Photoresponse of epitaxial YBa2Cu3O7-x ultrathin films

The voltage photoresponse of YBa2CH307_ x/SrTiO3 10 nm-tlfick films\ud on laser irradiation is studied using the low temperature scanning laser\ud microscopy (LTSLM) teclmique. The irradiation wavelength is 633 run.\ud The spatial response dependencies via temperature (4-100 K), beam\ud intensity modulation frequency (0-150 kHz) and bias current are\ud examined. The bolometric and non-bolometric components are\ud separated. The amplitude of the non-bolometric component at 4.2 K is\ud about 10 times higher than that of bolometric one measured near the\ud midpoint of the superconducting transition. The non-bolometric\ud component is presumably associated with weak links in the film due to\ud interdiffusion of SrTiO3 into YBCO layer. The spatial irregularity in\ud superconducting parameters is not resolved by the LTSLM method\ud since the spacing between weak links is appeared to be less than 1 um

Laser scanning imaging and local characterization of superconducting properties in high-Tc thin film multiturn coil

Low-temperature scanning laser microscopy has been used to investigate the spatial variation of the critical temperature Tc and critical current Ic in thin-film high-Tc multilayer structures that include dielectric layers. The method is described and measurements are presented on an YBa2Cu3O7-x-based multiturn coil with SrTiO3 insulating layer. We found that the critical temperature Tc of the YBa2Cu3O7-x top layer, from which the return strip of the coil is formed, is higher than that of the YBa2Cu3O7-x base layer. The critical current of the coil is limited by the quality of the YBa2Cu3O7-x base layer and not by the edges of the crossovers