INPLANE TEXTURE AND TRANSPORT-PROPERTIES OF YBCO FILMS GROWN ON MGO CUT OFF-AXIS

The microstructure of YBa2Cu3O7 thin films grown by pulsed laser deposition on (001)-oriented MgO substrates cut at different angles off-axis was studied by x-ray diffraction and transmission electron microscopy. The films consist of twin-related grain domains with the c axis normal to the surface. The in-plane texture was found to be epitaxially related to the substrate lattice as predicted by the near-coincidence site lattice theory. An increase in the number of grain orientations and their relative populations was observed when the angle at which the substrate was cut off-axis increased, corresponding to a deterioration of the electrical transport properties. Growth of preferred orientations was observed in a sample cut at a high off-axis angle. The bias toward a particular direction has been explained in terms of a constraint induced by surface steps in the grain nucleation.