Investigations of two-dimensional transition-metal chalcogenides (TMCs) have recently revealed interesting physical phenomena, including the quantum spin Hall effect1,2, valley polarization3,4 and two-dimensional superconductivity5, suggesting potential applications for functional devices6,7,8,9,10. However, of the numerous compounds available, only a handful, such as Mo- and W-based TMCs, have been synthesized, typically via sulfurization11,12,13,14,15, selenization16,17 and tellurization18 of metals and metal compounds. Many TMCs are difficult to produce because of the high melting points of their metal and metal oxide precursors. Molten-salt-assisted methods have been used to produce ceramic powders at relatively low temperature19 and this approach20 was recently employed to facilitate the growth of monolayer WS2 and WSe2. Here we demonstrate that molten-salt-assisted chemical vapour deposition can be broadly applied for the synthesis of a wide variety of two-dimensional (atomically thin) TMCs. We synthesized 47 compounds, including 32 binary compounds (based on the transition metals Ti, Zr, Hf, V, Nb, Ta, Mo, W, Re, Pt, Pd and Fe), 13 alloys (including 11 ternary, one quaternary and one quinary), and two heterostructured compounds. We elaborate how the salt decreases the melting point of the reactants and facilitates the formation of intermediate products, increasing the overall reaction rate. Most of the synthesized materials in our library are useful, as supported by evidence of superconductivity in our monolayer NbSe2 and MoTe2 samples21,22 and of high mobilities in MoS2 and ReS2. Although the quality of some of the materials still requires development, our work opens up opportunities for studying the properties and potential application of a wide variety of two-dimensional TMCs.
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The authors declare no competing interests.
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This work was supported by the Singapore National Research Foundation under NRF award number NRF-NRFF2013-08, Tier 2 MOE2016-T2-2-153, MOE2016-T2-1-131, MOE2015-T2-2-007, Tier 1 RG164/15, Tier 1 RG4/17, CoE Industry Collaboration Grant WINTECH-NTU and the A*Star QTE programme. T.Y. acknowledges MOE Tier 1 RG100/15. J.L. and K.S. acknowledge the financial support of JST-ACCEL and JSPS KAKENHI (JP16H06333 and P16382). The work in SICCAS was supported by the National Key Research and Development Program of China (2016YFB0700204) and the National Natural Science Foundation of China (51502327). The work at IOP was supported by the Ministry of Science and Technology of China (grant numbers 2014CB920904, 2015CB921101 and 2016YFA0300600), the National Natural Science Foundation of China (grant numbers 11174340, 912212012, 11527806 and 91421303) and the Chinese Academy of Sciences (grant numbers XDB07010100). H.L. acknowledges the Singapore National Research Foundation for support under NRF award number NRF-NRFF2013-03. The work at Rice was supported by the US Department of Energy (DE-SC0012547) and by the R. Welch Foundation (C-1590).
Nature thanks D. Akinwande, M. Terrones and the other anonymous reviewer(s) for their contribution to the peer review of this work.
This file contains Supplementary Materials and Methods, Supplementary Text and Data, Supplementary Figures 1-63, Supplementary Tables 1-5 and Supplementary References – see contents page for details
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