Paper GR+TF-TuA9
Graphene Growth on Metal Surfaces
Tuesday, November 10, 2009, 4:40 pm, Room C3
Previous work has shown that when elemental carbon is deposited on the Ru(0001) surface, graphene forms from a dense, tightly-bound carbon-adatom gas. Nonlinearity of the graphene growth rate with carbon adatom density suggests that growth proceeds by addition of carbon atom clusters to the graphene edge [1,2]. In this talk, we present the results of low-energy electron microscopy (LEEM) observations of graphene formation when Ru(0001) and Ir(111) surfaces are exposed to ethylene. We find that graphene growth velocities and nucleation rates on Ru have precisely the same dependence on adatom concentration as in elemental carbon deposition [3]. Thus, hydrocarbon decomposition only affects graphene growth through the rate of adatom formation; for ethylene, that rate decreases with increasing adatom concentration and graphene coverage. Graphene growth on Ir(111) is similar to that on Ru: the growth velocity is the same nonlinear function of adatom concentration (albeit with much smaller equilibrium adatom concentrations, as we explain with DFT calculations of adatom formation energies). When graphene is exposed to oxygen at high temperatures, it is etched. We observe the etching to proceed by the inverse of the graphene growth mechanism, i.e., by cluster detachment.
[1] E. Loginova, N. C. Bartelt, P. J. Feibelman, and K. F. McCarty, Evidence for graphene growth by C cluster attachment, New Journal of Physics 10 (2008) 093026
[2] K. F. McCarty, P. J. Feibelman, E. Loginova, and N. C. Bartelt, Kinetics and thermodynamics of carbon segregation and graphene growth on Ru(0001), Carbon doi:10.1016/j.carbon.2009.03.004
[3] E. Loginova, N. C. Bartelt, P. J. Feibelman, and K. F. McCarty, Factors influencing graphene growth on metal surfaces, submitted to New Journal of Physics (2009).