Imaging double moiré pattern in twisted bilayer graphene grown on hBN with microwave impedance microscopy

Stacking multiple atomic layers of similar crystal structure will create moiré patterns whose periodicity and orientation are determined by the stacked layers. In this study, we image the moiré patterns in CVD grown bilayer graphene/hBN heterostructures using microwave impedance microscopy and conductive atomic force microscopy. Two sets of moiré patterns are observed: one formed between the first graphene layer with hBN and a second one between the two twisted graphene layers. The graphene/hBN moiré pattern indicates a perfect alignment between the two layers. The graphene/graphene moiré pattern has a smaller period due to a larger twist angle. This moiré pattern experiences abrupt phase change across the boundaries of the graphene/hBN moiré pattern. We present our analysis of such double moiré pattern based on lattice reconstruction occurred in the graphene layers.