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Sousa FB, Nadas R, Martins R, Barboza APM, Soares JS, Neves BRA, Silvestre I, Jorio A, Malard LM. Disentangling doping and strain effects at defects of grown MoS 2 monolayers with nano-optical spectroscopy. NANOSCALE 2024; 16:12923-12933. [PMID: 38805074 DOI: 10.1039/d4nr00837e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2024]
Abstract
The role of defects in two-dimensional semiconductors and how they affect the intrinsic properties of these materials have been a widely researched topic over the past few decades. Optical characterization techniques such as photoluminescence and Raman spectroscopies are important tools to probe the physical properties of semiconductors and the impact of defects. However, confocal optical techniques present a spatial resolution limitation lying in a μm-scale, which can be overcome by the use of near-field optical measurements. Here, we use tip-enhanced photoluminescence and Raman spectroscopies to unveil the nanoscale optical properties of grown MoS2 monolayers, revealing that the impact of doping and strain can be disentangled by the combination of both techniques. A noticeable enhancement of the exciton peak intensity corresponding to trion emission quenching is observed at narrow regions down to a width of 47 nm at grain boundaries related to doping effects. Besides, localized strain fields inside the sample lead to non-uniformities in the intensity and energy position of photoluminescence peaks. Finally, two distinct MoS2 samples present different nano-optical responses at their edges associated with opposite strains. The edge of the first sample shows a photoluminescence intensity enhancement and energy blueshift corresponding to a frequency blueshift for E2g and 2LA Raman modes. In contrast, the other sample displays a photoluminescence energy redshift and frequency red shifts for E2g and 2LA Raman modes at their edges. Our work highlights the potential of combining tip-enhanced photoluminescence and Raman spectroscopies to probe localized strain fields and doping effects related to defects in two-dimensional materials.
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Affiliation(s)
- Frederico B Sousa
- Departamento de Física, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais 30123-970, Brazil.
| | - Rafael Nadas
- Departamento de Física, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais 30123-970, Brazil.
- FabNS, Belo Horizonte, Minas Gerais 31310-260, Brazil
| | - Rafael Martins
- Departamento de Física, Universidade Federal de Ouro Preto, Ouro Preto, Minas Gerais 35400-000, Brazil
| | - Ana P M Barboza
- Departamento de Física, Universidade Federal de Ouro Preto, Ouro Preto, Minas Gerais 35400-000, Brazil
| | - Jaqueline S Soares
- Departamento de Física, Universidade Federal de Ouro Preto, Ouro Preto, Minas Gerais 35400-000, Brazil
| | - Bernardo R A Neves
- Departamento de Física, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais 30123-970, Brazil.
| | - Ive Silvestre
- Departamento de Física, Universidade Federal de Ouro Preto, Ouro Preto, Minas Gerais 35400-000, Brazil
| | - Ado Jorio
- Departamento de Física, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais 30123-970, Brazil.
| | - Leandro M Malard
- Departamento de Física, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais 30123-970, Brazil.
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2
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Ji J, Park S, Choi JH. Morphology Engineering of Hybrid Supercapacitor Electrodes from Hierarchical Stem-like Carbon Networks with Flower-like MoS 2 Structures. ACS OMEGA 2023; 8:16833-16841. [PMID: 37214723 PMCID: PMC10193431 DOI: 10.1021/acsomega.3c00445] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/21/2023] [Accepted: 03/13/2023] [Indexed: 05/24/2023]
Abstract
There is a critical need to develop high-performance supercapacitors that can complement and even rival batteries for energy storage. This work introduces a strategy to drastically enhance the energy storage performance of a supercapacitor by engineering electrode morphologies with ternary composites offering distinct benefits for the energy storage application. The electrodes were fabricated with conductive networks of carbon nanotubes (CNTs) coated with a zeolitic imidazole framework (ZIF) for high ion diffusivity and ion-accumulating molybdenum disulfide (MoS2) with various morphologies. These include flower-like (fMoS2), stacked-plate (pMoS2), and exfoliated-flake (eMoS2) structures from topochemical synthesis. CNT-ZIF-fMoS2 demonstrates an excellent energy density, reaching almost 80 Wh/kg, and a maximum power density of approximately 3000 W/kg in a half-cell. This is far superior to the electrodes containing pMoS2 and eMoS2 and attributed to the increased surface area and the faradaic reactivity offered by fMoS2. Additionally, the CNT-ZIF-fMoS2 electrode demonstrates exceptional stability with an ∼78% of capacitance retention over 10,000 cycles. This work suggests that the electrode morphologies can dominate the energy storage behaviors and that the heteromaterial approach may be crucial in designing next-generation supercapacitors.
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3
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Ambardar S, Withers ZH, Liu J, Lai X, Albagami A, Zhukova A, Fabris Capelli P, Sahoo PK, Voronine DV. Quantum plasmonic two-dimensional WS 2-MoS 2 heterojunction. NANOSCALE 2023; 15:7318-7328. [PMID: 37017120 DOI: 10.1039/d3nr00861d] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
Two-dimensional heterostructures have recently gained broad interest due to potential applications in optoelectronic devices. Their reduced dimensionality leads to novel physical effects beyond conventional bulk electronics. However, the optical properties of the 2D lateral heterojunctions have not been completely characterized due to the limited spatial resolution, requiring nano-optical techniques beyond the diffraction limit. Here, we investigate lateral monolayer WS2-MoS2 heterostructures in a plasmonic Au-Au tip-substrate picocavity using subdiffraction limited tip-enhanced photoluminescence (TEPL) spectroscopy with sub-nanometer tip-sample distance control. We observed more than 3 orders of magnitude PL enhancement by placing a plasmonic Au-coated tip at the resonantly excited heterojunction. We developed a theoretical model of the quantum plasmonic 2D heterojunction, where tunneling of hot electrons between the Au tip and MoS2 leads to the quenching of the MoS2 PL, while simultaneously increasing the WS2 PL, in contrast to the non-resonant reverse transfer. Our simulations show good agreement with the experiments, revealing a range of parameters and enhancement factors corresponding to the switching between the classical and quantum regimes. The controllable photoresponse of the 2D heterojunction can be used in novel nanodevices.
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Affiliation(s)
- Sharad Ambardar
- Department of Medical Engineering, University of South Florida, Tampa, FL 33620, USA.
| | - Zachary H Withers
- Department of Physics, Stony Brook University, Stony Brook, NY 11790, USA
| | - Jiru Liu
- Department of Physics, Texas A&M University, College Station, TX 77840, USA
| | - Xiaoyi Lai
- CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Abdullah Albagami
- Department of Physics, King Saud University, Riyadh 11362, Kingdom of Saudi Arabia
- Department of Physics, University of South Florida, Tampa, FL 33620, USA
| | - Alina Zhukova
- Department of Physics, University of South Florida, Tampa, FL 33620, USA
| | | | - Prasana K Sahoo
- Materials Science Centre, India Institute of Technology, Kharagpur, India
| | - Dmitri V Voronine
- Department of Medical Engineering, University of South Florida, Tampa, FL 33620, USA.
- Department of Physics, University of South Florida, Tampa, FL 33620, USA
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4
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Arrighi A, Ullberg N, Derycke V, Grévin B. A simple KPFM-based approach for electrostatic- free topographic measurements: the case of MoS 2on SiO 2. NANOTECHNOLOGY 2023; 34:215705. [PMID: 36812541 DOI: 10.1088/1361-6528/acbe02] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Accepted: 02/22/2023] [Indexed: 06/18/2023]
Abstract
A simple implementation of Kelvin probe force microscopy (KPFM) is reported that enables recording topographic images in the absence of any component of the electrostatic force (including the static term). Our approach is based on a close loop z-spectroscopy operated in data cube mode. Curves of the tip-sample distance as a function of time are recorded onto a 2D grid. A dedicated circuit holds the KPFM compensation bias and subsequently cut off the modulation voltage during well-defined time-windows within the spectroscopic acquisition. Topographic images are recalculated from the matrix of spectroscopic curves. This approach is applied to the case of transition metal dichalcogenides (TMD) monolayers grown by chemical vapour deposition on silicon oxide substrates. In addition, we check to what extent a proper stacking height estimation can also be performed by recording series of images for decreasing values of the bias modulation amplitude. The outputs of both approaches are shown to be fully consistent. The results exemplify how in the operating conditions of non-contact AFM under ultra-high vacuum (nc-AFM), the stacking height values can dramatically be overestimated due to variations in the tip-surface capacitive gradient, even though the KPFM controller nullifies the potential difference. We show that the number of atomic layers of a TMD can be safely assessed, only if the KPFM measurement is performed with a modulated bias amplitude reduced at its strict minimum or, even better, without any modulated bias. Last, the spectroscopic data reveal that certain kind of defects can have a counterintuitive impact on the electrostatic landscape, resulting in an apparent decrease of the measured stacking height by conventional nc-AFM/KPFM compared to other sample areas. Hence, electrostatic free z-imaging proves to be a promising tool to assess the existence of defects in atomically thin TMD layers grown on oxides.
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Affiliation(s)
- Aloïs Arrighi
- Univ. Grenoble Alpes, CNRS, CEA, IRIG-SyMMES, F-38000 Grenoble, France
- lnstitut Néel, CNRS, Univ. Grenoble-Alpes, F-38042 Grenoble Cedex 09, France
| | - Nathan Ullberg
- Université Paris-Saclay, CEA, CNRS, NIMBE, LICSEN, F-91191 Gif-sur-Yvette, France
| | - Vincent Derycke
- Université Paris-Saclay, CEA, CNRS, NIMBE, LICSEN, F-91191 Gif-sur-Yvette, France
| | - Benjamin Grévin
- Univ. Grenoble Alpes, CNRS, CEA, IRIG-SyMMES, F-38000 Grenoble, France
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5
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Yu M, Hu Z, Zhou J, Lu Y, Guo W, Zhang Z. Retrieving Grain Boundaries in 2D Materials. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2023; 19:e2205593. [PMID: 36461686 DOI: 10.1002/smll.202205593] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2022] [Revised: 11/13/2022] [Indexed: 06/17/2023]
Abstract
The coalescence of randomly distributed grains with different crystallographic orientations can result in pervasive grain boundaries (GBs) in 2D materials during their chemical synthesis. GBs not only are the inherent structural imperfection that causes influential impacts on structures and properties of 2D materials, but also have emerged as a platform for exploring unusual physics and functionalities stemming from dramatic changes in local atomic organization and even chemical makeup. Here, recent advances in studying the formation mechanism, atomic structures, and functional properties of GBs in a range of 2D materials are reviewed. By analyzing the growth mechanism and the competition between far-field strain and local chemical energies of dislocation cores, a complete understanding of the rich GB morphologies as well as their dependence on lattice misorientations and chemical compositions is presented. Mechanical, electronic, and chemical properties tied to GBs in different materials are then discussed, towards raising the concept of using GBs as a robust atomic-scale scaffold for realizing tailored functionalities, such as magnetism, luminescence, and catalysis. Finally, the future opportunities in retrieving GBs for making functional devices and the major challenges in the controlled formation of GB structures for designed applications are commented.
