Structural characterization of YBa(2)Cu(3)O(7)/Y(2)O(3) composite films

Using 4-circle x-ray diffraction and transmission electron microscopy we have studied the microstructure and in-plane orientation of the phases present in thin film composite mixtures of YBa(2)Cu(3)O(7) and Y(2)O(3). We see a high degree of in-plane orientation and have verified a previous prediction for the in-plane order of Y(2)BaCuO(5) on (110) MgO. Transmission electron microscopy shows the composite films to be a mixture of two phases, with YBCO grain sizes of 1 micron. We have also compared our observations of the in-plane order to the predictions of a modified near coincidence site lattice model.Comment: To be published in Journal of Materials Research, (4 pages, 4 jpeg figures

Materials basis for a six-level epitaxial HTS digital circuit process

We have developed a process for fabrication of HTS single-flux-quantum logic circuits based on edge SNS junctions which requires six epitaxial film layers and six mask levels. The process was successfully applied to fabrication of small-scale circuits ({le} 10 junctions). This paper examines the materials properties affecting the reproducibility of YBCO-based SNS junctions, the low inductance provided by an integrated YBCO ground plane, and electrical isolation by SrTiO{sub 3} or SrAlTaO{sub 6} ground-plane and junction insulator layers. Some of the critical processing parameters identified by electrical measurements, TEM, SEM, and AFM were control of second-phase precipitates in YBCO, oxygen diffusion, Ar ion milling parameters, and preparation of surfaces for subsequent high-temperature depositions

Structure and transport properties of [001] tilt grain boundaries in YBa{sub 2}Cu{sub 3}O{sub x}

We have studied the microstructure and transport properties of nominal [001] tilt grain boundaries in order to correlate microstructural features with transport properties. single grain boundaries were prepared by epitaxial growth of YBa{sub 2}Cu{sub 3}O{sub x} onto bi-crystal SrTiO{sub 3} substrates. Transport measurements were used to characterize the electrical behavior across the boundary while TEM was used to characterize the structure of the boundary. The transport measurements are consistent with grain boundary behavior, but detailed comparisons show anomalies which may be resolved by microstructural characterization. Microstructural characterization showed that these artificially induced grain boundaries are periodically decorated by impurity phases. In addition, the boundaries are not always straight, but instead frequently meander away from the path of the underlying boundary in the substrate, and the various facets produced by the meandering show varying degrees of tilt and twist character. These structural variations suggest one potential explanation for the reduced effective coupling area, although the correlation is not unambiguous