1
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Jung J, Choi H, Lee Y, Kim Y, Taniguchi T, Watanabe K, Choi M, Jang JH, Chung H, Kim D, Kim Y, Cho C. Defect Passivation of 2D Semiconductors by Fixating Chemisorbed Oxygen Molecules via h-BN Encapsulations. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2024; 11:e2310197. [PMID: 38493313 PMCID: PMC11165525 DOI: 10.1002/advs.202310197] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2024] [Revised: 02/25/2024] [Indexed: 03/18/2024]
Abstract
Hexagonal boron nitride (h-BN) is a key ingredient for various 2D van der Waals heterostructure devices, but the exact role of h-BN encapsulation in relation to the internal defects of 2D semiconductors remains unclear. Here, it is reported that h-BN encapsulation greatly removes the defect-related gap states by stabilizing the chemisorbed oxygen molecules onto the defects of monolayer WS2 crystals. Electron energy loss spectroscopy (EELS) combined with theoretical analysis clearly confirms that the oxygen molecules are chemisorbed onto the defects of WS2 crystals and are fixated by h-BN encapsulation, with excluding a possibility of oxygen molecules trapped in bubbles or wrinkles formed at the interface between WS2 and h-BN. Optical spectroscopic studies show that h-BN encapsulation prevents the desorption of oxygen molecules over various excitation and ambient conditions, resulting in a greatly lowered and stabilized free electron density in monolayer WS2 crystals. This suppresses the exciton annihilation processes by two orders of magnitude compared to that of bare WS2. Furthermore, the valley polarization becomes robust against the various excitation and ambient conditions in the h-BN encapsulated WS2 crystals.
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Affiliation(s)
- Jin‐Woo Jung
- Department of Physics and ChemistryDaegu Gyeongbuk Institute of Science and Technology (DGIST)Daegu42988South Korea
| | - Hyeon‐Seo Choi
- Department of Physics and ChemistryDaegu Gyeongbuk Institute of Science and Technology (DGIST)Daegu42988South Korea
| | - Young‐Jun Lee
- Department of Physics and ChemistryDaegu Gyeongbuk Institute of Science and Technology (DGIST)Daegu42988South Korea
| | - Youngjae Kim
- School of PhysicsKorea Institute for Advanced Study (KIAS)Seoul02455South Korea
| | - Takashi Taniguchi
- International Center for Materials NanoarchitectonicsNational Institute for Materials ScienceTsukuba305‐0044Japan
| | - Kenji Watanabe
- Research Center for Functional MaterialsNational Institute for Materials ScienceTsukuba305‐0044Japan
| | - Min‐Yeong Choi
- Electron Microscopy and Spectroscopy TeamKorea Basic Science InstituteDaejeon34133South Korea
| | - Jae Hyuck Jang
- Electron Microscopy and Spectroscopy TeamKorea Basic Science InstituteDaejeon34133South Korea
- Graduate School of Analytic Science and TechnologyChungnam National UniversityDaejeon34134South Korea
| | - Hee‐Suk Chung
- Electron Microscopy and Spectroscopy TeamKorea Basic Science InstituteDaejeon34133South Korea
| | - Dohun Kim
- Department of Physics and ChemistryDaegu Gyeongbuk Institute of Science and Technology (DGIST)Daegu42988South Korea
| | - Youngwook Kim
- Department of Physics and ChemistryDaegu Gyeongbuk Institute of Science and Technology (DGIST)Daegu42988South Korea
| | - Chang‐Hee Cho
- Department of Physics and ChemistryDaegu Gyeongbuk Institute of Science and Technology (DGIST)Daegu42988South Korea
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2
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Qian W, Qi P, Dai Y, Shi B, Tao G, Liu H, Zhang X, Xiang D, Fang Z, Liu W. Strongly Localized Moiré Exciton in Twisted Homobilayers. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2024; 20:e2305200. [PMID: 37649150 DOI: 10.1002/smll.202305200] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2023] [Revised: 07/14/2023] [Indexed: 09/01/2023]
Abstract
Artificially molding exciton flux is the cornerstone for developing promising excitonic devices. In the emerging hetero/homobilayers, the spatial separated charges prolong exciton lifetimes and create out-plane dipoles, facilitating electrically control exciton flux on a large scale, and the nanoscale periodic moiré potentials arising from twist-angle or/and lattice mismatch can substantially alter exciton dynamics, which are mainly proved in the heterostructures. However, the spatially indirect excitons dynamics in homobilayers without lattice mismatch remain elusive. Here the nonequilibrium dynamics of indirect exciton in homobilayers are systematically investigated. The homobilayers with slightly twist-angle can induce a deep moiré potential (>50 meV) in the energy landscape of indirect excitons, resulting in a strongly localized moiré excitons insulating the transport dynamics from phonons and disorder. These findings provide insights into the exciton dynamics and many-body physics in moiré superlattices modulated energy landscape, with implications for designing excitonic devices operating at room temperature.
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Affiliation(s)
- Wenqi Qian
- Institute of Modern Optics, Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, Nankai University, Tianjin, 300350, China
| | - Pengfei Qi
- Institute of Modern Optics, Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, Nankai University, Tianjin, 300350, China
| | - Yuchen Dai
- School of Physics, State Key Laboratory for Mesoscopic Physics, Academy for Advanced Interdisciplinary Studies, Collaborative Innovation Center of Quantum Matter, Nano-optoelectronics Frontier Center of Ministry of Education, Peking University, Beijing, 100871, China
| | - Beibei Shi
- School of Physics, State Key Laboratory for Mesoscopic Physics, Academy for Advanced Interdisciplinary Studies, Collaborative Innovation Center of Quantum Matter, Nano-optoelectronics Frontier Center of Ministry of Education, Peking University, Beijing, 100871, China
| | - Guangyi Tao
- School of Physics, State Key Laboratory for Mesoscopic Physics, Academy for Advanced Interdisciplinary Studies, Collaborative Innovation Center of Quantum Matter, Nano-optoelectronics Frontier Center of Ministry of Education, Peking University, Beijing, 100871, China
| | - Haiyi Liu
- Institute of Modern Optics, Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, Nankai University, Tianjin, 300350, China
| | - Xubin Zhang
- Institute of Modern Optics, Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, Nankai University, Tianjin, 300350, China
| | - Dong Xiang
- Institute of Modern Optics, Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, Nankai University, Tianjin, 300350, China
| | - Zheyu Fang
- School of Physics, State Key Laboratory for Mesoscopic Physics, Academy for Advanced Interdisciplinary Studies, Collaborative Innovation Center of Quantum Matter, Nano-optoelectronics Frontier Center of Ministry of Education, Peking University, Beijing, 100871, China
| | - Weiwei Liu
- Institute of Modern Optics, Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, Nankai University, Tianjin, 300350, China
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3
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Zhu G, Zhang L, Li W, Shi X, Zou Z, Guo Q, Li X, Xu W, Jie J, Wang T, Du W, Xiong Q. Room-temperature high-speed electrical modulation of excitonic distribution in a monolayer semiconductor. Nat Commun 2023; 14:6701. [PMID: 37872139 PMCID: PMC10593816 DOI: 10.1038/s41467-023-42568-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2023] [Accepted: 10/16/2023] [Indexed: 10/25/2023] Open
Abstract
Excitons in monolayer semiconductors, benefitting from their large binding energies, hold great potential towards excitonic circuits bridging nano-electronics and photonics. However, achieving room-temperature ultrafast on-chip electrical modulation of excitonic distribution and flow in monolayer semiconductors is nontrivial. Here, utilizing lateral bias, we report high-speed electrical modulation of the excitonic distribution in a monolayer semiconductor junction at room temperature. The alternating charge trapping/detrapping at the two monolayer/electrode interfaces induces a non-uniform carrier distribution, leading to controlled in-plane spatial variations of excitonic populations, and mimicking a bias-driven excitonic flow. This modulation increases with the bias amplitude and eventually saturates, relating to the energetic distribution of trap density of states. The switching time of the modulation is down to 5 ns, enabling high-speed excitonic devices. Our findings reveal the trap-assisted exciton engineering in monolayer semiconductors and offer great opportunities for future two-dimensional excitonic devices and circuits.
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Affiliation(s)
- Guangpeng Zhu
- Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano and Soft Materials (FUNSOM), Soochow University, Suzhou, 215123, PR China
| | - Lan Zhang
- Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano and Soft Materials (FUNSOM), Soochow University, Suzhou, 215123, PR China
| | - Wenfei Li
- Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano and Soft Materials (FUNSOM), Soochow University, Suzhou, 215123, PR China
| | - Xiuqi Shi
- Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano and Soft Materials (FUNSOM), Soochow University, Suzhou, 215123, PR China
| | - Zhen Zou
- Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano and Soft Materials (FUNSOM), Soochow University, Suzhou, 215123, PR China
| | - Qianqian Guo
- Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano and Soft Materials (FUNSOM), Soochow University, Suzhou, 215123, PR China
| | - Xiang Li
- Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano and Soft Materials (FUNSOM), Soochow University, Suzhou, 215123, PR China
| | - Weigao Xu
- Key Laboratory of Mesoscopic Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, PR China
| | - Jiansheng Jie
- Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano and Soft Materials (FUNSOM), Soochow University, Suzhou, 215123, PR China
| | - Tao Wang
- Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano and Soft Materials (FUNSOM), Soochow University, Suzhou, 215123, PR China.
| | - Wei Du
- Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano and Soft Materials (FUNSOM), Soochow University, Suzhou, 215123, PR China.
| | - Qihua Xiong
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing, 100084, PR China
- Frontier Science Center for Quantum Information, Beijing, 100084, PR China
- Beijing Academy of Quantum Information Sciences, Beijing, 100193, PR China
- Collaborative Innovation Center of Quantum Matter, Beijing, PR China
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4
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Del Águila AG, Wong YR, Wadgaonkar I, Fieramosca A, Liu X, Vaklinova K, Dal Forno S, Do TTH, Wei HY, Watanabe K, Taniguchi T, Novoselov KS, Koperski M, Battiato M, Xiong Q. Ultrafast exciton fluid flow in an atomically thin MoS 2 semiconductor. NATURE NANOTECHNOLOGY 2023; 18:1012-1019. [PMID: 37524907 DOI: 10.1038/s41565-023-01438-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2022] [Accepted: 06/01/2023] [Indexed: 08/02/2023]
Abstract
Excitons (coupled electron-hole pairs) in semiconductors can form collective states that sometimes exhibit spectacular nonlinear properties. Here, we show experimental evidence of a collective state of short-lived excitons in a direct-bandgap, atomically thin MoS2 semiconductor whose propagation resembles that of a classical liquid as suggested by the nearly uniform photoluminescence through the MoS2 monolayer regardless of crystallographic defects and geometric constraints. The exciton fluid flows over ultralong distances (at least 60 μm) at a speed of ~1.8 × 107 m s-1 (~6% the speed of light). The collective phase emerges above a critical laser power, in the absence of free charges and below a critical temperature (usually Tc ≈ 150 K) approaching room temperature in hexagonal-boron-nitride-encapsulated devices. Our theoretical simulations suggest that momentum is conserved and local equilibrium is achieved among excitons; both these features are compatible with a fluid dynamics description of the exciton transport.
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Affiliation(s)
- Andrés Granados Del Águila
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore.
| | - Yi Ren Wong
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore
| | - Indrajit Wadgaonkar
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore
| | - Antonio Fieramosca
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore
| | - Xue Liu
- Institutes of Physical Science and Information Technology, Anhui University, Hefei, P.R. China
| | - Kristina Vaklinova
- Institute for Functional Intelligent Materials, National University of Singapore, Singapore, Singapore
| | - Stefano Dal Forno
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore
| | - T Thu Ha Do
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), Singapore, Republic of Singapore
| | - Ho Yi Wei
- Institute for Functional Intelligent Materials, National University of Singapore, Singapore, Singapore
- Department of Physics, National University of Singapore, Singapore, Singapore
| | - K Watanabe
- National Institute for Materials Science, Tsukuba, Japan
| | - T Taniguchi
- National Institute for Materials Science, Tsukuba, Japan
| | - Kostya S Novoselov
- Institute for Functional Intelligent Materials, National University of Singapore, Singapore, Singapore
- Department of Materials Science and Engineering, National University of Singapore, Singapore, Singapore
| | - Maciej Koperski
- Institute for Functional Intelligent Materials, National University of Singapore, Singapore, Singapore
- Department of Materials Science and Engineering, National University of Singapore, Singapore, Singapore
| | - Marco Battiato
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore
| | - Qihua Xiong
- State Key Laboratory of Low-Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing, P.R. China.
- Frontier Science Center for Quantum Information, Beijing, P.R. China.
- Collaborative Innovation Center of Quantum Matter, Beijing, P.R. China.
- Beijing Academy of Quantum Information Sciences, Beijing, P.R. China.
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5
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Kandoth N, Chaudhary SP, Gupta S, Raksha K, Chatterjee A, Gupta S, Karuthedath S, De Castro CSP, Laquai F, Pramanik SK, Bhattacharyya S, Mallick AI, Das A. Multimodal Biofilm Inactivation Using a Photocatalytic Bismuth Perovskite-TiO 2-Ru(II)polypyridyl-Based Multisite Heterojunction. ACS NANO 2023. [PMID: 37228184 DOI: 10.1021/acsnano.3c01064] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Infectious bacterial biofilms are recalcitrant to most antibiotics compared to their planktonic version, and the lack of appropriate therapeutic strategies for mitigating them poses a serious threat to clinical treatment. A ternary heterojunction material derived from a Bi-based perovskite-TiO2 hybrid and a [Ru(2,2'-bpy)2(4,4'-dicarboxy-2,2'-bpy)]2+ (2,2'-bpy, 2,2'-bipyridyl) as a photosensitizer (RuPS) is developed. This hybrid material is found to be capable of generating reactive oxygen species (ROS)/reactive nitrogen species (RNS) upon solar light irradiation. The aligned band edges and effective exciton dynamics between multisite heterojunctions are established by steady-state/time-resolved optical and other spectroscopic studies. Proposed mechanistic pathways for the photocatalytic generation of ROS/RNS are rationalized based on a cascade-redox processes arising from three catalytic centers. These ROS/RNS are utilized to demonstrate a proof-of-concept in treating two elusive bacterial biofilms while maintaining a high level of biocompatibility (IC50 > 1 mg/mL). The in situ generation of radical species (ROS/RNS) upon photoirradiation is established with EPR spectroscopic measurements and colorimetric assays. Experimental results showed improved efficacy toward biofilm inactivation of the ternary heterojunction material as compared to their individual/binary counterparts under solar light irradiation. The multisite heterojunction formation helped with better exciton delocalization for an efficient catalytic biofilm inactivation. This was rationalized based on the favorable exciton dissociation followed by the onset of multiple oxidation and reduction sites in the ternary heterojunction. This together with exceptional photoelectric features of lead-free halide perovskites outlines a proof-of-principle demonstration in biomedical optoelectronics addressing multimodal antibiofilm/antimicrobial modality.
