Modification of pinning in YBa 2 Cu 3 O 7 thin films by substrate annealing
To improve the usefulness of superconducting devices the critical current density (Jc) oftenneeds to be improved ormodified. This can simply be done by increasing the amount of defects present, allowing more magnetic flux to be trapped. These defects can be introduced artificially after deposition by use of for instance controlled holes throughout the surface (antidots), or prior to deposition by manipulating the procedure or substrate type/surface. In this paper, LaAlO3 substrates were annealed at 1000 °C for 2 h prior to deposition of approximately 250 nm of YBa 2 Cu 3 O 7 . Across several depositions, on average the Jc of the annealed substrate film is improved∼10-15% relative to a plain substrate film. Aside from a Jc enhancement, the annealed substrate samples were found to have a much higher consistency between depositions, particularly at lower applied magnetic fields. Furthermore, ion beam etching is often required on the substrate for fabrication of superconducting devices. This paper has shown that annealing can restore the substrate surface to the same quality as the manufactured plain substrate, based on the very similar Jc values.