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Reverse Doping Asymmetry in Semiconductor Thin Films Using External Voltage

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arXiv 2022年

作者： Liu, Kai Yi, Zhibin Luo, Guangfu Department of Materials Science and Engineering Southern University of Science and Technology Guangdong Shenzhen518055 China Guangdong Provincial Key Laboratory of Computational Science and Material Design Southern University of Science and Technology Guangdong Shenzhen518055 China

Doping asymmetry is a notable phenomenon with semiconductors and a particularly longstanding challenge limiting the applications of most wide-band-gap semiconductors, which are inherent of spontaneous heavy n- or p-type doping because of their extreme band edges. This study theoretically shows that by applying a proper external voltage on materials during their growth or doping processes, we can largely tune the band edges and consequently reverse the doping asymmetry in semiconductor thin films. We take zinc oxide as a touchstone and computationally demonstrate that this voltage-assisted-doping approach efficiently suppresses the spontaneous n-type defects by around four orders under three distinct growth conditions and successfully generates p-type zinc oxide up to the lowest acceptor levels. The proposed approach is insensitive to materials, growth conditions, or defects origins, and thus offers a general solution to the doping asymmetry in semiconductor thin films. © 2022, CC BY.

关键词： Wide band gap semiconductors

Rational design of large anomalous Nernst effect in Dirac semimetals

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arXiv 2022年

作者： Wang, Panshuo Hu, Zongxiang Wu, Xiaosong Liu, Qihang Shenzhen Institute for Quantum Science and Engineering Department of Physics Southern University of Science and Technology Shenzhen518055 China State Key Laboratory for Artificial Microstructure and Mesoscopic Physics Frontiers Science Center for Nano-optoelectronics Collaborative Innovation Center of Quantum Matter Peking University Beijing China Guangdong Provincial Key Laboratory of Computational Science and Material Design Southern University of Science and Technology Shenzhen518055 China Shenzhen Key Laboratory of Advanced Quantum Functional Materials and Devices Southern University of Science and Technology Shenzhen518055 China

Anomalous Nernst effect generates a transverse voltage perpendicular to the temperature gradient. It has several advantages compared with the longitudinal thermoelectricity for energy conversion, such as decoupling of electronic and thermal transports, higher flexibility, and simpler lateral structure. However, a design principle beyond specific materials systems for obtaining a large anomalous Nernst conductivity (ANC) is still absent. In this work, we theoretically demonstrate that a pair of Dirac nodes under a Zeeman field manifests a double-peak anomalous Hall conductivity curve with respect to the chemical potential and a compensated carriers feature, leading to an enhanced ANC pinning at the Fermi level compared with that of a simple Weyl semimetal with two Weyl nodes. Based on first-principles calculations, we then provide two Dirac semimetal candidates, i.e., Na3Bi and NaTeAu, and show that under a Zeeman field they exhibit a sizable ANC value of 0.4 A/(m ∙ K) and 1.3 A/(m ∙ K), respectively, near the Fermi level. Our work provides a design principle with a prototype band structure for enhanced ANC pinning at Fermi level, shedding light on the inverse design of other specific functional materials base on electronic structure. Copyright © 2022, The Authors. All rights reserved.

关键词： Sodium alloys

Spectroscopic signature of obstructed surface states in SrIn2P2

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arXiv 2023年

作者： Liu, Xiang-Rui Deng, Hanbin Liu, Yuntian Yin, Zhouyi Chen, Congrun Zhu, Yu-Peng Yang, Yichen Jiang, Zhicheng Liu, Zhengtai Ye, Mao Shen, Dawei Yin, Jia-Xin Wang, Kedong Liu, Qihang Zhao, Yue Liu, Chang Guangdong Shenzhen518055 China International Quantum Academy Guangdong Shenzhen518048 China State Key Laboratory of Functional Materials for Informatics Shanghai Institute of Microsystem and Information Technology Chinese Academy of Sciences Shanghai200050 China Department of Physics Princeton University PrincetonNJ08544 United States Guangdong Provincial Key Laboratory of Computational Science and Material Design Southern University of Science and Technology Shenzhen518055 China

The century-long development of surface sciences has witnessed the discoveries of a variety of quantum states. In the recently proposed "obstructed atomic insulators", insulators with symmetric charges pinned at virtual sites where no real atoms reside, the cleavage through these sites could lead to a set of obstructed surface states with partial occupation. Here, utilizing scanning tunneling microscopy, angle-resolved photoemission spectroscopy and first-principles calculations, we observe spectroscopic signature of obstructed surface states in SrIn2P2. We find a pair of surface states originated from the pristine obstructed surface states split by a unique surface reconstruction. The upper branch is marked with a striking differential conductance peak followed by negative differential conductance, signaling its localized nature, while the lower branch is found to be highly dispersive. This pair of surface states is in consistency with our calculational results. Our finding not only demonstrates a surface quantum state induced by a new type of bulk-boundary correspondence, but also provides a platform for exploring efficient catalysts and related surface engineering. © 2023, CC BY.

