Vibrational Characteristics of Two-Dimensional Composite Structures of Hexagonal Boron Nitride and Graphene

We use an eigenmode analysis to investigate normal mode vibrations of hexagonal boron nitride (h-BN) and of various types of graphene and h-BN composites. The vibrational spectrum of pristine h-BN structure was a rescaled one of pristine graphene. The vibrational spectra of graphene and h-BN composites with zigzag and with armchair boundaries were just mixtures of the vibrational spectra of the pristine structures of graphene and h-BN, respectively. The vibrational spectrum of h-BN doped with a graphene quantum dot was similar to that of h-BN, and the vibrational spectrum of graphene doped with a small piece of boron nitride was similar to that of graphene. We found that the resemblance of the vibrational spectra was closely related to the similarities of the lattice structures. Using the amplitude analysis, we were able to identify the eigenmodes of the various composites as motions of nodes in the graphene region or in the h-BN region or at the interfacial boundaries between them.