Thin superconducting Y-Ba-Cu oxide films formed by ion beam mixing

Abstract

Polycrystalline superconducting thin films of Y-Ba-Cu oxides have been prepared by vapour deposition of alternate layers of Y, Ba and Cu, followed by oxygen or xenon ion beam induced mixing and short-time post-annealing at temperatures up to 800°C. The mixed multilayers have been characterized by scanning electron microscopy, energy dispersive X-ray analysis, high-voltage electron microscopy and measurements of the resistance. The samples were completely superconducting between 79 and 82 K with onsets as high as 110 K. The topography of surfaces is characterized by two types of grains, where the so-called type-A grains have a composition close to the 1-2-3 stoichiometry. Electron diffraction studies have shown the superconducting phase to crystallize in a orthorhombic structure. The microstructure is dominated by lamellar domains. These have been identified as twins, does terminate O−Cu−O in the inter-Ba Cu−O planes.