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15 Aug 2012

Volume 112, Issue 4, Articles (04xxxx)

Issue Cover Spotlight Figure

J. Appl. Phys. 112, 041101 (2012); http://dx.doi.org/10.1063/1.4740023 (20 pages)

Iain A. Anderson, Todd A. Gisby, Thomas G. McKay, Benjamin M. O’Brien, and Emilio P. Calius
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back to top Dielectrics and Ferroelectricity

Domain fragmentation during cyclic fatigue in 94%(Bi1/2Na1/2)TiO3-6%BaTiO3

Hugh Simons, Julia Glaum, John E. Daniels, Andrew J. Studer, Andreas Liess, Jürgen Rödel, and Mark Hoffman

J. Appl. Phys. 112, 044101 (2012); http://dx.doi.org/10.1063/1.4745900 (5 pages) | Cited 1 time

Online Publication Date: 20 August 2012

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The fatigue of the lead-free piezoceramic 94%(Bi1/2Na1/2)TiO3-6%BaTiO3 was investigated under bipolar electric fields. Degradation of the polarization, strain, and permittivity was measured during the fatigue process, and correlated with structural data measured at incremental points in the fatigue process using neutron diffraction. The results suggest a two-stage fatigue mechanism whereby, following a field-induced phase transformation to a poled ferroelectric state, the domain structure becomes progressively fragmented by a repetitive process of domain wall pinning and subdivision.
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77.80.Dj Domain structure; hysteresis
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
77.84.Cg PZT ceramics and other titanates
77.80.bn Strain and interface effects
77.22.Ch Permittivity (dielectric function)
77.22.Ej Polarization and depolarization

On the nature of the interfacial layer in ultra-thin TiN/LaLuO3 gate stacks

I. Z. Mitrovic, S. Hall, N. Sedghi, G. Simutis, V. R. Dhanak, P. Bailey, T. C. Q. Noakes, I. Alexandrou, O. Engstrom, J. M. J. Lopes, and J. Schubert

J. Appl. Phys. 112, 044102 (2012); http://dx.doi.org/10.1063/1.4746790 (7 pages) | Cited 1 time

Online Publication Date: 21 August 2012

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We present a detailed investigation on the nature of the interfacial layer (IL) in ultra-thin TiN/LaLuO3 (LLO) gate stacks, which is of importance to facilitate CMOS scaling. The molecular beam deposited LaLuO3 films are found to be amorphous by high-resolution transmission electron microscopy. A ∼9 Å thick LaLuO3/interlayer transition observed by medium energy ion scattering correlates with the presence of a dual silicate/SiO2-like interfacial layer derived from the analysis of photoelectron line positions and electron energy loss spectra. A theoretical model is used for the dielectric transition in a bi-layer LaLuO3/IL structure, linking physical and electrical characterization data. The obtained leakage current of 10−3 A/cm2 at 1.5 V and equivalent oxide thickness of 0.75 nm for TiN/LaLuO3 gate stacks are adequate for scaling in the 14-12 nm node.
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85.30.Tv Field effect devices
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology

