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Several studies are conducted to measure the local current transport and the current sharing between different filaments in striated coated YBCO conductors with artificial defects. The local current crowding is found to be the main cause of the dissipation of the current in these conductors.

High-temperature superconducting Josephson junctions were grown in a ramp-edge superconductor-normal metal-superconductor (SNS) configuration using highly stable normal-metal barrier materials such as the cation-modified and corrosion-resistant compound (pryGd(sub 0.6-y))Ca0.4Ba1.6La0.4Cu3O7. The fabricated junctions were observed to exhibit well-defined RSJ-like current and voltage characteristics at liquid-nitrogen temperature.It was also noted that the junction performance is primarily regulated by the N-layer.

Transport measurements done at various applied magnetic fields were used in the critical-current measurements for YBa2Cu3O7-delta, Gd0.6Ca0.4Ba1.6LaO.4Cu3O7-delta and TX-GBCO/YBCO bilayer films which were prepared by pulsed laser deposition and patterned as microbridges. For TX-GBCO/YBCO bilayers, the highest Jc at 75 K in 5 Tesla was observed showing a 40% increase in Jc over YBCO under the same conditions.

Pulsed laser deposition on various single crystl substrates was used to fabricate epitaxial (rare earth)Ba2Cu3O7 films, RE123, with RE = Y, Er and Sm. Each material's deposition was optimized for T(sub c). An increase in ionic sized of the rare-earth element was observed in increased T(sub c) in RE123 films. In addition, the vortex pinning anisotropy was affected by the rare-earth element as shown by the study of field- and angle-dependent J(sub c).

The thickness and magnetic field dependence of the activation energy of thermally activated vortex motion in (Pr0.6Y0.4)Ba2Cu3O7/YBa2Cu3O7/(Pr0.6Y0.4)Ba2Cu3O7 heterostructures were studied. Specifically, measurements were carried out at fields up to seven tesla for films with a thickness of 1.2-120 nm. The results show that films whose thickness is approximately equal to the longitudinal vortex correlation length obey a logarithmic law at low fields and a power law at high fields.

A study on the deposition of ultra-thin YBa2Cu3O7-x/SrTiO3 (YBCO/STO) bilayers, which is used in the fabrication of superconducting field effect devices, is presented. Pulse laser deposition is used in studying the substrates and growth conditions of the YBCO/STO bilayers. Results indicate that the ideal temperature for substrates of YBCO films is lower than that for thick films and that high quality YBCO underlayers necessitate the lowering of the STO deposition temperature.

Investigating the spatial distribution of superconducting critical temperature, T(sub c)(x, y) from an epitaxial YBCO film in two different situations is discussed. The results show that the local superconducting transition occurs within 1 K suggesting that any samples with superconducting transition width larger than 1 K have local nonuniformity.

In the investigation, two wider-width superconducting films presented by variable temperature scanning laser microscopy are discussed. The results show that the study of larger superconducting samples using VTSLM is feasible, which is a significant step toward developing VTSLM for coated conductor diagnosis.

The buffer layers of 55% Pr (PY)BCO in trilayer structures and in YBCO/SrTiO3 superconducting field effect transistor devices are investigated. Results indicate that buffer layer thickness strongly influences transitions of ultrathin films in trilayer structures. Moreover, an optimal buffer layer of 5 nm is shown to improve transition temperature and critical current density. The findings agree with those obtained in previous research on non-weak-link dominated samples.

The IBAD and RABiTS coated conductors are me investigated by variable temperature scanning laser microscopy (VTSLM). In 50 μm scanning step images, IBAD samples appear to have more uniform current distribution than RABiTS samples, which can be related to the smaller grain sizes in IBAD. The images of IBAD samples taken with higher resolution reveal feather-like clusters with 40-150 μm in diameter. In RABiTS, the shape and size of percolation dusters are clear and do not change between high and low resolution images, and they are estimated to be 50-450 μm. VTSLM images prove that the current percolation in the transition region is due to the combination of the grain boundary network and the critical temperature variation. At the temperature below the critical temperature, the images of VTSLM show that the current bottleneck area causes the major local dissipation limiting Ic. We also find that the dissipation areas have lower Tc* and high δVm, an important characteristic shared among all the lower Jc* areas. [ABSTRACT FROM AUTHOR]

An YBCO coated conductor with a zipper pattern striation is investigated by scanning laser microscopy (SLM). The distribution of transport current deduced from the VTSLM images shows that striations act as artificial harriers forcing the current to flow around them. Current sharing and redistribution are observed at the zipper area. We find the major dissipation mechanism in the sample in the superconducting state to be the current crowding at bottleneck areas. The bottleneck seems to be caused by the disabled filaments at and around the zipper area. Some filaments show the dissipation away from the zipper area. In general, we find that the lower Jc* areas have lower Tc* and high δVm, which we consider as a sign of the current crowding. For the first time, we have demonstrated that there is a high temperature signature of the lower Jc* (high dissipation) area and VTSLM can detect the signature. [ABSTRACT FROM AUTHOR]