Letter

Structural phase transition in monolayer MoTe2 driven by electrostatic doping

  • Nature volume 550, pages 487491 (26 October 2017)
  • doi:10.1038/nature24043
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Abstract

Monolayers of transition-metal dichalcogenides (TMDs) exhibit numerous crystal phases with distinct structures, symmetries and physical properties1,2,3. Exploring the physics of transitions between these different structural phases in two dimensions4 may provide a means of switching material properties, with implications for potential applications. Structural phase transitions in TMDs have so far been induced by thermal or chemical means5,6; purely electrostatic control over crystal phases through electrostatic doping was recently proposed as a theoretical possibility, but has not yet been realized7,8. Here we report the experimental demonstration of an electrostatic-doping-driven phase transition between the hexagonal and monoclinic phases of monolayer molybdenum ditelluride (MoTe2). We find that the phase transition shows a hysteretic loop in Raman spectra, and can be reversed by increasing or decreasing the gate voltage. We also combine second-harmonic generation spectroscopy with polarization-resolved Raman spectroscopy to show that the induced monoclinic phase preserves the crystal orientation of the original hexagonal phase. Moreover, this structural phase transition occurs simultaneously across the whole sample. This electrostatic-doping control of structural phase transition opens up new possibilities for developing phase-change devices based on atomically thin membranes.

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Acknowledgements

We thank S. Zhou, K. Deng and W. Yang from Tsinghua University for providing a 1T′ MoTe2 crystal for reference. This work was supported in part by the Director, Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division, of the US Department of Energy under contract no. DE-AC02-05CH11231, within the ‘Light-Material Interactions in Energy Conversion’ Energy Frontier Research Center (for optical measurements); under the ‘van der Waals Heterostructures Program’ (for transport studies); and by the National Science Foundation (NSF) under grant EFMA-154274 (for device design and fabrication). Y.L., Y.Z., and E.J.R. acknowledge support from the Army Research Office (grant W911NF-15-1-0570); the Office of Naval Research (grant N00014-15-1-2697); the NSF (grants DMR-1455050 and EECS-1436626); and from the Stanford Graduate Fellowship programme.

Author information

Author notes

    • Ying Wang
    •  & Jun Xiao

    These authors contributed equally to this work.

Affiliations

  1. NSF Nanoscale Science and Engineering Center (NSEC), 3112 Etcheverry Hall, University of California, Berkeley, California 94720, USA.

    • Ying Wang
    • , Jun Xiao
    • , Hanyu Zhu
    • , Yousif Alsaid
    • , King Yan Fong
    • , Siqi Wang
    • , Yuan Wang
    •  & Xiang Zhang
  2. Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, USA.

    • Yao Li
    • , Yao Zhou
    •  & Evan J. Reed
  3. Materials Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720, USA

    • Wu Shi
    • , Alex Zettl
    •  & Xiang Zhang
  4. Kavli Energy NanoSciences Institute and Department of Physics, University of California, Berkeley, California 94720, USA

    • Wu Shi
    •  & Alex Zettl
  5. Department of Physics, King Abdulaziz University, Jeddah 21589, Saudi Arabia

    • Xiang Zhang

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Contributions

Ying W., J.X. and X.Z. initiated the research and designed the experiments; Ying W., J.X. and H.Z. performed Raman measurements; J.X. and Ying W. conducted gate-dependent SHG spectroscopy and mapping; Y.A. and J.X. prepared monolayer MoTe2; and Ying W. fabricated and characterized devices. Ying W. measured the doping level with assistance from K.Y.F., S.W. and W.S. (W.S. was under the guidance of A.Z); Y.L. and Y.Z. performed theoretical calculations under the guidance of E.J.R.; Ying W., J.X., H.Z., Y.Z, W.S., Yuan W., E.J.R. and X.Z. analysed data; Ying W., J.X., H.Z., Y.Z., Yuan W., E.J.R. and X.Z. wrote the manuscript. X.Z. and Yuan W. guided the work.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Xiang Zhang.

Reviewer Information Nature thanks A. Castro Neto, Y. Iwasa and R. Simpson for their contribution to the peer review of this work.

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