Superconducting Nd1.85Ce0.15CuO4−y bicrystal grain boundary Josephson junctions

Abstract

We have studied the electric transport properties of symmetrical [001] tilt Nd1.85Ce0.15CuO4−y (NCCO) bicrystal grain boundary Josephson junctions (GBJs) fabricated on SrTiO3 bicrystal substrates with misorientation angles of 24° and 36.8°. The superconducting properties of the NCCO GBJs are similar to those of GBJs fabricated from the hole doped high temperature superconductors (HTS). The critical current density Jc decreases strongly with increasing misorientation angle. The products of the critical current Ic and the normal resistance Rn (∼100 μV at 4.2 K) are small compared to the gap voltage and fit well to the universal scaling law IcRn∝Jc found for GBJs fabricated from the hole doped HTS. This suggests that the symmetry of the order parameter, which most likely is different for the electron and the hole doped HTS, has little influence on the characteristic properties of symmetrical [001] tilt GBJs.