AVS 61st International Symposium & Exhibition
    Actinides and Rare Earths Focus Topic Monday Sessions
       Session AC+AS+MI+SA+SS-MoM

Paper AC+AS+MI+SA+SS-MoM10
Unraveling the Mystery of Reactively-Sputtered UO(4+x)

Monday, November 10, 2014, 11:20 am, Room 301

Session: Spectroscopy, Microscopy and Dichroism of Actinides and Rare Earths
Presenter: David Allred, Brigham Young University
Authors: D.D. Allred, Brigham Young University
R.S. Turley, Brigham Young University
B.S. McKeon, Brigham Young University
A. Diwan, Brigham Young University
E.A. Scott, Brigham Young University
R.R. Vanfleet, Brigham Young University
Correspondent: Click to Email
We recently found EDX and XPS evidence in reactive sputtered uranium oxide thin films of higher oxygen-to-uranium ratios than the 3-to-1 allowed by stoichiometry. We used reactive, DC-magnetron sputtering in 100% oxygen to prepare uranium-oxide thin films on silicon wafer with the highest possible oxygen content to investigate this. Both EDX & XPS showed that the ratio of oxygen-to-uranium in freshly samples was at least 4-to-1, with compositions approached 5 to 1. The potential explanations are uranates or peroxides. Detecting hydrogen- and an element difficult to detect in thin films-is crucial in understanding what is happening chemically. Uranates require cations. The only one possible in our films would be hydrogen. Similarly, bulk uranium peroxides without water/ hydrogen peroxide of hydration are not known. (We have found evidence of uranium trioxide being weekly hygroscopic and stored samples in a dry environment, nonetheless these samples show high oxygen contents as prepared.) We report our chemistry and structural (TEM and XRD) attempts to solve this mystery. We also report are measurement of extreme ultraviolet reflectance of this material. (ALS-beamline 6.3.2)