Active oxidation of CuAu(110) using hyperthermal O molecular beam

Okada, Michio*; Teraoka, Yuden

Oxidation of CuAu(110) using a hyperthermal O molecular beam (HOMB) was investigated by synchrotron X-ray photoemission spectroscopy. From the incident energy dependence of the O-uptake curve, the precursor-mediated dissociative adsorption occurs, where the trapped O molecule can migrate and dissociate at the lower activation-barrier sites. Dissociative adsorption of O on CuAu(110) is as effective at the thermal O exposure as on Cu(110). On the other hand, at the incident energies of HOMB where the direct dissociative adsorption is dominant, the dissociative adsorption of O takes place with a higher activation barrier and less reactivity due to Au alloying comparing to the HOMB oxidation of Cu(110). The dissociative adsorption progresses with the Cu segregation on CuAu(110) similarly as on CuAu(100). The growth of CuO for 2 eV HOMB suggests that the diffusion of Cu also contribute to the oxidation.