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Multifunctional silicene/CeO_(2)heterojunctions:Desirable electronic material and promising water-splitting photocatalyst

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Chinese Chemical Letters 2022年第8期33卷 3947-3950页

作者： Liang Xu Jian Zeng Quan Li Xin Luo Tong Chen Jingjing Liu Ling-Ling Wang Energy Materials Computing Center School of Energy and Mechanical EngineeringJiangxi University of Science and TechnologyNanchang 330013China Department of Applied Physics School of ScienceEast China Jiaotong UniversityNanchang 330013China Key Laboratory for Micro-Nano Optoelectronic Devices of Ministry of Education School of Physics and ElectronicsHunan UniversityChangsha 410082China

The first-principles calculations demonstrate that covalently bonded(cb)heterojunction and van der Waals(vd W)heterojunction can coexist in silicene/CeO_(2) heterojunctions,due to the different stacking patterns.Especially,the cb heterojunction with band gap of 1.97 e V,forms a type-II heterojunction,exhibits good redox performance and has high-effective optical absorption spectra,thus it is a promising photocatalyst for overall water splitting.Besides,for the vd W heterojunction,the Dirac cone of silicene is well kept on CeO_(2) semiconducting substrate,with a considerable energy gap of 0.43 e V,which can be an ideal material in building silicene-based electronic device.These results may open a new gateway in both of nanoelectronic device and energy conversion for silicene/Ce O2 nanocomposites.

关键词： silicene CeO_(2) Photocatalyst Interfacial interaction Dirac cone

Sisyphus effects in hydrogen electrochemistry on metal silicides enabled by silicene subunit edge

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Science Bulletin 2019年第9期64卷 617-624页

作者： Zechao Zhuang Yong Li Jiazhao Huang Zilan Li Kangning Zhao Yunlong Zhao Lin Xu Liang Zhou Lyudmila V. Moskaleva Liqiang Mai State Key Laboratory of Advanced Technology for Materials Synthesis and Processing International School of Materials Science and EngineeringWuhan University of Technology Institute of Applied and Physical Chemistry and Center for Environmental Research and Sustainable Technology University of Bremen Advanced Technology Institute University of Surrey Department of Chemistry University of the Free State

Nonmetal elements strictly govern the electrochemical performance of molybdenum compounds.Yet,the exact role played by nonmetals during electrocatalysis remains largely obscure.With intermetallic MoSi_2comprising silicene subunits,we present an unprecedented hydrogen evolution reaction(HER)behavior in aqueous alkaline solution.Under continuous operation,the HER activity of MoSi_2shows a more than one order of magnitude improvement in current density from 1.1 to 21.5 mA cm^(à2)at 0.4 V overpotential.Meanwhile,this activation behavior is highly reversible,such that voltage withdrawal leads to catalyst inactivation but another operation causes reactivation.Thus,the system shows dynamics strikingly analogous to the legendary Sisyphus’labor,which drops and recovers in a stepwise manner repeatedly,but never succeeds in reaching the top of the mountain.Isomorphic WSi_2behaves almost the same as MoSi_2,whereas other metal silicides with silicyne subunits,including CrSi_2and TaSi_2,do not exhibit any anomalous behavior.A thin amorphous shell of MoSi_2is observed after reaction,within which the Si remains partially oxidized while the oxidation state of Mo is basically unchanged.First-principles calculations further reveal that the adsorption of hydroxide ions on silicene subunit edges and the subsequent Si vacancy formation in MoSi_2jointly lead to the anomalous HER kinetics of the adjacent Mo active centers.This work demonstrates that the role of nonmetal varies dramatically with the electronic and crystallographic structures of silicides and that silicene structural subunit may serve as a promoter for boosting HER in alkaline media.

关键词： Sisyphus effect Electrochemistry Metal silicides silicene subunit Hydrogen evolution reaction

Tunable valley filter efficiency by spin-orbit coupling in silicene nanoconstrictions

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Chinese Physics B 2021年第5期30卷 589-594页

作者：施一剑王园春汪鹏君 College of Electrical and Electronic Engineering Wenzhou UniversityWenzhou 325035China

Valley filter is a promising device for producing valley polarized current in graphene-like two-dimensional honeycomb lattice materials.The relatively large spin-orbit coupling in silicene contributes to remarkable quantum spin Hall effect,which leads to distinctive valley-dependent transport properties compared with intrinsic graphene.In this paper,quantized conductance and valley polarization in silicene nanoconstrictions are theoretically investigated in quantum spin-Hall insulator phase.Nearly perfect valley filter effect is found by aligning the gate voltage in the central constriction region.However,the valley polarization plateaus are shifted with the increase of spin-orbit coupling strength,accompanied by smooth variation of polarization reversal.Our findings provide new strategies to control the valley polarization in valleytronic devices.

