| AVS 58th Annual International Symposium and Exhibition | |
| Surface Science Division | Friday Sessions |
| Session SS-FrM |
| Session: | Surface Science on Graphene |
| Presenter: | Rafik Addou, University of South Florida |
| Authors: | R.Q. Addou, University of South Florida A. Dahal, University of South Florida L. Adamska, University of South Florida I.I. Oleynik, University of South Florida M. Batzill, University of South Florida |
| Correspondent: | Click to Email |
Graphene growth on metal surfaces (Ni, Pt, Ir, Rh and Cu) has been studied extensively [1]. Ni(111) is special among these metals because it is closely lattice matched with graphene (agraphene= 0.246 nm vs. aNi(111)= 0.249 nm) allowing the growth of graphene with a single domain and in registry with the substrate [2]. However, compared to most other metal substrates the interaction between Ni and graphene is rather large, resulting in a small metal-carbon distance and a large shift of the graphene π-band compared to freestanding graphene. In order to de-couple graphene from the Ni-substrate other weaker interacting metals such as Cu and Au have been successfully intercalated between the graphene and Ni-substrate [3]. These metals have, however, a different lattice parameter and consequently the registry between the substrate and graphene is lost. Here we demonstrate a new approach that weakens the metal-graphene interaction without destroying the lattice registry. By intercalating Sn-atoms an ordered √3 × √3 R30° Sn-Ni alloy is formed at the interface. The Sn intercalation process is characterized by Auger electron spectroscopy (AES) and low energy electron diffraction (LEED). In this alloy Sn substitutes for surface Ni atoms without changing the lattice parameter of the substrate and consequently the registry between the metal substrate and graphene is maintained. DFT simulations indicate that Sn alloying with Ni weakens the interaction of graphene with the metal substrate and consequently increasing the graphene-substrate distance and restoring the graphene π-band close to the position of free-standing graphene. Atomic-resolution scanning tunneling microscopy (STM) imaging reveals that the alloy periodicity is reproduced in the graphene layer, i.e. a √3 × √3 R30° superstructure is imposed on the graphene by the alloy substrate. This indicates a variation of the local density of states for C-atoms located on top of Sn-substrate sites compared to Ni-sites. Further experimental and theoretical characterization of the influence of the substrate on the electronic and structural properties of graphene is ongoing.
[1] J. Wintterlin and M.-L. Bocquet, Surf. Sci. 603, 1841-1852 (2009)
[2] J. Lahiri et al., Nano Lett. 11, 518-522 (2010)
[3] A. Varykhalov et al., Phys. Rev. Lett., 101, 157601 (2008)