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Sabbaghi S, Hosseinian E, Bazargan V. Strain-Assisted Phase Transformation in Two-Dimensional Transition-Metal Dichalcogenides. ACS APPLIED MATERIALS & INTERFACES 2024; 16:22676-22688. [PMID: 38632875 DOI: 10.1021/acsami.4c01503] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/19/2024]
Abstract
Two-dimensional polymorphic transition-metal dichalcogenides have drawn attention for their diverse applications. This work explores the complex interplay between strain-induced phase transformation and crack growth behavior in annealed nanocrystalline MoS2. Employing molecular dynamics (MD) simulations, this research focuses on the effect of grain size, misorientation, and annealing on phase evolution and their effects on the mechanical behavior of MoS2. First, examining phase transformation in monocrystalline MoS2 under various stress states reveals distinct behaviors depending on the initial phase (1T or 2H) and crystallographic orientation with respect to loading directions. Notably, transformation from a layered hexagonal to a body-centered tetragonal structure is more noticeable when strain in a zigzag direction is applied to the 1T sample. As such, single crystalline MoS2 with a 1T phase exhibits a 16% lower fracture stress in the armchair direction compared to that with a 2H phase. On the other hand, the 1T phase shows a 5% higher phonon lifetime compared to the 2H phase with similar phonon group velocities. Next, the influence of thermal energy and mechanical stress on the phase transformation of nanocrystalline MoS2 is investigated through annealing and quenching cycles, uncovering 60 and 44% irreversibility of phase transformation for an average grain size of 3 and 11 nm, respectively. Besides, the evolution of nanocrystalline samples with different initial phases and grain sizes is studied under uniaxial and biaxial stress. This study shows an inverse pseudo-Hall-Petch effect with exponents of 0.11 and 0.09 for 2H and 1T, respectively. The study reveals that phase transformation can occur concurrently with crack initiation and propagation with the 1T phase exhibiting a 19% lower grain size sensitivity of fracture stress compared to the 2H phase.
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Affiliation(s)
- Soroush Sabbaghi
- Department of Mechanical Engineering, University of Tehran, P.O. Box 11155-4563, Tehran 14399-57131, Iran
| | - Ehsan Hosseinian
- Department of Mechanical Engineering, University of Tehran, P.O. Box 11155-4563, Tehran 14399-57131, Iran
| | - Vahid Bazargan
- Department of Mechanical Engineering, University of Tehran, P.O. Box 11155-4563, Tehran 14399-57131, Iran
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2
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Li S, Lin J, Chen Y, Luo Z, Cheng H, Liu F, Zhang J, Wang S. Growth Anisotropy and Morphology Evolution of Line Defects in Monolayer MoS 2 : Atomic-Level Observation, Large-Scale Statistics, and Mechanism Understanding. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2024; 20:e2303511. [PMID: 37749964 DOI: 10.1002/smll.202303511] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Revised: 08/25/2023] [Indexed: 09/27/2023]
Abstract
Understanding the growth behavior and morphology evolution of defects in 2D transition metal dichalcogenides is significant for the performance tuning of nanoelectronic devices. Here, the low-voltage aberration-corrected transmission electron microscopy with an in situ heating holder and a fast frame rate camera to investigate the sulfur vacancy lines in monolayer MoS2 is applied. Vacancy concentration-dependent growth anisotropy is discovered, displaying first lengthening and then broadening of line defects as the vacancy densifies. With the temperature increase from 20 °C to 800 °C, the defect morphology evolves from a dense triangular network to an ultralong linear structure due to the temperature-sensitive vacancy migration process. Atomistic dynamics of line defect reconstruction on the millisecond time scale are also captured. Density functional theory calculations, Monte Carlo simulation, and configurational force analysis are implemented to understand the growth and reconstruction mechanisms at relevant time and length scales. Throughout the work, high-resolution imaging is closely combined with quantitative analysis of images involving thousands of atoms so that the atomic-level structure and the large-area statistical rules are obtained simultaneously. The work provides new ideas for balancing the accuracy and universality of discoveries in the TEM study and will be helpful to the controlled sculpture of nanomaterials.
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Affiliation(s)
- Shouheng Li
- Science and Technology on Advanced Ceramic Fibers and Composites Laboratory, College of Aerospace Science and Engineering, National University of Defense Technology, Changsha, 410073, P. R. China
- Center for Nanochemistry, Beijing Science and Engineering Center for Nanocarbons, Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, P. R. China
| | - Jinguo Lin
- State Key Laboratory of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Sciences, Beijing, 100190, P. R. China
- School of Engineering Sciences, University of Chinese Academy of Sciences, Beijing, 100049, P.R. China
| | - Yun Chen
- Science and Technology on Advanced Ceramic Fibers and Composites Laboratory, College of Aerospace Science and Engineering, National University of Defense Technology, Changsha, 410073, P. R. China
| | - Zheng Luo
- Science and Technology on Advanced Ceramic Fibers and Composites Laboratory, College of Aerospace Science and Engineering, National University of Defense Technology, Changsha, 410073, P. R. China
| | - Haifeng Cheng
- Science and Technology on Advanced Ceramic Fibers and Composites Laboratory, College of Aerospace Science and Engineering, National University of Defense Technology, Changsha, 410073, P. R. China
| | - Feng Liu
- State Key Laboratory of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Sciences, Beijing, 100190, P. R. China
- School of Engineering Sciences, University of Chinese Academy of Sciences, Beijing, 100049, P.R. China
| | - Jin Zhang
- Center for Nanochemistry, Beijing Science and Engineering Center for Nanocarbons, Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, P. R. China
- School of Advanced Materials, Peking University Shenzhen Graduate School, Shenzhen, 518055, P. R. China
| | - Shanshan Wang
- Science and Technology on Advanced Ceramic Fibers and Composites Laboratory, College of Aerospace Science and Engineering, National University of Defense Technology, Changsha, 410073, P. R. China
- School of Advanced Materials, Peking University Shenzhen Graduate School, Shenzhen, 518055, P. R. China
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3
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Li T, Miao J, Fu X, Song B, Cai B, Ge X, Zhou X, Zhou P, Wang X, Jariwala D, Hu W. Reconfigurable, non-volatile neuromorphic photovoltaics. NATURE NANOTECHNOLOGY 2023; 18:1303-1310. [PMID: 37474683 DOI: 10.1038/s41565-023-01446-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Accepted: 06/08/2023] [Indexed: 07/22/2023]
Abstract
The neural network image sensor-which mimics neurobiological functions of the human retina-has recently been demonstrated to simultaneously sense and process optical images. However, highly tunable responsivity concurrent with non-volatile storage of image data in the neural network would allow a transformative leap in compactness and function of these artificial neural networks. Here, we demonstrate a reconfigurable and non-volatile neuromorphic device based on two-dimensional semiconducting metal sulfides that is concurrently a photovoltaic detector. The device is based on a metal-semiconductor-metal (MSM) two-terminal structure with pulse-tunable sulfur vacancies at the M-S junctions. By modulating sulfur vacancy concentrations, the polarities of short-circuit photocurrent can be changed with multiple stable magnitudes. The bias-induced motion of sulfur vacancies leads to highly reconfigurable responsivities by dynamically modulating the Schottky barriers. A convolutional neuromorphic network is finally designed for image processing and object detection using the same device. The results demonstrated that neuromorphic photodetectors can be the key components of visual perception hardware.
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Affiliation(s)
- Tangxin Li
- State Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Jinshui Miao
- State Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai, China.
- University of Chinese Academy of Sciences, Beijing, China.
| | - Xiao Fu
- State Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Bo Song
- Institute of Intelligent Machines, HFIPS, Chinese Academy of Sciences, Hefei, China
| | - Bin Cai
- Institute of Intelligent Machines, HFIPS, Chinese Academy of Sciences, Hefei, China
| | - Xun Ge
- State Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai, China
| | - Xiaohao Zhou
- State Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Peng Zhou
- School of Microelectronics, Fudan University, Shanghai, China
| | - Xinran Wang
- School of Electronic Science and Engineering, Nanjing University, Nanjing, China
| | - Deep Jariwala
- Department of Electrical and Systems Engineering, University of Pennsylvania, Philadelphia, PA, USA.
| | - Weida Hu
- State Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai, China.
- University of Chinese Academy of Sciences, Beijing, China.
