Distribution analysis of thermal effusivity for sub-micrometer YBCO thin films using thermal microscope

Abstract

Thermal effusivity measurements have been carried out for sub-micrometer YBCO superconducting films using thermal microscope based upon thermoreflectance technique. Two samples were prepared: c-axis aligned YBCO thin films with 800 nm in thickness synthesized on MgO and SrTiO 3 substrates. Measured thermal effusivities perpendicular to the surface, i.e. in parallel with c-axis were determined to be 1770 J/m 2 s 0.5 K on MgO substrate and 1420 J/m 2 s 0.5 K for that on SrTiO 3 substrate, respectively. The scatter of the measurements is estimated to be lower than ±5.2%. These values are consistent with reported values of YBCO single crystal in the direction of c-axis. In addition, 2D profiling image, that is, in-plane distribution of thermal effusivity was well obtained for the YBCO film on MgO substrate by operating this thermal microscope in a scanning mode. Its standard deviation of the in-plane thermal effusivity scattering due to the non-uniformity is evaluated to be ±5.7%.