, due to the perfect conductivities of most metals, it is hard to realize the strong confinement of SPPs, even though the propagation loss could be sufficiently low. One main approach to circumvent this problem is to exploit spoof SPPs, which are expected to exhibit useful subwavelength confinement and relative low propagation loss at terahertz frequencies. Here we report the design,fabrication, and characterization of terahertz spoof SPP waveguides based on corrugated metal surfaces. The various waveguide components, including a straight waveguide, an S-bend waveguide, a Y-splitter, and a directional coupler, were experimentally demonstrated using scanning near-field terahertz microscopy. The proposed waveguide indeed enables propagation, bending, splitting, and coupling of terahertz SPPs and thus paves a new way for the development of flexible and compact plasmonic circuits operating at terahertz frequencies.

关键词：亚波长通讯技术传导速度传播损耗

Quantitative heterogeneity and subgroup classification based on motility of breast cancer cells

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Chinese Physics B 2019年第10期28卷 590-596页

作者： Ling Xiong Yanping Liu Ruchuan Liu Wei Yuan Gao Wang Yi He Jianwei Shuai Yang Jiao xixiang zhang Weijing Han Junle Qu Liyu Liu Chongqing Key Laboratory of Soft Condensed Matter Physics and Smart Materials College of PhysicsChongqing UniversityChongqing 401331China Department of Physics Xiamen UniversityXiamen 361005China Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province Shenzhen UniversityShenzhen 518060China Materials Science and Engineering Arizona State UniversityTempeArizona 85287USA Division of Physical Science and Engineering King Abdullah University of Science and TechnologyThuwal 23955-6900Saudi Arabia Shenzhen Shengyuan Biotechnology Co. LtdShenzhen 518060China

Cancer cell motility and its heterogeneity play an important role in metastasis, which is responsible for death of 90% of cancer patients. Here, in combination with a microfluidic technique, single-cell tracking, and systematic motility analysis,we present a rapid and quantitative approach to judge the motility heterogeneity of breast cancer cells MDA-MB-231 and MCF-7 in a well-defined three-dimensional(3D) microenvironment with controllable conditions. Following this approach,identification of highly mobile active cells in a medium with epithelial growth factor will provide a practical tool for cell invasion and metastasis investigation of multiple cancer cell types, including primary cells. Further, this approach could potentially become a speedy(~ hours) and efficient tool for basic and clinical diagnosis.

关键词： cancer metastasis motility heterogeneity three-dimensional microenvironment invasion potential