Critical current density enhancement in YBa2Cu3O7-δ thin films by twin domains of LaAlO3 substrates

Magnetic flux penetration into a 0.2 μm-thick YBa₂Cu₃O_7-δ (YBCO) thin film grown on a crystalline LaAlO₃ (LAO) substrate was studied using magneto-optical imaging techniques. Enhanced critical current density J_c was observed at the location corresponding to twin domains on the underlying substrate. We attribute this J_c enhancement to increased pinning defects in the YBCO layer induced by the naturally formed nano-scaled surface roughness on the LAO substrate. Our results suggest that the substrate surface roughness might be helpful in J_c improvement of YBCO thin films grown on metal substrates by pulsed laser deposition.