| AVS 65th International Symposium & Exhibition | |
| 2D Materials Focus Topic | Friday Sessions |
| Session 2D+EM+MN+NS-FrM |
| Session: | Nanostructures including Heterostructures and Patterning of 2D Materials |
| Presenter: | Leif Johansson, Linkoping University, Sweden |
| Authors: | T.B. Balasubramanian, Lund University, Sweden M. Leandersson, Lund University, Sweden J. Adell, Lund University, Sweden C. Polley, Lund University, Sweden L.I. Johansson, Linkoping University, Sweden R. Yakimova, Linkoping University, Sweden C. Jacobi, Linkoping University, Sweden |
| Correspondent: | Click to Email |
Graphene has made a major impact on physics due to its large variety of properties. The peculiar band structure of free standing graphene, showing linear dispersion and a Dirac point at the Fermi energy, makes it attractive for various applications. Large-scale epitaxial films have been grown on Si-terminated SiC substrates. However, the electronic structure is influenced when the graphene is laid upon a substrate whose lattice symmetry does not match that of graphene [1,2]. Six replicas oriented around each Dirac cone were observed already in the first ARPES experiments [1] of graphene grown on SiC(0001), and later reported [2] to have around 40 times lower intensity than a main Dirac cone. They were found to have the same relative separation and orientation as the rosette spots observed around the 0;th and 1x1 SiC and Graphene spots in the low energy electron diffraction (LEED) pattern and were explained [2] to have similar origin, i.e. to originate from photoelectron diffraction.
In two later ARPES investigations [3,4] additional weaker replicas were reported to exist along the Γ-K direction in the Brillouin zone of Graphene. One of them showed the existence [3] only for 1 ML but not 2 ML samples while the other reported [4] the existence in both 1 ML and 3 ML graphene samples. The origin of these replicas were in both cases attributed to a modulation of the ionic potential in the graphene layer/layers induced by the charge modulation of the carbon layer at the interface, i.e. the carbon buffer layer. Thus to an initial state effect instead of the earlier proposed final state effect. In both those experiments un-polarized HeI radiation was utilized, so the symmetry of the π-band replicas was not determined. We therefore investigated monolayer and multilayer graphene samples using linearly polarized synchrotron radiation, which allowed us to exploit the so called dark corridor [5] to directly determine the symmetry of the replica cones. Our ARPES data therefore clearly show the origin of these additional replicas observed using He-I radiation and moreover reveal the existence of some weaker replicas not earlier reported. An interpretation of our ARPES data in terms of final state photoelectron diffraction effects is shown to account for the location and symmetry of the π-band replicas observed.
References
1. A. Bostwick, et al, New J. Phys. 9, 385 (2007)
2. E. Rotenberg and A. Bostwick, Synthetic Metals 210, 85 (2015)
3. K. Nakatsuji, et al, Phys. Rev. B 82, 045428 (2010)
4. L. Huang, et al, Phys. Rev. B 96, 03541 (2017)
5. I. Gierz, et al, Phys. Rev. B 83, 121408 (2011)