Substrate-induced cross-plane thermal propagative modes in few-layer graphene

International audienceWe report the layer-number dependence of the averaged interlayer thermal resistances (Rint) of the suspendedand supported few-layer graphene (FLG), simulated by equilibrium molecular dynamics (EMD). The existenceof a silicon dioxide substrate significantly decreases the Rint of FLG at low layer number. We use the model oflong-wavelength dynamics of a nanolayer adsorbed on a deformable crystal [Kosevich and Syrkin, Phys. Lett.A 135, 298 (1989)] to explain the appearance of the substrate-induced gaps in the FLG dispersion curves andphonon radiation into the deformable substrate from these gap modes. The enhanced thermal conductance inthe cross-plane direction is ascribed to the phonon radiation from FLG into the deformable substrate, whichpartially transfers the flow of phonon energy in FLG from the in-plane to the cross-plane direction and to thesubstrate. To confirm this, we calculate the cross-plane thermal resistance of three-layer graphene supported byan effective SiO2 substrate in which atomic masses are increased by a factor of 1000. This makes the substratealmost immovable and suppresses phonon radiation from the supported FLG by complete phonon reflection atthe interface. The cross-plane thermal resistance of three-layer graphene supported on such a substrate is foundto be the same as its suspended counterpart