LAUSR

Abstract Twisted bilayer graphene is of particular interest with unique experimental characteristics such as fractional quantum hall states, topological phase transition, and superconductivity being reported. In these characteristics, interlayer spacing and coupling play a crucial role, which are inevitably affected by resist residues and other contaminations. In this research work, we demonstrate an effective way to modulate the interlayer conductance by in-situ annealing in the twisted bilayer Chemical Vapor Deposition (CVD) graphene. First, we removed adsorped p-type dopants in the as fabricated device by in-situ vacuum annealing, which led to slight n-doping due to charge transfer from SiO2 to graphene. The interaction between graphene and SiO2 is reduced by terminating the silicon dangling bonds through in-situ hydrogen annealing. Furthermore, in-situ annealing efficiently removed the residues in the graphene-to-graphene interface, and increased the interlayer conduction by an order of magnitude at 300 K. This is attributed to effective reduction in the interlayer spacing, and hence enhanced interlayer coupling. The four probe method interlayer measurement showed quantum tunneling conduction at temperature lower than 50 K, and electron-phonon scattering dominated conduction above 50 K. Again, we systematically decreased the interlayer conduction by electric field induced hydrogen molecule dissociative adsorption at CVD graphene vacancies.