Multilayered structures of (RE = rare earth)Ba₂Cu₃O_<i>x</i>films: an approach for the growth of superior quality large-area superconducting films on sapphire substrates

Abstract

Relatively thick REBa2Cu3O7?? (RE = rare?earth) films (thickness ~400?600?nm) with significantly improved surface morphology and critical current properties using a multilayered structure which alternates main layers of YBa2Cu3O7?? (YBCO) with intermediate DyBa2Cu3O7?? (DyBCO) layers on CeO2-buffered sapphire substrates were investigated. The DyBCO layer, which has a close lattice matching with YBCO, functions as a good starting template for the growth of high-quality YBCO layers. Critical current density (Jc) drastically increased up to a factor of 2 for YBCO/DyBCO multilayer films, compared to YBCO monolayer films in both the self-field and applied magnetic field. The significant improvement in Jc is attributed to the improvement of surface smoothness and enhanced flux pinning properties as revealed by the magnetic-field angular dependence of Jc.