摘要
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•Cu diffusion and O2 induced initial oxidation mechanism are compared and discussed.•Surface diffusion was stalled at the twin boundary due to high activation energy.•The stalled diffusion at concave junction modulates the surface step density.•Step-mediated oxidation behavior facilitates the conformal Cu oxidation.
Metal oxidation has long been an interesting and important research topic because it strongly impacts the electrical and mechanical properties of metals. Copper typically lacks the self-limiting oxidation characteristics observed in aluminum, chromium, and titanium. Nevertheless, Cu nanowires with dense coherent twin boundaries (CTBs) exhibit superior stability against further oxidation by forming a conformal thin surface oxide layer. This study reports an experimental and theoretical investigation of the unusual self-limiting oxidation behavior of nanotwinned Cu (nt-Cu) nanowires. The results indicate that CTB-intersected surface junctions decrease atomic step density and minimize oxide nuclei populations on nt-Cu surfaces. A two-dimensional oxide growth is suggested due to the reduced activity of Cu adatoms detaching from the concave CTB-intersected junctions. Consequently, the underlying nt-Cu nanowire is protected from further oxidation by a thin and conformal oxide layer.