Substrate Coupling Suppresses Size Dependence of Thermal Conductivity in Supported Graphene

TL;DR

This study uses molecular dynamics simulations to show that substrate coupling reduces size dependence of thermal conductivity in supported graphene, with thickness and substrate effects varying between single-layer and few-layer graphene.

Contribution

It reveals how substrate coupling suppresses size dependence of thermal conductivity in supported graphene and explores the physics behind this phenomenon.

Findings

Supported SLG's thermal conductivity is length-insensitive.

Supported FLG's thermal conductivity increases with layer number.

Substrate effects are weaker in FLG compared to SLG.

Abstract

Thermal conductivity $\kappa$ of both suspended and supported graphene has been studied by using molecular dynamics simulations. Obvious length dependence is observed in $\kappa$ of suspended single-layer graphene (SLG), while $\kappa$ of supported SLG is insensitive to the length. The simulation result of room temperature $\kappa$ of supported SLG is in good agreement with experimental value. In contrast to the decrease in $\kappa$ induced by inter-layer interaction in suspended few-layer graphene (FLG), $\kappa$ of supported FLG is found to increase rapidly with the layer thickness, reaching about 90% of that of bulk graphite at six layers, and eventually saturates at the thickness of 13.4 nm. More interestingly, unlike the remarkable substrate dependent $\kappa$ in SLG, the effect of substrate on thermal transport is much weaker in FLG. The underlying physics is investigated and presented.