Deposition of Superconducting Thin Films on Amorphous and Artificially-Structured Substrates

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The goal of this project is to deposit, on amorphous or polycrystalline substrates, thin films of high Tc, rare earth- barium-copper-oxygen superconductors with critical current densities exceeding 1*106 A/cm2 at 77k. This capability would permit the direct replacement of integrated circuit interconnects with superconductors. The present limits in critical current density for polycrystalline superconducting films (typically 103 A/cm2) are associated with Josephson junctions at grain boundaries. In an effort to overcome this limitation, this project is aimed at controlling crystalline orientation and quality without invoking epitaxial growth. The potential of two quite different techniques will be evaluated. In the first approach, the ability of reactive ion beam assisted deposition to control oxygen content and crystal orientation of films will be explored. In the second, the possibility of "grapho-epitaxy", where the film is oriented with respect to an artificially structured substrate, will be explored.