Protective layer formation during oxidation of Cu3Au(100) using hyperthermal O2 molecular beam

Abstract

Oxidation of Cu3Au(100) using 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 O-uptake curve, it was determined that the dissociative adsorption of O2 implies a higher activation barrier and therefore less reactivity compared to Cu, owing to the Au alloying. The dissociative adsorption progresses with the Cu segregation on the surface. No prominent growth of Cu2O even for 2eV HOMB suggests that the Au alloying of Cu can serve as a protective layer against further oxidation into the bulk.

Photoemission study on natural oxidation of Cu3Au with synchrotron radiation

“…Thus, we similarly consider that in naturally oxidized Cu 3 Au(110), the Au atoms move below the relatively thick Cu oxide layers. It was also found that in the oxidation of Cu 3 Au(100) with HOMB in a vacuum, subsurface Au atoms prevent O atoms from diffusing farther into bulk and limit the oxidation to the topmost layer [10,11]. Thus, we consider that in natural oxidation, the Au atoms below the Cu-oxide layers reduce the diffusion of O atoms farther into bulk and keep the oxide layers from growing beyond some limit.…”

“…The binding energies (E B ) of the components for Au-4f 5/2 were 88.3 and 87.7 eV, while those for Au-4f 7/2 were 84.6 and 84.0 eV. The higher and the lower E B components in each peak correspond to bulk Au and surface Au atoms, respectively, in the spectrum obtained from the clean surface [10,11]. The Au surface peak suggests the existence of Au atoms on the topmost layer and supports the structural model of Ref.…”

Supersonic Molecular Beam Experiments on Surface Chemical Reactions

“…[40,[48][49][50][51][52][53] In the hyperthermal energy region, we also expect the efficient collision-induced processes proposed by Ceyer. [47] Collisioninduced absorption (CIA) [43,54] and local heating of the substrate [55] were indeed shown to be effective for inducing oxide nucleation, opening up new possibilities for the production of nanostructured metal oxides. The energy transfer from hyperthermal beams can also be applied to the measurement of the friction coefficients of the adsorbed molecular motions.…”

“…Rec the XPS measurements of the core levels of O, Cu and Au. [55,67] Moreover, this O-induced structure of Cu3Au(100) was also produced with an ion beam. [68] With respect to Cu(100) (see also the uptake curve reported in Figure 6 for comparison), dissociative adsorption on Cu3Au(100) has a higher activation barrier.…”

Study on Oxidation of Cu and Cu3Au Surfaces with Hyperthermal Oxygen Molecular Beam

“…[7,8]. The uptake curve on Cu (100) for 2.3 eV HOMB incidence (open squares) is shown for comparison.…”