soft x-ray, EUV, low-angle reflector, nickel, uranium oxide, uranium nitride, synchrotron, EUV/soft X-ray astronomy, optical constants


Uranium oxide and uranium nitride thin films reflect significantly more than all previously known/standard reflectors (e.g., nickel, gold, and iridium) for most of the 4-10 nm range at low angles of incidence. This work includes measurements of the EUV/soft x-ray (2-20 nm) reflectance of uranium-based thin films (~20 nm thick) and extraction of their optical constants (d and ?). We report the reflectances at 5, 10, and 15 degrees grazing incidence of air-oxidized sputtered uranium, reactively sputtered (O2) uranium oxide, and reactively sputtered (N2) uranium nitride thin films measured at Beamline 6.3.2 at the Advanced Light Source (ALS) at Lawrence Berkeley National Laboratory (LBNL). Additionally, we report optical constants of reactively sputtered uranium oxide at nine wavelengths from 4.6 to 17.5 nm derived from ALS angle-scan reflectance measurements. We also report optical constants of uranium nitride at 13 and 14 nm. We compare the reflectance of these uranium-compound thin films to gold, nickel (and nickel oxide), and iridium thin films from 2.5 to 11.6 nm. These metal thin films were chosen for comparison due to their wide use in EUV/sift x-ray applications as low-angle, thin-film reflectors. The uranium compounds can exhibit some surface oxidation in ambient air. There are important discrepancies between UO2's and UN's actual thin-film reflectance with those predicted from tabulated optical constants of the elemental constituents of the compounds. These differences are also demonstrated in the optical constants we report. Uranium-based optics applications have important advantages for zone plates, thin-film reflectors and filters.

Original Publication Citation

Richard L. Sandberg, David D. Allred, Shannon Lunt, Marie K. Urry, R. Steven Turley, "Optical Properties and Application of Uranium-based Thin Films for the Extreme Ultraviolet and Soft X-ray Region," in Optical Constants of Materials for UV to X-Ray Wavelengths, edited by Regina Soufli, and John F. Seely, Proceedings of SPIE, Vol. 5538, (SPIE, Bellingham, WA, 24) 17-118. [][].

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Peer-Reviewed Article

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Society of Photo Optical Instrumentation Engineers (SPIE)




Physical and Mathematical Sciences


Physics and Astronomy