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4
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Xiao Y, Xiong C, Chen MM, Wang S, Fu L, Zhang X. Structure modulation of two-dimensional transition metal chalcogenides: recent advances in methodology, mechanism and applications. Chem Soc Rev 2023; 52:1215-1272. [PMID: 36601686 DOI: 10.1039/d1cs01016f] [Citation(s) in RCA: 18] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Together with the development of two-dimensional (2D) materials, transition metal dichalcogenides (TMDs) have become one of the most popular series of model materials for fundamental sciences and practical applications. Due to the ever-growing requirements of customization and multi-function, dozens of modulated structures have been introduced in TMDs. In this review, we present a systematic and comprehensive overview of the structure modulation of TMDs, including point, linear and out-of-plane structures, following and updating the conventional classification for silicon and related bulk semiconductors. In particular, we focus on the structural characteristics of modulated TMD structures and analyse the corresponding root causes. We also summarize the recent progress in modulating methods, mechanisms, properties and applications based on modulated TMD structures. Finally, we demonstrate challenges and prospects in the structure modulation of TMDs and forecast potential directions about what and how breakthroughs can be achieved.
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Affiliation(s)
- Yao Xiao
- Collaborative Innovation Centre for Advanced Organic Chemical Materials Co-Constructed by the Province and Ministry, Ministry of Education Key Laboratory for the Synthesis and Application of Organic Functional Molecules, College of Chemistry and Chemical Engineering, Hubei University, Wuhan 430062, P. R. China.
| | - Chengyi Xiong
- Collaborative Innovation Centre for Advanced Organic Chemical Materials Co-Constructed by the Province and Ministry, Ministry of Education Key Laboratory for the Synthesis and Application of Organic Functional Molecules, College of Chemistry and Chemical Engineering, Hubei University, Wuhan 430062, P. R. China.
| | - Miao-Miao Chen
- Collaborative Innovation Centre for Advanced Organic Chemical Materials Co-Constructed by the Province and Ministry, Ministry of Education Key Laboratory for the Synthesis and Application of Organic Functional Molecules, College of Chemistry and Chemical Engineering, Hubei University, Wuhan 430062, P. R. China.
| | - Shengfu Wang
- Collaborative Innovation Centre for Advanced Organic Chemical Materials Co-Constructed by the Province and Ministry, Ministry of Education Key Laboratory for the Synthesis and Application of Organic Functional Molecules, College of Chemistry and Chemical Engineering, Hubei University, Wuhan 430062, P. R. China.
| | - Lei Fu
- The Institute for Advanced Studies (IAS), Wuhan University, Wuhan 430072, P. R. China. .,College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, P. R. China.
| | - Xiuhua Zhang
- Collaborative Innovation Centre for Advanced Organic Chemical Materials Co-Constructed by the Province and Ministry, Ministry of Education Key Laboratory for the Synthesis and Application of Organic Functional Molecules, College of Chemistry and Chemical Engineering, Hubei University, Wuhan 430062, P. R. China.
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5
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Roccapriore KM, Boebinger MG, Dyck O, Ghosh A, Unocic RR, Kalinin SV, Ziatdinov M. Probing Electron Beam Induced Transformations on a Single-Defect Level via Automated Scanning Transmission Electron Microscopy. ACS NANO 2022; 16:17116-17127. [PMID: 36206357 DOI: 10.1021/acsnano.2c07451] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
A robust approach for real-time analysis of the scanning transmission electron microscopy (STEM) data streams, based on ensemble learning and iterative training (ELIT) of deep convolutional neural networks, is implemented on an operational microscope, enabling the exploration of the dynamics of specific atomic configurations under electron beam irradiation via an automated experiment in STEM. Combined with beam control, this approach allows studying beam effects on selected atomic groups and chemical bonds in a fully automated mode. Here, we demonstrate atomically precise engineering of single vacancy lines in transition metal dichalcogenides and the creation and identification of topological defects in graphene. The ELIT-based approach facilitates direct on-the-fly analysis of the STEM data and engenders real-time feedback schemes for probing electron beam chemistry, atomic manipulation, and atom by atom assembly.
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Affiliation(s)
- Kevin M Roccapriore
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee37831, United States
| | - Matthew G Boebinger
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee37831, United States
| | - Ondrej Dyck
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee37831, United States
| | - Ayana Ghosh
- Computational Sciences and Engineering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee37831, United States
| | - Raymond R Unocic
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee37831, United States
| | - Sergei V Kalinin
- Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee37916, United States
| | - Maxim Ziatdinov
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee37831, United States
- Computational Sciences and Engineering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee37831, United States
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6
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Sun Y, Xu S, Xu Z, Tian J, Bai M, Qi Z, Niu Y, Aung HH, Xiong X, Han J, Lu C, Yin J, Wang S, Chen Q, Tenne R, Zak A, Guo Y. Mesoscopic sliding ferroelectricity enabled photovoltaic random access memory for material-level artificial vision system. Nat Commun 2022; 13:5391. [PMID: 36104456 PMCID: PMC9474805 DOI: 10.1038/s41467-022-33118-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2022] [Accepted: 09/01/2022] [Indexed: 01/18/2023] Open
Abstract
Intelligent materials with adaptive response to external stimulation lay foundation to integrate functional systems at the material level. Here, with experimental observation and numerical simulation, we report a delicate nano-electro-mechanical-opto-system naturally embedded in individual multiwall tungsten disulfide nanotubes, which generates a distinct form of in-plane van der Waals sliding ferroelectricity from the unique combination of superlubricity and piezoelectricity. The sliding ferroelectricity enables programmable photovoltaic effect using the multiwall tungsten disulfide nanotube as photovoltaic random-access memory. A complete “four-in-one” artificial vision system that synchronously achieves full functions of detecting, processing, memorizing, and powering is integrated into the nanotube devices. Both labeled supervised learning and unlabeled reinforcement learning algorithms are executable in the artificial vision system to achieve self-driven image recognition. This work provides a distinct strategy to create ferroelectricity in van der Waals materials, and demonstrates how intelligent materials can push electronic system integration at the material level. Intelligent materials change their properties under external stimuli, integrating functionalities at the matter level. Here, Guo et al. report an artificial vision system based on the memory effect produced by sliding ferroelectricity in multiwalled tungsten disulfide nanotubes.
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7
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Liu X, Hou Y, Tang M, Wang L. Atom elimination strategy for MoS2 nanosheets to enhance photocatalytic hydrogen evolution. CHINESE CHEM LETT 2022. [DOI: 10.1016/j.cclet.2022.05.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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8
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Hong J, Chen X, Li P, Koshino M, Li S, Xu H, Hu Z, Ding F, Suenaga K. Multiple 2D Phase Transformations in Monolayer Transition Metal Chalcogenides. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022; 34:e2200643. [PMID: 35307877 DOI: 10.1002/adma.202200643] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Revised: 03/09/2022] [Indexed: 06/14/2023]
Abstract
Phase transformation lies at the heart of materials science because it allows for the control of structural phases of solids with desired properties. It has long been a challenge to manipulate phase transformations in crystals at the nanoscale with designed interfaces and compositions. Here in situ electron microscopy is employed to fabricate novel 2D phases with different stoichiometries in monolayer MoS2 and MoSe2 . The multiphase transformations: MoS2 → Mo4 S6 and MoSe2 → Mo6 Se6 which are highly localized with atomically sharp boundaries are observed. Their atomic mechanisms are determined as chalcogen 2H ↔ 1T sliding, cation shift, and commensurate lattice reconstructions, resulting in decreasing direct bandgaps and even a semiconductor-metal transition. These results will be a paradigm for the manipulation of multiphase heterostructures with controlled compositions and sharp interfaces, which will guide the future phase engineered electronics and optoelectronics of metal chalcogenides.
