An ion-beam-assisted process for high-T-c Josephson junctions

We have developed a non-ion-etching ion-beam-assisted-deposition (IBAD) process for fabricating high critical-temperature (T-c) grain boundary Josephson junctions through a photoresist liftoff mask, The YBa2Cu3O7 (YBCO) junctions fabricated through this process exhibited the resistively-shunted-junction (RSJ)-like I-V characteristics. The well-defined Shapiro steps have been seen on the I-V curves under microwave radiation. The magnetic modulation of critical current of a 4 mu m width YBCO junction tallied with the prior simulated Fraunhofer diffraction pattern of a Josephson junction with a spatially homogeneous critical current density, The maximum peak-to-peak modulation voltage across the dc superconducting quantum interference device (SQUID) fabricated by using these junctions reached up to 32 mu V at 77 K. The magnetic modulation of the SQUID exhibited periodic behavior with the observed modulation period of 5.0 X 10(-4) G. (C) 1997 American Institute of Physics.