Control of Y2O3 nano-islands density to introduce artificial pinning centers in YBCO thin films

We successfully introduced high-density linear defects as artificial pinning centers (APCs) of the quantized vortices into YBCO films, during the film deposition procedure. APCs were introduced perpendicular to the film surface by using the distributed nano-sized Y₂O₃ islands prepared on SrTiO₃(100) substrates. It is possible to induce strong changes on the shape and density of the Y₂O₃ islands by varying the deposition and annealing conditions. The highest Y₂O ₃ islands density, 226/μm², was obtained with fifteen laser pulses at 800°C of substrate temperature, and applying an annealing temperature of 800°C. Even if only a small fraction of the induced defects act as effective pinning centers, J_c of YBCO film grown on the Y ₂O₃ nanoislands/SrTiO₃ substrate increased to 1.8 × 10⁷ A/cm² (20 K, B//c, 0 T), which is 1.5 times higher than that of the pure YBCO film.