Biaxially aligned YSZ thin films with strong [100] fiber texture were formed on a polycrystalline Ni-based alloy by off-normal ion-beam-assisted deposition. Growth structures were characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), atomic force microscopy (AFM), etc., and the alignment mechanism was discussed using a selective growth model. Peculiar structural evolution of the crystalline orientation was observed and its development was well described by an exponential equation. It was explained as a collaboration of an anisotropic growth condition and epitaxial crystallization. The [100] fiber texture was formed by columnar structures of diameter of 30 -100 nm, which were composed of 5-10 nm diameter crystallites. Very smooth surfaces were observed by AFM imaging with a roughness of 2-3 nm and a peculiar ripple structure. The origin of the azimuthal alignment was discussed with emphasis on the surface structure of YSZ films produced using ion-beam-assisted deposition (IBAD) and the etching rate measurements of (100) surfaces of YSZ single crystals.

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Biaxially aligned YBa2Cu3O7−x (YBCO) films were fabricated on random Ni-based alloy tapes with yttrium stabilized-zirconia (YSZ) buffer layers deposited by ion-beam-assisted deposition (IBAD). Ar+ ion bombardment was found to have two significant effects on the crystalline structure of the YSZ buffer layers: to align a [100] axis with the substrate normal and a [111] axis with the bombarding beam axis. The resulting YSZ films were biaxially aligned on the random polycrystalline tapes, and the azimuthal distribution of the a- and b-axes of YBCO films on the top of the YSZ films was restricted to 10° FWHM. A critical current density (Jc) of 1.13 × 106 A/cm2 (77 K, 0 T) was obtained, and 1.1 × 105 A/cm2 was maintained at 5 T (77 K, B⊥c). The existence of both intrinsic and extrinsic pinning properties was clearly observed in the angular dependence of Jc with B⊥I. The longitudinal field effect on Jc was clearly observed, which indicated straight transport currents. This is evidence for strongly coupled current paths that demonstrate the bulk pinning properties of YBCO.

Self-field ac losses were measured by the conventional ac four-probe method in biaxially aligned Y–Ba–Cu–O tapes using polycrystalline Hastelloy tapes with textured yttria-stabilized-zirconia buffer layers. The ac losses increased in proportion to the fourth power of transport current in the high Jc sample, and agreed well with Norris’ equation for thin strip conductors. However, the low Jc sample had rather higher losses than Norris’ prediction, suggesting excessive magnetic flux penetration caused by percolated current paths. The results confirmed Norris’ prediction of the low ac losses for thin strip conductors, and indicated the importance of removing percolated structures of current paths to avoid higher ac losses than the theoretical predictions based on uniform conductors.

The dependence of the electromigration (EM) lifetime and the cross-sectional structure of interconnections after EM tests on linewidths was investigated in multi-level and single-level Al alloy interconnections consisting of a top–TiN/Ti/Al–0.5%Cu/TiN/Ti–bottom stack. In this study, an almost uniform Al3Ti intermetallic compound layer was formed by a well-known reaction between the Ti and Al. We found the following anomalous behavior: the mean time to failure (MTF) of EM in the multi-level interconnections with tungsten diffusion barriers decreased by increasing the linewidth. We also found that in the multi-level interconnections after EM tests, independent of linewidths, a local Al thickening formed near the anode end of the line and voids formed near the cathode end. On the other hand, in the single-level interconnections with bonding pads, the MTF of EM increased by increasing the linewidth and, after EM tests, a local Al thickening formed near the anode end even though no voids were observed near the cathode end. This directly opposed EM lifetime dependency on linewidth found in the multi-level and single-level interconnections and the observed Al thickening correlate closely with the fast diffusitivity of Al atoms at the interface between the Al3Ti and Al and/or between the Al3Ti and TiN.