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Effects of in-plane stiffness and charge transfer on thermal expansion of monolayer transition metal dichalcogenide

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Chinese Physics B 2015年第2期24卷 343-349页

作者：王占雨周艳丽王雪青王飞孙强郭正晓贾瑜 International Joint Research Laboratory for Quantum Functional Materials of Henan Zhengzhou University School of Physics and Engineering Zhengzhou University Department of Mechanical and Electrical Engineering Henan Industry and Trade Vocational College Department of Chemistry University College London

The temperature dependence of lattice constants is studied by using first-principles calculations to determine the effects of in-plane stiffness and charge transfer on the thermal expansions of monolayer semiconducting transition metal dichalcogenides.Unlike the corresponding bulk material,our simulations show that monolayer MX2（M = Mo and W;X = S,Se,and Te） exhibits a negative thermal expansion at low temperatures,induced by the bending modes.The transition from contraction to expansion at higher temperatures is observed.Interestingly,the thermal expansion can be tailored regularly by alteration of the M or X atom.Detailed analysis shows that the positive thermal expansion coefficient is determined mainly by the in-plane stiffness,which can be expressed by a simple relationship.Essentially the regularity of this change can be attributed to the difference in charge transfer between the different elements.These findings should be applicable to other two-dimensional systems.

关键词： transition metal dichalcogenide thermal expansion phonon

Nonlinear photoncurrent in transition metal dichalcogenide with warping term under illuminating of light

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Chinese Physics B 2021年第3期30卷 436-440页

作者：朱国宝杨慧敏张运海 School of Physics and Electronic Engineering Heze UniversityHeze 274015China

We investigate the photoconductivities of injection current and the shift current in transition metal dichalcogenide with warping term in the presence of sublattice potential and spin orbit coupling.The system shows the valley photoconductivities of injection current and the photoconductivities of shift current.It is found that the warping term and the geometric tensor play a critical role in the system,which are responsible for the photoconductivities.Due to the interplay between the sublattice potential and the spin orbit coupling,the photoconductivities can be tuned.Furthermore,the effect of warping term on geometric tensor and the amplitude of the photoconductivities are also discussed.

关键词： photoconductivity transition metal dichalcogenide warping term

In-situ surface self-reconstruction in ternary transition metal dichalcogenide nanorod arrays enables efficient electrocatalytic oxygen evolution

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Journal of Energy Chemistry 2021年第4期30卷 10-16页

作者： Qiang Chen Yulu Fu Jialun Jin Wenjie Zang Xiong Liu Xiangyong Zhang Wenzhong Huang Zongkui Kou John Wang Liang Zhou Liqiang Mai State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of TechnologyWuhan 430070HubeiChina Department of Materials Science and Engineering National University of SingaporeSingapore 117574Singapore Foshan Xianhu Laboratory Foshan 528216GuangdongChina

Water splitting has received more and more attention because of its huge potential to generate clean and renewable energy.The highly active and durable oxygen evolution reaction(OER)catalysts play a decisive factor in achieving efficient water splitting.The identification of authentic active origin under the service conditions can prompt a more reasonable design of catalysts together with well-confined micro-/nano-structures to boost the efficiency of water splitting.Herein,Fe,Co,and Ni ternary transition metal dichalcogenide(FCND)nanorod arrays on Ni foam are purposely designed as an active and stable low-cost OER pre-catalyst for the electrolysis of water in alkaline media.The optimized FCND catalyst demonstrated a lower overpotential than the binary and unary counterparts,and a 27-fold rise in kinetic current density at the overpotential of 300 m V compared to the nickel dichalcogenide counterpart.Raman spectra and other structural characterizations at different potentials reveal that the in-situ surface self-reconstruction from FCND to ternary transition metal oxyhydroxides(FCNOH)on catalyst surfaces initiated at about 1.5 V,which is identified as the origin of OER activity.The surface selfreconstruction towards FCNOH also enables excellent stability,without fading upon the test for 50 h.