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Affiliation(s)
- Noufal Kandoth
- Department of Chemical Sciences and Centre for Advanced Functional Materials, Indian Institute of Science Education and Research (IISER) Kolkata, Mohanpur 741246, India
| | - Sonu Pratap Chaudhary
- Department of Chemical Sciences and Centre for Advanced Functional Materials, Indian Institute of Science Education and Research (IISER) Kolkata, Mohanpur 741246, India
| | - Subhadeep Gupta
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) Kolkata, Mohanpur 741246, India
| | - Kumari Raksha
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Kolkata, Mohanpur 741246, India
| | - Atin Chatterjee
- Department of Chemical Sciences and Centre for Advanced Functional Materials, Indian Institute of Science Education and Research (IISER) Kolkata, Mohanpur 741246, India
| | - Shresth Gupta
- Department of Chemical Sciences and Centre for Advanced Functional Materials, Indian Institute of Science Education and Research (IISER) Kolkata, Mohanpur 741246, India
| | - Safakath Karuthedath
- KAUST Solar Center (KSC), Physical Science and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Kingdom of Saudi Arabia
| | - Catherine S P De Castro
- KAUST Solar Center (KSC), Physical Science and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Kingdom of Saudi Arabia
| | - Frédéric Laquai
- KAUST Solar Center (KSC), Physical Science and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Kingdom of Saudi Arabia
| | - Sumit Kumar Pramanik
- CSIR─Central Salt & Marine Chemicals Research Institute, Bhavnagar 364002, India
| | - Sayan Bhattacharyya
- Department of Chemical Sciences and Centre for Advanced Functional Materials, Indian Institute of Science Education and Research (IISER) Kolkata, Mohanpur 741246, India
| | - Amirul Islam Mallick
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) Kolkata, Mohanpur 741246, India
| | - Amitava Das
- Department of Chemical Sciences and Centre for Advanced Functional Materials, Indian Institute of Science Education and Research (IISER) Kolkata, Mohanpur 741246, India
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6
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Wagner K, Iakovlev ZA, Ziegler JD, Cuccu M, Taniguchi T, Watanabe K, Glazov MM, Chernikov A. Diffusion of Excitons in a Two-Dimensional Fermi Sea of Free Charges. NANO LETTERS 2023. [PMID: 37220259 DOI: 10.1021/acs.nanolett.2c03796] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Propagation of light-emitting quasiparticles is of central importance across the fields of condensed matter physics and nanomaterials science. We experimentally demonstrate diffusion of excitons in the presence of a continuously tunable Fermi sea of free charge carriers in a monolayer semiconductor. Light emission from tightly bound exciton states in electrically gated WSe2 monolayer is detected using spatially and temporally resolved microscopy. The measurements reveal a nonmonotonic dependence of the exciton diffusion coefficient on the charge carrier density in both electron and hole doped regimes. Supported by analytical theory describing exciton-carrier interactions in a dissipative system, we identify distinct regimes of elastic scattering and quasiparticle formation determining exciton diffusion. The crossover region exhibits a highly unusual behavior of an increasing diffusion coefficient with increasing carrier densities. Temperature-dependent diffusion measurements further reveal characteristic signatures of freely propagating excitonic complexes dressed by free charges with effective mobilities up to 3 × 103 cm2/(V s).
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Affiliation(s)
- Koloman Wagner
- Institute of Applied Physics and Wüzburg-Dresden Cluster of Excellence ct.qmat, Technische Universität Dresden, 01062 Dresden, Germany
- Department of Physics, University of Regensburg, 93053 Regensburg, Germany
| | | | - Jonas D Ziegler
- Institute of Applied Physics and Wüzburg-Dresden Cluster of Excellence ct.qmat, Technische Universität Dresden, 01062 Dresden, Germany
- Department of Physics, University of Regensburg, 93053 Regensburg, Germany
| | - Marzia Cuccu
- Institute of Applied Physics and Wüzburg-Dresden Cluster of Excellence ct.qmat, Technische Universität Dresden, 01062 Dresden, Germany
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Ibaraki 305-004, Japan
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Ibaraki 305-004, Japan
| | | | - Alexey Chernikov
- Institute of Applied Physics and Wüzburg-Dresden Cluster of Excellence ct.qmat, Technische Universität Dresden, 01062 Dresden, Germany
- Department of Physics, University of Regensburg, 93053 Regensburg, Germany
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7
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Wang X, Niu G, Jiang J, Sui L, Zeng X, Liu X, Zhang Y, Wu G, Yuan K, Yang X. Anomalous Dynamics of Defect-Assisted Phonon Recycling in Few-Layer Mo 0.5W 0.5S 2. J Phys Chem Lett 2022; 13:10395-10403. [PMID: 36318176 DOI: 10.1021/acs.jpclett.2c02935] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Alloying has emerged as a new strategy to tune the function of 2D transition metal dichalcogenides (TMDCs). However, the lack of research on the electrical and structural properties of these alloys limits their practical applications. Here, femtosecond transient absorption spectroscopy with pump pulse tunability is performed to elucidate the ultrafast carrier dynamics in the few-layer Mo0.5W0.5S2 prepared by the liquid phase exfoliation method. An anomalous rebleaching of the ground state is observed at high pump fluence by 3.1 eV excitation. We ascribe this rebleaching of the ground state to the mechanism that the carriers trapped in the defect are thermally excited back to the untrapped exciton state due to the phonon recycling, which hinders the dissipation of nonradiative energy, through comparative experiments and global analysis. Our findings demonstrate a novel energy transfer channel assisted by defect in few-layer TMDCs which is critical for their advanced applications.
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Affiliation(s)
- Xiaowei Wang
- State Key Laboratory of Molecular Reaction Dynamics and Dalian Coherent Light Source, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China
- University of the Chinese Academy of Sciences, Beijing 100039, China
| | - Guangming Niu
- State Key Laboratory of Molecular Reaction Dynamics and Dalian Coherent Light Source, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China
- Marine Engineering College, Dalian Maritime University, Dalian 116026, China
| | - Jutao Jiang
- State Key Laboratory of Molecular Reaction Dynamics and Dalian Coherent Light Source, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China
- University of the Chinese Academy of Sciences, Beijing 100039, China
| | - Laizhi Sui
- State Key Laboratory of Molecular Reaction Dynamics and Dalian Coherent Light Source, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China
| | - Xiangyu Zeng
- State Key Laboratory of Molecular Reaction Dynamics and Dalian Coherent Light Source, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China
- Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012, China
| | - Xin Liu
- State Key Laboratory of Molecular Reaction Dynamics and Dalian Coherent Light Source, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China
- Science College, Dalian Maritime University, Dalian 116026, China
| | - Yutong Zhang
- State Key Laboratory of Molecular Reaction Dynamics and Dalian Coherent Light Source, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China
| | - Guorong Wu
- State Key Laboratory of Molecular Reaction Dynamics and Dalian Coherent Light Source, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China
| | - Kaijun Yuan
- State Key Laboratory of Molecular Reaction Dynamics and Dalian Coherent Light Source, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China
| | - Xueming Yang
- State Key Laboratory of Molecular Reaction Dynamics and Dalian Coherent Light Source, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China
- Department of Chemistry, College of Science, Southern University of Science and Technology, Shenzhen 518055, China
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8
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Schedel C, Strauß F, Kohlschreiber P, Geladari O, Meixner AJ, Scheele M. Substrate effects on the speed limiting factor of WSe 2 photodetectors. Phys Chem Chem Phys 2022; 24:25383-25390. [PMID: 36239305 DOI: 10.1039/d2cp03364j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
We investigate the time-resolved photoelectric response of WSe2 crystals on glass and flexible polyimide substrates to determine the effect of a changed dielectric environment on the speed of the photodetectors. We show that varying the substrate material can alter the speed-limiting mechanism: while the detectors on polyimide are RC limited, those on glass are limited by slower excitonic diffusion processes. We attribute this to a shortening of the depletion layer at the metal electrode/WSe2 interface caused by the higher dielectric screening of glass compared to polyimide. The photodetectors on glass show a tunable bandwidth, which can be increased to 2.6 MHz with increasing the electric field.
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Affiliation(s)
- Christine Schedel
- Institute for Physical and Theoretical Chemistry, University of Tübingen, 72076 Tübingen, Germany
| | - Fabian Strauß
- Institute for Physical and Theoretical Chemistry, University of Tübingen, 72076 Tübingen, Germany
- Center for Light-Matter Interaction, Sensors and Analytics LISA+, University of Tübingen, 72076 Tübingen, Germany.
| | - Pia Kohlschreiber
- Institute for Physical and Theoretical Chemistry, University of Tübingen, 72076 Tübingen, Germany
| | - Olympia Geladari
- Institute for Physical and Theoretical Chemistry, University of Tübingen, 72076 Tübingen, Germany
| | - Alfred J Meixner
- Institute for Physical and Theoretical Chemistry, University of Tübingen, 72076 Tübingen, Germany
- Center for Light-Matter Interaction, Sensors and Analytics LISA+, University of Tübingen, 72076 Tübingen, Germany.
| | - Marcus Scheele
- Institute for Physical and Theoretical Chemistry, University of Tübingen, 72076 Tübingen, Germany
- Center for Light-Matter Interaction, Sensors and Analytics LISA+, University of Tübingen, 72076 Tübingen, Germany.
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9
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Sharma A, Zhu Y, Halbich R, Sun X, Zhang L, Wang B, Lu Y. Engineering the Dynamics and Transport of Excitons, Trions, and Biexcitons in Monolayer WS 2. ACS APPLIED MATERIALS & INTERFACES 2022; 14:41165-41177. [PMID: 36048513 DOI: 10.1021/acsami.2c08199] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
The study of transport and diffusion dynamics of quasi-particles such as excitons, trions, and biexcitons in two-dimensional (2D) semiconductors has opened avenues for their application in high-speed excitonic and optoelectronic devices. However, long-range transport and fast diffusion of these quasi-particles have not been reported for 2D systems such as transition metal dichalcogenides (TMDCs). The reported diffusion coefficients from TMDCs are low, limiting their use in high-speed excitonic devices and other optoelectronic applications. Here, we report the highest exciton diffusion coefficient value in monolayer WS2 achieved via engineering the radiative lifetime and diffusion lengths using static back-gate voltage and substrate engineering. Electrostatic doping is observed to modulate the radiative lifetime and in turn the diffusion coefficient of excitons by ∼three times at room temperature. By combining electrostatic doping and substrate engineering, we push the diffusion coefficient to an extremely high value of 86.5 cm2/s, which has not been reported before in TMDCs and is even higher than the values in some 1D systems. At low temperatures, we further report the control of dynamic and spatial diffusion of excitons, trions, and biexcitons from WS2. The electrostatic control of dynamics and transport of these quasi-particles in monolayers establishes monolayer TMDCs as ideal candidates for high-speed excitonic circuits, optoelectronic, and photonic device applications.
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Affiliation(s)
- Ankur Sharma
- School of Engineering, College of Engineering and Computer Science, The Australian National University, Canberra, ACT 2601, Australia
| | - Yi Zhu
- School of Engineering, College of Engineering and Computer Science, The Australian National University, Canberra, ACT 2601, Australia
- Department of Engineering, University of Cambridge, Cambridge CB3 0FA, United Kingdom
| | - Robert Halbich
- School of Engineering, College of Engineering and Computer Science, The Australian National University, Canberra, ACT 2601, Australia
| | - Xueqian Sun
- School of Engineering, College of Engineering and Computer Science, The Australian National University, Canberra, ACT 2601, Australia
| | - Linglong Zhang
- School of Engineering, College of Engineering and Computer Science, The Australian National University, Canberra, ACT 2601, Australia
| | - Bowen Wang
- School of Engineering, College of Engineering and Computer Science, The Australian National University, Canberra, ACT 2601, Australia
| | - Yuerui Lu
- School of Engineering, College of Engineering and Computer Science, The Australian National University, Canberra, ACT 2601, Australia
- ARC Centre of Excellence in Quantum Computation and Communication Technology ANU Node, Canberra, ACT 2601, Australia
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10
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Qian C, Villafañe V, Soubelet P, Hötger A, Taniguchi T, Watanabe K, Wilson NP, Stier AV, Holleitner AW, Finley JJ. Nonlocal Exciton-Photon Interactions in Hybrid High-Q Beam Nanocavities with Encapsulated MoS_{2} Monolayers. PHYSICAL REVIEW LETTERS 2022; 128:237403. [PMID: 35749182 DOI: 10.1103/physrevlett.128.237403] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Revised: 02/11/2022] [Accepted: 05/24/2022] [Indexed: 06/15/2023]
Abstract
Atomically thin semiconductors can be readily integrated into a wide range of nanophotonic architectures for applications in quantum photonics and novel optoelectronic devices. We report the observation of nonlocal interactions of "free" trions in pristine hBN/MoS_{2}/hBN heterostructures coupled to single mode (Q>10^{4}) quasi 0D nanocavities. The high excitonic and photonic quality of the interaction system stems from our integrated nanofabrication approach simultaneously with the hBN encapsulation and the maximized local cavity field amplitude within the MoS_{2} monolayer. We observe a nonmonotonic temperature dependence of the cavity-trion interaction strength, consistent with the nonlocal light-matter interactions in which the extent of the center-of-mass (c.m.) wave function is comparable to the cavity mode volume in space. Our approach can be generalized to other optically active 2D materials, opening the way toward harnessing novel light-matter interaction regimes for applications in quantum photonics.
