NbN tunnel junctions

The selective niobium nitride overlap process for the fabrication of all-niobium nitride Josephson junction involves trilayer deposition over the entire wafer before a selective patterning of the electrodes by means of optically controlled dry reactive ion etching. An analysis of the properties of NbN films deposited by DC magnetron sputtering, followed by surface oxide growth, shows that the earliest stage of NbN counterelectrode growth is critical for the production of high quality, high gap value junctions.