title: Ambience-sensitive optical refraction in ferroelectric nanofilms of NaNbO3.
abstract: Optical index of refractionnis studied by spectroscopic ellipsometry in epitaxial nanofilms of NaNbO3with thickness ∼10 nm grown on different single-crystal substrates. The indexnin the transparency spectral range (n≈ 2.1 - 2.2) exhibits a strong sensitivity to atmospheric-pressure gas ambience. The indexnin air exceeds that in an oxygen ambience byδn≈ 0.05 - 0.2. The thermo-optical behaviourn(T) indicates ferroelectric state in the nanofilms. The ambience-sensitive optical refraction is discussed in terms of fundamental connection between refraction and ferroelectric polarization in perovskites, screening of depolarizing field on surfaces of the nanofilms, and thermodynamically stable surface reconstructions of NaNbO3.
authors.affiliation: Microelectronics and Materials Physics Laboratories, University of Oulu, PO Box 4500, FI-90014 Oulun yliopisto, Finland; Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 182 21 Prague 8, Czech Republic.
authors.forename: Marina
authors.initials: M
authors.lastname: Tyunina
authors.affiliation: Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 182 21 Prague 8, Czech Republic.
authors.forename: Dagmar
authors.initials: D
authors.lastname: Chvostova
authors.affiliation: Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 182 21 Prague 8, Czech Republic.
authors.forename: Oliva
authors.initials: O
authors.lastname: Pacherova
authors.affiliation: Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 182 21 Prague 8, Czech Republic.
authors.forename: Tomas
authors.initials: T
authors.lastname: Kocourek
authors.affiliation: Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 182 21 Prague 8, Czech Republic.
authors.forename: Miroslav
authors.initials: M
authors.lastname: Jelinek
authors.affiliation: Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 182 21 Prague 8, Czech Republic.
authors.forename: Lubomir
authors.initials: L
authors.lastname: Jastrabik
authors.affiliation: Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 182 21 Prague 8, Czech Republic.
authors.forename: Alexander
authors.initials: A
authors.lastname: Dejneka
keywords: NaNbO3; epitaxial; nanofilm; refraction