  Here we report a novel nitridation technique for transforming niobium into
hexagonal Nb2N which appears to be superconducting below 1K. The nitridation is
achieved by high temperature annealing of Nb films grown on Si3N4/Si (100)
substrate under high vacuum. The structural characterization directs the
formation of a majority Nb2N phase while the morphology shows granular nature
of the films. The temperature dependent resistance measurements reveal a wide
metal-to-superconductor transition featuring two distinct transition regions.
The region close to the normal state varies strongly with the film thickness,
whereas, the second region in the vicinity of the superconducting state remains
almost unaltered but exhibiting resistive tailing. The current-voltage
characteristics also display wide transition embedded with intermediate
resistive states originated by phase slip lines. The transition width in
current and the number of resistive steps depend on film thickness and they
both increase with decrease in thickness. The broadening in transition width is
explained by progressive establishment of superconductivity through proximity
coupled superconducting nano-grains while finite size effects and quantum
fluctuation may lead to the resistive tailing. Finally, by comparing with Nb
control samples, we emphasize that Nb2N offers unconventional superconductivity
with promises in the field of phase slip based device applications.
