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

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

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Valley lifetimes of conduction band electrons in monolayer WSe2 13

Valley lifetimes of conduction band electrons in monolayer W...

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Spintronics XIII 2020

作者： Ersfeld, Manfred Volmer, Frank Rathmann, Lars Kotewitz, Luca Heithoff, Maximilian Lohmann, Mark Yang, Bowen Watanabe, Kenji Taniguchi, Takashi Bartels, Ludwig Shi, Jing Stampfer, Christoph Beschoten, Bernd 2nd Institute of Physics JARA-FIT RWTH Aachen University Aachen52074 Germany Department of Physics and Astronomy University of California RiversideCA92521 United States Department of Chemistry and Materials Science and Engineering Program University of California RiversideCA92521 United States Research Center for Functional Materials National Institute for Materials Science 1-1 Namiki Tsukuba Ibaraki305-0044 Japan International Center for Materials Nanoarchitectonics National Institute for Materials Science 1-1 Namiki Tsukuba Ibaraki305-0044 Japan Forschungszentrum Jülich Jülich52425 Germany

ISBN: (数字)9781510637474

ISBN: (纸本)9781510637467

One of the main tasks in the investigation of 2-dimensional transition metal dichalcogenides is the determination of valley lifetimes. In this work, we combine time-resolved Kerr rotation with electrical transport measurements to explore the gate-dependent valley lifetimes of free conduction band electrons of monolayer WSe2. When tuning the Fermi energy into the conduction band we observe a strong decrease of the respective valley lifetimes which is consistent with both spin-orbit and electron-phonon scattering. We explain the formation of a valley polarization by the scattering of optically excited valley polarized bright trions into dark states by intervalley scattering. Furthermore, we show that the conventional time-resolved Kerr rotation measurement scheme has to be modified to account for photo-induced gate screening effects. Disregarding this adaptation can lead to erroneous conclusions drawn from gate-dependent optical measurements and can completely mask the true gatedependent valley dynamics. © 2020 SPIE.

关键词： Transition metals

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Photoluminescence of oxygen vacancy-rich nano-TiO 2 photocatalyst for methylene blue color degradation

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materials science and Engineering: B 2025年 320卷

作者： Mayer Simanjuntak I Made Joni Ferry Faizal Noto Susanto Gultom Dong-Hau Kuo Camellia Panatarani Department of Physics Faculty of Mathematic and Natural Sciences Universitas Padjadjaran Jl. Raya Bandung-Sumedang KM 21 Jatinangor Sumedang 45363 Indonesia Study Program of Biotechnology Faculty of Graduate School Universitas Padjadjaran Jl. Dipati Ukur No.35 Coblong Bandung 40132 Indonesia Functional Nano Powder University Center of Excellence Universitas Padjadjaran Jl. Raya Bandung-Sumedang KM 21 Jatinangor Sumedang 45363 Indonesia Department of Materials Science and Engineering National Taiwan University of Science and Technology No.43 Sec. 4 Keelung Road Taipei 10607 Taiwan

Wastewater containing synthetic dyes poses a critical environmental hazard, necessitating the development of effective treatment techniques. Despite its promise as a photocatalyst, TiO 2 ′s inability to efficiently absorb visible light limits its practical use. To overcome this limitation, oxygen vacancy (OV) engineering was carried out in TiO 2 through solvothermal at temperatures of 150°C, 180°C, and 210°C. Comprehensive analyses confirmed a temperature-induced increase in crystallinity and OV concentration. Furthermore, photoluminescence analysis revealed mid-gap states that improve visible light absorption. Notably, the T150 sample achieved 93.43% degradation of methylene blue within 3 h under sunlight, outperforming commercial TiO 2 . The superior performance was attributed to a reduced bandgap energy, enhanced charge carrier separation, and increased generation of reactive oxygen species, all facilitated by an optimal concentration of OV. This study clarifies the interaction between photoluminescence and photocatalytic activity, highlighting OV engineering as a highly effective strategy for developing advanced TiO 2 -based materials for wastewater treatment.

