PLoS ONE (Jan 2016)

Optical Properties of Ferroelectric Epitaxial K0.5Na0.5NbO3 Films in Visible to Ultraviolet Range.

  • E Chernova,
  • O Pacherova,
  • T Kocourek,
  • M Jelinek,
  • A Dejneka,
  • M Tyunina

DOI
https://doi.org/10.1371/journal.pone.0153261
Journal volume & issue
Vol. 11, no. 4
p. e0153261

Abstract

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The complex index of refraction in the spectral range of 0.74 to 4.5 eV is studied by variable-angle spectroscopic ellipsometry in ferroelectric K0.5Na0.5NbO3 films. The 20-nm-thick cube-on-cube-type epitaxial films are grown on SrTiO3(001) and DyScO3(011) single-crystal substrates. The films are transparent and exhibit a significant difference between refractive indices Δn = 0.5 at photon energies below 3 eV. The energies of optical transitions are in the range of 3.15-4.30 eV and differ by 0.2-0.3 eV in these films. The observed behavior is discussed in terms of lattice strain and strain-induced ferroelectric polarization in epitaxial perovskite oxide films.