Phononic thermal transport along graphene grain boundaries

TL;DR

This study demonstrates that grain boundaries in graphene significantly reduce phononic thermal conductivity through complex scattering mechanisms, impacting thermal management in graphene-based devices.

Contribution

It reveals the detailed phononic scattering processes at graphene grain boundaries using molecular dynamics and spectral analysis, a novel insight into thermal transport.

Findings

Phononic thermal conductivity decreases along graphene grain boundaries.

Periodic strain fields act as phonon diffraction gratings.

Grain boundaries induce diffuse and specular phonon reflections.

Abstract

We reveal that phononic thermal transport in graphene is not immune to grain boundaries (GBs) aligned along the direction of the temperature gradient. Non-equilibrium molecular dynamics simulations uncover a large reduction in the phononic thermal conductivity ($\kappa_p$) along linear ultra-narrow GBs comprising periodically-repeating pentagon-heptagon dislocations. Green's function calculations and spectral energy density analysis indicate that $\kappa_p$ is the complex manifestation of the periodic strain field, which behaves as a reflective diffraction grating with both diffuse and specular phonon reflections, and represents a source of anharmonic phonon-phonon scattering. Our findings provide new insights into the integrity of the phononic thermal transport in GB graphene.