Properties of NbN films crystallized from the amorphous state

Cubic Bl structure NbN was prepared by annealing amorphous Nb-N films made by sputtering niobium in an argon-nitrogen atmosphere onto low temperature ( C) substrates. Crystallized films on sapphire substrates have equiaxed grains while films on niobium are columnar. Grain sizes vary from 12.5 nm to > 100 nm. The highest superconducting critical properties measured in these films are: Tc= 16K, Jc(4.2K, zero field) = 8 × 10⁵A/cm², and Bc2(1.3K) = 28T. Data on the effect of uniaxial tensile strain on Jcshow that there is no measurable elastic (reversible) strain effect. Irreversible Jcdegradation begins at an intrinsic tensile strain of 1.3% in the best case.