关键词： valley polarization spin-orbit coupling quantization silicene

Electronic properties of silicene in BN/silicene van der Waals heterostructures

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Chinese Physics B 2018年第7期27卷 473-479页

作者：吴泽宾张余洋李更杜世萱高鸿钧 Key Laboratory of Vacuum Physics Institute of Physics Chinese Academy of Sciences Beijing 100190 China University of Chinese Academy of Sciences Beijing 100190 China

silicene is a promising 2D Dirac material as a building block for van der Waals heterostructures （vdWHs）. Here we investigate the electronic properties of hexagonal boron nitride/silicene （BN/Si） vdWHs using first-principles calculations. We calculate the energy band structures of BN/Si/BN heterostructures with different rotation angles and find that the electronic properties of silicene are retained and protected robustly by the BN layers. In BN/Si/BN/Si/BN heterostructure, we find that the band structure near the Fermi energy is sensitive to the stacking configurations of the silicene layers due to in- terlayer coupling. The coupling is reduced by increasing the number of BN layers between the silicene layers and becomes negligible in BN/Si/（BN）3/Si/BN. In （BN）n/Si superlattices, the band structure undergoes a conversion from Dirac lines to Dirac points by increasing the number of BN layers between the silicene layers. Calculations of silicene sandwiched by other 2D materials reveal that silicene sandwiched by low-carbon-doped boron nitride or HfO2 is semiconducting.

关键词： silicene BN electronic property heterostructure

The nonlocal transport and switch effect in light-and electric-controlled silicene–superconductor hybrid structure

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Chinese Physics B 2018年第12期27卷 121-126页

作者：戚凤华曹军曹杰张力发 Center for Quantum Transport and Thermal Energy Science School of Physics and TechnologyNanjing Normal UniversityNanjing 210023China School of Electronic Engineering Nanjing Xiaozhuang UniversityNanjing 211171China College of Science Hohai UniversityNanjing 210098China

We theoretically investigate the influence of off-resonant circularly polarized light field and perpendicular electric field on the quantum transport in a monolayer silicene-based normal/superconducting/normal junction.Owing to the tunable band structure of silicene,a pure crossed Andreev reflection process can be realized under the optical and electrical coaction.Moreover,a switch effect among the exclusive crossed Andreev reflection,the exclusive elastic cotunneling and the exclusive Andreev reflection,where the former two are the nonlocal transports and the third one is the local transport,can be obtained in our system by the modulation of the electric and light fields.In addition,the influence of the relevant parameters on the nonlocal and local transports is calculated and analyzed as well.

关键词： switch effect silicene crossed Andreev reflection

Spin-valley-dependent transport and giant tunneling magnetoresistance in silicene with periodic electromagnetic modulations

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Chinese Physics B 2017年第12期26卷 475-480页

作者：刘一曼邵怀华周光辉朴红光潘礼庆刘敏 College of Science China Three Gorges University School of Electrical Engineering Liupanshui Normal University Department of Physics and Key Laboratory for Low-Dimensional Structures and Quantum Manipulation (Ministry of Education) Hunan Normal University

The transport property of electrons tunneling through arrays of magnetic and electric barriers is studied in silicene. In the tunneling transmission spectrum, the spin-valley-dependent filtered states can be achieved in an incident energy range which can be controlled by the electric gate voltage. For the parallel magnetization configuration, the transmission is asymmetric with respect to the incident angle θ, and electrons with a very large negative incident angle can always transmit in propagating modes for one of the spin-valley filtered states under a certain electromagnetic condition. But for the antiparallel configuration, the transmission is symmetric about θ and there is no such transmission channel. The difference of the transmission between the two configurations leads to a giant tunneling magnetoresistance （TMR） effect. The TMR can reach to 100% in a certain Fermi energy interval around the electrostatic potential. This energy interval can be adjusted significantly by the magnetic field and/or electric gate voltage. The results obtained may be useful for future valleytronic and spintronic applications, as well as magnetoresistance device based on silicene.