关键词： Surface self-reconstruction transition metal dichalcogenide transition metal oxyhydroxide Oxygen evolution reaction Water splitting

Thermal properties of transition-metal dichalcogenide

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Chinese Physics B 2018年第3期27卷 12-19页

作者：刘向军张永伟 Institute of High Performance Computing A*STAR

Beyond graphene, the layered transition metal dichalcogenides （TMDs） have gained considerable attention due to their unique properties. Herein, we review the lattice dynamic and thermal properties of monolayer TMDs, including their phonon dispersion, relaxation time, mean free path （MFP）, and thermal conductivities. In particular, the experimental and theoretical studies reveal that the TMDs have relatively low thermal conductivities due to the short phonon group velocity and MFP, which poses a significant challenge for efficient thermal management of TMDs-based devices. Importantly, recent studies have shown that this issue could be largely addressed by connecting TMDs and other materials （such as metal electrode and graphene） with chemical bonds, and a relatively high interracial thermal conductance （ITC） could be achieved at the covalent bonded interface. The ITC of MoS2/Au interface with chemical edge contact is more than 10 times higher than that with physical side contact. In this article, we review recent advances in the study of TMD-related ITC. The effects of temperature, interfacial vacancy, contact orientation, and phonon modes on the edge-contacted interface are briefly discussed.

关键词： transition metal dichalcogenide MoS2 thermal conductivity interracial thermal conductance

Rapid synthesis of transition metal dichalcogenide-carbon aerogel composites for supercapacitor electrodes

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Microsystems & Nanoengineering 2017年第1期3卷 212-220页

作者： Matthew J.Crane Matthew B.Lim Xuezhe Zhou Peter J.Pauzauskie Department of Chemical Engineering University of WashingtonSeattleWA 98195-1750USA Department of Materials Science&Engineering University of WashingtonSeattleWA 98195-2120USA Fundamental&Computational Sciences Directorate Pacific Northwest National LaboratoryRichlandWA 99352USA

transition metal dichalcogenide(TMD)materials have recently demonstrated exceptional supercapacitor properties after conversion to a metallic phase,which increases the conductivity of the network.However,freestanding,exfoliated transition metal dichalcogenide films exhibit surface areas far below their theoretical maximum(1.2%),can fail during electrochemical operation due to poor mechanical properties,and often require pyrophoric chemicals to process.On the other hand,pyrolyzed carbon aerogels exhibit extraordinary specific surface areas for double layer capacitance,high conductivity,and a strong mechanical network of covalent chemical bonds.In this paper,we demonstrate the scalable,rapid nanomanufacturing of TMD(MoS2 and WS2)and carbon aerogel composites,favoring liquid-phase exfoliation to avoid pyrophoric chemicals.The aerogel matrix support enhances conductivity of the composite and the synthesis can complete in 30 min.We find that the addition of transition metal dichalcogenides does not impact the structure of the aerogel,which maintains a high specific surface area up to 620 m^(2) g−1 with peak pore radii of 10 nm.While supercapacitor tests of the aerogels yield capacitances around 80 F g^(−1) at the lowest applied currents,the aerogels loaded with TMD’s exhibit volumetric capacitances up to 127% greater than the unloaded aerogels.In addition,the WS2 aerogels show excellent cycling stability with no capacitance loss over 2000 cycles,as well as markedly better rate capability and lower charge transfer resistance compared to their MoS2-loaded counterparts.We hypothesize that these differences in performance stem from differences in contact resistance and in the favorability of ion adsorption on the chalcogenides.

