THERMAL-BOUNDARY RESISTANCE AND DIFFUSIVITY FOR YBA2CU3O7-DELTA FILMS

We have measured the thermoelectric response of off-c-axis epitaxial YBa2Cu3O7-δ films with thicknesses between 35 and 500 nm using laser pulses at uv and IR wavelengths. Due to the anisotropy of the thermopower in YBa2Cu3O7-δ, these off-c-axis films show a voltage response proportional to the average temperature gradient in the film which provides a sensitive probe of the temperature distribution within the film. A comparison of the experimetnal data and calculations with a thermal model for films with different thicknesses, allows us to extract the diffusivity of YBa2Cu3O7-δ and the thermal boundary resistance of the film-substrate boundary. Irradiating the films through the substrate leads to a situation where heat flow in the interfacial region dominates. The shape of the voltage signals depends strongly on the value assumed for the thermal boundary resistance. A consistent description for both illumination directions is found only in a narrow range around Rbd0.5×10-3 K cm2/W. © 1995 The American Physical Society.