Influence of Hot Electron Scattering and Electron-Phonon Interactions on Thermal Boundary Conductance at Metal/Nonmetal Interfaces

It has recently been demonstrated that under certain conditions of electron nonequilibrium, electron to substrate energy coupling could represent a unique mechanism to enhance heat flow across interfaces. In this work, we present a coupled thermodynamic and quantum mechanical derivation of electron-phonon scattering at free electron metal/nonmetal substrate interfaces. A simplified approach to the Fermi's Golden Rule with electron energy transitions between only three energy levels is adopted to derive an electron-phonon diffuse mismatch model, that account for the electron-phonon thermal boundary conductance at metal/insulator interfaces increases with electron temperature. Our approach demonstrates that the metal-electron/nonmetal phonon conductance at interfaces can be an order of magnitude larger than purely phonon driven processes when the electrons are driven out of equilibrium with the phonons, consistent with recent experimental observations.