Effects of oxygen on the resistivity in Au thin films with Ti-Al adhesion layer

In this paper, the authors present a characterization study of a nonstoichiometric adhesion layer composed of a Ti-Al alloy (⁠$55%$ Ti, $45%$ Al) studied for the first-time for the interface of Au/Si and Au/glass. The system was deposited by DC magnetron sputtering on both substrates, and the Au/Ti-Al performance was assessed by surface roughness, stoichiometry, and electrical resistivity measurements. A four-point probe technique was used to acquire the resistivity value (⁠$ρ∼3.5×10−8$ $Ω$ m) at room temperature, showing high conductivity. The thickness of the system was estimated with Rutherford backscattering spectrometry and the in-depth chemical composition with glow-discharge optical emission spectroscopy. The set of results was compared with other known adhesion layers in the literature, such as Ti, Cr, and Al. It was found that a suitable combination of electronegativity, number of valence electrons, and low intermixing with Au top layer causes Ti-Al to oxidize less than Ti and Cr without decreasing the Au conductivity. These properties confirm that the Au/Ti-Al system could be useful for application in electronics, especially for dry electrodes, due to its excellent conductivity, low oxidation, and, hence, good durability.