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Borophene synthesis beyond the single-atomic-layer limit

Nature Materials volume 21, pages 35–40 (2022)Cite this article

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Abstract

Synthetic two-dimensional (2D) materials have no bulk counterparts and typically exist as single atomic layers due to substrate-stabilized growth. Multilayer formation, although broadly sought for structure and property tuning, has not yet been achieved in the case of synthetic 2D boron: that is, borophene1,2. Here, we experimentally demonstrate the synthesis of an atomically well-defined borophene polymorph beyond the single-atomic-layer (SL) limit. The structure of this bilayer (BL) borophene is consistent with two covalently bonded α-phase layers (termed BL-α borophene) as evidenced from bond-resolved scanning tunnelling microscopy, non-contact atomic force microscopy and density functional theory calculations. While the electronic density of states near the Fermi level of BL-α borophene is similar to SL borophene polymorphs, field-emission resonance spectroscopy reveals distinct interfacial charge transfer doping and a heightened local work function exceeding 5 eV. The extension of borophene polymorphs beyond the SL limit significantly expands the phase space for boron-based nanomaterials.

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Fig. 1: Growth of BL borophene on Ag(111).
Fig. 2: Atomic-scale imaging of BL borophene.
Fig. 3: Lattice structure of BL-α borophene.
Fig. 4: Spectroscopic characterization of BL-α borophene.

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All data needed to evaluate the conclusions in the paper are present in the paper and/or the Supplementary Information. Additional data related to this paper may be requested from the authors.

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Acknowledgements

X.L., Q.L., M.S.R. and M.C.H. acknowledge support from the Office of Naval Research (ONR N00014−17-1-2993) and the National Science Foundation Materials Research Science and Engineering Center (NSF DMR-1720139). Q.R. and B.I.Y. acknowledge support from the Electronics Division of the US Army Research Office (W911NF-16-1-0255) and the Robert Welch Foundation (C-1590).

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Author notes

  1. These authors contributed equally: Xiaolong Liu, Qiucheng Li, Qiyuan Ruan.

Authors and Affiliations

  1. Applied Physics Graduate Program, Northwestern University, Evanston, IL, USA

    Xiaolong Liu & Mark C. Hersam

  2. Department of Materials Science and Engineering, Northwestern University, Evanston, IL, USA

    Qiucheng Li, Matthew S. Rahn & Mark C. Hersam

  3. Department of Materials Science and NanoEngineering, Rice University, Houston, TX, USA

    Qiyuan Ruan & Boris I. Yakobson

  4. Department of Chemistry, Rice University, Houston, TX, USA

    Boris I. Yakobson

  5. Department of Chemistry, Northwestern University, Evanston, IL, USA

    Mark C. Hersam

  6. Department of Electrical and Computer Engineering, Northwestern University, Evanston, IL, USA

    Mark C. Hersam

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  1. Xiaolong Liu
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Contributions

X.L. and M.C.H. conceived the project. X.L., Q.L. and M.S.R. performed sample preparation and STM/FER/AFM measurements. Q.R. and B.I.Y. designed the models. Q.R. performed the DFT simulations. X.L. provided assistance with model construction. All authors contributed to data interpretation and manuscript writing.

Corresponding authors

Correspondence to Boris I. Yakobson or Mark C. Hersam.

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The authors declare no competing interests.

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Peer review information Nature Materials thanks Ivan Bozovic and Guy Le Lay for their contribution to the peer review of this work.

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Supplementary Information

Supplementary Figs. 1–11.

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Liu, X., Li, Q., Ruan, Q. et al. Borophene synthesis beyond the single-atomic-layer limit. Nat. Mater. 21, 35–40 (2022). https://doi.org/10.1038/s41563-021-01084-2

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