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Insight into vertical piezoelectric characteristics regulated thermal transport in van der Waals two-dimensional materials

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Rare Metals 2024年第2期43卷 770-779页

作者： Dong-Hai Wei E Zhou Jin-Yuan Xu Hui-Min Wang Chen Shen Hong-Bin Zhang Zhen-Zhen Qin Guang-Zhao Qin State key laboratory of Advanced Design and Manufacturing for Vehicle Body College of Mechanical and Vehicle EngineeringHunan UniversityChangsha410082China hunan key laboratory for micro-nano energy materials and device and school of physics and optoelectronics Xiangtan UniversityXiangtan411105China Institute of materials Science Technical University of DarmstadtAlarich-Weiss-Str.264287DarmstadtGermany school of physics and microelectronics Zhengzhou UniversityZhengzhou450001China

The urgent demand of extreme(ultra-high/low)thermal conductivity materials is triggered by the high-power device,where exploring the theories and mechanisms of regulating thermal transport properties plays a key ***,we elaborately investigate the effect of vertical(out-of-plane)piezoelectric characteristics on thermal transport,which is historically *** different stacking-order(AA and AB)bilayer boron nitride(Bi-BN)in two-dimensional(2D)materials are selected as study *** performing state-of-the-art first-principles calculations,it is found that the polarization charge along the out-of-plane orientation ascends significantly with the increasing piezoelectric response in AB stacked Bi-BN(Bi-BN-AB)followed by the enhanced interlayer B–N atomic ***,the amplitude of phonon anharmonicity in Bi-BN-AB increases larger than that in the AA stacked Bi-BN(Bi-BN-AA),resulting in the dramatic weakening of the thermal conductivity by 20.34%under 18%*** research reveals the significant role of the vertical(out-of-plane)piezoelectric characteristic in regulating thermal transport and provides new insight into accurately exploring the thermal transport performance of 2D van der Waals materials.

关键词： Thermal conductivity Piezoelectric effect 2D materials Bilayer BN Strain engineering

Efficient terahertz generation from van der Waalsα-In_(2)Se_(3)

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Chinese Optics Letters 2024年第1期22卷 141-146页

作者：段诗婕杨鸣周溯媛张隆辉韩锦森孙旭王广刘昌勤康冬冬王小伟陈家浩戴佳钰 Department of physics College of ScienceNational University of Defense TechnologyChangsha 410073China hunan key laboratory of Extreme Matter and Applications(XMAL) Changsha 410073China hunan key laboratory for micro-nano energy materials and devices School of Physics and OptoelectronicsXiangtan UniversityXiangtan 411105China Guangxi key laboratory of Automatic Detecting Technology and Instrument Guilin University of Electronic TechnologyGuilin 541004China

Two-dimensional(2D)van der Waals materials have attracted tremendous attention due to their versatile physical properties and flexible manipulation *** the various types of van der Waals materials,α-In_(2)Se_(3)is remarkable for its intrinsic 2D ferroelectricity and high-performance opto-electronic ***,the study of theα-In_(2)Se_(3)system in terahertz(THz)radiation is scarce,although it is promising for electrically controlled THz field *** investigate theα-In_(2)Se_(3)in different thicknesses and report that the THz generation efficiency induced by femtosecond laser pulses can be largely improved by reducing the thickness from the ***,we reveal the surge current in thin film coupled with THz emission exhibits a different Auger recombination mode,which is helpful in understanding the mechanism and provides insights into the design of 2D highly efficient THz devices.

