Thermal conductivity of graphene flakes: Comparison with bulk graphite

TL;DR

This paper presents a simple model for graphene's lattice thermal conductivity, showing it can surpass bulk graphite in large flakes due to its two-dimensional phonon transport, aligning with experimental data.

Contribution

Introduces a model using Klemens approximation with mode-specific Gruneisen parameters to predict graphene's thermal conductivity based on flake size.

Findings

Thermal conductivity increases with flake size.

Graphene's thermal conductivity can exceed that of bulk graphite.

Model aligns with experimental observations.

Abstract

The authors proposed a simple model for the lattice thermal conductivity of graphene in the framework of Klemens approximation. The Gruneisen parameters were introduced separately for the longitudinal and transverse phonon branches through averaging over phonon modes obtained from the first-principles. The calculations show that Umklapp-limited thermal conductivity of graphene grows with the increasing linear dimensions of graphene flakes and can exceed that of the basal planes of bulk graphite when the flake size is on the order of few micrometers. The obtained results are in agreement with experimental data and reflect the two-dimensional nature of phonon transport in graphene.