Temperature dependent structural changes of graphene layers on 6H-SiC(0001) surfaces

We investigated the electronic and structural properties of graphene layers grown on a 6H-SiC (Si-terminated) substrate by using core level photoemission spectroscopy (CLPES), low energy electron diffraction (LEED), and near edge x-ray absorption fine structure (NEXAFS). The angle between the plane of the graphene sheet and the SiC substrate was measured by monitoring the variation of the pi* transition in the NEXAFS spectrum with the thickness of the graphene layers. As the thickness of the graphene layers increased, the angle gradually decreased.