关键词： van der Waals terahertz carrier dynamics

Layer-by-layer epitaxy growth of thickness-controllable two-dimensional tungsten disulfide

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Science China(Information Sciences) 2024年第5期67卷 302-310页

作者： Jieyuan LIANG Zixing ZOU Junwu LIANG Di WANG Biao WANG Anshi CHU Jiali YI Cheng ZHANG Lizhen FANG Tian ZHANG Huawei LIU Xiaoli ZHU Dong LI Anlian PAN key laboratory for micro-nano physics and Technology of hunan Province State Key Laboratory of Chemo/Biosensing and Chemometrics Hunan Institute of Optoelectronic IntegrationCollege of Materials Science and Engineering School of Physics and ElectronicsHunan University school of Electronic Information and Electrical Engineering Changsha University school of physics and Telecommunication Engineering Yulin Normal University Units Semiconductor Technology Co. Ltd. school of physics and Electronics Hunan Normal University

Bilayer transition metal dichalcogenides（TMDs） balance the high mobility of single layers with the high state density of multilayers and therefore have promising application prospects in high-performance electronics. However, the layer-controlled growth of 2D materials is still confronted with challenges such as poor repeatability between different labs and a limited understanding of the growth mechanism at the atomic scale. Herein, we report a new carbon-assisted chemical vapor deposition process that can realize the growth of WS2sheets with high yield, precise thickness controllability, and repeatability. We show that carbon can act as a reducing agent and catalyst that preferentially reacts with the WO3precursor to form intermediate WO3-xproducts with low-valence state W. The resulting oxycarbide gas has a low surface adsorption energy when deposited on the surface of as-grown WS2, which provides nucleation sites for the subsequent layer of WS2growth and leads to the vertical growth of WS2sheets. The growth mechanism is thoroughly investigated. Electrical transport measurements show that the produced bilayer WS2possesses a high carrier mobility(up to 58 cm2·V-1·s-1) and small subthreshold swing（estimated to be 148 mV/decade）,which are among the best reported results for TMDs produced using CVD.

关键词： WS$_2$ thickness-controlled growth chemical vapor deposition additive carbon

Competitive assembling strategy to construct carbon nitride homojunctions for boosting photocatalytic performance

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Journal of materials Science & Technology 2024年第5期172卷 23-32页

作者： Hua-Wei Zhang Yuan-Yuan Li Bo Li Jing-Hui Shi Tao Huang Gui-Fang Huang Anlian Pan Wangyu Hu Wei-Qing Huang school of physics&Electronic Engineering Zhengzhou University of Light IndustryZhengzhou 450002China key laboratory for micro/nano Optoelectronic devices of Ministry of Education&hunan Provincial key laboratory of Low-Dimensional Structural physics and devices School of Physics and ElectronicsHunan UniversityChangsha 410082China College of materials Science and Engineering Hunan UniversityChangsha 410082China

Both morphology and composition have a great influence on the properties and functions of materials,however,how to rational modulate both of them to achieve their synergistic effects has been a longstanding ***,we demonstrate a competitive assembling strategy for the construction of metal-free graphite carbon nitride(CN)homojunctions in which morphology and composition can be easily controlled simultaneously by only changing the ratio of assembly raw *** homojunctions are comprised of porous nanotubular S-doped CN(SCN)grafted with CN nanovesicles,which are derived from thermal polycondensation of melamine-thiocyanuric acid(M-T)/melamine-cyanuric acid(M-C)supramolecular hybrid *** unique architecture and component engineering endows the novel SCN-CN homojunction with abundant active sites,enhanced visible trapping ability,and intimate interface *** a result,the synthesized SCN-CN homojunctions demonstrate high photocatalytic activity for hydrogen evolution and pollutant *** developed strategy opens up intriguing opportu-nities for the rational construction of intricate metal-free heterostructures with controllable architecture and interfacial contact for applications in energy-related fields.

关键词： Competitive assembling strategy Supramolecular hybrid blocks Homojunctions Graphite carbon nitride Photocatalytic

Optical spectrum of ferrovalley materials:A case study of Janus H-VSSe

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Chinese physics B 2024年第1期33卷 54-59页

作者：罗朝波刘文超彭向阳 hunan key laboratory for micro-nano energy materials and devices School of Physics and OptoelectronicsXiangtan UniversityXiangtan 411105China

