Thermal transport in oxidized polycrystalline graphene

Abstract

Grain boundaries (GBs) and the spontaneous oxidization around GB regions are inherent features of graphene. In this paper, the thermal conductivity (κ) of oxidized polycrystalline graphene (PG) is studied using molecular dynamics simulation. The κ of oxidized PG decreases as oxygen (O) coverage increases, which is due to the phonon-defect scattering. However, the relative κ reduction of oxidized PG is much smaller compared to that of oxidized single-crystalline graphene (SG) with the same O coverage when oxidation is localized at the GBs. This is because the GBs themselves are already strong phonon scatterers, such that O atoms residing at the GBs have far less impact on κ as compared to the O atoms in uniformly oxidized SGs. An effective medium approximation model is developed, which predicts that the influence of both GBs and O atoms on the κ of oxidized PG becomes smaller as the grain size increases, such that the κ of oxidized PG approaches the κ of pristine SG at the large grain limit. The results in this work offer important insights to the thermal transport physics in oxidized PG and provide useful information for the design of graphene-based devices for nanoelectronics and thermal management applications.