1
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Coelho PM. Magnetic doping in transition metal dichalcogenides. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2024; 36:203001. [PMID: 38324890 DOI: 10.1088/1361-648x/ad271b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2023] [Accepted: 02/07/2024] [Indexed: 02/09/2024]
Abstract
Transition metal dichalcogenides (TMDCs) are materials with unique electronic properties due to their two-dimensional nature. Recently, there is a large and growing interest in synthesizing ferromagnetic TMDCs for applications in electronic devices and spintronics. Apart from intrinsically magnetic examples, modification via either intrinsic defects or external dopants may induce ferromagnetism in non-magnetic TMDCs and, hence expand the application of these materials. Here, we review recent experimental work on intrinsically non-magnetic TMDCs that present ferromagnetism as a consequence of either intrinsic defects or doping via self-flux approach, ion implantation or e-beam evaporation. The experimental work discussed here is organized by modification/doping mechanism. We also review current work on density functional theory calculations that predict ferromagnetism in doped systems, which also serve as preliminary data for the choice of new doped TMDCs to be explored experimentally. Implementing a controlled process to induce magnetism in two-dimensional materials is key for technological development and this topical review discusses the fundamental procedures while presenting promising materials to be investigated in order to achieve this goal.
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Affiliation(s)
- Paula Mariel Coelho
- Department of Physics, University of North Florida, Jacksonville, FL, United States of America
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2
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Köster J, Kretschmer S, Storm A, Rasper F, Kinyanjui MK, Krasheninnikov AV, Kaiser U. Phase transformations in single-layer MoTe 2stimulated by electron irradiation and annealing. NANOTECHNOLOGY 2024; 35:145301. [PMID: 38096582 DOI: 10.1088/1361-6528/ad15bb] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2023] [Accepted: 12/14/2023] [Indexed: 01/16/2024]
Abstract
Among two-dimensional (2D) transition metal dichalcogenides (TMDs), MoTe2is predestined for phase-engineering applications due to the small difference in free energy between the semiconducting H-phase and metallic 1T'-phase. At the same time, the complete picture of the phase evolution originating from point defects in single-layer of semiconducting H-MoTe2via Mo6Te6nanowires to cubic molybdenum has not yet been reported so far, and it is the topic of the present study. The occurring phase transformations in single-layer H-MoTe2were initiated by 40-80 kV electrons in the spherical and chromatic aberration-corrected high-resolution transmission electron microscope and/or when subjected to high temperatures. We analyse the damage cross-section at voltages between 40 kV and 80 kV and relate the results to previously published values for other TMDs. Then we demonstrate that electron beam irradiation offers a route to locally transform freestanding single-layer H-MoTe2into one-dimensional (1D) Mo6Te6nanowires. Combining the experimental data with the results of first-principles calculations, we explain the transformations in MoTe2single-layers and Mo6Te6nanowires by an interplay of electron-beam-induced energy transfer, atom ejection, and oxygen absorption. Further, the effects emerging from electron irradiation are compared with those produced byin situannealing in a vacuum until pure molybdenum crystals are obtained at temperatures of about 1000 °C. A detailed understanding of high-temperature solid-to-solid phase transformation in the 2D limit can provide insights into the applicability of this material for future device fabrication.
