Epitaxial arrangements of thin films and heterostructures of copper oxide based isotropic metallic oxides for use as barriers in SNS junctions

We have studied the epitaxial arrangement of thin films and heterostructures of copper-oxide based isotropic metallic oxides—La6.4Sr1.6Cu8O20 (LSCO), and La4BaCu5O13 (LBCO)—using four-circle x-ray diffraction and atomic force microscopy. All the films grow epitaxially ‘cube-on-cube’ with respect to the substrate. The single layer LSCO films were found to be very smooth (RMS roughness=5 Å) with a 90° rectangular grain structure. These films exhibit metallic conductivity and the bilayer La6.4Sr1.6Cu8O20/YBa2Cu3O7 (LSCO/YBCO) films show a sharp superconducting transition with Tc=88.4 K. Due to their structural and chemical compatibility with YBCO, these materials can be ideal normal metal barriers in fabricating SNS junctions with high junction resistance and low interface resistance.