Flexoelectric effect in finite samples

Alexander K. Tagantsev and Alexander S. Yurkov

J. Appl. Phys. 112, 044103 (2012); http://dx.doi.org/10.1063/1.4745037 (7 pages) | Cited 1 time

Online Publication Date: 23 August 2012

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Static flexoelectric effect in a finite sample of a solid is addressed in terms of phenomenological theory for the case of a thin plate subjected to bending. It has been shown that despite an explicit asymmetry inherent to the bulk constitutive electromechanical equations which take into account the flexoelectric coupling, there exists a situation where electromechanical response for a finite sample is “symmetric.” “Symmetric” means that if a sensor and an actuator are made of a flexoelectric element, performance of such devices can be characterized by the same effective piezoelectric coefficient. This behavior is consistent with the thermodynamic arguments offered earlier, being in conflict with the current point of view on the matter in literature. This result was obtained using standard mechanical boundary conditions valid for the case where the polarization vanishes at the surface. It was shown that, for the case where the polarization at the surface is not zero, the aforementioned symmetry of electromechanical response may be violated if standard mechanical boundary conditions are used, leading to a conflict with the thermodynamic arguments. It is suggested that this conflict may be resolved when using modified mechanical boundary conditions. It is also shown that the contribution of surface piezoelectricity to the flexoelectric response of a finite sample is expected to be comparable to that of the static bulk contribution (including materials with high values of the dielectric constant) and to scale as the bulk value of the dielectric constant (similar to the bulk contribution). This finding implies that if the experimentally measured flexoelectric coefficient scales as the dielectric constant of the material, this does not imply that the measured flexoelectric response is controlled by the static bulk contribution to the flexoelectric effect.
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77.65.-j Piezoelectricity and electromechanical effects
46.35.+z Viscoelasticity, plasticity, viscoplasticity
77.22.Ch Permittivity (dielectric function)
77.22.Ej Polarization and depolarization

Space-charge polarization of a dilute electrolytic cell in the presence of diffuse double layers

Atsushi Sawada

J. Appl. Phys. 112, 044104 (2012); http://dx.doi.org/10.1063/1.4745046 (11 pages)

Online Publication Date: 23 August 2012

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The frequency dependence of the complex dielectric constant due to space-charge polarization is analyzed for a dilute electrolytic cell with blocking electrodes in the presence of diffuse double layers. If the diffuse double layer is not generated by an external voltage application but induced by a contact potential difference between the electrode and electrolytic solution, the dielectric constant in Poisson’s equation does not include the contribution of the space-charge polarization. The space-charge polarization is measured by applying an external field. The external voltage source supplies positive and negative charges to the electrodes to keep the potential difference between the electrodes constant in the measurement. Accordingly, the dielectric constant in Poisson’s equation has to include the contribution of the space-charge polarization to take account of the external charges in the data analysis. An electrode polarization model developed with this concept can well explain the frequency-dependent behavior of the complex dielectric constant observed for the dilute electrolytic cell with the specific adsorption of ions to the electrodes.
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88.80.ff Batteries

Effect of Pt bottom electrode texture selection on the tetragonality and physical properties of Ba0.8Sr0.2TiO3 thin films produced by pulsed laser deposition

J. P. B. Silva, K. C. Sekhar, A. Almeida, J. Agostinho Moreira, J. Martín-Sánchez, M. Pereira, A. Khodorov, and M. J. M. Gomes

J. Appl. Phys. 112, 044105 (2012); http://dx.doi.org/10.1063/1.4748288 (8 pages)

Online Publication Date: 28 August 2012

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The effect of platinum (Pt) bottom electrode texture on the tetragonality, dielectric, ferroelectric, and polarization switching response of pulsed laser deposited Ba0.8Sr0.2TiO3 (BST) thin films has been studied. The x-ray diffraction and Raman analysis revealed the higher tetragonality of BST films when they were grown on higher (111) textured Pt layer. The properties like dielectric permittivity, polarization, switching time, and leakage currents were found to be correlated to tetragonality and orientation of the BST films. The polarization current was observed to be higher in BST films on Pt epitaxial layer and it exhibits exponential dependence on the electric field. The voltage-current measurements displayed Ohmic behavior of leakage current irrespective of Pt texture for low voltages (up to 1 V), whereas at higher voltages the conduction mechanism was found to be dependent on texture selection of bottom Pt electrode.
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77.55.-g Dielectric thin films
68.55.jm Texture
81.15.Fg Pulsed laser ablation deposition
77.80.Fm Switching phenomena
77.22.Ej Polarization and depolarization
77.22.Ch Permittivity (dielectric function)

