A-AXIS ORIENTED EPITAXIAL YBA2CU3O7-X-PRBA2CU3O7-Y HETEROSTRUCTURES

We have grown YBa2Cu3O7-x-PrBa 2Cu3O7-y heterostructures with the perovskite a axis normal to the surface of a variety of (001) oriented substrates using the pulsed laser deposition technique. X-ray diffraction studies indicate little or no formation of the traditional c-axis normal orientation usually nucleated on these substrates, while ion channeling, transmission electron microscopy (TEM), and Raman scattering studies reveal a highly ordered crystalline structure similar in quality to that obtained in the best c-axis oriented films. Superconducting transition temperatures, for current transport in the plane of the films, consistently exceed 80 K, but are probably lower than the optimum 92 K transition expected for YBa2Cu3O7-x due to the presence of growth twin boundaries between grains with the c axis oriented along the two substrate directions.