Superconductive tunneling into NbN deposited near room temperature

Abstract

We have developed the ability to deposit niobium nitride thin films routinely having a superconducting transition temperature of 14 K by dc reactive magnetron sputtering onto substrates held near room temperature (Ts <90 °C). This allows the use of conventional photoresist liftoff techniques for patterning. Pb-counterelectrode tunnel junctions formed on these films show excellent V-I characteristics, suitable for device applications and offering potential advantages over conventional Pb-alloy/Pb-alloy and Nb/Pb-alloy junctions. These high quality junctions are also suitable for tunneling investigations of superconductivity in the Nb-N system.