NbN Films Prepared by Magnetron Sputtering

NbN films on sapphire or copper substrates have been prepared by magnetron sputtering in argon-nitrogen atmospheres. The highest transition temperature, T c =15.7 K, was achieved with a film sputtered on a sapphire substrate at a substrate temperature T s =800°C and a partial nitrogen pressure P N 2 =5×10 -3 Torr. Uniform films with transition width narrower than 0.4 K were prepared with good reproducibility by this method. A short NbN tape of metallic luster stripped off from the copper substrate still showed a T c of ∼15 K even after being bent to a radius of curvature as small as 6 mm. These results indicate that magnetron sputtering is useful for preparing NbN films and long NbN tapes.