Metastable 1T′-phase transition metal dichalcogenides (1T′-TMDs) with semi-metallic natures have attracted increasing interest owing to their uniquely distorted structures and fascinating phase-dependent physicochemical properties. However, the synthesis of high-quality metastable 1T′-TMD crystals, especially for the group VIB TMDs, remains a challenge. Here, we report a general synthetic method for the large-scale preparation of metastable 1T′-phase group VIB TMDs, including WS2, WSe2, MoS2, MoSe2, WS2xSe2(1−x) and MoS2xSe2(1−x). We solve the crystal structures of 1T′-WS2, -WSe2, -MoS2 and -MoSe2 with single-crystal X-ray diffraction. The as-prepared 1T′-WS2 exhibits thickness-dependent intrinsic superconductivity, showing critical transition temperatures of 8.6 K for the thickness of 90.1 nm and 5.7 K for the single layer, which we attribute to the high intrinsic carrier concentration and the semi-metallic nature of 1T′-WS2. This synthesis method will allow a more systematic investigation of the intrinsic properties of metastable TMDs.
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The X-ray crystallographic coordinates for the structure reported in this study have been deposited at the Cambridge Crystallographic Data Centre under deposition numbers CSD 2062455, 2062456, 2062457 and 2062458. These data can be obtained free of charge from https://www.ccdc.cam.ac.uk/. Other data that support the findings of this study are available from the corresponding author upon reasonable request.
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H.Z. acknowledges support from ITC via the Hong Kong Branch of National Precious Metals Material Engineering Research Center (NPMM), the Start-Up Grant (project no. 9380100) and grants (project nos. 9610478 and 1886921) from the City University of Hong Kong and the Science Technology and Innovation Committee of Shenzhen Municipality (grant no. JCYJ20200109143412311). Q.H. acknowledges the funding support from the Start-Up Grant (project no. 9610482) from the City University of Hong Kong. Y.S. and Y.M. acknowledge the funding support from the National Natural Science Foundation of China (under grant no. 11534003) and the Program for JLU Science and Technology Innovative Research Team and Science Challenge Project (no. TZ2016001). K.H. and D.V.M.R. acknowledge funding from the Accelerated Materials Development for Manufacturing Program at A*STAR via the AME Programmatic Fund by the Agency for Science, Technology and Research under grant no. A1898b0043. R.V.R. and V.S. acknowledge support by grants from the National Research Foundation, Prime Minister’s Office, Singapore, under its Campus for Research Excellence and Technological Enterprise (CREATE) programme. X.R.W. acknowledges supports from Academic Research Fund Tier 2 (grant no. MOE-T2EP50120-006) from Singapore Ministry of Education. We also thank W. Fernando for his generosity in providing us with his PhD thesis for our reference and S. Morris for the helpful discussions. We acknowledge the Facility for Analysis, Characterization, Testing and Simulation, Nanyang Technological University, Singapore, for use of their electron microscopy and X-ray facilities.
The authors declare no competing interests.
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Supplementary Figs. 1–64, Tables 1–7 and Notes 1–5.
The CIF document of the 1T′-WS2 crystal.
The CIF document of the 1T′-WSe2 crystal.
The CIF document of the 1T′-MoS2 crystal.
The CIF document of the 1T′-MoSe2 crystal.
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Lai, Z., He, Q., Tran, T.H. et al. Metastable 1T′-phase group VIB transition metal dichalcogenide crystals. Nat. Mater. (2021). https://doi.org/10.1038/s41563-021-00971-y