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Affiliation(s)
- Janis Köster
- Electron Microscopy Group of Materials Science, Ulm University, Albert-Einstein-Allee 11, D-89081 Ulm, Germany
| | - Silvan Kretschmer
- Institut of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, D-01328 Dresden, Germany
| | - Alexander Storm
- Electron Microscopy Group of Materials Science, Ulm University, Albert-Einstein-Allee 11, D-89081 Ulm, Germany
| | - Fabian Rasper
- Electron Microscopy Group of Materials Science, Ulm University, Albert-Einstein-Allee 11, D-89081 Ulm, Germany
| | - Michael K Kinyanjui
- Electron Microscopy Group of Materials Science, Ulm University, Albert-Einstein-Allee 11, D-89081 Ulm, Germany
| | - Arkady V Krasheninnikov
- Institut of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, D-01328 Dresden, Germany
- Department of Applied Physics, Aalto University, PO Box 14100, FI-00076 Aalto, Finland
| | - Ute Kaiser
- Electron Microscopy Group of Materials Science, Ulm University, Albert-Einstein-Allee 11, D-89081 Ulm, Germany
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3
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Zhu J, Hu Z, Guo S, Luo R, Yu M, Li A, Pang J, Xue M, Pennycook SJ, Liu Z, Zhang Z, Zhou W. Non-epitaxial growth of highly oriented transition metal dichalcogenides with density-controlled twin boundaries. Innovation (N Y) 2023; 4:100502. [PMID: 37701921 PMCID: PMC10493259 DOI: 10.1016/j.xinn.2023.100502] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2023] [Accepted: 08/21/2023] [Indexed: 09/14/2023] Open
Abstract
Twin boundaries (TBs) in transition metal dichalcogenides (TMDs) constitute distinctive one-dimensional electronic systems, exhibiting intriguing physical and chemical properties that have garnered significant attention in the fields of quantum physics and electrocatalysis. However, the controlled manipulation of TBs in terms of density and specific atomic configurations remains a formidable challenge. In this study, we present a non-epitaxial growth approach that enables the controlled and large-scale fabrication of homogeneous catalytically active TBs in monolayer TMDs on arbitrary substrates. Notably, the density achieved using this strategy is six times higher than that observed in convention chemical vapor deposition (CVD)-grown samples. Through rigorous experimental analysis and multigrain Wulff construction simulations, we elucidate the role of regulating the metal source diffusion process, which serves as the key factor for inducing the self-oriented growth of TMD grains and the formation of unified TBs. Furthermore, we demonstrate that this novel growth mode can be readily incorporated into the conventional CVD growth method by making a simple modification of the growth temperature profile, thereby offering a universal approach for engineering of grain boundaries in two-dimensional materials.
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Affiliation(s)
- Juntong Zhu
- School of Physical Sciences, CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Zhili Hu
- State Key Laboratory of Mechanics and Control for Aerospace Structures, Key Laboratory for Intelligent Nano Materials and Devices of Ministry of Education, and Institute for Frontier Science, Nanjing University of Aeronautics and Astronautics, Nanjing 210013, China
| | - Shasha Guo
- School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore
| | - Ruichun Luo
- School of Physical Sciences, CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Maolin Yu
- State Key Laboratory of Mechanics and Control for Aerospace Structures, Key Laboratory for Intelligent Nano Materials and Devices of Ministry of Education, and Institute for Frontier Science, Nanjing University of Aeronautics and Astronautics, Nanjing 210013, China
| | - Ang Li
- School of Physical Sciences, CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jingbo Pang
- School of Physical Sciences, CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Minmin Xue
- State Key Laboratory of Mechanics and Control for Aerospace Structures, Key Laboratory for Intelligent Nano Materials and Devices of Ministry of Education, and Institute for Frontier Science, Nanjing University of Aeronautics and Astronautics, Nanjing 210013, China
| | - Stephen J. Pennycook
- School of Physical Sciences, CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Zheng Liu
- School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore
- Environmental Chemistry and Materials Centre, Nanyang Environment and Water Research Institute, Nanyang Technological University, Singapore 637141, Singapore
| | - Zhuhua Zhang
- State Key Laboratory of Mechanics and Control for Aerospace Structures, Key Laboratory for Intelligent Nano Materials and Devices of Ministry of Education, and Institute for Frontier Science, Nanjing University of Aeronautics and Astronautics, Nanjing 210013, China
| | - Wu Zhou
- School of Physical Sciences, CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing 100049, China
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4
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Kim HW. Recent progress in the role of grain boundaries in two-dimensional transition metal dichalcogenides studied using scanning tunneling microscopy/spectroscopy. Appl Microsc 2023; 53:5. [PMID: 37458942 DOI: 10.1186/s42649-023-00088-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2023] [Accepted: 06/20/2023] [Indexed: 07/20/2023] Open
Abstract
Grain boundaries (GBs) are one- or two-dimensional (2D) defects, which are universal in crystals and play a crucial role in determining their mechanical, electrical, optical, and thermoelectric properties. In general, GBs tend to decrease electrical or thermal conductivity, and consequently degrade the performance of devices. However, the unusual characteristics of GBs have led to the production of a new class of memristors with 2D semiconducting transition metal dichalcogenides (TMDs) and the creation of conducting channels in 2D topological insulators. Therefore, understanding the nature of GBs and their influence on device applications emphasizes the importance of GB engineering for future 2D TMD-based devices. This review discusses recent progress made in the investigation of various roles of GBs in 2D TMDs characterized via scanning tunneling microscopy/spectroscopy.
