Artificially generated bi-epitaxial YBCO grain boundary junctions on SrTiO/sub 3/ and sapphire substrates

In this work we present the fabrication and characterization of artificially generated bi-epitaxial YBCO grain boundaries on SrTiO/sub 3/ and buffered R-plane sapphire. The grain boundary is obtained by partly interposing a MgO seed layer between a bare or buffered substrate and a CeO/sub 2/ layer. We find that the structural perfection of the YBCO films decrease as the complexity of the stacking sequence increases. By comparing the structural properties of the YBCO film on the different stacking sequences with the transport properties of the fabricated devices, we found a strong correlation between the normalized junction resistance /spl rho//sub N/ and the degree of structural perfection in the superconducting film. The electrical behavior of the obtained junctions can be explained considering the grain boundary as a Josephson structure where the barrier transparency is related with the degree of structural and textural perfection of each superconducting electrode, justifying the correlation between the normalized junction resistance and the disorder in the YBCO films.