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Realizing quinary charge states of solitary defects in two-dimensional intermetallic semiconductor

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National Science Review 2022年第2期9卷 63-69页

作者： Jian Gou Bingyu Xia Xuguang Wang Peng Cheng andrew thye shen wee Wenhui Duan Yong Xu Kehui Wu Lan Chen Institute of Physics Chinese Academy of Sciences School of Physics University of Chinese Academy of Sciences Department of Physics National University of Singapore State Key Laboratory of Low-Dimensional Quantum Physics Department of Physics Tsinghua University Institute for Advanced Study Tsinghua University Collaborative Innovation Center of Quantum Matter RIKEN Center for Emergent Matter Science (CEMS) Songshan Lake Materials Laboratory

Creating and manipulating multiple charge states of solitary defects in semiconductors is of essential importance for solitary defect electronics,but is fundamentally limited by Coulomb’s *** this objective is challenging,due to the conflicting requirements of the localization necessary for the sizable band gap and delocalization necessary for a low charging ***,using scanning tunneling microscopy/spectroscopy experiments and first-principles calculations,we realized exotic quinary charge states of solitary defects in two-dimensional intermetallic semiconductor *** also observed an ultralow defect charging energy that increases sublinearly with charge number rather than displaying the usual quadratic *** work suggests a promising route for constructing multiple defect-charge states by designing intermetallic semiconductors,and opens new opportunities for developing quantum devices with charge-based quantum states.

关键词： 2D materials intermetallic semiconductor tip-induced band bending solitary defect defect charging

Atomic-scale characterization of two-dimensional magnets and their heterostructures

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ChemPhysMater 2023年第4期2卷 282-294页

作者： Yuli Huang Mingyue Sun Yihe Wang andrew thye shen wee Wei Chen Joint School of National University of Singapore and Tianjin University International Joint Institute of Tianjin UniversityFuzhou 350207China Department of Physics National University of SingaporeSingapore 117551Singapore Department of Chemistry National University of SingaporeSingapore 117542Singapore

The realization of long-range magnetic ordering in two-dimensional(2D)van der Waals systems significantly expands the scope of the 2D family as well as their possible spin-related phenomena and device *** atomically thin nature of 2D materials makes their magnetically ordered states sensitive to local environments,and this necessitates advanced characterization at the atomic ***,we briefly review several representative 2D magnetic systems,namely,iron chalcogenides,chromium chalcogenides,chromium trihalides,and their *** powerful scanning-probe microscopy,atomically resolved characterization of their crystalline configurations,electronic structures,and magnetization distributions has been achieved,and novel phenomena such as giant tunneling magnetoresistance and topological superconductivity have been ***,we discuss the challenges and new perspectives in this flourishing field.

关键词： Two-dimensional magnets Two-dimensional heterostructures Scanning probe microscopy Spin-polarized configuration

6H-SiC(0001)-63^(1/3)×63^(1/3)R30°重构表面的同步辐射角分辨光电子能谱研究

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物理学报 2009年第6期58卷 4288-4294页

作者：武煜宇陈石高新宇 andrew thye shen wee 徐彭寿中国科学技术大学国家同步辐射实验室合肥230029 新加坡国立大学物理系新加坡117542

利用同步辐射角分辨光电子能谱(SRARPES)对6H-SiC(0001)-63^(1/3)×63^(1/3)R30°重构表面的电子结构和表面态进行了研究.通过鉴别价带谱中来自于体态的信息,可以推断出重构表面的费米能级位于体态价带顶之上(2.1±0.1)eV处.实验测出的... 详细信息

利用同步辐射角分辨光电子能谱(SRARPES)对6H-SiC(0001)-63^(1/3)×63^(1/3)R30°重构表面的电子结构和表面态进行了研究.通过鉴别价带谱中来自于体态的信息,可以推断出重构表面的费米能级位于体态价带顶之上(2.1±0.1)eV处.实验测出的体能带结构与理论计算的结果较为符合.在重构表面上发现三个表面态,分别位于结合能-0.48eV(S0),-1.62eV(S1)和-4.93eV(S2)处.沿着表面布里渊区的高对称线ΓKM方向,测量了相关表面态的能带色散,只有表面态S0(-0.48eV)表现出了所希望的63×63R30°重构周期性.根据实验现象,可以认为,表面态S0应归结于重构表面的C—C悬键,而表面态S1则由重构表面未钝化的C悬键所导致.

