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Temperature-dependent thermal and thermoelectric properties of n-type and p-type Sc1−xMgxN

Physical Review B 2018年第8期97卷 085301-085301页

作者： Bivas Saha Jaime Andres Perez-Taborda Je-Hyeong Bahk Yee Rui Koh Ali Shakouri Marisol Martin-Gonzalez Timothy D. Sands Department of Materials Science and Engineering University of California Berkeley California 94720 USA Instituto de Microelectrónica de Madrid CSIC C/ Isaac Newton 8 Tres Cantos 28760 Madrid Spain Department of Mechanical and Materials Engineering University of Cincinnati Cincinnati Ohio 45221 USA School of Electrical and Computer Engineering Purdue University West Lafayette Indiana 47907 USA Bradley Department of Electrical and Computer Engineering and Department of Materials Science and Engineering Virginia Tech Blacksburg Virginia 24061 USA

Scandium Nitride (ScN) is an emerging rocksalt semiconductor with octahedral coordination and an indirect bandgap. ScN has attracted significant attention in recent years for its potential thermoelectric applications, as a component material in epitaxial metal/semiconductor superlattices, and as a substrate for defect-free GaN growth. Sputter-deposited ScN thin films are highly degenerate n-type semiconductors and exhibit a large thermoelectric power factor of ∼3.5×10−3W/m−K2 at 600–800 K. Since practical thermoelectric devices require both n- and p-type materials with high thermoelectric figures-of-merit, development and demonstration of highly efficient p-type ScN is extremely important. Recently, the authors have demonstrated p-type Sc1−xMgxN thin film alloys with low MgxNy mole-fractions within the ScN matrix. In this article, we demonstrate temperature dependent thermal and thermoelectric transport properties, including large thermoelectric power factors in both n- and p-type Sc1−xMgxN thin film alloys at high temperatures (up to 850 K). Employing a combination of temperature-dependent Seebeck coefficient, electrical conductivity, and thermal conductivity measurements, as well as detailed Boltzmann transport-based modeling analyses of the transport properties, we demonstrate that p-type Sc1−xMgxN thin film alloys exhibit a maximum thermoelectric power factor of ∼0.8×10−3W/m−K2 at 850 K. The thermoelectric properties are tunable by adjusting the MgxNy mole-fraction inside the ScN matrix, thereby shifting the Fermi energy in the alloy films from inside the conduction band in case of undoped n-type ScN to inside the valence band in highly hole-doped p-type Sc1−xMgxN thin film alloys. The thermal conductivities of both the n- and p-type films were found to be undesirably large for thermoelectric applications. Thus, future work should address strategies to reduce the thermal conductivity of Sc1−xMgxN thin-film alloys, without affecting the power factor for improved

关键词： Semiconductors Thermal conductivity Alloys Thin films

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Fast Exact Computation of Expected HyperVolume Improvement

arXiv

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arXiv 2018年

作者： Zhao, Guang Arróyave, Raymundo Qian, Xiaoning Department of Electrical and Computer Engineering Texas A&M University Department of Materials Science and Engineering Texas A&M University

In multi-objective Bayesian optimization and surrogate-based evolutionary algorithms, Expected HyperVolume Improvement (EHVI) is widely used as the acquisition function to guide the search approaching the Pareto front. This paper focuses on the exact calculation of EHVI given a nondominated set, for which the existing exact algorithms are complex and can be inefficient for problems with more than three objectives. Integrating with different decomposition algorithms, we propose a new method for calculating the integral in each decomposed high-dimensional box in constant time. We develop three new exact EHVI calculation algorithms based on three region decomposition methods. The first grid-based algorithm has a complexity of O(m · nm) with n denoting the size of the nondominated set and m the number of objectives. The Walking Fish Group (WFG)based algorithm has a worst-case complexity of O(m · 2n) but has a better average performance. These two can be applied for problems with any m. The third CLM-based (Beume et al., 2009) algorithm is only for m = 3 and asymptotically optimal with complexity Θ(n log n). Performance comparison results show that all our three algorithms are at least twice faster than the state-of-the-art algorithms with the same decomposition methods. When m > 3, our WFG-based algorithm can be over 102 faster than the corresponding existing algorithms. Our algorithm is demonstrated in an example involving efficient multi-objective material design with Bayesian optimization. Copyright © 2018, The Authors. All rights reserved.

