Ultra-low thermal conductivity in graphene nanomesh

Graphene nanomesh (GNM), a new nanostructure of graphene, has attracted extensive interest recently due to the promising chemical, electronic and photonic applications. In this paper, another important property – thermal conductivity is systematically investigated by using molecular dynamics simulations. The thermal conductivity (κ) is found to be extremely low, up to more than 3 orders lower than the pristine single layer graphene. Roughly, κ decreases exponentially with increasing porosity and linearly with decreasing neck width, and is not temperature sensitive in the range of 300 K–700 K. κ of GNMs is found to be even up to 200-fold lower than the graphene nanoribbons (GNR), a potential thermoelectric material, of the same neck width and boundary-to-area ratio. The extremely low κ in the GNM makes it a potential candidate for thermoelectrics. The phonon participation spectra show that the low κ in GNM is due to the localization and phonon back scattering around the nanopores. We also find that the phonon coherence in two dimensional superlattice GNM indeed exists, but is not as important as in the one dimensional superlattices. The isotope effect is negligible. The thermal conductivity reduction by edge passivation increases with increasing neck width and porosity.