| AVS 57th International Symposium & Exhibition | |
| Graphene Focus Topic | Thursday Sessions |
| Session GR+AS+TF-ThM |
| Session: | Graphene Synthesis on Metals |
| Presenter: | K.F. McCarty, Sandia National Labs |
| Authors: | S. Nie, Sandia National Labs A.L. Walter, Lawrence Berkeley National Lab and Fritz-Haber-Institut der Max-Planck-Gesellschaft, Germany E. Starodub, Sandia National Labs K.F. McCarty, Sandia National Labs K. Thürmer, Sandia National Labs K. Horn, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Germany A. Bostwick, Lawrence Berkeley National Lab N.C. Bartelt, Sandia National Labs E. Rotenberg, Lawrence Berkeley National Lab |
| Correspondent: | Click to Email |
An interesting question is how the second layer of graphene grows on transition-metal substrates. First-layer graphene on Ir(111) [1] exists with four discrete in-plane orientations relative to substrate directions [2]. Thus, this system offers potential to better understand the relationship between second-layer growth and first-layer structure. We use low-energy electron microscope (LEEM) to characterize where the second-layer graphene forms on Ir(111) covered by domains of differently oriented first-layer graphene. We find that the second layer does not grow easily where the lattice of the first-layer graphene is aligned with the lattice of the substrate. Instead the second-layer graphene forms most easily where the first-layer graphene is rotated, by 30°, for example. Angle-resolved photoemission spectroscopy (ARPES) confirms this strong preference. So how does the orientation of the first layer control the growth of the second layer? ARPES and Raman spectroscopy provide insight, revealing that the rotated variants of first-layer graphene are even less strongly bound to the substrate than the more abundant, non-rotated variant [3]. This information suggests the following growth mechanism. Carbon atoms segregating from the substrate build up in concentration under the first layer. The second layer nucleates and grows where it is easier to debond the first layer from the substrate, that is, under the rotated first-layer domains. Electron diffraction also reveals that the second graphene layers are usually but not always aligned with the first-formed layer. Finally, we will discuss the doping of the different types of second-layer graphene, as revealed by ARPES.
This work was supported by the Office of Basic Energy Sciences of the US DOE under Contracts No. DE-AC04-94AL85000 (SNL) and No. DE-AC02-05CH11231 (LBL).
[1] A. T. N'Diaye, J. Coraux, T. N. Plasa, C. Busse, and T. Michely, New J. Phys. 10, 16 (2008).
[2] E. Loginova, S. Nie, K. Thürmer, K., N. C. Bartelt, and K. F. McCarty, Phys. Rev. B 80, 085430 (2009).
[3] I. Pletikosic, M. Kralj, P. Pervan, R. Brako, J. Coraux, A. T. N'Diaye, C. Busse, and T. Michely, Phys. Rev. Lett. 102, 056808 (2009).