bluuebunny/crossref_metadata_2025 huggingface dataset:
Dilepton production in finite baryonic quark–gluon plasma
Authors: Kumar Yogesh , Singh S. Somorendro
Published: September 2012

We study the evolution of hot plasma through a statistical model in the hadronic medium. Evolution of the plasma can be expressed by the free energy at finite temperature and quark chemical potential of the constituent particles in the system. In this study, the dynamical quark mass is dependent on momentum and temperature. The evolution is explained through thermodynamic variables like free energy and entropy curve. These variables show the behaviour of the system for the different chemical potentials, μ, at these transition temperatures T = 150–170 MeV. Moreover, the study of the dilepton production at these finite temperatures and quark chemical potentials from the fireball of quark–gluon plasma shows a specific structure of dilepton spectrum in the intermediate mass region of 1.0–4.0 GeV and its production rate is observed to be a strong increasing function of quark chemical potential for quark and antiquark annihilation. We further observe lepton spectra coming from the hadronic phase in the low mass M = 0–1.2 GeV region.
What all the noise is about: the physical basis of cellular individuality
Authors: Charlebois Daniel A. , Kærn Mads
Published: September 2012

Noise has been traditionally viewed as undesirable in biology, resulting in disorder, distortion, and disruption, and ultimately as something that needs to be filtered and removed. More recently, it has been shown that noise can also be beneficial. We briefly review historical developments pertaining to noise in biological physics, and some of the current research in the field of molecular and cellular biophysics.
Modeling the influence of surface effect and molecular force on pull-in voltage of rotational nano–micro mirror using 2-DOF model
Authors: Beni Y. Tadi , Koochi A. , Kazemi A.S. , Abadyan M.
Published: September 2012

Herein, the torsion–bending coupled pull-in instability of rotational electromechanical nano–micro mirror is investigated using a two-degree-of-freedom (2-DOF) model. Two nano-scale phenomena (i.e., surface effect and molecular van der Waals attraction) are incorporated in the model. None of the previous 2-DOF models have taken these nano-scale effects into account. Results reveal that the influences of surface effects and intermolecular force on the coupled pull-in voltage of the nano–micro mirror highly depend on the geometrical characteristics of the system. It is found that if the mirror dimensions are of the order of the material length scale parameters, the pull-in characteristics computed via the present 2-DOF model will highly differ from those predicted by previous one-degree-of-freedom (1-DOF) models. Interestingly, the influence of surface effects on pull-in voltage of the system highly depends on the bending/torsion coupling ratio. Moreover, results show that the van der Waals force can reduce the pull-in voltage of the mirror. This deteriorating effect is more highlighted in the torsional mode than the bending mode.
Kinetic treatment for the exact solution of the unsteady Rayleigh flow problem of a rarefied homogeneous charged gas bounded by an oscillating plate
Authors: AbdelWahid T.Z. , Elagan S.K.
Published: September 2012

The exact solution of the unsteady Rayleigh flow problem of a rarefied charged gas bounded by an oscillating plate has been made. For this purpose, we use the traveling wave solution method. The kinetic and the irreversible thermodynamic properties of the charged gas are presented from the molecular viewpoint. Our study is based on the solution of the Bhatnager–Gross–Krook (BGK) model of the Boltzmann kinetic equation, with the precision value of the electron–electron collision frequency. The BGK model equation coupled with Maxwell’s equations, for electron gas near an oscillating rigid plane, are solved. The distinction and comparisons between the perturbed and the equilibrium velocity distribution functions are illustrated. The ratios between the different contributions of the internal energy changes are predicted via the extended Gibbs equation for both diamagnetic and paramagnetic plasmas. The results are applied to a typical model of laboratory argon plasma.
Tachyon cosmology with nonminimal derivative coupling
Authors: Banijamali A. , Sadeghi J. , Vaez H.
Published: September 2012

In this paper we study a gravitational theory in which tachyons play the role of a scalar field. Also, nonminimal derivative coupling between tachyons and the Einstein tensor is considered in the model. We show that at the initial time, tachyon field behavior is exponential and its behavior at late times is liner in cosmic time. We investigate the asymptotic behavior of scale factor a(t) = eα(t) and show that in the limit t → ∞ it is impossible to have a constant [Formula: see text] and the model has an initial cosmological singularity (i.e., a ∝ (t – ti)2/β) in the limit t – ti.
Scattering of electromagnetic plane wave by a circular disk on a grounded substrate
Authors: Jafri A.D.U. , Naqvi Q.A. , Syed A.A. , Hongo Kohei
Published: September 2012

