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Optimizing the size and electronic effects of core-shell heterostructures via well-constructed Ru clusters encapsulated in N-doped carbon layers

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Chinese Chemical Letters 2024年

作者： Min Jie Wang Jiao Yang Lishan Peng Yongjie Bai Zehui Liu Xiaoliang Yang Huijuan Lu Bingjie Zhou Ningtao Jiang Guoxu He Han-Ming Zhang Liwei Mi Yonghui Deng School of Chemistry and Environmental Engineering Pingdingshan University Pingdingshan 467000 China Key Laboratory of Rare Earths Chinese Academy of Sciences； Ganjiang Innovation Academy Chinese Academy of Sciences Ganzhou 341119 China China Automotive Technology and Research Center Co. Ltd. Tianjin 300300 China Department of Electrical and Computer Engineering North Dakota State University Fargo 58102 United States School of Materials Science and Engineering Hebei University of Science and Technology Shijiazhuang 050018 China Yaoshan laboratory Pingdingshan University Pingdingshan 467000 China Department of Chemistry State Key Laboratory of Molecular Engineering of Polymers Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials Collaborative Innovation Center of Chemistry for Energy Material (iChEM) Fudan University Shanghai 200433 China State Key Lab of Transducer Technology Shanghai Institute of Microsystem and Information Technology Chinese Academy of Sciences Shanghai 200050 China

The design and development of high-performance electrocatalysts for the hydrogen evolution reaction (HER) are essential for advancing the hydrogen economy. The electronic structure and core size of an electrocatalyst are pivotal for determining the intrinsic activity of the catalytic sites. Interfacial engineering, particularly the formation of well-controlled core-shell heterostructures, has emerged as a promising strategy, although significant challenges remain. Here, we present a series of Ru@NC heterostructures with size-controlled Ru cores encapsulated in N-doped graphene layers. Among these, Ru@NC-3h, with the best holistic effects, has superior durability and mass activity 7.03 times that of Pt/C. This high performance is attributed to the open porous structure, which enhances active site exposure and mass transfer, and the optimized adsorption and desorption of reaction intermediates by the strengthened hetero-interfacial interaction between the smaller Ru cores and thin N-doped shells. Attenuated total reflectance surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) reveals reinforced interfacial water interaction and reduced hydrogen adsorption. Density functional theory (DFT) calculations indicate that the size effect promotes interfacial H 2 O adsorption, whereas the electronic effect governs *H adsorption to collectively accelerate the HER kinetics. This novel strategy, introduced to regulate heterostructures through size and electronic effects, offers significant potential for various energy material applications.

关键词： Hydrogen evolution reaction Interfacial engineering Core-shell heterostructures Holistic effects Density functional theory

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Route to High Hole Mobility in GaN via Reversal of Crystal-Field Splitting

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Physical Review Letters 2019年第9期123卷 096602-096602页

作者： Samuel Poncé Debdeep Jena Feliciano Giustino Department of Materials University of Oxford Parks Road Oxford OX1 3PH United Kingdom School of Electrical and Computer Engineering Cornell University Ithaca New York 14853 USA Department of Material Science and Engineering Cornell University Ithaca New York 14853 USA

A fundamental obstacle toward the realization of GaN p-channel transistors is its low hole mobility. Here we investigate the intrinsic phonon-limited mobility of electrons and holes in wurtzite GaN using the ab initio Boltzmann transport formalism, including all electron-phonon scattering processes and many-body quasiparticle band structures. We predict that the hole mobility can be increased by reversing the sign of the crystal-field splitting in such a way as to lift the split-off hole states above the light and heavy holes. We find that a 2% biaxial tensile strain can increase the hole mobility by 230%, up to a theoretical Hall mobility of 120 cm2/V s at room temperature and 620 cm2/V s at 100 K.