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Affiliation(s)
- Maolin Yu
- Key Laboratory for Intelligent Nano Materials and Devices of Ministry of Education, State Key Laboratory of Mechanics and Control of Mechanical Structures, and Institute for Frontier Science, Nanjing University of Aeronautics and Astronautics, Nanjing, 210016, China
| | - Zhili Hu
- Key Laboratory for Intelligent Nano Materials and Devices of Ministry of Education, State Key Laboratory of Mechanics and Control of Mechanical Structures, and Institute for Frontier Science, Nanjing University of Aeronautics and Astronautics, Nanjing, 210016, China
| | - Jingzhuo Zhou
- Department of Mechanical Engineering, City University of Hong Kong, Kowloon, Hong Kong SAR, 999077, China
| | - Yang Lu
- Department of Mechanical Engineering, City University of Hong Kong, Kowloon, Hong Kong SAR, 999077, China
| | - Wanlin Guo
- Key Laboratory for Intelligent Nano Materials and Devices of Ministry of Education, State Key Laboratory of Mechanics and Control of Mechanical Structures, and Institute for Frontier Science, Nanjing University of Aeronautics and Astronautics, Nanjing, 210016, China
| | - Zhuhua Zhang
- Key Laboratory for Intelligent Nano Materials and Devices of Ministry of Education, State Key Laboratory of Mechanics and Control of Mechanical Structures, and Institute for Frontier Science, Nanjing University of Aeronautics and Astronautics, Nanjing, 210016, China
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6
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Ji J, Choi JH. Recent progress in 2D hybrid heterostructures from transition metal dichalcogenides and organic layers: properties and applications in energy and optoelectronics fields. NANOSCALE 2022; 14:10648-10689. [PMID: 35839069 DOI: 10.1039/d2nr01358d] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Atomically thin transition metal dichalcogenides (TMDs) present extraordinary optoelectronic, electrochemical, and mechanical properties that have not been accessible in bulk semiconducting materials. Recently, a new research field, 2D hybrid heteromaterials, has emerged upon integrating TMDs with molecular systems, including organic molecules, polymers, metal-organic frameworks, and carbonaceous materials, that can tailor the TMD properties and exploit synergetic effects. TMD-based hybrid heterostructures can meet the demands of future optoelectronics, including supporting flexible, transparent, and ultrathin devices, and energy-based applications, offering high energy and power densities with long cycle lives. To realize such applications, it is necessary to understand the interactions between the hybrid components and to develop strategies for exploiting the distinct benefits of each component. Here, we provide an overview of the current understanding of the new phenomena and mechanisms involved in TMD/organic hybrids and potential applications harnessing such valuable materials in an insightful way. We highlight recent discoveries relating to multicomponent hybrid materials. Finally, we conclude this review by discussing challenges related to hybrid heteromaterials and presenting future directions and opportunities in this research field.
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Affiliation(s)
- Jaehoon Ji
- School of Mechanical Engineering, Purdue University, West Lafayette, Indiana 47907, USA.
| | - Jong Hyun Choi
- School of Mechanical Engineering, Purdue University, West Lafayette, Indiana 47907, USA.
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7
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Ambardar S, Kamh R, Withers ZH, Sahoo PK, Voronine DV. Coupling nanobubbles in 2D lateral heterostructures. NANOSCALE 2022; 14:8050-8059. [PMID: 35587784 DOI: 10.1039/d2nr00512c] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Two-dimensional transition metal dichalcogenides provide flexible platforms for nanophotonic engineering due to their exceptional mechanical and optoelectronic properties. For example, continuous band gap tunability has been achieved in 2D TMDs by elastic strain engineering. Localized elastic deformations in nanobubbles behave as "artificial atoms" with a spatially varying band gap resulting in funnelling of excitons and photocarriers. Here we present a new method of nanobubble fabrication in monolayer 2D lateral heterostructures using high temperature superacid treatment. We fabricated MoS2 and WS2 nanobubbles and performed near-field imaging with nanoscale resolution using tip-enhanced photoluminescence (TEPL) spectroscopy. TEPL nanoimaging revealed the coupling between MoS2 and WS2 nanobubbles with a large synergistic PL enhancement due to the plasmonic tip, hot electrons, and exciton funnelling. We investigated the contributions of different enhancement mechanisms, and developed a quantum plasmonic model, in good agreement with the experiments. Our work opens new avenues in exploration of novel nanophotonic coupling schemes.
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Affiliation(s)
- Sharad Ambardar
- Department of Medical Engineering, University of South Florida, Tampa, FL 33620, USA.
| | - Rana Kamh
- Department of Electrical Engineering, University of South Florida, Tampa, FL 33620, USA
| | - Zachary H Withers
- Department of Physics, University of South Florida, Tampa, FL 33620, USA
| | - Prasana K Sahoo
- Materials Science Centre, India Institute of Technology, Kharagpur, India
| | - Dmitri V Voronine
- Department of Medical Engineering, University of South Florida, Tampa, FL 33620, USA.
- Department of Physics, University of South Florida, Tampa, FL 33620, USA
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8
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Tang PW, Shiau SY, Chou HC, Zhang XQ, Yu JR, Sung CT, Lee YH, Chen C. Visualization of Band Shifting and Interlayer Coupling in W xMo 1-xS 2 Alloys Using Near-Field Broadband Absorption Microscopy. ACS NANO 2022; 16:7503-7511. [PMID: 35486895 DOI: 10.1021/acsnano.1c10593] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Beyond-diffraction-limit optical absorption spectroscopy provides in-depth information on the graded band structures of composition-spread and stacked two-dimensional materials, in which direct/indirect bandgap, interlayer coupling, and defects significantly modify their optoelectronic functionalities such as photoluminescence efficiency. We here visualize the spatially varying band structure of monolayer and bilayer transition metal dichalcogenide alloys by using near-field broadband absorption microscopy. The near-field spectral and spatial information manifests the excitonic band shift that results from the interplay of composition spreading and interlayer coupling. These results enable us to identify, notably, the top layer of the bilayer alloy as pure WS2. We also use the aberration-free near-field transmission images to demarcate the exact boundaries of alloyed and pure transition metal dichalcogenides. This technology can offer valuable insights on various layered structures in the era of "stacking science" in the quest of quantum optoelectronic devices.
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Affiliation(s)
- Po-Wen Tang
- Research Center for Applied Sciences, Academia Sinica, Taipei 115, Taiwan
| | - Shiue-Yuan Shiau
- Physics Division, National Center for Theoretical Sciences, Taipei 106, Taiwan
| | - He-Chun Chou
- Research Center for Applied Sciences, Academia Sinica, Taipei 115, Taiwan
| | - Xin-Quan Zhang
- Department of Materials Science and Engineering, National Tsing-Hua University, Hsinchu 300, Taiwan
| | - Jia-Ru Yu
- Research Center for Applied Sciences, Academia Sinica, Taipei 115, Taiwan
| | - Chun-Te Sung
- Research Center for Applied Sciences, Academia Sinica, Taipei 115, Taiwan
- Department of Materials Science and Engineering, National Tsing-Hua University, Hsinchu 300, Taiwan
| | - Yi-Hsien Lee
- Department of Materials Science and Engineering, National Tsing-Hua University, Hsinchu 300, Taiwan
| | - Chi Chen
- Research Center for Applied Sciences, Academia Sinica, Taipei 115, Taiwan
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9
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Chou HC, Zhang XQ, Shiau SY, Chien CH, Tang PW, Sung CT, Chang YC, Lee YH, Chen C. Near-field spectroscopic imaging of exciton quenching at atomically sharp MoS 2/WS 2 lateral heterojunctions. NANOSCALE 2022; 14:6323-6330. [PMID: 35297443 DOI: 10.1039/d2nr00216g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Heterojunctions made by laterally stitching two different transition metal dichalcogenide monolayers create a unique one-dimensional boundary with intriguing local optical properties that can only be characterized by nanoscale-spatial-resolution spectral tools. Here, we use near-field photoluminescence (NF-PL) to reveal the narrowest region (105 nm) ever reported of photoluminescence quenching at the junction of a laterally stitched WS2/MoS2 monolayer. We attribute this quenching to the atomically sharp band offset that generates a strong electric force at the junction to easily dissociate excitons. Besides the sharp heterojunction, a model considering various widths of the alloying interfacial region under low or high optical pumping is presented. With a spatial resolution six times better than that of confocal microscopy, NF-PL provides an unprecedented spectral tool for non-scalable 1D lateral heterojunctions.
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Affiliation(s)
- He-Chun Chou
- Research Center for Applied Sciences, Academia Sinica, Taipei, 115, Taiwan.
| | - Xin-Quan Zhang
- Department of Materials Science and Engineering, National Tsing-Hua University, Hsinchu, 300, Taiwan.
| | - Shiue-Yuan Shiau
- Physics Division, National Center for Theoretical Sciences, Taipei, 106, Taiwan
| | - Ching-Hang Chien
- Research Center for Applied Sciences, Academia Sinica, Taipei, 115, Taiwan.
| | - Po-Wen Tang
- Research Center for Applied Sciences, Academia Sinica, Taipei, 115, Taiwan.
| | - Chun-Te Sung
- Research Center for Applied Sciences, Academia Sinica, Taipei, 115, Taiwan.
- Department of Materials Science and Engineering, National Tsing-Hua University, Hsinchu, 300, Taiwan.
| | - Yia-Chung Chang
- Research Center for Applied Sciences, Academia Sinica, Taipei, 115, Taiwan.
| | - Yi-Hsien Lee
- Department of Materials Science and Engineering, National Tsing-Hua University, Hsinchu, 300, Taiwan.
| | - Chi Chen
- Research Center for Applied Sciences, Academia Sinica, Taipei, 115, Taiwan.
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10
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YANG Y, HIRSINGER L, Devel M. Computation of Flexoelectric Coefficients of a MoS 2 monolayer with a Model of Self-consistently Distributed Effective Charges and Dipoles. J Chem Phys 2022; 156:174104. [DOI: 10.1063/5.0088972] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Flexoelectricity is an electromechanical coupling phenomenon, that can generate noticeable electric polarization in dielectric materials for nanoscale strain gradients. It is gaining an increasing attention because of its potential applications, and the fact that experimental results were initially an order of magnitude higher than initial theoretical predictions. This stimulated intense experimental and theoretical researches to investigate flexoelectric coefficients in dielectric materials such as two-dimensional materials. In this work, we concentrate on the calculation of the flexoelectric coefficients of 2D-MoS2 thanks to a model using self-consistently determined charges and dipoles on the atoms. More specifically, we study the importance of two contributions which were neglected/omitted in previous papers using this model, namely the charge term in the total polarization and the conservation of electric charge through a Lagrange multiplier. Our calculations demonstrate that the results for flexoelectric coefficient computed with this improved definition of polarization agree better with experimental measurements, provided consistent definitions for signs are used. Additionally, we show how two physical contributions with opposite signs compete to give net values of flexoelectric coefficients that can be either positive of negative depending on their relative importance, and give net values for the case of MoS2.
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Affiliation(s)
| | | | - Michel Devel
- Doubs, Ecole Nationale Supérieure de Mécanique et des Microtechniques, France
- FEMTO-ST
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11
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Albagami A, Ambardar S, Hrim H, Sahoo PK, Emirov Y, Gutiérrez HR, Voronine DV. Tip-Enhanced Photoluminescence of Freestanding Lateral Heterobubbles. ACS APPLIED MATERIALS & INTERFACES 2022; 14:11006-11015. [PMID: 35170302 DOI: 10.1021/acsami.1c24486] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Two-dimensional (2D) semiconducting materials have promising applications in flexible optoelectronics, nanophotonics, and sensing based on the broad tunability of their optical and electronic properties. 2D nanobubbles form exciton funnels due to localized strain that can be used as local emitters for information processing. Their nanoscale optical characterization requires the use of near-field scanning probe microscopy (SPM). However, previous near-field studies of 2D materials were performed on SiO2/Si and metallic substrates using the plasmonic gap mode to increase the signal-to-noise ratio. Another challenge is the deterministic control of bubble size and location. We addressed these challenges by investigating the photoluminescence (PL) signals of freestanding monolayer lateral WSe2-MoSe2 heterostructures under the influence of strain exerted by a plasmonic SPM tip. For first time, we performed tip-enhanced PL imaging of freestanding 2D materials and studied the competition between the PL enhancement mechanisms by nanoindentation as a function of the tip-sample distance. We observed the tunability of PL as a function of bubble size, which opens new possibilities to design optoelectronic nanodevices.
