Abstract
The oxidation of Au/Ag alloy thin films using radio-frequency oxygen plasma was studied in this work. It was demonstrated that there is a phase separation occurring between silver and gold. In addition, it was shown that the preferential oxidation of silver resulted in a solid-state diffusion of silver toward the surface where it oxidized and formed nanoporous microspheres. The gold phase remaining in the film exhibited nanoporosity due to the injected vacancies at the metal/silver oxide interface. Based on the scanning transmission electron microscopy analysis coupled with energy dispersive X-ray mapping a mechanism was proposed based on solid-state diffusion and the Kirkendall effect to explain the different steps occurring during the oxidation process.
Highlights
Silver corrosion upon exposure to atomic oxygen is a phenomenon that was highly studied in the 1980s
Silver degradation related to this phenomenon was attributed to the strong chemical reaction between silver and atomic oxygen present in the low earth orbit (LEO) resulting in the transformation of the metallic silver into highly stressed and nanoporous silver oxide [1,2]
By using elemental energy dispersive X-ray (EDS) analysis, these microspheres were confirmed to be constituted of silver oxide
Summary
Silver corrosion upon exposure to atomic oxygen is a phenomenon that was highly studied in the 1980s. Instead of using nanostructures as before, we used Au/Ag alloy thin films deposited by co-sputtering as the model system to study the oxidation process triggered by radiofrequency oxygen plasma (Figure 1). The oxidation and phase separation processes resulted in the formation of unique features, consisting of silver oxide nanoporous microspheres (Figure 1).
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