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Effects of interlayer coupling on the excitons and electronic structures of WS_(2)/hBN/MoS_(2) van der Waals heterostructures

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Nano Research 2022年第3期15卷 2674-2681页

作者： Xudan Zhu Junbo He Rongjun Zhang chunxiao cong Yuxiang Zheng Hao Zhang Songyou Wang Haibin Zhao Meiping Zhu Shanwen Zhang Shaojuan Li Liangyao Chen Key Laboratory of Micro and Nano Photonic Structures Ministry of EducationShanghai Engineering Research Center of Ultra-Precision Optical ManufacturingSchool of Information Science and EngineeringFudan UniversityShanghai 200433China State Key Laboratory of ASIC and System School of Information Science and EngineeringFudan UniversityShanghai 200433China Laboratory of Thin Film Optics Shanghai Institute of Optics and Fine MechanicsChinese Academy of SciencesShanghai 201800China Grating Technology Laboratory Changchun Institute of Optics and Fine Mechanics and PhysicsChinese Academy of SciencesChangchun 130033China State Key Laboratory of Applied Optics Changchun Institute of Optics Fine Mechanics and PhysicsChinese Academy of SciencesChangchun 130033China

Inserting hexagonal boron nitride(hBN)as barrier layers into bilayer transition metal dichalcogenides heterointerface has been proved an efficient method to improve two dimensional tunneling optoelectronic device performance.Nevertheless,the physical picture of interlayer coupling effect during incorporation of monolayer(1L-)hBN is not explicit yet.In this article,spectroscopic ellipsometry was used to experimentally obtain the broadband excitonic and critical point properties of WS_(2)/MoS_(2)and WS_(2)/hBN/MoS_(2)van der Waals heterostructures.We find that 1L-hBN can only slightly block the interlayer electron transfer from WS_(2)layer to MoS_(2)layer.Moreover,insertion of 1L-hBN weakens the interlayer coupling effect by releasing quantum confinement and reducing efficient dielectric screening.Consequently,the exciton binding energies in WS_(2)/hBN/MoS_(2)heterostructures blueshift comparing to those in WS_(2)/MoS_(2)heterostructures.In this exciton binding energies tuning process,the reducing dielectric screening effect plays a leading role.In the meantime,the quasi-particle(QP)bandgap remains unchanged before and after 1L-hBN insertion,which is attributed to released quantum confinement and decreased dielectric screening effects canceling each other.Unchanged QP bandgap as along with blueshift exciton binding energies lead to the redshift exciton transition energies in WS_(2)/hBN/MoS_(2)heterostructures.

关键词： two-dimensional(2D)van der Waals heterostructure interlayer coupling excitons critical points spectroscopic ellipsometry

Thermal conductivity determination of suspended mono- and bilayer WS2 by Raman spectroscopy

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Nano Research 2015年第4期8卷 1210-1221页

作者： Namphung Peimyoo Jingzhi Shang Weihuang Yang Yanlong wang chunxiao cong Ting Yu Division of Physics and Applied Physics School of Physical and Mathematical Sciences Nanyang Technological University 637371 Singapore Singapore Department of Physics Faculty of Science National University of Singapore 117542 Singapore Singapore Graphene Research Center Faculty of Science National University of Singapore 117546 Singapore Singapore

我们报导单层 1L 和 bilayer 2L WS 的热传导性化学蒸汽免职 CVD 种的 2 ，它被温度的使用和 E 的刺激依赖决定 2g 1 和 A 1g 拉曼模式。E 的一阶的温度系数 2g 1 和 A 1g 模式在支持了并且推迟 WS 2 层被提取。 A 的频率移... 详细信息

我们报导单层 1L 和 bilayer 2L WS 的热传导性化学蒸汽免职 CVD 种的 2 ，它被温度的使用和 E 的刺激依赖决定 2g 1 和 A 1g 拉曼模式。E 的一阶的温度系数 2g 1 和 A 1g 模式在支持了并且推迟 WS 2 层被提取。 A 的频率移动有温度的 1g 模式比 E 的大 2g 为 1L-WS 的 1 个模式 2 ,它被归因于为 A 联合的更强壮的电子声子 1g 模式比那为 E 2g 1 模式。而且由激光加热导致的声子模式的移动的使用，在房间温度的热传导性被估计是 32 和 53 W/mmine ICL 的全面功能。给 ICL 还没完成了一个自治学科的地位的事实，询问必须以 criminalisation 的国家理论的讨论开始。文章集中于 criminalisation 的二个很重要的理论，也就是理论 o 吗？