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Affiliation(s)
- Abdullah Albagami
- Department of Physics, University of South Florida, Tampa, Florida 33620, United States
- Department of Physics, King Saud University, Riyadh 11362, Kingdom of Saudi Arabia
| | - Sharad Ambardar
- Department of Medical Engineering, University of South Florida, Tampa, Florida 33620, United States
| | - Hana Hrim
- Department of Physics, University of South Florida, Tampa, Florida 33620, United States
| | - Prasana K Sahoo
- Materials Science Centre, India Institute of Technology Kharagpur, Kharagpur, West Bengal 721302, India
| | - Yusuf Emirov
- Nanotechnology Research and Education Center, University of South Florida, Tampa, Florida 33620, United States
| | - Humberto R Gutiérrez
- Department of Physics, University of South Florida, Tampa, Florida 33620, United States
| | - Dmitri V Voronine
- Department of Physics, University of South Florida, Tampa, Florida 33620, United States
- Department of Medical Engineering, University of South Florida, Tampa, Florida 33620, United States
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12
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Xia Y, He S, Wang J, Zhou L, Wang J, Komarneni S. MXene/WS 2 hybrids for visible-light-activated NO 2 sensing at room temperature. Chem Commun (Camb) 2021; 57:9136-9139. [PMID: 34498643 DOI: 10.1039/d1cc03474j] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Optoelectronic gas sensors based on two-dimensional (2D) materials are touted as potential candidates for NO2 sensing at room temperature. However, most of the developed optoelectronic sensors to date are confined to the ultraviolet region with unsatisfactory performance. Herein, a room-temperature visible-light-activated optoelectronic NO2 sensor based on 2D/2D T3C2Tx/WS2 nanocomposites is presented. The T3C2Tx/WS2-based gas sensor exhibited fast response/recovery rate, full reversibility, long stability, good selectivity, and low detection limit (10 ppb). In addition to the efficient interfacial charge separation provided by 2D/2D heterostructures, the improvement of optoelectronic NO2 sensing performance was attributed to the visible-light-activation effects. This study provides a promising method to fabricate room-temperature high-performance gas sensors based on 2D nanomaterials.
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Affiliation(s)
- Yi Xia
- Research Center for Analysis and Measurement, Kunming University of Science and Technology, and Analytic & Testing Research Center of Yunnan, Kunming 650093, China.,The Key Laboratory of Unconventional Metallurgy, Ministry of Education, Faculty of Metallurgical and Energy Engineering, Kunming University of Science and Technology, Kunming 650093, China
| | - Sufang He
- Research Center for Analysis and Measurement, Kunming University of Science and Technology, and Analytic & Testing Research Center of Yunnan, Kunming 650093, China
| | - Junming Wang
- Research Center for Analysis and Measurement, Kunming University of Science and Technology, and Analytic & Testing Research Center of Yunnan, Kunming 650093, China
| | - Liexing Zhou
- Research Center for Analysis and Measurement, Kunming University of Science and Technology, and Analytic & Testing Research Center of Yunnan, Kunming 650093, China
| | - Jing Wang
- School of Chemical and Material Engineering, Jiangnan University, Wuxi 214122, China
| | - Sridhar Komarneni
- Department of Ecosystem Science and Management and Materials Research Institute, 204 Energy and the Environment Laboratory, The Pennsylvania State University, University Park, PA 16802, USA.
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13
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Lei L, Lun Y, Cao F, Meng L, Xing S, Guo J, Dong H, Gu S, Xu K, Hussain S, Li YJ, Sugawara Y, Pang F, Ji W, Hong J, Xu R, Cheng Z. Size-dependent strain-engineered nanostructures in MoS 2monolayer investigated by atomic force microscopy. NANOTECHNOLOGY 2021; 32:465703. [PMID: 34359059 DOI: 10.1088/1361-6528/ac1b54] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2021] [Accepted: 08/06/2021] [Indexed: 06/13/2023]
Abstract
The strain has been employed for controlled modification of electronical and mechanical properties of two-dimensional (2D) materials. However, the thermal strain-engineered behaviors of the CVD-grown MoS2have not been systematically explored. Here, we investigated the strain-induced structure and properties of CVD-grown triangular MoS2flakes by several advanced atomic force microscopy. Two different kinds of flakes with sharp-corner or vein-like nanostructures are experimentally discovered due to the size-dependent strain behaviors. The critical size of these two kinds of flakes can be roughly estimated at ∼17μm. Within the small flakes, the sharp-corner regions show specific strain-modified properties due to the suffering of large tensile strain. While in the large MoS2flakes, the complicated vein-like nanoripple structures were formed due to the interface slipping process under the larger tensile strain. Our work not only demonstrates the size-specific strain behaviors of MoS2flakes but also sheds light on the artificial design and preparation of strain-engineered nanostructures for the devices based on the 2D materials.
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Affiliation(s)
- Le Lei
- Beijing Key Laboratory of Optoelectronic Functional Materials & Micro-nano Devices, Department of Physics, Renmin University of China, Beijing 100872, People's Republic of China
| | - Yingzhuo Lun
- School of Aerospace Engineering, Beijing Institute of Technology, Beijing 100081, People's Republic of China
| | - Feiyue Cao
- Beijing Key Laboratory of Optoelectronic Functional Materials & Micro-nano Devices, Department of Physics, Renmin University of China, Beijing 100872, People's Republic of China
| | - Lan Meng
- College of Electronic Science and Engineering, Nanjing University of Posts and Telecommunications, Nanjing 210046, People's Republic of China
| | - Shuya Xing
- Beijing Key Laboratory of Optoelectronic Functional Materials & Micro-nano Devices, Department of Physics, Renmin University of China, Beijing 100872, People's Republic of China
| | - Jianfeng Guo
- Beijing Key Laboratory of Optoelectronic Functional Materials & Micro-nano Devices, Department of Physics, Renmin University of China, Beijing 100872, People's Republic of China
| | - Haoyu Dong
- Beijing Key Laboratory of Optoelectronic Functional Materials & Micro-nano Devices, Department of Physics, Renmin University of China, Beijing 100872, People's Republic of China
| | - Shangzhi Gu
- Beijing Key Laboratory of Optoelectronic Functional Materials & Micro-nano Devices, Department of Physics, Renmin University of China, Beijing 100872, People's Republic of China
| | - Kunqi Xu
- CAS Key Laboratory of Standardization and Measurement for Nanotechnology, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190, People's Republic of China
| | - Sabir Hussain
- CAS Key Laboratory of Standardization and Measurement for Nanotechnology, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190, People's Republic of China
| | - Yan Jun Li
- Department of Applied Physics, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Yasuhiro Sugawara
- Department of Applied Physics, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Fei Pang
- Beijing Key Laboratory of Optoelectronic Functional Materials & Micro-nano Devices, Department of Physics, Renmin University of China, Beijing 100872, People's Republic of China
| | - Wei Ji
- Beijing Key Laboratory of Optoelectronic Functional Materials & Micro-nano Devices, Department of Physics, Renmin University of China, Beijing 100872, People's Republic of China
| | - Jiawang Hong
- School of Aerospace Engineering, Beijing Institute of Technology, Beijing 100081, People's Republic of China
| | - Rui Xu
- Beijing Key Laboratory of Optoelectronic Functional Materials & Micro-nano Devices, Department of Physics, Renmin University of China, Beijing 100872, People's Republic of China
| | - Zhihai Cheng
- Beijing Key Laboratory of Optoelectronic Functional Materials & Micro-nano Devices, Department of Physics, Renmin University of China, Beijing 100872, People's Republic of China
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14
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Abstract
Tip-enhanced nano-spectroscopy, such as tip-enhanced photoluminescence (TEPL) and tip-enhanced Raman spectroscopy (TERS), generally suffers from inconsistent signal enhancement and difficulty in polarization-resolved measurement. To address this problem, we present adaptive tip-enhanced nano-spectroscopy optimizing the nano-optical vector-field at the tip apex. Specifically, we demonstrate dynamic wavefront shaping of the excitation field to effectively couple light to the tip and adaptively control for enhanced sensitivity and polarization-controlled TEPL and TERS. Employing a sequence feedback algorithm, we achieve ~4.4 × 104-fold TEPL enhancement of a WSe2 monolayer which is >2× larger than the normal TEPL intensity without wavefront shaping. In addition, with dynamical near-field polarization control in TERS, we demonstrate the investigation of conformational heterogeneity of brilliant cresyl blue molecules and the controllable observation of IR-active modes due to a large gradient field effect. Adaptive tip-enhanced nano-spectroscopy thus provides for a systematic approach towards computational nanoscopy making optical nano-imaging more robust and widely deployable. Tip-enhanced nano-spectroscopy suffers from inconsistent signal and difficulty in polarization-resolved measurement. Here, the authors present adaptive tip-enhanced nano-spectroscopy, which enables the additional signal enhancement and near-field polarization control via dynamic wavefront shaping.
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15
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Fali A, Zhang T, Terry JP, Kahn E, Fujisawa K, Kabius B, Koirala S, Ghafouri Y, Zhou D, Song W, Yang L, Terrones M, Abate Y. Photodegradation Protection in 2D In-Plane Heterostructures Revealed by Hyperspectral Nanoimaging: The Role of Nanointerface 2D Alloys. ACS NANO 2021; 15:2447-2457. [PMID: 33464036 DOI: 10.1021/acsnano.0c06148] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Single-layer heterostructures exhibit striking quasiparticle properties and many-body interaction effects that hold promise for a range of applications. However, their properties can be altered by intrinsic and extrinsic defects, thus diminishing their applicability. Therefore, it is of paramount importance to identify defects and understand 2D materials' degradation over time using advanced multimodal imaging techniques. Here we implemented a liquid-phase precursor approach to synthesize 2D in-plane MoS2-WS2 heterostructures exhibiting nanoscale alloyed interfaces and map exotic interface effects during photodegradation using a combination of hyperspectral tip-enhanced photoluminescence and Raman and near-field nanoscopy. Surprisingly, 2D alloyed regions exhibit thermal and photodegradation stability providing protection against oxidation. Coupled with surface and interface strain, 2D alloy regions create stable localized potential wells that concentrate excitonic species via a charge carrier funneling effect. These results demonstrate that 2D alloys can withstand extreme degradation effects over time and could enable stable 2D device engineering.
