Experimental and theoretical investigation of graphene layers on SiC(0001¯) in different stacking arrangements

Abstract

High-resolution transmission electron microscopy was used to investigate graphene layers formed on the C-terminated 4H-SiC(0001¯) surface in different arrangements, including various stacking sequences and spatial layer separation. Various stacking types such as ABAB and ABCA configurations were identified. The density functional theory (DFT) calculations of the graphene in various configurations were performed showing the following dispersion relations: AAAA—linear, ABBBA—close to linear, and ABAB—hyperbolic (strongly nonlinear). An increase of the interlayer separation of ABAB and ABCA systems leads to gradually increased linear dispersion, typical for AAAA stacking. It is shown, however, that for this transition to occur, a separation of the adjacent layers by about 5 Å is necessary, which is not likely to occur in the graphene layer grown on the SiC(0001¯) surface. DFT calculations employing rotation of the adjacent AB planes of bilayer graphene by either 27.7 or 32.2 arc deg demonstrate similar linear dependence, typical for single layer or double AA stacked graphene. It was therefore confirmed that the experimentally observed linear dispersion and the B dependence of the Landau levels may be explained by various stacking of carbon layers in multilayer graphene.