In this investigation, scattering from a perfectly conducting circular disk located on a grounded substrate has been studied rigorously. The incident field is a plane wave. The method of analysis uses a Kobayashi potential. The mathematical formulation produces dual integral equations (DIEs). These DIEs are solved by using the discontinuous properties of Weber–Schafheitlin’s integral. After applying the projection, the resulting expressions reduce to matrix equations for expansion coefficients. The matrix elements are in the form of infinite integrals. The far-field patterns of the scattered field are computed for different incident angles and disk sizes for both E- and H-polarizations. To validate the results, we have computed the solution based on the physical optics approximation. The comparison of the results shows good agreement.
Population genetics study of common (Pipistrellus pipistrellus) and soprano (Pipistrellus pygmaeus) pipistrelle bats from central Europe suggests interspecific hybridization
Authors: Sztencel-Jabłonka A. , Bogdanowicz W.
Published: September 2012

The discovery that the most widespread bat in Europe comprises cryptic species, Pipistrellus pipistrellus (Schreber, 1774) (common pipistrelle) and Pipistrellus pygmaeus (Leach, 1825) (soprano pipistrelle), provides a great opportunity to look at the mechanism of species coexistence. Based on eight nuclear microsatellite loci (n = 353), we observed similarities between the species in Poland with respect to heterozygosity, allelic richness, mean relatedness, and inbreeding coefficients. However, pronounced differences in migratory patterns (shown by assignment tests) suggest that P. pygmaeus is the more migratory species. The proportion of bats migrating between colonies differed significantly, with 17.1% and 41.8% individuals of P. pygmaeus and P. pipistrellus, respectively, confidently assigned to colonies of origin. Both species demonstrated a more migratory character in central Europe compared with the populations from the British Isles. Given the cryptic nature of the examined taxa, we also assessed whether they hybridize. Hybridization was confirmed by three methods—one based on genetic distance and two based on Bayesian approaches. The overall hybridization rate, depending on assumed threshold values, ranged from 1.7% to 13.3% for both species. We conclude that the population structuring in these pipistrelles is not homogenous across their range. Moreover, hybridization between them in continental Europe does occur and is not rare.
Influence of sampling scheme on the inference of sex-biased gene flow in the American badger (Taxidea taxus)
Authors: Kierepka E.M. , Latch E.K. , Swanson B.J.
Published: September 2012

Population genetics has fueled a substantial growth in studies of dispersal, a life-history trait that has important applications in ecology and evolution. Mammals typically exhibit male-biased gene flow, so this pattern often serves as a null hypothesis in empirical studies. Estimation of dispersal using population genetics is not without biases, so we utilized a combination of population genetic methods and simulations to evaluate gene flow within the American badger ( Taxidea taxus (Schreber, 1777)), a highly elusive and poorly understood mustelid. A total of 132 badgers captured between 2001 and 2002 were genotyped at nine microsatellite loci to investigate fine-scale genetic structure consistent with philopatry in females and dispersal in males. Resultant genetic patterns were largely consistent with a panmictic population with little evidence for sex-biased dispersal, and simulations confirmed that our sampling scheme did not substantially impact our statistics. An overall deficiency of heterozygotes was observed across the Lower Peninsula, which indicates either a Wahlund effect, mixing of separate populations, or inbreeding. Our study emphasizes the importance in deciphering between actual behavioral mechanisms and sampling effects when interpreting genetic data to understand other factors that influence dispersal like population density and territoriality.
Ultrastructure of the coenecium of Cephalodiscus (Hemichordata: Pterobranchia)
Authors: Gonzalez Paul , Cameron Christopher B.
Published: September 2012

