Effect of substrate modes on thermal transport in supported graphene

Abstract

We examine thermal transport in graphene supported on SiO 2 using molecular dynamics (MD) simulations. Coupling to the substrate reduces the thermal conductivity (TC) of supported graphene by an order of magnitude, due to damping of the flexural acoustic (ZA) phonons. However, increasing the strength of the graphene-substrate interaction enhances the TC of supported graphene, contrary to expectations. The enhancement is due to the coupling of graphene ZA modes to the substrate Rayleigh waves, which linearizes the dispersion and increases the group velocity of the hybridized modes. These findings suggest that the TC of 2-D supported graphene is tunable through surface interactions, providing a novel possibility for controlled energy flow in nanomaterials.

Thermal properties of graphene: Fundamentals and applications

“…25,39 This decrease is also seen in Figure It is relevant to put such thermal properties of graphene in context. For comparison, the thermal conductivity of thin Si-on-insulator (SOI) films is also …”

“…However, it is possible that these modes could be partly suppressed or their dispersion altered when graphene is in strong contact with a substrate (thus lowering the specific heat), as suggested by experiments investigating epitaxial graphene on metals 23,24 and recent theoretical work on graphene on insulators. 25 At low temperatures (Figure 2 inset), the specific heat of a material scales as C p ~ T d/n for a phonon dispersion ω ~ q n in d dimensions. 10,26 Thus, the lowtemperature specific heat contains valuable information about both the dimensionality of a system and its phonon dispersion.…”

Effects of interfacial roughness on phonon transport in bilayer silicon thin films

“…For example, it has been shown that the in-plane thermal conductivity of multi-layer graphene 17 or supported graphene 8 is lower than that of suspended single-layer graphene, [17][18][19][20][21] which has been attributed to the interlayer phonon scattering or that between the supported graphene and the substrate. 17,[19][20][21][22] On the contrary, Guo et al's 23 and Ong et al's 24 results show that the coupling force plays an positive role in the enhancement of thermal conductivity. However, the underlying mechanism behind these phenomena is the change of phonon dispersion in the components of the coupling systems.…”

Substrate coupling suppresses size dependence of thermal conductivity in supported graphene

“…1(b)). To understand this distinct size dependence of thermal conductivity in suspended and supported SLG, we carry out the spectral energy density (SED) analysis Φ(k, ω)[24] for phonons in graphene (see supplementary information for calculation details), where k is the wavevector index, ω is the angular frequency.The SED is a very useful tool to extract phonon information (dispersion relation and lifetime) from MD simulation which can incorporate the full anharmonicity of the atomic interactions, and has been used in a number of studies [19,24,25].Previous theoretical study has suggested that thermal conductivity of graphene is dominated by contributions from ZA phonons [26], which have an anomalously large density of states near zone-center compared to the in-plane modes. Therefore, we focus on the zone-center ZA phonons in the SED analysis.…”

“…The SED is a very useful tool to extract phonon information (dispersion relation and lifetime) from MD simulation which can incorporate the full anharmonicity of the atomic interactions, and has been used in a number of studies [19,24,25].…”