Nanoscale evaluation of the number of layers of hexagonal boron nitride by scattering-type scanning near-field optical microscopy

Abstract

We demonstrate a nondestructive way to determine the number of layers of hexagonal boron nitride (h-BN) by scattering-type scanning near-field optical microscopy (s-SNOM). The amplitude of s-SNOM near-field signals show a dependence on the number of h-BN layers, which can be explained by a finite dipole model. The layer number estimated by the s-SNOM is consistent with that observed by a transmission electron microscopy. This method also allows us to estimate the domain size of h-BN from the distribution of s-SNOM signals. These results demonstrate that the layer number and its in-plane distribution can be evaluated by s-SNOM with nanoscale spatial resolution.