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Affiliation(s)
- Chenjiang Qian
- Walter Schottky Institut and Physik Department, Technische Universität München, Am Coulombwall 4, 85748 Garching, Germany
| | - Viviana Villafañe
- Walter Schottky Institut and Physik Department, Technische Universität München, Am Coulombwall 4, 85748 Garching, Germany
| | - Pedro Soubelet
- Walter Schottky Institut and Physik Department, Technische Universität München, Am Coulombwall 4, 85748 Garching, Germany
| | - Alexander Hötger
- Walter Schottky Institut and Physik Department, Technische Universität München, Am Coulombwall 4, 85748 Garching, Germany
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Nathan P Wilson
- Walter Schottky Institut and Physik Department, Technische Universität München, Am Coulombwall 4, 85748 Garching, Germany
| | - Andreas V Stier
- Walter Schottky Institut and Physik Department, Technische Universität München, Am Coulombwall 4, 85748 Garching, Germany
| | - Alexander W Holleitner
- Walter Schottky Institut and Physik Department, Technische Universität München, Am Coulombwall 4, 85748 Garching, Germany
| | - Jonathan J Finley
- Walter Schottky Institut and Physik Department, Technische Universität München, Am Coulombwall 4, 85748 Garching, Germany
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11
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Liu Q, Wei K, Tang Y, Xu Z, Cheng X, Jiang T. Visualizing Hot-Carrier Expansion and Cascaded Transport in WS 2 by Ultrafast Transient Absorption Microscopy. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2022; 9:e2105746. [PMID: 35104054 PMCID: PMC8981895 DOI: 10.1002/advs.202105746] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/11/2021] [Revised: 01/04/2022] [Indexed: 06/14/2023]
Abstract
The competition between different spatiotemporal carrier relaxation determines the carrier harvesting in optoelectronic semiconductors, which can be greatly optimized by utilizing the ultrafast spatial expansion of highly energetic carriers before their energy dissipation via carrier-phonon interactions. Here, the excited-state dynamics in layered tungsten disulfide (WS2 ) are primarily imaged in the temporal, spatial, and spectral domains by transient absorption microscopy. Ultrafast hot carrier expansion is captured in the first 1.4 ps immediately after photoexcitation, with a mean diffusivity up to 980 cm2 s-1 . This carrier diffusivity then rapidly weakens, reaching a conventional linear spread of 10.5 cm2 s-1 after 2 ps after the hot carriers cool down to the band edge and form bound excitons. The novel carrier diffusion can be well characterized by a cascaded transport model including 3D thermal transport and thermo-optical conversion, in which the carrier temperature gradient and lattice thermal transport govern the initial hot carrier expansion and long-term exciton diffusion rates, respectively. The ultrafast hot carrier expansion breaks the limit of slow exciton diffusion in 2D transition metal dichalcogenides, providing potential guidance for high-performance applications and thermal management of optoelectronic technology.
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Affiliation(s)
- Qirui Liu
- College of Advanced Interdisciplinary Studies, National University of Defense Technology, Changsha, 410073, P. R. China
| | - Ke Wei
- State Key Laboratory of High Performance Computing, College of Computer, National University of Defense Technology, Changsha, 410073, P. R. China
- Beijing Institute for Advanced Study, National University of Defense Technology, Beijing, 100000, P. R. China
| | - Yuxiang Tang
- College of Advanced Interdisciplinary Studies, National University of Defense Technology, Changsha, 410073, P. R. China
| | - Zhongjie Xu
- College of Advanced Interdisciplinary Studies, National University of Defense Technology, Changsha, 410073, P. R. China
| | - Xiang'ai Cheng
- College of Advanced Interdisciplinary Studies, National University of Defense Technology, Changsha, 410073, P. R. China
| | - Tian Jiang
- Beijing Institute for Advanced Study, National University of Defense Technology, Beijing, 100000, P. R. China
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12
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Kim B, Luo Y, Rhodes D, Bai Y, Wang J, Liu S, Jordan A, Huang B, Li Z, Taniguchi T, Watanabe K, Owen J, Strauf S, Barmak K, Zhu X, Hone J. Free Trions with Near-Unity Quantum Yield in Monolayer MoSe 2. ACS NANO 2022; 16:140-147. [PMID: 34935357 DOI: 10.1021/acsnano.1c04331] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Trions, quasiparticles composed of an electron-hole pair bound to a second electron and/or hole, are many-body states with potential applications in optoelectronics. Trions in monolayer transition metal dichalcogenide (TMD) semiconductors have attracted recent interest due to their valley/spin polarization, strong binding energy, and tunability through external gate control. However, low materials quality (i.e., high defect density) has hindered efforts to understand the intrinsic properties of trions. The low photoluminescence (PL) quantum yield (QY) and short lifetime of trions have prevented harnessing them in device applications. Here, we study the behavior of trions in a series of MoSe2 monolayers, with atomic defect density varying by over 2 orders of magnitude. The QY increases with decreasing defect density and approaches unity in the cleanest material. Simultaneous measurement of the PL lifetime yields both the intrinsic radiative lifetime and the defect-dependent nonradiative lifetime. The long lifetime of ∼230 ps of trions allows direct observation of their diffusion.
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Affiliation(s)
- Bumho Kim
- Department of Mechanical Engineering, Columbia University, New York, New York 10027, United States
| | - Yue Luo
- Department of Physics, Stevens Institute of Technology, Hoboken, New Jersey 07030, United States
- Center for Nanoscale Systems, Harvard University, Cambridge, Massachusetts 02138, United States
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, United States
| | - Daniel Rhodes
- Department of Mechanical Engineering, Columbia University, New York, New York 10027, United States
| | - Yusong Bai
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Jue Wang
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Song Liu
- Department of Mechanical Engineering, Columbia University, New York, New York 10027, United States
| | - Abraham Jordan
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Baili Huang
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, United States
| | - Zhaochen Li
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, United States
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Jonathan Owen
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Stefan Strauf
- Department of Physics, Stevens Institute of Technology, Hoboken, New Jersey 07030, United States
| | - Katayun Barmak
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, United States
| | - Xiaoyang Zhu
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - James Hone
- Department of Mechanical Engineering, Columbia University, New York, New York 10027, United States
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13
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Rosati R, Wagner K, Brem S, Perea-Causín R, Ziegler JD, Zipfel J, Taniguchi T, Watanabe K, Chernikov A, Malic E. Non-equilibrium diffusion of dark excitons in atomically thin semiconductors. NANOSCALE 2021; 13:19966-19972. [PMID: 34821228 DOI: 10.1039/d1nr06230a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Atomically thin semiconductors provide an excellent platform to study intriguing many-particle physics of tightly-bound excitons. In particular, the properties of tungsten-based transition metal dichalcogenides are determined by a complex manifold of bright and dark exciton states. While dark excitons are known to dominate the relaxation dynamics and low-temperature photoluminescence, their impact on the spatial propagation of excitons has remained elusive. In our joint theory-experiment study, we address this intriguing regime of dark state transport by resolving the spatio-temporal exciton dynamics in hBN-encapsulated WSe2 monolayers after resonant excitation. We find clear evidence of an unconventional, time-dependent diffusion during the first tens of picoseconds, exhibiting strong deviation from the steady-state propagation. Dark exciton states are initially populated by phonon emission from the bright states, resulting in creation of hot (unequilibrated) excitons whose rapid expansion leads to a transient increase of the diffusion coefficient by more than one order of magnitude. These findings are relevant for both fundamental understanding of the spatio-temporal exciton dynamics in atomically thin materials as well as their technological application by enabling rapid diffusion.
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Affiliation(s)
- Roberto Rosati
- Department of Physics, Philipps-Universität Marburg, Renthof 7, D-35032 Marburg, Germany.
| | - Koloman Wagner
- Department of Physics, University of Regensburg, Regensburg D-93053, Germany
- Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Würzburg-Dresden Cluster of Excellence ct.qmat, Technische Universität Dresden, 01062 Dresden, Germany
| | - Samuel Brem
- Department of Physics, Philipps-Universität Marburg, Renthof 7, D-35032 Marburg, Germany.
| | - Raül Perea-Causín
- Chalmers University of Technology, Department of Physics, 412 96 Gothenburg, Sweden
| | - Jonas D Ziegler
- Department of Physics, University of Regensburg, Regensburg D-93053, Germany
- Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Würzburg-Dresden Cluster of Excellence ct.qmat, Technische Universität Dresden, 01062 Dresden, Germany
| | - Jonas Zipfel
- Department of Physics, University of Regensburg, Regensburg D-93053, Germany
- Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Ibaraki 305-004, Japan
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Ibaraki 305-004, Japan
| | - Alexey Chernikov
- Department of Physics, University of Regensburg, Regensburg D-93053, Germany
- Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Würzburg-Dresden Cluster of Excellence ct.qmat, Technische Universität Dresden, 01062 Dresden, Germany
| | - Ermin Malic
- Department of Physics, Philipps-Universität Marburg, Renthof 7, D-35032 Marburg, Germany.
- Chalmers University of Technology, Department of Physics, 412 96 Gothenburg, Sweden
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14
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Rosati R, Schmidt R, Brem S, Perea-Causín R, Niehues I, Kern J, Preuß JA, Schneider R, Michaelis de Vasconcellos S, Bratschitsch R, Malic E. Dark exciton anti-funneling in atomically thin semiconductors. Nat Commun 2021; 12:7221. [PMID: 34893602 PMCID: PMC8664915 DOI: 10.1038/s41467-021-27425-y] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2021] [Accepted: 11/16/2021] [Indexed: 11/09/2022] Open
Abstract
Transport of charge carriers is at the heart of current nanoelectronics. In conventional materials, electronic transport can be controlled by applying electric fields. Atomically thin semiconductors, however, are governed by excitons, which are neutral electron-hole pairs and as such cannot be controlled by electrical fields. Recently, strain engineering has been introduced to manipulate exciton propagation. Strain-induced energy gradients give rise to exciton funneling up to a micrometer range. Here, we combine spatiotemporal photoluminescence measurements with microscopic theory to track the way of excitons in time, space and energy. We find that excitons surprisingly move away from high-strain regions. This anti-funneling behavior can be ascribed to dark excitons which possess an opposite strain-induced energy variation compared to bright excitons. Our findings open new possibilities to control transport in exciton-dominated materials. Overall, our work represents a major advance in understanding exciton transport that is crucial for technological applications of atomically thin materials.
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Affiliation(s)
- Roberto Rosati
- Department of Physics, Philipps-Universität Marburg, 35032, Marburg, Germany
| | - Robert Schmidt
- Institute of Physics and Center for Nanotechnology, University of Münster, 48149, Münster, Germany
| | - Samuel Brem
- Department of Physics, Philipps-Universität Marburg, 35032, Marburg, Germany
| | - Raül Perea-Causín
- Chalmers University of Technology, Department of Physics, 412 96, Gothenburg, Sweden
| | - Iris Niehues
- Institute of Physics and Center for Nanotechnology, University of Münster, 48149, Münster, Germany
| | - Johannes Kern
- Institute of Physics and Center for Nanotechnology, University of Münster, 48149, Münster, Germany
| | - Johann A Preuß
- Institute of Physics and Center for Nanotechnology, University of Münster, 48149, Münster, Germany
| | - Robert Schneider
- Institute of Physics and Center for Nanotechnology, University of Münster, 48149, Münster, Germany
| | | | - Rudolf Bratschitsch
- Institute of Physics and Center for Nanotechnology, University of Münster, 48149, Münster, Germany.
| | - Ermin Malic
- Department of Physics, Philipps-Universität Marburg, 35032, Marburg, Germany.
- Chalmers University of Technology, Department of Physics, 412 96, Gothenburg, Sweden.
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15
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Li Z, Bretscher H, Zhang Y, Delport G, Xiao J, Lee A, Stranks SD, Rao A. Mechanistic insight into the chemical treatments of monolayer transition metal disulfides for photoluminescence enhancement. Nat Commun 2021; 12:6044. [PMID: 34663820 PMCID: PMC8523741 DOI: 10.1038/s41467-021-26340-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Accepted: 09/17/2021] [Indexed: 11/29/2022] Open
Abstract
There is a growing interest in obtaining high quality monolayer transition metal disulfides for optoelectronic applications. Surface treatments using a range of chemicals have proven effective to improve the photoluminescence yield of these materials. However, the underlying mechanism for the photoluminescence enhancement is not clear, which prevents a rational design of passivation strategies. Here, a simple and effective approach to significantly enhance the photoluminescence is demonstrated by using a family of cation donors, which we show to be much more effective than commonly used p-dopants. We develop a detailed mechanistic picture for the action of these cation donors and demonstrate that one of them, bis(trifluoromethane)sulfonimide lithium salt (Li-TFSI), enhances the photoluminescence of both MoS2 and WS2 to a level double that of the currently best performing super-acid trifluoromethanesulfonimide (H-TFSI) treatment. In addition, the ionic salts used in our treatments are compatible with greener solvents and are easier to handle than super-acids, providing the possibility of performing treatments during device fabrication. This work sets up rational selection rules for ionic chemicals to passivate transition metal disulfides and increases their potential in practical optoelectronic applications.
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Affiliation(s)
- Zhaojun Li
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, CB3 0HE, Cambridge, UK
- Molecular and Condensed Matter Physics, Department of Physics and Astronomy, Uppsala University, 75120, Uppsala, Sweden
| | - Hope Bretscher
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, CB3 0HE, Cambridge, UK
| | - Yunwei Zhang
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, CB3 0HE, Cambridge, UK
| | - Géraud Delport
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, CB3 0HE, Cambridge, UK
| | - James Xiao
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, CB3 0HE, Cambridge, UK
| | - Alpha Lee
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, CB3 0HE, Cambridge, UK
| | - Samuel D Stranks
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, CB3 0HE, Cambridge, UK
- Department of Chemical Engineering & Biotechnology, University of Cambridge, Philippa Fawcett Drive, CB3 0AS, Cambridge, UK
| | - Akshay Rao
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, CB3 0HE, Cambridge, UK.
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16
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Qiu DY, Cohen G, Novichkova D, Refaely-Abramson S. Signatures of Dimensionality and Symmetry in Exciton Band Structure: Consequences for Exciton Dynamics and Transport. NANO LETTERS 2021; 21:7644-7650. [PMID: 34463514 PMCID: PMC8890683 DOI: 10.1021/acs.nanolett.1c02352] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2021] [Revised: 08/25/2021] [Indexed: 05/25/2023]
Abstract
Exciton dynamics, lifetimes, and scattering are directly related to the exciton dispersion or band structure. Here, we present a general theory for exciton band structure within both ab initio and model Hamiltonian approaches. We show that contrary to common assumption, the exciton band structure contains nonanalytical discontinuities-a feature which is impossible to obtain from the electronic band structure alone. These discontinuities are purely quantum phenomena, arising from the exchange scattering of electron-hole pairs. We show that the degree of these discontinuities depends on materials' symmetry and dimensionality, with jump discontinuities occurring in 3D and different orders of removable discontinuities in 2D and 1D, whose details depend on the exciton degeneracy and material thickness. We connect these features to the early stages of exciton dynamics, radiative lifetimes, and diffusion constants, in good correspondence with recent experimental observations, revealing that the discontinuities in the band structure lead to ultrafast ballistic transport and suggesting that measured exciton diffusion and dynamics are influenced by the underlying exciton dispersion.
