| AVS 55th International Symposium & Exhibition | |
| Graphene Topical Conference | Tuesday Sessions |
| Session GR+EM+NC-TuM |
| Session: | Graphene and Carbon Electronics |
| Presenter: | K.R. Knox, Columbia University |
| Authors: | K.R. Knox, Columbia University S. Wang, Columbia University A. Morgante, Laboratorio TASC-INFM, Italy D. Cvetko, Laboratorio TASC-INFM, Italy A. Locatelli, Elettra - Sincrotrone Trieste S.C.p.A., Italy T.O. Mentes, Elettra - Sincrotrone Trieste S.C.p.A., Italy M.A. Niño, Elettra - Sincrotrone Trieste S.C.p.A., Italy P. Kim, Columbia University R.M. Osgood, Columbia University |
| Correspondent: | Click to Email |
While graphene's distinctive Dirac-cone electronic structure and simple 2D atomic structure have attracted major interest in the physics community, inherent limitations in the size of available exfoliated graphene samples have made it difficult to study this system with conventional UHV probes such as photoemission and low energy electron diffraction (LEED). Thus, previous photoemission and LEED studies of graphene have probed films grown on SiC.1,2,3 While graphene grown on SiC can form large area sheets, exfoliated graphene on SiO2 continues to be the system of choice for transport experiments as it is relatively easy to gate and has shown the most interesting and impressive electrical properties.4,5 Using the high spatial resolution of the Nanospectroscopy beamline at the Elettra synchrotron light source, we have overcome these size limitations by utilizing micro-spot low energy electron diffraction (μLEED) and micro-spot angle resolved photoemission (μARPES) to study exfoliated graphene. In this talk, we will discuss our measurements of the electronic structure and surface morphology of exfoliated graphene using low energy electron microscopy (LEEM), μLEED and μARPES. Our LEEM data can be used to unambiguously determine the film thickness of graphene sheets by means of a quantum size contrast effect; a well understood effect in which modulations in the electron reflectivity arise due to quantum well resonances above the vacuum level.6 Our diffraction measurements provide information about the surface morphology of monolayer and multilayer graphene sheets, which are not atomically flat, but microscopically corrugated. This corrugation increases with decreasing film thickness, reaching a maximum for monolayer graphene. Our photoemission measurements probe the unique massless fermionic dispersion of monolayer graphene, to confirm that the electronic structure of the valence band is well described by the one-orbital tight binding model.
1 T. Ohta et al., Science 313, 951 (2006).
2 A. Bostwick et al., Nature Phys. 3, 36 (2007).
3 S.Y. Zhou et al., Nature Phys. 2, 595 (2006).
4 K.S. Novoselov et al., Science 306, 666 (2004).
5 Y.B. Zhang et al., Nature 438, 201 (2005).
6 M.S. Altman, et al. App. Surf. Sci. 169, 82 (2001).