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Layer-dependent optically-induced spin polarization in InSe

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arXiv 2022年

作者： Nelson, Jovan Stanev, Teodor K. Lebedev, Dmitry LaMountain, Trevor Tyler Gish, J. Zeng, Hongfei Shin, Hyeondeok Heinonen, Olle Watanabe, Kenji Taniguchi, Takashi Hersam, Mark C. Stern, Nathaniel P. Applied Physics Program Northwestern University EvanstonIL60208 United States Department of Physics and Astronomy Northwestern University EvanstonIL60208 United States Department of Material Science & Engineering Northwestern University EvanstonIL60208 United States Computational Science Division Argonne National Laboratory LemontIL60439 United States Material Science Division Argonne National Laboratory LemontIL60439 United States Research Center for Functional Materials National Institute for Materials Science 1-1 Namiki Tsukuba305-0044 Japan International Center for Materials Nanoarchitectonics National Institute for Materials Science 1-1 Namiki Tsukuba305-0044 Japan Department of Chemistry Northwestern University EvanstonIL60208 United States Department of Electrical Engineering and Computer Science Northwestern University EvanstonIL60208 United States

Optical control of spin in semiconductors has been pioneered using nanostructures of III-V and II-VI semiconductors, but the emergence of two-dimensional van der Waals materials offers an alternative low-dimensional platform for spintronic phenomena. Indium selenide (InSe), a group-III monochalcogenide van der Waals material, has shown promise for opto-electronics due to its high electron mobility, tunable direct bandgap, and quantum transport. In addition to these confirmed properties, there are predictions of spin-dependent optical selection rules suggesting potential for all-optical excitation and control of spin in a two-dimensional layered material. Despite these predictions, layer-dependent optical spin phenomena in InSe have yet to be explored. Here, we present measurements of layer-dependent optical spin dynamics in few-layer and bulk InSe. Polarized photo-luminescence reveals layer-dependent optical orientation of spin, thereby demonstrating the optical selection rules in few-layer InSe. Spin dynamics are also studied in many-layer InSe using time-resolved Kerr rotation spectroscopy. By applying out-of-plane and in-plane static magnetic fields for polarized emission measurements and Kerr measurements, respectively, the g-factor for InSe was extracted. Further investigations are done by calculating precession values using a k·p model, which is supported by ab-initio density functional theory. Comparison of predicted precession rates with experimental measurements highlights the importance of excitonic effects in InSe for understanding spin dynamics. Optical orientation of spin is an important prerequisite for opto-spintronic phenomena and devices, and these first demonstrations of layer-dependent optical excitation of spins in InSe lay the foundation for combining layer-dependent spin properties with advantageous electronic properties found in this material. Copyright © 2022, The Authors. All rights reserved.

关键词： Spin dynamics

Reliable operation of Cr2O3:Mg/β-Ga2O3 p-n heterojunction diodes at 600◦C

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arXiv 2024年

作者： Callahan, William A. Egbo, Kingsley Lee, Cheng-Wei Ginley, David O'Hayre, Ryan Zakutayev, Andriy Materials Science Center National Renewable Energy Laboratory GoldenCO80401 United States Advanced Energy Systems Graduate Program Colorado School of Mines GoldenCO80401 United States Department of Metallurgical and Materials Engineering Colorado School of Mines GoldenCO80401 United States

