We introduced high-density columnar defects as artificial pinning centers (APCs) for quantized vortices into YBa2Cu3O7-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 Jc 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).
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