关键词： Evolutionary algorithms

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Switchable X-ray orbital angular momentum from an artificial spin ice

arXiv

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arXiv 2020年

作者： Woods, Justin Chen, Xiaoqian Chopdekar, Rajesh V. Farmer, Barry Mazzoli, Claudio Koch, Roland Tremsin, Anton Hu, Wen Scholl, Andreas Kevan, Steve Wilkins, Stuart Kwok, Wai-Kwong De Long, Lance E. Roy, Sujoy Todd Hastings, J. Department of Physics and Astronomy University of Kentucky LexingtonKY40506 United States Materials Science Division Argonne National Laboratory LemontIL60439 United States Advanced Light Source Lawrence Berkeley National Laboratory BerkeleyCA94720 United States Department of Electrical and Computer Engineering University of Kentucky LexingtonKY40506 United States National Synchrotron Light Source II Brookhaven National Laboratory UptonNY11973 United States Space Sciences Laboratory University of California BerkeleyCA94720 United States

Artificial spin ices (ASI) have been widely investigated as magnetic metamaterials with exotic properties governed by their geometries. In parallel, interest in X-ray photon orbital angular momentum (OAM) has been rapidly growing. Here we show that a square ASI with a programmed topological defect, a double edge dislocation, imparts OAM to scattered X-rays. Unlike single dislocations, a double dislocation does not introduce magnetic frustration, and the ASI equilibrates to its antiferromagnetic (AF) ground state. The topological charge of the defect differs with respect to the structural and magnetic order;thus, X-ray diffraction from the ASI produces photons with even and odd OAM quantum numbers at the structural and AF Bragg conditions, respectively. The magnetic transitions of the ASI allow the AF OAM beams to be switched on and off by modest variations of temperature and applied magnetic field. These results demonstrate ASIs can serve as metasurfaces for reconfigurable X-ray optics that could enable selective probes of electronic and magnetic properties. Copyright © 2020, The Authors. All rights reserved.

关键词： Ground state

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Observation of multifractality of light in prime number arrays

arXiv

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arXiv 2020年

作者： Sgrignuoli, Fabrizio Gorsky, Sean Britton, Wesley A. Zhang, Ran Riboli, Francesco Dal Negro, Luca Department of Electrical and Computer Engineering and Photonics Center Boston University 8 Saint Mary's St. BostonMA02215 United States Division of Materials Science and Engineering Boston University 15 Saint Mary's St. BrooklineMA02446 United States Instituto Nazionale di Ottica CNR Via Nello Carrara 1 Sesto Fiorentino50019 Italy European Laboratory for Nonlinear Spectroscopy via Nello Carrara 1 Sesto Fiorentino50019 Italy Department of Physics Boston University 590 Commonwealth Ave. BostonMA02215 United States

Many natural patterns and shapes, such as meandering coastlines, clouds, or turbulent ows, exhibit a characteristic complexity mathematically described by fractal geometry [1]. In recent years, the engineering of self-similar structures in photonics and nano-optics technology [2{ 7] enabled the manipulation of light states beyond periodic [8] or disordered systems [9, 10], adding novel functionalities to complex optical media [11{14] with applications to nano-devices and metamaterials [15{17]. Here, we extend the reach of "fractal photonics" by experimentally demonstrating multifractality of light in engineered arrays of dielectric nanoparticles. Our findings stimulate fundamental questions on the nature of transport and localization of wave excitations with multi-scale uctuations beyond what is possible in traditional fractal systems [2{7]. Moreover, our approach establishes structure-property relationships that can readily be transferred to planar semiconductor electronics [18] and to artificial atomic lattices [19], enabling the exploration of novel quantum phases and manybody effects that emerge directly from fundamental structures of algebraic number theory. Copyright © 2020, The Authors. All rights reserved.