The ultrastructure of the coenecia of Cephalodiscus (Cephalodiscus) hodgsoni Ridewood, 1907, Cephalodiscus (Idiothecia) nigrescens Lankester, 1905, and Cephalodiscus (Orthoecus) densus Andersson, 1907 was characterized using light microscopy, transmission electron microscopy, and scanning electron microscopy. The coenecium of Cephalodiscus is composed of layers of coenecial material of variable thickness laid down one upon the next and separated by sheets. Thick fusellar-like layers (up to 160 μm thick) and thin cortical-like layers (down to 15 nm thick) are present, but do not form two distinct components. Instead, a continuum exists in the thickness and shape of these layers. At the ultrastructural level, both fusellar-like and cortical-like layers are composed of thin (16–23 nm) long and straight fibrils, similar to the fibrils described in extant Rhabdopleura Allman, 1869. In C. densus, fibrils in the outer secondary deposits show a parallel arrangement, similar to the arrangement of fibrils in the graptolite eucortex. Although similarities in the shape and arrangement of growth increments between Cephalodiscus, Rhabdopleura, and graptolites probably reflect homologous zooidal behaviors and secretion mechanisms, differences at the ultrastructural level show that fibril types and fibril arrangement can evolve independently from larger scale features of the coenecium.
THERMODYNAMIC OF THE GHOST DARK ENERGY UNIVERSE
Authors: FENG CHAO-JUN , LI XIN-ZHOU , SHEN XIAN-YONG
Published: September 2012

Recently, the vacuum energy of the QCD ghost in a time-dependent background is proposed as a kind of dark energy candidate to explain the acceleration of the Universe. In this model, the energy density of the dark energy is proportional to the Hubble parameter H, which is the Hawking temperature on the Hubble horizon of the Friedmann–Robertson–Walker (FRW) Universe. In this paper, we generalized this model and chose the Hawking temperature on the so-called trapping horizon, which will coincide with the Hubble temperature in the context of flat FRW Universe dominated by the dark energy component. We study the thermodynamics of Universe with this kind of dark energy and find that the entropy-area relation is modified, namely, there is another new term besides the area term.
QUANTUM LARMOR RADIATION FROM A MOVING CHARGE IN AN ELECTROMAGNETIC PLANE WAVE BACKGROUND
Authors: NAKAMURA GEN , YAMAMOTO KAZUHIRO
Published: September 2012

We extend our previous work [Phys. Rev. D83, 045030 (2011)], which investigated the first-order quantum effect in the Larmor radiation from a moving charge in a spatially homogeneous time-dependent electric field. Specifically, we investigate the quantum Larmor radiation from a moving charge in a monochromatic electromagnetic plane wave background based on the scalar quantum electrodynamics at the lowest order of the perturbation theory. Using the in–in formalism, we derive the theoretical formula of the total radiation energy from a charged particle in the initial states being at rest and being in a relativistic motion. Expanding the theoretical formula in terms of the Planck constant ℏ, we obtain the first-order quantum effect on the Larmor radiation. The quantum effect generally suppresses the total radiation energy compared with the prediction of the classical Larmor formula, which is a contrast to the previous work. The reason is explained by the fact that the radiation from a moving charge in a monochromatic electromagnetic plane wave is expressed in terms of the inelastic collisions between an electron and photons of the background electromagnetic waves.
APPLICATION OF COMPUTATIONAL METHODS TO PREDICT ABSORPTION MAXIMA OF ORGANIC DYES USED IN SOLAR CELLS
Authors: ASADOLLAHI-BABOLI M. , MANI-VARNOSFADERANI A.
Published: September 2012

A quantitative structure-property relationship (QSPR) study for the prediction of the absorption maxima (λmax) of organic dyes used in solar cells was carried out using different computational methods. Three-dimensional (3D) descriptors were calculated using Codessa and Dragon softwares to represent the dye molecules. Then, different chemometric tools such as multivariate adaptive regression splines (MARS) and adaptive neuro-fuzzy inference system (ANFIS) combined with Monte Carlo (MC) sampling technique were utilized for selecting the most important descriptors and predicting the absorption maxima of the dyes. Various evaluation techniques such as leave-one-out, leave-multiple-out cross-validation procedures, randomization tests, and validation through the external test set were performed to validate the performance of the model. The results revealed that the calculated absorption maxima values are in good agreement with the experimental ones. This theoretical method provides an accurate and alternative method to obtain λmax of dyes before they are actually synthesized.
PREPARATION AND ELECTROCHEMICAL PERFORMANCE OF HYBRID MATERIALS CONTAINING HETEROPOLY ACID WITH DAWSON STRUCTURE AND POLYMERS
Authors: TONG XIA , WU WEN , ZHOU SHENGMING , WU QINGYIN , CAO FAHE , YAROSLAVTSEV A. B.
Published: September 2012

