Abstract
The modulated optical reflectance (MOR) method is applied for nondestructive characterization of high-temperature superconducting (HTS) films and thin-film devices. An optimized optical scheme is developed employing He–Ne laser and diode laser of 780nm wavelength, and via a photodetector aligned to a lock-in amplifier, which is able to monitor the reflectance and technological inhomogeneity in the focal spot on the sample film. Microwave coplanar resonators patterned from YBa2Cu3O7−x (YBCO) films of 100nm thickness have been examined employing the MOR scheme. Unmodulated reflectance signals and MOR are compared between YBCO film and the substrate, MOR scans provide better indication of the structural differences due to the employed thermal modulation. A characteristic feature of YBCO films with embedded oxide crystals, referred to as assemblies of imperfections, could be detected. Automation of the scanning process and computerization of data acquisition are being developed.
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