关键词： Electron-phonon coupling Transport phenomena Nitrides Boltzmann theory First-principles calculations

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Hole mobility of strained GaN from first principles

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Physical Review B 2019年第8期100卷 085204-085204页

Nitride semiconductors are ubiquitous in optoelectronic devices such as LEDs and Blu-Ray optical disks. A major limitation for further adoption of GaN in power electronics is its low hole mobility. In order to address this challenge, here we investigate the phonon-limited mobility of wurtzite GaN using the ab initio Boltzmann transport formalism, including all electron-phonon scattering processes, spin-orbit coupling, and many-body quasiparticle band structures. We demonstrate that the mobility is dominated by acoustic deformation-potential scattering, and we predict that the hole mobility can significantly be increased by lifting the split-off hole states above the light and heavy holes. This can be achieved by reversing the sign of the crystal-field splitting via strain or via coherent excitation of the A1 optical phonon through ultrafast infrared optical pulses.

关键词： Phonons III-V semiconductors Wurtzite Boltzmann theory Density functional calculations First-principles calculations

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Crystal orientation dictated epitaxy of ultrawide bandgap 5.4 - 8.6 eV α-(AlGa)2O3 on m-plane sapphire

arXiv

引用

arXiv 2020年

作者： Jinno, Riena Chang, Celesta S. Onuma, Takeyoshi Cho, Yongjin Ho, Shao-Ting Cao, Michael C. Lee, Kevin Protasenko, Vladimir Schlom, Darrell G. Muller, David A. Xing, Huili G. Jena, Debdeep School of Electrical and Computer Engineering Cornell University IthacaNY14853 United States Department of Physics Cornell University IthacaNY14853 United States School of Applied and Engineering Physics Cornell University IthacaNY14853 United States Department of Applied Physics Kogakuin University 2665-1 Hachioji Tokyo192-0015 Japan Department of Material Science and Engineering Cornell University IthacaNY14853 United States Kavli Institute for Nanoscale Science Cornell University IthacaNY14853 United States

Ultra-wide bandgap semiconductors are ushering in the next generation of high power electronics. The correct crystal orientation can make or break successful epitaxy of such semiconductors. Here it is discovered that single-crystalline layers of α-(AlGa)2O3 alloys spanning bandgaps of 5.4-8.6 eV can be grown by molecular beam epitaxy. The key step is found to be the use of m-plane sapphire crystal. The phase transition of the epitaxial layers from the α- to the narrower bandgap β-phase is catalyzed by the c-plane of the crystal. Because the c-plane is orthogonal to the growth front of the m-plane surface of the crystal, the narrower bandgap pathways are eliminated, revealing a route to much wider bandgap materials with structural purity. The resulting energy bandgaps of the epitaxial layers span a range beyond the reach of all other semiconductor families, heralding the successful epitaxial stabilization of the largest bandgap materials family to date. Copyright © 2020, The Authors. All rights reserved.

关键词： Crystal orientation

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Diffusive Electron-phonon Interaction for Terahertz Radiation

Diffusive Electron-phonon Interaction for Terahertz Radiatio...

引用

Progress in Electromagnetic Research Symposium (PIERS)

作者： S. H. Park H. Lee K. Ishioka K. Volz C. J. Stanton Y. D. Jho School of Electrical Engineering and Computer Science Gwangju Institute of Science and Technology Gwangju South Korea National Institute for Materials Science Tsukuba Japan Material Science Center and Faculty of Physics Philipps-University Marburg Germany University of Florida Gainesville United States

ISBN: (数字)9781728134031

ISBN: (纸本)9781728134048

We demonstrate terahertz (THz) electromagnetic wave radiation could induced by interactions between acoustic (AC) phonons and diffusive electrons. AC phonons are generated in thin GaP layer on n -Si, while THz wave was emitted as AC nanowaves encountered diffusively transporting electrons in the Si layer. The pulse-like emission patterns at t=t1 and t2 were in agreement with the temporal periods of the electron-phonon interactions via two main AC packets originating from GaP/Si and air/GaP interfaces. Additionally, the GaP-thickness-dependent THz amplitude was affected primarily by the density profile of the electron reservoir.