关键词： Fractals

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Carbon Nanotubes: Colors of Single-Wall Carbon Nanotubes (Adv. Mater. 8/2021)

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Advanced materials 2021年第8期33卷

作者： Nan Wei Ying Tian Yongping Liao Natsumi Komatsu Weilu Gao Alina Lyuleeva-Husemann Qiang Zhang Aqeel Hussain Er-Xiong Ding Fengrui Yao Janne Halme Kaihui Liu Junichiro Kono Hua Jiang Esko I. Kauppinen Department of Applied Physics Aalto University School of Science Aalto 00076 Finland Department of Physics Dalian Maritime University Dalian 116026 China Department of Electrical and Computer Engineering Rice University Houston TX 77005 USA School of Physics Academy for Advanced Interdisciplinary Studies Collaborative Innovation Center of Quantum Matter Peking University Beijing 100871 China Department of Physics and Astronomy Rice University Houston TX 77005 USA Department of Materials Science and NanoEngineering Rice University Houston TX 77005 USA

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Characterization of Ligand Exchange in 2D Hybrid Molecule-nanoparticle Superlattices

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Microscopy and Microanalysis 2018年第S1期24卷 1722-1723页

作者： Sahar Hihath Cliff McCold Katia March Josh L. Hihath Department of Electrical and Computer Engineering University of California Davis CA Department of Materials Science and Engineering University of California Davis CA Eyring Materials Center Arizona State University Tempe AZ

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Atomic-Scale Defect Detection by Nonlinear Light Scattering and Localization

arXiv

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arXiv 2020年

作者： Shafiei, Farbod Orzali, Tommaso Vert, Alexey Miri, Mohammad-Ali Hung, P.Y. Wong, Man Hoi Alù, Andrea Bersuker, Gennadi Downer, Michael C. Department of Physics University of Texas at Austin AustinTX United States SEMATECH AlbanyNY United States Sunny Polytechnic Institute AlbanyNY United States Department of Electrical and Computer Engineering University of Texas at Austin AustinTX United States Department of Physics Queens College of the CUNY QueensNY United States Photonics Initiative Advanced Science Research Center CUNY New YorkNY United States Physics Program Graduate Center CUNY New YorkNY United States Aerospace Corporation Los AngelesCA United States

Hetero-epitaxial crystalline films underlie many electronic and optical technologies but are prone to forming defects at their hetero-interfaces. Atomic-scale defects such as threading dislocations that propagate into a film impede the flow of charge carriers and light degrading electrical/optical performance of devices. Diagnosis of sub-surface defects traditionally requires time-consuming invasive techniques such as cross–sectional transmission electron microscopy. Using III-V films grown on Si, we have demonstrated noninvasive, bench-top diagnosis of sub-surface defects by optical second-harmonic scanning probe microscope. We observed a high-contrast pattern of sub-wavelength "hot spots" caused by scattering and localization of fundamental light by defect scattering sites. Size of these observed hotspots are strongly correlated to the density of dislocation defects. Our results not only demonstrate a global and versatile method for diagnosing sub-surface scattering sites but uniquely elucidate optical properties of disordered media. An extension to third harmonics would enable irregularities detection in non-χ(2) materials making the technique universally applicable. Copyright © 2020, The Authors. All rights reserved.

关键词： High resolution transmission electron microscopy

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Strong terahertz plasmonic resonances in thin-film Cd3As2: a three-dimensional Dirac semimetal

Strong terahertz plasmonic resonances in thin-film Cd3As2: a...

引用

International Conference on Infrared and Millimeter Waves

作者： Ashish Chanana Joshua Winger Prashanth Gopalan Neda Lotfizadeh Vikram Deshpande Ajay Nahata Michael Scarpulla Berardi Sensale-Rodriguez Department of Electrical and Computer Engineering Department of Materials Science and Engineering Department of Physics and Astronomy University of Utah Salt Lake City USA

Linear energy band dispersion in Dirac semimetals has been associated with strong plasmon coupling in terahertz regime. Graphene, in this regard, has been projected to play crucial role in terahertz optoelectronics due to high carrier mobility and conductivity. However, in the realm of quantum materials, a three-dimension analogue of graphene, Cd 3 As 2 , so called 3D semimetal, has been shown to have carrier mobility and fermi-velocity well exceeding that in graphene. We experimentally demonstrate synthesis of high-quality large-area Cd 3 As 2 thin-films and realization of THz plasmonic structures. The structures exhibit quality factor ~5, at frequency of ~0.7 THz, the highest reported to-date at room temperature in any semiconductor or semimetal. Our results evidence that the 3D nature of Cd 3 As 2 provides for a more robust platform for terahertz applications than what is otherwise possible in graphene.