关键词： Surface states

Spin-Group Symmetry in Magnetic materials with Negligible Spin-Orbit Coupling

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Physical Review X 2022年第2期12卷 021016-021016页

作者： Pengfei Liu Jiayu Li Jingzhi Han Xiangang Wan Qihang Liu Shenzhen Institute for Quantum Science and Engineering and Department of Physics Southern University of Science and Technology Shenzhen 518055 China School of Physics Peking University Beijing 100871 People’s Republic of China National Laboratory of Solid State Microstructures and School of Physics Nanjing University Nanjing 210093 China and Collaborative Innovation Center of Advanced Microstructures Nanjing University Nanjing 210093 China Guangdong Provincial Key Laboratory of Computational Science and Material Design Southern University of Science and Technology Shenzhen 518055 China Shenzhen Key Laboratory of Advanced Quantum Functional Materials and Devices Southern University of Science and Technology Shenzhen 518055 China

Symmetry formulated by group theory plays an essential role with respect to the laws of nature, from fundamental particles to condensed-matter systems. Here, by combining symmetry analysis and model calculations, we elucidate that the crystallographic symmetry groups of a vast number of magnetic materials with light elements, in which the neglect of relativistic spin-orbit coupling (SOC) is an appropriate approximation, are considerably larger than the conventional magnetic groups. Thus, a symmetry description that involves partially decoupled spin and spatial rotations, dubbed spin group, is required. We derive the classifications of spin point groups describing coplanar and collinear magnetic structures, and the irreducible corepresentations of spin space groups illustrating more energy degeneracies that are disallowed by magnetic groups. One consequence of the spin group is the new antiunitary symmetries that protect SOC-free Z2 topological phases with unprecedented surface-node structures. Our work not only manifests the physical reality of materials with weak SOC, but also sheds light on the understanding of all solids with and without SOC by a unified group theory.

关键词： Topological phases of matter Topological materials Density functional calculations Group theory

Mechanical strength enhancement of C/SiC–Nb brazed joints through ultrafast high-temperature non-equilibrium surface high-entropy metallization

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Carbon 2025年 242卷

作者： Li, Peixin Wang, Zeyu Chen, Yicheng Butt, Hassaan Ahmad Zhang, Zilong Huang, Ziyao Zhang, Tianlei Qiao, Liang Zhong, Ying Krasnikov, Dmitry Nasibulin, Albert Cao, Jian Yan, Yaotian Qi, Junlei State Key Laboratory of Precision Welding & Joining of Materials and Structures Harbin Institute of Technology Harbin150001 China School of Material Science and Engineering Jiangsu University Zhenjiang212013 China Shenzhen518055 China Skolkovo Institute of Science and Technology Nobel Street 3 Moscow Russia Beijing Institute of Remote Sensing Equipment Beijing100854 China Key Laboratory of Materials Design and Quantum Simulation College of Science Changchun University Changchun130022 China

To address the challenges of high residual stress and limited high-temperature performance in C/SiC composites brazed with Nb joints using AgCuTi filler alloy, we propose a novel method of high-entropy surface metallization within an ultrafast, high-temperature, non-equilibrium temperature field (UHNF). This approach utilizes rapid heating and quenching induced by the Joule effect to produce a superior quality high-entropy metallized layer (HEML) on the C/SiC surface. Experimental results demonstrate that the brazed joints, including a 170 μm HEML, exhibit improved mechanical properties at both room temperature and 500 °C, overcoming key challenges associated with traditional joining methods. The method effectively mitigates residual stress, enhances resistance to plastic deformation, and improves the high-temperature performance of the AgCuTi filler alloy. By reducing the formation of brittle reaction layers and improving stress dissipation, this technique significantly boosts the mechanical robustness and thermal stability of brazed joints. The use of high-entropy alloys (HEAs) stabilizes the interface and extends the operational temperature range of the AgCuTi alloy. This innovative approach offers a promising strategy for overcoming the performance limitations of aerospace materials, particularly in applications involving large, performance dependent C/SiC–Nb joints. © 2025 Elsevier Ltd

关键词： Silicon carbide

Correction: materials laboratories of the future for alloys, amorphous, and composite materials (MRS Bulletin, (2025), 50, 2, (190-207), 10.1557/s43577-024-00846-y)

