Deposition angle tunes low-temperature electronic transport in early transition metal thin films

Nine transition metals, namely, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W, are DC sputter-deposited by oblique angle deposition (OAD). The deposition angle α is gradually changed from 0 to 85° while keeping the films thickness at 400 nm. The electronic transport properties of these metallic nanocolumnar thin films are investigated by means of resistivity vs. temperature measurements from 7 to 300 K. Electron scattering phenomena by phonons, defects and electrons strongly depend on the nature of deposited metal, and deposition angle. Temperature-dependent models are applied as a function of the different electron interaction mechanisms. It is shown that the conventional Bloch-Grüneisen theory of bulk metals well explain the electronic transport properties of hcp metals. However, it cannot fit with the various evolutions of resistivity vs. temperature measurements of bcc thin films. A saturation effect in resistivity occurs for bcc metals when they are fabricated with the most glancing deposition angles (α > 70°). A more complex behavior is also obtained for chromium thin films, which clearly illustrates the significant deviation from the Matthiessen’s rule due to the increasing number of growth-induced defects and voids favored by the OAD process.