关键词： Photocatalytic activity

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Selectivity of CO_(2)reduction reaction to CO on the graphitic edge active sites of Fe-single-atom and dual-atom catalysts:A combined DFT and microkinetic modeling

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Carbon Resources Conversion 2024年第1期7卷 21-31页

作者： Ahmad Nuruddin Adhitya Gandaryus Saputro Arifin Luthfi Maulana Febdian Rusydi Fiki Taufik Akbar Hadi Teguh Yudistira Hermawan Kresno Dipojono Advanced Functional Materials Research Group Faculty of Industrial TechnologyInstitut Teknologi BandungJl.Ganesha No.10Bandung 40132Indonesia Research Center for Nanosciences and Nanotechnology Institut Teknologi BandungJl.Ganesha No.10Bandung 40132Indonesia Research Center for Quantum Engineering Design Department of PhysicsFaculty of Science and TechnologyUniversitas AirlanggaSurabaya 60115Indonesia Theoretical High Energy Physics Research Division Faculty of Mathematics and Natural SciencesInstitut Teknologi BandungJl.Ganesha No.10Bandung 40132Indonesia Mechanical Engineering Study Program Institut Teknologi Sumatera(ITERA)South LampungLampungIndonesia Department of Materials Science and Engineering University of CaliforniaBerkeleyBerkeleyCA 94720United States

We study the carbon dioxide reduction reaction(CO_(2)RR)activity and selectivity of Fe single-atom catalyst(Fe-SAC)and Fe dual-atom catalyst(Fe-DAC)active sites at the interior of graphene and the edges of graphitic nanopore by using a combination of DFT calculations and microkinetic *** trend of limiting potentials for CO_(2)RR to produce CO can be described by using either the adsorption energy of COOH,CO,or their ***_(2)RR process with reasonable reaction rates can be achieved only on the active site configurations with weak tendencies toward CO *** efficiency of CO_(2)RR on a catalyst depends on its ability to suppress the parasitic hydrogen evolution reaction(HER),which is directly related to the behavior of H adsorption on the catalyst’s active *** find that the edges of the graphitic nanopore can act as potential adsorption sites for an H atom,and in some cases,the edge site can bind the H atom much stronger than the main Fe *** linear scaling between CO and H adsorptions is broken if this condition is *** condition also allows some edge active site configurations to have their CO_(2)RR limiting potential lower than the HER process favoring CO production over H2 production.

关键词： CO_(2)RR FexNy active site Fe-SAC Fe-DAC Graphitic edges DFT Microkinetic

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Surface buckling of black phosphorus: Determination, origin, and influence on electronic structure

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Physical Review materials 2017年第7期1卷 074003-074003页

作者： Zhongwei Dai Wencan Jin Jie-Xiang Yu Maxwell Grady Jerzy T. Sadowski Young Duck Kim James Hone Jerry I. Dadap Jiadong Zang Richard M. Osgood, Jr. Karsten Pohl Department of Physics and Materials Science Program University of New Hampshire Durham New Hampshire 03824 USA Columbia University New York New York 10027 USA Center for Functional Nanomaterials Brookhaven National Laboratory Upton New York 11973 USA

The surface structure of black phosphorus materials is determined using surface-sensitive dynamical microspot low energy electron diffraction (μLEED) analysis using a high spatial resolution low energy electron microscopy (LEEM) system. Samples of (i) crystalline cleaved black phosphorus (BP) at 300 K and (ii) exfoliated few-layer phosphorene (FLP) of about 10 nm thickness which were annealed at 573 K in vacuum were studied. In both samples, a significant surface buckling of 0.22 Å and 0.30 Å, respectively, is measured, which is one order of magnitude larger than previously reported. As direct evidence for large buckling, we observe a set of (for the flat surface forbidden) diffraction spots. Using first-principles calculations, we find that the presence of surface vacancies is responsible for the surface buckling in both BP and FLP, and is related to the intrinsic hole doping of phosphoresce materials previously reported.

关键词： Band gap Crystal defects Crystal structure Crystal symmetry Defects Density of states Edge states Electronic structure Structural properties Surface & interfacial phenomena Surface instabilities Surface reconstruction

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In-situ TEM-STM observations of SWCNT ropes/tubular transformations

In-situ TEM-STM observations of SWCNT ropes/tubular transfor...

