Frequency and Polarization Dependence of Thermal Coupling between Carbon Nanotubes and SiO2

TL;DR

This study investigates how frequency and polarization affect heat transfer between carbon nanotubes and SiO2, revealing phonon mode contributions and inelastic scattering effects through molecular dynamics simulations.

Contribution

It provides new insights into the phonon-specific mechanisms governing thermal boundary conductance at CNT-SiO2 interfaces.

Findings

Long wavelength phonons dominate heat transfer.

High frequency CNT phonons strongly couple with lower frequency modes.

Inelastic scattering enhances interfacial thermal transport.

Abstract

We study heat dissipation from a (10,10) CNT to a SiO2 substrate using equilibrium and non-equilibrium classical molecular dynamics. The CNT-substrate thermal boundary conductance (TBC) is computed both from the relaxation time of the CNT-substrate temperature difference, and from the time autocorrelation function of the interfacial heat flux at equilibrium (Green-Kubo relation). The power spectrum of interfacial heat flux fluctuation and the time evolution of the internal CNT energy distribution suggest that: 1) thermal coupling is dominated by long wavelength phonons between 0-10 THz, 2) high frequency (40-57 THz) CNT phonon modes are strongly coupled to sub-40 THz CNT phonon modes, and 3) inelastic scattering between the CNT phonons and substrate phonons contributes to interfacial thermal transport. We also find that the low frequency longitudinal acoustic (LA) and twisting acoustic (TA) modes do not transfer energy to the substrate as efficiently as the low frequency transverse optical (TO) mode.