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Affiliation(s)
- Hyo Won Kim
- Samsung Advanced Institute of Technology, Suwon, 13595, Korea.
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5
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Di Bernardo I, Ripoll-Sau J, Silva-Guillén JA, Calleja F, Ayani CG, Miranda R, Canadell E, Garnica M, Vázquez de Parga AL. Metastable Polymorphic Phases in Monolayer TaTe 2. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2023:e2300262. [PMID: 37029707 DOI: 10.1002/smll.202300262] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2023] [Revised: 03/09/2023] [Indexed: 06/19/2023]
Abstract
Polymorphic phases and collective phenomena-such as charge density waves (CDWs)-in transition metal dichalcogenides (TMDs) dictate the physical and electronic properties of the material. Most TMDs naturally occur in a single given phase, but the fine-tuning of growth conditions via methods such as molecular beam epitaxy (MBE) allows to unlock otherwise inaccessible polymorphic structures. Exploring and understanding the morphological and electronic properties of new phases of TMDs is an essential step to enable their exploitation in technological applications. Here, scanning tunneling microscopy (STM) is used to map MBE-grown monolayer (ML) TaTe2 . This work reports the first observation of the 1H polymorphic phase, coexisting with the 1T, and demonstrates that their relative coverage can be controlled by adjusting synthesis parameters. Several superperiodic structures, compatible with CDWs, are observed to coexist on the 1T phase. Finally, this work provides theoretical insight on the delicate balance between Te…Te and Ta-Ta interactions that dictates the stability of the different phases. The findings demonstrate that TaTe2 is an ideal platform to investigate competing interactions, and indicate that accurate tuning of growth conditions is key to accessing metastable states in TMDs.
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Affiliation(s)
- Iolanda Di Bernardo
- Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, Madrid, 28049, Spain
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies, Monash University, Victoria, 3800, Australia
- School of Physics and Astronomy, Monash University, Victoria, 3800, Australia
- Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanociencia), Madrid, 28049, Spain
| | - Joan Ripoll-Sau
- Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, Madrid, 28049, Spain
- Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanociencia), Madrid, 28049, Spain
| | - Jose Angel Silva-Guillén
- Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanociencia), Madrid, 28049, Spain
| | - Fabian Calleja
- Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanociencia), Madrid, 28049, Spain
| | - Cosme G Ayani
- Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, Madrid, 28049, Spain
- Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanociencia), Madrid, 28049, Spain
| | - Rodolfo Miranda
- Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, Madrid, 28049, Spain
- Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanociencia), Madrid, 28049, Spain
- Instituto Nicolás Cabrera, Universidad Autónoma de Madrid, Madrid, 28049, Spain
- Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, Madrid, 28049, Spain
| | - Enric Canadell
- Institut de Ciència de Materials de Barcelona, ICMAB-CSIC, Campus UAB, Bellaterra, 08193, Spain
| | - Manuela Garnica
- Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanociencia), Madrid, 28049, Spain
- Instituto Nicolás Cabrera, Universidad Autónoma de Madrid, Madrid, 28049, Spain
| | - Amadeo L Vázquez de Parga
- Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, Madrid, 28049, Spain
- Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanociencia), Madrid, 28049, Spain
- Instituto Nicolás Cabrera, Universidad Autónoma de Madrid, Madrid, 28049, Spain
- Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, Madrid, 28049, Spain
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6
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Yamagata K, Maeda M, Tessari Z, Mali KS, Tobe Y, De Feyter S, Tahara K. Solvent Mediated Nanoscale Quasi-Periodic Chirality Reversal in Self-Assembled Molecular Networks Featuring Mirror Twin Boundaries. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2023; 19:e2207209. [PMID: 36683210 DOI: 10.1002/smll.202207209] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2022] [Revised: 12/30/2022] [Indexed: 06/17/2023]
Abstract
Grain boundaries in polycrystals have a prominent impact on the properties of a material, therefore stimulating the research on grain boundary engineering. Structure determination of grain boundaries of molecule-based polycrystals with submolecular resolution remains elusive. Reducing the complexity to monolayers has the potential to simplify grain boundary engineering and may offer real-space imaging with submolecular resolution using scanning tunneling microscopy (STM). Herein, the authors report the observation of quasi-periodic nanoscale chirality switching in self-assembled molecular networks, in combination with twinning, as revealed by STM at the liquid/solid interface. The width of the chiral domain structure peaks at 12-19 nm. Adjacent domains having opposite chirality are connected continuously through interdigitated alkoxy chains forming a 1D defect-free domain border, reflecting a mirror twin boundary. Solvent co-adsorption and the inherent conformational adaptability of the alkoxy chains turn out to be crucial factors in shaping grain boundaries. Moreover, the epitaxial interaction with the substrate plays a role in the nanoscale chirality reversal as well.