关键词：角分辨光电子能谱碳化硅(SiC) 电子结构表面态

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Structuring Nonlinear Wavefront Emitted from Monolayer Transition-Metal Dichalcogenides

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Research 2020年第1期2020卷 1721-1730页

作者： Xuanmiao Hong Guangwei Hu Wenchao Zhao Kai Wang Shang Sun Rui Zhu Jing Wu Weiwei Liu Kian Ping Loh andrew thye shen wee Bing Wang Andrea Alù Cheng-Wei Qiu Peixiang Lu Wuhan National Laboratory for Optoelectronics and School of Physics Huazhong University of Science and TechnologyWuhan 430074China Department of Electrical and Computer Engineering National University of Singapore4 Engineering Drive 3Singapore 117583 Advanced Science Research Center City University of New YorkNew York 10031USA Department of Physics National University of Singapore2 Science Drive 3Singapore 117542 Institute of Materials Research and Engineering Agency for ScienceTechnology and Research2 Fusionopolis WayInnovis#08-03Singapore 138634 Department of Chemistry National University of Singapore3 Science Drive 3Singapore 17543 Centre for Advanced 2D Materials National University of SingaporeBlock S146 Science Drive 2Singapore 117546 Hubei Key Laboratory of Optical Information and Pattern Recognition Wuhan Institute of TechnologyWuhan 430205China

The growing demand for tailored nonlinearity calls for a structure with unusual phase discontinuity that allows the realization of nonlinear optical chirality,holographic imaging,and nonlinear wavefront ***-metal dichalcogenide(TMDC)monolayers offer giant optical nonlinearity within a few-angstrom thickness,but limitations in optical absorption and domain size impose restriction on wavefront control of nonlinear emissions using classical light *** contrast,noble metal-based plasmonic nanosieves support giant field enhancements and precise nonlinear phase control,with hundred-nanometer pixellevel resolution;however,they suffer from intrinsically weak nonlinear ***,we report a multifunctional nonlinear interface by integrating TMDC monolayers with plasmonic nanosieves,yielding drastically different nonlinear functionalities that cannot be accessed by either *** a hybrid nonlinear interface allows second-harmonic(SH)orbital angular momentum(OAM)generation,beam steering,versatile polarization control,and holograms,with an effective SH nonlinearityχ^((2))of~25 nm/*** designer platform synergizes the TMDC monolayer and plasmonic nanosieves to empower tunable geometric phases and large field enhancement,paving the way toward multifunctional and ultracompact nonlinear optical devices.

关键词： nonlinearity Transition yielding

Two-dimensional ferromagnetic superlattices

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National Science Review 2020年第4期7卷 745-754页

作者： Shanshan Liu Ke Yang Wenqing Liu Enze Zhang Zihan Li Xiaoqian Zhang Zhiming Liao Wen Zhang Jiabao Sun Yunkun Yang Han Gao Ce Huang Linfeng Ai Ping Kwan Johnny Wong andrew thye shen wee Alpha T.N'Diaye Simon A.Morton Xufeng Kou Jin Zou Yongbing Xu Hua Wu Faxian Xiu State Key Laboratory of Surface Physics and Department of Physics Fudan University Institute for Nanoelectronic Devices and Quantum Computing Fudan University Laboratory for Computational Physical Sciences (MOE) Fudan University Department of Electronic Engineering Royal Holloway University of London School of Electronic Science and Engineering Nanjing University Materials Engineering The University of Queensland Department of Physics National University of Singapore Centre for Advanced 2D Materials and Graphene Research Centre National University of Singapore Lawrence Berkeley National Laboratory School of Information Science and Technology Shanghai Tech University Centre for Microscopy and Microanalysis The University of Queensland Collaborative Innovation Center of Advanced Microstructures

Mechanically exfoliated two-dimensional ferromagnetic materials(2 D FMs) possess long-range ferromagnetic order and topologically nontrivial skyrmions in few layers. However, because of the dimensionality effect, such few-layer systems usually exhibit much lower Curie temperature(TC) compared to their bulk counterparts. It is therefore of great interest to explore effective approaches to enhance their TC, particularly in wafer-scale for practical applications. Here, we report an interfacial proximity-induced high-TC2 D FM FeGe Te(FGT) via A-type antiferromagnetic material Cr Sb(CS) which strongly couples to FGT. A superlattice structure of(FGT/CS)n, where n stands for the period of FGT/CS heterostructure, has been successfully produced with sharp interfaces by molecular-beam epitaxy on 2-inch wafers. By performing elemental specific X-ray magnetic circular dichroism(XMCD) measurements, we have unequivocally discovered that TCof 4-layer FeGeTecan be significantly enhanced from 140 K to230 K because of the interfacial ferromagnetic coupling. Meanwhile, an inverse proximity effect occurs in the FGT/CS interface, driving the interfacial antiferromagnetic Cr Sb into a ferrimagnetic state as evidenced by double-switching behavior in hysteresis loops and the XMCD spectra. Density functional theory calculations show that the Fe-Te/Cr-Sb interface is strongly FM coupled and doping of the spin-polarized electrons by the interfacial Cr layer gives rise to the TCenhancement of the FeGeTefilms, in accordance with our XMCD measurements. Strikingly, by introducing rich Fe in a 4-layer FGT/CS superlattice, TCcan be further enhanced to near room temperature. Our results provide a feasible approach for enhancing the magnetic order of few-layer 2 D FMs in wafer-scale and render opportunities for realizing realistic ultra-thin spintronic devices.

