Critical current enhancement in PLD YBa₂Cu₃O_7-x films using artificial pinning centers

We introduced high-density columnar defects as artificial pinning centers (APCs) for quantized vortices into YBa₂Cu₃O_7-x (YBCO) films during the film deposition procedure. APCs were introduced perpendicular to the film surface using nano-sized Y₂O₃ islands prepared on SrTiO₃(1 0 0) substrates. Varying the deposition parameters and the substrate annealing conditions allowed strong changes in the shape and density of the Y₂O₃ islands to be induced. Compared to a pure YBCO film, the best performance among the APCs samples was obtained on the Y₂O₃-deposited substrate with 5 laser pulses, corresponding to a nominal thickness of 0.2 nm. Even when the APC films were prepared using the same deposition conditions, the columnar defects enhanced J_c at 77 K from 1.8 to 2.7 MA/cm² (self field) and from 0.06 to 0.10 MA/cm² (H = 5 T, H∥c-axis).