关键词： Strain Silicon Springs Phonons Charge carrier processes Acceleration Photonics

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Observation of terahertz gain in two-dimensional magnetoexcitons

arXiv

引用

arXiv 2020年

作者： Li, Xinwei Yoshioka, Katsumasa Zhang, Qi Peraca, Nicolas Marquez Katsutani, Fumiya Gao, Weilu Noe, G. Timothy Watson, John D. Manfra, Michael J. Katayama, Ikufumi Takeda, Jun Kono, Junichiro Department of Electrical and Computer Engineering Rice University HoustonTX77005 United States Department of Physics Graduate School of Engineering Science Yokohama National University Yokohama240-8501 Japan School of Physics Nanjing University Nanjing210093 China Department of Physics and Astronomy Rice University HoustonTX77005 United States Department of Physics and Astronomy Purdue University West LafayetteIN47907 United States Department of Material Science and NanoEngineering Rice University HoustonTX77005 United States

We have observed photoinduced negative optical conductivity, or gain, in the terahertz frequency range in a GaAs multiple-quantum-well structure in a strong perpendicular magnetic field at low temperatures. The gain i... 详细信息

关键词： Polarization

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Perfect intrinsic squeezing at the superradiant phase transition critical point

arXiv

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arXiv 2020年

作者： Hayashida, Kenji Makihara, Takuma Peraca, Nicolas Marquez Padilla, Diego Fallas Pu, Han Kono, Junichiro Bamba, Motoaki Department of Electrical and Computer Engineering Rice University Houston77005 United States Division of Applied Physics Graduate School and Faculty of Engineering Hokkaido University SapporoHokkaido060-8628 Japan Department of Physics and Astronomy Rice University Houston77005 United States Department of Material Science and NanoEngineering Rice University Houston77005 United States Department of Physics Kyoto University Kyoto606-8502 Japan PRESTO Japan Science and Technology Agency Kawaguchi332-0012 Japan

The ground state of the photon–matter coupled system described by the Dicke model is found to be perfectly squeezed at the quantum critical point of the superradiant phase transition (SRPT). In the presence of the counter-rotating photon–atom coupling, the ground state is analytically expressed as a two-mode squeezed vacuum in the basis of photons and atomic collective excitations. The variance of a quantum fluctuation in the two-mode basis vanishes at the SRPT critical point, with its conjugate fluctuation diverging, ideally satisfying the Heisenberg uncertainty principle. Copyright © 2020, The Authors. All rights reserved.

关键词： Photons

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Evaluation of a novel test method for the determination of strain rate-dependent material properties of high-performance fibers

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Procedia Structural Integrity 2019年 17卷 942-948页

作者： Reimar Unger Andreas Nocke Gerald Gerlach Chokri Cherif Technische Universität Dresden Faculty of Mechanical Science and Engineering Institute of Textile Machinery and High Performance Material Technology (ITM) 01062 Dresden Germany Technische Universität Dresden Faculty of Electrical and Computer Engineering Institute of Solid-State Electronics Laboratory (IFE) 01062 Dresden Germany

For reinforcement in fiber reinforced plastic and concrete applications, the knowledge of the high-velocity impact and crash behavior of typically used high-performance fibers, such as carbon fibers (CF), becomes an important aspect for designing and dimensioning new composite components. More important than the impact velocity is the resulting strain rate in the fiber, which defines the failure behavior. In current literature, there is still an open gap for fiber material testing for strain rates between 100 and 1000 1/s, which is difficult to close with the existing measurement setups, i.e. between servo-hydraulic tensile testing machines and Split-Hopkinson-tension-bars. A rotary drive principle is proposed where the challenge arises in coupling the force, in a reliable clamping of the specimens and in high-speed acquisition of the stress-strain curve. In the implementation process, speeds up to 40 m/s were currently achieved, which corresponds to a strain rate of 267 s -1 for a specimen length of 150 mm. The specimen and the moving elements were prepared with stochastic patterns and evaluated by means of digital image correlation (DIC). The force signal is recorded and correlated from a piezoelectric load cell. Additional information on the energy dissipated by the tensile test was acquired by analyzing the engine control records. The evaluation of high-speed images by DIC shows that there is a partially elastic impact and acceleration reaches its maxima before the specimen’s rupture. Thus, for a precise evaluation, the stress equilibrium has to be taken into account and the impact process has to be further optimized.

