Effects of the Ta content on the microstructure and electrical property of reactively sputtered TaxZr1−xN thin films

The TaxZr1−xN films were prepared by reactive magnetron sputtering and the concentration of zirconium and tantalum was regulated by controlling the power to the sputtering guns. The effects of the Ta content on the microstructure, composition and electrical properties of TaxZr1−xN films were investigated by x-ray diffraction, field-emission electron probe micro-analyzer, atomic force microscopy, x-ray photoelectron spectroscopy, four point probe and Hall-effect measurements. Results indicated that the TaxZr1−xN films with different Ta contents were crystallized in NaCl-type structure. However, the lattice constant of TaxZr1−xN films decreased with the increase of the Ta content due to the smaller ionic radius of Ta5+ comparing with that of Zr4+. The decreasing lattice constant of TaxZr1−xN films with the Ta content evidenced the successful substitution of Zr with Ta. The electrical resistivity of TaxZr1−xN films showed a minimum value of 78 μΩ cm at Ta content of 3.5 at.% and then increased with the increase of Ta content. Hall measurements indicated that the electrical conduction of films was essentially due to electrons (n-type). And the increase of carrier density and mobility at a Ta content of 3.5 at.%, caused by the extra d valence electron of Ta and the less electron scattering of grain boundaries, was responsible for the further decreasing of resistivity from pure ZrNx films.