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6 Dec 2004

Volume 85, Issue 23, pp. 5499-5791

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Appl. Phys. Lett. 85, 5694 (2004); http://dx.doi.org/10.1063/1.1828575 (3 pages)

M. Y. Shen, C. H. Crouch, J. E. Carey, and E. Mazur
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Optical phonon softening in strained SrTiO3 thin film: First-principles study

Leejun Kim, Juho Kim, Jaichan Lee, and Donggeun Jung

Appl. Phys. Lett. 85, 5649 (2004); http://dx.doi.org/10.1063/1.1833558 (3 pages) | Cited 8 times

Online Publication Date: 8 December 2004

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The dielectric response and optical phonon of hydrostatically and anisotropically strained SrTiO3 lattices were studied using density functional theory. A structural analysis was performed on the strained SrTiO3 lattice. Following the structural analysis, the optical phonon frequency was calculated for a wide range of lattice distortion. The dielectric constant was calculated from the optical phonon frequency and the Börn effective charges. It was found that significant optical phonon softening occurs at a certain degree of lattice distortion and a certain amount of volume change. In other words, the optical phonon frequency decreased and reached a minimum (50 cm−1) at a specific lattice distortion (c∕a=0.985) as the SrTiO3 lattice was progressively distorted starting from the unstrained state. The phonon frequency increased as the lattice distortion was further increased. This phonon behavior, i.e., optical phonon softening, leads to a maximum dielectric constant at a certain degree of lattice distortion. The first-principles calculation on the strained SrTiO3 shows that the strain affects the dielectric constant of the strained SrTiO3 through the optical phonon softening (or hardening).
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
63.20.D- Phonon states and bands, normal modes, and phonon dispersion
77.55.-g Dielectric thin films
77.22.Ch Permittivity (dielectric function)
68.60.Bs Mechanical and acoustical properties

Investigation of electric internal field in congruent LiNbO3 by electro-optic effect

Melania Paturzo, Domenico Alfieri, Simonetta Grilli, Pietro Ferraro, Paolo De Natale, Marella de Angelis, Sergio De Nicola, Andrea Fińizio, and Giovanni Pierattini

Appl. Phys. Lett. 85, 5652 (2004); http://dx.doi.org/10.1063/1.1832738 (3 pages) | Cited 8 times

Online Publication Date: 8 December 2004

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We investigate the effect of the defect-induced internal field on the electro-optic behavior of z-cut congruent lithium niobate crystals. We measure, by a spatially resolved interferometric technique, the phase retardation due to an external applied voltage occurring in two regions with opposite ferroelectric polarization. When measurements are performed just after electrical poling, the two opposite domains show a different electro-optic behavior. We interpret this as due to an elastic component of the internal field. In fact, the asymmetric behavior disappears when the sample is thermally annealed, i.e., when the internal field vanishes.
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78.20.Jq Electro-optical effects
77.22.Ej Polarization and depolarization
81.40.Gh Other heat and thermomechanical treatments
71.70.Ch Crystal and ligand fields
77.80.Dj Domain structure; hysteresis

Reproducible resistance switching in polycrystalline NiO films

S. Seo, M. J. Lee, D. H. Seo, E. J. Jeoung, D.-S. Suh, Y. S. Joung, I. K. Yoo, I. R. Hwang, S. H. Kim, I. S. Byun, J.-S. Kim, J. S. Choi, and B. H. Park

Appl. Phys. Lett. 85, 5655 (2004); http://dx.doi.org/10.1063/1.1831560 (3 pages) | Cited 323 times

Online Publication Date: 8 December 2004

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Negative resistance behavior and reproducible resistance switching were found in polycrystalline NiO films deposited by dc magnetron reactive sputtering methods. Oxygen to argon gas ratio during deposition was critical in deciding the detailed switching characteristics of either bi-stable memory switching or mono-stable threshold switching. Both metallic nickel defects and nickel vacancies influenced the negative resistance and the switching characteristics. We obtained a distribution of low resistance values which were dependent on the compliance current of high-to-low resistance switching. At 200 °C, the low-resistance state kept its initial resistance value while the high-resistance state reached 85% of its initial resistance value after 5×105 s. We suggested that the negative resistance and the switching mechanism could be described by electron conduction related to metallic nickel defect states existing in deep levels and by small-polaron hole hopping conduction.
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73.50.Fq High-field and nonlinear effects
81.15.Cd Deposition by sputtering
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
71.55.Ht Other nonmetals

Large recoverable electrostrain in Mn-doped (Ba,Sr) TiO3 ceramics

L. X. Zhang, W. Chen, and X. Ren

Appl. Phys. Lett. 85, 5658 (2004); http://dx.doi.org/10.1063/1.1829394 (3 pages) | Cited 49 times

