Metal-to-Dielectric transition induced by annealing of oriented titanium thin films

Abstract

Titanium thin films were deposited by DC magnetron sputtering. The glancing angle deposition (GLAD) method was implemented to prepare two series of titanium films: perpendicular and oriented columnar structures. The first series was obtained with a conventional incident angle α of the sputtered particles (α = 0°), whereas the second one used a grazing incident angle α = 85°. Afterwards, the films were annealed in air using six cycles of temperature ranging from 293 K to 773 K. DC electrical conductivity was measured during the annealing treatment. Films deposited by conventional sputtering (α = 0°) kept a typical metallic-like behavior versus temperature (σ300 K = 2.0 × 10^6 S m-1 and TCR293 K = 1.52 × 10^-3 K-1), whereas those sputtered with α = 85° showed a gradual transition from metal to dielectric. Such a transition was mainly attributed to the high porous structure, which favors the oxidation of titanium films to tend to the TiO2 compound.