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Affiliation(s)
- Alireza Fali
- Department of Physics and Astronomy, University of Georgia, Athens, Georgia 30602, United States
| | - Tianyi Zhang
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Jason Patrick Terry
- Department of Physics and Astronomy, University of Georgia, Athens, Georgia 30602, United States
| | - Ethan Kahn
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Kazunori Fujisawa
- Department of Physics and Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Bernd Kabius
- Department of Physics and Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Sandhaya Koirala
- Department of Physics and Astronomy, University of Georgia, Athens, Georgia 30602, United States
| | - Yassamin Ghafouri
- Department of Physics and Astronomy, University of Georgia, Athens, Georgia 30602, United States
| | - Da Zhou
- Department of Physics and Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Wenshen Song
- Department of Physics and Institute of Materials Science & Engineering, Washington University in St Louis, St. Louis, Missouri 63130, United States
| | - Li Yang
- Department of Physics and Institute of Materials Science & Engineering, Washington University in St Louis, St. Louis, Missouri 63130, United States
| | - Mauricio Terrones
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Department of Physics and Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Yohannes Abate
- Department of Physics and Astronomy, University of Georgia, Athens, Georgia 30602, United States
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16
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Lee K, Lee H, Kim Y, Choi J, Ahn JP, Shin DH, Cho YH, Jang HK, Lee SW, Shin J, Ji H, Kim GT. Real-time effect of electron beam on MoS 2 field-effect transistors. NANOTECHNOLOGY 2020; 31:455202. [PMID: 32325431 DOI: 10.1088/1361-6528/ab8c78] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Irradiation of MoS2 field-effect transistors (FETs) fabricated on Si/SiO2 substrates with electron beams (e-beams) below 30 keV creates electron-hole pairs (EHP) in the SiO2, which increase the interface trap density (Nit ) and change the current path in the channel, resulting in performance changes. In situ measurements of the electrical characteristics of the FET performed using a nano-probe system mounted inside a scanning electron microscope show that e-beam irradiation enables both multilayer and monolayer MoS2 channels act as conductors. The e-beams mostly penetrate the channel owing to their large kinetic energy, while the EHPs formed in the SiO2 layer can contribute to the conductance by flowing into the MoS2 channel or inducing the gate bias effect. The analysis of the device parameters in the initial state and the vent-evacuation state after e-beam irradiation can clarify the effect of the interplay between the e-beam-induced EHPs and ambient adsorbates on the carrier behavior, which depends on the thickness of the MoS2 layer. DC and low frequency noise analysis reveals that the e-beam-induced EHPs increase Nit from 109-1010 to 1011 cm-2 eV-1 in both monolayer and multilayer devices, while the interfacial Coulomb scattering parameter αSC increases by three times in the monolayer and decreases to one-tenth of its original value in the multilayer. In other words, an MoS2 layer with a thickness of ∼30 nm is less sensitive to adsorbates by surface screening. Thus, the carrier mobility in the monolayer device decreases from 45.7 to 40 cm2 V-1 s-1, while in the 30 nm-thick multilayer device, it increases from 4.9 to 5.6 cm2 V-1 s-1. This is further evidenced by simulations of the distribution of interface traps and channel carriers in the MoS2 FET before and after e-beam irradiation, demonstrating that Coulomb scattering decreases as the effective channel moves away from the interface.
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Affiliation(s)
- Kookjin Lee
- School of Electrical Engineering, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul 02841, Republic of Korea
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17
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Abstract
Grain boundaries (GBs) are a kind of lattice imperfection widely existing in two-dimensional materials, playing a critical role in materials' properties and device performance. Related key issues in this area have drawn much attention and are still under intense investigation. These issues include the characterization of GBs at different length scales, the dynamic formation of GBs during the synthesis, the manipulation of the configuration and density of GBs for specific material functionality, and the understanding of structure-property relationships and device applications. This review will provide a general introduction of progress in this field. Several techniques for characterizing GBs, such as direct imaging by high-resolution transmission electron microscopy, visualization techniques of GBs by optical microscopy, plasmon propagation, or second harmonic generation, are presented. To understand the dynamic formation process of GBs during the growth, a general geometric approach and theoretical consideration are reviewed. Moreover, strategies controlling the density of GBs for GB-free materials or materials with tunable GB patterns are summarized, and the effects of GBs on materials' properties are discussed. Finally, challenges and outlook are provided.
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Affiliation(s)
- Wenqian Yao
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Science, Beijing 100190, P.R. China
- Sino-Danish Center for Education and Research, Sino-Danish College, University of Chinese Academy of Sciences, Beijing 100049, P.R. China
| | - Bin Wu
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Science, Beijing 100190, P.R. China
| | - Yunqi Liu
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Science, Beijing 100190, P.R. China
- Sino-Danish Center for Education and Research, Sino-Danish College, University of Chinese Academy of Sciences, Beijing 100049, P.R. China
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18
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Yu JR, Chou HC, Yang CW, Liao WS, Hwang IS, Chen C. A horizontal-type scanning near-field optical microscope with torsional mode operation toward high-resolution and non-destructive imaging of soft materials. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2020; 91:073703. [PMID: 32752832 DOI: 10.1063/5.0009422] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2020] [Accepted: 07/09/2020] [Indexed: 06/11/2023]
Abstract
We design and build a horizontal-type aperture based scanning near-field optical microscope (a-SNOM) with superior mechanical stability toward high-resolution and non-destructive topographic and optical imaging. We adopt the torsional mode in AFM (atomic force microscopy) operation to achieve a better force sensitivity and a higher topographic resolution when using pyramidal a-SNOM tips. The performance and stability of the AFM are evaluated through single-walled carbon nanotube and poly(3-hexyl-thiophene) nanowire samples. An optical resolution of 93 nm is deduced from the a-SNOM imaging of a metallic grating. Finally, a-SNOM fluorescence imaging of soft lipid domains is successfully achieved without sample damage by our horizontal-type a-SNOM instrument with torsional mode AFM operation.
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Affiliation(s)
- Jia-Ru Yu
- Research Center for Applied Sciences, Academia Sinica, Nangang, Taipei 115, Taiwan
| | - He-Chun Chou
- Research Center for Applied Sciences, Academia Sinica, Nangang, Taipei 115, Taiwan
| | - Chih-Wen Yang
- Institute of Physics, Academia Sinica, Nankang, Taipei 115, Taiwan
| | - Wei-Ssu Liao
- Department of Chemistry, National Taiwan University, Da-an, Taipei 106, Taiwan
| | - Ing-Shouh Hwang
- Institute of Physics, Academia Sinica, Nankang, Taipei 115, Taiwan
| | - Chi Chen
- Research Center for Applied Sciences, Academia Sinica, Nangang, Taipei 115, Taiwan
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19
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Negri M, Francaviglia L, Dumcenco D, Bosi M, Kaplan D, Swaminathan V, Salviati G, Kis A, Fabbri F, Fontcuberta I Morral A. Quantitative Nanoscale Absorption Mapping: A Novel Technique To Probe Optical Absorption of Two-Dimensional Materials. NANO LETTERS 2020; 20:567-576. [PMID: 31874041 DOI: 10.1021/acs.nanolett.9b04304] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Two-dimensional semiconductors, in particular transition metal dichalcogenides and related heterostructures, have gained increasing interest as they constitute potential new building blocks for the next generation of electronic and optoelectronic applications. In this work, we develop a novel nondestructive and noncontact technique for mapping the absorption properties of 2D materials, by taking advantage of the underlying substrate cathodoluminescence emission. We map the quantitative absorption of MoS2 and MoSe2 monolayers, obtained on sapphire and oxidized silicon, with nanoscale resolution. We extend our technique to the characterization of the absorption properties of MoS2/MoSe2 van der Waals heterostructures. We demonstrate that interlayer excitonic phenomena enhance the absorption in the UV range. Our technique also highlights the presence of defects such as grain boundaries and ad-layers. We provide measurements on the absorption of grain boundaries in monolayer MoS2 at different merging angles. We observe a higher absorption yield of randomly oriented monolayers with respect to 60° rotated monolayers. This work opens up a new possibility for characterizing the functional properties two-dimensional semiconductors at the nanoscale.
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Affiliation(s)
- Marco Negri
- Institute of Materials, Faculty of Engineering , École Polytechnique Fédérale de Lausanne , 1015 Lausanne , Switzerland
| | - Luca Francaviglia
- Institute of Materials, Faculty of Engineering , École Polytechnique Fédérale de Lausanne , 1015 Lausanne , Switzerland
| | - Dumitru Dumcenco
- Institute of Materials, Faculty of Engineering , École Polytechnique Fédérale de Lausanne , 1015 Lausanne , Switzerland
- Electrical Engineering Institute , École Polytechnique Fédérale de Lausanne (EPFL) , CH-1015 Lausanne , Switzerland
| | - Matteo Bosi
- Institute for Materials for Electronics and Magnetism (IMEM-CNR) , Parco Area delle Scienze 37/A , 43124 Parma , Italy
| | - Daniel Kaplan
- Fuze Precision Armaments and Technology Directorate , U.S. Army RDECOM-ARDEC , Picatinny Arsenal , New Jersey 07806 , United States
| | - Venkataraman Swaminathan
- Fuze Precision Armaments and Technology Directorate , U.S. Army RDECOM-ARDEC , Picatinny Arsenal , New Jersey 07806 , United States
| | - Giancarlo Salviati
- Institute for Materials for Electronics and Magnetism (IMEM-CNR) , Parco Area delle Scienze 37/A , 43124 Parma , Italy
| | - Andras Kis
- Electrical Engineering Institute , École Polytechnique Fédérale de Lausanne (EPFL) , CH-1015 Lausanne , Switzerland
| | - Filippo Fabbri
- NEST , Istituto Nanoscienze-CNR, Scuola Normale Superiore , Piazza San Silvestro 12 , 56127 Pisa , Italy
| | - Anna Fontcuberta I Morral
- Institute of Materials, Faculty of Engineering , École Polytechnique Fédérale de Lausanne , 1015 Lausanne , Switzerland
- Institute of Physics, Faculty of Basic Sciences , École Polytechnique Fédérale de Lausanne , 1015 Lausanne , Switzerland
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20
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Reconfigurable Local Photoluminescence of Atomically-Thin Semiconductors via Ferroelectric-Assisted Effects. NANOMATERIALS 2019; 9:nano9111620. [PMID: 31731643 PMCID: PMC6915559 DOI: 10.3390/nano9111620] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/04/2019] [Revised: 11/04/2019] [Accepted: 11/11/2019] [Indexed: 11/16/2022]
Abstract
Combining a pair of materials of different structural dimensions and functional properties into a hybrid material system may realize unprecedented multi-functional device applications. Especially, two-dimensional (2D) materials are suitable for being incorporated into the heterostructures due to their colossal area-to-volume ratio, excellent flexibility, and high sensitivity to interfacial and surface interactions. Semiconducting molybdenum disulfide (MoS2), one of the well-studied layered materials, has a direct band gap as one molecular layer and hence, is expected to be one of the promising key materials for next-generation optoelectronics. Here, using lateral 2D/3D heterostructures composed of MoS2 monolayers and nanoscale inorganic ferroelectric thin films, reversibly tunable photoluminescence has been demonstrated at the microscale to be over 200% upon ferroelectric polarization reversal by using nanoscale conductive atomic force microscopy tips. Also, significant ferroelectric-assisted modulation in electrical properties has been achieved from field-effect transistor devices based on the 2D/3D heterostructrues. Moreover, it was also shown that the MoS2 monolayer can be an effective electric field barrier in spite of its sub-nanometer thickness. These results would be of close relevance to exploring novel applications in the fields of optoelectronics and sensor technology.
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21
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Chen X, Hu D, Mescall R, You G, Basov DN, Dai Q, Liu M. Modern Scattering-Type Scanning Near-Field Optical Microscopy for Advanced Material Research. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2019; 31:e1804774. [PMID: 30932221 DOI: 10.1002/adma.201804774] [Citation(s) in RCA: 91] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2018] [Revised: 02/27/2019] [Indexed: 05/27/2023]
Abstract
Infrared and optical spectroscopy represents one of the most informative methods in advanced materials research. As an important branch of modern optical techniques that has blossomed in the past decade, scattering-type scanning near-field optical microscopy (s-SNOM) promises deterministic characterization of optical properties over a broad spectral range at the nanoscale. It allows ultrabroadband optical (0.5-3000 µm) nanoimaging, and nanospectroscopy with fine spatial (<10 nm), spectral (<1 cm-1 ), and temporal (<10 fs) resolution. The history of s-SNOM is briefly introduced and recent advances which broaden the horizons of this technique in novel material research are summarized. In particular, this includes the pioneering efforts to study the nanoscale electrodynamic properties of plasmonic metamaterials, strongly correlated quantum materials, and polaritonic systems at room or cryogenic temperatures. Technical details, theoretical modeling, and new experimental methods are also discussed extensively, aiming to identify clear technology trends and unsolved challenges in this exciting field of research.
