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

Abstract

We have grown superconducting NbN films using a pulsed KrF laser for potential use as superconducting electrodes in SNS Josephson junctions being developed for nonlatching logic applications. The NbN films show a superconducting transition of 16 K using an Nb target in background N2 gas. The Tc dependence on N2 pressure in the range of 50-­80 mTorr was investigated at a growth temperature of 600 °C. The NbN films were grown on MgO(100) and amorphous SiNx/Si substrates. In the latter case, the films had a lower Tc, and appeared amorphous from x­ray diffraction measurements, while those on the MgO(100) substrates were strongly textured. AFM measurements reveal RMS surface roughness as low as 1 nm, over a 5 µm × 5 µm area, indicating that these films appear suitable for SNS junctions.