Fabrication and characterization of Y-Ba-Cu-O and Nd-Ba-Cu-O ramp-edge junctions with an interface-modified barrier

The fabrication process for YBa2Cu3O7-delta (YBCO) ramp-edge junctions with an interface-modified barrier has been studied. The conditions of electron cyclotron resonance (ECR) ion etching and following annealing treatment we re optimized by evaluating the mean roughness of the ramp surface using ato mic force microscope (AFM) observation. We could obtain resistively-shunted junction (RSJ) type current-voltage characteristics for the junctions with the counterelectrode YBCO layer deposited at temperatures lower than 720 d egreesC, while the deposition temperature higher than 755 degreesC resulted in a high-J(c) superconducting contact. The junctions exhibited an IcRn pr oduct of 1.0 - 1.9 mV and magnetic field modulation of I-c more than 90 % a t 4.2 K, By applying the optimum etching condition to a NdBa2Cu3O7-delta (N BCO) base electrode and employing a slightly higher annealing and depositio n temperature, YBCO/NBCO ramp-edge Josephson junctions with a similar IcRn product were successfully obtained.