Control of Y₂O₃ nanoislands deposition parameters in order to induce defects formation and its influence on the critical current density of YBCO 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 nanosized Y₂O₃ islands prepared on SrTiO₃(1 0 0) substrates. It is possible to induce strong changes on the shape and density of the Y₂O₃ islands by varying the deposition conditions. The highest Y₂O₃ islands density, 226/μm², was obtained with fifteen laser pulses at 800 °C of substrate temperature. Even if only 10% 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.