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Affiliation(s)
- Kyohei Yamagata
- Department of Applied Chemistry, School of Science and Technology, Meiji University, 1-1-1 Higashimita, Tama-ku, Kawasaki, 214-8571, Japan
| | - Matsuhiro Maeda
- Department of Applied Chemistry, School of Science and Technology, Meiji University, 1-1-1 Higashimita, Tama-ku, Kawasaki, 214-8571, Japan
| | - Zeno Tessari
- Division of Molecular Imaging and Photonics, Department of Chemistry, KU Leuven, Celestijnenlaan 200 F, 3001, Leuven, Belgium
| | - Kunal S Mali
- Division of Molecular Imaging and Photonics, Department of Chemistry, KU Leuven, Celestijnenlaan 200 F, 3001, Leuven, Belgium
| | - Yoshito Tobe
- Department of Applied Chemistry, National Yang Ming Chiao Tung University, 1001 Ta Hsueh Road, Hsinchu, 30030, Taiwan
- Nanoscience and Nanotechnology Center, The Institute of Scientific and Industrial Research (SANKEN), Osaka University, Osaka, 567-0047, Japan
| | - Steven De Feyter
- Division of Molecular Imaging and Photonics, Department of Chemistry, KU Leuven, Celestijnenlaan 200 F, 3001, Leuven, Belgium
| | - Kazukuni Tahara
- Department of Applied Chemistry, School of Science and Technology, Meiji University, 1-1-1 Higashimita, Tama-ku, Kawasaki, 214-8571, Japan
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7
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Lunardon M, Kosmala T, Ghorbani-Asl M, Krasheninnikov AV, Kolekar S, Durante C, Batzill M, Agnoli S, Granozzi G. Catalytic Activity of Defect-Engineered Transition Me tal Dichalcogenides Mapped with Atomic-Scale Precision by Electrochemical Scanning Tunneling Microscopy. ACS ENERGY LETTERS 2023; 8:972-980. [PMID: 36816778 PMCID: PMC9926491 DOI: 10.1021/acsenergylett.2c02599] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/16/2022] [Accepted: 01/03/2023] [Indexed: 06/18/2023]
Abstract
Unraveling structure-activity relationships is a key objective of catalysis. Unfortunately, the intrinsic complexity and structural heterogeneity of materials stand in the way of this goal, mainly because the activity measurements are area-averaged and therefore contain information coming from different surface sites. This limitation can be surpassed by the analysis of the noise in the current of electrochemical scanning tunneling microscopy (EC-STM). Herein, we apply this strategy to investigate the catalytic activity toward the hydrogen evolution reaction of monolayer films of MoSe2. Thanks to atomically resolved potentiodynamic experiments, we can evaluate individually the catalytic activity of the MoSe2 basal plane, selenium vacancies, and different point defects produced by the intersections of metallic twin boundaries. The activity trend deduced by EC-STM is independently confirmed by density functional theory calculations, which also indicate that, on the metallic twin boundary crossings, the hydrogen adsorption energy is almost thermoneutral. The micro- and macroscopic measurements are combined to extract the turnover frequency of different sites, obtaining for the most active ones a value of 30 s-1 at -136 mV vs RHE.
