TRANSPORT-PROPERTIES AND SURFACE-MORPHOLOGY IN Y123 FILMS ON METALLIC SUBSTRATES WITH GRAIN-ORIENTED BUFFER LAYER

It has emerged after many years of research that to obtain good-quality high-T(c) superconducting Y1Ba2Cu3O7-delta (referred to as Y123 here) films on metallic (Hastelloy C-276) substrates, cubic yttria stabilized zirconia (frequently referred to as YSZ) is an excellent buffer layer. It was found that the use of a Pt underlayer, under this buffer layer, helps the further improvement of the transport behavior in such films. In order to elucidate the effect of such metallic underlayer coatings in detail, we have used various other metallic underlayer coatings, like Pd, Au, Ag in addition to the previously used Pt, in this report. We show that the role of metallic underlayer coating is in improving the surface morphology. Thin layers (20 nm) of these metals with their noble properties act as a barrier for the interaction between the substrate and the buffer layer, and thus finally improve the surface morphology. Detailed X-ray measurements reveal that the quality of the films was directly linked to the percentage mismatch between the lattice parameters of YSZ and Y123 film. Two distinctly different grain morphologies are noticed. This difference is discussed in terms of the film quality.