AVS 51st International Symposium
    Thin Films Wednesday Sessions
       Session TF-WeM

Paper TF-WeM1
Optical Properties of Uranium and Thorium-Based Thin Films as Highly Reflective EUV Mirrors

Wednesday, November 17, 2004, 8:20 am, Room 303C

Session: Optical Thin Films
Presenter: W.R. Evans, Brigham Young University
Authors: D.D. Allred, Brigham Young University
J.E. Johnson, Brigham Young University
W.R. Evans, Brigham Young University
N. Farnsworth, Brigham Young University
A.E. Baker, Brigham Young University
R.S. Turley, Brigham Young University
Correspondent: Click to Email
We present measured reflectances (Beamline 6.3.2, ALS at LBNL) of air oxidized sputtered uranium and thorium, reactively sputtered (O2) uranium oxide and thorium, and reactively sputtered (N2) uranium nitride thin films. The thin films were also characterized using AFM, spectroscopic ellipsometry, LAXRD, TEM, XPS, and XANES. We compare these with our measurements of the reflectance of nickel, gold, and iridium thin films (commonly used soft x-ray reflectors for astronomy and synchrotrons) from 50 to 500 eV at 5Ës, 10Ës, and 15Ës grazing incidence. These show that these two uranium compounds, as UO2 and UN, and thorium as air oxidized thorium can fulfill their promise as the highest-known, single-surface reflector for this portion of the soft x-ray region, being nearly twice as reflective as nickel in the 120 to 200 eV region. We additionally report complex indices of refraction for ThO2, UO2, and UN obtained from reflection and transmission measurements taken at the ALS. Shifts in energy of up to 20 eV between features in the Th spectra suggest the need for possible revision in the atomic scattering factor approach for obtaining optical constants for compounds. There are also important discrepancies between UO2â?Ts and UNâ?Ts actual reflectance with those estimated using the atomic scattering factor approach.