β-Ga2O3-based semiconductor heterojunctions have recently demonstrated improved performance at high voltages and elevated temperatures and are thus promising for applications in power electronic devices and harsh-environment sensors. However, the long-term reliability of these ultra-wide band gap (UWBG) semiconductor devices remains barely addressed and may be strongly influenced by chemical reactions at the p-n heterojunction interface. Here, we experimentally demonstrate operation and evaluate the reliability of Cr2O3:Mg/β-Ga2O3 p-n heterojunction diodes at during extended operation at 600◦C, as well as after 30 repeated cycles between 25-550◦C. The calculated pO3-temperature phase stability diagram of the Ga-Cr-O material system predicts that Ga2O3 and Cr2O3 should remain thermodynamically stable in contact with each other over a wide range of oxygen pressures and operating temperatures. The fabricated Cr2O3:Mg/β-Ga2O3 p-n heterojunction diodes show room-temperature on/off ratios >104 at ±5V and a breakdown voltage (VBr) of -390V. The leakage current increases with increasing temperature up to 600◦C, which is attributed to Poole-Frenkel emission with a trap barrier height of 0.19 eV. Over the course of a 140-hour thermal soak at 600◦C, both the device turn-on voltage and on-state resistance increase from 1.08V and 5.34 mΩ-cm2 to 1.59V and 7.1 mΩ-cm2 respectively. This increase is attributed to the accumulation of Mg and MgO at the Cr2O3/Ga2O3 interface as observed from TOF-SIMS analysis. These findings inform future design strategies of UWBG semiconductor devices for harsh environment operation and underscore the need for further reliability assessments for β-Ga2O3 based devices. © 2024, CC BY.

关键词： Gallium compounds

Large magnetic moment in flexoelectronic silicon at room temperature

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arXiv 2021年

作者： Lou, Paul C. Katailiha, Anand Bhardwaj, Ravindra G. Beyermann, Ward P. Juraschek, Dominik M. Kumar, Sandeep Department of Mechanical Engineering University of California RiversideCA92521 United States Department of Physics and Astronomy University of California RiversideCA92521 United States Harvard John A. Paulson School of Engineering and Applied Sciences Harvard University CambridgeMA02145 United States Materials Science and Engineering Program University of California RiversideCA92521 United States

Time-dependent rotational electric polarizations have been proposed to generate temporally varying magnetic moments, for example, through a combination of ferroelectric polarization and optical phonons. This phenomenon has been called dynamical multiferroicity, but explicit experimental demonstrations have been elusive to date. Here, we report the detection of a temporal magnetic moment as high as 1.2 µB/atom in charge-doped thin film of silicon under flexural strain. We demonstrate that the magnetic moment is generated by a combination of electric polarization arising from a flexoelectronic charge separation along the strain gradient and the deformation potential of phonons. The effect can be controlled by adjusting the external strain gradient, doping concentration and dopant, and can be regarded as a dynamical multiferroic effect involving flexoelectronics polarization instead of ferroelectricity. The discovery of a large magnetic moment in silicon may enable the use of non-magnetic and non-ferroelectric semiconductors in various multiferroic and spintronic applications. © 2021, CC BY.

关键词： Magnetic moments

Effect of Heat Treatment on Improving Oer Activity of Nifeooh Based Aerogels: A Combined Experimental and Theoretical Study

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SSRN

SSRN 2024年

作者： Lakhanlal Rimon, Or Moschkowitsch, Wenjamin Elbaz, Lior Toroker, Maytal Caspary Department of Materials Science and Engineering Technion-Israel Institute of Technology Haifa3200003 Israel Bar Ilan University Ramat-Gan52900 Israel The Nancy and Stephen Grand Technion Energy Program Technion - Israel Institute of Technology Haifa3200003 Israel

Enhanced catalytic activity of oxygen evolution reaction (OER) catalysts can make water electrolysis more efficient. This study focuses on the use of a simple strategy of heat treatment to enhance the catalytic activity of NiFeOOH-based aerogels. The study shows that heat treatment of this aerogel at 150 °C leads to significant improvement in its catalytic activity, as evident in the staircase voltammetry results. To understand how heat treatment improves the catalytic activity, a DFT+U calculation was carried out on heat-treated and non-heat treated catalysts. The calculation shows that the overpotential for OER decreases with heat treatment, which is related to the relative stability of the intermediates in heat-treated and non-heat treated catalysts. Also, it has been found that heat treatment decreases work function, which might improve charge transfer and, thus, catalytic activity. Our calculations are in line with the experimental results that demonstrate the potential of controlling water content on catalytic efficiency. © 2024, The Authors. All rights reserved.