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Affiliation(s)
- Xinzhong Chen
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, 11794, USA
| | - Debo Hu
- Division of Nanophotonics, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing, 100190, China
| | - Ryan Mescall
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, 11794, USA
| | - Guanjun You
- Shanghai Key Lab of Modern Optical Systems and Engineering Research Center of Optical Instrument and System, Ministry of Education, University of Shanghai for Science and Technology, Shanghai, 200093, China
| | - D N Basov
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Qing Dai
- Division of Nanophotonics, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing, 100190, China
| | - Mengkun Liu
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, 11794, USA
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22
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Mendes RG, Pang J, Bachmatiuk A, Ta HQ, Zhao L, Gemming T, Fu L, Liu Z, Rümmeli MH. Electron-Driven In Situ Transmission Electron Microscopy of 2D Transition Metal Dichalcogenides and Their 2D Heterostructures. ACS NANO 2019; 13:978-995. [PMID: 30673226 DOI: 10.1021/acsnano.8b08079] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Investigations on monolayered transition metal dichalcogenides (TMDs) and TMD heterostructures have been steadily increasing over the past years due to their potential application in a wide variety of fields such as microelectronics, sensors, batteries, solar cells, and supercapacitors, among others. The present work focuses on the characterization of TMDs using transmission electron microscopy, which allows not only static atomic resolution but also investigations into the dynamic behavior of atoms within such materials. Herein, we present a body of recent research from the various techniques available in the transmission electron microscope to structurally and analytically characterize layered TMDs and briefly compare the advantages of TEM with other characterization techniques. Whereas both static and dynamic aspects are presented, special emphasis is given to studies on the electron-driven in situ dynamic aspects of these materials while under investigation in a transmission electron microscope. The collection of the presented results points to a future prospect where electron-driven nanomanipulation may be routinely used not only in the understanding of fundamental properties of TMDs but also in the electron beam engineering of nanocircuits and nanodevices.
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Affiliation(s)
- Rafael G Mendes
- Leibniz Institute for Solid State and Materials Research Dresden , P.O. Box 270116, Dresden D-01171 , Germany
| | - Jinbo Pang
- Leibniz Institute for Solid State and Materials Research Dresden , P.O. Box 270116, Dresden D-01171 , Germany
| | - Alicja Bachmatiuk
- Leibniz Institute for Solid State and Materials Research Dresden , P.O. Box 270116, Dresden D-01171 , Germany
- Centre of Polymer and Carbon Materials , Polish Academy of Sciences , M. Curie-Skłodowskiej 34 , Zabrze 41-819 , Poland
| | | | | | - Thomas Gemming
- Leibniz Institute for Solid State and Materials Research Dresden , P.O. Box 270116, Dresden D-01171 , Germany
| | - Lei Fu
- College of Chemistry and Molecular Science , Wuhan University , Wuhan 430072 , China
| | - Zhongfan Liu
- Center for Nanochemistry, Beijing Science and Engineering Centre for Nanocarbons, Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering , Peking University , Beijing 100871 , China
| | - Mark H Rümmeli
- Leibniz Institute for Solid State and Materials Research Dresden , P.O. Box 270116, Dresden D-01171 , Germany
- Centre of Polymer and Carbon Materials , Polish Academy of Sciences , M. Curie-Skłodowskiej 34 , Zabrze 41-819 , Poland
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23
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Molas MR, Gołasa K, Bala Ł, Nogajewski K, Bartos M, Potemski M, Babiński A. Tuning carrier concentration in a superacid treated MoS 2 monolayer. Sci Rep 2019; 9:1989. [PMID: 30760791 PMCID: PMC6374480 DOI: 10.1038/s41598-018-38413-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2018] [Accepted: 12/27/2018] [Indexed: 11/25/2022] Open
Abstract
The effect of bis(trifluoromethane) sulfonimide (TFSI, superacid) treatment on the optical properties of MoS2 monolayers is investigated by means of photoluminescence, reflectance contrast and Raman scattering spectroscopy employed in a broad temperature range. It is shown that when applied multiple times, the treatment results in progressive quenching of the trion emission/absorption and in the redshift of the neutral exciton emission/absorption associated with both the A and B excitonic resonances. Based on this evolution, a trion complex related to the B exciton in monolayer MoS2 is unambiguously identified. A defect-related emission observed at low temperatures also disappears from the spectrum as a result of the treatment. Our observations are attributed to effective passivation of defects on the MoS2 monolayer surface. The passivation reduces the carrier density, which in turn affects the out-of-plane electric field in the sample. The observed tuning of the carrier concentration strongly influences also the Raman scattering in the MoS2 monolayer. An enhancement of Raman scattering at resonant excitation in the vicinity of the A neutral exciton is clearly seen for both the out-of-plane A′1 and in-plane E′ modes. On the contrary, when the excitation is in resonance with a corresponding trion, the Raman scattering features become hardly visible. These results confirm the role of the excitonic charge state plays in the resonance effect of the excitation energy on the Raman scattering in transition metal dichalcogenides.
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Affiliation(s)
- Maciej R Molas
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093, Warszawa, Poland. .,Laboratoire National des Champs Magnétiques Intenses, CNRS-UGA-UPS-INSA-EMFL, 25, avenue des Martyrs, 38042, Grenoble, France.
| | - Katarzyna Gołasa
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093, Warszawa, Poland
| | - Łukasz Bala
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093, Warszawa, Poland.,Laboratoire National des Champs Magnétiques Intenses, CNRS-UGA-UPS-INSA-EMFL, 25, avenue des Martyrs, 38042, Grenoble, France
| | - Karol Nogajewski
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093, Warszawa, Poland.,Laboratoire National des Champs Magnétiques Intenses, CNRS-UGA-UPS-INSA-EMFL, 25, avenue des Martyrs, 38042, Grenoble, France
| | - Miroslav Bartos
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093, Warszawa, Poland
| | - Marek Potemski
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093, Warszawa, Poland.,Laboratoire National des Champs Magnétiques Intenses, CNRS-UGA-UPS-INSA-EMFL, 25, avenue des Martyrs, 38042, Grenoble, France
| | - Adam Babiński
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093, Warszawa, Poland.
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24
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Syari'ati A, Kumar S, Zahid A, Ali El Yumin A, Ye J, Rudolf P. Photoemission spectroscopy study of structural defects in molybdenum disulfide (MoS 2) grown by chemical vapor deposition (CVD). Chem Commun (Camb) 2019; 55:10384-10387. [PMID: 31396602 DOI: 10.1039/c9cc01577a] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The fingerprint of structural defects in CVD grown MoS2 was revealed by means of X-ray Photoelectron Spectroscopy (XPS). These defects can be partially healed by grafting thiol-functionalized molecules. The functionalization does not alter the semiconducting properties of MoS2 as confirmed by the photoluminescence spectra.
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Affiliation(s)
- Ali Syari'ati
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands.
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Xu H, Zhang H, Guo Z, Shan Y, Wu S, Wang J, Hu W, Liu H, Sun Z, Luo C, Wu X, Xu Z, Zhang DW, Bao W, Zhou P. High-Performance Wafer-Scale MoS 2 Transistors toward Practical Application. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2018; 14:e1803465. [PMID: 30328296 DOI: 10.1002/smll.201803465] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2018] [Revised: 09/24/2018] [Indexed: 05/13/2023]
Abstract
Atomic thin transition-metal dichalcogenides (TMDs) are considered as an emerging platform to build next-generation semiconductor devices. However, to date most devices are still based on exfoliated TMD sheets on a micrometer scale. Here, a novel chemical vapor deposition synthesis strategy by introducing multilayer (ML) MoS2 islands to improve device performance is proposed. A four-probe method is applied to confirm that the contact resistance decreases by one order of magnitude, which can be attributed to a conformal contact by the extra amount of exposed edges from the ML-MoS2 islands. Based on such continuous MoS2 films synthesized on a 2 in. insulating substrate, a top-gated field effect transistor (FET) array is fabricated to explore key metrics such as threshold voltage (V T ) and field effect mobility (μFE ) for hundreds of MoS2 FETs. The statistical results exhibit a surprisingly low variability of these parameters. An average effective μFE of 70 cm2 V-1 s-1 and subthreshold swing of about 150 mV dec-1 are extracted from these MoS2 FETs, which are comparable to the best top-gated MoS2 FETs achieved by mechanical exfoliation. The result is a key step toward scaling 2D-TMDs into functional systems and paves the way for the future development of 2D-TMDs integrated circuits.
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Affiliation(s)
- Hu Xu
- State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai, 200433, China
| | - Haima Zhang
- State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai, 200433, China
| | - Zhongxun Guo
- State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai, 200433, China
| | - Yuwei Shan
- State Key Laboratory of Surface Physics, Key Laboratory of Micro and Nano Photonic Structures (MOE), Physics Department, Fudan University, Shanghai, 200433, China
| | - Shiwei Wu
- State Key Laboratory of Surface Physics, Key Laboratory of Micro and Nano Photonic Structures (MOE), Physics Department, Fudan University, Shanghai, 200433, China
| | - Jianlu Wang
- State Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Science, 500 Yutian Road, Shanghai, 200083, China
| | - Weida Hu
- State Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Science, 500 Yutian Road, Shanghai, 200083, China
| | - Hanqi Liu
- Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Department of Chemistry, Fudan University, Shanghai, 200433, China
| | - Zhengzong Sun
- Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Department of Chemistry, Fudan University, Shanghai, 200433, China
| | - Chen Luo
- Shanghai Key Laboratory of Multidimensional Information Processing, Department of Electronic Engineering, East China Normal University, 500 Dongchuan Road, Shanghai, 200241, China
| | - Xing Wu
- Shanghai Key Laboratory of Multidimensional Information Processing, Department of Electronic Engineering, East China Normal University, 500 Dongchuan Road, Shanghai, 200241, China
| | - Zihan Xu
- Shenzhen 6 Carbon Technology, Shenzhen, 518106, China
| | - David Wei Zhang
- State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai, 200433, China
| | - Wenzhong Bao
- State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai, 200433, China
| | - Peng Zhou
- State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai, 200433, China
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Lee C, Jeong BG, Yun SJ, Lee YH, Lee SM, Jeong MS. Unveiling Defect-Related Raman Mode of Monolayer WS 2 via Tip-Enhanced Resonance Raman Scattering. ACS NANO 2018; 12:9982-9990. [PMID: 30142265 DOI: 10.1021/acsnano.8b04265] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Monolayer tungsten disulfide (WS2) has emerged as an active material for optoelectronic devices due to its quantum yield of photoluminescence. Despite the enormous research about physical characteristics of monolayer WS2, the defect-related Raman scattering has been rarely studied. Here, we report the correlation of topography and Raman scattering in monolayer WS2 by using tip-enhanced resonance Raman spectroscopy and reveal defect-related Raman modes denoted as D and D' modes. We found that the sulfur vacancies introduce not only the red-shifted A1g mode but also the D and D' modes by the density functional theory calculations. The observed defect-related Raman modes can be utilized to evaluate the quality of monolayer WS2 and will be helpful to improve the performance of WS2 optoelectronic devices.