关键词： 2D ferromagnetic material room temperature 2-inch Fe3GeTe2 film wafers proximity effect (Fe3GeTe2/CrSb)nsuperlattice

Towards higher-dimensional structured light

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Light(Science & Applications) 2022年第8期11卷 1650-1666页

作者： Chao He Yijie shen andrew Forbes Department of Engineering Science University of OxfordParks RoadOxfordOX13PJUK Optoelectronics Research Centre University of SouthamptonSouthamptonSO171BJUK School of Physics University of the WitwatersrandPrivate Bag 3Johannesburg2050South Africa

Structured light refers to the arbitrarily tailoring of optical fields in all their degrees of freedom(DoFs),from spatial to *** orbital angular momentum(OAM)is perhaps the most topical example,and celebrating 30 years since its connection to the spatial structure of light,control over other DoFs is slowly gaining traction,promising access to higher-dimensional forms of structured ***,harnessing these new DoFs in quantum and classical states remains challenging,with the toolkit still in its *** this perspective,we discuss methods,challenges,and opportunities for the creation,detection,and control of multiple DoFs for higher-dimensional structured *** present a roadmap for future development trends,from fundamental research to applications,concentrating on the potential for larger-capacity,higher-security information processing and communication,and beyond.

关键词： light dimensional slowly

Metal Organic framework derived carbon for ultrahigh power and long cyclic life aqueous Zn ion capacitor

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Nano Materials Science 2020年第2期2卷 159-163页

作者： Ting Xiong Yirui shen wee Siang Vincent Lee Junmin Xue Department of Materials Science and Engineering National University of SingaporeSingapore117573 Centre for Advanced 2D Materials and Graphene Research Centre National University of SingaporeSingapore117546 Key Laboratory of Synthetic and Biological Colloids(Jiangnan University) Ministry of EducationSchool of Chemical and Material EngineeringWuxi214122PR China

In order to develop functional energy storage device,it is necessary to improve the energy and power *** a potential candidate that can synergistically harmonize energy and power density,lithium ion capacitor(LIC)has shown exciting promises in recent ***,in the recent years,alternative metal has been explored to replace lithium in such metal-ion capacitor ***,in this work we present zinc ion capacitor(ZIC)in which zinc acts as negative electrode and Metal Organic framework(MOF)derived carbon as positive *** assembled ZIC was able to demonstrate exceptional power density of 85.5 kW kg^-1 and a maximal energy density of 36.4W h kg^-1,together with 99%capacitance retention after cycling for 20000 cycles.

关键词： density. lithium replace

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Two-dimensional magnetic transition metal chalcogenides

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SmartMat 2021年第2期2卷 139-153页

作者： Yu Li Huang Wei Chen andrew T.S.wee Joint School of National University of Singapore and Tianjin University International Campus of Tianjin UniversityFuzhouChina Department of Physics National University of SingaporeSingaporeSingapore Department of Chemistry National University of SingaporeSingaporeSingapore

The field of two-dimensional(2D)magnets has expanded rapidly during the past several years since the first demonstration of intrinsic 2D magnetism in atomically thin CrI_(3) and Cr_(2)Ge_(2)Te_(6) in 2017.2D transition metal chalcogenides(TMCs),a class of strongly correlated materials,have exhibited a wide variety of novel electronic and optical properties,and more recently ***,we review recent experimental progress achieved in the growth of 2D magnetic TMC materials using chemical vapor deposition and molecular beam epitaxy *** examples include the demonstration of room temperature intrinsic and extrinsic ferromagnetism in monolayer VSe_(2),MnSe_(2),Cr_(3)Te_(4),V-doped WSe_(2),and so on.A brief discussion on the origin of the exotic magnetic properties and emergent phenomena is also ***,we summarize the remaining challenges and future perspective on the development of 2D magnetic materials for next-generation spintronic devices.

关键词： chemical vapor deposition molecular beam epitaxy transition metal chalcogenides twodimensional magnets

Active label-denoising algorithm based on broad learning for annotation of machine health status

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Science China(Technological Sciences) 2022年第9期65卷 2089-2104页

作者： LIU GuoKai shen WeiMing GAO Liang KUSIAK andrew State Key Laboratory of Digital Manufacturing Equipment and Technology Huazhong University of Science and TechnologyWuhan 430074China Department of Industrial and System Engineering The University of IowaSeamans CenterIowa CityIA 52242USA

Deep learning has led to tremendous success in machine maintenance and fault ***,this success is predicated on the correctly annotated *** in large industrial datasets can be noisy and thus degrade the performance of fault diagnosis *** emerging concept of broad learning shows the potential to address the label noise *** with existing deep learning algorithms,broad learning has a simple architecture and high training *** active label denoising algorithm based on broad learning(ALDBL)is ***,ALDBL captures the embedded representation from the time-frequency features by a recurrent memory ***,it augments wide features with a sparse autoencoder and projects the sparse features into an orthogonal space.A proposed corrector then iteratively changes the weights of source examples during the training and corrects the labels by using a label adaptation ***,ALDBL finetunes the model parameters with actively sampled target data with reliable pseudo *** performance of ALDBL is validated with three benchmark datasets,including 30 label denoising *** results demonstrate the effectiveness and advantages of the proposed algorithm over the other label denoising algorithms.

关键词： data annotation broad learning deep learning domain adaptation fault diagnosis noisy label