Studies of Superconducting Thin Film Carbides and Nitrides

Abstract : Thin films of niobium nitride prepared by reactive sputtering have an excellent combination of superconducting characteristics. A major problem in using these nitrides has been the varied and often contradictory descriptions of how to prepare the films to obtain a desired set of superconducting properties. The problem of consistency and transferability of results can be partially resolved if one pays attention to the structure and composition of the films and not necessarily to the mechanics of sputtering. In this study the authors attempted to vary the sputtering conditions and correlate the superconducting properties of NbN and related alloys with the film's composition and structure. It is found that relatively small changes in sputtering conditions often resulted in large changes in superconducting properties. In every case the results can be explained when film structure and composition were characterized. The study included the nitrides and carbides of niobium and tantalum. Both d. c. and a. c. sputtering techniques were used.