关键词： Plasmons Graphene Conductivity Films Dispersion Three-dimensional displays Q-factor

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Entanglement properties of disordered quantum spin chains with long-range antiferromagnetic interactions

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Physical Review B 2020年第21期102卷 214201-214201页

作者： Y. Mohdeb J. Vahedi N. Moure A. Roshani Hyun-Yong Lee R. N. Bhatt Stefan Kettemann Stephan Haas Department of Physics and Earth Sciences Jacobs University Bremen Bremen 28759 Germany Technische Universität Braunschweig Institut für Mathematische Physik Mendelssohnstr. 3 38106 Braunschweig Germany Department of Physics Sari Branch Islamic Azad University Sari 48164-194 Iran Department of Physics and Astronomy University of Southern California Los Angeles California 90089-0484 USA Department of Applied Physics Graduate School Korea University Sejong 30019 Korea Division of Display and Semiconductor Physics Korea University Sejong 30019 Korea Interdisciplinary Program in EċICT-Culture-Sports Convergence Korea University Sejong 30019 Korea Department of Electrical Engineering Princeton University Princeton New Jersey 08544 USA School of Natural Sciences Institute for Advanced Study Princeton New Jersey 08540 USA Division of Advanced Materials Science Pohang University of Science and Technology (POSTECH) Pohang 790-784 Korea

Entanglement measures are useful tools in characterizing otherwise unknown quantum phases and indicating transitions between them. Here we examine the concurrence and entanglement entropy in quantum spin chains with random long-range couplings, spatially decaying with a power-law exponent α. Using the strong disorder renormalization group (SDRG) technique, we find by analytical solution of the master equation a strong disorder fixed point, characterized by a fixed point distribution of the couplings with a finite dynamical exponent, which describes the system consistently in the regime α>12. A numerical implementation of the SDRG method yields a power-law spatial decay of the average concurrence, which is also confirmed by exact numerical diagonalization. However, we find that the lowest-order SDRG approach is not sufficient to obtain the typical value of the concurrence. We therefore implement a correction scheme which allows us to obtain the leading-order corrections to the random singlet state. This approach yields a power-law spatial decay of the typical value of the concurrence, which we derive both by a numerical implementation of the corrections and by analytics. Next, using numerical SDRG, the entanglement entropy (EE) is found to be logarithmically enhanced for all α, corresponding to a critical behavior with an effective central charge c=ln(2), independent of α. This is confirmed by an analytical derivation. Using numerical exact diagonalization (ED), we confirm the logarithmic enhancement of the EE and a weak dependence on α. For a wide range of partition size l, the EE fits a critical behavior with a central charge close to c=1, which is the same as for the clean Haldane-Shastry model with a power-law-decaying interaction with α=2. Only for small l≪L, in a range which increases with the number of spins N, we find deviations which are rather consistent with the strong disorder fixed point central charge c=ln(2). Furthermore, we find using ED that the conc

关键词： Magnetism Quantum entanglement Disordered systems Doped semiconductors Density matrix methods Exact diagonalization Renormalization group Tensor network methods

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Sustainable Fuel Production: Sustainable Fuel Production from Ambient Moisture via Ferroelectrically Driven MoS2Nanosheets (Adv. Mater. 25/2020)

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Advanced materials 2020年第25期32卷

作者： Lin Yang Leyi Loh Dilip Krishna Nandakumar Wanheng Lu Mengqi Gao Xue Le Charlotte Wee Kaiyang Zeng Michel Bosman Swee Ching Tan Department of Materials Science and Engineering National University of Singapore 9 Engineering Drive 1 Singapore 117575 Singapore Department of Electrical and Computer Engineering National University of Singapore 4 Engineering Drive 3 Singapore 117583 Singapore Department of Mechanical Engineering National University of Singapore 9 Engineering Drive 1 Singapore 117576 Singapore

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