The boundaries in laser-deposited thin films were investigated by means of high-resolution transmission electron microscopy. The films exhibited perfect texturing, with Cu3Ba2YO7(001)/MgO(001) giving rise to low-angle [001] tilt grain boundaries which resulted from grains having their c-axis normal to the substrate surface and with a misorientation in the a-b plane. The atomic structures of the grain boundaries were analyzed by using a dislocation model. Low-angle grain boundaries were found to be aligned along (100) and (110) interface planes. In the case of the (110) boundary plane, the low-energy dislocation configuration consisted of an array of alternating [100] and [010] dislocations. The energies of various configurations were calculated, and it was shown that the energy of the (110) boundary, with dissociated dislocations, was comparable to that of the (100) boundary. This explained the coexistence of (100) and (110) interface facets along the boundary. Critical current transport through grain boundaries having various structures were also modelled, and it was found that the low-energy (110) grain boundary - with dissociated dislocation arrays - was expected to transport a lower superconducting current (lower by 25% for a 6º misorientation) than did (100) boundaries.

Dislocation Structure of Low-Angle Grain Boundaries in YBa2Cu3O7/MgO Film. S.Oktyabrsky, R.Kalyanaraman, K.Jagannadham, J.Narayan: Journal of Materials Research, 1999, 14[7], 2764-72