Tuning of the critical current in YBa2Cu3O7-x thin films by controlling the size and density of Y2O3 nanoislands on annealed SrTiO3 substrates

We introduced high density columnar defects, as artificial pinning centres (APCs) for quantized vortices, into YBa2Cu3O7-chi (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 J(c) 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 = 5T).