(383d) Thermal Properties of Graphene Nanomeshes

Graphene has remarkable mechanical, electronic, and thermal properties, which can be tuned by properly modifying graphene structure and composition through patterning and chemical functionalization.  Graphene nanomeshes (GNMs) are graphene nanostructures consisting of a periodic arrangement of nano-scale holes or pores in the graphene lattice with neck widths less than 10 nm, mimicking dense arrays of ordered nanoribbons.  Establishing rigorous structure-property-function relationships in such patterned graphene nanostructures is significant for their optimal design toward enabling a broad range of technological applications.

In this presentation, we report the results of a systematic study based on molecular-dynamics (MD) simulations of the thermal properties of GNMs as a function of the nanomesh architecture determined by the lattice arrangement of the pores, pore morphology, material density (ρ), and pore edge passivation.  Scaling laws for the density dependence of the thermal conductivity k, k(r), are established.  Specifically, we find that, for circular unpassivated pores, 1/k scales linearly with 1/r.  For elliptical pores with aspect ratio (semi-major : semi-minor ellipse axis) f > 1, the thermal conductivity of the GNMs becomes anisotropic; the anisotropy becomes stronger as the GNM density decreases.  Passivating the nanomesh pore edges with H atoms increases the GNM thermal conductivity.  Further analysis of the phonon mean free paths based on the geometry of the GNMs shows that phonon transport in GNMs is dominated by phonon-pore edge scattering.  The results of Monte Carlo sampling of phonon mean free paths explain the scaling rules derived from the MD simulations.