Properties of SNS Josephson Junctions Fabricated by 200 keV Oxygen Implantation into YBa2Cu3O7-δ

The properties of SNS Josephson junctions in YBa2Cu3O7-δ thin films have been investigated, which were fabricated by oxygen irradiation at 200 keV through a 50 nm wide slit in an implantation mask. After annealing the irradiated microbridges at 500°C in an oxygen atmosphere, the implanted region has a reduced but finite transition temperature, allowing Josephson coupling in a temperature window of < 15 K. Close to the coupling temperature the critical current shows a nearly complete modulation in an applied magnetic field. This indicates a homogeneous current distribution in the junctions and therefore a homogeneous defect distribution throughout the implanted and subsequently annealed region of the superconducting microbridges. Over the entire temperature range of Josephson coupling, the junctions exhibit resistively shunted junction like I-V characteristics with additional excess current. Furthermore, the exponential dependence of the critical current on temperature is in good agreement with conventional superconductor-normal-superconductor proximity effect theory.