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Affiliation(s)
- Jinhua Hong
- Nanomaterials Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, 305-8565, Japan
| | - Xi Chen
- Center for Joint Quantum Studies and Department of Physics, Institute of Science, Tianjin University, Tianjin, 300350, China
| | - Pai Li
- Center for Multidimensional Carbon Materials (CMCM), Institute for Basic Science (IBS), Ulsan, 689-798, Republic of Korea
| | - Masanori Koshino
- Nanomaterials Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, 305-8565, Japan
| | - Shisheng Li
- International Center for Young Scientists (ICYS), National Institute for Materials Science (NIMS), Tsukuba, 305-0044, Japan
| | - Hua Xu
- Key Laboratory of Applied Surface and Colloid Chemistry, School of Materials Science and Engineering, Shaanxi Normal University, Xi'an, 710119, China
| | - Zhixin Hu
- Center for Joint Quantum Studies and Department of Physics, Institute of Science, Tianjin University, Tianjin, 300350, China
| | - Feng Ding
- Center for Multidimensional Carbon Materials (CMCM), Institute for Basic Science (IBS), Ulsan, 689-798, Republic of Korea
- School of Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan, 689-798, Republic of Korea
| | - Kazu Suenaga
- Nanomaterials Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, 305-8565, Japan
- The Institute of Scientific and Industrial Research (ISIR-SANKEN), Osaka University, Osaka, 567-0047, Japan
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9
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Chen J, Zhou J, Xu W, Wen Y, Liu Y, Warner JH. Atomic-Level Dynamics of Point Vacancies and the Induced Stretched Defects in 2D Monolayer PtSe 2. NANO LETTERS 2022; 22:3289-3297. [PMID: 35389659 DOI: 10.1021/acs.nanolett.1c04275] [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
Monolayer PtSe2 holds great potential in extending 2D devices functionality, but their atomic-level-defect study is still limited. Here, we investigate the atomic structures of lattice imperfections from point to stretched 1D defects in 1T-PtSe2 monolayers, using annular dark-field scanning transmission electron microscopy (ADF-STEM). We show Se vacancies (VSe) have preferential sites with high beam-induced mobility. Diverse divacancies form with paired VSe. We found stretched linear defects triggered by dynamics of VSe that altered strain fields, distinct from the line vacancies in 2H-phase 2D materials. The paired VSe stability and formation possibility of vacancy lines are evaluated by density functional theory. Lower sputtering energy in PtSe2 than that in MoS2 can cause larger possibility of atomic loss compared to diffusion required for creating VSe lines. This provides atomic insights into the defects in 1T-PtSe2 and shows how a deviated 1D structure is embedded in a 2D system without losing atom lines.
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Affiliation(s)
- Jun Chen
- Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, United Kingdom
| | - Jiang Zhou
- Materials Graduate Program, Texas Materials Institute, The University of Texas at Austin, 204 East Dean Keeton Street, Austin, Texas 78712, United States
- Key Laboratory of Materials Modification by Laser, Ion and Electron Beams, Dalian University of Technology, Ministry of Education, Dalian 116024, China
| | - Wenshuo Xu
- Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, United Kingdom
| | - Yi Wen
- Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, United Kingdom
| | - Yuanyue Liu
- Materials Graduate Program, Texas Materials Institute, The University of Texas at Austin, 204 East Dean Keeton Street, Austin, Texas 78712, United States
| | - Jamie H Warner
- Materials Graduate Program, Texas Materials Institute, The University of Texas at Austin, 204 East Dean Keeton Street, Austin, Texas 78712, United States
- Walker Department of Mechanical Engineering, The University of Texas at Austin, Austin, Texas 78712, United States
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10
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Verma D, Kumar P, Mukherjee S, Thakur D, Singh CV, Balakrishnan V. Interplay between Thermal Stress and Interface Binding on Fracture of WS 2 Monolayer with Triangular Voids. ACS APPLIED MATERIALS & INTERFACES 2022; 14:16876-16884. [PMID: 35353490 DOI: 10.1021/acsami.2c00901] [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
The defect engineering of two-dimensional (2D) materials has become a pivotal strategy for tuning the electrical and optical properties of the material. However, the reliable application of these atomically thin materials in practical devices require careful control of structural defects to avoid premature failure. Herein, a systematic investigation is presented to delineate the complex interactions among structural defects, the role of thermal mismatch between WS2 monolayer and different substrates, and their consequent effect on the fracture behavior of the monolayer. Detailed microscopic and Raman/PL spectroscopic observations enabled a direct correlation between thermal mismatch stress and crack patterns originating from the corner of faceted voids in the WS2 monolayer. Aberration-corrected STEM-HAADF imaging reveals the tensile strain localization around the faceted void corners. Density functional theory (DFT) simulations on interfacial interaction between the substrate (Silicon and sapphire -Al2O3) and monolayer WS2 revealed a binding energy between WS2 and Si substrate is 20 times higher than that with a sapphire substrate. This increased interfacial interaction in WS2 and substrate-aided thermal mismatch stress arising due to difference in thermal expansion coefficient to a maximum extent leading to fracture in monolayer WS2. Finite element simulations revealed the stress distribution near the void in the WS2 monolayer, where the maximum stress was concentrated at the void tip.
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Affiliation(s)
- Divya Verma
- School of Engineering, Indian Institute of Technology, Mandi, Himachal Pradesh 175075, India
| | - Pawan Kumar
- School of Engineering, Indian Institute of Technology, Mandi, Himachal Pradesh 175075, India
- Department of Electrical and System Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Sankha Mukherjee
- Department of Materials Science and Engineering, University of Toronto, Toronto, Ontario M5S 3E4, Canada
- Department of Metallurgical and Materials Engineering, Indian Institute of Technology, Kharagpur, West Bengal 721302, India
| | - Deepa Thakur
- School of Engineering, Indian Institute of Technology, Mandi, Himachal Pradesh 175075, India
| | - Chandra Veer Singh
- Department of Materials Science and Engineering, University of Toronto, Toronto, Ontario M5S 3E4, Canada
| | - Viswanath Balakrishnan
- School of Engineering, Indian Institute of Technology, Mandi, Himachal Pradesh 175075, India
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11
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Tseng YT, Lu LS, Shen FC, Wang CH, Sung HY, Chang WH, Wu WW. In Situ Atomic-Scale Observation of Monolayer MoS 2 Devices under High-Voltage Biasing via Transmission Electron Microscopy. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2022; 18:e2106411. [PMID: 34995002 DOI: 10.1002/smll.202106411] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2021] [Revised: 11/27/2021] [Indexed: 06/14/2023]
Abstract
2D materials have great potential for not only device scaling but also various applications. To prompt the development of 2D electronics and optoelectronics, a better understanding of the limitation of materials is essential. Material failure caused by bias can lead to variations in device behavior and even electrical breakdown. In this study, the structural evolution of monolayer MoS2 with high bias is revealed via in situ transmission electron microscopy at the atomic scale. The biasing process is recorded and studied with the aid of aberration-corrected scanning transmission electron microscopy. The effects of electron beam irradiation and biasing are also discussed through the combination of experiments and theory. It is found that the Mo nanoclusters result from disintegration of MoS2 and sulfur depletion, which are induced by Joule heating. The thermal stress can also damage the MoS2 layer and form long cracks in both in situ and ex situ biasing cases. Investigation of the results obtained with different applied voltages helps to further verify the mechanism of evolution and provide a comprehensive study of the function of biasing.
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Affiliation(s)
- Yi-Tang Tseng
- Department of Materials Science and Engineering, National Yang Ming Chiao Tung University, No. 1001, University Rd., East Dist., Hsinchu City, 30010, Taiwan
| | - Li-Syuan Lu
- Department of Electrophysics, National Yang Ming Chiao Tung University, No. 1001, University Rd., East Dist., Hsinchu City, 30010, Taiwan
| | - Fang-Chun Shen
- Department of Materials Science and Engineering, National Yang Ming Chiao Tung University, No. 1001, University Rd., East Dist., Hsinchu City, 30010, Taiwan
| | - Che-Hung Wang
- Department of Materials Science and Engineering, National Yang Ming Chiao Tung University, No. 1001, University Rd., East Dist., Hsinchu City, 30010, Taiwan
| | - Hsin-Ya Sung
- Department of Materials Science and Engineering, National Yang Ming Chiao Tung University, No. 1001, University Rd., East Dist., Hsinchu City, 30010, Taiwan
| | - Wen-Hao Chang
- Department of Electrophysics, National Yang Ming Chiao Tung University, No. 1001, University Rd., East Dist., Hsinchu City, 30010, Taiwan
- Research Center for Applied Sciences, Academia Sinica, No. 128, Sec. 2, Academia Rd., Nangang Dist., Taipei City, 11529, Taiwan
| | - Wen-Wei Wu
- Department of Materials Science and Engineering, National Yang Ming Chiao Tung University, No. 1001, University Rd., East Dist., Hsinchu City, 30010, Taiwan
- Center for the Intelligent Semiconductor Nano-system Technology Research, National Yang Ming Chiao Tung University, No. 1001, University Rd., East Dist., Hsinchu City, 30010, Taiwan
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12
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de Graaf S, Ahmadi M, Lazić I, Bosch EGT, Kooi BJ. Imaging atomic motion of light elements in 2D materials with 30 kV electron microscopy. NANOSCALE 2021; 13:20683-20691. [PMID: 34878478 DOI: 10.1039/d1nr06614e] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Scanning transmission electron microscopy (STEM) is the most widespread adopted tool for atomic scale characterization of two-dimensional (2D) materials. However, damage free imaging of 2D materials with electrons has remained problematic even with powerful low-voltage 60 kV-microscopes. An additional challenge is the observation of light elements in combination with heavy elements, particularly when recording fast dynamical phenomena. Here, we demonstrate that 2D WS2 suffers from electron radiation damage during 30 kV-STEM imaging, and we capture beam-induced defect dynamics in real-time by atomic electrostatic potential imaging using integrated differential phase contrast (iDPC)-STEM. The fast imaging of atomic electrostatic potentials with iDPC-STEM reveals the presence and motion of single sulfur atoms near defects and edges in WS2 that are otherwise invisible at the same imaging dose at 30 kV with conventional annular dark-field STEM, and has a vast speed and data processing advantage over electron detector camera based STEM techniques like electron ptychography.
