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  • Review Article
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A new family of septuple-layer 2D materials of MoSi2N4-like crystals

Nature Reviews Physics volume 6, pages 426–438 (2024)Cite this article

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Abstract

Recently synthesized MoSi2N4 is the first septuple-layer two-dimensional material, which does not naturally occur as a layered crystal, and has been obtained with chemical vapour deposition growth. It can be considered as MoN2 crystal (with a crystal structure of MoS2) intercalating Si2N2 two-dimensional layer (with the structure similar to InSe). The discovery of this material has spurred on research into its electronic properties, and also to the prediction and classification of dozens of other members of the family. Whereas the originally synthesized MoSi2N4 is a semiconductor, some of the members of the family are also metallic, some are magnetic, some showing remarkable properties, such as very high room-temperature electron mobilities. The major interest towards these materials is coming from the septuple-layer structure, which allows not only multiple crystal phases but also complex compositions, in particular those with broken mirror-reflection symmetry against the layer of metal atoms. In this Review, we provide a profile of this new family of materials and discuss the possibilities they open up towards new physics and applications.

Key points

  • Septuple-layer 2D materials have been synthesized: MoSi2N4 and WSi2N4. Such materials can be seen as a layer of MoN2 (has a structure similar to MoS2) intercalated into Si2N2 (has a structure similar to InSe).

  • It is possible to intercalate more layers of MoN2 between SiN layers, so derivatives such as MoSi2N4(MoN)4n have also been grown.

  • Potentially many other similar materials of the type MA2Z4 can be created. Here, M can stand for elements of transition metal groups IVB, VB and VIB; A for Si or Ge; and Z for N, P or As.

  • Janus structures with broken out-of-plane inversion symmetry (as, for instance, MoSiGeN4) are possible. Such structures would have a built-in dipole moment and would be of interest for catalysis and optoelectronic applications.

  • Electronic properties of these materials are predicted to be very attractive. For instance, room-temperature hole mobilities exceeding 105 cm2 (V s)−1 have been predicted for α2-WSi2Sb4.

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Fig. 1: Structure of MoSi2N4 family.
Fig. 2: Transmission electron microscopy study of MoSi2N4(MoN)4.
Fig. 3: Valley-contrasting properties of the MA2Z4 family.
Fig. 4: Contacts to MA2Z4 structures.
Fig. 5: Different excitons and relaxation processes.
Fig. 6: Band alignment and energy gaps in MoSi2N4–MoS2 van der Waals heterostructure.
Fig. 7: Photocatalytic properties of MA2Z4 materials.

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Acknowledgements

T.L. thanks Swiss National Foundation Research Grant 200021_197107. D.A.B. and K.S.N. acknowledge support from the Ministry of Education, Singapore (Research Centre of Excellence award to the Institute for Functional Intelligent Materials, I-FIM, project number EDUNC-33-18-279-V12). K.S.N. acknowledges support from the Royal Society (UK, grant number RSRP\R\190000) and the National Research Foundation, Singapore under its AI Singapore Programme (AISG Award No: AISG3-RP-2022-028).

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Authors and Affiliations

  1. Paul Scherrer Institute, Villigen, Switzerland

    T. Latychevskaia

  2. Department of Materials Science and Engineering, National University of Singapore, Singapore, Singapore

    D. A. Bandurin

  3. Institute for Functional Intelligent Materials, National University of Singapore, Singapore, Singapore

    K. S. Novoselov

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  1. T. Latychevskaia
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  3. K. S. Novoselov
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Latychevskaia, T., Bandurin, D.A. & Novoselov, K.S. A new family of septuple-layer 2D materials of MoSi2N4-like crystals. Nat Rev Phys 6, 426–438 (2024). https://doi.org/10.1038/s42254-024-00728-x

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