Observation and manipulation of grain boundary corrugations in polycrystalline graphene supported by van der Waals and metallic substrates

The nanoscale corrugations, which endow atomically thin two-dimensional materials with unique physical and chemical properties, universally exist in the grain boundary (GB) of polycrystalline graphene, but their structural tunability and the influence of substrate interaction require further investigation. Here, we report the atomically resolved scanning tunneling microscope (STM) observation and manipulation of GB corrugations in polycrystalline graphene with different substrate interactions. On the van der Waals (vdW) substrate graphite, the structure of the GB corrugation is dominated by intralayer interaction arising from the misorientation between neighboring grains. It evolves from periodic bubble-like corrugations to continuous wrinkles as the misorientation angle increases. The buckling polarity of the surface and subsurface bubble-like GB corrugations on vdW substrates can be reversibly manipulated by applying an electric field through the STM tip. While on the metallic substrate Pt(111), the GB wrinkles show asymmetric cross-sectional profiles due to combined intralayer interactions from neighboring grains and interlayer interactions from the substrate. The metallic substrate also provides the pinning effect prohibiting the buckling polarity manipulation. Additionally, an asymmetric strain distribution mechanism was proposed to explain the influence of the key factors. These findings shed light on the strain engineering of graphene corrugations, which might find applications in electronic devices.