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MRS Bulletin 2025年 1-2页

作者： Banerjee, Sarbajit Meng, Y. Shirley Minor, Andrew M. Zhang, Minghao Zaluzec, Nestor J. Chan, Maria K.Y. Seidler, Gerald McComb, David W. Agar, Joshua Mukherjee, Partha P. Melot, Brent Chapman, Karena Guiton, Beth S. Klie, Robert F. McCue, Ian D. Voyles, Paul M. Robertson, Ian Li, Ling Chi, Miaofang Destino, Joel F. Devaraj, Arun Marquis, Emmanuelle A. Segre, Carlo U. Liu, Huinan H. Yang, Judith C. Momeni, Kasra Misra, Amit Abdolrahim, Niaz Medvedeva, Julia E. Cai, Wenjun Sehirlioglu, Alp Dizbay-Onat, Melike Mehta, Apurva Graham-Brady, Lori Maruyama, Benji Rajan, Krishna Warner, Jamie H. Taheri, Mitra L. Kalinin, Sergei V. Reeja-Jayan, B. Schwarz, Udo D. Simon, Sindee L. Brown, Craig M. Department of Chemistry and Department of Materials Science & Engineering Texas A & M University College Station United States Pritzker School of Molecular Engineering The University of Chicago Chicago United States Department of Materials Science & Engineering University of California Berkeley Berkeley United States National Center for Electron Microscopy Molecular Foundry Lawrence Berkeley National Laboratory Berkeley United States Center for Nanoscale Materials Argonne National Laboratory Lemont United States Department of Physics University of Washington Seattle United States Department of Materials Science & Engineering The Ohio State University Columbus United States Department of Mechanical Engineering and Mechanics Drexel University Philadelphia United States School of Mechanical Engineering Purdue University West Lafayette United States Department of Chemistry University of Southern California Los Angeles United States Department of Chemistry Stony Brook University The State University of New York Stony Brook United States Department of Chemistry University of Kentucky Lexington United States Department of Physics University of Illinois at Chicago Chicago United States Department of Materials Science & Engineering Northwestern University Evanston Bangladesh Department of Materials Science & Engineering University of Wisconsin–Madison Madison United States Department of Materials Science and Engineering University of Pennsylvania Philadelphia United States Department of Mechanical Engineering and Materials Science Duke University Durham United States Department of Chemistry Creighton University Omaha United States Physical and Computational Sciences Directorate Pacific Northwest National Laboratory Richland United States Department of Materials Science & Engineering University of Michigan–Ann Arbor Ann Arbor United States Department of Physics Illinois Institute of Technology Chicago United States Department of Bioengineering and the Mater

This article was updated to correct Minghao Zhang’s affiliation from "Pritzker School of Molecular engineering, The University of Chicago, Chicago, USA" to "Pritzker School of Molecular engineering, The University of Chicago, Chicago, USA;Argonne National laboratory, Lemont, USA." Argonne National laboratory was left off the original publication. © The Author(s) 2025.

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Band alignment in multilayered semiconductor homojunctions supported on metals

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Journal of materials Chemistry C 2020年第3期8卷 959-967页

作者： Wang, Qian Dou, Kunpeng Shi, Xingqiang Department of Physics Guangdong Provincial Key Laboratory for Computational Science and Material Design Southern University of Science and Technology Shenzhen518055 China Harbin Institute of Technology Harbin150080 China College of Information Science and Engineering Ocean University of China Qingdao266100 China

To solve the intractable problem of momentum-mismatch in heterojunctions, we propose a universal approach to obtain type II band alignment in two-dimensional (2D) semiconductor homojunctions with wide range momentum-space-match by a band-nesting effect. 2D homojunctions are implemented in van der Waals multilayered semiconductors through supporting them on a metal surface. There are two advantages in 2D multilayered semiconductor homojunctions (MSHs) compared to 2D heterojunctions: (1) momentum-matched band alignments are easy to achieve due to the inherent lattice-orientation-match between van der Waals layers of the same 2D material, and moreover, a wide-range momentum-space-match can be obtained by metal-induced Fermi-level movement to achieve 'parallel' band edges in degenerately doped MSHs;and (2) largely tunable band offsets make band alignment change from type II to type III to inversed type II due to the charge redistribution at the junction interfaces. In addition, we found that 2D MSHs are better supported on 2D metals (e.g. MXene) rather than 3D metals (e.g. Pt), with the advantages of being free of metal-induced-gap-states and easily obtained n- and p-type Schottky-barrier-free contacts. Thus, our proposed van der Waals homojunctions, with unexpected excellent properties compared to heterojunctions, stimulate studies on their various applications. © 2020 The Royal Society of Chemistry.