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2009 MRS Fall Meeting

作者： Solá, F. Lebrón-Colón, M. Ferreira, P.J. Fonseca, L.F. Meador, M.A. Marín, C. Glenn Research Center Structures and Materials Division 21000 Brookpark Road Cleveland OH 44135 United States Advanced Metallics Branch United States Polymers Branch United States Materials Science and Engineering Program University of Texas at Austin Austin TX 78712 United States Department of Physics Institute for Functional Nanomaterials University of Puerto Rico Rio Piedras PO Box 23343 San Juan PR 00931 United States

ISBN: (纸本)9781605111773

Single-walled carbon nanotubes (SWCNTs) prepared by the HiPco process were purified using a modified gas phase purification technique. A TEM-STM holder was used to study the morphological changes of SWCNT ropes as a function of applied voltage. Kink formation, buckling behavior, tubular transformation and eventual breakdown of the system were observed. The tubular formation was attributed to a transformation from SWCNT ropes to multi-walled carbon nanotube (MWCNT) structures. It is likely mediated by the patching and tearing mechanism which is promoted primarily by the mobile vacancies generated due to current-induced heating and, to some extent, by electron irradiation. © 2010 materials Research Society.

关键词： Electron irradiation

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Pressure induced band structure evolution of halide perovskites: A first-principles atomic and electronic structure study

arXiv

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arXiv 2018年

作者： Huang, Yang Wang, Lingrui Ma, Zhuang Wang, Fei International Laboratory for Quantum Functional Materials of Henan School of Physics and Engineering Zhengzhou University Zhengzhou450001 China Materials Science and Engineering Program University of California San Diego San DiegoCA92093 United States Key Laboratory of Materials Physics of Ministry of Education School of Physics and Engineering Zhengzhou University Zhengzhou450001 China

Density functional theory (DFT) based calculations have been conducted to draw a broad picture of pressure induced band structure evolution in various phases of organic and inorganic halide perovskite materials. Under a wide range of pressure applied, distinct band structure behaviors including magnitude change of band gap, direct-indirect/indirect-direct band gap transitions and CBM/VBM shifts, have been observed between organic and inorganic perovskites among different phases. Through atomic and electronic structure calculations, band gap narrowing/widening has been rationalized through crystal orbitals coupling transformations;direct-indirect mutual transitions were explained based on structural symmetry evolution;different VBM/CBM shifts behaviors between organic and inorganic perovskites were analyzed focusing on orientation and polarity of molecules/atoms outside the octahedrals. These results provide a comprehensive guidance for further experimental investigations on pressure engineering of perovskite materials. Copyright © 2018, The Authors. All rights reserved.

关键词： Perovskite

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Uncompensated moments in antiferromagnets: Origin, properties and role in exchange bias

Uncompensated moments in antiferromagnets: Origin, propertie...

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2010 12th International Conference on Electromagnetics in Advanced Applications, ICEAA'10

作者： Roshchin, Igor V. Badgley, Karie E. Zhernenkov, Mikhail Fitzsimmons, Michael R. Varela, Maria Pennycook, Stephen J. Li, Zhi-Pan Ponce, H. Romero, A.H. Miller, Casey W. Schuller, Ivan K. Physics Department Texas AandM University College Station TX 77843-4242 United States Materials Science and Engineering Program Texas A and M University Collegest Station TX 77843-3003 United States Los Alamos Neutron Science Center Los Alamos National Laboratory Los Alamos NM 87545 United States Oak Ridge National Laboratory Oak Ridge TN United States Brion Technologies Santa Clara CA 95051 United States Physics Department University of California - San Diego San Diego CA 92093-0319 United States Materials Department CINVESTAV Querétaro Mexico Department of Physics Center for Integrated Functional Materials University of South Florida Tampa FL 33620 United States

ISBN: (纸本)9781424473687

Presented is a study of uncompensated magnetization in antiferromagnets performed by SQUID and VSM magnetometry, and polarized neutron reflectometry. This uncompensated magnetization is observed and studied as a function of temperature and cooling conditions. Uncompensated magnetization is found close to the top surface of the antiferromagnet (interface with the ferromagnet) and also in the "bulk" of the antiferromagnetic film. It has been established that this uncompensated magnetization plays crucial role in exchange bias. To understand the origin of uncompensated magnetization, ab initio calculations are performed. ©2010 IEEE.