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Affiliation(s)
- Sytze de Graaf
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands.
| | - Majid Ahmadi
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands.
| | - Ivan Lazić
- Thermo Fisher Scientific, Achtseweg Noord 5, 5651 GG Eindhoven, The Netherlands
| | - Eric G T Bosch
- Thermo Fisher Scientific, Achtseweg Noord 5, 5651 GG Eindhoven, The Netherlands
| | - Bart J Kooi
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands.
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13
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Fujisawa K, Carvalho BR, Zhang T, Perea-López N, Lin Z, Carozo V, Ramos SLLM, Kahn E, Bolotsky A, Liu H, Elías AL, Terrones M. Quantification and Healing of Defects in Atomically Thin Molybdenum Disulfide: Beyond the Controlled Creation of Atomic Defects. ACS NANO 2021; 15:9658-9669. [PMID: 33754710 DOI: 10.1021/acsnano.0c10897] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Atomically thin 2D materials provide an opportunity to investigate the atomic-scale details of defects introduced by particle irradiation. Once the atomic configuration of defects and their spatial distribution are revealed, the details of the mesoscopic phenomena can be unveiled. In this work, we created atomically small defects by controlled irradiation of gallium ions with doses ranging from 4.94 × 1012 to 4.00 × 1014 ions/cm2 on monolayer molybdenum disulfide (MoS2) crystals. The optical signatures of defects, such as the evolution of defect-activated LA-bands and a broadening of the first-order (E' and A'1) modes, can be studied by Raman spectroscopy. High-resolution scanning transmission electron microscopy (HR-STEM) analysis revealed that most defects are vacancies of few-molybdenum atoms with surrounding sulfur atoms (VxMo+yS) at a low ion dose. When increasing the ion dose, the atomic vacancies merge and form nanometer-sized holes. Utilizing HR-STEM and image analysis, we propose the estimation of the finite crystal length (Lfc) via the careful quantification of 0D defects in 2D systems through the formula Lfc = 4.41/ηion, where ηion corresponds to the ion dose. Combining HR-STEM and Raman spectroscopy, the formula to calculate Lfc from Raman features, I(LA)/I(A'1) = 5.09/Lfc2, is obtained. We have also demonstrated an effective route to healing the ion irradiation-induced atomic vacancies by annealing defective MoS2 in a hydrogen disulfide (H2S) atmosphere. The H2S annealing improved the crystal quality of MoS2 with Lfc greater than the calculated size of the A exciton wave function, which leads to a partial recovery of the photoluminescence signal after its quenching by ion irradiation.
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Affiliation(s)
- Kazunori Fujisawa
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Center for 2-Dimensional and Layered Materials, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Research Initiative for Supra Materials, Shinshu University, 4-17-1 Wakasato, Nagano 380-8553, Japan
| | - Bruno R Carvalho
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Center for 2-Dimensional and Layered Materials, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Departamento de Física, Universidade Federal do Rio Grande do Norte, Natal, Rio Grande do Norte 59078-970, Brazil
| | - Tianyi Zhang
- Center for 2-Dimensional and Layered Materials, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Néstor Perea-López
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Center for 2-Dimensional and Layered Materials, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Zhong Lin
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Center for 2-Dimensional and Layered Materials, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Victor Carozo
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Center for 2-Dimensional and Layered Materials, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Department of Physics, Pontifical Catholic University of Rio de Janeiro, Rio de Janeiro, Rio de Janeiro 22451900, Brazil
| | - Sérgio L L M Ramos
- Centro de Tecnologia em Nanomateriais (CT Nano), Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais 30161-970, Brazil
| | - Ethan Kahn
- Center for 2-Dimensional and Layered Materials, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Adam Bolotsky
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Center for 2-Dimensional and Layered Materials, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - He Liu
- Center for 2-Dimensional and Layered Materials, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Ana Laura Elías
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Center for 2-Dimensional and Layered Materials, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Department of Physics, Binghamton University, Binghamton, New York 13902, United States
| | - Mauricio Terrones
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Center for 2-Dimensional and Layered Materials, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Research Initiative for Supra Materials, Shinshu University, 4-17-1 Wakasato, Nagano 380-8553, Japan
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
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14
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Zhao X, Loh KP, Pennycook SJ. Electron beam triggered single-atom dynamics in two-dimensional materials. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 33:063001. [PMID: 33007771 DOI: 10.1088/1361-648x/abbdb9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Controlling atomic structure and dynamics with single-atom precision is the ultimate goal in nanoscience and nanotechnology. Despite great successes being achieved by scanning tunneling microscopy (STM) over the past a few decades, fundamental limitations, such as ultralow temperature, and low throughput, significantly hinder the fabrication of a large array of atomically defined structures by STM. The advent of aberration correction in scanning transmission electron microscopy (STEM) revolutionized the field of nanomaterials characterization pushing the detection limit down to single-atom sensitivity. The sub-angstrom focused electron beam (e-beam) of STEM is capable of interacting with an individual atom, thereby it is the ideal platform to direct and control matter at the level of a single atom or a small cluster. In this article, we discuss the transfer of energy and momentum from the incident e-beam to atoms and their subsequent potential dynamics under different e-beam conditions in 2D materials, particularly transition metal dichalcogenides (TMDs). Next, we systematically discuss the e-beam triggered structural evolutions of atomic defects, line defects, grain boundaries, and stacking faults in a few representative 2D materials. Their formation mechanisms, kinetic paths, and practical applications are comprehensively discussed. We show that desired structural evolution or atom-by-atom assembly can be precisely manipulated by e-beam irradiation which could introduce intriguing functionalities to 2D materials. In particular, we highlight the recent progress on controlling single Si atom migration in real-time on monolayer graphene along an extended path with high throughput in automated STEM. These results unprecedentedly demonstrate that single-atom dynamics can be realized by an atomically focused e-beam. With the burgeoning of artificial intelligence and big data, we can expect that fully automated microscopes with real-time data analysis and feedback could readily design and fabricate large scale nanostructures with unique functionalities in the near future.
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Affiliation(s)
- Xiaoxu Zhao
- Department of Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, 117575, Singapore
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, 117543, Singapore
| | - Kian Ping Loh
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, 117543, Singapore
| | - Stephen J Pennycook
- Department of Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, 117575, Singapore
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15
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Leiter R, Li Y, Kaiser U. In-situ formation and evolution of atomic defects in monolayer WSe 2 under electron irradiation. NANOTECHNOLOGY 2020; 31:495704. [PMID: 32946426 DOI: 10.1088/1361-6528/abb335] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Transition metal dichalcogenide (TMD) monolayers such as MoS2, MoSe2, MoTe2, WS2 and WSe2 have attracted significant interest due to their remarkable electronic and optical properties, exhibiting a direct band gap, enabling usability in electronics and optics. Their properties can be altered further by the introduction of lattice defects. In this work, the dynamics of the formation of electron-beam-induced lattice defects in monolayer WSe2 are investigated by in-situ spherical and chromatic aberration-corrected low-voltage transmission electron microscopy. We show and analyze the electron-dose-limited life of a monolayer WSe2 from the formation of isolated Se vacancies over extended defects such as vacancy lines, mirror twin boundaries (MTBs) and inversion domains towards the loss of W atoms leading to the formation of holes and finally the destruction of the monolayer. We identify, moreover, a new type of MTB. Our study extends the basic understanding of defect dynamics in monolayer WSe2, sheds further light on the electron radiation response and suggests new ways for engineering the in-plane architecture of TMDs.