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Affiliation(s)
- Diana Y. Qiu
- Department
of Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut 06516, United States
| | - Galit Cohen
- Department
of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Dana Novichkova
- Department
of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Sivan Refaely-Abramson
- Department
of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Rehovot 7610001, Israel
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17
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Ma X, Zhang F, Chu Z, Hao J, Chen X, Quan J, Huang Z, Wang X, Li X, Yan Y, Zhu K, Lai K. Superior photo-carrier diffusion dynamics in organic-inorganic hybrid perovskites revealed by spatiotemporal conductivity imaging. Nat Commun 2021; 12:5009. [PMID: 34408145 PMCID: PMC8373981 DOI: 10.1038/s41467-021-25311-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Accepted: 08/04/2021] [Indexed: 11/09/2022] Open
Abstract
The outstanding performance of organic-inorganic metal trihalide solar cells benefits from the exceptional photo-physical properties of both electrons and holes in the material. Here, we directly probe the free-carrier dynamics in Cs-doped FAPbI3 thin films by spatiotemporal photoconductivity imaging. Using charge transport layers to selectively quench one type of carriers, we show that the two relaxation times on the order of 1 μs and 10 μs correspond to the lifetimes of electrons and holes in FACsPbI3, respectively. Strikingly, the diffusion mapping indicates that the difference in electron/hole lifetimes is largely compensated by their disparate mobility. Consequently, the long diffusion lengths (3~5 μm) of both carriers are comparable to each other, a feature closely related to the unique charge trapping and de-trapping processes in hybrid trihalide perovskites. Our results unveil the origin of superior diffusion dynamics in this material, crucially important for solar-cell applications.
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Affiliation(s)
- Xuejian Ma
- Department of Physics, University of Texas at Austin, Austin, TX, USA
| | - Fei Zhang
- Chemistry and Nanoscience Center, National Renewable Energy Laboratory, Golden, Colorado, CO, USA
| | - Zhaodong Chu
- Department of Physics, University of Texas at Austin, Austin, TX, USA
| | - Ji Hao
- Chemistry and Nanoscience Center, National Renewable Energy Laboratory, Golden, Colorado, CO, USA
| | - Xihan Chen
- Chemistry and Nanoscience Center, National Renewable Energy Laboratory, Golden, Colorado, CO, USA
| | - Jiamin Quan
- Department of Physics, University of Texas at Austin, Austin, TX, USA
| | - Zhiyuan Huang
- Chemistry and Nanoscience Center, National Renewable Energy Laboratory, Golden, Colorado, CO, USA
| | - Xiaoming Wang
- Department of Physics and Astronomy, University of Toledo, Toledo, OH, USA
| | - Xiaoqin Li
- Department of Physics, University of Texas at Austin, Austin, TX, USA
| | - Yanfa Yan
- Department of Physics and Astronomy, University of Toledo, Toledo, OH, USA
| | - Kai Zhu
- Chemistry and Nanoscience Center, National Renewable Energy Laboratory, Golden, Colorado, CO, USA.
| | - Keji Lai
- Department of Physics, University of Texas at Austin, Austin, TX, USA.
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18
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Wagner K, Zipfel J, Rosati R, Wietek E, Ziegler JD, Brem S, Perea-Causín R, Taniguchi T, Watanabe K, Glazov MM, Malic E, Chernikov A. Nonclassical Exciton Diffusion in Monolayer WSe_{2}. PHYSICAL REVIEW LETTERS 2021; 127:076801. [PMID: 34459627 DOI: 10.1103/physrevlett.127.076801] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Accepted: 06/24/2021] [Indexed: 06/13/2023]
Abstract
We experimentally demonstrate time-resolved exciton propagation in a monolayer semiconductor at cryogenic temperatures. Monitoring phonon-assisted recombination of dark states, we find a highly unusual case of exciton diffusion. While at 5 K the diffusivity is intrinsically limited by acoustic phonon scattering, we observe a pronounced decrease of the diffusion coefficient with increasing temperature, far below the activation threshold of higher-energy phonon modes. This behavior corresponds neither to well-known regimes of semiclassical free-particle transport nor to the thermally activated hopping in systems with strong localization. Its origin is discussed in the framework of both microscopic numerical and semiphenomenological analytical models illustrating the observed characteristics of nonclassical propagation. Challenging the established description of mobile excitons in monolayer semiconductors, these results open up avenues to study quantum transport phenomena for excitonic quasiparticles in atomically thin van der Waals materials and their heterostructures.
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Affiliation(s)
- Koloman Wagner
- Department of Physics, University of Regensburg, Regensburg D-93053, Germany
| | - Jonas Zipfel
- Department of Physics, University of Regensburg, Regensburg D-93053, Germany
- Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Roberto Rosati
- Department of Physics, Philipps-Universität Marburg, Renthof 7, Marburg D-35032, Germany
| | - Edith Wietek
- Department of Physics, University of Regensburg, Regensburg D-93053, Germany
| | - Jonas D Ziegler
- Department of Physics, University of Regensburg, Regensburg D-93053, Germany
| | - Samuel Brem
- Department of Physics, Philipps-Universität Marburg, Renthof 7, Marburg D-35032, Germany
| | - Raül Perea-Causín
- Department of Physics, Chalmers University of Technology, Fysikgården 1, 41258 Gothenburg, Sweden
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Ibaraki 305-004, Japan
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Ibaraki 305-004, Japan
| | | | - Ermin Malic
- Department of Physics, Philipps-Universität Marburg, Renthof 7, Marburg D-35032, Germany
- Department of Physics, Chalmers University of Technology, Fysikgården 1, 41258 Gothenburg, Sweden
| | - Alexey Chernikov
- Department of Physics, University of Regensburg, Regensburg D-93053, Germany
- Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Würzburg-Dresden Cluster of Excellence ct.qmat, Technische Universität Dresden, 01062 Dresden, Germany
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19
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Cheng G, Li B, Jin Z, Zhang M, Wang J. Observation of Diffusion and Drift of the Negative Trions in Monolayer WS 2. NANO LETTERS 2021; 21:6314-6320. [PMID: 34250802 DOI: 10.1021/acs.nanolett.1c02351] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Monolayer transition metal dichalcogenides (ML-TMDCs) are a versatile platform to explore the transport dynamics of the tightly bound excitonic states. The diffusion of neutral excitons in various ML-TMDCs has been observed. However, the transport of charged excitons (trions), which can be driven by an in-plane electric field and facilitate the formation of an excitonic current, has yet been well investigated. Here, we report the direct observation of diffusion and drift of the trions in ML-WS2 through spatially and time-resolved photoluminescence. An effective diffusion coefficient of 0.47 cm2/s was extracted from the broadening of spatial profiles of the trion emission. When an in-plane electric field is applied, the spatial shift of the trion emission profiles indicated a drift velocity of 7400 cm/s. Both the diffusion caused broadening and the drift caused shift of the emission profiles saturate because of the Coulomb interactions between trions and the background charges.
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Affiliation(s)
- Guanghui Cheng
- Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
- Department of Physics and Astronomy, Purdue Quantum Science and Engineering Institute, Purdue University, West Lafayette, Indiana 47907, United States
- WPI Advanced Institute for Materials Research (AIMR), Tohoku University, Sendai 980-8577, Japan
| | - Baikui Li
- Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen, Guangdong 518060, China
| | - Zijing Jin
- Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
| | - Meng Zhang
- Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen, Guangdong 518060, China
| | - Jiannong Wang
- Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
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20
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Shinokita K, Miyauchi Y, Watanabe K, Taniguchi T, Matsuda K. Resonant Coupling of a Moiré Exciton to a Phonon in a WSe 2/MoSe 2 Heterobilayer. NANO LETTERS 2021; 21:5938-5944. [PMID: 34269588 DOI: 10.1021/acs.nanolett.1c00733] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Moiré patterns with an angular mismatch in van der Waals heterostructures are a fascinating platform to engineer optically generated excitonic properties. The moiré pattern can give rise to spatially ordered exciton ensembles, which offer the possibility for coherent quantum emitters and quantum simulation of many-body physics. The intriguing moiré exciton properties are affected by their dynamics and exciton-phonon interaction. Here, we report the moiré exciton and phonon interaction in a twisted WSe2/MoSe2 heterobilayer. By tuning the excitation energy, we realized the selective excitation of the moiré exciton at phonon resonances and the otherwise negligible small absorption. Furthermore, we revealed the relaxation of moiré exciton ensembles between different potential minima via the resonant phonon scattering process. Our findings highlight resonant coupling of a moiré exciton to a phonon and could pave a new way for the exploration of novel quantum phenomena of the moiré exciton.
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Affiliation(s)
- Keisuke Shinokita
- Institute of Advanced Energy, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Yuhei Miyauchi
- Institute of Advanced Energy, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
| | - Kazunari Matsuda
- Institute of Advanced Energy, Kyoto University, Uji, Kyoto 611-0011, Japan
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21
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Yildirim T, Zhang L, Neupane GP, Chen S, Zhang J, Yan H, Hasan MM, Yoshikawa G, Lu Y. Towards future physics and applications via two-dimensional material NEMS resonators. NANOSCALE 2020; 12:22366-22385. [PMID: 33150899 DOI: 10.1039/d0nr06773c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Two-dimensional materials (2Dm) offer a unique insight into the world of quantum mechanics including van der Waals (vdWs) interactions, exciton dynamics and various other nanoscale phenomena. 2Dm are a growing family consisting of graphene, hexagonal-Boron Nitride (h-BN), transition metal dichalcogenides (TMDs), monochalcogenides (MNs), black phosphorus (BP), MXenes and 2D organic crystals such as small molecules (e.g., pentacene, C8 BTBT, perylene derivatives, etc.) and polymers (e.g., COF and MOF, etc.). They exhibit unique mechanical, electrical, optical and optoelectronic properties that are highly enhanced as the surface to volume ratio increases, resulting from the transition of bulk to the few- to mono- layer limit. Such unique attributes include the manifestation of highly tuneable bandgap semiconductors, reduced dielectric screening, highly enhanced many body interactions, the ability to withstand high strains, ferromagnetism, piezoelectric and flexoelectric effects. Using 2Dm for mechanical resonators has become a promising field in nanoelectromechanical systems (NEMS) for applications involving sensors and condensed matter physics investigations. 2Dm NEMS resonators react with their environment, exhibit highly nonlinear behaviour from tension induced stiffening effects and couple different physics domains. The small size and high stiffness of these devices possess the potential of highly enhanced force sensitivities for measuring a wide variety of un-investigated physical forces. This review highlights current research in 2Dm NEMS resonators from fundamental physics and an applications standpoint, as well as presenting future possibilities using these devices.
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Affiliation(s)
- Tanju Yildirim
- Center for Functional Sensor & Actuator (CFSN), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan.
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22
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Glazov MM, Golub LE. Skew Scattering and Side Jump Drive Exciton Valley Hall Effect in Two-Dimensional Crystals. PHYSICAL REVIEW LETTERS 2020; 125:157403. [PMID: 33095628 DOI: 10.1103/physrevlett.125.157403] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Accepted: 09/03/2020] [Indexed: 06/11/2023]
Abstract
Exciton valley Hall effect is the spatial separation of the valley-tagged excitons by a drag force. Usually, the effect is associated with the anomalous velocity acquired by the particles due to the Berry curvature of the Bloch bands. Here we show that the anomalous velocity plays no role in the exciton valley Hall effect, which is governed by the side-jump and skew scattering. We develop a microscopic theory of the exciton valley Hall effect in the presence of a synthetic electric field and phonon drag and calculate all relevant contributions to the valley Hall current also demonstrating the cancellation of the anomalous velocity. The sensitivity of the effect to the origin of the drag force and to the scattering processes is shown. We extend the drift-diffusion model to account for the valley Hall effect and calculate the exciton density and valley polarization profiles.
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Affiliation(s)
- M M Glazov
- Ioffe Institute, 194021 St. Petersburg, Russia
| | - L E Golub
- Ioffe Institute, 194021 St. Petersburg, Russia
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23
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Sharma A, Zhang L, Tollerud JO, Dong M, Zhu Y, Halbich R, Vogl T, Liang K, Nguyen HT, Wang F, Sanwlani S, Earl SK, Macdonald D, Lam PK, Davis JA, Lu Y. Supertransport of excitons in atomically thin organic semiconductors at the 2D quantum limit. LIGHT, SCIENCE & APPLICATIONS 2020; 9:116. [PMID: 32655861 PMCID: PMC7338549 DOI: 10.1038/s41377-020-00347-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2020] [Revised: 05/14/2020] [Accepted: 06/09/2020] [Indexed: 05/20/2023]
Abstract
Long-range and fast transport of coherent excitons is important for the development of high-speed excitonic circuits and quantum computing applications. However, most of these coherent excitons have only been observed in some low-dimensional semiconductors when coupled with cavities, as there are large inhomogeneous broadening and dephasing effects on the transport of excitons in their native states in materials. Here, by confining coherent excitons at the 2D quantum limit, we first observed molecular aggregation-enabled 'supertransport' of excitons in atomically thin two-dimensional (2D) organic semiconductors between coherent states, with a measured high effective exciton diffusion coefficient of ~346.9 cm2/s at room temperature. This value is one to several orders of magnitude higher than the values reported for other organic molecular aggregates and low-dimensional inorganic materials. Without coupling to any optical cavities, the monolayer pentacene sample, a very clean 2D quantum system (~1.2 nm thick) with high crystallinity (J-type aggregation) and minimal interfacial states, showed superradiant emission from Frenkel excitons, which was experimentally confirmed by the temperature-dependent photoluminescence (PL) emission, highly enhanced radiative decay rate, significantly narrowed PL peak width and strongly directional in-plane emission. The coherence in monolayer pentacene samples was observed to be delocalised over ~135 molecules, which is significantly larger than the values (a few molecules) observed for other organic thin films. In addition, the supertransport of excitons in monolayer pentacene samples showed highly anisotropic behaviour. Our results pave the way for the development of future high-speed excitonic circuits, fast OLEDs, and other optoelectronic devices.
