Realization of an Ideal Cairo Tessellation in Nickel Diazenide NiN<sub>2</sub>: High-Pressure Route to Pentagonal 2D Materials.
basic_science · Level V
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- Record sourced from PubMed, PMID 34355559.
- Also identified by DOI 10.1021/acsnano.1c04325.
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Abstract
Most of the studied two-dimensional (2D) materials are based on highly symmetric hexagonal structural motifs. In contrast, lower-symmetry structures may have exciting anisotropic properties leading to various applications in nanoelectronics. In this work we report the synthesis of nickel diazenide NiN<sub>2</sub> which possesses atomic-thick layers comprised of Ni<sub>2</sub>N<sub>3</sub> pentagons forming Cairo-type tessellation. The layers of NiN<sub>2</sub> are weakly bonded with the calculated exfoliation energy of 0.72 J/m<sup>2</sup>, which is just slightly larger than that of graphene. The compound crystallizes in the space group of the ideal Cairo tiling (<i>P</i>4/<i>mbm</i>) and possesses significant anisotropy of elastic properties. The single-layer NiN<sub>2</sub> is a direct-band-gap semiconductor, while the bulk material is metallic. This indicates the promise of NiN<sub>2</sub> to be a precursor of a pentagonal 2D material with a tunable direct band gap.