Initial stages of Cu sub(3)Au(111) oxidation: oxygen induced Cu segregation and the protective Au layer profile

• Published in: Physical chemistry chemical physics : PCCP Vol. 16; no. 8; pp. 3815 - 3822
• Main Authors: Tsuda, Yasutaka, Oka, Kohei, Makino, Takamasa, Okada, Michio, Dino, Wilson Agerico, Hashinokuchi, M, Yoshigoe, Akitaka, Teraoka, Yuden, Kasai, Hideaki
• Format: Journal Article
• Language: English
• Published: 01.01.2014
• Subjects: Copper; Density functional theory; Enrichment; Gold; Oxidation; Protective; Segregations; X-ray photoelectron spectroscopy
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c3cp54709d

We report results of our experimental and theoretical studies on the Au concentration profile of Cu sub(3)Au(111) during oxidation by a hyperthermal O sub(2) molecular beam at room temperature, using X-ray photoemission spectroscopy (XPS), in conjunction with synchrotron radiation (SR), and density functional theory (DFT). Before O sub(2) exposure, we observe strong Au segregation to the top layer, i.e., Au surface enrichment of the clean surface. We also observe a gradual Cu surface enrichment, and Au enrichment of the second and third (subsurface) layers, with increasing O coverage. Complete Cu segregation to the surface occurs at 0.5 ML O surface coverage. The Au-rich second and third layers of the oxidized surface demonstrate the protective layer formation against oxidation deeper into the bulk.