Near-field study in hBN moir\'{e} superlattices.

Interlayer coupling in atomic van der Waal (vdW) heterostructures plays a rather unique role in controlling their optical and electronic properties. The character of the interlayer coupling can be manipulated by a particular stacking arrangement of the proximal layers and by adjusting the orientation of the neighboring planes. The latter method is known to trigger the long-range periodic modulations referred to as moir\'{e} superlattices. Implications of moir\'{e} patterns for the properties of twisted graphene bilayers and in graphene on hexagonal boron nitride (hBN) are being systematically explored. Moir\'{e} patterns in other vdW systems are yet to be revealed. Here we report the observation of moir\'{e} superlattices with a giant periodicity (\textasciitilde 500 nm) in exfoliated hBN crystals subjected to thermal treatment. A combination of atomic force topographic imaging and scanning nano-infrared spectroscopy has implicated both strain and layer rotations in the observed effects.