Tuning of the critical current in YBa₂Cu₃O_7−<i>x</i>thin films by controlling the size and density of Y₂O₃nanoislands on annealed SrTiO₃substrates

Abstract

We introduced high density columnar defects, as artificial pinning centres (APCs) for quantized vortices, into YBa2Cu3O7−x (YBCO) films during the film deposition procedure. APCs were introduced perpendicular to the film surface using nanosized Y2O3 islands prepared on SrTiO3(100) substrates by pulsed laser deposition. Varying the deposition parameters and the substrate annealing conditions allowed strong changes in the shape and density of the Y2O3 islands to be induced. The best performance among the APC samples as compared to the pure YBCO film was obtained for that grown on the Y2O3-deposited substrate with five laser pulses, corresponding to 0.2 Y2O3 monolayers (ML). Even when the 0.2 ML APC films were prepared using the same deposition conditions, the columnar defects enhanced Jc at 77 K from 1.8 to 2.7 MA cm−2 (self-field) and from 0.06 to 0.10 MA cm−2 (H = 5 T).