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Affiliation(s)
- Marco Lunardon
- Department
of Chemical Sciences, University of Padova, Padova 35131, Italy
| | - Tomasz Kosmala
- Department
of Chemical Sciences, University of Padova, Padova 35131, Italy
- Institute
of Experimental Physics, University of Wrocław, Wrocław 50-204, Poland
| | - Mahdi Ghorbani-Asl
- Institute
of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf Dresden 01328, Germany
| | - Arkady V. Krasheninnikov
- Institute
of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf Dresden 01328, Germany
- Department
of Applied Physics, Aalto University, 00076 Aalto, Finland
| | - Sadhu Kolekar
- Department
of Physics, University of South Florida, Tampa, Florida 33620, United States
| | - Christian Durante
- Department
of Chemical Sciences, University of Padova, Padova 35131, Italy
| | - Matthias Batzill
- Department
of Physics, University of South Florida, Tampa, Florida 33620, United States
| | - Stefano Agnoli
- Department
of Chemical Sciences, University of Padova, Padova 35131, Italy
- INSTM
Research
Unit, University of Padova, Padova 35131, Italy
| | - Gaetano Granozzi
- Department
of Chemical Sciences, University of Padova, Padova 35131, Italy
- INSTM
Research
Unit, University of Padova, Padova 35131, Italy
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8
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Lasek K, Li J, Ghorbani-Asl M, Khatun S, Alanwoko O, Pathirage V, Krasheninnikov AV, Batzill M. Formation of In-Plane Semiconductor-Metal Contacts in 2D Platinum Telluride by Converting PtTe 2 to Pt 2Te 2. NANO LETTERS 2022; 22:9571-9577. [PMID: 36399113 DOI: 10.1021/acs.nanolett.2c03715] [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
Monolayer PtTe2 is a narrow gap semiconductor while Pt2Te2 is a metal. Here we show that the former can be transformed into the latter by reaction with vapor-deposited Pt atoms. The transformation occurs by nucleating the Pt2Te2 phase within PtTe2 islands, so that a metal-semiconductor junction is formed. A flat band structure is found with the Fermi level of the metal aligning with that of the intrinsically p-doped PtTe2. This is achieved by an interface dipole that accommodates the ∼0.2 eV shift in the work functions of the two materials. First-principles calculations indicate that the origin of the interface dipole is the atomic scale charge redistributions at the heterojunction. The demonstrated compositional phase transformation of a 2D semiconductor into a 2D metal is a promising approach for making in-plane metal contacts that are required for efficient charge injection and is of particular interest for semiconductors with large spin-orbit coupling, like PtTe2.
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Affiliation(s)
- Kinga Lasek
- Department of Physics, University of South Florida, Tampa, Florida 33620, United States
| | - Jingfeng Li
- Department of Physics, University of South Florida, Tampa, Florida 33620, United States
| | - Mahdi Ghorbani-Asl
- Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany
| | - Salma Khatun
- Department of Physics, University of South Florida, Tampa, Florida 33620, United States
| | - Onyedikachi Alanwoko
- Department of Physics, University of South Florida, Tampa, Florida 33620, United States
| | - Vimukthi Pathirage
- Department of Physics, University of South Florida, Tampa, Florida 33620, United States
| | - Arkady V Krasheninnikov
- Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany
- Department of Applied Physics, Aalto University, P.O. Box 11100, 00076 Aalto, Finland
| | - Matthias Batzill
- Department of Physics, University of South Florida, Tampa, Florida 33620, United States
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9
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Zhu T, Ruan W, Wang YQ, Tsai HZ, Wang S, Zhang C, Wang T, Liou F, Watanabe K, Taniguchi T, Neaton JB, Weber-Bargioni A, Zettl A, Qiu ZQ, Zhang G, Wang F, Moore JE, Crommie MF. Imaging gate-tunable Tomonaga-Luttinger liquids in 1H-MoSe 2 mirror twin boundaries. NATURE MATERIALS 2022; 21:748-753. [PMID: 35710632 DOI: 10.1038/s41563-022-01277-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Accepted: 04/25/2022] [Indexed: 06/15/2023]
Abstract
One-dimensional electron systems exhibit fundamentally different properties than higher-dimensional systems. For example, electron-electron interactions in one-dimensional electron systems have been predicted to induce Tomonaga-Luttinger liquid behaviour. Naturally occurring grain boundaries in single-layer transition metal dichalcogenides exhibit one-dimensional conducting channels that have been proposed to host Tomonaga-Luttinger liquids, but charge density wave physics has also been suggested to explain their behaviour. Clear identification of the electronic ground state of this system has been hampered by an inability to electrostatically gate such boundaries and tune their charge carrier concentration. Here we present a scanning tunnelling microscopy and spectroscopy study of gate-tunable mirror twin boundaries in single-layer 1H-MoSe2 devices. Gating enables scanning tunnelling microscopy and spectroscopy for different mirror twin boundary electron densities, thus allowing precise characterization of electron-electron interaction effects. Visualization of the resulting mirror twin boundary electronic structure allows unambiguous identification of collective density wave excitations having two velocities, in quantitative agreement with the spin-charge separation predicted by finite-length Tomonaga-Luttinger liquid theory.
