REACTIVE DIFFUSION PRODUCED NIOBIUM NITRIDE FILMS FOR SUPERCONDUCTING CAVITY APPLICATIONS

In view of their potential interest for the construction of radiofrequency (RF) superconducting accelerating cavities, films of NbN have been produced by annealing Nb samples in a nitrogen atmosphere. These films have been characterized by critical temperature measurements performed with the magnetic permeation method, by metallographic examination and by X-ray diffraction. They exhibit critical temperatures up to 16.6 K, and transition widths of about 0.4 K. The influence of nitriding conditions (temperature, nitrogen pressure and time) on the superconducting properties has been investigated, in order to obtain the optimal nitriding parameters.