Distribution Measurement of Thermal Effusivity for YBCO Thin-film Superconducting Material Using Thermal Microscope

Abstract

Distribution measurement of thermal effusivity was carried out for c-axis aligned YBCO thin-film superconducting material using a thermal microscope based upon a thermoreflectance technique. The 800 nm-thick YBCO film synthesized on MgO substrate showed line-shaped damage by scanning a processing laser beam on the surface. The damaged YBCO film was prepared to be coated with a Mo thin film 100 nm in thickness before measurement. The thermal effusivity YBCO film with no damaged part was measured and determined to be 1890 J s^-0.5 m^-2 K^-1, on the basis of the calibration result of reference materials, Corning7740 and glassy carbon. The scatter of the measurement is estimated to be lower than 1.4%. A line-shape contrast image of thermal effusivity due to damaging the YBCO film was clearly observed. The thermal effusivity of the damaged part in the YBCO film was estimated to be 1.7% lower than that of non-damaged film. It was confirmed that a thermal microscope is applicable for homogeneity evaluation or defect inspection with about 1% resolution in the distribution measurement of thermal effusivity.