| AVS 57th International Symposium & Exhibition | |
| Graphene Focus Topic | Tuesday Sessions |
| Session GR+TF-TuA |
| Session: | Graphene and 2D Nanostructures |
| Presenter: | J.A. Kelber, University of North Texas |
| Authors: | C. Bjelkevig, University of North Texas Z. Mi, University of North Texas J. Xiao, Nebraska Center for Nanostructures and Materials P.A. Dowben, Nebraska Center for Nanostructures and Materials S. Gaddam, University of North Texas S. Pokharel, University of North Texas J.A. Kelber, University of North Texas |
| Correspondent: | Click to Email |
Graphene has been grown by chemical vapor deposition of C2H4 on a monolayer of h-BN(0001) formed by atomic layer deposition (BCl3, NH3) on Ru(0001). AES, STM and LEED confirm a graphene-like overlayer, with near-zero DOS near the Fermi level, in registry with a BN R30(√3x√3) substrate. Raman spectra reveal graphene “G” and “2D” features with relative intensities indicative of single layer graphene. A large (350 cm-1) redshift in the 2D feature relative to HOPG indicates significant BN-to-graphene charge transfer. The charge transfer is confirmed by photoemission/angle-resolved inverse photoemission spectroscopies (PES/ARIPES), that demonstrate filling of the lowest unoccupied graphene state ( π*) near the Brillouin zone center. These results are in direct contrast to PES/ARIPES results for graphene/ Cu, and reported results for graphene/SiC(0001), that show empty graphene π* states. The data show that the BN layer acts as an n-type dopant for graphene. For the graphene/BN heterojunctions, the ARIPES-determined dispersion of the unoccupied graphene σ*(Γ1+) state yields an effective mass of 0.05 me , in excellent agreement with reported transport measurements on graphene sheets, and indicating that BN doping does not fundamentally alter the graphene electronic structure. The direct growth of graphene on dielectric substrates, and the controlled exploitation of graphene/substrate heterojunction properties, are critical issues for practical device fabrication. The implications of direct CVD of undoped graphene and graphene/BN heterojunctions on high dielectric constant substrates for device applications will be discussed in light of recent results in our laboratories for graphene thermal and free radical-assisted CVD on OH-terminated MgO(111).
Acknowledgements: Work at UNT was supported by the Global Research Consortium of the Semiconductor Research Corporation through Task ID 1770.001, and through ONR under award no. N00014-08-1-1107 through a subcontract with Texas State University at San Marcos. Work at UNL was supported by the Defense Threat Reduction Agency (Grant No. HDTRA1-07-1-0008), and the NSF "QSPINS" MRSEC (DRM-0820521) at UNL. The authors also thank Luigi Colombo and Adam Pirkle for acquisition of the Raman spectra.