Preparation of YBa2Cu3O7−x superconducting thin films over large area substrates

Using facing targets and off‐axis direct‐current magnetron sputtering, we have prepared high quality YBa2Cu3O7−x (YBCO) superconducting thin films on ZrO2 (100) with Tc≤90 K (R=0) and Jc as high as 1.6×106 A/cm2 (78 K, zero magnetic field) over an area of 70 mm diameter. Over this large area, the fluctuations of Tc and film thickness are from less than +0.9% to −1.3% and from +6.3% to −10%, respectively. In this article, also discussed are the differences between two sputtering modes used in our experiments, one of which gives larger area of superconducting thin film, higher deposition rate, and better thickness uniformity than the other. It is found that the smoothness and the temperature uniformity of the substrate holder are a of extreme importance for the fabrication of large area superconducting thin films. An electroquartz with little deformation during deposition has turned out to be very successful as the substrate holder in our fabrication.