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Affiliation(s)
- Chanwoo Lee
- Department of Energy Science , Sungkyunkwan University , Suwon 16419 , Republic of Korea
- Center for Integrated Nanostructure Physics (CINAP) , Institute for Basic Science (IBS) , Suwon 16419 , Republic of Korea
| | - Byeong Geun Jeong
- Department of Energy Science , Sungkyunkwan University , Suwon 16419 , Republic of Korea
| | - Seok Joon Yun
- Department of Energy Science , Sungkyunkwan University , Suwon 16419 , Republic of Korea
- Center for Integrated Nanostructure Physics (CINAP) , Institute for Basic Science (IBS) , Suwon 16419 , Republic of Korea
| | - Young Hee Lee
- Department of Energy Science , Sungkyunkwan University , Suwon 16419 , Republic of Korea
- Center for Integrated Nanostructure Physics (CINAP) , Institute for Basic Science (IBS) , Suwon 16419 , Republic of Korea
- Department of Physics , Sungkyunkwan University , Suwon 16419 , Republic of Korea
| | - Seung Mi Lee
- Korea Research Institute of Standards and Science (KRISS) , Daejeon 34113 , Republic of Korea
| | - Mun Seok Jeong
- Department of Energy Science , Sungkyunkwan University , Suwon 16419 , Republic of Korea
- Center for Integrated Nanostructure Physics (CINAP) , Institute for Basic Science (IBS) , Suwon 16419 , Republic of Korea
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27
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Ahn H, Huang YC, Lin CW, Chiu YL, Lin EC, Lai YY, Lee YH. Efficient Defect Healing of Transition Metal Dichalcogenides by Metallophthalocyanine. ACS APPLIED MATERIALS & INTERFACES 2018; 10:29145-29152. [PMID: 30044602 DOI: 10.1021/acsami.8b09378] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Two-dimensional (2D) transition metal dichalcogenides (TMDCs) have attracted great attention as alternatives to graphene with semiconducting band gaps. Mono- or few-layer TMDCs can be prepared by various methods, but regardless of the fabrication methods [such as mechanical exfoliation and chemical vapor deposition (CVD)], TMDCs contain many structural defects, which significantly affect their physical properties and limit their performance in applications. Metallophthalocyanines (MPcs) are organic semiconductors, and as dopants, they are capable of modulating the optical and electrical properties of other semiconducting materials. Here, we report that besides the ability to modulate the optoelectronic properties of 2D TMDCs, MPc molecules can be used to heal defects and improve the physicochemical properties of TMDCs. Doping of planar MPc molecules to TMDCs is achieved by a simple solution dip-coating method and results in a significant improvement in the optical properties and thermal responses of CVD-grown TMDCs, even comparable to those of mechanically exfoliated counterparts. Study of carrier dynamics shows that the adsorption of MPc on the TMDC surface leads to the complete suppression of the mid-gap defect-induced absorption in TMDCs. Furthermore, MPc molecules with a large lateral size are found to effectively reduce the point defects in mechanically exfoliated TMDCs introduced during the preparation process. Our results not only clarify the optoelectronic modulation mechanism of chemical doping but also offer a simple method to control the nanosized defects in 2D TMDCs.
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Affiliation(s)
- Hyeyoung Ahn
- Department of Photonics , National Chiao Tung University , Hsinchu 30010 , Taiwan
| | - Yu-Chiao Huang
- Department of Photonics , National Chiao Tung University , Hsinchu 30010 , Taiwan
| | - Chang-Wei Lin
- Department of Photonics , National Chiao Tung University , Hsinchu 30010 , Taiwan
| | - Yi-Lun Chiu
- Department of Photonics , National Chiao Tung University , Hsinchu 30010 , Taiwan
| | - Erh-Chen Lin
- Institute of NanoEngineering and MicroSystems , National Tsing-Hua University , Hsinchu 30010 , Taiwan
| | - Ying-Yu Lai
- Institute of NanoEngineering and MicroSystems , National Tsing-Hua University , Hsinchu 30010 , Taiwan
| | - Yi-Hsien Lee
- Institute of NanoEngineering and MicroSystems , National Tsing-Hua University , Hsinchu 30010 , Taiwan
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Kim Y, Lee Y, Kim H, Roy S, Kim J. Near-field exciton imaging of chemically treated MoS 2 monolayers. NANOSCALE 2018; 10:8851-8858. [PMID: 29714393 DOI: 10.1039/c8nr00606g] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The exciton-dominated light emission of two-dimensional (2D) semiconductors is determined largely by the doping state and the formation of defects. Extensive studies have shown that chemical treatment critically modifies the doping state and defect state of chemical vapor deposition (CVD)-grown or exfoliated monolayer MoS2 (1L-MoS2), suggesting a promising possibility for engineering the optoelectronic properties of 2D semiconductors. However, chemical treatment inevitably modifies both the doping state and defect states, and their independent roles in the exciton emission of 1L-MoS2 have been difficult to study, significantly limiting the practical and reliable uses of chemical treatment to improve the optical properties of 1L-TMDs. Herein, we used near-field imaging and spectroscopy to investigate the effects of chemical treatment on the exciton emission of 1L-MoS2. CVD-grown 1L-MoS2 was treated with bis(trifluoromethane)-sulfonimide (TFSI) or 7,7,8,8-tetracyanoquinodimethane (TCNQ), and nanoscale maps of neutral exciton and trion emission before and after chemical treatment were obtained with 80 nm spatial resolution. A comparison of the local spatial and spectral compositions of neutral excitons and trions suggested that the p-doping effect of TFSI was especially strong around local defects, whereas electron depletion by TCNQ was spatially uniform. The specific reaction of TFSI to defect locations observed in our study provides the clue for the reason that TFSI is notably effective at improving the light emission of 1L-MoS2.
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Affiliation(s)
- Youngbum Kim
- Department of Energy Science, Sungkyunkwan University, Suwon 16419, Republic of Korea.
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Ding H, Dong Y, Li S, Pan N, Wang X. Edge optical scattering of two-dimensional materials. OPTICS EXPRESS 2018; 26:7797-7810. [PMID: 29609329 DOI: 10.1364/oe.26.007797] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2018] [Accepted: 03/13/2018] [Indexed: 06/08/2023]
Abstract
Rayleigh scattering has shown powerful abilities to study electron resonances of nanomaterials regardless of the specific shapes. In analogy to Rayleigh scattering, here we demonstrate that edge optical scattering from two-dimensional(2D) materials also has the similar advantage. Our result shows that, in visible spectral range, as long as the lateral size of a 2D sample is larger than 2 μm, the edge scattering intensity distribution of the high-angle scattering in k space is nearly independent of the lateral size and the shape of the 2D samples. The high-angle edge scattering spectra are purely determined by the intrinsic dielectric properties of the 2D materials. As an example, we experimentally verify this feature in single-layer MoS2, in which A and B excitons are clearly detected in the edge scattering spectra, and the scattering images in k space and real space are consistent with our theoretical model. This study shows that the edge scattering is a highly practical and efficient method for optical studies of various 2D materials as well as thin films with clear edges.
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30
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Vacuum level dependent photoluminescence in chemical vapor deposition-grown monolayer MoS 2. Sci Rep 2017; 7:16714. [PMID: 29196652 PMCID: PMC5711928 DOI: 10.1038/s41598-017-15577-1] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Accepted: 10/30/2017] [Indexed: 11/12/2022] Open
Abstract
The stronger photoluminescence (PL) in chemical vapor deposition (CVD) grown monolayer MoS2 has been attributed to its high crystal quality compared with that in mechanically exfoliated (ME) crystal, which is contrary to the cognition that the ME crystal usually have better crystal quality than that of CVD grown one and it is expected with a better optical quality. In this report, the reason of abnormally strong PL spectra in CVD grown monolayer crystal is systematically investigated by studying the in-situ opto-electrical exploration at various environments for both of CVD and ME samples. High resolution transmission electron microscopy is used to investigate their crystal qualities. The stronger PL in CVD grown crystal is due to the high p-doping effect of adsorbates induced rebalance of exciton/trion emission. The first principle calculations are carried out to explore the interaction between adsorbates in ambient and defects sites in MoS2, which is consistent to the experimental phenomenon and further confirm our proposed mechanisms.
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31
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Roy S, Muhammed Ajmal C, Baik S, Kim J. Silver nanoflowers for single-particle SERS with 10 pM sensitivity. NANOTECHNOLOGY 2017; 28:465705. [PMID: 28901949 DOI: 10.1088/1361-6528/aa8c57] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Surface-enhanced Raman scattering (SERS) has received considerable attention as a noninvasive optical sensing technique with ultrahigh sensitivity. While numerous types of metallic particles have been actively investigated as SERS substrates, the development of new SERS agents with high sensitivity and their reliable characterization are still required. Here we report the preparation and characterization of flower-shaped silver (Ag) nanoparticles that exhibit high-sensitivity single-particle SERS performance. Ag nanoflowers (NFs) with bud sizes in the range 220-620 nm were synthesized by the wet synthesis method. The densely packed nanoscale petals with thicknesses in the range 9-22 nm exhibit a large number of hot spots that significantly enhance their plasmonic activity. A single Ag NF particle (530-620 nm) can detect as little as 10-11 M 4-mercaptobenzoic acid, and thus provides a sensitivity three orders of SERS magnitude greater than that of a spherical Ag nanoparticle. The analytical enhancement factors for single Ag NF particles were found to be as high as 8.0 × 109, providing unprecedented high SERS detectivity at the single particle level. Here we present an unambiguous and systematic assessment of the SERS performances of the Ag NFs and demonstrate that they provide highly sensitive sensing platforms by single SERS particle.
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Affiliation(s)
- Shrawan Roy
- IBS Center for Integrated Nanostructure Physics, Institute for Basic Science, Suwon 16419, Republic of Korea. Department of Energy Science, Sungkyunkwan University, Suwon 16419, Republic of Korea
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Park KC, Seo C, Gupta G, Kim J, Lee CY. Efficient Energy Transfer (EnT) in Pyrene- and Porphyrin-Based Mixed-Ligand Metal-Organic Frameworks. ACS APPLIED MATERIALS & INTERFACES 2017; 9:38670-38677. [PMID: 29048158 DOI: 10.1021/acsami.7b14135] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Designing and synthesizing the ordered light-harvesting systems, possessing complementary absorption and energy-transfer process between the chromophores, are essential steps to accomplish successful mimicking of the natural photosynthetic systems. Metal-organic frameworks (MOFs) can be considered as an ideal system to achieve this due to their highly ordered structure, superior synthetic versatility, and tailorable functionality. Herein, we have synthesized the new light-harvesting mixed-ligand MOFs (MLMs, MLM-1-3) via solvothermal reactions between a Zr6 cluster and a mixture of appropriate ratio of 1,3,6,8-tetrakis(p-benzoic acid)pyrene and [5,10,15,20-tetrakis(4-carboxy-phenyl)porphyrinato]-Zn(II) ligands. The identical symmetry and connectivity of the two ligands of the MLMs was the key parameter of successful synthesis as a single MOF form, and the ample overlap between the emission spectrum of pyrene and the absorption spectrum of porphyrin provided the ideal platform to design an efficient-energy transfer (EnT) process within the MLMs. We obtained the nanoscale maps of the fluorescence intensities and lifetimes of microsize MLM grains for unambiguous visualization of EnT phenomena occurring between two ligands in MLMs. Moreover, due to complementary absorption and energy transfer between the two ligands in the MLMs, our MLMs performed as superior photoinduced singlet-oxygen generators, verifying the enhanced light-harvesting properties of the pyrene- and porphyrin-based MLMs.
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Affiliation(s)
| | - Changwon Seo
- Departmentof Energy Science, Sungkyunkwan University , Suwon, 16419, Republic of Korea
| | | | - Jeongyong Kim
- Departmentof Energy Science, Sungkyunkwan University , Suwon, 16419, Republic of Korea
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33
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Molas MR, Nogajewski K, Slobodeniuk AO, Binder J, Bartos M, Potemski M. The optical response of monolayer, few-layer and bulk tungsten disulfide. NANOSCALE 2017; 9:13128-13141. [PMID: 28849844 DOI: 10.1039/c7nr04672c] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We present a comprehensive optical study of thin flakes of tungsten disulfide (WS2) with thickness ranging from mono- to octalayer and in the bulk limit. It is shown that the optical band-gap absorption of monolayer WS2 is governed by competing resonances arising from one neutral and two distinct negatively charged excitons whose contributions to the overall absorption of light vary as a function of temperature and carrier concentration. The photoluminescence response of monolayer WS2 is found to be largely dominated by disorder/impurity- and/or phonon-assisted recombination processes. The indirect band-gap luminescence in multilayer WS2 turns out to be a phonon-mediated process whose energy evolution with the number of layers surprisingly follows a simple model of a two-dimensional confinement. The energy position of the direct band-gap response (A and B resonances) is only weakly dependent on the layer thickness, which underlines an approximate compensation of the effect of the reduction of the exciton binding energy by the shrinkage of the apparent band gap. The A-exciton absorption-type spectra in multilayer WS2 display a non-trivial fine structure which results from the specific hybridization of the electronic states in the vicinity of the K-point of the Brillouin zone. The effects of temperature on the absorption-like and photoluminescence spectra of various WS2 layers are also quantified.
