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Valley and band structure engineering of folded MoS2 bilayers

Nature Nanotechnology volume 9, pages 825–829 (2014)Cite this article

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Abstract

Artificial structures made of stacked two-dimensional crystals have recently been the focus of intense research activity1. As in twisted or stacked graphene layers2,3,4,5,6, these structures can show unusual behaviours and new phenomena1. Among the various layered compounds that can be exfoliated, transition-metal dichalcogenides7 exhibit interesting properties governed by their structural symmetry8,9 and interlayer coupling10,11,12,13, which are highly susceptible to stacking. Here, we obtain—by folding exfoliated MoS2 monolayers—MoS2 bilayers with different stacking orders, as monitored by second harmonic generation and photoluminescence. Appropriate folding can break the inversion symmetry and suppress interlayer hopping, evoking strong valley14,15,16 and spin17,18,19 polarizations that are not achieved in natural MoS2 bilayers of Bernal stacking20. It can also enlarge the indirect bandgap by more than 100 meV through a decrease in the interlayer coupling. Our work provides an effective and versatile means to engineer transition-metal dichalcogenide materials with desirable electronic and optical properties.

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Figure 1: Microscopy and characterization of monolayer, folded bilayers, and trilayer of MoS2.
Figure 2: Second harmonic generation (SHG) anisotropy and microscopic structures of folded MoS2 bilayers.
Figure 3: Photoluminescence spectra and band structures of MoS2 bilayers with different stacking orders.
Figure 4: Valley and spin polarizations in 2H-like(Mo), 3R-like and 2H bilayers.

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Acknowledgements

This work was supported by the National Natural Science Foundation of China, the National Basic Research Program of China, the Ministry of Education of China and the Shu Guang Project (grant agreements nos. 2014CB921600, 2012CB921400, 11104036, 11104033, 20110071120003, NCET-11-0110 and 11SG05).

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Authors and Affiliations

  1. State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai, 200433, China

    Tao Jiang, Hengrui Liu, Di Huang, Shuai Zhang, Yingguo Li, Xingao Gong, Yuen-Ron Shen, Wei-Tao Liu & Shiwei Wu

  2. Key Laboratory of Micro and Nano Photonic Structures (MOE), Fudan University, Shanghai, 200433, China

    Tao Jiang, Di Huang, Shuai Zhang, Yingguo Li, Yuen-Ron Shen, Wei-Tao Liu & Shiwei Wu

  3. Key Laboratory of Computational Physical Sciences (MOE), Fudan University, Shanghai, 200433, China

    Hengrui Liu & Xingao Gong

  4. Collaborative Innovation Center of Advanced Microstructures, Nanjing, 210093, China

    Xingao Gong, Wei-Tao Liu & Shiwei Wu

  5. Physics Department, University of California at Berkeley, Berkeley, 94720-7300, California, USA

    Yuen-Ron Shen

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  1. Tao Jiang
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Contributions

S.W.W. and W.T.L. designed the project and prepared the manuscript. T.J. prepared the sample and performed the measurements. H.R.L. and X.G.G. carried out the ab initio calculation. D.H., S.Z. and Y.G.L. built the low-temperature experimental set-up. All authors contributed to analysis of the results and writing the manuscript.

Corresponding authors

Correspondence to Xingao Gong, Wei-Tao Liu or Shiwei Wu.

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The authors declare no competing financial interests.

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Jiang, T., Liu, H., Huang, D. et al. Valley and band structure engineering of folded MoS2 bilayers. Nature Nanotech 9, 825–829 (2014). https://doi.org/10.1038/nnano.2014.176

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