Meandering grain boundaries in YBa₂Cu₃O_y bi-crystal thin films

Artificially induced [001] tilt grain boundaries in epitaxial YBa₂Cu₃O_y (YBCO) thin films were prepared by deposition onto SrTiO₃ bi-crystal substrates and subsequently examined by transmission electron microscopy and atomic force microscopy (AFM). It was found that the YBCO grain boundary deviated from the path defined by the underlying substrate boundary, with the]] meandering" YBCO boundary only generally following the path defined by the boundary in the underlying substrate. The AFM studies suggest this]] meandering" behavior is related to the nucleation and growth mechanisms of the film, and based on this, we were able to vary the magnitude of the meandering by changing the growth conditions. The implications of this meandering behavior are significant, suggesting potential variations in electrical behavior from point to point along these boundaries. This effect is likely to be exacerbated by reduced junction linewidths and may lead to inconsistent behavior in devices which utilize this type of boundary.