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Affiliation(s)
- Tiancong Zhu
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
- Department of Physics, University of California, Berkeley, CA, USA
| | - Wei Ruan
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
- Department of Physics, University of California, Berkeley, CA, USA.
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai, China.
| | - Yan-Qi Wang
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
- Department of Physics, University of California, Berkeley, CA, USA
| | - Hsin-Zon Tsai
- Department of Physics, University of California, Berkeley, CA, USA
| | - Shuopei Wang
- Beijing National Laboratory for Condensed Matter Physics, Key Laboratory for Nanoscale Physics and Devices, Institute of Physics, Chinese Academy of Sciences, Beijing, China
- Songshan Lake Materials Laboratory, Dongguan, China
| | - Canxun Zhang
- Department of Physics, University of California, Berkeley, CA, USA
- Kavli Energy Nano Sciences Institute, University of California Berkeley and Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Tianye Wang
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
- Department of Physics, University of California, Berkeley, CA, USA
| | - Franklin Liou
- Department of Physics, University of California, Berkeley, CA, USA
- Kavli Energy Nano Sciences Institute, University of California Berkeley and Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Japan
| | - Jeffrey B Neaton
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
- Department of Physics, University of California, Berkeley, CA, USA
| | - Alexander Weber-Bargioni
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
- Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Alex Zettl
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
- Department of Physics, University of California, Berkeley, CA, USA
- Kavli Energy Nano Sciences Institute, University of California Berkeley and Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Z Q Qiu
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
- Department of Physics, University of California, Berkeley, CA, USA
| | - Guangyu Zhang
- Beijing National Laboratory for Condensed Matter Physics, Key Laboratory for Nanoscale Physics and Devices, Institute of Physics, Chinese Academy of Sciences, Beijing, China
- Songshan Lake Materials Laboratory, Dongguan, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Feng Wang
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
- Department of Physics, University of California, Berkeley, CA, USA.
- Kavli Energy Nano Sciences Institute, University of California Berkeley and Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
| | - Joel E Moore
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
- Department of Physics, University of California, Berkeley, CA, USA.
- Kavli Energy Nano Sciences Institute, University of California Berkeley and Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
| | - Michael F Crommie
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
- Department of Physics, University of California, Berkeley, CA, USA.
- Kavli Energy Nano Sciences Institute, University of California Berkeley and Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
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10
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Lee Y, Lee J, Chung H, Kim J, Lee Z. In Situ Scanning Transmission Electron Microscopy Study of MoS 2 Formation on Graphene with a Deep-Learning Framework. ACS OMEGA 2021; 6:21623-21630. [PMID: 34471766 PMCID: PMC8388093 DOI: 10.1021/acsomega.1c03002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/08/2021] [Accepted: 08/02/2021] [Indexed: 06/13/2023]
Abstract
Atomic-scale information is essential for understanding and designing unique structures and properties of two-dimensional (2D) materials. Recent developments in in situ transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) enable research to provide abundant insights into the growth of nanomaterials. In this study, 2D MoS2 is synthesized on a suspended graphene substrate inside a TEM column through thermolysis of the ammonium tetrathiomolybdate (NH4)2MoS4 precursor at 500 °C. To avoid misinterpretation of the in situ STEM images, a deep-learning framework, DeepSTEM, is developed. The DeepSTEM framework successfully reconstructs an object function in atomic-resolution STEM imaging for accurate determination of the atomic structure and dynamic analysis. In situ STEM imaging with DeepSTEM enables observation of the edge configuration, formation, and reknitting progress of MoS2 clusters with the formation of a mirror twin boundary. The synthesized MoS2/graphene heterostructure shows various twist angles, as revealed by atomic-resolution TEM. This deep-learning framework-assisted in situ STEM imaging provides atomic information for in-depth studies on the growth and structure of 2D materials and shows the potential use of deep-learning techniques in 2D material research.