关键词：拉曼光谱 WS2 热导率化学气相沉积激光诱导加热发展中国家海藻酸钠声子耦合

High-performance polarization-sensitive photodetector based on a few-layered PdSe2 nanosheet

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Nano Research 2020年第6期13卷 1780-1786页

作者： Jiahong Zhong Juan Yu Lingkai Cao Cheng Zeng Junnan Ding chunxiao cong Zongwen Liu Yanping Liu School of Physics and Electronics Hunan Key Laboratory for Super-microstructure and Ultrafast ProcessCentral South UniversityChangsha410083China School of Electronics and Information Hangzhou Dianzi UniversityHangzhou310018China School of Information Science and Technology Fudan UniversityShanghai200433China School of Chemical and Biomolecular Engineering The University of SydneySydneyNSW2006Australia Shenzhen Research Institute of Central South University Shenzhen518057China State Key Laboratory of High Performance Complex Manufacturing Central South UniversityChangsha410083China

The extraordinary optical and electronic properties of anisotropic two-dimensional materials,such as black phosphorus,ReS2,and GeSe,enable them a promising component of polarization-sensitive photodetectors.However,these applications are significantly limited by the challenges of air-stability,response time,and linearly dichroic ratio.Interestingly,palladium diselenide(PdSe2)with high air stability is an emerging material that has robust in-plane anisotropy induced by its asymmetric pentagonal lattice structure.We have successfully prepared a few-layer PdSe2 using micromechanical exfoliation,and here we demonstrate the strong linear dichroism behavior of PdSe2 by polarization-resolved absorption spectra measurements.Such unique linear dichroism,endows the PdSe2 photodetector powerful ability to detect polarized light.The photodetector based on 5L PdSe2,as tested with polarization-dependent photocurrent mapping,exhibited competitive capability to detect polarized light,achieving a significant photocurrent on/off ratio(>10^2),the quite fast response time(<11 ms)and robust linearly dichroic ratios(/max//min≈1.9 at 532 nm).These results are essential advance in the development of polarization-sensitive photodetector,a crucial step towards opening up a new avenue for the application of 2D optoelectronic devices.

关键词： PdSe2 anisotropy polarization-sensitive linear dichroism

Electrical field tuning of magneto-Raman scattering in monolayer graphene

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Nano Research 2015年第4期8卷 1139-1147页

作者： Xiaonan Shen Caiyu Qiu Bingchen Cao chunxiao cong Weihuang Yang Haomin Wang Ting Yu Division of Physics and Applied Physics School of Physical and Mathematical Sciences Nanyang Technological University 637371 Singapore Singapore Wenzhou Institute of Biomaterials and Engineering Wenzhou 325001 China Department of Physics Faculty of Science National University of Singapore 117542 Singapore Singapore Graphene Research Center Faculty of Science National University of Singapore 117546 Singapore Singapore

在这个工作，我们报导在磁场下面在单层 graphene 磁电机声子回声调节直到 9 T 的电场。搬运人集中罐头急速地影响 G E，这被发现对通过显著磁电机声子回声 MPR 的一个变化磁场的 2g 声子反应。在负责中立或稍微做的单层 graphene，... 详细信息

在这个工作，我们报导在磁场下面在单层 graphene 磁电机声子回声调节直到 9 T 的电场。搬运人集中罐头急速地影响 G E，这被发现对通过显著磁电机声子回声 MPR 的一个变化磁场的 2g 声子反应。在负责中立或稍微做的单层 graphene，精力和 E 的线宽度 2g 声子表演有磁场的清楚的变化。这被归因于在 magnetoexcitations 和 E 之间的磁电机声子回声 2g 声子。相反，当单层 graphene 的费密水平是远的离开迪拉克点时， G 乐队显示出弱磁性的依赖并且展出对称的线形状。这建议在 4 T 附近联合的磁电机声子由于堵住的泡利不相容原理被关上了内部 -- 四轮马车水平刺激。而且， G 乐队不对称现象由在激子的许多身体状态和 E 之间的 Fano 回声引起了 2g 声子被观察。这个工作提供一个方法与一个外部电场通过 magneto-Raman 光谱学学习材料的 magnetoexcitation 声子相互作用。

关键词：拉曼光谱石墨单层电场调谐声子耦合散射载流子浓度

Remarkable anisotropic phonon response in uniaxially strained few-layer black phosphorus