关键词： aerogel molybdenum disulfide nanomanufacturing rapid resorcinol-formaldehyde supercapacitor transition metal dichalcogenide tungsten disulfide

Shallowing interfacial carrier trap in transition metal dichalcogenide heterostructures with interlayer hybridization

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Nano Research 2021年第5期14卷 1390-1396页

作者： Xu Wu Jingsi Qiao Liwei Liu Yan Shao Zhongliu Liu Linfei Li Zhili Zhu Cong Wang Zhixin Hu Wei Ji Yeliang Wang Hongjun Gao School of Information and Electronics MIIT Key Laboratory for Low-Dimensional Quantum Structure and DevicesBeijing Institute of TechnologyBeijing100081China Institute of Physics&University of Chinese Academy of Sciences Chinese Academy of SciencesBeijing100190China Beijing Key Laboratory of Optoelectronic Functional Materials&Micro-Nano Devices Department of PhysicsRenmin University of ChinaBeijing100872China Center for Joint Quantum Studies and Department of Physics Tianjin UniversityTianjin300350China CAS Center for Excellence in Topological Quantum Computation Beijing100049China

With the unique properties,layered transition metal dichalcogenide(TMD)and its heterostructures exhibit great potential for applications in electronics.The electrical performance,e.g.,contact barrier and resistance to electrodes,of TMD heterostructure devices can be significantly tailored by employing the functional layers,called interlayer engineering.At the interface between different TMD layers,the dangling-bond states normally exist and act as traps against charge carrier flow.In this study,we propose a technique to suppress such carrier trap that uses enhanced interlayer hybridization to saturate dangling-bond states,as demonstrated in a strongly interlayer-coupled monolayer-bilayer PtSe2 heterostructure.The hybridization between the unsaturated states and the interlayer electronic states of PtSe2 significantly reduces the depth of carrier traps at the interface,as corroborated by our scanning tunnelling spectroscopic measurements and density functional theory calculations.The suppressed interfacial trap demonstrates that interlayer saturation may offer an efficient way to relay the charge flow at the interface of TMD heterostructures.Thus,this technique provides an effective way for optimizing the interface contact,the crucial issue exists in two-dimensional electronic community.

关键词： transition metal dichalcogenide PtSe2 layered heterostructure band alignment strong interlayer interaction

Signal promoting role of a p-type transition metal dichalcogenide used for the detection of ultra-trace amounts of diclofenac via a labeled aptasensor

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Frontiers of Chemical Science and Engineering 2019年第4期13卷 823-831页

作者： Abdolhamid Hatefi-Mehrjardi Amirkhosro Beheshti-Marnani Zarrin Es'haghi Department of Chemisttry Payamc Noor University(PNU)TehranIran

A p-type transition metal dichalcogenide(WS2)was synthesized and hybridized with graphene oxide via a simple hydrothermal method.The as-prepared material was used to modify a glassy carbon electrode for the fabrication of a simple,stable,and repeatable methylene blue-labeled“signal-off”aptasensor used for the sensitive determination of very low amounts of sodium diclofenac(DCF).The synthetic material,modification process,and role of WS2 in the current response enhancement were studied by X-ray diffraction,energy-dispersive X-ray spectroscopy,field emission scanning electron microscopy,high resolution transmission electron microscopy,Hall effect,cyclic voltammetry,differential pulse voltammetry,and electrochemical impedance spectroscopy.Subsequently,a wide linear range of DCF concentration(0.5-300 nmol/L),very low limit of detection(0.23 nmol/L),and good selectivity were obtained using the differential pulse voltammetry method with the assembled aptasensor.Finally,the fabricated aptasensor was successfully developed for physiological real samples with significant recoveries.

