[1P01-32] Poster session

[1P05] SR-XPS study of chemical process of water on the stainless steel surface as the UHV material

*Wataru Osada^1,2, Kozo Mukai³, Jun Yoshinobu³ (1. National Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology (Japan), 2. Institute of Materials Structure Science, High Energy Accelerator Research Organization (Japan), 3. The Institute for Solid State Physics, The University of Tokyo (Japan))

The chemical processes of H₂O on SUS316L stainless steel surface were investigated using SR-XPS. Experiments were performed on two types of surfaces: an as-installed sample after baking and a cleaned-oxidized sample prepared by repeated cycles of Ar ion sputtering and annealing at 970 K, followed by O₂ exposure. H₂O was adsorbed at 85 K, followed by stepwise heating to room temperature. The O 1s spectra of the as-installed sample indicate that the surface is covered with oxide and oxyhydroxide layers, on which H₂O is adsorbed molecularly without dissociation. In contrast, the cleaned-oxidized surface possesses slight activity toward H₂O dissociation. The oxide phase appears to be more reactive than the oxyhydroxide phase and may retain H₂O to slightly higher temperatures, potentially contributing to the prolonged surface residence time during UHV evacuation.

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