Edge Effects on Phonon Dispersion and density-of-states of Graphene Nanoribbons and Nanoflakes

F. Mazzamuto ； A. Valentin ； C. Chassat ； J. Saint-Martin ； P. Dollfus

《Chinese Journal of Physics》 49卷1期 (2011/02) Pp. 31-40

並列摘要

We calculate the phonon dispersion and the vibrational density of states (VDOS) of semi-infinite GNRs and nanoflakes of various width and edge orientations using the force constant model including fifth-nearest neighbour atoms. Besides typical graphene peaks like E2g (G peak) and D, we clearly identify several distinctive ribbon peaks in ribbon VDOS depending on the edge shape. In particular, most of armchair modes have been detected at about 1350 cm^(-1) and 1480 cm^(-1), associated with strong localized in-plane vibrations, and at about 630 cm^(-1), associated with out-of plane vibrations. VDOS is also calculated for graphene nanoflakes to identify the minimal GNR length for which typical armchair and zigzag peaks can be observed. Typical localized modes appear for ribbon longer than 10 nm. Therefore, the edge nature can be identified by detecting the characteristic ribbon peaks in the VDOS.