Isolation techniques and electrical characterization of single grain boundaries of Bi2Sr2CaCu2O2 high-temperature superconductor

We have isolated single grain boundaries of a bulk material of polycrystalline high-temperature superconductor Bi2Sr2CaCu2O2 (Bi-2212) tapes. The tapes were grown on a single crystal of MgO or Ag-foil by partial melting of the superconductor. The isolation techniques consisted of fabricating metal micro-contact pads, wire bonding, and laser patterning of the Bi-2212 superconductor. Results of electrical and magnetic measurements of single gain boundaries suggested a possible existence of Josephson-like junctions coexisting with flux flow junctions. In contrast to bulk samples, T-c of a single grain boundary did not change by applying magnetic field. J(c) and T-c were found to be greatly dependent on heat treatment and growth conditions. The current-voltage characteristics of a single patterned bridge followed a relation of the form V similar to (I - I-c)(n) for I > I-c with n similar to 1.2. (C) 1998 Elsevier Science B.V.