AVS 50th International Symposium
    Surface Science Wednesday Sessions
       Session SS-WeP

Paper SS-WeP15
Photoemission Study of the Oxidation of Cu{111} with Hyperthermal O@sub 2@ Molecular Beam

Wednesday, November 5, 2003, 11:00 am, Room Hall A-C

Session: Poster Session
Presenter: K. Moritani, Japan Atomic Energy Research Institute
Authors: K. Moritani, Japan Atomic Energy Research Institute
M. Okada, Osaka University, Japan
S. Sato, Osaka University, Japan
S. Goto, Osaka University, Japan
T. Kasai, Osaka University, Japan
A. Yoshigoe, Japan Atomic Energy Research Institute
Y. Teraoka, Japan Atomic Energy Research Institute
Correspondent: Click to Email
The oxidation of Cu has been of great interest because of the important role of Cu oxides in material science, for example, high T@sub c@ superconductors of cuprates and solar cells. Thus, many experimental and theoretical studies have been performed to understand the oxidation of Cu. However, the oxide-formation processes have been little elucidated from the kinetics and dynamics points of view. In the present work, we studied the oxidation of Cu{111} with a hyperthermal O@sub 2@ molecular beam (HOMB) using X-ray photoemission spectroscopy (XPS) in conjunction with a synchrotron radiation (SR) source. All experiments were performed with the surface reaction analysis apparatus (SUREAC 2000) constructed in BL23SU at SPring-8. The kinetic energy of incident O@sub 2@ can be controlled by changing the O@sub 2@, He and/or Ar gas mixing ratios with the nozzle temperature kept at 1400 K. The incident direction of the HOMB is along the surface normal of the sample kept at 300 K. After the irradiation of a proper amount of HOMB, high-resolution XPS spectra were measured at 300 K using SR. We measured O-uptake curves, determined from the integration of O-1s XPS spectra, in the 2.3- and 0.6-eV HOMB irradiation on the Cu{111} surface. The efficiency of oxidation with HOMB is higher than that with ambient thermal O@sub 2@ gas. The kinetics of the dissociative adsorption in the HOMB incidence can be described well using a Langmuir-type adsorption model under @theta@ @<=@ 0.5 ML. On the other hand, further oxidation occurs rather inefficiently under @theta@ @>=@ 0.5 ML even for the 2.3-eV-HOMB irradiation. We found that such slow oxidation process of Cu can be interpreted in terms of a collision-induced-adsorption mechanism. We will discuss possible models of oxidation process of Cu based on the incident-energy dependence of the O-uptake curve.