Properties of submicron [001] tilt symmetric and asymmetric 45? bicrystal grain boundary junctions

We have fabricated submicron YBa2Cu3O7-x [001] tilt bicrystal grain boundary junctions by a focused ion beam process. The reduction of the junction width, leading to more homogeneous grain boundary interfaces, has been proved to be very important for the study of many fundamental properties of high critical temperature superconducting junctions. In particular, experiments on 45° symmetric junctions have shown a clear evidence of midgap states, with a 0- to π- junction transition in the case of small barrier transparency; moreover, in 45° asymmetric junctions we have observed a transition from an unconventional to a Fraunhofer-like magnetic field dependence of the critical current, sign of the reduced influence of faceting on the junction properties.