Effects of Joint Vibrational States on Thermal Boundary Conductance

The accuracy of predictions of the thermal boundary conductance (hBD) made using traditional models such as the diffuse mismatch model (DMM) varies depending on the types of material comprising the interface. At interfaces of materials with very different material properties, the discrepancy between the measured hBD and the DMM results has been associated with inelastic scattering. In this study, a new model, the joint frequency diffuse mismatch model (JFDMM), is derived under the assumption that the phonon flux approaching the interface is altered by phonons vibrating at joint frequencies around the interface affected by phonons on both sides of the interface. This model yields improved hBD predictions for a wide range of materials over a temperature range of several 100s of Kelvin, indicating that at these temperatures, substrate phonons are participating in interfacial thermal transport.