HREM investigation of (110) oriented YBa₂Cu₃O₇ thin films deposited on (110) SrTiO₃ substrates

The epitaxial growth and microstructure of YBa₂Cu₃O₇ thin films on (110) SrTiO₃ substrates was investigated by high-resolution electron microscopy. The single thin films and heterostructures with PrBa₂Cu₃O₇ and SrTiO₃ separating the superconductor layers were deposited by DC sputtering. All layers were grown with the [110] direction perpendicular to the substrate surface with the c-axis of the YBa₂Cu₃O₇ film oriented parallel to the [001] direction of the substrate. Resistance measurements showed that, by applying a template growth procedure, T_c values of up to 85 K can be obtained. Stacking faults were found to be the dominant defect type in the superconducting film. A structural model for a novel type of these defects inducing a local 2-3-5 cation stoichiometry was deduced by comparison between experimental and simulated high-resolution images. Antiphase boundaries with a habit plane close to the (110) plane of YBa₂Cu₃O₇ were detected.