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Affiliation(s)
- Ankur Sharma
- Research School of Electrical, Energy and Materials Engineering, College of Engineering and Computer Science, The Australian National University, Canberra, ACT 2601 Australia
| | - Linglong Zhang
- Research School of Electrical, Energy and Materials Engineering, College of Engineering and Computer Science, The Australian National University, Canberra, ACT 2601 Australia
| | - Jonathan O. Tollerud
- Optical Sciences Centre, Swinburne University of Technology, Hawthorn, VIC 3122 Australia
- ARC Centre of Excellence for Future Low-Energy Electronics Technology, Australia
| | - Miheng Dong
- Research School of Electrical, Energy and Materials Engineering, College of Engineering and Computer Science, The Australian National University, Canberra, ACT 2601 Australia
| | - Yi Zhu
- Research School of Electrical, Energy and Materials Engineering, College of Engineering and Computer Science, The Australian National University, Canberra, ACT 2601 Australia
| | - Robert Halbich
- Research School of Electrical, Energy and Materials Engineering, College of Engineering and Computer Science, The Australian National University, Canberra, ACT 2601 Australia
| | - Tobias Vogl
- Centre for Quantum Computation and Communication Technology, Department of Quantum Science, Research School of Physics and Engineering, The Australian National University, Acton, ACT 2601 Australia
| | - Kun Liang
- Research School of Electrical, Energy and Materials Engineering, College of Engineering and Computer Science, The Australian National University, Canberra, ACT 2601 Australia
- School of Mechatronical Engineering, Beijing Institute of Technology, Beijing, 100081 China
| | - Hieu T. Nguyen
- Research School of Electrical, Energy and Materials Engineering, College of Engineering and Computer Science, The Australian National University, Canberra, ACT 2601 Australia
| | - Fan Wang
- Institute for Biomedical Materials and Devices (IBMD), Faculty of Science, University of Technology Sydney, Sydney, NSW 2007 Australia
| | - Shilpa Sanwlani
- Optical Sciences Centre, Swinburne University of Technology, Hawthorn, VIC 3122 Australia
- ARC Centre of Excellence for Future Low-Energy Electronics Technology, Australia
| | - Stuart K. Earl
- Optical Sciences Centre, Swinburne University of Technology, Hawthorn, VIC 3122 Australia
- ARC Centre of Excellence for Future Low-Energy Electronics Technology, Australia
| | - Daniel Macdonald
- Research School of Electrical, Energy and Materials Engineering, College of Engineering and Computer Science, The Australian National University, Canberra, ACT 2601 Australia
| | - Ping Koy Lam
- Centre for Quantum Computation and Communication Technology, Department of Quantum Science, Research School of Physics and Engineering, The Australian National University, Acton, ACT 2601 Australia
| | - Jeffrey A. Davis
- Optical Sciences Centre, Swinburne University of Technology, Hawthorn, VIC 3122 Australia
- ARC Centre of Excellence for Future Low-Energy Electronics Technology, Australia
| | - Yuerui Lu
- Research School of Electrical, Energy and Materials Engineering, College of Engineering and Computer Science, The Australian National University, Canberra, ACT 2601 Australia
- ARC Centre of Excellence for Future Low-Energy Electronics Technology, Australia
- Centre for Quantum Computation and Communication Technology, Department of Quantum Science, Research School of Physics and Engineering, The Australian National University, Acton, ACT 2601 Australia
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24
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Chu Z, Wang CY, Quan J, Zhang C, Lei C, Han A, Ma X, Tang HL, Abeysinghe D, Staab M, Zhang X, MacDonald AH, Tung V, Li X, Shih CK, Lai K. Unveiling defect-mediated carrier dynamics in monolayer semiconductors by spatiotemporal microwave imaging. Proc Natl Acad Sci U S A 2020; 117:13908-13913. [PMID: 32513713 PMCID: PMC7322012 DOI: 10.1073/pnas.2004106117] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The optoelectronic properties of atomically thin transition-metal dichalcogenides are strongly correlated with the presence of defects in the materials, which are not necessarily detrimental for certain applications. For instance, defects can lead to an enhanced photoconduction, a complicated process involving charge generation and recombination in the time domain and carrier transport in the spatial domain. Here, we report the simultaneous spatial and temporal photoconductivity imaging in two types of WS2 monolayers by laser-illuminated microwave impedance microscopy. The diffusion length and carrier lifetime were directly extracted from the spatial profile and temporal relaxation of microwave signals, respectively. Time-resolved experiments indicate that the critical process for photoexcited carriers is the escape of holes from trap states, which prolongs the apparent lifetime of mobile electrons in the conduction band. As a result, counterintuitively, the long-lived photoconductivity signal is higher in chemical-vapor deposited (CVD) samples than exfoliated monolayers due to the presence of traps that inhibits recombination. Our work reveals the intrinsic time and length scales of electrical response to photoexcitation in van der Waals materials, which is essential for their applications in optoelectronic devices.
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Affiliation(s)
- Zhaodong Chu
- Department of Physics, The University of Texas at Austin, Austin, TX 78712
| | - Chun-Yuan Wang
- Department of Physics, The University of Texas at Austin, Austin, TX 78712
| | - Jiamin Quan
- Department of Physics, The University of Texas at Austin, Austin, TX 78712
| | - Chenhui Zhang
- Physical Sciences and Engineering Division, King Abdullah University of Science and Technology, 23955-6900 Thuwal, Kingdom of Saudi Arabia
| | - Chao Lei
- Department of Physics, The University of Texas at Austin, Austin, TX 78712
| | - Ali Han
- Physical Sciences and Engineering Division, King Abdullah University of Science and Technology, 23955-6900 Thuwal, Kingdom of Saudi Arabia
| | - Xuejian Ma
- Department of Physics, The University of Texas at Austin, Austin, TX 78712
| | - Hao-Ling Tang
- Physical Sciences and Engineering Division, King Abdullah University of Science and Technology, 23955-6900 Thuwal, Kingdom of Saudi Arabia
| | - Dishan Abeysinghe
- Department of Physics, The University of Texas at Austin, Austin, TX 78712
| | - Matthew Staab
- Department of Physics, The University of Texas at Austin, Austin, TX 78712
| | - Xixiang Zhang
- Physical Sciences and Engineering Division, King Abdullah University of Science and Technology, 23955-6900 Thuwal, Kingdom of Saudi Arabia
| | - Allan H MacDonald
- Department of Physics, The University of Texas at Austin, Austin, TX 78712
| | - Vincent Tung
- Physical Sciences and Engineering Division, King Abdullah University of Science and Technology, 23955-6900 Thuwal, Kingdom of Saudi Arabia
| | - Xiaoqin Li
- Department of Physics, The University of Texas at Austin, Austin, TX 78712
| | - Chih-Kang Shih
- Department of Physics, The University of Texas at Austin, Austin, TX 78712
| | - Keji Lai
- Department of Physics, The University of Texas at Austin, Austin, TX 78712;
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25
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Zhang D, Gan L, Zhang J, Zhang R, Wang Z, Feng J, Sun H, Ning CZ. Reconstructing Local Profile of Exciton-Emission Wavelengths across a WS 2 Bubble beyond the Diffraction Limit. ACS NANO 2020; 14:6931-6937. [PMID: 32491830 DOI: 10.1021/acsnano.0c01337] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Air bubbles formed between layers of two-dimensional (2D) materials not only are unavoidable but also emerge as an important means of engineering their excitonic emission properties, especially as controllable quantum light sources. Measuring the actual spatially resolved optical properties across such bubbles is important for understanding excitonic physics and for device applications; however, such a measurement is challenging due to nanoscale features involved which require spatial resolution beyond the diffraction limit. Additional complexity is the involvement of multiple physical effects such as mechanical strain and dielectric environment that are difficult to disentangle. In this paper, we demonstrate an effective approach combining micro-photoluminescence measurement, atomic force microscope profile mapping, and a theoretical strain model. We succeeded in reconstructing the actual spatial profiles of the emission wavelengths beyond the diffraction limit for bubbles formed by a monolayer tungsten disulfide on boron nitride. The agreements and consistency among various approaches established the validity of our approach. In addition, our approach allows us to disentangle the effects of strain and dielectric environment and provides a general and reliable method to determine the true magnitude of wavelength changes due to the individual effects across bubbles. Importantly, we found that micro-optical measurement underestimates the red and blue shifts by almost 5 times. Our results provide important insights into strain and screening-dependent optical properties of 2D materials on the nanometer scale and contribute significantly to our understanding of excitonic emission physics as well as potential applications of bubbles in optoelectronic devices.
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Affiliation(s)
- Danyang Zhang
- Department of Electronic Engineering, Tsinghua University, Beijing 100084, China
- International Center for Nano-Optoelectronics, Tsinghua University, Beijing 100084, China
| | - Lin Gan
- Department of Electronic Engineering, Tsinghua University, Beijing 100084, China
- Frontier Science Center for Quantum Information, Beijing 100084, China
- International Center for Nano-Optoelectronics, Tsinghua University, Beijing 100084, China
- Beijing National Research Center for Information Science and Technology, Beijing 100084, China
| | - Jianxing Zhang
- Department of Electronic Engineering, Tsinghua University, Beijing 100084, China
- International Center for Nano-Optoelectronics, Tsinghua University, Beijing 100084, China
| | - Ruiling Zhang
- Department of Electronic Engineering, Tsinghua University, Beijing 100084, China
- International Center for Nano-Optoelectronics, Tsinghua University, Beijing 100084, China
| | - Zhen Wang
- Department of Electronic Engineering, Tsinghua University, Beijing 100084, China
- International Center for Nano-Optoelectronics, Tsinghua University, Beijing 100084, China
| | - Jiabin Feng
- Department of Electronic Engineering, Tsinghua University, Beijing 100084, China
- International Center for Nano-Optoelectronics, Tsinghua University, Beijing 100084, China
| | - Hao Sun
- Department of Electronic Engineering, Tsinghua University, Beijing 100084, China
- Frontier Science Center for Quantum Information, Beijing 100084, China
- International Center for Nano-Optoelectronics, Tsinghua University, Beijing 100084, China
- Beijing National Research Center for Information Science and Technology, Beijing 100084, China
| | - Cun-Zheng Ning
- Department of Electronic Engineering, Tsinghua University, Beijing 100084, China
- Frontier Science Center for Quantum Information, Beijing 100084, China
- International Center for Nano-Optoelectronics, Tsinghua University, Beijing 100084, China
- Beijing National Research Center for Information Science and Technology, Beijing 100084, China
- School of Electrical, Computer, and Energy Engineering, Arizona State University, Tempe, Arizona 85287, United States
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26
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Qi P, Luo Y, Li W, Cheng Y, Shan H, Wang X, Liu Z, Ajayan PM, Lou J, Hou Y, Liu K, Fang Z. Remote Lightening and Ultrafast Transition: Intrinsic Modulation of Exciton Spatiotemporal Dynamics in Monolayer MoS 2. ACS NANO 2020; 14:6897-6905. [PMID: 32491833 DOI: 10.1021/acsnano.0c01165] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Devices operating with excitons have promising prospects for overcoming the dilemma of response time and integration in current generation of electron- or/and photon-based elements and devices. Although the intrinsic properties including edges, grain boundaries, and defects of atomically thin semiconductors have been demonstrated as a powerful tool to adjust the bandgap and exciton energy, investigating the intrinsic modulation of spatiotemporal dynamics still remains challenging on account of the short exciton diffusion length. Here, we achieve the attractive remote lightening phenomenon, in which the emission region could be far away (up to 14.6 μm) from the excitation center, by utilizing a femtosecond laser with ultrahigh peak power as excitation source and the edge region with high photoluminescence efficiency as a bright emitter. Furthermore, the ultrafast transition between exciton and trion is demonstrated, which provides insight into the intrinsic modulation on populations of exciton and trion states. The complete cascaded physical scenario of exciton spatiotemporal dynamics is eventually established. This work can refresh our perspective on the spatial nonuniformities of CVD-grown atomically thin semiconductors and provide important implications for developing durable and stable excitonic devices in the future.
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Affiliation(s)
- Pengfei Qi
- School of Physics, State Key Laboratory for Mesoscopic Physics, Academy for Advanced Interdisciplinary Studies, Collaborative Innovation Center of Quantum Matter, Nano-optoelectronics Frontier Center of Ministry of Education, Peking University, Beijing 100871, China
| | - Yang Luo
- School of Physics, State Key Laboratory for Mesoscopic Physics, Academy for Advanced Interdisciplinary Studies, Collaborative Innovation Center of Quantum Matter, Nano-optoelectronics Frontier Center of Ministry of Education, Peking University, Beijing 100871, China
| | - Wei Li
- Beijing Key Laboratory for Magnetoelectric Materials and Devices, Beijing Innovation Centre for Engineering Science and Advanced Technology, Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871, China
| | - Yang Cheng
- School of Physics, State Key Laboratory for Mesoscopic Physics, Academy for Advanced Interdisciplinary Studies, Collaborative Innovation Center of Quantum Matter, Nano-optoelectronics Frontier Center of Ministry of Education, Peking University, Beijing 100871, China
| | - Hangyong Shan
- School of Physics, State Key Laboratory for Mesoscopic Physics, Academy for Advanced Interdisciplinary Studies, Collaborative Innovation Center of Quantum Matter, Nano-optoelectronics Frontier Center of Ministry of Education, Peking University, Beijing 100871, China
| | - Xingli Wang
- CNRS International-NTU-Thales Research Alliance (CINTRA), Nanyang Technological University, Singapore 637553, Singapore
| | - Zheng Liu
- CNRS International-NTU-Thales Research Alliance (CINTRA), Nanyang Technological University, Singapore 637553, Singapore
| | - Pulickel M Ajayan
- Department of Materials Science and NanoEngineering, Rice University, Houston, Texas 77005, United States
| | - Jun Lou
- Department of Materials Science and NanoEngineering, Rice University, Houston, Texas 77005, United States
| | - Yanglong Hou
- Beijing Key Laboratory for Magnetoelectric Materials and Devices, Beijing Innovation Centre for Engineering Science and Advanced Technology, Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871, China
| | - Kaihui Liu
- School of Physics, State Key Laboratory for Mesoscopic Physics, Academy for Advanced Interdisciplinary Studies, Collaborative Innovation Center of Quantum Matter, Nano-optoelectronics Frontier Center of Ministry of Education, Peking University, Beijing 100871, China
| | - Zheyu Fang
- School of Physics, State Key Laboratory for Mesoscopic Physics, Academy for Advanced Interdisciplinary Studies, Collaborative Innovation Center of Quantum Matter, Nano-optoelectronics Frontier Center of Ministry of Education, Peking University, Beijing 100871, China
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27
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Glazov MM. Quantum Interference Effect on Exciton Transport in Monolayer Semiconductors. PHYSICAL REVIEW LETTERS 2020; 124:166802. [PMID: 32383933 DOI: 10.1103/physrevlett.124.166802] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2019] [Accepted: 04/01/2020] [Indexed: 06/11/2023]
Abstract
We study theoretically weak localization of excitons in atomically thin transition metal dichalcogenides. The constructive interference of excitonic de Broglie waves on the trajectories forming closed loops results in a decrease of the exciton diffusion coefficient. We calculate the interference contribution to the diffusion coefficient for the experimentally relevant situation of exciton scattering by acoustic phonons and static disorder. For the acoustic phonon scattering, the quantum interference becomes more and more important with increasing the temperature. Our estimates show that the quantum contribution to the diffusion coefficient is considerable for the state-of-the-art monolayer and bilayer transition metal dichalcogenides.