As opposed to the prototypical MoS2 with centroasymmetry,Janus ferrovalley materials such as H-VSSe are less symmetric with the mirror symmetry and time reversal symmetry broken,and hence possess spontaneous valley polarization and strong *** optical transition is an important means to excite the valley *** investigate the optical spectrum of H-VSSe by using the many-body perturbation-based GW approach and solving the Bethe–Salpeter equation(BSE)to include the electron–hole *** is found that after the GW correction,the band gaps of the quasiparticle bands are much larger than those obtained by the normal density functional *** system is ferromagnetic and the valley gaps become non-degenerate due to spin–orbit coupling(SOC).The position of the lowest BSE peak is much lower than the quasiparticle band gap,indicating that the excitonic effect is *** peak is split into two peaks by the *** binding energy difference between these two BSE peaks is about the same as the difference between the inequivalent valley *** results show that in Janus H-VSSe the two lowest exciton peaks are from the two inequivalent valleys with different gaps,in contrast to the A and B exciton peaks of MoS2 which are from the same valley.

关键词： infrared spectroscopy magnetic topological insulator Drude model band reconstruction

Graphene binding on black phosphorus enables high on/off ratios and mobility

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National Science Review 2024年第2期11卷 188-195页

作者： Fanrong Lin Zhonghan Cao Feiping Xiao Jiawei Liu Jiabin Qiao Minmin Xue Zhili Hu Ying Liu Huan Lu Zhuhua Zhang Jens Martin Qingjun Tong Wanlin Guo Yanpeng Liu key laboratory for Intelligent nano materials and devices of Ministry of Education State Key Laboratory of Mechanics and Control of Mechanical Structures and Institute for Frontier Science Nanjing University of Aeronautics and Astronautics Centre for Advanced 2D materials National University of Singapore school of physics and Electronics Hunan University Centre for Quantum physics Key Laboratory of Advanced Optoelectronic Quantum Architecture and MeasurementSchool of PhysicsBeijing Institute of Technology Leibniz Institute für Kristallzüchtung

Graphene is one of the most promising candidates for integrated circuits due to its robustness against short-channel effects, inherent high carrier mobility and desired gapless nature for Ohmic contact, but it is difficult to achieve satisfactory on/off ratios even at the expense of its carrier mobility, limiting its device applications. Here, we present a strategy to realize high back-gate switching ratios in a graphene monolayer with well-maintained high mobility by forming a vertical heterostructure with a black phosphorus multi-layer. By local current annealing, strain is introduced within an established area of the graphene, which forms a reflective interface with the rest of the strain-free area and thus generates a robust off-state via local current depletion. Applying a positive back-gate voltage to the heterostructure can keep the black phosphorus insulating, while a negative back-gate voltage changes the black phosphorus to be conductive because of hole accumulation. Then, a parallel channel is activated within the strain-free graphene area by edge-contacted electrodes, thereby largely inheriting the intrinsic carrier mobility of graphene in the on-state. As a result, the device can provide an on/off voltage ratio of >10～3 as well as a mobility of ～8000 cm2V-1s-1at room temperature, meeting the low-power criterion suggested by the International Roadmap for devices and Systems.

关键词： graphene on/off ratio mobility black phosphorus reflective interface

Quantum Anomalous Hall Effect with Tunable Chern Numbers in High-Temperature 1T-PrN_(2) Monolayer

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Chinese physics Letters 2024年第5期41卷 77-84页

作者：吴绪才李树宗司君山黄博张卫兵 hunan Provincial key laboratory of Flexible Electronic materials Genome Engineering School of Physics and Electronic SciencesChangsha University of Science and TechnologyChangsha 410114China

Quantum anomalous Hall(QAH) insulators have highly potential applications in spintronic device. However,available candidates with tunable Chern numbers and high working temperature are quite rare. Here, we predict a 1T-PrN_(2) monolayer as a stable QAH insulator with high magnetic transition temperature of above 600 K and tunable high Chern numbers of C = ±3 from first-principles calculations. Without spin-orbit coupling(SOC),the 1T-PrN_(2) monolayer is predicted to be a p-state Dirac half metal with high Fermi velocity. Rich topological phases depending on magnetization directions can be found when the SOC is considered. The QAH effect with periodical changes of Chern number(±1) can be produced when the magnetic moment breaks all twofold rotational symmetries in the xy plane. The critical state can be identified as Weyl half semimetals. When the magnetization direction is parallel to the z-axis, the system exhibits high Chern number QAH effect with C = ±*** work provides a new material for exploring novel QAH effect and developing high-performance topological devices.

