Fabrication of large-area twisted bilayer graphene for high-speed ultra-sensitive tunable photodetectors

Single layer graphene has shown promising applications in fast and sensitive optoelectronic applications such as optical modulators and photodetectors. Twisted bilayer graphene has the potential to further improve the performances of such graphene devices due to its modified electronic band structure. However, the lack of synthesis method for large-area isolated twisted bilayer graphene has limited device applications. After a brief review of recent development in single layer graphene optoelectronic property and photodetectors, we discuss unique optical properties of twisted bilayer graphene. We then show two methods that we have developed to fabricate large-size twisted bilayer graphene islands. The first method uses chemical vapor deposition; the other method utilizes mechanical stacking of two large-size single layer graphene hexagons. The realization of such twisted bilayer graphene samples enables new development of novel graphene-based devices.