Nanoarchitectonics-Based Growth of High-Quality Monolayer Graphene and Interlayer Interactions in a Twisted Bilayer to Five-Layer Structures Investigated by Tip-Enhanced Raman Spectroscopy and Kelvin Force Probe Microscopy

Large single-crystal graphene is an important material that holds great promise for applications in graphene electronics, whereas twisted bilayer graphene exhibits breakthrough structural properties and revolutionizes diverse future devices. Herein, we synthesized millimeter scale high-quality graphene stacked in a few layers on copper (Cu) foil by atmospheric pressure chemical vapor deposition (APCVD). The maximum size of hexagonal graphene was found to be around 5.5 mm. Raman spectroscopy and mapping analysis specified the quality and clear structural changes in the graphene lattice consisting of monolayer to twisted few-layers. Especially, using nongap mode tip-enhanced Raman spectroscopy (TERS), a significant enhancement of the Raman signal was observed on the twisted graphene. Using Kelvin force probe microscopy (KPFM), we confirmed that the surface potential shifts more negatively with an increase in the number of layers. This is due to the lattice misalignment in the twisted structure, changing the charge distribution and Fermi level. The present findings of the physical properties of large-scale and twisted few-layer graphene are expected to contribute to the development of twistronics devices.