Partial-epitaxial morphology of graphene nanoribbon on the Si-terminated SiC(0001) surfaces

We present a study of morphology of graphene nanoribbons with armchair edges placed on the SiC(0001) substrates. We found that on the Si-terminated SiC(0001) surface the initial planar shape of a graphene nanoribbon can be substantially distorted by the underlying substrate. Appreciable ripples are created in the graphene nanoribbon due to the combined effect of the van der Waals interaction and covalent bond formation between the graphene nanoribbon and the substrate. A graphene nanoribbon with a narrow width forms covalent bonds only along the edges, creating a partial wavy cylindrical shape of the nanoribbon. With an increase in the nanoribbon width, covalent bonds are formed not only along the edges but also in the interior, resulting in a reduction in the distortion and a decrease in the amplitude of the ripples. It is also found that the number of covalent bonds between the graphene nanoribbon and the substrate grows initially and then saturates as the temperature increases. On the C-terminated SiC(0001) substrates, the planar shape of the graphene nanoribbon is retained due to the absence of covalent bond formation at the interface. ©2010 The American Physical Society