NANO LETTERS
Raman Topography and Strain Uniformity of Large-Area Epitaxial Graphene
2009 Vol. 9, No. 3 964-968
Joshua A. Robinson,*,†,‡ Conor P. Puls,§ Neal E. Staley,§ Joseph P. Stitt,‡ Mark A. Fanton,† Konstantin V. Emtsev,| Thomas Seyller,| and Ying Liu‡,§ Electro-Optics Center, Materials Research Institute, and Department of Physics, The PennsylVania State UniVersity, UniVersity Park, PennsylVania 16802, and Lehrstuhl fu¨r Technische Physik, UniVersita¨t Erlangen-Nu¨rnberg, Erwin-Rommel-Strasse 1, 91058 Erlangen, Germany Received September 19, 2008; Revised Manuscript Received January 5, 2009
ABSTRACT We report results of Raman spectroscopy studies of large-area epitaxial graphene grown on SiC. Our work reveals unexpectedly large variation in Raman shift resulting from graphene strain inhomogeneity, which is shown to be correlated with physical topography by coupling Raman spectroscopy with atomic force microscopy. We show that graphene strain can vary over a distance shorter than 300 nm and may be uniform only over roughly 1 µm. We show that nearly strain-free graphene is possible even in epitaxial graphene.
Graphene exhibits extraordinary electronic properties including an unusually high mobility of the charge carriers.1 Significant progress toward understanding the properties of graphene has resulted from studying graphene flakes mechanically exfoliated from bulk graphite.1,2 While these small flakes (
