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Phase-selective synthesis of 1T′ MoS2 monolayers and heterophase bilayers

Abstract

Two-dimensional (2D) MoS2, which has great potential for optoelectronic and other applications, is thermodynamically stable and hence easily synthesized in its semiconducting 2H phase. In contrast, growth of its metastable 1T and 1T′ phases is hampered by their higher formation energy. Here we use theoretical calculations to design a potassium (K)-assisted chemical vapour deposition method for the phase-selective growth of 1T′ MoS2 monolayers and 1T′/2H heterophase bilayers. This is realized by tuning the concentration of K in the growth products to invert the stability of the 1T′ and 2H phases. The synthesis of 1T′ MoS2 monolayers with high phase purity allows us to characterize their intrinsic optical and electrical properties, revealing a characteristic in-plane anisotropy. This phase-controlled bottom-up synthesis offers a simple and efficient way of manipulating the relevant device structures, and provides a general approach for producing other metastable-phase 2D materials with unique properties.

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Data availability

The data that support the findings of this study are available from the corresponding author upon request.

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Acknowledgements

L.J. acknowledges the National Natural Science Foundation of China (grant numbers 21573125, 21322303 and 51372134) and the Tsinghua University Initiative Scientific Research Program. L.X. acknowledges the NSFC (grant number 21673058), the Key Research Program of Frontier Sciences of CAS (grant number QYZDB-SSW-SYS031), the Strategic Priority Research Program of Chinese Academy of Sciences (grant number XDB30000000) and the Beijing Nova Program-Joint Project (grant number Z171100001117129). X.J. acknowledges the National Natural Science Foundation of China (grant numbers 11574304 and 11774338) and the Youth Innovation Promotion Association CAS (grant number 2016109). L.G. acknowledges the National Program on Key Basic Research Project (grant number 2014CB921002), The Strategic Priority Research Program of Chinese Academy of Sciences (grant number XDB07030200) and the National Natural Science Foundation of China (grant numbers 51522212, 51421002 and 51672307). P.L. acknowledges the National Natural Science Foundation of China (grant number 61675032), the National Basic Research Program of China (973 Program) under grant number 2014CB643900 and the Open Program of State Key Laboratory of Functional Materials for Informatics. We thank X. Yan for TEM data analysis and X. Ping for HER measurements.

Author information

L.J. and L.X. cosupervised this project. L.J. and L.L. conceived the ideas. L.L., J.W., L.S., J.Z. and L.X. performed the experiments. L.W., Q.W., S.H., P.L., M.Y. and X.J. carried out the theoretical calculations. X.L. and L.G. performed the STEM characterizations. L.J., L.L., J.W. and L.X. co-wrote the manuscript. All authors read the manuscript and commented on it.

Correspondence to Liming Xie or Liying Jiao.

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Supplementary Figures 1–17, Supplementary Tables 1–2, Supplementary References 1–17

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Further reading

Fig. 1: Schematics for the phase-controlled synthesis strategy.
Fig. 2: Selective CVD growth of 1T′-phase and 2H-phase MoS2 monolayers.
Fig. 3: Vertically stacked 1T′/2H heterophase bilayers.
Fig. 4: In-plane anisotropic spectroscopic characterizations.
Fig. 5: In-plane anisotropic electrical characterizations.
Fig. 6: Electrochemical performance of CVD-grown 1T′ and 2H MoS2 flakes.