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Affiliation(s)
- M M Glazov
- Ioffe Institute, 194021 St. Petersburg, Russia
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28
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Rosati R, Perea-Causín R, Brem S, Malic E. Negative effective excitonic diffusion in monolayer transition metal dichalcogenides. NANOSCALE 2020; 12:356-363. [PMID: 31825433 DOI: 10.1039/c9nr07056g] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
While exciton relaxation in monolayers of transition metal dichalcogenides (TMDs) has been intensively studied, spatial exciton diffusion has received only a little attention - in spite of being a key process for optoelectronics and having already shown interesting unconventional behaviours (e.g. spatial halos). Here, we study the spatiotemporal dynamics in TMD monolayers and track optically excited excitons in time, momentum, and space. In particular, we investigate the temperature-dependent exciton diffusion including the remarkable exciton landscape constituted by bright and dark states. Based on a fully quantum mechanical approach, we show at low temperatures an unexpected negative effective diffusion characterized by a shrinking of the spatial exciton distributions. This phenomenon can be traced back to the existence of dark exciton states in TMD monolayers and is a result of an interplay between spatial exciton diffusion and intervalley exciton-phonon scattering.
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Affiliation(s)
- Roberto Rosati
- Chalmers University of Technology, Department of Physics, 412 96 Gothenburg, Sweden.
| | - Raül Perea-Causín
- Chalmers University of Technology, Department of Physics, 412 96 Gothenburg, Sweden.
| | - Samuel Brem
- Chalmers University of Technology, Department of Physics, 412 96 Gothenburg, Sweden.
| | - Ermin Malic
- Chalmers University of Technology, Department of Physics, 412 96 Gothenburg, Sweden.
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29
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Liu H, Wang C, Zuo Z, Liu D, Luo J. Direct Visualization of Exciton Transport in Defective Few-Layer WS 2 by Ultrafast Microscopy. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2020; 32:e1906540. [PMID: 31773833 DOI: 10.1002/adma.201906540] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2019] [Revised: 11/03/2019] [Indexed: 06/10/2023]
Abstract
As defects usually limit the exciton diffusion in 2D transition metal dichalcogenides (TMDCs), the interaction knowledge of defects and exciton transport is crucial for achieving efficient TMDC-based devices. A direct visualization of defect-modulated exciton transport is developed in few-layer WS2 by ultrafast transient absorption microscopy. Atomic-scale defects are introduced by argon plasma treatment and identified by aberration-corrected scanning transmission electron microscopy. Neutral excitons can be captured by defects to form bound excitons in 7.75-17.88 ps, which provide a nonradiative relaxation channel, leading to decreased exciton lifetime and diffusion coefficient. The exciton diffusion length of defective sample has a drastic reduction from 349.44 to 107.40 nm. These spatially and temporally resolved measurements reveal the interaction mechanism between defects and exciton transport dynamics in 2D TMDCs, giving a guideline for designing high-performance TMDC-based devices.
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Affiliation(s)
- Huan Liu
- State Key Laboratory of Tribology, Tsinghua University, Beijing, 100084, P. R. China
| | - Chong Wang
- State Key Laboratory of Tribology, Tsinghua University, Beijing, 100084, P. R. China
| | - Zhengguang Zuo
- State Key Laboratory of Tribology, Tsinghua University, Beijing, 100084, P. R. China
| | - Dameng Liu
- State Key Laboratory of Tribology, Tsinghua University, Beijing, 100084, P. R. China
| | - Jianbin Luo
- State Key Laboratory of Tribology, Tsinghua University, Beijing, 100084, P. R. China
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30
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Liu Y, Hu X, Wang T, Liu D. Reduced Binding Energy and Layer-Dependent Exciton Dynamics in Monolayer and Multilayer WS 2. ACS NANO 2019; 13:14416-14425. [PMID: 31825594 DOI: 10.1021/acsnano.9b08004] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The exciton dynamics in WS2 from monolayer to four-layer was investigated by using fluorescence lifetime imaging measurement (FLIM). The transition process of negatively charged trions is measured and detected using a fluorescence detection method. Compared with neutral excitons, negatively charged trions have a longer fluorescence lifetime. Further exploration illustrated that the fluorescence lifetime of both neutral excitons and trions get longer when the thickness increased. When WS2 was added from monolayer to four-layer, lifetimes of direct transition excitons and trions tended to increase over 10 and 2.5 times, separately, whereas the lifetime of indirect transition excitons tended to be reduced by nearly 2.5 times. This layer-dependent signature is ascribed to the reduced binding energy in thicker WS2 at room temperature, which is verified by density theory functional calculation. Although the direct transition exciton dominates the whole fluorescence decay process, it is influenced by trions and dark excitons. Based on the FLIM results, we proposed four main exciton transition channels during the fluorescence luminescence process. Such layer-dependent transition channel conception helps to control the fluorescence lifetime, which determines the efficiency of the carriers' separation.
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Affiliation(s)
- Yuanshuang Liu
- State Key Laboratory of Tribology , Tsinghua University , Beijing 100084 , China
| | - Xiangmin Hu
- State Key Laboratory of Tribology , Tsinghua University , Beijing 100084 , China
| | - Ting Wang
- State Key Laboratory of Tribology , Tsinghua University , Beijing 100084 , China
| | - Dameng Liu
- State Key Laboratory of Tribology , Tsinghua University , Beijing 100084 , China
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31
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Ginsberg NS, Tisdale WA. Spatially Resolved Photogenerated Exciton and Charge Transport in Emerging Semiconductors. Annu Rev Phys Chem 2019; 71:1-30. [PMID: 31756129 DOI: 10.1146/annurev-physchem-052516-050703] [Citation(s) in RCA: 60] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
We review recent advances in the characterization of electronic forms of energy transport in emerging semiconductors. The approaches described all temporally and spatially resolve the evolution of initially localized populations of photogenerated excitons or charge carriers. We first provide a comprehensive background for describing the physical origin and nature of electronic energy transport both microscopically and from the perspective of the observer. We introduce the new family of far-field, time-resolved optical microscopies developed to directly resolve not only the extent of this transport but also its potentially temporally and spatially dependent rate. We review a representation of examples from the recent literature, including investigation of energy flow in colloidal quantum dot solids, organic semiconductors, organic-inorganic metal halide perovskites, and 2D transition metal dichalcogenides. These examples illustrate how traditional parameters like diffusivity are applicable only within limited spatiotemporal ranges and how the techniques at the core of this review,especially when taken together, are revealing a more complete picture of the spatiotemporal evolution of energy transport in complex semiconductors, even as a function of their structural heterogeneities.
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Affiliation(s)
- Naomi S Ginsberg
- Department of Chemistry and Department of Physics, University of California, Berkeley, California 94720, USA; .,Material Sciences Division and Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.,Kavli Energy NanoSciences Institute, Berkeley, California 94720, USA
| | - William A Tisdale
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA;
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32
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Perea-Causín R, Brem S, Rosati R, Jago R, Kulig M, Ziegler JD, Zipfel J, Chernikov A, Malic E. Exciton Propagation and Halo Formation in Two-Dimensional Materials. NANO LETTERS 2019; 19:7317-7323. [PMID: 31532993 DOI: 10.1021/acs.nanolett.9b02948] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The interplay of optics, dynamics, and transport is crucial for the design of novel optoelectronic devices, such as photodetectors and solar cells. In this context, transition-metal dichalcogenides (TMDs) have received much attention. Here, strongly bound excitons dominate optical excitation, carrier dynamics, and diffusion processes. While the first two have been intensively studied, there is a lack of fundamental understanding of nonequilibrium phenomena associated with exciton transport that is of central importance (e.g., for high-efficiency light harvesting). In this work, we provide microscopic insights into the interplay of exciton propagation and many-particle interactions in TMDs. On the basis of a fully quantum mechanical approach and in excellent agreement with photoluminescence measurements, we show that Auger recombination and emission of hot phonons act as a heating mechanism giving rise to strong spatial gradients in excitonic temperature. The resulting thermal drift leads to an unconventional exciton diffusion characterized by spatial exciton halos.
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Affiliation(s)
- Raül Perea-Causín
- Department of Physics , Chalmers University of Technology , 412 96 Gothenburg , Sweden
| | - Samuel Brem
- Department of Physics , Chalmers University of Technology , 412 96 Gothenburg , Sweden
| | - Roberto Rosati
- Department of Physics , Chalmers University of Technology , 412 96 Gothenburg , Sweden
| | - Roland Jago
- Department of Physics , Chalmers University of Technology , 412 96 Gothenburg , Sweden
| | - Marvin Kulig
- Department of Physics , University of Regensburg , Regensburg D-93053 , Germany
| | - Jonas D Ziegler
- Department of Physics , University of Regensburg , Regensburg D-93053 , Germany
| | - Jonas Zipfel
- Department of Physics , University of Regensburg , Regensburg D-93053 , Germany
| | - Alexey Chernikov
- Department of Physics , University of Regensburg , Regensburg D-93053 , Germany
| | - Ermin Malic
- Department of Physics , Chalmers University of Technology , 412 96 Gothenburg , Sweden
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33
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He Z, Han Z, Yuan J, Sinyukov AM, Eleuch H, Niu C, Zhang Z, Lou J, Hu J, Voronine DV, Scully MO. Quantum plasmonic control of trions in a picocavity with monolayer WS 2. SCIENCE ADVANCES 2019; 5:eaau8763. [PMID: 31646171 PMCID: PMC6788863 DOI: 10.1126/sciadv.aau8763] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Accepted: 09/14/2019] [Indexed: 05/30/2023]
Abstract
Monitoring and controlling the neutral and charged excitons (trions) in two-dimensional (2D) materials are essential for the development of high-performance devices. However, nanoscale control is challenging because of diffraction-limited spatial resolution of conventional far-field techniques. Here, we extend the classical tip-enhanced photoluminescence based on tip-substrate nanocavity to quantum regime and demonstrate controlled nano-optical imaging, namely, tip-enhanced quantum plasmonics. In addition to improving the spatial resolution, we use the scanning probe to control the optoelectronic response of monolayer WS2 by varying the neutral/charged exciton ratio via charge tunneling in Au-Ag picocavity. We observe trion "hot spots" generated by varying the picometer-scale probe-sample distance and show the effects of weak and strong coupling, which depend on the spatial location. Our experimental results are in agreement with simulations and open an unprecedented view of a new range of quantum plasmonic phenomena with 2D materials that will help to design new quantum optoelectronic devices.
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Affiliation(s)
- Zhe He
- Institute for Quantum Science and Engineering, Texas A&M University, College Station, TX 77843, USA
| | - Zehua Han
- Institute for Quantum Science and Engineering, Texas A&M University, College Station, TX 77843, USA
| | - Jiangtan Yuan
- Department of Materials Science and NanoEngineering, Rice University, Houston, TX 77005, USA
| | - Alexander M. Sinyukov
- Institute for Quantum Science and Engineering, Texas A&M University, College Station, TX 77843, USA
| | - Hichem Eleuch
- Institute for Quantum Science and Engineering, Texas A&M University, College Station, TX 77843, USA
- Department of Applied Sciences and Mathematics, College of Arts and Sciences, Abu Dhabi University, Abu Dhabi, United Arab Emirates
| | - Chao Niu
- Baylor Research and Innovation Collaborative, Baylor University, Waco, TX 76798, USA
- Department of Electrical and Computer Engineering, Baylor University, Waco, TX 76798, USA
| | - Zhenrong Zhang
- Baylor Research and Innovation Collaborative, Baylor University, Waco, TX 76798, USA
- Department of Physics, Baylor University, Waco, TX 76798, USA
| | - Jun Lou
- Department of Materials Science and NanoEngineering, Rice University, Houston, TX 77005, USA
| | - Jonathan Hu
- Baylor Research and Innovation Collaborative, Baylor University, Waco, TX 76798, USA
- Department of Electrical and Computer Engineering, Baylor University, Waco, TX 76798, USA
| | - Dmitri V. Voronine
- Department of Physics, University of South Florida, Tampa, FL 33620, USA
| | - Marlan O. Scully
- Institute for Quantum Science and Engineering, Texas A&M University, College Station, TX 77843, USA
- Baylor Research and Innovation Collaborative, Baylor University, Waco, TX 76798, USA
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34
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Pommier D, Bretel R, López LEP, Fabre F, Mayne A, Boer-Duchemin E, Dujardin G, Schull G, Berciaud S, Le Moal E. Scanning Tunneling Microscope-Induced Excitonic Luminescence of a Two-Dimensional Semiconductor. PHYSICAL REVIEW LETTERS 2019; 123:027402. [PMID: 31386496 DOI: 10.1103/physrevlett.123.027402] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2018] [Indexed: 05/24/2023]
Abstract
The long sought-after goal of locally and spectroscopically probing the excitons of two-dimensional (2D) semiconductors is attained using a scanning tunneling microscope (STM). Excitonic luminescence from monolayer molybdenum diselenide (MoSe_{2}) on a transparent conducting substrate is electrically excited in the tunnel junction of an STM under ambient conditions. By comparing the results with photoluminescence measurements, the emission mechanism is identified as the radiative recombination of bright A excitons. STM-induced luminescence is observed at bias voltages as low as those that correspond to the energy of the optical band gap of MoSe_{2}. The proposed excitation mechanism is resonance energy transfer from the tunneling current to the excitons in the semiconductor, i.e., through virtual photon coupling. Additional mechanisms (e.g., charge injection) may come into play at bias voltages that are higher than the electronic band gap. Photon emission quantum efficiencies of up to 10^{-7} photons per electron are obtained, despite the lack of any participating plasmons. Our results demonstrate a new technique for investigating the excitonic and optoelectronic properties of 2D semiconductors and their heterostructures at the nanometer scale.
