Transport properties in Tl-Ba-Ca-Cu-O grain boundary junctions on SrTiO₃ bicrystal substrates

We have investigated the electrical properties of Tl-Ba-Ca-Cu-O high-T c superconductor bicrystal grain boundary junctions. The behavior of the transport parameters is very similar to those obtained in YBaCuO 7-δ junctions. In particular, the temperature dependence of the critical current and the scaling behavior of the critical current density as a function of the misorientation angle were analyzed. Relatively good control of the transport parameters as a function of the misorientation angle has been achieved. The current-voltage characteristics showed a resistively shunted junction model-like behavior at large angles (θ≥20°); at lower angles, the characteristics were more flux-flow like. Preliminary results on noise characteristics are also presented.