Low-temperature electrical resistivity in obliquely co-deposited Cr–Ta, Cr–Hf, and Ti–W thin films

Cr–Ta, Cr–Hf and Ti–W thin films were fabricated by glancing angle co-sputtering. Two single metallic targets (A = Cr or Ti and B = Ta or Hf or W) were inclined with an angle of 80° with respect to the substrate normal. This configuration enabled simultaneous sputtering of both targets with an independent and reverse controlled of each target current from 0 to 300 mA. Atomic concentrations of these bi-component films were adjusted from A-rich to B-rich compounds. Some co-sputtering conditions led to equiatomic A and B films with tunable tilted columnar structures: From oriented columns facing A or B target, through perpendicular growth to the substrate surface. X-ray diffraction analyses showed a poorly crystalline structure with a mixture of metallic phases for similar target currents. DC electrical resistivity measured from 7 to 300 K exhibited a typical metallic-like behavior for Cr–Ta and Ti–W films, whatever the structure and composition, whereas Hf-rich films produced negative temperature coefficients of resistance. A rule of mixtures was proposed for electrical resistivity measured at room temperature, and Debye temperatures of Cr–Ta and Cr–Hf films were calculated and well estimated as a function of the composition assuming the cross-over temperature obtained from electron-defect to electron-phonon scattering regimes.