Synthesis and superconducting properties of niobium nitride nanowires and nanoribbons

Superconducting niobium nitride wires and ribbons with transverse dimensions down to tens of nanometers were synthesized by annealing Nb Se3 nanostructure precursors in flowing ammonia gas at temperatures up to 1000 °C. Their critical temperatures increase with increasing annealing temperatures and reach 9-11.2 K when sintered at 950 °C or above. X-ray diffraction analyses identified Nb4 N5 and Nb5 N6 phases, dominating at annealing temperatures below and above 950 °C, respectively. Transport measurements show magnetoresistance oscillations at temperatures near the superconducting transition due to vortex-row confinement effects and voltage jumps in current-voltage characteristics at low temperatures attributed to hot-spot behavior.