Comparative studies of ion-implant Josephson-effect structures

We have investigated Josephson-effect structures formed by Cu or Fe implant of localized regions in Ta films and have compared their properties to those of other types of proximity-effect bridges. Properties investigated include coherence length, penetration depth, critical current versus temperature, critical current versus magnetic field, and rf response. We find no significant differences between the various types of bridges, provided a material-dependent scaling factor is applied to the bridge length.