关键词： magnetization topological monolayer

Controlled fabrication of freestanding monolayer SiC by electron irradiation

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Chinese physics B 2024年第8期33卷 31-37页

作者：笪蕴力罗瑞春雷宝季威周武 school of Physical Sciences University of Chinese Academy of SciencesBeijing 100049China Department of physics and Beijing key laboratory of Optoelectronic Functional materials&micro-nano devices Renmin University of ChinaBeijing 100872China

The design and preparation of novel quantum materials with atomic precision are crucial for exploring new physics and for device *** irradiation has been demonstrated as an effective method for preparing novel quantum materials and quantum structures that could be challenging to obtain *** features the advantages of precise control over the patterning of such new materials and their integration with other materials with different ***,we present a new strategy for fabricating freestanding monolayer SiC within nanopores of a graphene *** regulating the energy of the incident electron beam and the in-situ heating temperature in a scanning transmission electron microscope(STEM),we can effectively control the patterning of nanopores and subsequent growth of monolayer SiC within the graphene *** resultant SiC monolayers seamlessly connect with the graphene lattice,forming a planar structure distinct by a wide direct *** in-situ STEM observations further uncover that the growth of monolayer SiC within the graphene nanopore is driven by a combination of bond rotation and atom extrusion,providing new insights into the atom-by-atom self-assembly of freestanding two-dimensional(2D)monolayers.

关键词： monolayer SiC 2D semiconductor in-situ growth in-situ STEM defect engineering graphene nanopores

一种实现单层MoS_(2)光致发光显著增强的有效缺陷工程策略

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Science China materials 2024年第7期67卷 2232-2238页

作者：陈荧黄卓睿刘华伟喻国粮张金鼎徐哲元陈明星李东马超黄明朱小莉陈舒拉蒋英潘安练 key laboratory for micro-nano physics and Technology of hunan Province Hunan Institute of Optoelectronic IntegrationSchool of Physics and ElectronicsCollege of Materials Science and EngineeringHunan UniversityChangsha 410082China school of physics and Electronics Hunan Normal UniversityChangsha 410081China State key laboratory of Powder Metallurgy Central South UniversityChangsha 410083China

二维过渡金属硫族化合物(TMDCs)材料被认为是拓展摩尔定律的极具前景的候选材料.然而,该材料的低光致发光效率严重限制了其实际应用,其本质源于材料制备中不可避免引入的缺陷.在本文中,我们报道了一种Sr掺杂单层MoS_(2)的有效缺陷工程策... 详细信息

二维过渡金属硫族化合物(TMDCs)材料被认为是拓展摩尔定律的极具前景的候选材料.然而,该材料的低光致发光效率严重限制了其实际应用,其本质源于材料制备中不可避免引入的缺陷.在本文中,我们报道了一种Sr掺杂单层MoS_(2)的有效缺陷工程策略,该策略在实验上通过简便的化学气相沉积(CVD)一步法成功实现.所制备的具有亚毫米(~324μm)级的大尺寸样品的光致发光可实现高达两个数量级的增强,并伴随着载流子寿命的显著增强.这一现象主要归因于Sr掺杂后MoS_(2)体系中其三激子向激子转换.与此同时,掺杂样品的辐射质量和稳定性也显著提升.第一性原理计算进一步阐明了其调控机制,即在MoS_(2)中引入适当互补缺陷能级与其自身的缺陷能级协同,从而可调节其载流子组分,以实现光致发光的显著增强.此外,我们的缺陷工程策略也适用于其他掺杂剂,如钙掺杂剂.我们的工作报告了一种可以显著提升单层MoS_(2)的荧光性能的有效缺陷工程策略,这为设计和调控二维TMDCs的光电特性提供一种极具前途的方法.

关键词： MoS_(2) substitutional doping photoluminescence in-tensity enhancement first-principles calculations