Large variations of refractive index in the visible spectral range are obtained in epitaxial perovskite oxide ferroelectric films experiencing lattice strain. The strain is imposed by substrates, on top of which the films are grown. The optical constants are determined using the spectroscopic ellipsometry. As a reference and for comparison, also prototype single crystals are inspected. The variations in refraction are related to the lattice strain in the films. Elasto-optic coefficient is formally estimated using the out-of-plane lattice elongation or shrinkage in the films compared to bulk. The obtained elasto-optic coefficients exceed significantly those previously reported for ferroelectric materials.
FerrarosP, GrilliS, De NataleP.Ferroelectric crystals for photonic applications: including nanoscale fabrication and characterization techniques. Berlin: Springer Science & Business Media; 2013.
2.
LinesME, GlassAM.Principles and applications of ferroelectrics and related materials. Oxford: Oxford University Press; 1977.
3.
QinM, YaoK, LiangYC.High efficient photovoltaics in nanoscaled ferroelectric thin films. Appl Phys Lett. 2008;93(12):122904.
4.
GuoR, YouL, ZhouY, Non-volatile memory based on the ferroelectric photovoltaic effect. Nat Commun. 2013;4:1990.
5.
DickenMJ, SweatlockLA, PacificiD, Electrooptic modulation in thin film barium titanate plasmonic interferometers. Nano Lett. 2008;8:4048–4052.
6.
TyuninaM, YaoL, ChvostovaD, Concurrent bandgap narrowing and polarization enhancement in epitaxial ferroelectric nanofilms. Sci Technol Adv Mater. 2015;16:026002.
7.
TyuninaM, ChvostovaD, PacherovaO, Ambience-sensitive optical refraction in ferroelectric nanofilms of NaNbO3. Sci Technol Adv Mater. 2014;15:045001.
8.
ChernovaE, PacherovaO, ChvostovaD, Strain-controlled optical absorption in epitaxial ferroelectric BaTiO3 films. Appl Phys Lett. 2015;106:192903.
9.
SandoD, YangY, BousquetE, Large elasto-optic effect and reversible electrochromism in multiferroic BiFeO3. Nat Commun. 2016;7:10718.
10.
DejnekaA, TyuninaM, NarkilahtiJ, Tensile strain induced changes in the optical spectra of SrTiO3 epitaxial thin films. Phys Solid State. 2010;52(10):2082–2089.
11.
ChernovaE, PacherovaO, KocourekT, Optical properties of ferroelectric epitaxial K0.5Na0.5NbO3 films in visible to ultraviolet range. PLoS ONE. 2016;11(4):e0153261.
FujiwaraH, KohJ, RoviraPI, Assessment of effective-medium theories in the analysis of nucleation and microscopic surface roughness evolution for semiconductor thin films. Phys Rev B. 2000;61:10832–10844.
14.
CardonaM.Optical properties and band structure of SrTiO3 and BaTiO3. Phys Rev. 1965;140:A651–A655.
15.
TyuninaM, NarkilahtiJ, PlekhM, Evidence for strain-induced ferroelectric order in epitaxial thin-film KTaO3. Phys Rev Lett. 2010;104:260.
16.
DrDomenicoMJr, WempleSH.Oxygen-octahedra ferroelectrics. I. Theory of electro-optical and nonlinear optical effects. J Appl Phys. 1969;40(2):720–734.
17.
BergerRF, FennieCJ, NeatonJB.Band gap and edge engineering via ferroic distortion and anisotropic strain: the case of SrTiO3. Phys Rev Lett. 2011;107(14):2158.
18.
LefkowitzI, ŁukaszewiczK, MegawHD.The high-temperature phases of sodium niobate and the nature of transitions in pseudosymmetric structures. Acta Crystallogr. 1966;20(5):670–683.
19.
MegawHD.The seven phases of sodium niobate. Ferroelectrics. 1974;7(1):87–89.
20.
LideDavid R.CRC handbook of chemistry and physics. 84th ed. London: CRC Press; 2003.
21.
VeithenM, GhosezP.Temperature dependence of the electro-optic tensor and refractive indices of BaTiO3 from first principles. Phys Rev B. 2005;71(13):1751.
