Preparation of superconducting multilayer structure for power electronic devices

Multi-step KrF excimer pulsed laser deposition (MSPLD) technique has been developed to fabricate high-quality micrometer thick superconducting YBa₂Cu₃O_7-x (YBCO) films. As has been shown, a crystallization of YBCO at the initial stage of deposition crucially affects on thick YBCO film performance. Smooth, c-axis oriented 1-μm thick YBCO films with the critical temperature of T_c(zero) = 89.5 K and the overall critical current density of J_c(77 K) = 10⁵ A/cm² have been prepared on the single crystal MgO substrate in three-step process by monitoring the laser fluence, laser repetition rate and substrate temperature. Micrometer thick YBCO films on the single crystal LaAlO₃ substrate show T_c(zero) = 85.7 K and J_c(77 K) = 10³ A/cm², indicating that optimization of MSPLD processing conditions is much more critical for substrates with a small substrate/film lattice mismatch. Furthermore, Pb(Zr,Ti)O₃(PZT)/YBa₂Cu₃O_7-x/MgO heterostructures have been prepared by MSPLD technique with the critical temperature of T_c(zero) = 82.0 K in superconducting YBCO layer.