关键词： Heat treatment

Pressure-induced phase transition in La1−xSmxO0.5F0.5BiS2

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Physical Review B 2015年第9期92卷 094507-094507页

作者： Y. Fang D. Yazici B. D. White M. B. Maple Materials Science and Engineering Program University of California San Diego La Jolla California 92093 USA Center for Advanced Nanoscience University of California San Diego La Jolla California 92093 USA Department of Physics University of California San Diego La Jolla California 92093 USA

Electrical resistivity measurements on La1−xSmxO0.5F0.5BiS2(x=0.1,0.3,0.6,0.8) have been performed under applied pressures up to 2.6 GPa from 2 K to room temperature. The superconducting transition temperature Tc of each sample significantly increases at a Sm-concentration-dependent pressure Pt, indicating a pressure-induced phase transition from a low-Tc to a high-Tc phase. At ambient pressure, Tc increases dramatically from 2.8 K at x=0.1 to 5.4 K at x=0.8; however, the Tc values at P>Pt decrease slightly with x, and Pt shifts to higher pressures with Sm substitution. In the normal state, semiconducting-like behavior is suppressed, and metallic conduction is induced with increasing pressure in all of the samples. These results suggest that the pressure dependence of Tc for the BiS2-based superconductors is related to the lattice parameters at ambient pressure and enable us to estimate the evolution of Tc for SmO0.5F0.5BiS2 under pressure.

关键词： PHASE transformations (Physics) LANTHANUM compounds ELECTRICAL resistivity TEMPERATURE effect SUBSTITUTION reactions SUPERCONDUCTORS

Probing strong Kondo disorder with measurements of thermoelectric power

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Physical Review B 2014年第23期90卷 235104-235104页

作者： B. D. White K. Huang M. B. Maple Department of Physics University of California San Diego La Jolla California 92093 USA Center for Advanced Nanoscience University of California San Diego La Jolla California 92093 USA Materials Science and Engineering Program University of California San Diego La Jolla California 92093 USA

Measurements of thermoelectric power S(T) on the Kondo disorder system CePt4Ge12−xSbx are remarkably sensitive to the distribution of Kondo temperatures P(TK), which develops out of a single Kondo temperature TK in CePt4Ge12 and is governed by the degree to which hybridization is disordered. Three distinct S(T) behaviors are observed in concentration regions which coincide with the boundaries of Fermi-liquid, non-Fermi-liquid, and antiferromagnetically ordered ground states in this system. In the non-Fermi-liquid region, S(T)/T diverges logarithmically with decreasing temperature over nearly one decade in the case of x=0.84.

关键词： KONDO effect THERMOELECTRIC power FERMI liquids ANTIFERROMAGNETIC materials MAGNETIC properties

Two-dimensional materials for future information technology: status and prospects

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science China(Information sciences) 2024年第6期67卷 1-147页

