Thermal transport in bent graphene nanoribbons.

This work reports on a study of the phonon behavior and thermal transport in bent graphene nanoribbons (GNRs). Three peculiar phenomena are observed in bent GNRs during thermal transport. First, due to the high thermal conductivity of flexural mode (ZM) phonons in GNRs, energy separation is observed between the in-plane and out-of-plane phonon modes after a steady state heat flux is imposed on the system. Such energy separation can hold for about 50 nm from the heating region. Second, a thermal resistance is observed in the bending region of a 90° bent GNR system. This phenomenon is explained by the phonon energy scattering/reflection and the compressive strain in the bending structure. Different bending angles are investigated and it is proved that the bending resistance decreases with increasing bending angle. Finally, upon crossing the bending structure in GNRs, phonon packages preserve their vibrating mode instead of vibrating directions.