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Nano Research 2015年第12期8卷 3944-3953页

作者： Yanlong Wang chunxiao cong Ruixiang Fei Weihuang Yang Yu Chen Bingchen Cao Li Yang Ting Yu Division of Physics and Applied Physics School of Physical and Mathematical Sciences Nanyang Technological University 637377 Singapore Department of Physics Washington University in St. Louis St. Louis Missouri 63130 USA Department of Physics Faculty of Science National University of Singapore 117542 Singapore

黑磷(BP ) 是一个好候选人因为学习紧张在 graphene 和转变金属 dichalcogenides 以外在 twodimensional (2D ) 上完成材料。这因为它支撑高紧张和源于它的唯一的皱起的结构的显著地各向异性的机械性质的特别能力。我们这里调查格子的... 详细信息

黑磷(BP ) 是一个好候选人因为学习紧张在 graphene 和转变金属 dichalcogenides 以外在 twodimensional (2D ) 上完成材料。这因为它支撑高紧张和源于它的唯一的皱起的结构的显著地各向异性的机械性质的特别能力。我们这里调查格子的依赖在由在原处做作的拉曼的单轴地做作的很少层 BP 的结晶的取向上的震动的频率光谱学。out-of-plane A 1 而， g 模式对沿着近扶手椅的方向的单轴的紧张敏感在里面飞机 B 2g 和 A 2 g 模式是敏感的在近之字形的方向拉紧。为使用离开这些方向的单轴的种类，所有三个声子模式是线性地 redshifted。我们的试验性的观察被对 BP 的结构的性质的单轴的张力的紧张的各向异性的影响用密度解释功能的理论。这研究表明由单轴的紧张的在 BP 的在里面飞机和 out-of-plane 声子模式的选择调节的可能性并且使紧张工程成为一条有希望的大街为广泛地 modulating 2D 材料的光、机械的性质。

关键词：声子模式各向异性高应变单轴过渡金属硫化物密度泛函理论磷结构特性

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

Unveiling the origin of anomalous low-frequency Raman mode in CVD-grown monolayer WS_(2)

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Nano Research 2021年第11期14卷 4314-4320页

作者： Qian Xiang Xiaofei Yue Yanlong Wang Bin Du Jiajun Chen Shaoqian Zhang Gang Li chunxiao cong Ting Yu Qingwei Li Yuqi Jin Key Laboratory of Chemical Lasers Dalian Institute of Chemical PhysicsChinese Academy of SciencesDalian116023China State Key Laboratory of ASIC&System School of Information Science and TechnologyFudan UniversityShanghai200433China School of Materials Science and Engineering Xi’an Polytechnic UniversityXi’an710048China Division of Physics and Applied Physics School of Physical and Mathematical SciencesNanyang Technological University637371SingaporeSingapore University of Chinese Academy of Sciences Beijing100049China

Substrates provide the necessary support for scientific explorations of numerous promising features and exciting potential applications in two-dimensional (2D) transition metal dichalcogenides (TMDs). To utilize substrate engineering to alter the properties of 2D TMDs and avoid introducing unwanted adverse effects, various experimental techniques, such as high-frequency Raman spectroscopy, have been used to understand the interactions between 2D TMDs and substrates. However, sample-substrate interaction in 2D TMDs is not yet fully understood due to the lack of systematic studies by techniques that are sensitive to 2D TMD-substrate interaction. This work systematically investigates the interaction between tungsten disulfide (WS_(2)) monolayers and substrates by low-frequency Raman spectroscopy, which is very sensitive to WS_(2)-substrate interaction. Strong coupling with substrates is clearly revealed in chemical vapor deposition (CVD)-grown monolayer WS_(2) by its low-wavenumber interface mode. It is demonstrated that the enhanced sample-substrate interaction leads to tensile strain on monolayer WS_(2), which is induced during the cooling process of CVD growth and could be released for monolayer WS_(2) sample after transfer or fabricated by an annealing-free method such as mechanical exfoliation. These results not only suggest the effectiveness of low-frequency Raman spectroscopy for probing sample-substrate interactions in 2D TMDs, but also provide guidance for the design of high-performance devices with the desired sample-substrate coupling strength based on 2D TMDs.

