Thermal Resistivity at Interfaces between Metal and Dielectric Films at 1.5° to 4.2°K

Measurements of the thermal resistivity at interfaces between metal and dielectric thin films and a bulk substrate are reported. The thin-film structures are representative of a variety of superconducting devices with electrically insulated components. Results were obtained for single and multiple layers from 1.5° to 4.2°K. The magnitude of the observed values are within the range of the Little formulation if only longitudinal phonon contribution is considered. The temperature dependence is approximately T−2.5. The thermal resistivities decreased with increasing heat flux and temperature difference. The resistivity of multiple-layered structures was considerably less than the sum of the resistivities of each layer measured separately. This is consistent with wave propagation through layered media. No appreciable effect of film thickness was noted in the 0.2- to 2-micron range.