Pore formation and increased critical current density in YBa₂Cu₃Oxfilms deposited on a substrate surface modulated by Y₂O₃nanoparticles

YBa 2 Cu 3 O 7− x (YBCO) films of thicknesses from 0.1 to 0.6 µm were grown on a 20 nm base layer of Y 2 O 3 particles. The particles typically have dimensions of ∼140 nm (radial) by ∼26 nm, and provide an isotropically modulated surface morphology on which the YBCO films are deposited. It was observed that the surface morphology of the YBCO film grown on the particles resembles the highly porous structure seen previously in vicinal YBCO films deposited on anisotropically modulated miscut SrTiO 3 substrates. Magnetic measurements also showed similarly enhanced critical current densities J c as observed in the vicinal films. The results provide a critical confirmation of strain-induced pore formation and improved J c by pore surface pinning.