Electron beam-induced nanopores in Bernal-stacked hexagonal boron nitride

Controlling the size and shape of nanopores in two-dimensional materials is a key challenge in applications such as DNA sequencing, sieving, and quantum emission in artificial atoms. We here experimentally and theoretically investigate triangular vacancies in (unconventional) Bernal-stacked AB-h-BN formed using a high-energy electron beam. Due to the geometric configuration of AB-h-BN, triangular pores in different layers are aligned, and their sizes are controlled by the duration of the electron irradiation. Interlayer covalent bonding at the vacancy edge is not favored, as opposed to what occurs in the more common AA′-stacked BN. A variety of monolayer, concentric, and bilayer pores in the bilayer AB-h-BN are observed in high-resolution transmission electron microscopy and characterized using ab initio simulations. Bilayer pores in AB-h-BN are commonly formed and grow without breaking the bilayer character. Nanopores in AB-h-BN exhibit a wide range of electronic properties, ranging from half-metallic to non-magnetic and magnetic semiconductors. Therefore, because of the controllability of the pore size, the electronic structure is also highly controllable in these systems and can potentially be tuned for particular applications.

This work was supported primarily by the Director, Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division, of the U.S. Department of Energy under Contract No. DE-AC02–05-CH11231, within the sp2-bonded Materials Program (No. KC2207), which supported TEM imaging and first-principles computations of the atomic structures. Sample growth was supported by the Director, Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division, of the U.S. Department of Energy under Contract No. DE-AC02–05-CH11231, within the van der Waals Heterostructures Program (No. KCWF16). Further support for the theoretical work was provided by the NSF Grant No. DMR-1926004, which supported first-principles computations of the precise electronic structures. Computational resources were provided by the DOE at the Lawrence Berkeley National Laboratory's NERSC facility and the NSF through XSEDE resources at NICS. S.M.G. acknowledges support from the Kavli Energy NanoSciences Institute Fellowship and the NSF Graduate Fellowship Program. M.D. thanks Sehoon Oh and P.E. thanks Earl J. Kirkland for their helpful scientific discussions.