Influence of the electron-phonon interfacial conductance on the thermal transport at metal/dielectric interfaces

TL;DR

This study investigates how direct electron-phonon coupling at metal/dielectric interfaces can enhance thermal conductance, challenging the traditional view that it is solely resistive, with implications for nanoscale heat management.

Contribution

The paper introduces an analytical and numerical analysis showing that direct electron-phonon coupling can increase interfacial thermal conductance, contrary to previous assumptions of its resistive nature.

Findings

Direct electron-phonon coupling enhances thermal conductance.

Resistive effects are significant only for thin, weakly coupled metals.

Implications for interpreting thermoreflectance experiments.

Abstract

Thermal boundary conductance at a metal-dieletric interface is a quantity of prime importance for heat management at the nanoscale. While the boundary conductance is usually ascribed to the coupling between metal phonons and dielectric phonons, in this work we examine the influence of a direct coupling between the metal electrons and the dielectric phonons. The effect of electron- phonon processes is generally believed to be resistive, and tends to decrease the overall thermal boundary conductance as compared to the phonon-phonon conductance {\sigma}p . Here, we find that the effect of a direct coupling {\sigma}e is to enhance the effective thermal conductance, between the metal and the dielectric. Resistive effects turn out to be important only for thin films of metals having a low electron-phonon coupling strength. Two approaches are explored to reach these conclusions. First, we present an analytical solution of the two-temperature model to compute the effective conductance which account for all the relevant energy channels, as a function of {\sigma}e , {\sigma}p and the electron-phonon coupling factor G. Second, we use numerical resolution to examine the influence of {\sigma}e on two realistic cases: gold film on silicon or silica substrates. We point out the implications for the interpretation of time-resolved thermoreflectance experiments.