Kohichi Kubo

Effects of Oxygen Partial Pressure and Substrate Temperature on Crystalline Orientation in Y-Ba-Cu-O Films Prepared by Sputtering

The dependence of crystalline orientation in Y-Ba-Cu-O films on oxygen partial pressure and substrate temperature has been investigated for films prepared by magnetron sputtering on (100) SrTiO3 and (100) MgO substrates. The tendencies for preferential orientation were the same on both substrates. At low oxygen pressures, the c-axis was oriented perpendicularly to the film plane. In contrast, a/c-axis oriented films were formed at intermediate oxygen pressures, and the a-axis was oriented at high oxygen pressures. At higher temperatures, c-axis oriented films were formed, even at high oxygen pressures.

Structural Features and Superconducting Properties of As-Grown Y-Ba-Cu-O Films

The structural features of superconducting Y-Ba-Cu-O films prepared by reactive sputtering have been discussed in relation to the preparation conditions. Conductivity anisotropy and the anomalous diamagnetic response observed for the films have also been discussed.

Effects of oxygen partial pressure on properties of Y‐Ba‐Cu‐O films prepared by magnetron sputtering

Dependence of orientation in Y‐Ba‐Cu‐O films on oxygen partial pressure has been investigated for films prepared by magnetron sputtering on SrTiO3 (100) planes. Orientations were closely related to the oxygen partial pressure in the 530 to 680 °C substrate temperature range. The dependence on substrate temperature was not observed clearly below 680 °C. At low oxygen pressure, the c axis was oriented perpendicular to the film plane. With an increase in oxygen pressure, the films tended to have a axis normal to the film surface. When the gas pressure during sputtering was 0.65 Pa with oxygen at 50%, zero resistivity was obtained at 70 K for many films without post annealing and 80 K for the best film. At higher oxygen pressure, the a axis was oriented with the expanded lattice parameter and superconducting films were not obtained without post annealing. At 0.32 Pa of oxygen, the oxygen uptake during film growth was most effective. At the higher substrate temperature of 730 C, c axis oriented films were formed.

Superconductivity and current-voltage characteristic of a YBCO/Ag/Pb junction

The electric property of a YBCO/Ag/Pb junction was examined by a novel measurement technique using a superconducting galvanometer. The residual resistance below Ic was less than 10 −14 ohm cm 2 . The current-voltage chracteristic above Ic was measured with a voltage sensitivity of 10 pV.