Influence of the sputtering pressure on the morphological features and electrical resistivity anisotropy of nanostructured titanium films

Abstract

Titanium films were DC sputtered with a particle flux incidence angle of 80°, using the Glancing Angle Deposition (GLAD) technique with increasing sputtering pressures from 0.2 to 1.5Pa. This range of pressures is typically implemented for the deposition of thin films by the magnetron sputtering process. The main objective of this work was to study the anisotropic electrical resistivity behaviour of the different thin film nanostructures that were obtained. It is shown that low sputtering pressures (0.2–0.5Pa) promote higher column angles β with respect to the substrate normal (15°≤β≤40°), as well as better defined porous structures. On the other hand, intermediate and high pressures (0.6-0.8Pa) originate secondary growth effects on the columnar structures perpendicular to the substrate normal (β=0°). No defined columns can be seen when the films are sputtered using the highest pressure (1.5Pa). The electrical resistivity is significantly affected by the differences in the columnar microstructure. Porous films exhibit higher room temperature (RT) resistivity values (0.95–1.5×10−5Ωm), when compared to the more compact ones (0.6–0.9×10−5Ωm). When a temperature cycle of RT(25)-300-RT(25)°C was applied, a more significant oxidation is evidenced in the more porous structures, as well as a higher resistivity anisotropy (maximum of 1.6) than in the more compact ones (minimum of 1.25).