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Affiliation(s)
- Robert Leiter
- Electron Microscopy Group of Materials Science, Ulm University, Albert-Einstein-Allee 11, 89081, Ulm, Germany
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16
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Ryu GH, Chan RJ. Sequential conversion from line defects to atomic clusters in monolayer WS 2. Appl Microsc 2020; 50:27. [PMID: 33580451 PMCID: PMC7818298 DOI: 10.1186/s42649-020-00047-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2020] [Accepted: 11/12/2020] [Indexed: 11/10/2022] Open
Abstract
Transition metal dichalcogenides (TMD), which is composed of a transition metal atom and chalcogen ion atoms, usually form vacancies based on the knock-on threshold of each atom. In particular, when electron beam is irradiated on a monolayer TMD such as MoS2 and WS2, S vacancies are formed preferentially, and they are aligned linearly to constitute line defects. And then, a hole is formed at the point where the successively formed line defects collide, and metal clusters are also formed at the edge of the hole. This study reports a process in which the line defects formed in a monolayer WS2 sheet expends into holes. Here, the process in which the W cluster, which always occurs at the edge of the formed hole, goes through a uniform intermediate phase is explained based on the line defects and the formation behavior of the hole. Further investigation confirms the atomic structure of the intermediate phase using annular dark field scanning transition electron microscopy (ADF-STEM) and image simulation.
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Affiliation(s)
- Gyeong Hee Ryu
- School of Materials Science and Engineering, Gyeongsang National University, Jinju, 52828, Republic of Korea.
| | - Ren-Jie Chan
- Department of Materials, University of Oxford, 16 Parks Road, Oxford, OX1 3PH, UK
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17
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Park S, Siahrostami S, Park J, Mostaghimi AHB, Kim TR, Vallez L, Gill TM, Park W, Goodson KE, Sinclair R, Zheng X. Effect of Adventitious Carbon on Pit Formation of Monolayer MoS 2. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2020; 32:e2003020. [PMID: 32743836 DOI: 10.1002/adma.202003020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Revised: 06/26/2020] [Indexed: 06/11/2023]
Abstract
Forming pits on molybdenum disulfide (MoS2 ) monolayers is desirable for (opto)electrical, catalytic, and biological applications. Thermal oxidation is a potentially scalable method to generate pits on monolayer MoS2 , and pits are assumed to preferentially form around undercoordinated sites, such as sulfur vacancies. However, studies on thermal oxidation of MoS2 monolayers have not considered the effect of adventitious carbon (C) that is ubiquitous and interacts with oxygen at elevated temperatures. Herein, the effect of adventitious C on the pit formation on MoS2 monolayers during thermal oxidation is studied. The in situ environmental transmission electron microscopy measurements herein show that pit formation is preferentially initiated at the interface between adventitious C nanoparticles and MoS2 , rather than only sulfur vacancies. Density functional theory (DFT) calculations reveal that the C/MoS2 interface favors the sequential adsorption of oxygen atoms with facile kinetics. These results illustrate the important role of adventitious C on pit formation on monolayer MoS2 .
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Affiliation(s)
- Sangwook Park
- Department of Mechanical Engineering, Stanford University, 440 Escondido Mall, Stanford, CA, 94305, USA
| | - Samira Siahrostami
- Department of Chemistry, University of Calgary, 2500 University Drive NW, Calgary, Alberta, T2N 1N4, Canada
| | - Joonsuk Park
- Department of Materials Science and Engineering, Stanford University, 496 Lomita Mall, Stanford, CA, 94305, USA
| | | | - Taeho Roy Kim
- Stanford Nano Shared Facilities, Stanford University, 476 Lomita Mall, Stanford, CA, 94305, USA
| | - Lauren Vallez
- Department of Mechanical Engineering, Stanford University, 440 Escondido Mall, Stanford, CA, 94305, USA
| | - Thomas Mark Gill
- Department of Mechanical Engineering, Stanford University, 440 Escondido Mall, Stanford, CA, 94305, USA
| | - Woosung Park
- Department of Mechanical Systems Engineering, Sookmyung Women's University, Seoul, 04310, South Korea
| | - Kenneth E Goodson
- Department of Mechanical Engineering, Stanford University, 440 Escondido Mall, Stanford, CA, 94305, USA
| | - Robert Sinclair
- Department of Materials Science and Engineering, Stanford University, 496 Lomita Mall, Stanford, CA, 94305, USA
| | - Xiaolin Zheng
- Department of Mechanical Engineering, Stanford University, 440 Escondido Mall, Stanford, CA, 94305, USA
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18
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Wang X, Guan X, Ren X, Liu T, Huang W, Cao J, Jin C. Deriving 2D M 2X 3 (M = Mo, W, X = S, Se) by periodic assembly of chalcogen vacancy lines in their MX 2 counterparts. NANOSCALE 2020; 12:8285-8293. [PMID: 32236196 DOI: 10.1039/c9nr10144f] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Structural defects in crystals are generally believed to disrupt the symmetry of the pristine lattice, but sometimes, they can also serve as the constituent elements of new structures if they are arranged in a well-ordered pattern. Herein, choosing 2D transition metal dichalcogenides (TMDCs) as a model system, we successfully fabricated a novel group of 2D materials-M2X3 (M = Mo, W, X = S, Se) via the periodic assembly of chalcogen vacancy lines in their corresponding MX2 monolayers (such as MoS2). Our ab initio calculations further revealed that these monolayer M2X3 materials electronically exhibit quasi-direct narrow band-gap semiconducting characteristics, e.g., Eg = 0.89 eV for Mo2S3, and show ultra-high phonon-limited room-temperature carrier mobility up to ∼27 000 cm2 V-1 s-1 for electrons in Mo2S3. The emergence of these novel M2X3 materials expands the existing 2D family and provides new platforms for both fundamental research and practical applications, and the approach via the periodic assembly of ordered defects should also be applicable to other 2D materials.
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Affiliation(s)
- Xiaowei Wang
- State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou, Zhejiang 310027, China.
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19
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Murthy AA, Stanev TK, Dos Reis R, Hao S, Wolverton C, Stern NP, Dravid VP. Direct Visualization of Electric-Field-Induced Structural Dynamics in Monolayer Transition Metal Dichalcogenides. ACS NANO 2020; 14:1569-1576. [PMID: 32003564 DOI: 10.1021/acsnano.9b06581] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Layered transition metal dichalcogenides offer many attractive features for next-generation low-dimensional device geometries. Due to the practical and fabrication challenges related to in situ methods, the atomistic dynamics that give rise to realizable macroscopic device properties are often unclear. In this study, in situ transmission electron microscopy techniques are utilized in order to understand the structural dynamics at play, especially at interfaces and defects, in the prototypical film of monolayer MoS2 under electrical bias. Through our sample fabrication process, we clearly identify the presence of mass transport in the presence of a lateral electric field. In particular, we observe that the voids present at grain boundaries combine to induce structural deformation. The electric field mediates a net vacancy flux from the grain boundary interior to the exposed surface edge sites that leaves molybdenum clusters in its wake. Following the initial biasing cycles, however, the mass flow is largely diminished and the resultant structure remains stable over repeated biasing. We believe insights from this work can help explain observations of nonuniform heating and preferential oxidation at grain boundary sites in these materials.
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20
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Sinha S, Zhu T, France-Lanord A, Sheng Y, Grossman JC, Porfyrakis K, Warner JH. Atomic structure and defect dynamics of monolayer lead iodide nanodisks with epitaxial alignment on graphene. Nat Commun 2020; 11:823. [PMID: 32041958 PMCID: PMC7010709 DOI: 10.1038/s41467-020-14481-z] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2019] [Accepted: 01/06/2020] [Indexed: 11/09/2022] Open
Abstract
Lead Iodide (PbI2) is a large bandgap 2D layered material that has potential for semiconductor applications. However, atomic level study of PbI2 monolayer has been limited due to challenges in obtaining thin crystals. Here, we use liquid exfoliation to produce monolayer PbI2 nanodisks (30-40 nm in diameter and > 99% monolayer purity) and deposit them onto suspended graphene supports to enable atomic structure study of PbI2. Strong epitaxial alignment of PbI2 monolayers with the underlying graphene lattice occurs, leading to a phase shift from the 1 T to 1 H structure to increase the level of commensuration in the two lattice spacings. The fundamental point vacancy and nanopore structures in PbI2 monolayers are directly imaged, showing rapid vacancy migration and self-healing. These results provide a detailed insight into the atomic structure of monolayer PbI2, and the impact of the strong van der Waals interaction with graphene, which has importance for future applications in optoelectronics.