关键词： Magnetization

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Electronic and magnetic properties of the topological semimetal candidate NdSbTe

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Physical Review B 2020年第23期101卷 235161-235161页

作者： Krishna Pandey Rabindra Basnet Aaron Wegner Gokul Acharya Md Rafique Un Nabi Jiangwei Liu Jian Wang Y. K. Takahashi Bo Da Jin Hu Materials Science and Engineering Program Institute for Nanoscience and Engineering University of Arkansas Fayetteville Arkansas 72701 USA Department of Physics University of Arkansas Fayetteville Arkansas 72701 USA Research Center for Functional Materials National Institute for Materials Science Tsukuba Ibaraki 305-0047 Japan Institute for Materials Research and Center for Spintronics Research Network Tohoku University Sendai 980–8577 Japan Research Center for Magnetic and Spintronic Materials National Institute for Materials Science Sengen 1-2-1 Tsukuba Ibaraki 305-0047 Japan Research and Services Division of Materials Data and Integrated System National Institute for Materials Science Tsukuba Ibaraki 305-0044 Japan

ZrSiS-type materials represent a large material family with unusual coexistence of topological nonsymmorphic Dirac fermions and nodal-line fermions. As a special group of ZrSiS family, LnSbTe (Ln=lanthaniderare−earth) compounds provide a unique opportunity to explore new quantum phases due to the intrinsic magnetism induced by Ln. Here we report the single-crystal growth and characterization of NdSbTe, a previously unexplored LnSbTe compound. NdSbTe has an antiferromagnetic ground state with field-driven metamagnetic transitions similar to other known LnSbTe, but exhibits distinct enhanced electronic correlations characterized by large a Sommerfeld coefficient of 115mJ/molK2, which is the highest among the known LnSbTe compounds. Furthermore, our transport studies have revealed the coupling with magnetism and signatures of Kondo localization. All these findings establish NdSbTe as a platform for observing phenomena arising from the interplay between magnetism, topology, and electron correlations.

关键词： Magnetic order Magnetotransport Topological phases of matter Magnetic systems Single crystal materials Strongly correlated systems Topological materials Magnetic techniques Specific heat measurements Transport techniques

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Effect of surface steps on chemical ordering in the subsurface of Cu(Au) solid solutions

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Physical Review B 2021年第3期103卷 035401-035401页

作者： Kuo Liu Siming Zhang Dongxiang Wu Langli Luo Xianhu Sun Xiaobo Chen Dmitri Zakharov Shaobo Cheng Yimei Zhu Judith C. Yang Guofeng Wang Guangwen Zhou Department of Mechanical Engineering and Materials Science and Engineering Program State University of New York Binghamton New York 13902 USA Department of Mechanical Engineering and Materials Science University of Pittsburgh Pittsburgh Pennsylvania 15261 USA Center for Functional Nanomaterials Brookhaven National Laboratory Upton New York 11973 USA Department of Condensed Matter Physics and Materials Science Brookhaven National Laboratory Upton New York 11973 USA Department of Chemical and Petroleum Engineering University of Pittsburgh Pittsburgh Pennsylvania 15261 USA

Atomic steps are typically assumed to only influence surface phenomena of solids. In contrast, here we show, using in situ atomic-resolution electron microscopy observations and atomistic modeling, the pronounced effect from surface steps in inducing compositional and structural evolution in the subsurface of a Cu(Au) solid solution. We find that Au surface segregation results in a stacked sequence of Cu-Au ordered phases in the subsurface. The presence of a monatomic step at the surface induces the formation of an antiphase boundary that extends from the surface step to deeper layers by maintaining the same composition profile associated with each terrace. The bunching of surface steps induces chemical disordering of the Cu-Au ordered phases in the subsurface region of the bunched steps. These results demonstrate the instant propagation of surface dynamics of atomic steps into the subsurface region and can find broader applicability in utilizing surface defects to tune the composition and structure in the subsurface of alloys.

关键词： Structural properties Surface & interfacial phenomena Alloys Density functional theory Electron microscopy

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