Interfacial thermal conductance at metal-nonmetal interface via electron-phonon coupling

Interfacial thermal conductance between dissimilar materials plays an important role in solving the overheating problem and thus improving the performance of photonic and electronic devices, especially those at micro- and nano-scale. However, conclusive heat transfer mechanism across interfaces is absent, especially across metal-nonmetal interfaces. Heat transfer across a metal-nonmetal interface is determined by the interplay among different heat carriers. In the metal, both electrons and phonons carry heat, while in the nonmetal, only the phonons are the dominant heat carriers. The interactions among these carriers can be classified into three categories, which correspond to three heat transfer channels, i.e. (i) phonon(metal)-phonon(nonmetal) interactions, which have been widely studied on the basis of the acoustic mismatch theory, diffuse mismatch model, lattice/molecular dynamics simulations; (ii) electron(metal)-phonon(metal) interactions followed by phonon(metal)-phonon(nonmetal) interactions, which were introduced to provide thermal resistance in series with that of the first channel; (iii) electron(metal)-phonon(nonmetal) direct interactions. The third channel has been introduced in order to explain the deviation between experimental results and the existing models incorporating the channel (i) and the channel (ii). Currently, there have been no models to comprehensively capture the underlying mechanism, mainly due to the difficulty in determining/defining the interfacial states at microscopic level and the temperature. Experimentally, it is hard to distinguish the contributions from these channels due to the resolution/sensitivity of the experimental system. Therefore, we here mainly concern with the investigations on the contributions of the channel (iii) from both experimental and theoretical aspects.