AVS 57th International Symposium & Exhibition
    Actinides and Rare Earths Topical Conference Monday Sessions
       Session AC+SS-MoM

Paper AC+SS-MoM10
The Non-Equilibrium Nature of Uranium Oxide Surfaces

Monday, October 18, 2010, 11:20 am, Room Isleta

Session: Surface Science of Actinides
Presenter: R.K. Schulze, Los Alamos National Laboratory
Authors: R.K. Schulze, Los Alamos National Laboratory
D.P. Johnson, Los Alamos National Laboratory
M.A. Hill, Los Alamos National Laboratory
Correspondent: Click to Email
We examine the surface reactions of bulk single crystal uranium oxide (UO2) and thin films of uranium oxide on metal using Kelvin probe (surface work function and chemical potential) measurements and x-ray and ultraviolet photoelectron spectroscopy. The processes of surface and sub-surface reactions with small gas phase molecules are examined through in-situ work function measurements (dynamic) while the surface chemistry and configuration are probed with photoemission and LEED measurements (equilibrium). The hyperstoichiometric uranium oxide (UO2+x) is shown to be composed of, in the surface region, labile interstitial oxygen that can be moved relatively easily in and out of the fluorite structure lattice through control of the headspace oxygen activity. The transport of oxygen in this near surface region of the oxide is examined through changes in the surface work function with exposure to various partial pressures of oxygen. The amount of excess oxygen in the oxide lattice of the surface is shown to affect the reactivity of this surface with small gas phase molecules directly. A measurement and description of the band structure of the uranium oxide surface for different levels of oxygen content (UO3, UO2+x, UO2, UO2-x) is presented.