NbN/TaNx/NbN SNS Josephson junctions by pulsed laser deposition

We have made NbN/TaN_x/NbN Josephson junctions with nonhysteretic I-V characteristics that may have potential application for single-flux-quantum logic or SQUID magnetometers. The trilayer growth was done in-situ using pulsed laser deposition. The resistivity of the TaN_x was varied by the N₂ pressure during growth from a few hundred micro-ohm-cm at low pressure to a few hundred milli-ohm-cm at pressures up to 300 mTorr. The films were characterized using Rutherford backscattering, X-ray diffraction, and atomic force microscopy. Junction processing was done in the usual trilayer technology. The fabricated Josephson junctions show I_cR_n values >0.3 mV at 4.2 K. We also observed that at a high laser fluence, NbN films with low a real particulate density and T_c~16.2 K could be grown on 25°C substrates