Recovery of thermal transport in atomic-layer-deposition-healed defective graphene

Abstract

Large-scale graphene samples are mostly grown through chemical processes, which unavoidably introduce structural defects such as vacancies and adatoms that impede thermal transport. Recently, atomic layer deposition (ALD) utilizing metallic elements has proven healing capability of both structural defects and thermal transport in graphene, but the details of recovery mechanism have been elusive. In this study, we carry out molecular dynamics simulations to investigate the Pt-ALD-assisted healing reaction in graphene. Considering single (SV), double vacancies (DV) and C adatoms (C-ad) as representative imperfections, it is revealed that SVs and DVs are healed through direct Pt-filling and C adatoms are removed from graphene surface predominantly via dissociating O-2 molecules due to the catalytic effect of Pt. Moreover, examining thermal conductivity (kappa) shows that removal of C-ad plays a key role in recovering kappa whereas the improvement due to vacancy filling is insignificant. The spectral analysis of the lattice vibrations further demonstrates that the enhanced kappa originates from the enhanced mean free path of the flexural phonon modes in a low frequency range (<20 THz). (C) 2021 Elsevier Ltd. All rights reserved.