  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 investigate experimentally and
theoretically 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 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 semiconducting. 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.
