Luminescence of thin uranium oxide films

Abstract

Electron-induced luminescence and Auger electron spectroscopy were used to study thin uranium oxide layers prepared by exposing clean, high-purity, polycrystalline uranium surfaces to small amounts of either pure H 2O, dry O 2, or CO between 85 and 300 K. All oxidized surfaces exhibited a uniform, faint blue luminescence whose spectrum consisted of an asymmetric peak centered at 400 nm that was ascribed to excitation of F-centers in the surface oxide layers. The adsorption of H 2O vapor on an oxygen-saturated surface resulted in the appearance of an additional bright red luminescence that was localized at several small spots on the sample surface and whose spectrum consisted of an asymmetric peak centered at 800 nm. These spots were correlated with surface pit formation resulting from the presence of condensed H 2O on the uranium surface. A preliminary evaluation of electron-induced luminescence as a surface specific technique is made.