关键词： silicene quantum transport electromagnetic superlattice giant tunneling magnetoresistance effect

Improved double-gate armchair silicene nanoribbon field-effect-transistor at large transport bandgap

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Chinese Physics B 2016年第1期25卷 809-816页

作者： Mohsen Mahmoudi Zahra Ahangari Morteza Fathipour Department of Electrical and Computer Engineering University of Tehran Young Researchers and Elite Club Yadegar-e-Imam Khomeini (RAH) Shahre-Rey Branch Islamic Azad University

The electrical characteristics of a double-gate armchair silicene nanoribbon field-effect-transistor （DG ASiNR FET） are thoroughly investigated by using a ballistic quantum transport model based on non-equilibrium Green＇s function （NEGF） approach self-consistently coupled with a three-dimensional （3D） Poisson equation. We evaluate the influence of variation in uniaxial tensile strain, ribbon temperature and oxide thickness on the on-off current ratio, subthreshold swing, transconductance and the delay time of a 12-nm-length ultranarrow ASiNR FET. A novel two-parameter strain mag- nitude and temperature-dependent model is presented for designing an optimized device possessing balanced amelioration of all the electrical parameters. We demonstrate that employing HfO2 as the gate insulator can be a favorable choice and simultaneous use of it with proper combination of temperature and strain magnitude can achieve better device performance. Furthermore, a general model power （GMP） is derived which explicitly provides the electron effective mass as a function of the bandgap of a hydrogen passivated ASiNR under strain.

关键词： silicene double-gate field-effect-transistor non-equilibrium Green＇s function tight binding

Competing magnetic states in silicene and germanene 2D ferromagnets

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Nano Research 2020年第12期13卷 3396-3402页

作者： Dmitry V.Averyanov Ivan S.Sokolov Mikhail S.Platunov Fabrice Wilhelm Andrei Rogalev Pierluigi Gargiani Manuel Valvidares Nicolas Jaouen Oleg E.Parfenov Alexander N.Taldenkov Igor A.Karateev Andrey M.Tokmachev Vyacheslav G.Storchak National Research Center“Kurchatov Institute” Kurchatov Sq.1Moscow123182Russia ESRF-The European Synchrotron CS 4022038043Grenoble Cedex 9France ALBA Synchrotron Light Source Cerdanyola del Vallès08290BarcelonaSpain L’Orme des Merisiers Synchrotron SOLEILGyf-sur-Yvette91192France

Two-dimension(2D)magnets have recently developed into a class of stoichiometric materials with prospective applications in ultra-compact spintronics and quantum computing.Their functionality is particularly rich when different magnetic orders are competing in the same material.Metalloxenes REX2(RE=Eu,Gd;X=Si,Ge),silicene or germanene—heavy counterparts of graphene—coupled with a layer of rare-earth metals,evolve from three-dimension(3D)antiferromagnets in multilayer structures to 2D ferromagnets in a few monolayers.This evolution,however,does not lead to fully saturated 2D ferromagnetism,pointing at a possibility of coexisting/competing magnetic states.Here,REX2 magnetism is explored with element-selective X-ray magnetic circular dichroism(XMCD).The measurements are carried out for GdSi2,EuSi2,GdGe2,and EuGe2 of different thicknesses down to 1 monolayer employing K absorption edges of Si and Ge as well as M and L edges of the rare-earths.They access the magnetic state in REX2 and determine the seat of magnetism,orbital,and spin contributions to the magnetic moment.High-field measurements probe remnants of the bulk antiferromagnetism in 2D REX2.The results provide a new platform for studies of complex magnetic structures in 2D materials.

关键词： silicene germanene 2D ferromagnetism X-ray magnetic circular dichroism(XMCD) monolayer

Goos-Hanchen-like shift related to spin and valley polarization in ferromagnetic silicene

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Chinese Physics B 2021年第10期30卷 523-529页

作者：刘美荣刘正方张若龙肖贤波伍清萍 Department of Applied Physics East China Jiaotong UniversityNanchang 330013China School of Computer Science Jiangxi University of Traditional Chinese MedicineNanchang 330004China

We study the Goos-Hanchen-like shift of single silicene barrier under the external perpendicular electric field,off- resonant circularly polarized light and the exchange field modulation using the stationary-phase method.The results show that the Goos-Hanchen-like shift of silicene resulting from the external perpendicular electric field does not have the characteristics of spin or valley polarization,while that from off-resonant circularly polarized light or the exchange field is spin-polarized.More importantly,the combined effect of the external perpendicular electric field and the exchange field or off-resonant circularly polarized light can cause the Goos-Hanchen-like shift of the system to be spin and valley polarized.It is particularly worth noting that when the three modulations are considered at the same time,as the exchange field changes,the system will have a positive or negative Goos-Hanchen-like shift.

关键词： Goos-Hanchen-like shift silicene polarization