关键词： labeled aptasensor transition metal dichalcogenide graphene oxide sodium diclofenac

Spatial variations of valley splitting in monolayer transition metal dichalcogenide

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InfoMat 2020年第3期2卷 585-592页

作者： Chenji Zou Hongbo Zhang Yu Chen Shun Feng Lishu Wu Jing Zhang Ting Yu Jingzhi Shang Chunxiao Cong Division of Physics and Applied Physics School of Physical and Mathematical SciencesNanyang Technological UniversitySingaporeSingapore Institute of Flexible Electronics Northwestern Polytechnical UniversityXi'anShaanxiChina State Key Laboratory of ASIC and System School of Information Science and TechnologyFudan UniversityShanghaiChina

In monolayer group-VI transition metal dichalcogenides(TMDs),valley splitting features have received a lot of attention since it can be potentially utilized for information storing and processing.Among the known two-dimensional(2D)TMDs,monolayer WSe2 or MoSe2 has been mostly selected for excitonic and valleytronic physics studies because of its sharp and well-resolved excitonic spectral features.Meanwhile,their high optical quality leads to a tremendous desire for developing promising WSe2-and MoSe2-based valleytronic devices.Toward this goal,exploring the uniformity of valley features crossing an entire piece of monolayer becomes necessary and critical.Here,we performed the systematic magnetophotoluminescence mapping measurements on mechanically exfoliated monolayer WSe2 and observed unconventional spatial variations of valley splitting.The observed nonuniformity is attributed to the modulated doping,which is probably due to the different distributions of unintentional absorbates across the sample.Such an unexpected doping effect shows the nonnegligible influence on the valley Zeeman splitting of the trion emission(XT)while affecting that of the neutral exciton emission(X0)trivially,evidencing for the large valleytronic sensitivity of the charged exciton.This work not only enriches the understanding of the doping effect on valley splitting but also is meaningful for developing 2D valleytronics.

关键词： doping effect monolayer WSe2 photoluminescence transition metal dichalcogenide valley splitting

Self-assembly tungsten selenide hybrid ternary MOF derived magnetic alloys via multi-polarization to boost microwave absorption

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Nano Research 2024年第3期17卷 1625-1635页

作者： Tianbao Zhao Tingting Zheng Di Lan Yan Zhang Zhengshuo Sun Chao Wang Zirui Jia Guanglei Wu Institute of Materials for Energy and Environment State Key Laboratory of Bio-fibers and Eco-textilesCollege of Materials Science and EngineeringQingdao UniversityQingdao 266071China School of Materials Science and Engineering Hubei University of Automotive TechnologyShiyan 442002China College of Chemistry and Chemical Engineering Qingdao UniversityQingdao 266071China

Confronted with severe electromagnetic wave pollution,the development of high-performance electromagnetic wave shielding or absorbing materials is an effective way to deal with it.Notably,double transition metal alloys and transition metal dichalcogenides have attracted extensive attention in electromagnetic wave absorption,but few reports have studied the effects of these two materials on electromagnetic wave absorption at the same time.In this work,cobalt-based alloy with magnetic loss mechanism was selected for composition optimization.The ternary metal-organic framework was prepared by the one-step method,and then CoCu/C was prepared by high temperature annealing.Finally,in the hydrothermal process,ultra-thin tungsten selenide nanosheets were coated on the surface of magnetic component,and the final polyhedral WSe_(2)/CoCu/C composites with multiple heterogeneous interfaces were obtained.The synergistic effect of dielectric and magnetic components optimizes impedance matching and allows more electromagnetic waves to enter the absorber.Subsequently,through the conduction loss of high conductivity graphitized carbon,interfacial polarization,and dipole polarization of heterogeneous interfaces between the components,the magnetic loss provided by CoCu alloy can work together to maximize the attenuation ability of electromagnetic waves.Exactly,the minimum reflection loss(RLmin)value of the composite reaches-53.43 dB when the matched thickness is 2.1 mm,while the maximum effective absorption bandwidth(EABmax)reaches 6.0 GHz at a thin thickness of 1.8 mm.This work provides some support and reference for the design of novel electromagnetic wave absorbing materials via the dielectric/magnetic loss synergistic mechanism.

关键词： metal-organic framework dielectric/magnetic loss transition metal dichalcogenide electromagnetic wave absorption