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a-Axis oriented NdBa2Cu3O7-δ/PrBa2(Cu,Co)3O7-δ/ NdBa2Cu3O7-δtrilayers were prepared on (100) SrTiO3substrates. The trilayers were sputtered using a DC-95MHz hybrid plasma. The I-V characteristics of the trilayers were analyzed as a function of PrBa2(Cu,Co)3O7-δthickness (25–100 nm). In the case of the 50 nm thick PrBa2(Cu,Co)3O7-δlayer, the I-V characteristics show clear Shapiro steps corresponding to 7–20 GHz microwave irradiation. The Fraunhofer pattern was also observed for applied magnetic fields up to 1.00x10–3T.

Homoepitaxial NdBa2Cu3O7-y (NBCO) thin films have been prepared on NBCO (001) substrates in a cold wall lateral flow reactor by metalorganic chemical vapor deposition. It was observed by atomic force microscopy that one-unit-cell-high step structure or grains grew on as-polished substrate according to each growth condition. We found that zigzag steps appear when the initial steps on the as-polished substrate run off the [100] and [010] directions.

We successfully created a smooth surface on liquid phase epitaxially (LPE) grown YiBa2Cu3O7-δ (YBCO) films by employing a mechanical polishing process. We used an alumina powder with an average grain diameter of 0.03µm which was dispersed in oil for mechanical polishing, which made it possible to avoid a degradation of the Tc value for YBCO. While the as-grown surface of LPE-YBCO films contains various pyramidal structures with heights of about 400nm, the polished surface has only a roughness of 2 to 3nm as measured by a step profiler. A χmin value of 2.6% according to Rutherford backscattering spectrometry suggests that the damage after mechanical polishing is negligible. After annealing in O2 gas at 1 atm, the polished YBCO films transformed from tetragonal to orthorhombic phase and had a Tc value of about 91K.

The a-axis oriented PrBa2Cu3O7-δ. films and PrBa2Cu3O7-δ. /NdBa2Cu3O72δ/PrBa2Cu3O7-δ multilayers were deposited on (001) YBa2Cu3O7-δ and (001) NdBa2Cu3O7-δ single-crystal substrates using a DC-95MHZ hybrid plasma sputtering method to form ramp-edge SNS junctions with a ground plane. We found that both the PrBa2aCu3O7-δ film and the multilayer showed less precipitates on the surface of (001) NdBa2Cu3O7-δ substrate than that of (001) YBa2Cu3O7-δ substrate by atomic force microscopy measurements. Futhermore, the multilayers deposited on (001) YBa2Cu3O7-δ substrate and (001) NdBa 2Cu3O7-δ substrate had precipitates on the surface, while that deposited on the multilayered SrTiO7-δ substrate, PrBa2Cu3O7-δ/ NdBa2Cu3O7-δ/ SrTiO3, for reference had no precipitates. An electric resistance of the PrBa2Cu3O7-δ film on (001) YBa2Cu3O7-δ substrate was measured by a standard four-probe method. The electric resistance vs temperature curve suggested the tendency of becoming superconductivity below 13 K.

We have investigated the surfaces of YBa2Cu3O7-δ and NdBa2Cu3O7-δ single crystals using 950keV He+ Rutherford backscattering spectrometry and the ion channeling technique. The surface stability at temperatures up to 780°C was examined as a function of oxygen pressure. We found that the YBa2Cu3O7-δ and the NdBa2Cu3O7-δ crystal surfaces were stable at high temperatures in a limited O2 pressure between 1mTorr and 1Torr. Beyond this range, the YBa2Cu3O7-δ surfaces deteriorated significantly at high temperatures, while the NdBa2Cu3O7-δ surfaces only showed a slight degradation. These results revealed that the crystalline surface of NdBa2Cu3O7-δ remains stable at high temperatures in a larger O2 pressure range than that of YBa2Cu3O7-δ.

We have investigated the surface of high quality YBa2Cu2Ox single crystal substrates, fabricated from YBa2Cu3Ox single crystals grown by the crystal pulling method, for homoepitaxy. They have good crystallinity with χmin of under 2% evaluated by Rutherford backscattering spectrometry and good surface morphology with unit-cell steps observed by atomic force microscopy. Furthermore, we also discuss the initial stage of homoepitaxial growth by using metalorganic chemical vapor deposition method and YBa2Cu3Ox single crystal substrates as mentioned above.