Effects of heteroepitaxy on the crystal structure in superconducting DyBa₂Cu₃O_7-x thin films

High-quality DyBa₂Cu₃O_7-x thin films were grown by molecular beam epitaxy (MBE). In contrast to the previous growth by MBE using co-deposition technique, we have employed an atomic-layer-by-layer shuttering sequence with in-situ RHEED feedback. Epitaxial films grown on various oxide substrates have a sharp superconducting transition above 80 K. Scanning-transition electron microscopy (STEM) shows atomically sharp substrate-film interfaces and the absence of stacking faults, unlike films previously grown by pulsed-laser deposition (PLD).
We employed synchrotron-based X-ray diffraction (XRD) to determine structural differences imposed by the heteroepitaxy with substrates with varying lattice parameters and crystal symmetry. A particular focus was put on the investigation of twinning which usually occurs in bulk orthorhombic crystal structure. However, in thin films the orthorhombic twinning can be hindered while the films still remain superconducting.