Highly constrained ferroelectric [BaTiO{sub 3}]{sub (1−x)Λ}/[BaZrO{sub 3}]{sub xΛ} superlattices: X-ray diffraction and Raman spectroscopy

Journal Article · Mon Jul 21 00:00:00 EDT 2014 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.4890513· OSTI ID:22308492

Belhadi, J.; Gagou, Y.; El Mendili, Y.; Bouyanfif, H. ^[1]; Yuzyuk, Yu. I.; Raevski, I. P. ^[2]; Wolfman, J. ^[3]

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1. Laboratoire de Physique de la Matière Condensée, Université de Picardie Jules Verne, 33 rue Saint-Leu, 80039 Amiens Cedex (France)
2. Faculty of Physics, Southern Federal University, 5, Zorge str., Rostov-on-Don 344090 (Russian Federation)
3. Laboratoire GREMAN, UMR 7347 CNRS, Université F. Rabelais, Parc de Grandmont, 37200 Tours (France)

We report an x-ray diffraction (XRD) and a Raman-scattering investigation of ferroelectric/paraelectric superlattices [BaTiO{sub 3}] {sub (1−x)Λ}/[BaZrO{sub 3}]{sub xΛ} for which the composition varied, 0.15 ≤ x ≤ 0.85, while the superlattice (SL) modulation period Λ was kept constant at about 100 Å. The samples were epitaxially grown by pulsed laser deposition on MgO substrates buffered with La{sub 0.5}Sr{sub 0.5}CoO{sub 3}. Based on the XRD analysis and on polarized Raman spectra, we have showed that the large strain in SLs induced ferroelectricity in BaZrO{sub 3} (BZ) for all SLs, a material that is paraelectric in the bulk form at any temperature and in the single film. The induced polar axis in BZ layers is perpendicular to the plane of substrate while BaTiO{sub 3} (BT) layers exhibit in-plane polar orientation. Raman spectroscopy revealed a lattice ordering in SLs due to the misfit strain generated by the large lattice mismatch between the alternating BZ and BT layers. This strain induced a huge upward frequency of the lowest E(1TO) soft mode from 60 cm{sup −1} in the BT single film to 215 cm{sup −1} in the SL with x = 0.85. These results show that in spite of relatively large periodicity of SLs, they are highly constrained and the variation of BZ ratio allowed modifying strains between layers. The temperature dependence of the Raman spectra for BT{sub 0.3Λ}/BZ{sub 0.7Λ} and BT{sub 0.7Λ}/BZ{sub 0.3Λ} samples revealed giant shift of the ferroelectric phase transition. The phase transition temperature was found to be upshifted by about 300 °C with respect to BT single crystal.

• OSTI ID: 22308492
• Journal Information: Journal of Applied Physics, Vol. 116, Issue 3; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
BARIUM COMPOUNDS
BUFFERS
ENERGY BEAM DEPOSITION
FERROELECTRIC MATERIALS
LASER RADIATION
LAYERS
MAGNESIUM OXIDES
MONOCRYSTALS
PERIODICITY
PHASE TRANSFORMATIONS
RAMAN EFFECT
RAMAN SPECTRA
RAMAN SPECTROSCOPY
SUBSTRATES
SUPERLATTICES
TEMPERATURE DEPENDENCE
TITANATES
TRANSITION TEMPERATURE
X-RAY DIFFRACTION
ZIRCONATES