a-axis oriented epitaxial YBa2Cu3O7−x-PrBa2Cu3O7−y heterostructures

Abstract

We have grown YBa₂Cu₃O_7−x‐PrBa₂Cu₃O_7−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 YBa₂Cu₃O_7−x due to the presence of growth twin boundaries between grains with the c axis oriented along the two substrate directions.