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Affiliation(s)
- Maciej R Molas
- Laboratoire National des Champs Magnétiques Intenses, CNRS-UGA-UPS-INSA-EMFL, 25, avenue des Martyrs, 38042 Grenoble, France.
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Ghimire G, Dhakal KP, Neupane GP, Gi Jo S, Kim H, Seo C, Hee Lee Y, Joo J, Kim J. Optically active charge transfer in hybrids of Alq 3 nanoparticles and MoS 2 monolayer. NANOTECHNOLOGY 2017; 28:185702. [PMID: 28319028 DOI: 10.1088/1361-6528/aa67c7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Organic/inorganic hybrid structures have been widely studied because of their enhanced physical and chemical properties. Monolayers of transition metal dichalcogenides (1L-TMDs) and organic nanoparticles can provide a hybridization configuration between zero- and two-dimensional systems with the advantages of convenient preparation and strong interface interaction. Here, we present such a hybrid system made by dispersing π-conjugated organic (tris (8-hydroxyquinoline) aluminum(III)) (Alq3) nanoparticles (NPs) on 1L-MoS2. Hybrids of Alq3 NP/1L-MoS2 exhibited a two-fold increase in the photoluminescence of Alq3 NPs on 1L-MoS2 and the n-doping effect of 1L-MoS2, and these spectral and electronic modifications were attributed to the charge transfer between Alq3 NPs and 1L-MoS2. Our results suggested that a hybrid of organic NPs/1L-TMD can offer a convenient platform to study the interface interactions between organic and inorganic nano objects and to engineer optoelectronic devices with enhanced performance.
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Affiliation(s)
- Ganesh Ghimire
- IBS Center for Integrated Nanostructure Physics, Institute for Basic Science, Suwon 16419, Republic of Korea. Department of Energy Science, Sungkyunkwan University, Suwon 16419, Republic of Korea
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35
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Tao L, Chen K, Chen Z, Chen W, Gui X, Chen H, Li X, Xu JB. Centimeter-Scale CVD Growth of Highly Crystalline Single-Layer MoS 2 Film with Spatial Homogeneity and the Visualization of Grain Boundaries. ACS APPLIED MATERIALS & INTERFACES 2017; 9:12073-12081. [PMID: 28297598 DOI: 10.1021/acsami.7b00420] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
MoS2 monolayer attracts considerable attention due to its semiconducting nature with a direct bandgap which can be tuned by various approaches. Yet a controllable and low-cost method to produce large-scale, high-quality, and uniform MoS2 monolayer continuous film, which is of crucial importance for practical applications and optical measurements, remains a great challenge. Most previously reported MoS2 monolayer films had limited crystalline sizes, and the high density of grain boundaries inside the films greatly affected the electrical properties. Herein, we demonstrate that highly crystalline MoS2 monolayer film with spatial size up to centimeters can be obtained via a facile chemical vapor deposition method with solid-phase precursors. This growth strategy contains selected precursor and controlled diffusion rate, giving rise to the high quality of the film. The well-defined grain boundaries inside the continuous film, which are invisible under an optical microscope, can be clearly detected in photoluminescence mapping and atomic force microscope phase images, with a low density of ∼0.04 μm-1. Transmission electron microscopy combined with selected area electron diffraction measurements further confirm the high structural homogeneity of the MoS2 monolayer film with large crystalline sizes. Electrical measurements show uniform and promising performance of the transistors made from the MoS2 monolayer film. The carrier mobility remains high at large channel lengths. This work opens a new pathway toward electronic and optical applications, and fundamental growth mechanism as well, of the MoS2 monolayer.
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Affiliation(s)
- Li Tao
- Department of Electronic Engineering and Materials Science and Technology Research Center, The Chinese University of Hong Kong , Shatin, N.T., Hong Kong SAR, China
| | - Kun Chen
- Department of Electronic Engineering and Materials Science and Technology Research Center, The Chinese University of Hong Kong , Shatin, N.T., Hong Kong SAR, China
| | - Zefeng Chen
- Department of Electronic Engineering and Materials Science and Technology Research Center, The Chinese University of Hong Kong , Shatin, N.T., Hong Kong SAR, China
| | | | | | | | - Xinming Li
- Department of Electronic Engineering and Materials Science and Technology Research Center, The Chinese University of Hong Kong , Shatin, N.T., Hong Kong SAR, China
| | - Jian-Bin Xu
- Department of Electronic Engineering and Materials Science and Technology Research Center, The Chinese University of Hong Kong , Shatin, N.T., Hong Kong SAR, China
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36
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Neupane GP, Tran MD, Yun SJ, Kim H, Seo C, Lee J, Han GH, Sood AK, Kim J. Simple Chemical Treatment to n-Dope Transition-Metal Dichalcogenides and Enhance the Optical and Electrical Characteristics. ACS APPLIED MATERIALS & INTERFACES 2017; 9:11950-11958. [PMID: 28303716 DOI: 10.1021/acsami.6b15239] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The optical and electrical properties of monolayer transition-metal dichalcogenides (1L-TMDs) are critically influenced by two dimensionally confined exciton complexes. Although extensive studies on controlling the optical properties of 1L-TMDs through external doping or defect engineering have been carried out, the effects of excess charges, defects, and the populations of exciton complexes on the light emission of 1L-TMDs are not yet fully understood. Here, we present a simple chemical treatment method for n-dope 1L-TMDs, which also enhances their optical and electrical properties. We show that dipping 1Ls of MoS2, WS2, and WSe2, whether exfoliated or grown by chemical vapor deposition, into methanol for several hours can increase the electron density and also can reduce the defects, resulting in the enhancement of their photoluminescence, light absorption, and the carrier mobility. This methanol treatment was effective for both n- and p-type 1L-TMDs, suggesting that the surface restructuring around structural defects by methanol is responsible for the enhancement of optical and electrical characteristics. Our results have revealed a simple process for external doping that can enhance both the optical and electrical properties of 1L-TMDs and help us understand how the exciton emission in 1L-TMDs can be modulated by chemical treatments.
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Affiliation(s)
- Guru P Neupane
- Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS) , Suwon 440-746, Republic of Korea
- Department of Energy Science, Sungkyunkwan University (SKKU) , Suwon 440-746, Republic of Korea
| | - Minh Dao Tran
- Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS) , Suwon 440-746, Republic of Korea
- Department of Energy Science, Sungkyunkwan University (SKKU) , Suwon 440-746, Republic of Korea
| | - Seok Joon Yun
- Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS) , Suwon 440-746, Republic of Korea
- Department of Energy Science, Sungkyunkwan University (SKKU) , Suwon 440-746, Republic of Korea
| | - Hyun Kim
- Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS) , Suwon 440-746, Republic of Korea
- Department of Energy Science, Sungkyunkwan University (SKKU) , Suwon 440-746, Republic of Korea
| | - Changwon Seo
- Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS) , Suwon 440-746, Republic of Korea
- Department of Energy Science, Sungkyunkwan University (SKKU) , Suwon 440-746, Republic of Korea
| | - Jubok Lee
- Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS) , Suwon 440-746, Republic of Korea
- Department of Energy Science, Sungkyunkwan University (SKKU) , Suwon 440-746, Republic of Korea
| | - Gang Hee Han
- Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS) , Suwon 440-746, Republic of Korea
- Department of Energy Science, Sungkyunkwan University (SKKU) , Suwon 440-746, Republic of Korea
| | - A K Sood
- Department of Physics, Indian Institute of Science , Bangalore 560012, India
| | - Jeongyong Kim
- Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS) , Suwon 440-746, Republic of Korea
- Department of Energy Science, Sungkyunkwan University (SKKU) , Suwon 440-746, Republic of Korea
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37
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Manipulation of local optical properties and structures in molybdenum-disulfide monolayers using electric field-assisted near-field techniques. Sci Rep 2017; 7:46004. [PMID: 28378804 PMCID: PMC5380953 DOI: 10.1038/srep46004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Accepted: 03/06/2017] [Indexed: 11/30/2022] Open
Abstract
Remarkable optical properties, such as quantum light emission and large optical nonlinearity, have been observed in peculiar local sites of transition metal dichalcogenide monolayers, and the ability to tune such properties is of great importance for their optoelectronic applications. For that purpose, it is crucial to elucidate and tune their local optical properties simultaneously. Here, we develop an electric field-assisted near-field technique. Using this technique we can clarify and tune the local optical properties simultaneously with a spatial resolution of approximately 100 nm due to the electric field from the cantilever. The photoluminescence at local sites in molybdenum-disulfide (MoS2) monolayers is reversibly modulated, and the inhomogeneity of the charge neutral points and quantum yields is suggested. We successfully etch MoS2 crystals and fabricate nanoribbons using near-field techniques in combination with an electric field. This study creates a way to tune the local optical properties and to freely design the structural shapes of atomic monolayers using near-field optics.
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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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Kim MS, Seo C, Kim H, Lee J, Luong DH, Park JH, Han GH, Kim J. Simultaneous Hosting of Positive and Negative Trions and the Enhanced Direct Band Emission in MoSe2/MoS2 Heterostacked Multilayers. ACS NANO 2016; 10:6211-9. [PMID: 27187667 DOI: 10.1021/acsnano.6b02213] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Heterostacking of layered transition-metal dichalcogenide (LTMD) monolayers (1Ls) offers a convenient way of designing two-dimensional exciton systems. Here we demonstrate the simultaneous hosting of positive trions and negative trions in heterobilayers made by vertically stacking 1L MoSe2 and 1L MoS2. The charge transfer occurring between the 1Ls of MoSe2 and MoS2 converted the polarity of trions in 1L MoSe2 from negative to positive, resulting in the presence of positive trions in the 1L MoSe2 and negative trions in the 1L MoS2 of the same heterostacked bilayer. Significantly enhanced MoSe2 photoluminescence (PL) in the heterostacked bilayers compared to the PL of 1L MoSe2 alone suggests that, unlike other previously reported heterostacked bilayers, direct band transition of 1L MoSe2 in heterobilayer was enhanced after the vertical heterostacking. Moreover, by inserting hexagonal BN monolayers between 1L MoSe2 and 1L MoS2, we were able to adjust the charge transfer to maximize the MoSe2 PL of the heteromultilayers and have achieved a 9-fold increase of the PL emission. The enhanced optical properties of our heterostacked LTMDs suggest the exciting possibility of designing LTMD structures that exploit the superior optical properties of 1L LTMDs.
