Phonon Thermal Conduction in Graphene

TL;DR

This paper provides a detailed theoretical analysis of phonon thermal conductivity in single-layer graphene, considering all phonon interactions, defect effects, and edge scattering, resulting in high predicted thermal conductivities consistent with experiments.

Contribution

It introduces a comprehensive model for phonon thermal conduction in graphene, including exact three-phonon processes and defect/edge scattering, with predictions matching experimental data.

Findings

Thermal conductivity of graphene ranges from 2000 to 5000 W/mK at room temperature.

Graphene edges significantly affect thermal conductivity due to long phonon mean free paths.

The model aligns well with recent experimental measurements of suspended graphene.

Abstract

We investigated theoretically the phonon thermal conductivity of single layer graphene. The phonon dispersion for all polarizations and crystallographic directions in graphene lattice was obtained using the valence-force field method. The three-phonon Umklapp processes were treated exactly using an accurate phonon dispersion and Brillouin zone, and accouting for all phonon relaxation channels allowed by the momentum and energy conservation laws. The uniqueness of graphene was reflected in the two-dimensional phonon density of states and restrictions on the phonon Umklapp scattering phase-space. The phonon scattering on defects and graphene edges has been also included in the model. The calculations were performed for the Gruneisen parameter, which was determined from the ab initio theory as a function of the phonon wave vector and polarization branch, and for a range of values from experiments. It was found that the near room-temperature thermal conductivity of single layer graphene, calculated with a realistic Gruneisen parameter, is in the range ~ 2000 - 5000 W/mK depending on the defect concentration and roughness of the edges. Owing to the long phonon mean free path the graphene edges produce strong effect on thermal conductivity even at room temperature. The obtained results are in good agreement with the recent measurements of the thermal conductivity of suspended graphene.