Stacking-engineered ferroelectricity in bilayer boron nitride

2D ferroelectrics with robust polarization in the ultrathin limit, provide novel building blocks for functional van der Waals heterostructures. Experimental reports, however, are limited due to the strict requirement of a layered polar bulk crystal [1]. Here, we demonstrate a general approach to engineering 2D ferroelectrics from a non-ferroelectric parent compound using van der Waals assembly [2]. Parallel-stacked bilayer boron nitride is shown to possess out-of-plane electric polarization that reverses depending on the stacking order, AB or BA. The polarization switching is probed via the induced carrier to an adjacent graphene sheet. Furthermore, small-angle twisted bilayer boron nitride creates moiré ferroelectricity with staggered polarization, which changes ferroelectric switching dynamics. The ferroelectricity persists to room temperature while keeping the high mobility of graphene, paving the way for potential ultrathin nonvolatile memory applications [3].
[1] C. Cui et al., npj 2D Mater. Appl. 2, 18 (2018)
[2] L. Li et al., ACS Nano. 11, 6382 (2017)
[3] K. Yasuda et al., arXiv:2010.06600