Transport properties of high-T-c planar Josephson junctions fabricated by nanolithography and ion implantation

We have developed a process for fabrication of planar high-T-c Josephson ju nctions using nanolithography and a 200 keV ion implanter. Conduction occur s in the ab plane and has no metallurgical interface. Devices may be tuned to operate at temperatures between 1 K and the T-c of the undamaged superco nducting material by varying the length of the weak link or by changing the amount of ion damage. We have examined the normal state and superconductin g properties of these films and find behavior consistent with a de Gennes d irty limit proximity effect model. Current-voltage curves, I-c(T) and R(T) data suggest a temperature dependent superconducting-normal metal interface that we have incorporated into the proximity effect model. (C) 2000 Americ an Institute of Physics. [S0021-8979(00)04602-8].