Experimental realization of two-dimensional boron sheets

Abstract

A variety of two-dimensional materials have been reported in recent years, yet single-element systems such as graphene and black phosphorus have remained rare. Boron analogues have been predicted, as boron atoms possess a short covalent radius and the flexibility to adopt sp2 hybridization, features that favour the formation of two-dimensional allotropes, and one example of such a borophene material has been reported recently. Here, we present a parallel experimental work showing that two-dimensional boron sheets can be grown epitaxially on a Ag(111) substrate. Two types of boron sheet, a β12 sheet and a χ3 sheet, both exhibiting a triangular lattice but with different arrangements of periodic holes, are observed by scanning tunnelling microscopy. Density functional theory simulations agree well with experiments, and indicate that both sheets are planar without obvious vertical undulations. The boron sheets are quite inert to oxidization and interact only weakly with their substrate. We envisage that such boron sheets may find applications in electronic devices in the future.

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Figure 1: Formation of 2D boron sheets on Ag(111).
Figure 2: Structure models of S1 and S2 phases of 2D boron sheets based on DFT calculations.
Figure 3: XPS results for 2D boron sheets on Ag(111) after exposure to air.

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Acknowledgements

The authors thank Qinlin Guo for useful discussions regarding XPS data analysis. This work was supported by the MOST of China (grant numbers 2012CB921703, 2013CB921702 and 2013CBA01600), the NSF of China (grant numbers 11334011, 11322431, 11174344 and 91121003), and the Strategic Priority Research Program of the Chinese Academy of Sciences (grant number XDB07020100).

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K.W. and L.C. designed the experiments. B.F., L.C., Q.Z., W.L. and S.L. performed experiments and data analysis (under the supervision of K.W.). J.Z., H.L. and S.M. performed the DFT calculations. B.F., L.C. and K.W. wrote the manuscript, with contributions from all authors. All authors contributed to data analyses and discussions.

Corresponding authors

Correspondence to Hui Li or Lan Chen or Kehui Wu.

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The authors declare no competing financial interests.

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Feng, B., Zhang, J., Zhong, Q. et al. Experimental realization of two-dimensional boron sheets. Nature Chem 8, 563–568 (2016). https://doi.org/10.1038/nchem.2491

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