AVS 51st International Symposium
    Surface Science Tuesday Sessions
       Session SS-TuP

Paper SS-TuP43
Kinetic Energy Dependent Oxidation Processes on Copper Surfaces

Tuesday, November 16, 2004, 4:00 pm, Room Exhibit Hall B

Session: Poster Session
Presenter: K. Moritani, Japan Atomic Energy Research Institute, Japan
Authors: K. Moritani, Japan Atomic Energy Research Institute, Japan
M. Okada, Osaka University, Japan
A. Yoshigoe, Japan Atomic Energy Research Institute, Japan
Y. Teraoka, Japan Atomic Energy Research Institute, Japan
T. Kasai, Osaka University, Japan
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 Tc 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 kinetics and dynamics points of view. In the present work, we studied the oxidation of Cu surfaces with a hyperthermal O@sub 2@ molecular beam (HOMB) using high-resolution 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 and the nozzle temperature. The incident direction of the HOMB is along the surface normal of the sample. The surface temperature was 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 on the Cu(111), (100) and (110) surfaces spectra, after the HOMB irradiation and the exposure to the oxygen atmosphere. The kinetic energy of HOMB varied from 0.1 to 2.3 eV. The oxidation under 0.3 ML on the Cu(111) proceeded efficiently even with the ambient thermal O@sub 2@ gas, while further oxidation required the higher kinetic energy of O@sub 2@ molecules. The oxide structure above 0.3 ML changed to be a distorted Cu(100)-(@sr@2X@sr@2)R45°-O layer on the Cu(111). This reconstruction is induced by the additional incident energy. We will compare the data on Cu(111), (100) and (110) surfaces and discuss possible models of oxidation processes of Cu on the basis of the incident-energy dependence of the O-uptake curve.