Thermal Transport of Flexural and In-Plane Phonons Modulated by Bended Graphene Nanoribbons

Changning Pan,Diwu Yang,Keqiu Chen,Jun He

doi:10.1155/2016/6093673

Abstract

Ballistic thermal transport properties are investigated comparatively for out-of-plane phonon modes (FPMs) and in-plane phonon modes (IPMs) in bended graphene nanoribbons (GNRs). Results show that the phonon modes transports can be modulated separately by the phonon dispersion mismatch between armchair and zigzag GNRs in considered system. The contribution of FPMs to total thermal conductance is larger than 50% in low temperature for perfect GNRs. But it becomes less than 20% in the bended GNRs. Furthermore, this contribution can be modulated by changing the structural parameters of the bended GNRs. The result is useful for the design of thermal or thermoelectric nanodevices in future.

Highlights

Graphene, a monolayer of carbon atoms honeycomb lattice, has attracted much attention due to its unique electronic and thermal properties
Negative differential thermal conductance and nonlinear thermal transport of graphene nanoribbons (GNRs) have been explored [14]; tunable thermal conductance has been observed in folded graphene and extended defects [15, 16]; the effective thermal rectifications have been found in asymmetric three-terminal graphene nanojunctions and asymmetric GNRs [17,18,19]
Lattice vibrations in the graphene can be classified as the in-plane phonon modes (IPMs) which vibrate in the plane of the layer with linear transverse and longitudinal acoustic branches and the out-of-plane phonon modes or the so-called flexural phonon modes (FPMs), which vibrate out of the plane of the layer [32]

Summary

Introduction

A monolayer of carbon atoms honeycomb lattice, has attracted much attention due to its unique electronic and thermal properties. One can calculate separately contributions of each type of mode to the total thermal conductance. Based on the exact numerical solution of the phonon Boltzmann equation, the authors studied the lattice thermal conductivity of graphene and found that the contribution is dominated by FPMs [32]. Most of the previous researches far investigate the total thermal conductance of the graphene and graphene-based devices or only focused on the thermal transport properties of FPMs for the graphene and GNRs. The systematic investigation of two types of phonon modes transport and how to tune separately their transport properties by thermal devices are paid less attention. The thermal transport of FPMs is weaker than that of IPMs in the lowenergy quantum transport, but it becomes more robust in the high-energy classical transport

Model and Formalism

Numerical Results and Discussion

Summary