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Affiliation(s)
- Sapna Sinha
- Department of Materials, University of Oxford, 16 Parks Road, Oxford, OX1 3PH, UK
| | - Taishan Zhu
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, 02139, USA
| | - Arthur France-Lanord
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, 02139, USA
| | - Yuewen Sheng
- Department of Materials, University of Oxford, 16 Parks Road, Oxford, OX1 3PH, UK
| | - Jeffrey C Grossman
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, 02139, USA
| | - Kyriakos Porfyrakis
- Faculty of Engineering and Science, University of Greenwich, Central Avenue, Chatham Maritime, Kent, ME4 4TB, UK
| | - Jamie H Warner
- Department of Mechanical Engineering, University of Texas at Austin, 204 Dean Keeton Street, Austin, 78712, USA.
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21
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Gerkman MA, Lee JK, Li X, Zhang Q, Windley M, Fonseca MV, Lu Y, Warner JH, Han GGD. Direct Imaging of Individual Molecular Binding to Clean Nanopore Edges in 2D Monolayer MoS 2. ACS NANO 2020; 14:153-165. [PMID: 31747249 DOI: 10.1021/acsnano.9b06061] [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
We use annular dark-field scanning transmission electron microscopy (ADF-STEM) to study how solution-deposited molecules bind to the edges and surface regions around nanopores in MoS2 monolayers. Nanopores with clean atomically flat edges and controllable mean diameter were generated by time-dependent large-area electron beam exposure during an in situ heating process, ready for subsequent molecular attachment. An organic molecule was designed to have a dithiolane end group that binds to Mo-terminated sites and a ligand structure that incorporates a single transition metal atom (Pt) marker for ADF-STEM detection. Pt atoms were used to track molecular binding around zigzag edges of MoS2 and to predict the orientations and conformations of molecules upon binding. We found that the molecules preferred to reside on the surface of the MoS2, pointing inward when attaching to the edge, rather than dangling out from the edge into free space, which is attributed to van der Waals interactions between the aromatic core of the molecule and the MoS2 basal planes. These results help us understand the way solution-deposited single molecules attach to free-standing edges of 2D crystals and the influence of van der Waals forces in guiding molecular binding.
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Affiliation(s)
- Mihael A Gerkman
- Department of Chemistry , Brandeis University , 415 South Street , Waltham , Massachusetts 02453 , United States
| | - Ja Kyung Lee
- Department of Materials , University of Oxford , 16 Parks Road , Oxford , OX1 3PH , United Kingdom
| | - Xiang Li
- Department of Chemistry , Brandeis University , 415 South Street , Waltham , Massachusetts 02453 , United States
| | - Qianyang Zhang
- Department of Materials , University of Oxford , 16 Parks Road , Oxford , OX1 3PH , United Kingdom
| | - Maurice Windley
- Department of Chemistry , Brandeis University , 415 South Street , Waltham , Massachusetts 02453 , United States
| | - Maria V Fonseca
- Department of Chemistry , Brandeis University , 415 South Street , Waltham , Massachusetts 02453 , United States
| | - Yang Lu
- Department of Materials , University of Oxford , 16 Parks Road , Oxford , OX1 3PH , United Kingdom
| | - Jamie H Warner
- Department of Materials , University of Oxford , 16 Parks Road , Oxford , OX1 3PH , United Kingdom
| | - Grace G D Han
- Department of Chemistry , Brandeis University , 415 South Street , Waltham , Massachusetts 02453 , United States
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22
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Tai KL, Huang CW, Cai RF, Huang GM, Tseng YT, Chen J, Wu WW. Atomic-Scale Fabrication of In-Plane Heterojunctions of Few-Layer MoS 2 via In Situ Scanning Transmission Electron Microscopy. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2020; 16:e1905516. [PMID: 31825564 DOI: 10.1002/smll.201905516] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2019] [Revised: 11/14/2019] [Indexed: 06/10/2023]
Abstract
Layered MoS2 is a prospective candidate for use in energy harvesting, valleytronics, and nanoelectronics. Its properties strongly related to its stacking configuration and the number of layers. Due to its atomically thin nature, understanding the atomic-level and structural modifications of 2D transition metal dichalcogenides is still underdeveloped, particularly the spatial control and selective precision. Therefore, the development of nanofabrication techniques is essential. Here, an atomic-scale approach used to sculpt 2D few-layer MoS2 into lateral heterojunctions via in situ scanning/transmission electron microscopy (STEM/TEM) is developed. The dynamic evolution is tracked using ultrafast and high-resolution filming equipment. The assembly behaviors inherent to few-layer 2D-materials are observed during the process and included the following: scrolling, folding, etching, and restructuring. Atomic resolution STEM is employed to identify the layer variation and stacking sequence for this new 2D-architecture. Subsequent energy-dispersive X-ray spectroscopy and electron energy loss spectroscopy analyses are performed to corroborate the elemental distribution. This sculpting technique that is established allows for the formation of sub-10 nm features, produces diverse nanostructures, and preserves the crystallinity of the material. The lateral heterointerfaces created in this study also pave the way for the design of quantum-relevant geometries, flexible optoelectronics, and energy storage devices.
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Affiliation(s)
- Kuo-Lun Tai
- Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu, 300, Taiwan
| | - Chun-Wei Huang
- Material and Chemical Research Laboratories, Nanotechnology Research Center, Industrial Technology Research Institute, Hsinchu, 310, Taiwan
| | - Ren-Fong Cai
- Material and Chemical Research Laboratories, Nanotechnology Research Center, Industrial Technology Research Institute, Hsinchu, 310, Taiwan
| | - Guan-Min Huang
- Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu, 300, Taiwan
| | - Yi-Tang Tseng
- Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu, 300, Taiwan
| | - Jun Chen
- Department of Materials, University of Oxford, OX1 2JD, Oxford, UK
| | - Wen-Wei Wu
- Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu, 300, Taiwan
- Frontier Research Center on Fundamental and Applied Sciences of Matters, National Tsing Hua University, Hsinchu City, 300, Taiwan
- Center for the Intelligent Semiconductor Nano-system Technology Research, National Chiao Tung University, Hsinchu, 300, Taiwan
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23
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Chen J, Ryu GH, Zhang Q, Wen Y, Tai KL, Lu Y, Warner JH. Spatially Controlled Fabrication and Mechanisms of Atomically Thin Nanowell Patterns in Bilayer WS 2 Using in Situ High Temperature Electron Microscopy. ACS NANO 2019; 13:14486-14499. [PMID: 31794193 DOI: 10.1021/acsnano.9b08220] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
We show controlled production of atomically thin nanowells in bilayer WS2 using an in situ heating holder combined with a focused electron beam in a scanning transmission electron microscope (STEM). We systematically study the formation and evolvement mechanism involved in removing a single layer of WS2 within a bilayer region with 2 nm accuracy in location and without punching through to the other layer to create a hole. Best results are found when using a high temperature of 800 °C, because it enables thermally activated atomic migration and eliminates the interference from surface carbon contamination. We demonstrate precise control over spatial distributions with 5 nm accuracy of patterning and the width of nanowells adjustable by dose-dependent parameters. The mechanism of removing a monolayer of WS2 within a bilayer region is different than removing equivalent sections in a monolayer film due to the van der Waals interaction of the underlying remaining layer in the bilayer system that stabilizes the excess W atom stoichiometry within the edges of the nanowell structure and facilitates expansion. This study offers insights for the nanoengineering of nanowells in two-dimensional (2D) transitional metal dichalcogenides (TMDs), which could hold potential as selective traps to localize 2D reactions in molecules and ions, underpinning the broader utilization of 2D material membranes.
