Abstract

A decade of intense research on two-dimensional (2D) atomic crystals has revealed that their properties can differ greatly from those of the parent compound1,2. These differences are governed by changes in the band structure due to quantum confinement and are most profound if the underlying lattice symmetry changes3,4. Here we report a high-quality 2D electron gas in few-layer InSe encapsulated in hexagonal boron nitride under an inert atmosphere. Carrier mobilities are found to exceed 103 cm2 V−1 s−1 and 104 cm2 V−1 s−1 at room and liquid-helium temperatures, respectively, allowing the observation of the fully developed quantum Hall effect. The conduction electrons occupy a single 2D subband and have a small effective mass. Photoluminescence spectroscopy reveals that the bandgap increases by more than 0.5 eV with decreasing the thickness from bulk to bilayer InSe. The band-edge optical response vanishes in monolayer InSe, which is attributed to the monolayer's mirror-plane symmetry. Encapsulated 2D InSe expands the family of graphene-like semiconductors and, in terms of quality, is competitive with atomically thin dichalcogenides5,6,7 and black phosphorus8,9,10,11.

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Acknowledgements

This work was supported by the European Research Council, the Graphene Flagship, the Engineering and Physical Sciences Research Council (EPSRC, UK) and The Royal Society. D.A.B. and I.V.G. acknowledge support from the Marie Curie programme SPINOGRAPH (Spintronics in Graphene). A.M. acknowledges support of the EPSRC Early Career Fellowship EP/N007131/1. S.V.M. was supported by the NUST MISiS (grant K1-2015-046) and the Russian Foundation for Basic Research (RFBR15-02-01221 and RFBR14-02-00792). V.F. acknowledges support from the ERC Synergy Grant Hetero2D, the EPSRC grant EP/N010345/1 and the Lloyd Register Foundation Nanotechnology grant, and V.Z. from the European Graphene Flagship Project. Measurements in high magnetic field were supported by the High Field Magnet Laboratory–Radboud University/Foundation for Fundamental Research on Matter, member of the European Magnetic Field Laboratory, and by the EPSRC via its membership to the EMFL (grant EP/N01085X/1). We thank M. Mohammed for assisting with UV PL measurements.

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Affiliations

  1. School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK

    • Denis A. Bandurin
    • , Geliang L. Yu
    • , Artem Mishchenko
    • , Irina V. Grigorieva
    • , Vladimir I. Fal'ko
    • , Andre K. Geim
    •  & Yang Cao
  2. Skolkovo Institute of Science and Technology, Nobel St. 3, 143026 Moscow, Russia

    • Anastasia V. Tyurnina
  3. National Graphene Institute, University of Manchester, Manchester M13 9PL, UK

    • Anastasia V. Tyurnina
    • , Viktor Zólyomi
    • , Roshan Krishna Kumar
    • , Roman V. Gorbachev
    • , Konstantin S. Novoselov
    • , Vladimir I. Fal'ko
    •  & Yang Cao
  4. Institute of Microelectronics Technology and High Purity Materials, RAS, Chernogolovka 142432, Russia

    • Sergey V. Morozov
  5. National University of Science and Technology ‘MISiS’, Leninsky Pr. 4, 119049 Moscow, Russia

    • Sergey V. Morozov
  6. School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, UK

    • Zakhar R. Kudrynskyi
    • , Amalia Patanè
    •  & Laurence Eaves
  7. High Field Magnet Laboratory (HFML –EMFL), Radboud University, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands

    • Sergio Pezzini
    •  & Uli Zeitler
  8. National Academy of Sciences of Ukraine, Institute for Problems of Materials Science, UA-58001 Chernovtsy, Ukraine

    • Zakhar D. Kovalyuk

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Contributions

D.A.B., G.L.Y., R.K.K., A.M. and S.V.M. performed transport measurements and A.V.T. carried out optical studies. D.A.B. and A.V.T. analysed experimental data with help from A.K.G. and V.I.F. Y.C. fabricated devices and co-supervised the project with help from R.V.G. V.Z. and V.I.F. provided theory support. Z.R.K., Z.D.K. and A.P. provided bulk InSe crystals. D.A.B., V.I.F. and A.K.G. wrote the manuscript. All authors contributed to discussions.

Competing interests

The authors declare no competing financial interests.

Corresponding authors

Correspondence to Andre K. Geim or Yang Cao.

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DOI

https://doi.org/10.1038/nnano.2016.242

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