关键词： strain rate carbon fiber high-performance fiber tensile testing technical yarns

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Magnetic damping in epitaxial fe alloyed with low-atomic-number elements

arXiv

引用

arXiv 2020年

作者： Smith, David A. Rai, Anish Lim, Youngmin Hartnett, Timothy Sapkota, Arjun Srivastava, Abhishek Mewes, Claudia Jiang, Zijian Clavel, Michael Hudait, Mantu K. Viehland, Dwight D. Heremans, Jean J. Balachandran, Prasanna V. Mewes, Tim Emori, Satoru Department of Physics Virginia Tech BlacksburgVA24061 United States Department of Physics and Astronomy University of Alabama TuscaloosaAL35487 United States Center for Materials for Information Technology University of Alabama TuscaloosaAL35487 United States Department of Material Science and Engineering University of Virginia CharlottesvilleVA22904 United States Department of Electrical and Computer Engineering Virginia Tech BlacksburgVA24061 United States Department of Materials Science and Engineering Virginia Tech BlacksburgVA24061 United States Department of Mechanical and Aerospace Engineering University of Virginia CharlottesvilleVA22904 United States

To develop low-moment, low-damping metallic ferromagnets for power-efficient spintronic devices, it is crucial to understand how magnetic relaxation is impacted by the addition of nonmagnetic elements. Here, we compare magnetic relaxation in epitaxial Fe films alloyed with light nonmagnetic elements of V and Al. FeV alloys exhibit lower intrinsic damping compared to pure Fe, reduced by nearly a factor of 2, whereas damping in FeAl alloys increases with Al content. Our experimental and computational results indicate that reducing the density of states at the Fermi level, rather than the average atomic number, has a more significant impact in lowering damping in Fe alloyed with light elements. Moreover, FeV is confirmed to exhibit an intrinsic Gilbert damping parameter of .0.001, among the lowest ever reported for ferromagnetic metals. Copyright © 2020, The Authors. All rights reserved.

关键词： Iron alloys

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Robust Coupling between Structural and Electronic Transitions in a Mott material

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Physical Review Letters 2019年第5期122卷 057601-057601页

作者： Yoav Kalcheim Nikita Butakov Nicolas M. Vargas Min-Han Lee Javier del Valle Juan Trastoy Pavel Salev Jon Schuller Ivan K. Schuller Department of Physics and Center for Advanced Nanoscience University of California San Diego La Jolla California 92093 USA Department of Electrical and Computer Engineering University of California Santa Barbara Santa Barbara California 93106 USA Material Science and Engineering Program University of California San Diego La Jolla California 92093 USA

The interdependences of different phase transitions in Mott materials are fundamental to the understanding of the mechanisms behind them. One of the most important relations is between the ubiquitous structural and electronic transitions. Using IR spectroscopy, optical reflectivity, and x-ray diffraction, we show that the metal-insulator transition is coupled to the structural phase transition in V2O3 films. This coupling persists even in films with widely varying transition temperatures and strains. Our findings are in contrast to recent experimental findings and theoretical predictions. Using V2O3 as a model system, we discuss the pitfalls in measurements of the electronic and structural states of Mott materials in general, calling for a critical examination of previous work in this field. Our findings also have important implications for the performance of Mott materials in next-generation neuromorphic computing technology.

关键词： Crystal growth Crystal orientation Crystal structure Crystal symmetry Crystallization Electronic structure Peierls transition Phase transitions Spin state transition Strain Antiferromagnets Mott insulators Stimuli-responsive materials Strongly correlated systems Thin films Cavity resonators Crystallography Fourier transform infrared spectroscopy Resistivity measurements Scanning techniques Sputtering Strain engineering X-ray diffraction

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