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Affiliation(s)
- Yeongdong Lee
- Center
for Multidimensional Carbon Materials, Institute
for Basic Science (IBS), Ulsan 44919, Republic of Korea
- Department
of Materials Science and Engineering, Ulsan
National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea
| | - Jongyeong Lee
- Center
for Multidimensional Carbon Materials, Institute
for Basic Science (IBS), Ulsan 44919, Republic of Korea
- Department
of Materials Science and Engineering, Ulsan
National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea
| | - Handolsam Chung
- Center
for Multidimensional Carbon Materials, Institute
for Basic Science (IBS), Ulsan 44919, Republic of Korea
- Department
of Materials Science and Engineering, Ulsan
National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea
| | - Jaemin Kim
- Center
for Multidimensional Carbon Materials, Institute
for Basic Science (IBS), Ulsan 44919, Republic of Korea
- Department
of Materials Science and Engineering, Ulsan
National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea
| | - Zonghoon Lee
- Center
for Multidimensional Carbon Materials, Institute
for Basic Science (IBS), Ulsan 44919, Republic of Korea
- Department
of Materials Science and Engineering, Ulsan
National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea
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11
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Murray C, van Efferen C, Jolie W, Fischer JA, Hall J, Rosch A, Krasheninnikov AV, Komsa HP, Michely T. Band Bending and Valence Band Quantization at Line Defects in MoS 2. ACS NANO 2020; 14:9176-9187. [PMID: 32602698 DOI: 10.1021/acsnano.0c04945] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The variation of the electronic structure normal to 1D defects in quasi-freestanding MoS2, grown by molecular beam epitaxy, is investigated through high resolution scanning tunneling spectroscopy at 5 K. Strong upward bending of valence and conduction bands toward the line defects is found for the 4|4E mirror twin boundary and island edges but not for the 4|4P mirror twin boundary. Quantized energy levels in the valence band are observed wherever upward band bending takes place. Focusing on the common 4|4E mirror twin boundary, density functional theory calculations give an estimate of its charging, which agrees well with electrostatic modeling. We show that the line charge can also be assessed from the filling of the boundary-localized electronic band, whereby we provide a measurement of the theoretically predicted quantized polarization charge at MoS2 mirror twin boundaries. These calculations elucidate the origin of band bending and charging at these 1D defects in MoS2. The 4|4E mirror twin boundary not only impairs charge transport of electrons and holes due to band bending, but holes are additionally subject to a potential barrier, which is inferred from the independence of the quantized energy landscape on either side of the boundary.
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Affiliation(s)
- Clifford Murray
- II. Physikalisches Institut, Universität zu Köln, Cologne D-50937, Germany
| | - Camiel van Efferen
- II. Physikalisches Institut, Universität zu Köln, Cologne D-50937, Germany
| | - Wouter Jolie
- II. Physikalisches Institut, Universität zu Köln, Cologne D-50937, Germany
- Institut für Materialphysik, Westfälische Wilhelms-Universität Münster, Münster D-48149, Germany
| | | | - Joshua Hall
- II. Physikalisches Institut, Universität zu Köln, Cologne D-50937, Germany
| | - Achim Rosch
- Institut für Theoretische Physik, Universität zu Köln, Cologne D-50937, Germany
| | - Arkady V Krasheninnikov
- Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, Dresden D-01328, Germany
- Department of Applied Physics, Aalto University School of Science, Aalto FI-00076, Finland
| | - Hannu-Pekka Komsa
- Department of Applied Physics, Aalto University School of Science, Aalto FI-00076, Finland
- Microelectronics Research Unit, University of Oulu, Oulu FI-90014, Finland
| | - Thomas Michely
- II. Physikalisches Institut, Universität zu Köln, Cologne D-50937, Germany
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12
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Young BT, Pathan MAK, Jiang T, Le D, Marrow N, Nguyen T, Jordan CE, Rahman TS, Popolan-Vaida DM, Vaida ME. Catalytic C 2H 2 synthesis via low temperature CO hydrogenation on defect-rich 2D-MoS 2 and 2D-MoS 2 decorated with Mo clusters. J Chem Phys 2020; 152:074706. [PMID: 32087629 DOI: 10.1063/1.5129712] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Rational design of novel catalytic materials used to synthesize storable fuels via the CO hydrogenation reaction has recently received considerable attention. In this work, defect poor and defect rich 2D-MoS2 as well as 2D-MoS2 decorated with Mo clusters are employed as catalysts for the generation of acetylene (C2H2) via the CO hydrogenation reaction. Temperature programmed desorption is used to study the interaction of CO and H2 molecules with the MoS2 surface as well as the formation of reaction products. The experiments indicate the presence of four CO adsorption sites below room temperature and a competitive adsorption between the CO and H2 molecules. The investigations show that CO hydrogenation is not possible on defect poor MoS2 at low temperatures. However, on defect rich 2D-MoS2, small amounts of C2H2 are produced, which desorb from the surface at temperatures between 170 K and 250 K. A similar C2H2 signal is detected from defect poor 2D-MoS2 decorated with Mo clusters, which indicates that low coordinated Mo atoms on 2D-MoS2 are responsible for the formation of C2H2. Density functional theory investigations are performed to explore possible adsorption sites of CO and understand the formation mechanism of C2H2 on MoS2 and Mo7/MoS2. The theoretical investigation indicates a strong binding of C2H2 on the Mo sites of MoS2 preventing the direct desorption of C2H2 at low temperatures as observed experimentally. Instead, the theoretical results suggest that the experimental data are consistent with a mechanism in which CHO radical dimers lead to the formation of C2H2 that presents an exothermic desorption.
