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      Spectroscopic studies of atomic defects and bandgap renormalization in semiconducting monolayer transition metal dichalcogenides

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          Abstract

          Assessing atomic defect states and their ramifications on the electronic properties of two-dimensional van der Waals semiconducting transition metal dichalcogenides (SC-TMDs) is the primary task to expedite multi-disciplinary efforts in the promotion of next-generation electrical and optical device applications utilizing these low-dimensional materials. Here, with electron tunneling and optical spectroscopy measurements with density functional theory, we spectroscopically locate the mid-gap states from chalcogen-atom vacancies in four representative monolayer SC-TMDs—WS 2, MoS 2, WSe 2, and MoSe 2—, and carefully analyze the similarities and dissimilarities of the atomic defects in four distinctive materials regarding the physical origins of the missing chalcogen atoms and the implications to SC-mTMD properties. In addition, we address both quasiparticle and optical energy gaps of the SC-mTMD films and find out many-body interactions significantly enlarge the quasiparticle energy gaps and excitonic binding energies, when the semiconducting monolayers are encapsulated by non-interacting hexagonal boron nitride layers.

          Abstract

          Atomic defects impact the electronic properties of atomically thin transition metal dichalcogenides (TMDs). Here, the authors locate the mid-gap states originating from single chalcogen-atom vacancies in four representative semiconducting monolayer films, and analyse their implications for the semiconducting properties of atomically thin TMDs through electron tunneling and optical spectroscopy measurements.

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            Efficient iterative schemes forab initiototal-energy calculations using a plane-wave basis set

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              Exploring atomic defects in molybdenum disulphide monolayers

              Defects usually play an important role in tailoring various properties of two-dimensional materials. Defects in two-dimensional monolayer molybdenum disulphide may be responsible for large variation of electric and optical properties. Here we present a comprehensive joint experiment–theory investigation of point defects in monolayer molybdenum disulphide prepared by mechanical exfoliation, physical and chemical vapour deposition. Defect species are systematically identified and their concentrations determined by aberration-corrected scanning transmission electron microscopy, and also studied by ab-initio calculation. Defect density up to 3.5 × 1013 cm−2 is found and the dominant category of defects changes from sulphur vacancy in mechanical exfoliation and chemical vapour deposition samples to molybdenum antisite in physical vapour deposition samples. Influence of defects on electronic structure and charge-carrier mobility are predicted by calculation and observed by electric transport measurement. In light of these results, the growth of ultra-high-quality monolayer molybdenum disulphide appears a primary task for the community pursuing high-performance electronic devices.
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                Author and article information

                Contributors
                yongsung.kim@kriss.re.kr
                syjung@kriss.re.kr
                Journal
                Nat Commun
                Nat Commun
                Nature Communications
                Nature Publishing Group UK (London )
                2041-1723
                23 August 2019
                23 August 2019
                2019
                : 10
                : 3825
                Affiliations
                [1 ]ISNI 0000 0001 2301 0664, GRID grid.410883.6, Quantum Technology Institute, , Korea Research Institute of Standards and Science, ; Daejeon, 34113 Korea
                [2 ]ISNI 0000 0001 0722 6377, GRID grid.254230.2, Department of Physics, , Chungnam National University, ; Daejeon, 34134 Korea
                [3 ]ISNI 0000 0004 1784 4496, GRID grid.410720.0, Center for Theoretical Physics of Complex Systems, , Institute for Basic Science, ; Daejeon, 34126 Korea
                [4 ]ISNI 0000 0001 0789 6880, GRID grid.21941.3f, Advanced Materials Laboratory, , National Institute for Materials Science, ; 1-1 Namiki, Tsukuba, 305-0044 Japan
                Author information
                http://orcid.org/0000-0003-3701-8119
                http://orcid.org/0000-0002-6057-2997
                http://orcid.org/0000-0003-3885-9999
                Article
                11751
                10.1038/s41467-019-11751-3
                6707146
                31444331
                fc2393bc-8acc-4e29-a451-77e791e09e41
                © The Author(s) 2019

                Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.

                History
                : 7 February 2019
                : 5 August 2019
                Funding
                Funded by: FundRef https://doi.org/10.13039/501100003706, Korea Research Institute of Standards and Science (KRISS);
                Award ID: KRISS-2018-GP2018-0019
                Award Recipient :
                Funded by: FundRef https://doi.org/10.13039/501100003725, National Research Foundation of Korea (NRF);
                Award ID: NRF-2016R1A2B4008816
                Award ID: NRF-2019R1A2C2004007
                Award Recipient :
                Categories
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                Custom metadata
                © The Author(s) 2019

                Uncategorized
                materials science,condensed-matter physics,materials for devices,materials for optics,nanoscale materials

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