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

TL;DR

This study investigates how the buffer layer between epitaxial graphene and SiC(0001) influences the Raman spectrum, revealing that it contributes specific vibrational features that can be characterized through experimental and computational methods.

Contribution

The paper demonstrates that the buffer layer causes distinct Raman signals in epitaxial graphene, supported by ab-initio calculations linking these signals to its vibrational density of states.

Findings

Buffer layer contributes to Raman D- and G-band signals.

Vibrational density of states explains Raman features.

Ab-initio calculations confirm experimental observations.

Abstract

We report a Raman study of the so-called buffer layer with $(6\sqrt3\times6\sqrt3)R30^{\circ}$ periodicity which forms the intrinsic interface structure between epitaxial graphene and SiC(0001). We show that this interface structure leads to a nonvanishing 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.