Contribution of the buffer layer to the Raman spectrum of epitaxial graphene on SiC(0001)

Abstract

We report a Raman study of the so-called buffer layer with $(6\sqrt 3\times 6\sqrt 3)R30^{\circ }$ periodicity which forms the intrinsic interface structure between epitaxial graphene and SiC(0001). We show that this interface structure leads to a non-vanishing signal in the Raman spectrum at frequencies in the range of the D- and G-band of graphene and discuss its shape and intensity. Ab initio phonon calculations reveal that these features can be attributed to the vibrational density of states of the buffer layer.