AVS 52nd International Symposium
    Surface Science Tuesday Sessions
       Session SS2-TuM

Paper SS2-TuM11
The Reaction of Water over the Stoichiometric and Defected Surfaces of Uranium Dioxide: a High Resolution XPS Study

Tuesday, November 1, 2005, 11:40 am, Room 203

Session: Defects on Oxide Surfaces
Presenter: H. Idriss, The Univ. of Auckland, New Zealand
Authors: S.D. Senanayake, The Univ. of Auckland, New Zealand
G.I.N. Waterhouse, The Univ. of Auckland, New Zealand
A.S.Y. Chan, Rutgers, The State Univ. of New Jersey
D.R. Mullins, Oak Ridge National Lab.
T.E. Madey, Rutgers, The State Univ. of New Jersey
H. Idriss, The Univ. of Auckland, New Zealand
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The chemistry of the uranium oxides is complex and historically been important to many aspects of nuclear technology. A recent study has shown using XPS that argon ion sputtering of the UO@sub 2@ surface can form a stable reduced oxide surface (UO@sub 2-x@) due to creation of oxygen defects.@footnote 1@ This work uses high resolution photoelectron spectroscopy (HRXPS) performed at the beam line U12a at the National Synchrotron Light Source/BNL to investigate the effect of this defect formation process. Sputtering at 300 and 95K gave different defect distributions. The reduced surface has a complex set of oxidation states lower than that of U@super +4@ including U metal (U@super 0@). Previous investigations made on the reactivity of water vapor on polycrystalline UO@sub 2@@footnote 2@ and defected single crystal UO@sub 2-x@ surface have revealed complex reaction pathways to the production of H@sub 2@ and XPS has further confirmed adsorbate induced oxidation of the surface.@footnote 1@ This work aims to further examine the effect of D@sub 2@O adsorption on the stoichiometric and sputter reduced surfaces of UO@sub 2@ at 300 and 95K. The effects of the thermal chemistry and oxidation of the surface is studied using temperature programmed XPS (TPXPS). In particular, the formation of D@sub 2@O ice at low temperature and dissociated OD species versus the role of defects in this heterogeneous interplay is examined. @FootnoteText@ @footnote 1@ Senanayake S.D., Idriss H., Surf. Sci. 563 (2004) 135.@footnote 2@ Senanayake S.D., Rousseau R., Colegrave D., Idriss H, J. Nucl. Mater. In press.