Twisted 2D Heterostructure Moiré Superlattice Characterization with Piezoresponse Force Microscopy and Freesource SPM Software

Heterostructures composed of two-dimensional van der Waals (vdW) materials can result in moiré superlattices as a result of the misalignment of the crystal structures of the different layers. Here I describe a method whereby the moiré superlattice can be characterized at room temperature using piezoresponse force microscopy (PFM). The simultaneous mapping of multiple moiré responses in a twisted bilayer graphene on hexagonal boron nitride heterostructure was obtained using scanning probe microscopy (SPM) imaging and analysis freeware. The method consisted of a series of noise-filtering processes to allow for the smaller underlying moiré to appear through the contrasting domain response. Upon comparison with scanning tunneling microscopy data and reports from literature, the small-period moiré superlattice corresponds to the twist between the two graphene layers, while the larger period superlattice may be a result of the bilayer graphene/hBN misalignment. Using this technique, additional information about the sample was obtained at an ambient temperature which was not previously seen.