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Affiliation(s)
- Jun Chen
- Department of Materials , University of Oxford , Parks Road , Oxford OX1 3PH , United Kingdom
| | - Gyeong Hee Ryu
- Department of Materials , University of Oxford , Parks Road , Oxford OX1 3PH , United Kingdom
| | - Qianyang Zhang
- Department of Materials , University of Oxford , Parks Road , Oxford OX1 3PH , United Kingdom
| | - Yi Wen
- Department of Materials , University of Oxford , Parks Road , Oxford OX1 3PH , United Kingdom
| | - Kuo-Lun Tai
- Department of Materials , University of Oxford , Parks Road , Oxford OX1 3PH , United Kingdom
| | - Yang Lu
- Department of Materials , University of Oxford , Parks Road , Oxford OX1 3PH , United Kingdom
| | - Jamie H Warner
- Department of Materials , University of Oxford , Parks Road , Oxford OX1 3PH , United Kingdom
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24
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Shautsova V, Sinha S, Hou L, Zhang Q, Tweedie M, Lu Y, Sheng Y, Porter BF, Bhaskaran H, Warner JH. Direct Laser Patterning and Phase Transformation of 2D PdSe 2 Films for On-Demand Device Fabrication. ACS NANO 2019; 13:14162-14171. [PMID: 31833365 DOI: 10.1021/acsnano.9b06892] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Heterophase homojunction formation in atomically thin 2D layers is of great importance for next-generation nanoelectronics and optoelectronics applications. Technologically challenging, controllable transformation between the semiconducting and metallic phases of transition metal chalcogenides is of particular importance. Here, we demonstrate that controlled laser irradiation can be used to directly ablate PdSe2 thin films using high power or trigger the local transformation of PdSe2 into a metallic phase PdSe2-x using lower laser power. Such transformations are possible due to the low decomposition temperature of PdSe2 and a variety of stable phases compared to other 2D transition metal dichalcogenides. Scanning transmission electron microscopy is used to reveal the laser-induced Se-deficient phases of PdSe2 material. The process sensitivity to the laser power allows patterning flexibility for resist-free device fabrication. The laser-patterned devices demonstrate that a laser-induced metallic phase PdSe2-x is stable with increased conductivity by a factor of about 20 compared to PdSe2. These findings contribute to the development of nanoscale devices with homojunctions and scalable methods to achieve structural transformations in 2D materials.
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Affiliation(s)
- Viktoryia Shautsova
- Department of Materials , University of Oxford , Parks Road , Oxford OX1 3PH , United Kingdom
| | - Sapna Sinha
- Department of Materials , University of Oxford , Parks Road , Oxford OX1 3PH , United Kingdom
| | - Linlin Hou
- Department of Materials , University of Oxford , Parks Road , Oxford OX1 3PH , United Kingdom
| | - Qianyang Zhang
- Department of Materials , University of Oxford , Parks Road , Oxford OX1 3PH , United Kingdom
| | - Martin Tweedie
- Department of Materials , University of Oxford , Parks Road , Oxford OX1 3PH , United Kingdom
| | - Yang Lu
- Department of Materials , University of Oxford , Parks Road , Oxford OX1 3PH , United Kingdom
| | - Yuewen Sheng
- Department of Materials , University of Oxford , Parks Road , Oxford OX1 3PH , United Kingdom
| | - Benjamin F Porter
- Department of Materials , University of Oxford , Parks Road , Oxford OX1 3PH , United Kingdom
| | - Harish Bhaskaran
- Department of Materials , University of Oxford , Parks Road , Oxford OX1 3PH , United Kingdom
| | - Jamie H Warner
- Department of Materials , University of Oxford , Parks Road , Oxford OX1 3PH , United Kingdom
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25
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Ryu GH, Zhu T, Chen J, Sinha S, Shautsova V, Grossman JC, Warner JH. Striated 2D Lattice with Sub-nm 1D Etch Channels by Controlled Thermally Induced Phase Transformations of PdSe 2. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2019; 31:e1904251. [PMID: 31559669 DOI: 10.1002/adma.201904251] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Revised: 08/21/2019] [Indexed: 05/12/2023]
Abstract
2D crystals are typically uniform and periodic in-plane with stacked sheet-like structure in the out-of-plane direction. Breaking the in-plane 2D symmetry by creating unique lattice structures offers anisotropic electronic and optical responses that have potential in nanoelectronics. However, creating nanoscale-modulated anisotropic 2D lattices is challenging and is mostly done using top-down lithographic methods with ≈10 nm resolution. A phase transformation mechanism for creating 2D striated lattice systems is revealed, where controlled thermal annealing induces Se loss in few-layered PdSe2 and leads to 1D sub-nm etched channels in Pd2 Se3 bilayers. These striated 2D crystals cannot be described by a typical unit cells of 1-2 Å for crystals, but rather long range nanoscale periodicity in each three directions. The 1D channels give rise to localized conduction states, which have no bulk layered counterpart or monolayer form. These results show how the known family of 2D crystals can be extended beyond those that exist as bulk layered van der Waals crystals by exploiting phase transformations by elemental depletion in binary systems.
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Affiliation(s)
- Gyeong Hee Ryu
- Department of Materials, University of Oxford, 16 Parks Road, Oxford, OX1 3PH, UK
| | - Taishan Zhu
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, 02139, USA
| | - Jun Chen
- Department of Materials, University of Oxford, 16 Parks Road, Oxford, OX1 3PH, UK
| | - Sapna Sinha
- Department of Materials, University of Oxford, 16 Parks Road, Oxford, OX1 3PH, UK
| | - Viktoryia Shautsova
- Department of Materials, University of Oxford, 16 Parks Road, Oxford, OX1 3PH, UK
| | - Jeffrey C Grossman
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, 02139, USA
| | - Jamie H Warner
- Department of Materials, University of Oxford, 16 Parks Road, Oxford, OX1 3PH, UK
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26
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Li X, Zhang S, Huang H, Hu L, Liu F, Wang Q. Unidirectional Spin-Orbit Interaction Induced by the Line Defect in Monolayer Transition Metal Dichalcogenides for High-Performance Devices. NANO LETTERS 2019; 19:6005-6012. [PMID: 31386373 DOI: 10.1021/acs.nanolett.9b01812] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Spin-orbit (SO) interaction is an indispensable element in the field of spintronics for effectively manipulating the spin of carriers. However, in crystalline solids, the momentum-dependent SO effective magnetic field generally results in spin randomization by a process known as the Dyakonov-Perel spin relaxation, leading to the loss of spin information. To overcome this obstacle, the persistent spin helix (PSH) state with a unidirectional SO field was proposed but difficult to achieve in real materials. Here, on the basis of first-principles calculations and tight-binding model analysis, we report for the first time a unidirectional SO field in monolayer transition metal dichalcogenides (TMDs, MX2, M = Mo, W; and X = S, Se) induced by two parallel chalcogen vacancy lines. By changing the relative positions of the two vacancy lines, the direction of the SO field can be tuned from x to y. Moreover, using k·p perturbation theory and group theory analysis, we demonstrate that the emerging unidirectional SO field is subject to both the structural symmetry and 1D nature of such defects engineered in 2D TMDs. In particular, through transport calculations, we confirm that the predicted SO states carry highly coherent spin current. Our findings shed new light on creating PSH states for high-performance spintronic devices.
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Affiliation(s)
- Xiaoyin Li
- Center for Applied Physics and Technology, Department of Materials Science and Engineering, HEDPS, College of Engineering , Peking University , Beijing 100871 , China
- Department of Materials Science and Engineering , University of Utah , Salt Lake City , Utah 84112 , United States
| | - Shunhong Zhang
- International Center for Quantum Design of Functional Materials (ICQD), Hefei National Laboratory for Physical Sciences at Microscale , University of Science and Technology of China , Hefei , Anhui 230026 , China
- Department of Materials Science and Engineering , University of Utah , Salt Lake City , Utah 84112 , United States
| | - Huaqing Huang
- Department of Materials Science and Engineering , University of Utah , Salt Lake City , Utah 84112 , United States
| | - Lin Hu
- Department of Materials Science and Engineering , University of Utah , Salt Lake City , Utah 84112 , United States
- Beijing Computational Science Research Center , Beijing 100193 , China
| | - Feng Liu
- Department of Materials Science and Engineering , University of Utah , Salt Lake City , Utah 84112 , United States
| | - Qian Wang
- Center for Applied Physics and Technology, Department of Materials Science and Engineering, HEDPS, College of Engineering , Peking University , Beijing 100871 , China
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27
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Ryu GH, Chen J, Wen Y, Zhou S, Chang RJ, Warner JH. Atomic structural catalogue of defects and vertical stacking in 2H/3R mixed polytype multilayer WS 2 pyramids. NANOSCALE 2019; 11:10859-10871. [PMID: 31135012 DOI: 10.1039/c9nr01783f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
We examine the atomic structure of chemical vapour deposition grown multilayer WS2 pyramids using aberration corrected annular dark field scanning transmission electron microscopy coupled with an in situ heating holder. The stacking orders and specific types of defects after partial degradation by S and W atomic loss at high temperature are resolved layer-by-layer. Our study of an individual WS2 pyramid with at least six layers, reveals a mixed 2H and 3R polytype stacking. Etching occurred both top and bottom of the WS2 pyramid, which aids in determining the exact vertical layer stacking configurations in the thicker regions. We provide an extensive catalogue of the contrast profiles associated with defects in WS2 as a function of layer number and stacking type, as imaged using ADF-STEM. These results provide extensive details about the identification of a wide range of defects in S2 layers, and the unique ADF-STEM contrast patterns that arise from complex multilayer stacking.
