Properties of (Nb-0.35, Ti-0.15)(x)Ni1-x thin films deposited on silicon wafers at ambient substrate temperature

We have studied the properties of (Nb-0.35, Ti-0.15)(x)N1-x films deposited by reactive magnetron sputtering at ambient substrate temperature, focusin g in particular on the dependence of film properties on the total sputterin g pressure. As the pressure increases we observe a transition in the film s tructure from the ZT to the Z1 structural zone according to the Thornton cl assification. In general, the superconducting transition temperature (T-c) and residual resistance ratio have a very moderate dependence on total sput tering pressure, while the film resistivity increases an order of magnitude as the sputtering pressure increases. A wide spectrum of material science techniques is used to characterize the films and to explain the relationshi p between the sputtering conditions and film properties. Transmission elect ron microscopy and x-ray diffraction analysis show that 160-nm-thick (Nb-0. 35, Ti-0.15)(x)N1-x films consist of 20-40 nm grains with good crystallinit y. Films sputtered under low pressures have a weak [100] texture, while fil ms sputtered under high pressures have a distinct [111] texture. A stable c hemical composition and reduction in film density as the sputtering pressur e increases indicate that the change of resistivity in the ZT structural zo ne is due to a variation in the quenched-in vacancy concentration. In contr ast voids on the grain boundaries and vacancies together produce the high f ilm resistivities in the Z1 structural zone. (C) 2000 American Institute of Physics. [S0021-8979(00)02723-7].