Abstract
In this talk, I would like to discuss the optical properties of multilayer epitaxial graphene at low and high energies (1.5 – 35 eV). Multilayer epitaxial graphene grown by thermal decomposition on the carbon face (MEG-C) of a SiC substrates exhibit the electronic and optical properties of freestanding graphene, in which the interaction between graphene and underlying substrate is absent. This is due to the existence of different orientations between adjacent graphene layers which decouples those graphene layers. On the one hand, the low energy optical properties of MEG-C resemble to thatof chemical vapour deposition (CVD) graphene on SiO2 substrate where one can observe universal optical conductivity below 2 eV and asymmetric absorption peak at 4.5 eV due to the process of interband transition and the interaction between the electrons and electron-hole at M-points in the Brillouin zone of graphene [1-4]. On the other hand, the high energy optical properties of MEG-C has not been studied in details. According to the theory based on density functional calculation (DFT) with local density approximation (LDA) in which GW many-body effect and electron-hole interaction were included, the absorption peak of freestanding graphene and bilayer graphene should occurat 11 eV and 14.5 eV due to the uniqueness of parallel band between σ and π* band [5]. I will report our recent optical data of MEG-C taken at very broad energy range and will discuss the optical constant related to the dynamics of the electrons of freestanding graphene at high energy