| AVS 56th International Symposium & Exhibition | |
| Graphene Topical Conference | Monday Sessions |
| Session GR+SS-MoA |
| Session: | Epitaxial Graphene on SiC |
| Presenter: | G.G. Jernigan, US Naval Research Laboratory |
| Authors: | G.G. Jernigan, US Naval Research Laboratory J.L. Tedesco, US Naval Research Laboratory J.G. Tischler, US Naval Research Laboratory E. Glaser, US Naval Research Laboratory J. Caldwell, US Naval Research Laboratory P.M. Campbell, US Naval Research Laboratory D.K. Gaskill, US Naval Research Laboratory J.A. Robinson, Electro-Optics Center Penn State M.A. Fanton, Electro-Optics Center Penn State |
| Correspondent: | Click to Email |
Development of graphene is a materials issue. Exfoliated graphene has shown the promise of high carrier mobilities, but for graphene to become technologically viable, epitaxial graphene formed over large areas must be developed. Reported carrier mobilities for epitaxial graphene grown on SiC range from > 250,000 to < 1,000 cm2V-1s-1. Mobility results can vary with measurement method, measurement temperature, and sample size. We will present our results, which encompass the aforementioned range of mobilities, for graphene formed on Si-face and C-face SiC.
Utilizing semi-insulating substrates, we have been able to correlate electrical characteristics with materials properties, which are dependent on the surface termination of SiC. Si-face graphene consistently shows lower mobilities than graphene grown on the C-face. XPS shows the differences between growth on the Si-face and the C-face are 1) the presence of an interfacial layer between the graphene and the SiC for Si-face films and 2) electronic differences between the C 1s peak for graphene on the C-face and the C 1s peak for graphene on the Si-face. The electronic differences may result from more graphene layers form on the C-face than on the Si-face. In particular, graphene forms only 1 to 3 layers on the Si-face even for long growth times at high temperature (e.g. 60 min at 1600 °C). STM images of graphene on the Si-face show an islanding mode of growth, which leads to the development of grain boundaries within the film, and µ-Raman measurements show that the mobility increases as the domain size increases. Graphene formed on the C-face of SiC grows very rapidly, leading to films which are 10 to 30 nm thick and decorated with striped surface features (referred to as “giraffe stripes”). Independent of the presence of giraffe stripes, we observe that surface roughness does affect mobility, with smoother surfaces having higher mobilities. We have also performed far infrared magneto-transmission measurements (FIR-MT) on the graphene films. The C-face graphene shows a 0(-1) → 1(0) Landau level transition with a √B dependence and linewidths consistent with layers having carriers described as Dirac fermions with mobilities > 250,000 cm2V-1s-1 at 4.2K. The Si-face graphene showed much broader linewidths resulting from lower carrier mobility. One trend that holds for graphene on both faces of SiC is that fabrication of small area devices can result in higher carrier mobilities and that carrier mobility increases as the carrier density decreases. Continued improvements in the electrical characteristics of epitaxial graphene can be realized through improvements in material quality.