The microstructure of YBa2Cu3O7-x thin films on SrTiO3 substrate

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Abstract
The microstructure of high-temperature superconducting thin films (YBa2Cu3O7-x) deposited on SrTiO3 (100) substrates has been investigated. These films show a critical current density several orders of magnitude higher than previously reported for this class of materials. This was found by aligning the superconducting phase epitaxially with the substrate so that the direction of highest current density is parallel to the substrate (the c-axis of the orthorhombic structure perpendicular to the substrate) and by pinning the vortices with a fine distribution of second-phase particles. It is shown that, near the substrate/superconductor interface, the film is indeed mostly epitaxial. Lattice images of this epitaxial interface are presented. A small part of the film near the interface is misoriented so that its c-axis lies parallel to the substrate, with either a or b perpendicular to it. Numerous second-phase particles (Y2O3 and CuO) are distributed throughout the superconducting phase. Epitaxy deteriorates further away from the interface, but the high critical current density can still be correlated to the observed morphology.