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Affiliation(s)
- Gyeong Hee Ryu
- Department of Materials, University of Oxford, 16 Parks Road, Oxford OX1 3PH, UK.
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28
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Fang S, Wen Y, Allen CS, Ophus C, Han GGD, Kirkland AI, Kaxiras E, Warner JH. Atomic electrostatic maps of 1D channels in 2D semiconductors using 4D scanning transmission electron microscopy. Nat Commun 2019; 10:1127. [PMID: 30850616 PMCID: PMC6408534 DOI: 10.1038/s41467-019-08904-9] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2018] [Accepted: 02/01/2019] [Indexed: 11/16/2022] Open
Abstract
Defects in materials give rise to fluctuations in electrostatic fields that reflect the local charge density, but imaging this with single atom sensitivity is challenging. However, if possible, this provides information about the energetics of adatom binding, localized conduction channels, molecular functionality and their relationship to individual bonds. Here, ultrastable electron-optics are combined with a high-speed 2D electron detector to map electrostatic fields around individual atoms in 2D monolayers using 4D scanning transmission electron microscopy. Simultaneous imaging of the electric field, phase, annular dark field and the total charge in 2D MoS2 and WS2 is demonstrated for pristine areas and regions with 1D wires. The in-gap states in sulphur line vacancies cause 1D electron-rich channels that are mapped experimentally and confirmed using density functional theory calculations. We show how electrostatic fields are sensitive in defective areas to changes of atomic bonding and structural determination beyond conventional imaging. Imaging electrostatic field around individual atoms or defective areas in monolayer 2D materials is crucial to understand their structural coordination. Here, the authors report local changes in specific atomic bonds and provide in-depth structural information of complex defective monolayer MoS2 and WS2 systems by 4D STEM.
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Affiliation(s)
- Shiang Fang
- Department of Physics, Harvard University, Cambridge, MA, 02138, USA
| | - Yi Wen
- Department of Materials, University of Oxford, 16 Parks Road, Oxford, OX1 3PH, UK
| | - Christopher S Allen
- Department of Materials, University of Oxford, 16 Parks Road, Oxford, OX1 3PH, UK.,Electron Physical Sciences Imaging Center, Diamond Light Source Ltd., Didcot, Oxfordshire, OX11 0DE, UK
| | - Colin Ophus
- National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, 94720, CA, USA
| | - Grace G D Han
- Department of Chemistry, Brandeis University, Waltham, 02453, MA, USA
| | - Angus I Kirkland
- Department of Materials, University of Oxford, 16 Parks Road, Oxford, OX1 3PH, UK.,Electron Physical Sciences Imaging Center, Diamond Light Source Ltd., Didcot, Oxfordshire, OX11 0DE, UK
| | - Efthimios Kaxiras
- Department of Physics, Harvard University, Cambridge, MA, 02138, USA. .,John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, 02138, USA.
| | - Jamie H Warner
- Department of Materials, University of Oxford, 16 Parks Road, Oxford, OX1 3PH, UK.
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29
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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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30
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Chen J, Zhou S, Wen Y, Ryu GH, Allen C, Lu Y, Kirkland AI, Warner JH. In situ high temperature atomic level dynamics of large inversion domain formations in monolayer MoS 2. NANOSCALE 2019; 11:1901-1913. [PMID: 30644498 DOI: 10.1039/c8nr08821g] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Here we study the high-temperature formation and dynamics of large inversion domains (IDs) that form in monolayer MoS2 using atomic-resolution annular dark-field scanning transmission electron microscopy (ADF-STEM) with an in situ heating stage. We use temperatures above 700 °C to thermally activate rapid S vacancy migration and this leads to a formation mechanism of IDs that differs from the one at room temperature, where S vacancy migration is limited. We show that at high temperatures the formation of IDs occurs from intersected networks of long S vacancy line defects, whose strain fields are non-orthogonal and trigger large scale atomic reconstructions. Once formed, the IDs are influenced by the dynamic behaviour of nearby line defects and voids. With Mo and S atoms undergoing movement, the two types of ID grain boundaries can shift to allow further expansion of the ID area along the adjoining line defects. We reveal that IDs serve as metastable configurations between line defect rearrangements and eventual void formation under electron beam irradiation during heating. The formation of voids near to the IDs causes them to revert back to pristine lattice, which has the effect of restricting the ID domain size to a certain range (e.g. 3-5 nm in our observation) instead of continuously enlarging. This study provides insights into how the MoS2 IDs form and evolve at high temperature and can benefit the tailoring of electronic properties of two dimensional materials by structural manipulation.
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Affiliation(s)
- Jun Chen
- Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, UK.
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31
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Ryu GH, France-Lanord A, Wen Y, Zhou S, Grossman JC, Warner JH. Atomic Structure and Dynamics of Self-Limiting Sub-Nanometer Pores in Monolayer WS 2. ACS NANO 2018; 12:11638-11647. [PMID: 30375855 DOI: 10.1021/acsnano.8b07051] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
We reveal a self-limiting mechanism during the formation of a specific type of circular nanopore in monolayer WS2 that limits its diameter to sub-nm. A single W atom vacancy (triangular nanopore) is transformed into the self-limiting nanopore (SLNP) through the atomic restructuring of S atoms around the area, reducing the number of dangling bonds at the nanopore edge by shifting them further in-plane with W-W bonding instead. Bond rotations in WS2 help accommodate the electron beam induced atomic loss and ensure the stability of the SLNP. The SLNP shows significant improvement in diameter stability during electron beam irradiation compared to other triangular nanopores in WS2 that typically continue to expand in diameter during atom loss. The atomic structure of these SLNPs is studied using aberration-corrected scanning transmission electron microscopy with an in situ heating holder, revealing that the SLNPs are mostly formed at a temperature of ∼500 °C, which is a balance between thermally activated S vacancy diffusion and sufficient S vacancy density to initiate local atomic reconstruction. At higher temperatures ( i. e., 1000 °C), S vacancies quickly migrate away into long line vacancies, resulting in low S vacancy density and rapidly expanding holes generated at the edges of the line vacancies. At room temperature, S vacancy migration is low and vacancy density is very high, which limits atomic reconstruction, and instead many small holes open up. These results provide insights into the factors that lead to uniform sized nanopores in the sub-nm range in transition-metal dichalcogenides.
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Affiliation(s)
- Gyeong Hee Ryu
- Department of Materials , University of Oxford , 16 Parks Road , Oxford OX1 3PH , United Kingdom
| | - Arthur France-Lanord
- Department of Materials Science and Engineering , Massachusetts Institute of Technology , 77 Massachusetts Avenue , Cambridge , Massachusetts 02139 , United States
| | - Yi Wen
- Department of Materials , University of Oxford , 16 Parks Road , Oxford OX1 3PH , United Kingdom
| | - Si Zhou
- Department of Materials , University of Oxford , 16 Parks Road , Oxford OX1 3PH , United Kingdom
| | - Jeffrey C Grossman
- Department of Materials Science and Engineering , Massachusetts Institute of Technology , 77 Massachusetts Avenue , Cambridge , Massachusetts 02139 , United States
| | - Jamie H Warner
- Department of Materials , University of Oxford , 16 Parks Road , Oxford OX1 3PH , United Kingdom
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