关键词： interface mode monolayer tungsten disulfide low-frequency Raman spectroscopy sample-substrate interaction strain chemical vapor deposition

Stacking monolayers at will:A scalable device optimization strategy for two-dimensional semiconductors

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Nano Research 2022年第7期15卷 6620-6627页

作者： Xiaojiao Guo Honglei Chen Jihong Bian Fuyou Liao Jingyi Ma Simeng Zhang Xinzhi Zhang Junqiang Zhu Chen Luo Zijian Zhang Lingyi Zong Yin Xia Chuming Sheng Zihan Xu Saifei Gou Xinyu Wang Peng Gong Liwei Liu Xixi Jiang Zhenghua An chunxiao cong Zhijun Qiu Xing Wu Peng Zhou Xinyu Chen Ling Tong Wenzhong Bao State Key Laboratory of ASIC and System School of MicroelectronicsZhangjiang Fudan International Innovation CenterFudan UniversityShanghai 200433China The Hong Kong Polytechnic University Shenzhen Research Institute Shenzhen 518057China Department of Physics State Key Laboratory of Surface PhysicsInstitute of Nanoelectronic Devices and Quantum Computing and Key Laboratory of MicroFudan UniversityShanghai 200433China State Key Laboratory of ASIC and System School of Information Science and EngineeringFudan UniversityShanghai 200433China Shanghai Key Laboratory of Multidimensional Information Processing Department of Electronic Engineering East China Normal UniversityShanghai 200241China Shenzhen Six Carbon Technology Shenzhen 518055China Department of Chemistry and Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials Fudan UniversityShanghai 200433China

In comparison to monolayer(1L),multilayer(ML)two-dimensional(2D)semiconducting transition metal dichalcogenides(TMDs)exhibit more application potential for electronic and optoelectronic devices due to their improved current carrying capability,higher mobility,and broader spectral response.However,the investigation of devices based on wafer-scale ML-TMDs is still restricted by the synthesis of uniform and high-quality ML films.In this work,we propose a strategy of stacking MoS_(2) monolayers via a vacuum transfer method,by which one could obtain wafer-scale high-quality MoS_(2) films with the desired number of layers at will.The optical characteristics of these stacked ML-MoS_(2) films(>2L)indicate a weak interlayer coupling.The stacked MLMoS_(2) phototransistors show improved optoelectrical performances and a broader spectral response(approximately 300-1,000 nm)than that of 1L-MoS_(2).Additionally,the dual-gate ML-MoS_(2) transistors enable enhanced electrostatic control over the stacked ML-MoS_(2) channel,and the 3L and 4L thicknesses exhibit the optimal device performances according to the turning point of the current on/off ratio and the subthreshold swing.

关键词： two-dimensional semiconductor field-effect transistors chemical vapor deposition(CVD)synthesis interlayer coupling vacuum transfer method dual-gate transistor

Intrinsic excitonic emission and valley Zeeman splitting in epitaxial MS2(M=Mo and W)monolayers on hexagonal boron nitride

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Nano Research 2018年第12期11卷 6227-6236页

作者： chunxiao cong Chenji Zou Bingchen Cao Lishu Wu Jingzhi Shahg Haomin Wang Zhijun Qiu Laigui Hu Pengfei Tian Ran Liu Ting Yu State Key Laboratory of ASIC and System School of Information Science and TechnologyFudan UniversityShanghai 200433China Division of Physics and Applied Physics School of Physical and Mathematical SciencesNanyang Technological UniversitySingapore 637371Singapore State Key Laboratory of Functional Materials for Informatics Shanghai Institute of Microsystem and Information TechnologyChinese Academy of Sciences865Changning RoadShanghai200050China

Two-dimensional (2D) semiconductors, represented by 2D transition metal dichalcogenides (TMDs), exhibit rich valley physics due to strong spin-orbit/spin-valley coupling. The most common way to probe such 2D systems is to utilize optical methods, which can monitor light emissions from various excitonic states and further help in understanding the physics behind such phenomena. Therefore, 2D TMDs with good optical quality are in great demand. Here, we report a method to directly grow epitaxial WS2 and MoS2 monolayers on hexagonal boron nitride (hBN) flakes with a high yield and high optical quality; these monolayers show better intrinsic light emission features than exfoliated monolayers from natural crystals. For the first time, the valley Zeeman splitting of WS2 and MoS2 monolayers on hBN has been visualized and systematically investigated. This study paves a new way to produce high optical quality WS2 and MoS2 monolayers and to exploit their intrinsic properties in a multitude of applications.

关键词： transition metal dichalcogenides intrinsic excitonic emission valley Zeeman splitting hexagonal boron nitride chemical vapor deposition