A metastable de-excitation spectroscopy (MDS) study on oxygen adsorption on a polycrystalline zirconium surface |
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Authors: | Mitsunori Kurahashi Yasushi Yamauchi |
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Institution: | National Research Institute for Metals, 1-2-1 Sengen Tsukuba, Ibaraki 305-0047, Japan |
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Abstract: | The adsorption of oxygen on a polycrystalline zirconium surface at room temperature has been studied by metastable de-excitation spectroscopy (MDS) in conjunction with UPS and AES. From the analysis of the measured spectra, we have shown the following. (1) At the initial stage of oxygen adsorption (exposure <1.2 L), the surface density of states (SDOS) of zirconium changes little at around the Fermi level (EF), while it decreases appreciably at 1–2 eV below EF (EB=1–2 eV) by oxygen adsorption. (2) The SDOS at EB=0–2 eV decreases with increasing oxygen exposure at >1.2 L and disappears at >8 L. (3) The oxygen 2p states (EB=5–8 eV) are localized at the subsurface region at oxygen exposure 0–2 L. (4) The ZrO2 phase appears at the outermost zirconium surface at around 2 L, then grows with increasing exposure, and finally dominates at >8 L. It is suggested that two different phases (ZrO2 phase and that in which oxygen occupies subsurface sites) coexist at the outermost surface at 2–8 L. |
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Keywords: | Metastable de-excitation spectroscopy Oxidation Surface electronic states Zirconium surface |
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