作者： Hao QIU Zhihao YU Tiange ZHAO Qi ZHANG Mingsheng XU Peifeng LI Taotao LI Wenzhong BAO Yang CHAI Shula CHEN Yiqi CHEN Hui-Ming CHENG Daoxin DAI Zengfeng DI Zhuo DONG Xidong DUAN Yuhan FENG Yu FU Jingshu GUO Pengwen GUO Yue HAO Jun HE Xiao HE Jingyi HU Weida HU Zehua HU Xinyue HUANG Ziyang HUANG Ali IMRAN Ziqiang KONG Jia LI Qian LI Weisheng LI Lei LIAO Bilu LIU Can LIU Chunsen LIU Guanyu LIU Kaihui LIU Liwei LIU Sheng LIU Yuan LIU Donglin LU Likuan MA Feng MIAO Zhenhua NI Jing NING Anlian PAN Tian-Ling REN Haowen SHU Litao SUN Yue SUN Quanyang TAO Zi-Ao TIAN Dong WANG Hao WANG Haomin WANG Jialong WANG Junyong WANG Wenhui WANG Xingjun WANG Yeliang WANG Yuwei WANG Zhenyu WANG Yao WE... Department of Applied Physics The Hong Kong Polytechnic University Key Laboratory for Micro-Nano Physics and Technology of Hunan Province College of Materials Science and EngineeringHunan University College of Integrated Circuits Zhejiang University Shenzhen Geim Graphene Center Shenzhen Key Laboratory of Layered Materials for Value-Added ApplicationsTsinghua-Berkeley Shenzhen Institute & Institute of Materials ResearchTsinghua Shenzhen International Graduate SchoolTsinghua University State Key Laboratory of Extreme Photonics and Instrumentation College of Optical Science and EngineeringInternational Research Center for Advanced PhotonicsZijingang CampusZhejiang University National Key Laboratory of Materials for Integrated Circuits Shanghai Institute of Microsystem and Information TechnologyChinese Academy of Sciences CAS Key Laboratory of Nanophotonic Materials and Devices & Key Laboratory of Nanodevices and Applications i-LabSuzhou Institute of Nano-Tech and Nano-Bionics (SINANO)Chinese Academy of Sciences College of Chemistry and Chemical Engineering Hunan University Key Laboratory of Quantum State Construction and Manipulation (Ministry of Education) Department of PhysicsRenmin University of China School of Integrated Circuits Beijing National Research Center for Information Science and Technology (BNRist)Tsinghua University School of Electronic Science and Engineering Nanjing University The State Key Discipline Laboratory of Wide Band Gap Semiconductor Technology Shaanxi Joint Key Laboratory of GrapheneSchool of MicroelectronicsXidian University Key Laboratory of Artificial Micro- and Nano-Structures of Ministry of Education School of Physics and TechnologyWuhan University School of Integrated Circuits Huazhong University of Science and Technology Center for Nanochemistry (CNC) Beijing Science and Engineering Center for NanocarbonsBeijing National Laboratory for Molecular SciencesCollege of Chemistry and Molecular EngineeringPeking University State Key Laboratory for Artificial Microstruct

Over the past 70 years, the semiconductor industry has undergone transformative changes,largely driven by the miniaturization of devices and the integration of innovative structures and materials. Two-dimensional(2D) materials like transition metal dichalcogenides(TMDs) and graphene are pivotal in overcoming the limitations of silicon-based technologies, offering innovative approaches in transistor design and functionality, enabling atomic-thin channel transistors and monolithic 3D integration. We review the important progress in the application of 2D materials in future information technology, focusing in particular on microelectronics and optoelectronics. We comprehensively summarize the key advancements across material production, characterization metrology, electronic devices, optoelectronic devices, and heterogeneous integration on silicon. A strategic roadmap and key challenges for the transition of 2D materials from basic research to industrial development are outlined. To facilitate such a transition, key technologies and tools dedicated to 2D materials must be developed to meet industrial standards, and the employment of AI in material growth, characterizations, and circuit design will be essential. It is time for academia to actively engage with industry to drive the next 10 years of 2D material research.

关键词： two-dimensional (2D) materials information technology production technology standardization of characterization microelectronic devices optoelectronic devices multi-functional integration

High-pressure effects on nonfluorinated BiS2-based superconductors La1−xMxOBiS2 (M=Ti and Th)

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Physical Review B 2017年第21期96卷 214505-214505页

作者： Y. Fang D. Yazici I. Jeon M. B. Maple Materials Science and Engineering Program University of California San Diego La Jolla California 92093 USA Center for Advanced Nanoscience University of California San Diego La Jolla California 92093 USA Department of Physics University of California San Diego La Jolla California 92093 USA