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Affiliation(s)
- Delphine Pommier
- Institut des Sciences Moléculaires d'Orsay, CNRS, Université Paris Sud, Université Paris-Saclay, F-91405 Orsay, France
| | - Rémi Bretel
- Institut des Sciences Moléculaires d'Orsay, CNRS, Université Paris Sud, Université Paris-Saclay, F-91405 Orsay, France
| | - Luis E Parra López
- Institut de Physique et Chimie des Matériaux de Strasbourg, Université de Strasbourg, CNRS, IPCMS, UMR 7504, F-67000 Strasbourg, France
| | - Florentin Fabre
- Institut de Physique et Chimie des Matériaux de Strasbourg, Université de Strasbourg, CNRS, IPCMS, UMR 7504, F-67000 Strasbourg, France
| | - Andrew Mayne
- Institut des Sciences Moléculaires d'Orsay, CNRS, Université Paris Sud, Université Paris-Saclay, F-91405 Orsay, France
| | - Elizabeth Boer-Duchemin
- Institut des Sciences Moléculaires d'Orsay, CNRS, Université Paris Sud, Université Paris-Saclay, F-91405 Orsay, France
| | - Gérald Dujardin
- Institut des Sciences Moléculaires d'Orsay, CNRS, Université Paris Sud, Université Paris-Saclay, F-91405 Orsay, France
| | - Guillaume Schull
- Institut de Physique et Chimie des Matériaux de Strasbourg, Université de Strasbourg, CNRS, IPCMS, UMR 7504, F-67000 Strasbourg, France
| | - Stéphane Berciaud
- Institut de Physique et Chimie des Matériaux de Strasbourg, Université de Strasbourg, CNRS, IPCMS, UMR 7504, F-67000 Strasbourg, France
| | - Eric Le Moal
- Institut des Sciences Moléculaires d'Orsay, CNRS, Université Paris Sud, Université Paris-Saclay, F-91405 Orsay, France
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35
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Kojima K, Lim HE, Liu Z, Zhang W, Saito T, Nakanishi Y, Endo T, Kobayashi Y, Watanabe K, Taniguchi T, Matsuda K, Maniwa Y, Miyauchi Y, Miyata Y. Restoring the intrinsic optical properties of CVD-grown MoS 2 monolayers and their heterostructures. NANOSCALE 2019; 11:12798-12803. [PMID: 31173037 DOI: 10.1039/c9nr01481k] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
This study investigated the intrinsic optical properties of MoS2 monolayers and MoS2/WS2 van der Waals (vdW) heterostructures, grown using chemical vapor deposition. To understand the effect of the growth substrate, samples grown on a SiO2/Si surface were transferred and suspended onto a porous substrate. This transfer resulted in a blue shift of the excitonic photoluminescence (PL) peak generated by MoS2 monolayers, together with an intensity increase. The blue shift and the intensity increase are attributed to the release of lattice strain and the elimination of substrate-induced non-radiative relaxation, respectively. This suspension technique also allowed the observation of PL resulting from interlayer excitons in the MoS2/WS2 vdW heterostructures. These results indicate that the suppression of lattice strain and non-radiative relaxation is essential for the formation of interlayer excitons, which in turn is crucial for understanding the intrinsic physical properties of vdW heterostructures.
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Affiliation(s)
- Kana Kojima
- Department of Physics, Tokyo Metropolitan University, Hachioji, 192-0397, Japan.
| | - Hong En Lim
- Department of Physics, Tokyo Metropolitan University, Hachioji, 192-0397, Japan.
| | - Zheng Liu
- Inorganic Functional Materials Research Institute, AIST, Nagoya, 463-8560, Japan
| | - Wenjin Zhang
- Institute of Advanced Energy, Kyoto University, Uji, 611-0011, Japan
| | - Tetsuki Saito
- Department of Physics, Tokyo Metropolitan University, Hachioji, 192-0397, Japan.
| | - Yusuke Nakanishi
- Department of Physics, Tokyo Metropolitan University, Hachioji, 192-0397, Japan.
| | - Takahiko Endo
- Department of Physics, Tokyo Metropolitan University, Hachioji, 192-0397, Japan.
| | - Yu Kobayashi
- Department of Physics, Tokyo Metropolitan University, Hachioji, 192-0397, Japan.
| | - Kenji Watanabe
- National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Takashi Taniguchi
- National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Kazunari Matsuda
- Institute of Advanced Energy, Kyoto University, Uji, 611-0011, Japan
| | - Yutaka Maniwa
- Department of Physics, Tokyo Metropolitan University, Hachioji, 192-0397, Japan.
| | - Yuhei Miyauchi
- Institute of Advanced Energy, Kyoto University, Uji, 611-0011, Japan
| | - Yasumitsu Miyata
- Department of Physics, Tokyo Metropolitan University, Hachioji, 192-0397, Japan.
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36
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Zhang Q, Ji Y, Chen Z, Vella D, Wang X, Xu QH, Li Y, Eda G. Controlled Aqueous Synthesis of 2D Hybrid Perovskites with Bright Room-Temperature Long-Lived Luminescence. J Phys Chem Lett 2019; 10:2869-2873. [PMID: 31088074 DOI: 10.1021/acs.jpclett.9b00934] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Recently, some organic-inorganic hybrid perovskites (OIHPs) have been reported to exhibit strong subgap broadband luminescence. While the origin of such luminescence has been proposed by several groups, a strategy to prepare OIHP with the desired subgap emission properties has remained elusive. Here, we report controlled synthesis of a broadband-emitting single-crystal 2D OIHP with an average quantum yield of >80 %. We demonstrate that the intensity of broadband emission can be tuned by controlling the excess iodine ion concentration during the synthesis in hydroiodic acid. We show that the emitters exhibit characteristics of localized defects such as limited mobility and saturation at high excitation power. Using density functional theory calculations, we show that bond-state iodine interstitials are responsible for the observed long-lived luminescence.
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Affiliation(s)
- Qi Zhang
- Department of Physics , National University of Singapore , 2 Science Drive 3 , Singapore 117542
| | - Yujin Ji
- Institute of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices , Soochow University , Suzhou , Jiangsu 215123 , China
| | - Zhihui Chen
- Department of Chemistry , National University of Singapore , 3 Science Drive 3 , Singapore 117543
| | - Daniele Vella
- Department of Physics , National University of Singapore , 2 Science Drive 3 , Singapore 117542
- Centre for Advanced 2D Materials , National University of Singapore , 6 Science Drive 2 , Singapore 117546
| | - Xinyun Wang
- Department of Physics , National University of Singapore , 2 Science Drive 3 , Singapore 117542
- Centre for Advanced 2D Materials , National University of Singapore , 6 Science Drive 2 , Singapore 117546
| | - Qing-Hua Xu
- Department of Chemistry , National University of Singapore , 3 Science Drive 3 , Singapore 117543
| | - Youyong Li
- Institute of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices , Soochow University , Suzhou , Jiangsu 215123 , China
| | - Goki Eda
- Department of Physics , National University of Singapore , 2 Science Drive 3 , Singapore 117542
- Centre for Advanced 2D Materials , National University of Singapore , 6 Science Drive 2 , Singapore 117546
- Department of Chemistry , National University of Singapore , 3 Science Drive 3 , Singapore 117543
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37
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Jago R, Perea-Causin R, Brem S, Malic E. Spatio-temporal dynamics in graphene. NANOSCALE 2019; 11:10017-10022. [PMID: 31080988 DOI: 10.1039/c9nr01714c] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Temporally and spectrally resolved dynamics of optically excited carriers in graphene has been intensively studied theoretically and experimentally, whereas carrier diffusion in space has attracted much less attention. Understanding the spatio-temporal carrier dynamics is of key importance for optoelectronic applications, where carrier transport phenomena play an important role. In this work, we provide a microscopic access to the time-, momentum-, and space-resolved dynamics of carriers in graphene. We determine the diffusion coefficient to be D≈ 360 cm2 s-1 and reveal the impact of carrier-phonon and carrier-carrier scattering on the diffusion process. In particular, we show that phonon-induced scattering across the Dirac cone gives rise to back-diffusion counteracting the spatial broadening of the carrier distribution.
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Affiliation(s)
- Roland Jago
- Chalmers University of Technology, Department of Physics, SE-412 96 Gothenburg, Sweden.
| | - Raül Perea-Causin
- Chalmers University of Technology, Department of Physics, SE-412 96 Gothenburg, Sweden.
| | - Samuel Brem
- Chalmers University of Technology, Department of Physics, SE-412 96 Gothenburg, Sweden.
| | - Ermin Malic
- Chalmers University of Technology, Department of Physics, SE-412 96 Gothenburg, Sweden.
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38
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Pei J, Yang J, Yildirim T, Zhang H, Lu Y. Many-Body Complexes in 2D Semiconductors. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2019; 31:e1706945. [PMID: 30129218 DOI: 10.1002/adma.201706945] [Citation(s) in RCA: 101] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Revised: 06/10/2018] [Indexed: 05/25/2023]
Abstract
2D semiconductors such as transition metal dichalcogenides (TMDs) and black phosphorus (BP) are currently attracting great attention due to their intrinsic bandgaps and strong excitonic emissions, making them potential candidates for novel optoelectronic applications. Optoelectronic devices fabricated from 2D semiconductors exhibit many-body complexes (exciton, trion, biexciton, etc.) which determine the materials optical and electrical properties. Characterization and manipulation of these complexes have become a reality due to their enhanced binding energies as a direct result from reduced dielectric screening and enhanced Coulomb interactions in the 2D regime. Furthermore, the atomic thickness and extremely large surface-to-volume ratio of 2D semiconductors allow the possibility of modulating their inherent optical, electrical, and optoelectronic properties using a variety of different environmental stimuli. To fully realize the potential functionalities of these many-body complexes in optoelectronics, a comprehensive understanding of their formation mechanism is essential. A topical and concise summary of the recent frontier research progress related to many-body complexes in 2D semiconductors is provided here. Moreover, detailed discussions covering the aspects of fundamental theory, experimental investigations, modulation of properties, and optoelectronic applications are given. Lastly, personal insights into the current challenges and future outlook of many-body complexes in 2D semiconducting materials are presented.
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Affiliation(s)
- Jiajie Pei
- Collaborative Innovation Center for Optoelectronic Science and Technology, Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen, 518060, P. R. China
| | - Jiong Yang
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen, 518060, P. R. China
- Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen, 518060, P. R. China
| | - Tanju Yildirim
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen, 518060, P. R. China
- Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen, 518060, P. R. China
| | - Han Zhang
- Collaborative Innovation Center for Optoelectronic Science and Technology, Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen, 518060, P. R. China
| | - Yuerui Lu
- Research School of Engineering, The Australian National University, Canberra, ACT 2601, Australia
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39
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Kaviraj B, Sahoo D. Physics of excitons and their transport in two dimensional transition metal dichalcogenide semiconductors. RSC Adv 2019; 9:25439-25461. [PMID: 35530097 PMCID: PMC9070122 DOI: 10.1039/c9ra03769a] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2019] [Accepted: 07/17/2019] [Indexed: 11/21/2022] Open
Abstract
Two-dimensional (2D) group-VI transition metal dichalcogenide (TMD) semiconductors, such as MoS2, MoSe2, WS2 and others manifest strong light matter coupling and exhibit direct band gaps which lie in the visible and infrared spectral regimes. These properties make them potentially interesting candidates for applications in optics and optoelectronics. The excitons found in these materials are tightly bound and dominate the optical response, even at room temperatures. Large binding energies and unique exciton fine structure make these materials an ideal platform to study exciton behaviors in two-dimensional systems. This review article mainly focuses on studies of mechanisms that control dynamics of excitons in 2D systems – an area where there remains a lack of consensus in spite of extensive research. Firstly, we focus on the kinetics of dark and bright excitons based on a rate equation model and discuss on the role of previous ‘unsuspected’ dark excitons in controlling valley polarization. Intrinsically, dark and bright exciton energy splitting plays a key role in modulating the dynamics. In the second part, we review the excitation energy-dependent possible characteristic relaxation pathways of photoexcited carriers in monolayer and bilayer systems. In the third part, we review the extrinsic factors, in particular the defects that are so prevalent in single layer TMDs, affecting exciton dynamics, transport and non-radiative recombination such as exciton–exciton annihilation. Lastly, the optical response due to pump-induced changes in TMD monolayers have been reviewed using femtosecond pump–probe spectroscopy which facilitates the analysis of underlying physical process just after the excitation. Two-dimensional (2D) group-VI transition metal dichalcogenide (TMD) semiconductors, such as MoS2, MoSe2, WS2 and others manifest strong light matter coupling and exhibit direct band gaps which lie in the visible and infrared spectral regimes.![]()
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Affiliation(s)
- Bhaskar Kaviraj
- Department of Physics
- School of Natural Sciences
- Shiv Nadar University
- Greater Noida
- India
| | - Dhirendra Sahoo
- Department of Physics
- School of Natural Sciences
- Shiv Nadar University
- Greater Noida
- India
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40
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Debbarma R, Behura SK, Wen Y, Che S, Berry V. WS 2-induced enhanced optical absorption and efficiency in graphene/silicon heterojunction photovoltaic cells. NANOSCALE 2018; 10:20218-20225. [PMID: 30357212 DOI: 10.1039/c8nr03194k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Van Hove singularity (VHS) induced enhancement of visible-frequency absorption in atomically-thin two-dimensional (2D) crystals provides an opportunity for improved light management in photovoltaics; however, it requires the 2D nanomaterial to be in close vicinity of a photojunction. In this report, we design a Schottky junction-based photovoltaic system with single-layer graphene atop n-type silicon (n-Si), which is interfaced directly with a few layers of tungsten disulfide (WS2) via a bottom-up CVD synthesis strategy. An enhanced power conversion efficiency in the architecture of WS2-graphene/n-Si is observed compared to graphene/n-Si. Here, the WS2 induced photon absorption, with only three atoms above the photo-junction, enhanced the short-circuit current density (Jsc), and the reconfiguration of the energy band structure led to effective built-in electric field induced charge carrier transport (enhanced open-circuit voltage (Voc)). Similar to a graphene/n-Si Schottky junction, the WS2-graphene/n-Si double junction exhibited non-linear current density-voltage (J-V) characteristics with a 4-fold increase in Jsc (2.28 mA cm-2 in comparison with 0.52 mA cm-2 for graphene/n-Si) and 40% increase in the Voc (184 mV compared to 130 mV for graphene/n-Si) with a 6-fold increase in the photovoltaic power conversion efficiency. Futuristically, we envision an evolution in 2D heterojunctions with sharp transitions in properties within a few nanometers enabling control on optical absorption, carrier distribution, and band structure for applications including tandem photovoltaic cells and 2D optoelectronic circuit-switches.
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Affiliation(s)
- Rousan Debbarma
- Department of Chemical Engineering, University of Illinois at Chicago, 810 S. Clinton Street, Chicago, IL 60607, USA.
