  Two-dimensional (2D) hexagonal boron nitride (BN) nanosheets are excellent
dielectric substrate for graphene, molybdenum disulfide and many other 2D
nanomaterials based electronic and photonic devices. To optimize the
performance of these 2D devices, it is essential to understand the dielectric
screening properties of BN nanosheets as a function of the thickness. Here,
electric force microscopy along with theoretical calculations based on both
state-of-the-art first-principles calculations with van der Waals interactions
under consideration and non-linear Thomas-Fermi theory models are used to
investigate the dielectric screening in high-quality BN nanosheets of different
thicknesses. It is found that atomically thin BN nanosheets are less effective
in electric field screening, but the screening capability of BN shows a
relatively weak dependence on the layer thickness.
