Characterization of NbTiN thin films prepared by reactive DC-magnetron sputtering

Niobium-titanium-nitride (NbTiN) thin films were prepared on quartz substrates by reactive dc-magnetron sputtering with a NbTi alloy target, and their properties, were studied systematically. Properties of the thin films, such as superconducting transition temperature were strongly dependent on variation of cathode voltage, /spl Delta/U, which is induced when a small fraction of N/sub 2/ is added to Ar during sputter discharge. High quality thin films with transition temperature as high as 15 K and resistivity of /spl sim/100 /spl mu//spl Omega/cm have been obtained at around /spl Delta/U=28 V with a total gas pressure of 0.9 Pa. Since gap frequency calculated from the measured critical temperature of 15 K based on BCS theory is about 1.1 THz, these NbTiN thin films are good candidates for wiring layers of SIS mixers as well as SIS junctions in the 1 THz band.