EVIDENCE FOR CHANNEL CONDUCTION IN LOW MISORIENTATION ANGLE [001]-TILT YBA2CU3O7-X BICRYSTAL FILMS

Extended voltage-current (V-I) characteristics of [001] tilt YBa2Cu3O7 -x bicrystal films having misorientation angles, theta, of 3 degrees t o 20 degrees showed a substantial and progressive change with theta, w hen measured in large fields. Transmission electron microscopy of the 10 degrees bicrystal showed the grain boundary to contain edge disloca tions separated by channels of relatively undisturbed lattice. A large drop in the intergrain irreversibility field, H, occurred between 10 degrees and 15 degrees, and the characteristics became qualitatively different by 20 degrees. Both the microscopy and the electromagnetic d ata support a heterogeneous description of the grain boundary, consist ing of strongly coupled channels that close at a misorientation angle of around 15 degrees. (C) 1996 American Institute of Physics.