Marina Tyunina

  • Citations Per Year
Learn More
In perovskite-structure epitaxial films, it has been theoretically predicted that the polarization and the coherence of polar order can increase with increasing crystallographic strain. Experimental evidence of strain-induced long-range ferroelectric order has not been obtained thus far, posing the fundamental question of whether or not strain can induce(More)
Perovskite-type ferroelectric (FE) crystals are wide bandgap materials with technologically valuable optical and photoelectric properties. Here, versatile engineering of electronic transitions is demonstrated in FE nanofilms of KTaO3, KNbO3 (KNO), and NaNbO3 (NNO) with a thickness of 10-30 unit cells. Control of the bandgap is achieved using heteroepitaxial(More)
Ultrathin (12-15 nm) SrTiO(3) films are grown by pulsed laser deposition on various single-crystal substrates. The crystal structure, orientation, and strain state of the films are studied by x-ray diffraction. The room-temperature optical properties of the films are experimentally determined using ellipsometric spectroscopy in the 1-6 eV spectral range.(More)
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(More)
Heterostructures of thin-film perovskite ferroelectrics and relaxors were grown by in situ pulsed laser deposition on La<sub>0.5</sub>Sr<sub>0.5</sub>CoO<sub>3</sub>/MgO and Pt/sapphire. The dielectric response of the heterostructures was measured as a function of frequency, temperature, amplitude of ac field, magnitude of dc field, and varying the(More)
Epitaxial perovskite potassium tantalate (KTaO(3)) films with thicknesses of 7.4-36 nm are grown on SrTiO(3)(001) substrates by pulsed laser deposition. X-ray diffraction (XRD) analysis reveals evolution of lattice strain with increasing film thickness. A biaxial compressive in-plane strain as large as  - 2.1% is obtained in the 7.4 nm-thick film. A(More)
Optical index of refraction n is studied by spectroscopic ellipsometry in epitaxial nanofilms of NaNbO3 with thickness ∼10 nm grown on different single-crystal substrates. The index n in the transparency spectral range (n ≈ 2.1 - 2.2) exhibits a strong sensitivity to atmospheric-pressure gas ambience. The index n in air exceeds that in an oxygen ambience by(More)
We use computational and experimental methods to study d(0) ferromagnetism at a charge-imbalanced interface between two perovskites. In SrTiO(3)/KTaO(3) superlattice calculations, the charge imbalance introduces holes in the SrTiO(3) layer, inducing a d(0) ferromagnetic half-metallic 2D hole gas at the interface oxygen 2p orbitals. The charge imbalance(More)
M. Tyunina,1,2,* D. Chvostova,2 L. D. Yao,3 A. Dejneka,2 T. Kocourek,2 M. Jelinek,2 and S. van Dijken3 1Microelectronics and Materials Physics Laboratories, University of Oulu, P.O. Box 4500, FI-90014 Oulun Yliopisto, Finland 2Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 182 21 Prague 8, Czech Republic 3NanoSpin,(More)