Graphene-based SiC Van der Waals heterostructures: nonequilibrium molecular dynamics simulation study

The structural properties and thermal conductivity of graphene-based SiC heterostructures are investigated using the reverse nonequilibrium molecular dynamics. The C/SiC/C heterostructure has the greatest value of cohesive energy due to the effect of vdW interactions between layers. The surfaces of heterostructures begin to ripple as a direct consequence of the plane fluctuations observed around T = 400 K. The thermal conductivity at room temperature is determined. The length and the armchair and zigzag orientations increase the magnitude of κ which decreases with increasing temperature. This change is attributed to the phonon Umklapp scattering and phonon cross-plane couplings. The impact of point vacancy, bi-vacancy and edge vacancy in a concentration range up to 2% is also discussed. The localization of low-frequency phonons around the vacancy induces a decaying characteristic of thermal conductivity. The effect depends on the type of vacancy and is more pronounced in heterostructures with point vacancy. The present results make pristine and defective heterostructures promising materials for various thermoelectric applications with tunable functionalities.