Molecular dynamics simulations of thermal conductivity and spectral phonon relaxation time in suspended and supported graphene

摘要

We perform molecular dynamics (MD) simulations with phonon spectral analysisaiming at understanding the two dimensional (2D) thermal transport in suspendedand supported graphene. Within the framework of equilibrium MD simulations, weperform spectral energy density (SED) analysis to obtain the lifetime ofindividual phonon modes. The per-mode contribution to thermal conductivity isthen calculated to obtain the lattice thermal conductivity in the temperaturerange 300-650 K. In contrast to prior studies, our results suggest that thecontribution from out-of-plane acoustic (or ZA) branch to thermal conductivityis around 25-30% in suspended single-layer graphene (SLG) at room temperature.The thermal conductivity is found to reduce when SLG is put on amorphous SiO2substrate. Such reduction is attributed to the strengthened scattering in allphonon modes in the presence of the substrate. Among them, ZA modes are mostlyaffected with their contribution to thermal conductivity reduced to around 15%.As a result, thermal transport is dominated by in-plane acoustic phonon modesin supported SLG.