Double-sided YBa2Cu3O7 (YBCO) films were successfully prepared on 50-mm-diameter CeO2-buffered sapphire substrates by metalorganic deposition (MOD) process using an acetylacetonate coating solution. Mapping analysis of superconducting current densities (Jc) at 77.3 K revealed that Jc values of the double-sided films indicated in excess of 2 MA/cm2 in the center parts with a small decrease of Jc at the outer side of the specimens. The Jc values of one side (A) are higher than those of the other side (B). Microwave surface resistance (Rs) of sides A and B of the film exhibited 0.57 and 0.60 mΩ, respectively, at 70 K (12 GHz). The difference in the Rs values should be attributed to the slight difference in the Jc values, which arose from the surface morphology of the CeO2 buffer layer and heat treatment conditions during the firing process in MOD.

In-plane-aligned a-axis-oriented YBa2Cu3O7-δ (YBCO) thin films are attractive for the formation of planar intrinsic Josephson devices. In this study, these films were deposited by dc sputtering on LaSrGaO4 (LSGO) (100) substrates and the dependence of the characteristics on the deposition conditions was investigated. In-plane-aligned a-axis-oriented YBCO thin films were successfully grown in the substrate temperature range of 555-615. With the temperature gradient method, it was seen that the critical temperature of the film increased to 81 K. The current-voltage characteristic along the c-axis exhibited clear multibranch structures. These results indicate that ion-cleaning of the substrate surface broadens the growth temperature range of these films and planar intrinsic Josephson devices can be fabricated from these films.

High-Tc superconductors convincingly showed that these materials are essentially natural arrays of Josephson junctions formed in atomic scale. In this paper, in-plane aligned a-axis-oriented YBa2Cu3O7-δ (YBCO) thin films were successfully grown on LaSrGaO4(LSGO) (100) substrates which were cleaned by ion-beam. Voltage jumps with hysteresis implying intrinsic Josephson effects are observed in c-axis direction. This result suggest that it is possible to achieve planar intrinsic Josephson devices which have applications in high frequency electronics, such as voltage standards, Josephson masers and so on.

2-pole band-pass filters (BPFs) with tap-excitation are prepared by using high temperature superconductors (HTS). The possibility of realizing superconducting coplanar filters with attenuation poles is revealed.

The electric field intensity of the THz radiation from YBCO thin films excited by ultrashort laser pulses has been enhanced by a factor of 3 using a-axis oriented films instead of c-axis oriented ones used previously under the same excitation conditions. This corresponds to the enhancement of a factor of 10 for the radiation power. From the transmittance measurements of the millimeter wave for a-and c-axis oriented films, the origin of the enhancement is attributed to the increased fraction of the THz electromagnetic wave power transmitted from the YBCO film to free space. This result indicates that the utilization of the anisotropic properties of high-Tc superconductors is effective to enhance the radiation power.

Amorphous films of YBCO and BSCCO (2212) sputtered on MgO substrate were crystallized using zonemelt technique. For YBCO films, thin Ag intermediate layer was found to be effective in enhancing crystal growth and preferred orientation. Zone-melted BSCCO films included both (2201) phase and Cu(Sr, Ca)O2 in a form of dendritic crystallites. Tc's obtained for YBCO and BSCCO films were 70 and 75 K, respectively.

Thin-film YBCO Josephson junctions were successfully fabricated by a pulsed excimer laser ablation, and the mixing experiments in the microwave region (820 GHz) were carried out at the temperature of 77 K. The IF output maximum was obtained at the bias voltage midway between the zero and the first Shapiro steps for the fundamental mixing. For the 2nd harmocic mixing, the IF output maximum was obtained at a zero bias voltage, and the conversion efficiency was -14 dB at the microwave frequency of 18 GHz. These results strongly suggest that the fabricated thin-film Josephson junctions work well at the temperature of 77 K as detectors and mixers in the microwave regions (820 GHz).