Evaluation local strain of twisted bilayer graphene via moiré pattern

• Suspended twisted bilayer graphene was prepared by using water assisted transfer approach. • A theoretical model for local strain analysis of twisted bilayer graphene was proposed. • Moiré pattern of twisted bilayer graphene was characterized by atomic force microscopy. • Local residual strain of twisted bilayer graphene was evaluated by deformation of moiré pattern. Twisted bilayer graphene with hexagonal moiré patterns have shown a variety of unusual physical and mechanical phenomena. Unfortunately, some residual strain is introduced during the fabrication process of twisted bilayer graphene, leading to the deformation of moiré pattern. In this work, we employed water assisted transfer approach to build the suspended twisted bilayer graphene over the microscale holes patterned SiO 2 /Si substrate. Atomic force microscopy is involved to characterize the moiré pattern. Based on reciprocal vectors analysis, a theoretical model was proposed to extract the local strain of twisted bilayer graphene sample. The local strain of twisted bilayer graphene induced by the transfer process as well as the biaxial tensile stretch was evaluated respectively.