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Affiliation(s)
- Min Su Kim
- Center for Integrated Nanostructure Physics, Institute for Basic Science, Sungkyunkwan University , Suwon 440-746, Republic of Korea
| | - Changwon Seo
- Center for Integrated Nanostructure Physics, Institute for Basic Science, Sungkyunkwan University , Suwon 440-746, Republic of Korea
- Department of Energy Science, Sungkyunkwan University , Suwon 440-746, Republic of Korea
| | - Hyun Kim
- Center for Integrated Nanostructure Physics, Institute for Basic Science, Sungkyunkwan University , Suwon 440-746, Republic of Korea
- Department of Energy Science, Sungkyunkwan University , Suwon 440-746, Republic of Korea
| | - Jubok Lee
- Center for Integrated Nanostructure Physics, Institute for Basic Science, Sungkyunkwan University , Suwon 440-746, Republic of Korea
- Department of Energy Science, Sungkyunkwan University , Suwon 440-746, Republic of Korea
| | - Dinh Hoa Luong
- Center for Integrated Nanostructure Physics, Institute for Basic Science, Sungkyunkwan University , Suwon 440-746, Republic of Korea
- Department of Energy Science, Sungkyunkwan University , Suwon 440-746, Republic of Korea
| | - Ji-Hoon Park
- Center for Integrated Nanostructure Physics, Institute for Basic Science, Sungkyunkwan University , Suwon 440-746, Republic of Korea
| | - Gang Hee Han
- Center for Integrated Nanostructure Physics, Institute for Basic Science, Sungkyunkwan University , Suwon 440-746, Republic of Korea
| | - Jeongyong Kim
- Center for Integrated Nanostructure Physics, Institute for Basic Science, Sungkyunkwan University , Suwon 440-746, Republic of Korea
- Department of Energy Science, Sungkyunkwan University , Suwon 440-746, Republic of Korea
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Huang YL, Ding Z, Zhang W, Chang YH, Shi Y, Li LJ, Song Z, Zheng YJ, Chi D, Quek SY, Wee ATS. Gap States at Low-Angle Grain Boundaries in Monolayer Tungsten Diselenide. NANO LETTERS 2016; 16:3682-3688. [PMID: 27140667 DOI: 10.1021/acs.nanolett.6b00888] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Two-dimensional (2D) transition metal dichalcogenides (TMDs) have revealed many novel properties of interest to future device applications. In particular, the presence of grain boundaries (GBs) can significantly influence the material properties of 2D TMDs. However, direct characterization of the electronic properties of the GB defects at the atomic scale remains extremely challenging. In this study, we employ scanning tunneling microscopy and spectroscopy to investigate the atomic and electronic structure of low-angle GBs of monolayer tungsten diselenide (WSe2) with misorientation angles of 3-6°. Butterfly features are observed along the GBs, with the periodicity depending on the misorientation angle. Density functional theory calculations show that these butterfly features correspond to gap states that arise in tetragonal dislocation cores and extend to distorted six-membered rings around the dislocation core. Understanding the nature of GB defects and their influence on transport and other device properties highlights the importance of defect engineering in future 2D device fabrication.
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Affiliation(s)
- Yu Li Huang
- Institute of Materials Research & Engineering (IMRE), A*STAR (Agency for Science, Technology and Research) , 2 Fusionopolis Way, Innovis, Singapore 138634, Singapore
- Department of Physics, National University of Singapore , 2 Science Drive 3, Singapore 117551, Singapore
| | - Zijing Ding
- SZU-NUS Collaborative Innovation Center for Optoelectronic Science & Technology, Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, Shenzhen University , Shenzhen 518060, China
- Department of Physics, National University of Singapore , 2 Science Drive 3, Singapore 117551, Singapore
| | - Wenjing Zhang
- SZU-NUS Collaborative Innovation Center for Optoelectronic Science & Technology, Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, Shenzhen University , Shenzhen 518060, China
| | - Yung-Huang Chang
- Department of Electrophysics, National Chiao Tung University , Hsinchu 300, Taiwan
| | - Yumeng Shi
- Physical Sciences and Engineering, King Abdullah University of Science and Technology , Thuwal 23955-6900, Saudi Arabia
| | - Lain-Jong Li
- Physical Sciences and Engineering, King Abdullah University of Science and Technology , Thuwal 23955-6900, Saudi Arabia
| | - Zhibo Song
- Institute of Materials Research & Engineering (IMRE), A*STAR (Agency for Science, Technology and Research) , 2 Fusionopolis Way, Innovis, Singapore 138634, Singapore
- Department of Physics, National University of Singapore , 2 Science Drive 3, Singapore 117551, Singapore
| | - Yu Jie Zheng
- Department of Physics, National University of Singapore , 2 Science Drive 3, Singapore 117551, Singapore
| | - Dongzhi Chi
- Institute of Materials Research & Engineering (IMRE), A*STAR (Agency for Science, Technology and Research) , 2 Fusionopolis Way, Innovis, Singapore 138634, Singapore
| | - Su Ying Quek
- Department of Physics, National University of Singapore , 2 Science Drive 3, Singapore 117551, Singapore
- Centre for Advanced 2D Materials, National University of Singapore , Block S14, Level 6, 6 Science Drive 2, Singapore 117546, Singapore
| | - Andrew T S Wee
- Department of Physics, National University of Singapore , 2 Science Drive 3, Singapore 117551, Singapore
- Centre for Advanced 2D Materials, National University of Singapore , Block S14, Level 6, 6 Science Drive 2, Singapore 117546, Singapore
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Su W, Kumar N, Mignuzzi S, Crain J, Roy D. Nanoscale mapping of excitonic processes in single-layer MoS2 using tip-enhanced photoluminescence microscopy. NANOSCALE 2016; 8:10564-9. [PMID: 27152366 DOI: 10.1039/c5nr07378b] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
In two-dimensional (2D) semiconductors, photoluminescence originating from recombination processes involving neutral electron-hole pairs (excitons) and charged complexes (trions) is strongly affected by the localized charge transfer due to inhomogeneous interactions with the local environment and surface defects. Herein, we demonstrate the first nanoscale mapping of excitons and trions in single-layer MoS2 using the full spectral information obtained via tip-enhanced photoluminescence (TEPL) microscopy along with tip-enhanced Raman spectroscopy (TERS) imaging of a 2D flake. Finally, we show the mapping of the PL quenching centre in single-layer MoS2 with an unprecedented spatial resolution of 20 nm. In addition, our research shows that unlike in aperture-scanning near field microscopy, preferential exciton emission mapping at the nanoscale using TEPL and Raman mapping using TERS can be obtained simultaneously using this method that can be used to correlate the structural and excitonic properties.
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Affiliation(s)
- Weitao Su
- Institute of Materials Physics, Hangzhou Dianzi University, 310018, Hangzhou, China and Key Laboratory of RF Circuits and Systems (Hangzhou Dianzi University), Ministry of Education of China, China
| | - Naresh Kumar
- National Physical Laboratory, Hampton Road, Teddington, Middlesex, TW11 0LW, UK.
| | - Sandro Mignuzzi
- National Physical Laboratory, Hampton Road, Teddington, Middlesex, TW11 0LW, UK.
| | - Jason Crain
- National Physical Laboratory, Hampton Road, Teddington, Middlesex, TW11 0LW, UK. and School of Physics and Astronomy, University of Edinburgh, James Clerk Maxwell Building, Peter Guthrie Tait Road, Edinburgh, EH9 3FD, UK
| | - Debdulal Roy
- National Physical Laboratory, Hampton Road, Teddington, Middlesex, TW11 0LW, UK.
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Park KD, Khatib O, Kravtsov V, Clark G, Xu X, Raschke MB. Hybrid Tip-Enhanced Nanospectroscopy and Nanoimaging of Monolayer WSe2 with Local Strain Control. NANO LETTERS 2016; 16:2621-7. [PMID: 26937992 DOI: 10.1021/acs.nanolett.6b00238] [Citation(s) in RCA: 91] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Many classes of two-dimensional (2D) materials have emerged as potential platforms for novel electronic and optical devices. However, their physical properties are strongly influenced by nanoscale heterogeneities in the form of edges, twin boundaries, and nucleation sites. Using combined tip-enhanced Raman scattering and photoluminescence (PL) nanospectroscopy and nanoimaging, we study the associated effects on the excitonic properties in monolayer WSe2 grown by physical vapor deposition. With ∼15 nm spatial resolution, we resolve nanoscale correlations of PL spectral intensity and shifts with crystal edges and internal twin boundaries associated with the expected exciton diffusion length. Through an active atomic force tip interaction we can control the crystal strain on the nanoscale and tune the local bandgap in reversible (up to 24 meV shift) and irreversible (up to 48 meV shift) fashion. This allows us to distinguish the effect of strain from the dominant influence of defects on the PL modification at the different structural heterogeneities. Hybrid nano-optical spectroscopy and imaging with nanomechanical strain control thus enables the systematic study of the coupling of structural and mechanical degrees of freedom to the nanoscale electronic and optical properties in layered 2D materials.
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Affiliation(s)
- Kyoung-Duck Park
- Department of Physics, Department of Chemistry, and JILA, University of Colorado , Boulder, Colorado 80309, United States
| | - Omar Khatib
- Department of Physics, Department of Chemistry, and JILA, University of Colorado , Boulder, Colorado 80309, United States
| | - Vasily Kravtsov
- Department of Physics, Department of Chemistry, and JILA, University of Colorado , Boulder, Colorado 80309, United States
| | - Genevieve Clark
- Department of Physics, Department of Materials Science and Engineering, University of Washington , Seattle, Washington 98195, United States
| | - Xiaodong Xu
- Department of Physics, Department of Materials Science and Engineering, University of Washington , Seattle, Washington 98195, United States
| | - Markus B Raschke
- Department of Physics, Department of Chemistry, and JILA, University of Colorado , Boulder, Colorado 80309, United States
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Kim MS, Yun SJ, Lee Y, Seo C, Han GH, Kim KK, Lee YH, Kim J. Biexciton Emission from Edges and Grain Boundaries of Triangular WS₂ Monolayers. ACS NANO 2016; 10:2399-405. [PMID: 26758415 DOI: 10.1021/acsnano.5b07214] [Citation(s) in RCA: 106] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Monolayer tungsten disulfides (WS2) constitute a high quantum yield two-dimensional (2D) system, and can be synthesized on a large area using chemical vapor deposition (CVD), suggesting promising nanophotonics applications. However, spatially nonuniform photoluminescence (PL) intensities and peak wavelengths observed in single WS2 grains have puzzled researchers, with the origins of variation in relative contributions of excitons, trions, and biexcitons to the PL emission not well understood. Here, we present nanoscale PL and Raman spectroscopy images of triangular CVD-grown WS2 monolayers of different sizes, with these images obtained under different temperatures and values of excitation power. Intense PL emissions were observed around the edges of individual WS2 grains and the grain boundaries between partly merged WS2 grains. The predominant origin of the main PL emission from these regions changed from neutral excitons to trions and biexcitons with increasing laser excitation power, with biexcitons completely dominating the PL emission for the high-power condition. The intense PL emission and the preferential formation of biexcitons in the edges and grain boundaries of monolayer WS2 were attributed to larger population of charge carriers caused by the excessive incorporation of growth promoters during the CVD, suggesting positive roles of excessive carriers in the PL efficiency of TMD monolayers. Our comprehensive nanoscale spectroscopic investigation sheds light on the dynamic competition between exciton complexes occurring in monolayer WS2, suggesting a rich variety of ways to engineer new nanophotonic functions using 2D transition metal dichalcogenide monolayers.
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Affiliation(s)
- Min Su Kim
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Sungkyunkwan University , Suwon 440-746, Republic of Korea
| | - Seok Joon Yun
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Sungkyunkwan University , Suwon 440-746, Republic of Korea
- Department of Energy Science, Sungkyunkwan University , Suwon 440-746, Republic of Korea
| | - Yongjun Lee
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Sungkyunkwan University , Suwon 440-746, Republic of Korea
- Department of Energy Science, Sungkyunkwan University , Suwon 440-746, Republic of Korea
| | - Changwon Seo
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Sungkyunkwan University , Suwon 440-746, Republic of Korea
- Department of Energy Science, Sungkyunkwan University , Suwon 440-746, Republic of Korea
| | - Gang Hee Han
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Sungkyunkwan University , Suwon 440-746, Republic of Korea
| | - Ki Kang Kim
- Department of Energy and Materials Engineering, Dongguk University-Seoul , Seoul 100-715, Republic of Korea
| | - Young Hee Lee
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Sungkyunkwan University , Suwon 440-746, Republic of Korea
- Department of Energy Science, Sungkyunkwan University , Suwon 440-746, Republic of Korea
| | - Jeongyong Kim
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Sungkyunkwan University , Suwon 440-746, Republic of Korea
- Department of Energy Science, Sungkyunkwan University , Suwon 440-746, Republic of Korea
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