APPLICATION OF DIFFUSE MISMATCH THEORY TO THE PREDICTION OF THERMAL-BOUNDARY RESISTANCE IN THIN-FILM HIGH-T-C SUPERCONDUCTORS

Thermal boundary resistance (R-b) plays an important role in the desig n and performance of thin-film high-temperature superconducting device s, such as infrared detectors and optical switches, which rely upon th e temperature rise of the film as the basis for their operation. Altho ugh there is general agreement on the magnitude of R-b from experiment al data, there is at present no generally accepted theory capable of p redicting R-b for these films, particularly at the intermediate cryoge nic temperatures where they are likely to be used. Here, the Diffuse M ismatch Model (DMM), which considers that all phonons reaching the int erface between the film and substrate scatter diffusely, is applied to the calculation of R-b. The results indicate that when employing the Debye model for the phonon density of states, the DMM yields results s lightly more in agreement with data than the Acoustic Mismatch Model ( AMM). Considering the measured phonon density of states, however, grea tly increases R-b over that calculated assuming the Debye model, thus bringing the DMM results in relatively good agreement with the experim ental data.