Thermal-diffusivity measurements of an oriented superconducting-film–substrate composite using the mirage technique

When one measures the thermal diffusivity {χ} of a thin film on a substrate by the mirage method, the photothermal deflection of the probe beam is caused by the heat field contributed by both the film and the substrate which are heated by the pump beam. To include the effects due to the presence of the substrate, we present a method to measure the diffusivities of both the film and substrate in one set of mirage detection. Using the off-axis magnetron sputtering process, we fabricated YBa₂{Cu}₃O_7-δ thin films of suitable thickness ({~}60 nm) on SrTiO₃ as our sample for {χ} measurements along the c and b axes. Our results are consistent with published ones.