Tuning of the critical current inYBa2Cu3O7−x thin films by controlling the size and density ofY2O3 nanoislandson annealed SrTiO3 substrates

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 wereintroduced perpendicular to the film surface using nanosizedY2O3 islandsprepared on SrTiO3(100) substrates by pulsed laser deposition. Varying the deposition parameters and thesubstrate annealing conditions allowed strong changes in the shape and density of theY2O3 islands to be induced. The best performance among the APC samples ascompared to the pure YBCO film was obtained for that grown on theY2O3-deposited substrate with five laser pulses, corresponding to 0.2Y2O3 monolayers (ML). Even when the 0.2 ML APC films were preparedusing the same deposition conditions, the columnar defects enhancedJc at 77 K from 1.8to 2.7 MA cm−2 (self-field)and from 0.06 to 0.10 MA cm−2 (H = 5 T).