Niboium-titanium nitride thin films for superconducting rf accelerator cavities

The development of sputtering-magnetron techniques makes possible the manufacturing of thin-film coated rf cavities for high-energy accelerators of various superconducting alloys or compounds. In this context high-quality (Nb1-xTix)N films have been produced by dc magnetron sputtering and carefully characterized. These films, for x≤0.5, exhibit a critical temperature Tc as high as NbN (Tc=17 K) but show a markedly lower normal state resistivity. The calculated BCS surface impedance of the films is also lower than for NbN. The overall properties of the (Nb1-xTix)N films are compared with those of other superconductors, and the suitability of this material for the production of superconducting sputter-coated copper cavities for particle physics accelerators is demonstrated. The potential interest of (Nb1-xTix)N films for superconducting electronics is also briefly outlined. © 1990 Plenum Publishing Corporation.