Superconducting NbN films grown using pulsed laser deposition for potential application in internally shunted Josephson junctions

We have grown superconducting NbN films using a pulsed KrF laser for potent ial use as superconducting electrodes in SNS Josephson junctions being deve loped for nonlatching logic applications. The NbN films show a superconduct ing transition of 16 K using an Nb target in background N-2 gas. The T-c de pendence on N-2 pressure in the range of 50-80 mTorr was investigated at a growth temperature of 600 degrees C. The NbN films were grown on MgO(100) a nd amorphous SiNx/Si substrates. In the latter case, the films had a lower T-c, and appeared amorphous from x-ray diffraction measurements, while thos e on the MgO(100) substrates were strongly textured. AFM measurements revea l RMS surface roughness as low as 1 nm, over a 5 mu m x 5 mu m area, indica ting that these films appear suitable for SNS junctions.