Critical current density and microwave surface resistance of 5-cm-diameter YBCO films on LaAlO 3 substrates prepared by MOD using an infrared image furnace

Abstract

Inductive critical current density ( J c) and microwave surface resistance ( R s) were investigated for 0.7-μm-thick epitaxial YBa 2Cu 3O 7− y (YBCO) films on 5-cm-diameter LaAlO 3 substrates prepared by a chemical solution-based metal organic deposition (MOD) process using an infrared image furnace. By varying the heating rate at ramp during the final heat treatment, we obtained various orientations of YBCO; the c- and a-axis orientation at a slower rate, i.e., 20–100 °C/min while the pure c-axis orientation at a faster rate, 200 °C/min. The c-axis-oriented YBCO films showed excellent superconducting properties; for example, a high inductive- J c (77 K) of 2.6 MA/cm 2 and low R s (12 GHz)’s of 0.24 and 0.52 mΩ at 50 and 77 K, respectively, by a sapphire rod resonator method. The c- and a-axis-oriented films exhibited a lower J c and a higher R s. It was found that the J c and R s values of MOD-derived YBCO films showed a strong correlation; approximately, R s is inversely proportional to J c. This correlation is in good agreement with a previous report by Ohshima et al. for sputtered-YBCO films on BaSnO 3-buffered MgO substrates.