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Affiliation(s)
- Brett T Young
- Department of Chemistry, University of Central Florida, Orlando, Florida 32816, USA
| | - Md Afjal Khan Pathan
- Department of Physics, University of Central Florida, Orlando, Florida 32816, USA
| | - Tao Jiang
- Department of Physics, University of Central Florida, Orlando, Florida 32816, USA
| | - Duy Le
- Department of Physics, University of Central Florida, Orlando, Florida 32816, USA
| | - Nikki Marrow
- Department of Physics, University of Central Florida, Orlando, Florida 32816, USA
| | - Trong Nguyen
- Department of Physics, University of Central Florida, Orlando, Florida 32816, USA
| | - Cody E Jordan
- Department of Physics, University of Central Florida, Orlando, Florida 32816, USA
| | - Talat S Rahman
- Department of Physics, University of Central Florida, Orlando, Florida 32816, USA
| | | | - Mihai E Vaida
- Department of Physics, University of Central Florida, Orlando, Florida 32816, USA
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13
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Karthikeyan J, Komsa HP, Batzill M, Krasheninnikov AV. Which Transition Metal Atoms Can Be Embedded into Two-Dimensional Molybdenum Dichalcogenides and Add Magnetism? NANO LETTERS 2019; 19:4581-4587. [PMID: 31251639 DOI: 10.1021/acs.nanolett.9b01555] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
As compared to bulk solids, large surface-to-volume ratio of two-dimensional (2D) materials may open new opportunities for postsynthesis introduction of impurities into these systems by, for example, vapor deposition. However, it does not work for graphene or h-BN, as the dopant atoms prefer clustering on the surface of the material instead of getting integrated into the atomic network. Using extensive first-principles calculations, we show that counterintuitively most transition metal (TM) atoms can be embedded into the atomic network of the pristine molybdenum dichalcogenides (MoDCs) upon atom deposition at moderate temperatures either as interstitials or substitutional impurities, especially in MoTe2, which has the largest spacing between the host atoms. We further demonstrate that many impurity configurations have localized magnetic moments. By analyzing the trends in energetics and values of the magnetic moments across the periodic table, we rationalize the results through the values of TM atomic radii and the number of (s + d) electrons available for bonding and suggest the most promising TMs for inducing magnetism in MoDCs. Our results are in line with the available experimental data and should further guide the experimental effort toward a simple postsynthesis doping of 2D MoDCs and adding new functionalities to these materials.
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Affiliation(s)
- J Karthikeyan
- Department of Applied Physics , Aalto University , P.O. Box 11100, 00076 Aalto , Finland
| | - Hannu-Pekka Komsa
- Department of Applied Physics , Aalto University , P.O. Box 11100, 00076 Aalto , Finland
| | - Matthias Batzill
- Department of Physics , University of South Florida , Tampa , Florida 33620 , United States
| | - Arkady V Krasheninnikov
- Department of Applied Physics , Aalto University , P.O. Box 11100, 00076 Aalto , Finland
- Institute of Ion Beam Physics and Materials Research , Helmholtz-Zentrum Dresden-Rossendorf , 01328 Dresden , Germany
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