Superconducting niobium nitride thin films by reactive pulsed laser deposition

Abstract The structural, electronic, and nanomechanical properties of cubic niobium nitride thin films were investigated. The films were deposited on Si(100) under different background nitrogen gas pressures (26.7-66.7 Pa) at constant substrate temperature of 800 °C by reactive pulsed laser deposition. Our results reveal that the NbN x films exhibit a cubic δ-NbN with strong (111) orientation and highly-oriented textured structures. We find nitrogen background pressure to be an important factor in determining the structure of the NbN x films. The dependence of the electronic structure as well as that of the superconducting transition temperature ( T c ) on the nitrogen gas background pressure is studied. A correlation between surface morphology, electronic and superconducting properties is found for the deposited NbN x thin films. The highly-textured δ-NbN films have a T c up to 15.07 K. Nanoindentation with continuous stiffness method is used to evaluate the hardness and modulus of the NbN x thin films as a function of depth. The film deposited at nitrogen background pressure of 66.7 Pa exhibits improved superconducting properties and shows higher hardness values as compared to films deposited at lower nitrogen pressures.