TRANSPORT THROUGH 90-DEGREES [010] BASAL-PLANE-FACED TILT AND TWIST GRAIN-BOUNDARIES IN YBA2CU3O7-DELTA THIN-FILMS

We have fabricated controlled grain boundaries between a- and c-axis films of YBa2Cu3O7-delta (YBCO). By selectively depositing c-axis and in-plane aligned a-axis YBCO on the same substrate, we have grown nominally 90-degrees [010] basal-plane-faced tilt and twist grain boundaries (BFGB's and TGB's) on LaSrGaO4 (LSGO) substrates and have studied their transport. We find that the TGB is very robust, exhibiting high critical current density J(c) and weak field dependence, and is as well coupled as our [010] antiphase boundaries. The BFGB is not as strong, but couples better than high-angle [001] tilt grain boundaries in c - axis films. Although the BFGB's do limit J(c), they do not reduce J(c) by more than an order of magnitude and the field dependence is very weak. We discuss these grain boundaries in terms of weak links.