Effect of Pr substitution on structural and dielectric properties of SrTiO3

Xiaofei Wang, Qiubo Hu, Liben Li, and Xiaomei Lu

J. Appl. Phys. 112, 044106 (2012); http://dx.doi.org/10.1063/1.4747937 (4 pages) | Cited 1 time

Online Publication Date: 29 August 2012

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Pr-doped SrTiO3 ceramics were fabricated by the conventional solid-state reaction method. Pr-doping greatly decreased the lattice parameters and the average grain size of SrTiO3 ceramics sample. Two thermally activated dielectric relaxations were found for the low- and high-temperature relaxations, respectively. By means of a detailed analysis, the low-temperature relaxation was ascribed to the electric hopping between Pr3+ and Pr4+ induced by the Pr-doping, and the origin of the high-temperature relaxation was changed from oxygen vacancies to the polar nanoregions with the increase of Pr content.
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77.22.Gm Dielectric loss and relaxation
77.22.Ej Polarization and depolarization
61.72.sd Impurity concentration
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
61.72.jd Vacancies
61.66.Fn Inorganic compounds

Modeling of dielectric and piezoelectric response of 1-3 type piezocomposites

R. Jayendiran and A. Arockiarajan

J. Appl. Phys. 112, 044107 (2012); http://dx.doi.org/10.1063/1.4748057 (7 pages) | Cited 1 time

Online Publication Date: 30 August 2012

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A study is carried out to compare the non-linear behaviour of 1-3 piezocomposites with different volume fractions and bulk piezoceramics. Experiments are conducted to measure the electrical displacement and strain on piezocomposites and ceramics under high cyclic electrical loading. A thermodynamically consistent framework, combining the phenomenological and micromechanical models, is developed to predict the coupled behavior. Volume fractions of three distinct uni-axial variants (instead of six variants) are used as internal variables to describe the microscopic state of the material. In this model, the grain boundary effects are taken into account by introducing the back fields (electric field and stress) as non-linear kinematic hardening functions. In order to calculate the effective properties (elastic, piezoelectric, and dielectric constants) of piezocomposites for different volume fractions, an analytical model based on equivalent layered approach is proposed. The predicted effective properties are incorporated in the proposed model, and the classical hysteresis (electrical displacement versus electric field) as well as butterfly curves (strain versus electric field) is simulated. Comparison between the experiments and the simulations shows that this model can reproduce the characteristics of non-linear coupled response. It is observed that the variation in fiber volume fraction has a significant influence on the response of the 1-3 piezocomposites.
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77.65.Bn Piezoelectric and electrostrictive constants
77.22.Ch Permittivity (dielectric function)
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.dq Other elastic constants

Electronic band structure and optical phonons of BaSnO3 and Ba0.97La0.03SnO3 single crystals: Theory and experiment

T. N. Stanislavchuk, A. A. Sirenko, A. P. Litvinchuk, X. Luo, and S.-W. Cheong

J. Appl. Phys. 112, 044108 (2012); http://dx.doi.org/10.1063/1.4748309 (7 pages) | Cited 3 times

Online Publication Date: 31 August 2012

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Optical properties of insulating BaSnO3 (BSO) and conducting Ba0.97La0.03SnO3 (BLSO) single crystals were studied at room temperature in a wide spectral range between 0.01 and 5.9 eV by means of spectroscopic ellipsometry. The far-infrared spectra of the optical phonons in BSO and BLSO were complemented by polarized Raman scattering measurements in BSO. The electronic band structure and the optical response (dielectric function) were calculated using density functional theory, which allowed for the interpretation of the main spectroscopic features such as optical phonons and electronic interband transitions. To reconcile the observed experimental spectra with the theory, a departure from the ideal perovskite structure on the local scale was proposed for BSO.
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71.20.Ps Other inorganic compounds
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
78.30.Hv Other nonmetallic inorganics
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
63.20.D- Phonon states and bands, normal modes, and phonon dispersion
77.22.Ch Permittivity (dielectric function)
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