Non-equilibrium Interface and Surface Dynamics

The role of carbon surface diffusion on the growth of epitaxial graphene on SiC

Taisuke Ohta

Sandia National Laboratories

Growth of high quality graphene films on silicon-carbide (SiC) is regarded as one of the more viable pathways toward graphene-based electronics. Graphene films are readily formed on SiC by preferential sublimation of Si at elevated temperature. Little is known, however, about the atomistic processes of interrelated Si sublimation and graphene growth. We have observed the formation of graphene on SiC by Si sublimation using low energy electron microscopy (LEEM), scanning tunneling microcopy, and atomic force microscopy. This work reveals unanticipated growth mechanisms, which depend strongly on the initial surface morphology. Isolated bilayer SiC steps generate narrow ribbons of graphene by a distinctive cooperative process, whereas triple bilayer SiC steps allow large graphene sheets to grow by step flow. In both cases, carbon diffusion governs the spatial relationship between Si sublimation and graphene growth. The characteristics of these growth fronts have important consequences to the resulting graphene films. We demonstrate how graphene quality can be improved by controlling the initial step structures to avoid the instabilities inherent in diffusion-limited growth.

This work is supported by the LDRD program at Sandia Labs and the US DOE Office of Basic Energy Sciences, Division of Materials Science and Engineering (DE-AC04-94AL85000), and was performed in part at CINT (DE-AC04-94AL85000). Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Co., for the U.S. DOE NNSA (DE-AC04-94AL85000).

Joint work with N. C. Bartelt, Shu Nie, T. E. Beechem, Konrad Thürmer, and G. L. Kellogg, Sandia National Laboratories, Albuquerque, NM 87185 and Livermore, CA 94550