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41
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Yin X, Tang CS, Majidi MA, Ren P, Wang L, Yang P, Diao C, Yu X, Breese MBH, Wee ATS, Wang J, Rusydi A. Modulation of Manganite Nanofilm Properties Mediated by Strong Influence of Strontium Titanate Excitons. ACS APPLIED MATERIALS & INTERFACES 2018; 10:35563-35570. [PMID: 29210262 DOI: 10.1021/acsami.7b15347] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Hole-doped perovskite manganites have attracted much attention because of their unique optical, electronic, and magnetic properties induced by the interplay between spin, charge, orbital, and lattice degrees of freedom. Here, a comprehensive investigation of the optical, electronic, and magnetic properties of La0.7Sr0.3MnO3 thin films on SrTiO3 (LSMO/STO) and other substrates is conducted using a combination of temperature-dependent transport, spectroscopic ellipsometry, X-ray absorption spectroscopy, and X-ray magnetic circular dichroism. A significant difference in the optical property of LSMO/STO that occurs even in thick (87.2 nm) LSMO/STO from that of LSMO on other substrates is discovered. Several excitonic features are observed in thin film nanostructure LSMO/STO at ∼4 eV, which could be attributed to the formation of anomalous charged excitonic complexes. On the basis of the spectral weight transfer analysis, anomalous excitonic effects from STO strengthen the electronic correlation in LSMO films. This results in the occurrence of optical spectral changes related to the intrinsic Mott-Hubbard properties in manganites. We find that while lattice strain from the substrate influences the optical properties of the LSMO thin films, the coexistence of strong electron-electron (e-e) and electron-hole (e-h) interactions which leads to the resonant excitonic effects from the substrate plays a much more significant role. Our result shows that the onset of anomalous excitonic dynamics in manganite oxides may potentially generate new approaches in manipulating exciton-based optoelectronic applications.
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Affiliation(s)
- Xinmao Yin
- Singapore Synchrotron Light Source (SSLS) , National University of Singapore , 5 Research Link , 117603 , Singapore
- SZU-NUS Collaborative Innovation Center for Optoelectronic Science & Technology, Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering , Shenzhen University , Shenzhen 518060 , China
- Department of Physics, Faculty of Science , National University of Singapore , 117542 , Singapore
| | - Chi Sin Tang
- Singapore Synchrotron Light Source (SSLS) , National University of Singapore , 5 Research Link , 117603 , Singapore
- Department of Physics, Faculty of Science , National University of Singapore , 117542 , Singapore
- NUS Graduate School for Integrative Sciences and Engineering , 117456 , Singapore
| | - Muhammad Aziz Majidi
- Singapore Synchrotron Light Source (SSLS) , National University of Singapore , 5 Research Link , 117603 , Singapore
- Department of Physics, Faculty of Science , National University of Singapore , 117542 , Singapore
- Departemen Fisika, FMIPA , Universitas Indonesia , Depok 16424 , Indonesia
| | - Peng Ren
- School of Materials Science and Engineering , Nanyang Technological University , 639798 , Singapore
| | - Le Wang
- School of Materials Science and Engineering , Nanyang Technological University , 639798 , Singapore
| | - Ping Yang
- Singapore Synchrotron Light Source (SSLS) , National University of Singapore , 5 Research Link , 117603 , Singapore
| | - Caozheng Diao
- Singapore Synchrotron Light Source (SSLS) , National University of Singapore , 5 Research Link , 117603 , Singapore
| | - Xiaojiang Yu
- Singapore Synchrotron Light Source (SSLS) , National University of Singapore , 5 Research Link , 117603 , Singapore
| | - Mark B H Breese
- Singapore Synchrotron Light Source (SSLS) , National University of Singapore , 5 Research Link , 117603 , Singapore
- Department of Physics, Faculty of Science , National University of Singapore , 117542 , Singapore
| | - Andrew T S Wee
- Department of Physics, Faculty of Science , National University of Singapore , 117542 , Singapore
- NUS Graduate School for Integrative Sciences and Engineering , 117456 , Singapore
- Centre for Advanced 2D Materials and Graphene Research Centre , National University of Singapore , 117551 , Singapore
| | - Junling Wang
- School of Materials Science and Engineering , Nanyang Technological University , 639798 , Singapore
| | - Andrivo Rusydi
- Singapore Synchrotron Light Source (SSLS) , National University of Singapore , 5 Research Link , 117603 , Singapore
- NUSNNI-NanoCore , National University of Singapore , 117411 , Singapore
- Department of Physics, Faculty of Science , National University of Singapore , 117542 , Singapore
- NUS Graduate School for Integrative Sciences and Engineering , 117456 , Singapore
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42
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Kulig M, Zipfel J, Nagler P, Blanter S, Schüller C, Korn T, Paradiso N, Glazov MM, Chernikov A. Exciton Diffusion and Halo Effects in Monolayer Semiconductors. PHYSICAL REVIEW LETTERS 2018; 120:207401. [PMID: 29864294 DOI: 10.1103/physrevlett.120.207401] [Citation(s) in RCA: 100] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2017] [Revised: 01/12/2018] [Indexed: 05/28/2023]
Abstract
We directly monitor exciton propagation in freestanding and SiO_{2}-supported WS_{2} monolayers through spatially and time-resolved microphotoluminescence under ambient conditions. We find a highly nonlinear behavior with characteristic, qualitative changes in the spatial profiles of the exciton emission and an effective diffusion coefficient increasing from 0.3 to more than 30 cm^{2}/s, depending on the injected exciton density. Solving the diffusion equation while accounting for Auger recombination allows us to identify and quantitatively understand the main origin of the increase in the observed diffusion coefficient. At elevated excitation densities, the initial Gaussian distribution of the excitons evolves into long-lived halo shapes with μm-scale diameter, indicating additional memory effects in the exciton dynamics.
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Affiliation(s)
- Marvin Kulig
- Department of Physics, University of Regensburg, Regensburg D-93053, Germany
| | - Jonas Zipfel
- Department of Physics, University of Regensburg, Regensburg D-93053, Germany
| | - Philipp Nagler
- Department of Physics, University of Regensburg, Regensburg D-93053, Germany
| | - Sofia Blanter
- Department of Physics, University of Regensburg, Regensburg D-93053, Germany
| | - Christian Schüller
- Department of Physics, University of Regensburg, Regensburg D-93053, Germany
| | - Tobias Korn
- Department of Physics, University of Regensburg, Regensburg D-93053, Germany
| | - Nicola Paradiso
- Department of Physics, University of Regensburg, Regensburg D-93053, Germany
| | | | - Alexey Chernikov
- Department of Physics, University of Regensburg, Regensburg D-93053, Germany
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43
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Tan D, Wang X, Zhang W, Lim HE, Shinokita K, Miyauchi Y, Maruyama M, Okada S, Matsuda K. Carrier Transport and Photoresponse in GeSe/MoS 2 Heterojunction p-n Diodes. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2018; 14:e1704559. [PMID: 29700968 DOI: 10.1002/smll.201704559] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2017] [Revised: 02/26/2018] [Indexed: 06/08/2023]
Abstract
Simple stacking of thin van der Waals 2D materials with different physical properties enables one to create heterojunctions (HJs) with novel functionalities and new potential applications. Here, a 2D material p-n HJ of GeSe/MoS2 is fabricated and its vertical and horizontal carrier transport and photoresponse properties are studied. Substantial rectification with a very high contrast (>104 ) through the potential barrier in the vertical-direction tunneling of HJs is observed. The negative differential transconductance with high peak-to-valley ratio (>105 ) due to the series resistance change of GeSe, MoS2 , and HJs at different gate voltages is observed. Moreover, strong and broad-band photoresponse via the photoconductive effect are also demonstrated. The explored multifunctional properties of the GeSe/MoS2 HJs are expected to be important for understanding the carrier transport and photoresponse of 2D-material HJs for achieving their use in various new applications in the electronics and optoelectronics fields.
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Affiliation(s)
- Dezhi Tan
- Institute of Advanced Energy, Kyoto University, Uji, Kyoto, 611-0011, Japan
| | - Xiaofan Wang
- Institute of Advanced Energy, Kyoto University, Uji, Kyoto, 611-0011, Japan
| | - Wenjin Zhang
- Institute of Advanced Energy, Kyoto University, Uji, Kyoto, 611-0011, Japan
| | - Hong En Lim
- Institute of Advanced Energy, Kyoto University, Uji, Kyoto, 611-0011, Japan
| | - Keisuke Shinokita
- Institute of Advanced Energy, Kyoto University, Uji, Kyoto, 611-0011, Japan
| | - Yuhei Miyauchi
- Institute of Advanced Energy, Kyoto University, Uji, Kyoto, 611-0011, Japan
| | - Mina Maruyama
- Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8571, Japan
| | - Susumu Okada
- Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8571, Japan
| | - Kazunari Matsuda
- Institute of Advanced Energy, Kyoto University, Uji, Kyoto, 611-0011, Japan
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44
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Zhao P, Amani M, Lien DH, Ahn GH, Kiriya D, Mastandrea JP, Ager JW, Yablonovitch E, Chrzan DC, Javey A. Measuring the Edge Recombination Velocity of Monolayer Semiconductors. NANO LETTERS 2017; 17:5356-5360. [PMID: 28814079 DOI: 10.1021/acs.nanolett.7b01770] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Understanding edge effects and quantifying their impact on the carrier properties of two-dimensional (2D) semiconductors is an essential step toward utilizing this material for high performance electronic and optoelectronic devices. WS2 monolayers patterned into disks of varying diameters are used to experimentally explore the influence of edges on the material's optical properties. Carrier lifetime measurements show a decrease in the effective lifetime, τeffective, as a function of decreasing diameter, suggesting that the edges are active sites for carrier recombination. Accordingly, we introduce a metric called edge recombination velocity (ERV) to characterize the impact of 2D material edges on nonradiative carrier recombination. The unpassivated WS2 monolayer disks yield an ERV ∼ 4 × 104 cm/s. This work quantifies the nonradiative recombination edge effects in monolayer semiconductors, while simultaneously establishing a practical characterization approach that can be used to experimentally explore edge passivation methods for 2D materials.
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Affiliation(s)
- Peida Zhao
- Materials Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States
| | - Matin Amani
- Materials Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States
| | - Der-Hsien Lien
- Materials Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States
| | - Geun Ho Ahn
- Materials Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States
| | - Daisuke Kiriya
- Materials Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States
| | - James P Mastandrea
- Materials Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States
| | - Joel W Ager
- Materials Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States
| | - Eli Yablonovitch
- Materials Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States
| | - Daryl C Chrzan
- Materials Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States
| | - Ali Javey
- Materials Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States
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45
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Yuan L, Wang T, Zhu T, Zhou M, Huang L. Exciton Dynamics, Transport, and Annihilation in Atomically Thin Two-Dimensional Semiconductors. J Phys Chem Lett 2017; 8:3371-3379. [PMID: 28661147 DOI: 10.1021/acs.jpclett.7b00885] [Citation(s) in RCA: 75] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Large binding energy and unique exciton fine structure make the transition metal dichalcogenides (TMDCs) an ideal platform to study exciton behaviors in two-dimensional (2D) systems. While excitons in these systems have been extensively researched, there currently lacks a consensus on mechanisms that control dynamics. In this Perspective, we discuss extrinsic and intrinsic factors in exciton dynamics, transport, and annihilation in 2D TMDCs. Intrinsically, dark and bright exciton energy splitting is likely to play a key role in modulating the dynamics. Extrinsically, defect scattering is prevalent in single-layer TMDCs, which leads to rapid picosecond decay and limits exciton transport. The exciton-exciton annihilation process in single-layer TMDCs is highly efficient, playing an important role in the nonradiative recombination rate in the high exciton density regime. Future challenges and opportunities to control exciton dynamics are discussed.
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Affiliation(s)
- Long Yuan
- Department of Chemistry, Purdue University , West Lafayette, Indiana 47907, United States
| | - Ti Wang
- Department of Chemistry, Purdue University , West Lafayette, Indiana 47907, United States
| | - Tong Zhu
- Department of Chemistry, Purdue University , West Lafayette, Indiana 47907, United States
| | - Mingwei Zhou
- Department of Chemistry, Purdue University , West Lafayette, Indiana 47907, United States
| | - Libai Huang
- Department of Chemistry, Purdue University , West Lafayette, Indiana 47907, United States
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46
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Lee Y, Yun SJ, Kim Y, Kim MS, Han GH, Sood AK, Kim J. Near-field spectral mapping of individual exciton complexes of monolayer WS 2 correlated with local defects and charge population. NANOSCALE 2017; 9:2272-2278. [PMID: 28124703 DOI: 10.1039/c6nr08813a] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Exciton transitions are mostly responsible for the optical properties of transition metal dichalcogenide monolayers (1L-TMDs). Extensive studies of optical and structural characterization indicated that the presence of local structural defects and charge population critically influence the exciton emissions of 1L-TMDs. However, due to large variations of sample and experimental conditions, the exact mechanism of the exciton emission influenced by local structural defects and charge population is not clearly understood. In this work by using near-field scanning optical imaging and spectroscopy, we directly visualized spatially- and spectrally-resolved emission profiles of excitons, trions and defect bound excitons in CVD-grown monolayer tungsten disulfide (1L-WS2) with ∼70 nm spatial resolution. We found that exciton emission is spatially uniform while emission of trions and defect bound excitons was strongly modulated by the presence of structural features such as defects and wrinkles. We also visually observe a strong correlation between local charge accumulation and the trion formation upon increased photo-excitation.
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Affiliation(s)
- Yongjun Lee
- IBS Center for Integrated Nanostructure Physics, Institute for Basic Science, Suwon 440-746, Republic of Korea and Department of Energy Science, Sungkyunkwan University, Suwon 440-746, Republic of Korea.
| | - Seok Joon Yun
- IBS Center for Integrated Nanostructure Physics, Institute for Basic Science, Suwon 440-746, Republic of Korea and Department of Energy Science, Sungkyunkwan University, Suwon 440-746, Republic of Korea.
| | - Youngbum Kim
- IBS Center for Integrated Nanostructure Physics, Institute for Basic Science, Suwon 440-746, Republic of Korea and Department of Energy Science, Sungkyunkwan University, Suwon 440-746, Republic of Korea.
| | - Min Su Kim
- Department of Energy Science, Sungkyunkwan University, Suwon 440-746, Republic of Korea.
| | - Gang Hee Han
- Department of Energy Science, Sungkyunkwan University, Suwon 440-746, Republic of Korea.
| | - A K Sood
- Department of Physics, Indian Institute of Science, Bangalore-560012, India
| | - Jeongyong Kim
- IBS Center for Integrated Nanostructure Physics, Institute for Basic Science, Suwon 440-746, Republic of Korea and Department of Energy Science, Sungkyunkwan University, Suwon 440-746, Republic of Korea.
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