Isolation techniques and electrical characterization of single grain boundaries of Bi 2Sr 2CaCu 2O 2 high-temperature superconductor

Abstract

We have isolated single grain boundaries of a bulk material of polycrystalline high-temperature superconductor Bi 2Sr 2CaCu 2O 2 (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 grain 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∼( I− I c) n for I> I c with n∼1.2.