The capacitance and the resistance of the Au/PrBa2Cu3Oy (PBCO)/YBa2Cu3Ox (YBCO) structure were measured at liquid helium temperature. A film of YBCO was deposited by rf magnetron sputtering at 700, and its thickness was 250 nm. A film of PBCO was deposited by rf magnetron sputtering at 690, and its thickness was less than 375 nm. The inverse capacitance and the resistance of the structure increased with PBCO thickness when PBCO thickness was more than 70 nm. However, the inverse capacitance was near zero, and the resistance was much less than that of PBCO itself when PBCO thickness was less than 70 nm. These results show the possibility that the electric property of PBCO within 70 nm from the PBCO/YBCO interface is different from that of PBCO itself, that is, there is a low-resistance region in PBCO near the YBCO/PBCO interface.

The Cooper pairing interaction in high Tc oxide superconductor is discussed in terms of an empirical expression; TcDexp[1/g], gcωo which was derived in our previous investigation. The dual character of this expression consisting of the phonon Debye temperature D and electronic excitation ωo in the mid-infrared region can be interpreted on the basis of the phonon-assisted mechanism on carrier conduction and the electronic excitation. A tunneling spectrum here presented shows certain evidence of the phonon contribution. The characteristics of the long range superconductive proximity phenomena recently reported are also may be interpreted by this mechanism.

Among the many fabrication methods for oxide superconductor films, metal organic chemical vapor deposition (MOCVD) is particularly suitable for industrial application because of its mass productivity and the low growth temperature. Therefore we have studied this technique using the horizontal cold wall furnace type MOCVD method to obtain high quality superconducting films. As the result, we have succeeded in fabricating YBa2Cu3Oy films which have high critical temperatures (over 80 K) under substrate temperatures as low as 700 without post-annealing. But, in the course of our experiments, it was found that the thicknesses of YBa2Cu3Oy films fabricated by MOCVD were not uniform. The cause of this non-uniformity is believed to be that the deposition rate exponentially falls off along the flow direction because of the decrease of the source gas concentration through the reaction. In this paper, this non-uniformity is analytically studied. It is shown that the deposition rate decrease can be controlled with a tapered inner tube, and that these theoretical results are in good agreement with the results of experiment. In addition, it is indicated that the superconducting property of the films has less dependence on substrate position as a result of the tapered inner tube.

The characteristics of a LiNbO3 light modulafor using the resonant YBa2Cu3Oy superconducting electrode were studied on the basis of the calculated results of surface resistances and transmission losses. The two-fluid model and the conventional transmission theory were used for the calculations. It was found that the modulation depth of this modulator using the YBCO electrode at 77 K was 7.5 times that using the Al electrode at room temperature. The drive voltage for the phase modulation of π radians was estimated to be a very low value of 2.3 V.

The characteristics of a LiNbO3 light modulator using the resonant YBa2Cu3Oy superconducting electrode were studied on the basis of the calculated results of surface resistances and transmission losses. The two-fluid model and the conventional transmission theory were used for the calculations. It was found that the modulation depth of this modulator using the YBCO electrode at 77 K was 7.5 times that using the Al electrode at room temperature. The drive voltage for the phase modulation of π radians was estimated to be a very low value of 2.3 V.