Nano-sculptured Janus-like TiAg thin films obliquely deposited by GLAD co-sputtering for temperature sensing

Abstract

Inclined, zigzag and spiral TiAg films were prepared by glancing angle co-deposition, using two distinct Ti and Ag targets with a particle incident angle of 80 degrees and Ag contents ranging from 20 to 75 at%. The effect of increasing Ag incorporation and columnar architecture change on the morphological, structural and electrical properties of the films was investigated. It is shown that inclined columnar features (beta = 47 degrees) with high porosity were obtained for 20 at% Ag, with the column angle sharply decreasing (beta = 21 degrees) for 50 at% Ag, and steeply increasing afterwards until beta = 37 degrees for the film with 75 at% Ag. The sputtered films exhibit a rather well-crystallized structure for Ag contents >= 50 at%, with a TiAg (111) preferential growth. No significant oxidation was detected in all films, except for the one with 20 at% Ag, after two 298-473-298 K temperature cycles in air. The calculated temperature coefficient of resistivity (TCR) values vary between 1.4 and 5.5 x 10(-4)K(-1). Nano-sculptured spiral films exhibit consistently higher resistivity (rho = 1.5. x 10(-6) Omega m) and TCR values (2.9 x 10(-4)K(-1)) than the inclined one with the same Ag content (rho = 1.2 x 10(-6) Omega m and TCR = 2.0 x 10(-4)K(-1)). No significant changes are observed in the zigzag films concerning these properties. The effective anisotropy A(eff) at 473 K changes from 1.3 to 1.7 for the inclined films. Spiral films exhibit an almost completely isotropic behavior with A(eff) = 1.1. Ag-rich TiAg core + shell Janus-like columns were obtained with increasing Ag concentrations.