title: Observation of the intrinsic bandgap behaviour in as-grown epitaxial twisted graphene.
abstract: Twisted graphene is of particular interest due to several intriguing characteristics, such as its the Fermi velocity, van Hove singularities and electronic localization. Theoretical studies recently suggested the possible bandgap opening and tuning. Here, we report a novel approach to producing epitaxial twisted graphene on SiC (0001) and the observation of its intrinsic bandgap behaviour. The direct deposition of C60 on pre-grown graphene layers results in few-layer twisted graphene confirmed by angular resolved photoemission spectroscopy and Raman analysis. The strong enhanced G band in Raman and sp(3) bonding characteristic in X-ray photoemission spectroscopy suggests the existence of interlayer interaction between adjacent graphene layers. The interlayer spacing between graphene layers measured by transmission electron microscopy is 0.352 ± 0.012 nm. Thermal activation behaviour and nonlinear current-voltage characteristics conclude that an intrinsic bandgap is opened in twisted graphene. Low sheet resistance (~ 160 Ω □(-1) at 10 K) and high mobility (~2,000 cm(2) V(-1) s(-1) at 10 K) are observed.
authors.affiliation: Air Force Research Laboratory, Materials and Manufacturing Directorate (AFRL/RXAN) Wright-Patterson AFB, Wright Patterson AFB, Ohio 45433-7707, USA.
authors.forename: Jeongho
authors.initials: J
authors.lastname: Park
authors.affiliation: Air Force Research Laboratory, Materials and Manufacturing Directorate (AFRL/RXAN) Wright-Patterson AFB, Wright Patterson AFB, Ohio 45433-7707, USA.
authors.forename: William C
authors.initials: WC
authors.lastname: Mitchel
authors.affiliation: Department of Physics, University of Dayton, Dayton, Ohio 45469, USA.
authors.forename: Said
authors.initials: S
authors.lastname: Elhamri
authors.affiliation: Air Force Research Laboratory, Materials and Manufacturing Directorate (AFRL/RXAN) Wright-Patterson AFB, Wright Patterson AFB, Ohio 45433-7707, USA.
authors.forename: Lawrence
authors.initials: L
authors.lastname: Grazulis
authors.affiliation: Air Force Research Laboratory, Materials and Manufacturing Directorate (AFRL/RXAN) Wright-Patterson AFB, Wright Patterson AFB, Ohio 45433-7707, USA.
authors.forename: John
authors.initials: J
authors.lastname: Hoelscher
authors.affiliation: Air Force Research Laboratory, Materials and Manufacturing Directorate (AFRL/RXAN) Wright-Patterson AFB, Wright Patterson AFB, Ohio 45433-7707, USA.
authors.forename: Krishnamurthy
authors.initials: K
authors.lastname: Mahalingam
authors.affiliation: Department of Physics, Pusan National University, Busan 609-735, Republic of Korea.
authors.forename: Choongyu
authors.initials: C
authors.lastname: Hwang
authors.affiliation: Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.forename: Sung-Kwan
authors.initials: SK
authors.lastname: Mo
authors.affiliation: Air Force Research Laboratory, Materials and Manufacturing Directorate (AFRL/RXAN) Wright-Patterson AFB, Wright Patterson AFB, Ohio 45433-7707, USA.
authors.forename: Jonghoon
authors.initials: J
authors.lastname: Lee