Epitaxial growth of multilayered YBa2Cu3O7-δ/Y0.7Ca0.3Ba2Cu3O7-δ films for high current application

Multilayered YBa₂Cu₃O_7-δ (YBCO)/Y_0.7Ca_0.3Ba₂Cu₃O_7-δ (YCBCO) films were epitaxially grown on [001] LaAlO₃ and [001] SrTiO₃ by using pulsed laser ablation. Constant-high critical current density (J_c) of 106 A/cm² at 77 K has been achieved with the combination of multilayered YBCO and YCBCO layers for films with various thickness. The critical current density exhibits a high constant value for the multilayered structures indicating that the J_c in the superconductor films no longer decreases with the increase of the film thickness. The result verifies the model that interfaces can limit the density of dislocations that form in the film during the film growth. The artificial multilayered structures terminate the dislocations and the superconductive films at the optimal J_c conditions maintain a constant high J_c at various film thickness.