Substrate-induced reduction of graphene thermal conductivity

TL;DR

This paper develops a theoretical model for heat conductivity in supported graphene, showing how substrate interactions significantly reduce phonon lifetimes and overall thermal conductivity, aligning with experimental observations.

Contribution

It introduces a Green's function and Boltzmann transport-based framework to quantify substrate effects on graphene's phonon spectra and thermal conductivity.

Findings

Substrate interactions drastically reduce phonon lifetimes.

ZA phonons' contribution to heat conductivity is suppressed.

Total heat conductivity decreases by several times, matching experiments.

Abstract

We develop the theory of heat conductivity in supported graphene, accounting for coherent phonon scattering on disorder induced by an amorphous substrate. We derive spectra for in-plane and out-of-plane phonons in the framework of Green's function approach. The energetic parameters of the theory are obtained using the molecular dynamics simulations for graphene on SiO$_2$ substrate. The heat conductivity is calculated by the Boltzmann transport equation. We find that the interaction with the substrate drastically reduces the phonon lifetime and completely suppresses the contribution of ZA phonons to the heat conductivity. As a result, the total heat conductivity is reduced by several times, which matches with the tendency observed for available experimental data. The considered effect is important for managing thermal properties of the graphene-based electronic devices.