Online Publication Date: 8 December 2004

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In this letter we demonstrate that with a different principle, BaTiO3 ceramics, so far considered as inferior piezoelectrics compared with Pb(Zr,Ti)O3 (PZT), can show a large recoverable electrostrain. This principle utilizes a point-defect-mediated reversible domain switching mechanism, which can in theory generate 0.368% strain for BaTiO3 ceramics at the best condition. Experimental results showed that, after aging at room temperature, 1.0 mol % Mn-doped (Ba0.95Sr0.05)TiO3 ceramics generate a large recoverable nonlinear strain of about 0.12%–0.15% at a field of 3 kV∕mm. This value exceeds that of conventional hard PZT piezoelectric ceramics. A microscopic model for the domain-related electrostrain effect in ceramics is proposed. It is also found that the large electrostrain effect is quite stable with respect to both changing frequency and fatigue cycles. Large electrostrain remains recoverable down to 0.05 Hz and after 10 000 cycles. These results demonstrate the potential of our approach in achieving large recoverable electrostrain in environmental-friendly (Pb-free) ceramics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
77.65.-j Piezoelectricity and electromechanical effects
77.80.Dj Domain structure; hysteresis
77.80.Fm Switching phenomena
81.40.Cd Solid solution hardening, precipitation hardening, and dispersion hardening; aging
61.72.J- Point defects and defect clusters

Structure evolution and ferroelectric and dielectric properties of Bi3.5Nd0.5Ti3O12 thin films under a moderate temperature annealing

X. L. Zhong, J. B. Wang, X. J. Zheng, Y. C. Zhou, and G. W. Yang

Appl. Phys. Lett. 85, 5661 (2004); http://dx.doi.org/10.1063/1.1834731 (3 pages) | Cited 26 times

Online Publication Date: 8 December 2004

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Bi3.5Nd0.5Ti3O12 (BNT) ferroelectric thin films were fabricated on Pt∕Ti∕SiO2∕Si(100) substrates by chemical solution deposition. Structure evolution and ferroelectric and dielectric properties of the as-prepared thin films under a moderate temperature (600–750 °C) annealing were studied in detail. The experimental results showed that the BNT thin films annealed at 700 °C exhibit preferred (00l) orientation, and the remnant polarization (2Pr) and dielectric constant (εr) are higher (the values of 2Pr and εr at 100 kHz are 54 μC∕cm2 and 448, respectively) than those of the deposited films annealed at other temperatures. Additionally, the mechanism concerning the dependence of electrical properties of the BNT ferroelectric thin films on the annealing temperature was discussed.
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77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.55.-g Dielectric thin films
68.55.-a Thin film structure and morphology
77.22.Ch Permittivity (dielectric function)
77.22.Ej Polarization and depolarization
77.80.Dj Domain structure; hysteresis
73.61.Ng Insulators
81.40.Gh Other heat and thermomechanical treatments

High permittivity Li and Al doped NiO ceramics

Yuanhua Lin, Jianfei Wang, Lei Jiang, Yu Chen, and Ce-Wen Nan

Appl. Phys. Lett. 85, 5664 (2004); http://dx.doi.org/10.1063/1.1827937 (3 pages) | Cited 42 times

Online Publication Date: 8 December 2004

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High-permittivity dielectric NiO-based ceramics co-doped with Li and Al (LANO) have been prepared by a traditional solid-state synthesis. Analyses of the ceramic microstructure and composition indicate that Al ions are distributed in grain boundaries, and that uniform boundaries indexed as NiAl2O4 surround the grains. The concentration of Al has a remarkable effect on the dielectric properties of the LANO ceramics. The dielectric constant remains almost constant (∼104–105) at low frequency and has a steplike decrease toward higher frequencies. The high-dielectric-constant response of the LANO ceramics is mainly enhanced by Maxwell–Wagner polarization.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Ch Permittivity (dielectric function)
61.72.S- Impurities in crystals
77.22.Ej Polarization and depolarization
61.72.Mm Grain and twin boundaries

Ferroelectric and dielectric anisotropy in high-quality SrBi2Ta2O9 single crystals

H. Amorín, V. V. Shvartsman, A. L. Kholkin, and M. E. V. Costa

Appl. Phys. Lett. 85, 5667 (2004); http://dx.doi.org/10.1063/1.1836017 (3 pages) | Cited 17 times

Online Publication Date: 8 December 2004

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High-quality SrBi2Ta2O9 single crystals were obtained by a self-flux solution method. The crystals were naturally oriented with [001] direction perpendicular to the major face and edges parallel to [110] axes. The dielectric and ferroelectric properties of the crystals were investigated along the c axis and in the ab plane of the orthorhombic unit cell. The ferro–paraelectric phase transition was observed at TC=355 °C. The anisotropy of dielectric permittivity, i.e., the ratio between average permittivity in the ab plane and along c axis was about 10 at TC and decreased to ∼2 at room temperature. Saturated hysteresis loops were observed for switching in the ab plane. The spontaneous polarization along ferroelectric a axis was estimated to be ≈20 μC∕cm2.
Show PACS
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Ch Permittivity (dielectric function)
77.80.Dj Domain structure; hysteresis
77.80.Fm Switching phenomena
77.80.B- Phase transitions and Curie point
77.22.Ej Polarization and depolarization
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