Properties of epitaxially grown a-axis oriented YBa2Cu3O7-x-PrBa2Cu3O7-y heterostructures

Multilayer structures of YBa2Cu3O7-x-PrBa2Cu3O7-ywere prepared, using pulsed laser deposition,withthe a-axisoriented normal to the surface of a variety of (001) substrates. Structural characterization of these films by X-ray diffraction (XRD), transmission electron microscopy (TEM) and helium ion beam channeling reveal a highly ordered microstructure similar, if not better, in quality to that obtained in the best c-axis oriented films. Studies of the surface morphology by scanning electron microscopy (SEM) show a very smooth surface with a total absence of the outgrowths commonly seen in c-axis oriented films. We observe that while the a-axis oriented films grown on (001) substrates show no a-b axis twinning, the films are composed of 0.01-0.1 µm sized domains that have the Y(Pr)Ba2Cu3O7-x c-axis oriented along thesubstrate (100) or (010) in-plane direction. Superconducting transition temperatures, for current transport the plane of the films, consistently exceed 80 K and are found to increase with the size of the domains. © 1991 IEEE