Fabrication of 123‐type high‐ T _c superconducting thin films on BaZrO ₃ ‐buffered MgO substrates

Abstract

We have developed a stable preparation process for high-quality thin films of YBa 2 Cu 3 O y (123)-type high-T c superconductors (HTS) for the ground plane of single-flux-quantum (SFQ) devices. The films were deposited on MgO (100) substrates by an off-axis DC magnetron sputtering method. During deposition, the substrates were directly heated by thermal radiation from a heater. No adhesive paste was used for fixing the substrate. Possibility of chip contamination due to the paste could be completely eliminated. The insertion of a BaZrO 3 (BZO)-buffer layer was effective to obtain flat epitaxial 123 films with complete c-axis orientation. The flat ground plane could play a role as a suitable foundation for multilayer films of SFQ devices.

Characterization of La-doped YBCO superconducting films deposited by DC magnetron sputtering at various off-axis geometries

“…We deposited BZO buffer and thin template layers on MgO prior to DC-sputtered La-YBCO films, since it is significantly effective to promote c-axis orientation and in-plane alignment of YBCOtype superconducting films. 37) 40) We expected that the insertion could provide the ideal foundation for the DC-sputtered La-YBCO films through homo-epitaxial growth. In preliminary experiments, we already found a suitable deposition condition using the RF sputtering for La-YBCO showing c-axis orientation and a very flat surface with R a ³0.60 nm for 10 © 10¯m 2 .…”

Deposition of SmBCO superconducting films on Zr-rich BaZrO3-buffered MgO substrates

“…The RF power was 100 W. During film deposition, substrates were directly heated by thermal radiation from the rear side. The details of the substrate holder and the heater were previously described in [15,16]. The cationic ratio Ba/Zr, x, of the films was analysed by x-ray fluorescence spectroscopy (XRF).…”

“…In recent years, we have studied the fabrication process for ramp-edge-type Josephson junctions on a superconducting ground plane [12][13][14][15][16]. The fabrication technique for the multilayer structure of YbBCO(La-doped)/SrSnO 3 /YBCO (La-doped)/SrSnO 3 /YBCO(La-doped) on BaZrO 3 (BZO)buffered MgO substrates was already established.…”