Dielectric function of epitaxial quasi-freestanding monolayer graphene on Si-face 6H-SiC in a broad spectral range

We present a study of the optical properties of quasi-freestanding epitaxial monolayer graphene grown on the Si face of 6H-SiC (0001) in a broad spectral range from midinfrared to ultraviolet. After growth, the sample was intercalated by hydrogen in order to ensure that no dangling bonds between the substrate and graphene layer remain. Spectral dependence of the dielectric function of graphene was parametrized based on spectroscopic ellipsometry fits. We show that, from the viewpoint of optical properties, the investigated sample is very close to exfoliated graphene. We provide information about the spectral dependence of the complex dielectric function of quasi-freestanding graphene in a broad spectral range.