A B2N monolayer: a direct band gap semiconductor with high and highly anisotropic carrier mobility

SY Lin and Y Guo and ML Xu and JJ Zhao and YW Liang and XH Yuan and YM Zhang and FL Wang and J Hao and YW Li, NANOSCALE, 14, 930-938 (2022).

DOI: 10.1039/d1nr07054a

Two-dimensional materials with a planar lattice, suitable direct band gap, and high and highly anisotropic carrier mobility are desirable for the development of advanced field-effect transistors. Here we predict three thermodynamically stable B-rich 2D B-N compounds with the stoichiometries of B2N, B3N, and B4N using a combination of crystal structure searches and first-principles calculations. Among them, B2N has an ultraflat surface and consists of eight-membered B6N2 and pentagonal B3N2 rings. The eight-membered B6N2 rings are linked to each other through both edge-sharing (in the y direction) and bridging B3N2 pentagons (in the x direction). B2N is a semiconductor with a direct band gap of 1.96 eV, and the nature of the direct band gap is well preserved in bilayer B2N. The hole mobility of B2N is as high as 0.6 x 10(3) cm(2) V-1 s(-1) along the y direction, 7.5 times that in the x direction. These combined novel properties render the B2N monolayer as a natural example in the field of two-dimensional functional materials with broad application potential for use in field-effect transistors.

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