Low temperature dependence of electrical resistivity in obliquely sputter-deposited transition metal thin films

Abstract

Transition metals exhibiting hcp (Ti, Zr, Hf) and bcc (V, Nb, Ta, Cr, Mo, W) crystalline structures are DC sputter-deposited by oblique angle deposition. A constant film thickness of 400 nm is prepared, whereas the deposition angle α is systematically changed from 0 to 85° A columnar structure is produced with column angle reaching β = 50° for the highest deposition angle. Crystallinity and grain size are both reduced with an increasing deposition angle, especially for α higher than 60° DC electrical resistivity vs. temperature in the range 7–300 K shows a typical metallic-like behavior with films becoming more resistive for high deposition angles. For temperatures higher than 100 K, the linear temperature dependence of resistivity is obtained for films prepared with deposition angles lower than 60° The electron-phonon is the main interaction acting on electronic transport mechanism. Oblique deposition angles give rise to an enhancement of electron-phonon interactions with a saturation effect of electrical resistivity for some metals. Resistivity measurements at low temperatures (down to 7 K) show the predominance of electron-defect interactions. Electron-phonon-defect interaction effect is particularly investigated as a function of the deposition angle and a shift of the crossover temperature is brought to the fore.