| AVS 58th Annual International Symposium and Exhibition | |
| Graphene and Related Materials Focus Topic | Monday Sessions |
| Session GR-MoM |
| Session: | Graphene Growth |
| Presenter: | Joseph Wofford, University of California at Berkeley and Lawrence Berkeley National Laboratory |
| Authors: | J. Wofford, University of California at Berkeley and Lawrence Berkeley National Laboratory E. Starodub, Sandia National Laboratories N.C. Bartelt, Sandia National Laboratories K. McCarty, Sandia National Laboratories O. Dubon, University of California at Berkeley and Lawrence Berkeley National Laboratory |
| Correspondent: | Click to Email |
Studies on the growth of graphene on metal surfaces indicate that the strength of the interaction between the two materials plays a significant role in determining the evolution and final properties of the resulting film. A number of relatively strongly interacting graphene-metal systems, such as –Ru and –Ir, have been studied comprehensively, but the graphene-Cu system remains the only comparatively weakly interacting combination to have been so scrutinized [1]. Comparisons between graphene growth on Cu and Au provide an opportunity to systematically understand graphene growth on weakly interacting substrates. For example, both Cu and Au have low C solubility, but the mismatch between the lattice of graphene aligned with that of the metal’s (111) surface is substantially larger for Au than for Cu. To examine what effect these differences have, we used low-energy electron microscopy (LEEM) to observe graphene growth on Au (111) in UHV by direct deposition of C from a heated graphite rod. Low-energy electron diffraction (LEED) analysis of the pre-growth Au (111) surface showed the characteristic “herringbone” reconstruction peculiar to Au. Graphene islands nucleate rapidly upon exposure to the C flux, suggesting a relatively low equilibrium C adatom concentration on the otherwise bare Au surface. The graphene islands nucleate simultaneously across the surface with a slight preference for nucleation along Au step edges rather than on terraces. The nucleation density is substantially higher than previously observed on other metals, causing inter-island impingement to begin at sub-micron sizes. Similar to Cu, no island growth due to C precipitation from the bulk of the Au occurs during sample cooling. We find that the graphene lattice prefers strongly to be aligned with the Au lattice with a small minority of the domains rotated by 30 degrees. The prevalence of the aligned graphene orientation is particularly surprising due to the substantial lattice mismatch involved and calculations predicting a 30 degree relative rotation is preferred [2,3]. We draw comparisons between the observed rotational structure and those predicted by first principle calculations.
Work at Sandia was supported by the Office of Basic Energy Sciences, Division of Materials Sciences and Engineering, U. S. Department of Energy under Contract No. DE-AC04-94AL85000. J.M.W. acknowledges support from the National Science Foundation Graduate Research Fellowship Program.
[1] J. M. Wofford, et al., Nano Lett. 10, 4890 (2010).
[2] M. Vanin, et al., Phys. Rev. B 81, 081408 (2010).
[3] C. Gong, et al., J. Appl. Phys. 108, 123711 (2010).