Influence of the Ag Content on the Natural and Thermal Induced Oxidation of Cu Thin Films

In this paper, we studied the deposition and characterization of monolithic and silver-doped copper coatings using RF magnetron sputtering. The main objective was to examine the impact of different Ag contents on natural and thermally induced aging when compared with monolithic copper coatings. For this purpose, the as-deposited surfaces were left exposed to normal temperature and humidity conditions during one year (natural) and were annealed at 200 °C in a non-controlled atmosphere. To evaluate the results of these treatments, the films were characterized in terms of surface and cross-section morphology, structure, chemical composition, wettability, and surface energy. The as-deposited monolithic copper films exhibit a clear face-centered cubic structure with a very strong preferential crystallographic orientation according to the (111) diffraction plane. The presence of Ag in the as-deposited coatings decreased the ability of the films to be wetted, increasing their hydrophobicity and jeopardizing crystallographic orientation development according to the (111)-Cu diffraction plane, particularly after annealing, when compared to Cu films. Through annealing, Cu₂O and Ag₂O were formed, leading to a significant decrease in surface energy and reduced wettability. These results can help elucidate and estimate the life span of smart windows, batteries, and solar panels, which are some of the many applications for these coatings.