关键词： Metals

Compositional Variations in Highly Active Ptsn/Al2o3 Catalysts Derived from Molecular Complexes

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SSRN

SSRN 2023年

作者： He, Qian Xu, Chaokai Tan, Shengdong Tang, Yaxin Xi, Shibo Yao, Bingqing Wade, Austin Zhao, Binbin Lu, Shangchen Tian, Mingjiao He, Chi Ma, Lu Fu, Xingjie Shi, Jiwei Lu, Jiong Howe, Alexander G.R. Dai, Sheng Luo, Guangfu Du, Yankun Department of Material Science and Engineering College of Design and Engineering National University of Singapore 9 Engineering Drive 1 EA #03-09 Singapore117575 Singapore Department of Materials Science and Engineering Guangdong Provincial Key Laboratory of Computational Science and Material Design Southern University of Science and Technology Guangdong Shenzhen518055 China 1 Pesek Road Jurong Island 627833 Singapore Thermo Fisher Scientific 5350 NW Dawson Creek Drive HillsboroOR United States State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi’an Jiaotong University Shaanxi Xi’an710049 China Brookhaven National Laboratory UptonNY11973 United States Department of Chemistry National University of Singapore 12 Science Drive 2 117549 Singapore Key Laboratory for Advanced Materials Joint International Research Laboratory of Precision Chemistry and Molecular Engineering School of Chemistry and Molecular Engineering East China University of Science & Technology Shanghai200237 China

We investigated the industrially important PtSn/Al2O3 catalysts prepared with uniform particle sizes (~ 1 nm) and varied compositions using molecular complexes of Pt(II) and Sn(II). Our best catalyst, with a Sn:Pt ratio of around 2, exhibited a high initial propylene productivity of about 1.1 mol C3H6 (g catalyst)-1 h-1. Elaborate electron microscopy studies revealed significant compositional variations in the catalyst, highlighting the practical challenges in achieving or confirming the theoretically predicted optimum Sn:Pt ratio. It is also found that the catalytic activities correlate well with the Pt dispersion, suggesting the structure-insensitive nature of the dehydrogenation reaction applies in these ultrasmall Pt-Sn nanoparticles. The presence of Pt-rich particles in the catalysts did not produce noticeable degradations in the reaction selectivity, indicating a wide composition range for Pt-Sn nanoparticles to be effective at the 1 nm size range. These findings emphasize the importance of detailed analysis of compositional distributions for understanding nanoalloys. © 2023, The Authors. All rights reserved.

关键词： Electron microscopy

designing Ultra-Flat Bands in Twisted Bilayer materials at Large Twist Angles without specific degree

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arXiv 2022年

作者： Tao, Shengdan Zhang, Xuanlin Zhu, Jiaojiao He, Pimo Yang, Shengyuan A. Lu, Yunhao Wei, Su-Huai Zhejiang Province Key Laboratory of Quantum Technology and Device Department of Physics Zhejiang University Hangzhou310027 China State Key Laboratory of Silicon Materials School of Materials Science and Engineering Zhejiang University Hangzhou310027 China Research Laboratory for Quantum Materials Singapore University of Technology and Design Singapore487372 Singapore Beijing Computational Science Research Center Beijing100193 China

Inter-twisted bilayers of two-dimensional (2D) materials can host low-energy flat bands, which offer opportunity to investigate many intriguing physics associated with strong electron correlations. In the existing systems, ultra-flat bands only emerge at very small twist angles less than a few degrees, which poses challenge for experimental study and practical applications. Here, we propose a new design principle to achieve low-energy ultra-flat bands with increased twist angles. The key condition is to have a 2D semiconducting material with large energy difference of band edges controlled by stacking. We show that the interlayer interaction leads to defect-like states under twisting, which forms a flat band in the semiconducting band gap with dispersion strongly suppressed by the large energy barriers in the moiré superlattice even for large twist angles. We explicitly demonstrate our idea in bilayer α-In2Se3 and bilayer InSe. For bilayer α-In2Se3, we show that a twist angle ~13.2◦ is sufficient to achieve the band flatness comparable to that of twist bilayer graphene at the magic angle ~1.1◦. In addition, the appearance of ultra-flat bands here is not sensitive to the twist angle as in bilayer graphene, and it can be further controlled by external gate fields. Our finding provides a new route to achieve ultra-flat bands other than reducing the twist angles and paves the way towards engineering such flat bands in a large family of 2D materials. © 2022, CC BY.

关键词： Energy gap