Layered LnOBiS2 (where Ln represents a lanthanide element) compounds with Ln = La, Ce, Pr, Nd, and Yb can be rendered conducting and superconducting via two routes, substitution of F for O or the tetravalent ions Ti, Zr, Hf, and Th for trivalent Ln ions. Electrical resistivity measurements on nonfluorinated La0.80Ti0.20OBiS2 and La0.85Th0.15OBiS2 superconductors were performed between ∼1.5 and 300 K and under pressure up to 2.4 GPa. For both compounds, the superconducting transition temperature Tc, which is ∼2.9K at ambient pressure, gradually increases with pressure to 3.2–3.7 K at ∼1GPa, above which it is suppressed and the superconducting transitions become very broad. Measurements of the normal-state electrical resistivity of the two compounds reveal discontinuous changes in the resistivity as a function of pressure at ∼0.6GPa. Surprisingly, above 1.3 GPa, semiconductinglike behavior reappears in La0.80Ti0.20OBiS2. This paper reveals a new high-pressure phase of La1−xMxOBiS2 containing the tetravalent ions M=Ti, Th which does not favor superconductivity. In contrast, application of pressure to fluorinated LaO0.5F0.5BiS2 produces an abrupt tetragonal-monoclinic transition to a metallic phase with an enhanced Tc. These results demonstrate that the response of the normal and superconducting properties of LaOBiS2-based compounds depends strongly on the atomic site where the electron donor ions are substituted.

关键词： Phase transitions by order Pressure effects Superconductivity Transport phenomena

Compositionally Complex Perovskite Oxides for Solar Thermochemical Water Splitting

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arXiv 2022年

作者： Zhang, Dawei De Santiago, Héctor A. Xu, Boyuan Liu, Cijie Trindell, Jamie Li, Wei Park, Jiyun Rodriguez, Mark A. Coker, Eric N. Sugar, Josh McDaniel, Anthony Lany, Stephan Ma, Liang Wang, Yi Collins, Gregory Tian, Hanchen Li, Wenyuan Qi, Yue Liu, Xingbo Luo, Jian Program of Materials Science and Engineering University of California San Diego La Jolla CA92093 United States Department of Mechanical and Aerospace Engineering Benjamin M. Statler College of Engineering and Mineral Resources West Virginia University MorgantownWV26506 United States Department of Physics Brown University ProvidenceRI02912 United States Sandia National Laboratories LivermoreCA94551 United States School of Engineering Brown University ProvidenceRI02912 United States Sandia National Laboratories AlbuquerqueNM87185 United States Materials Science Center National Renewable Energy Laboratory GoldenCO80401 United States School of Materials Science and Engineering Hebei University of Engineering Hebei Province Handan056038 China Department of Chemical and Biomedical Engineering Benjamin M. Statler College of Engineering and Mineral Resources West Virginia University MorgantownWV26506 United States Department of NanoEngineering University of California San Diego La Jolla CA92093 United States

Solar thermochemical hydrogen generation (STCH) is a promising approach for eco-friendly H2 production, but conventional STCH redox compounds often suffer from thermodynamic and kinetic limitations with limited tunability. Expanding from the nascent high-entropy ceramics field, this study explores a new class of compositionally complex perovskite oxides (La0.8Sr0.2)(Mn(1-x)/3Fe(1-x)/3CoxAl(1-x)/3)O3 for STCH. In situ X-ray diffraction demonstrates the phase stability during redox cycling and in situ X-ray photoelectron spectroscopy shows preferential redox of Co. The extent of reduction increases, but the intrinsic kinetics decreases, with increased Co content. Consequently, (La0.8Sr0.2)(Mn0.2Fe0.2Co0.4Al0.2)O3-δ achieves an optimal balance between the thermodynamics and kinetics properties. The combination of a moderate enthalpy of reduction, high entropy of reduction, and preferable surface oxygen exchange kinetics enables a maximum H2 yield of 395 ± 11 μmol g-1 in a short 1-hour redox duration. Entropy stabilization expectedly contributes to the structure stability during redox without phase transformation, which enables an exceptional STCH stability for >50 cycles under harsh interrupted conditions. The underlying redox mechanism is further elucidated by the density functional theory based parallel Monte Carlo computation, which represents a new computation paradigm first established here. This study suggests a new class of non-equimolar compositionally complex ceramics for STCH and chemical looping. © 2022, CC BY.

关键词： Entropy