Ab initio studies of pristine and oxidized Cu3Au(100) and (111) surfaces

Phys. Chem. Chem. Phys.

Makino

et al. 2014

We report results of our experimental and theoretical studies on the Au concentration profile of Cu3Au(111) during oxidation by a hyperthermal O2 molecular beam at room temperature, using X-ray photoemission spectroscopy (XPS), in conjunction with synchrotron radiation (SR), and density functional theory (DFT). Before O2 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.

supporting

confidence: 91%

Initial stages of Cu3Au(111) oxidation: oxygen induced Cu segregation and the protective Au layer profile

Phys. Chem. Chem. Phys.

Makino

et al. 2014

“…Copper (Cu) and gold (Au) form model binary metallic systems 1 2 3 4 5 6 with stable L 1 0 (CuAu) and L 1 2 (Cu 3 Au and Au 3 Cu) structures. Experimental studies report surface segregation of Au in Cu-Au alloys 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 . More recently, extensive studies 4 10 11 12 13 14 15 16 17 18 19 22 23 on the oxidation of Cu 3 Au surfaces found Au-rich top-most layers of Cu 3 Au(100), (110), and (111) surfaces.…”

mentioning

confidence: 99%

“…Experimental studies report surface segregation of Au in Cu-Au alloys 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 . More recently, extensive studies 4 10 11 12 13 14 15 16 17 18 19 22 23 on the oxidation of Cu 3 Au surfaces found Au-rich top-most layers of Cu 3 Au(100), (110), and (111) surfaces. Oxidation, which is one of the more important corrosion process, induces changes in segregation 10 11 12 13 14 15 16 17 18 22 23 24 25 26 .…”

mentioning

confidence: 99%

“…More recently, extensive studies 4 10 11 12 13 14 15 16 17 18 19 22 23 on the oxidation of Cu 3 Au surfaces found Au-rich top-most layers of Cu 3 Au(100), (110), and (111) surfaces. Oxidation, which is one of the more important corrosion process, induces changes in segregation 10 11 12 13 14 15 16 17 18 22 23 24 25 26 . Studies have been done to induce Cu segregation to the surface by dissociatively adsorbing energetic O 2 10 11 12 13 22 23 .…”

mentioning

confidence: 99%

See 1 more Smart Citation

Experimental and Theoretical Studies on Oxidation of Cu-Au Alloy Surfaces: Effect of Bulk Au Concentration

Okada

et al. 2016

Sci Rep

We report results of our experimental and theoretical studies on the oxidation of Cu-Au alloy surfaces, viz., Cu3Au(111), CuAu(111), and Au3Cu(111), using hyperthermal O2 molecular beam (HOMB). We observed strong Au segregation to the top layer of the corresponding clean (111) surfaces. This forms a protective layer that hinders further oxidation into the bulk. The higher the concentration of Au in the protective layer formed, the higher the protective efficacy. As a result, of the three Cu-Au surfaces studied, Au3Cu(111) is the most stable against dissociative adsorption of O2, even with HOMB. We also found that this protective property breaks down for oxidations occurring at temperatures above 300 K.

“…The phenomena, like O-induced Cu segregation on Cu 3 Au(111), have been reported. [22][23][24] Here, we report results of our detailed studies on the reactivity of O and O diffusion into the bulk for the initial oxidation process of Cu 3 Au(111) with a HOMB with variable incident energy, in order to confirm the protective nature against oxidation. From the O uptake curves determined from the O-1s X-ray photoemission spectroscopy (XPS) measurements in conjunction with synchrotron radiation (SR), it was found that the dissociative adsorption of a 2.3 eV HOMB is less efficient on Cu 3 Au(111) than on Cu(111).…”

Section: Introductionmentioning

confidence: 99%

The effects of alloying and segregation for the reactivity and diffusion of oxygen on Cu₃Au(111)

Phys. Chem. Chem. Phys.

Makino

et al. 2014

We report results of the segregation induced by the adsorption of O2 and the barrier of the formation of Cu2O in Cu3Au(111) with an experimental and theoretical approach. Oxidation by a hyperthermal O2 molecular beam (HOMB) was investigated by X-ray photoemission spectroscopy in conjunction with a synchrotron light source. From the incident-energy dependence of the measured O-uptake curve, dissociative adsorption of O2 is less effective on Cu3Au(111) than on Cu(111). The dissociative adsorption is accompanied by the Cu segregation on Cu3Au(111) as well as on Cu3Au(100) and Cu3Au(110). The obvious growth of Cu2O for a 2.3 eV HOMB cannot be observed and it suggests that the Au-rich protective layers prevent the diffusion of O atoms into the bulk. The theoretical approach based on density functional theory indicates that O adsorption shows the same behavior on Cu3Au(111) and on Cu(111). For the diffusion case, the barrier to diffuse into the subsurface in segregated Cu3Au(111) is higher than in Cu(111). This indicates that the segregated Au-rich layer in Cu3Au(111) works as a protective layer.