Generalization of interfacial thermal conductance based on interfacial phonon localization

Interfacial energy transport is of great engineering and scientific importance. Traditional theoretical treatment based on phonon reflection and transmission only provides qualitative understanding of the interfacial thermal conductance (G). In the interface region, the material has gradual (covalent) or abrupt (van de Waals) physical structure transition, each transition features interface-region atomic interactions that are different from those of both adjoining sides. This difference makes the interface-region phonons extremely localized. Here, by constructing an “equivalent interfacial medium” (EIM) that accounts for the extremely localized phonon region, G can be described by a universal physical model that is characterized by an “interface characteristic temperature” (${\Theta }_{int}$) and energy carrier transfer time. The EIM model fits widely reported G ∼ T (T: temperature) data with high accuracy and provides remarkable prediction of G at different temperatures based on 2–3 experimental data points. Under normalized temperature (T/${\Theta }_{int}$) and interfacial thermal conductance (G/G_max), all literature data of G can be universally grouped to a single curve. The EIM model provides a solid correlation between G and interfacial structure and is expected to significantly advance the physical understanding and design of interfacial energy transport toward high-efficiency energy conversion, transport, and micro/nanoelectronics.