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Title: Optical constants of SrF2 thin films in the 25-780-eV spectral range

The transmittance and the optical constants of SrF2 thin films, a candidate material for multilayer coatings operating in the extreme ultraviolet and soft x-rays, have been determined in the spectral range of 25–780 eV, in most of which no experimental data were previously available. SrF2 films of various thicknesses were deposited by evaporation onto room-temperature, thin Al support films, and their transmittance was measured with synchrotron radiation. The transmittance as a function of film thickness was used to calculate the extinction coefficient k at each photon energy. A decrease in density with increasing SrF2 film thickness was observed. In the calculation of k, this effect was circumvented by fitting the transmittance versus the product of thickness and density. The real part of the refractive index of SrF2 films was calculated from k with Kramers-Krönig analysis, for which the measured spectral range was extended both to lower and to higher photon energies with data in the literature combined with interpolations and extrapolations. In conclusion, with the application of f- and inertial sum rules, the consistency of the compiled data was found to be excellent.
Authors:
 [1] ;  [1] ;  [1] ;  [2] ;  [2] ;  [1] ;  [2] ;  [3]
  1. GOLD-Instituto de Optica-Consejo Superior de Investigaciones Cientificas, Madrid (Spain)
  2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  3. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Publication Date:
OSTI Identifier:
1266685
Report Number(s):
LLNL-JRNL--643835
Journal ID: ISSN 0021-8979
Grant/Contract Number:
AC52-07NA27344
Type:
Accepted Manuscript
Journal Name:
Journal of Applied Physics
Additional Journal Information:
Journal Volume: 113; Journal Issue: 14; Journal ID: ISSN 0021-8979
Publisher:
American Institute of Physics (AIP)
Research Org:
Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; 36 MATERIALS SCIENCE thin films; photons; optical constants; extreme ultraviolet radiation; refractive index