Highly proton-conducting hybrid materials ( P2W17V /PEG and P2W17V/PEG/SiO2 ) were prepared by heptadecatungstovanadodiphosphoric heteropoly acid with Dawson structure ( P2W17V , 90 wt.%), polyethylene glycol (PEG, 10 wt.% and 5 wt.%) and silica gel ( SiO2 , 0 wt.% and 5 wt.%). The products were characterized by the infrared (IR) spectrum, X-ray powder diffraction (XRD) analysis and electrochemical impedance spectrum (EIS). The result reveals that their conductivity values are 1.02 × 10-2 and 2.58 × 10-2S ⋅ cm-1 at room temperature (26°C) and 75% relative humidity (RH), respectively. Their conductivities increase with higher temperature and these activation energies of proton conduction are 9.51 and 14.95 kJ⋅mol-1, which are lower than that of pure heteropoly acid (32.23 kJ⋅mol-1). These mechanisms of proton conduction for these two materials are Grotthuss mechanism.
MICROSTRUCTURES AND PIEZOELECTRIC PROPERTIES OF KNNLST DOPING BCZT LEAD-FREE CERAMICS
Authors: XU WEI , LI YANG , FENG JIAN-MIN , DAI YE-JING
Published: September 2012

In this study, lead-free piezoelectric ceramics ( Na0.52K0.44Li0.04 )( Nb0.88Sb0.08Ta0.04 ) O3 -doped 0.52 Ba ( Zr 0.2 Ti 0.8) O 3-0.48( Ba 0.7 Ca 0.3) TiO 3( BCZT -x KNNLST ) are investigated. The effects of the KNNLST addition on the microstructures and the electrical properties of the ceramics sintered at the temperature as low as 1350°C are studied. The X-ray diffraction data show that the addition of KNNLST could diffuse into BCZT lattice and a pure perovskite phase is formed. With the increase of KNNLST addition, the average grain size is first increased and afterwards decreased. The ceramics with x = 0.005 exhibit a good piezoelectric behavior of d 33 ~ 464 pC/N and k p ~ 0.44 after three month's aging, which indicates the BCZT -x KNNLST ceramics could be promising for lead-free practical applications.
SEARCHING FOR A DARK MATTER COUPLING TO THE STANDARD MODEL WITH A STUECKELBERG EXTENSION
Authors: DOS SANTOS A. L. , HADJIMICHEF D.
Published: September 2012

We investigate a double extension to the Standard Model (SM). A first extension introduces, via minimal coupling, a massive Z′ boson. This enlarged SM is coupled to a dark matter sector through the Stueckelberg mechanism by a A′ boson. However, the A′ boson does not interact directly with the SM fermions. In our study, we found that the A′ is a massless photon-like particle in dark sector. Constraints on the mass for Z′ and corrections to Z mass are obtained.
RADIAL PULSATIONS OF HYBRID NEUTRON STARS
Authors: VÁSQUEZ FLORES C. , LENZI C. H. , LUGONES G.
Published: September 2012

In this work we investigate the adiabatic radial oscillations of hybrid stars. We use a relativistic-mean-field model equation of state (EOS) to describe the hadron phase and the Nambu-Jona-Lasinio (NJL) model for the quark matter phase. We integrate the equations of relativistic radial oscillations using different parameterizations for the NJL model and investigate the effect of a first order hadron-quark phase transition on the fundamental oscillation mode. The results show that the period τ of the fundamental mode is characterized by a cusp on the maximum mass and is finite for some configurations beyond the maximum mass. We conclude that for hybrid stars with sharp discontinuities the standard stability criterion ∂M/∂εc > 0 is not coincident with the stability criterion based on the finiteness of τ.
C I 5380 Å: A SPECTRAL LINE WITH LOW INFLUENCE FROM STARSPOTS DYNAMICS AND MAGNETIC CYCLES
Authors: SOUTO D. , DO NASCIMENTO J. D.
Published: September 2012

In the Sun-as-a-star Project, the sun was observed spectroscopically and photometrically for more than 25 years in order to determine variability and luminosity changes. This project detected systematic longterm decrease in the total irradiance as a consequence of the solar magnetic activity cycle (scale of years) and variability on solar activity from a time scale of days-months. The solar magnetic activity cycles could mimic the radial velocity modulation signal of a long-period companion in several spectral lines. This effect is an important limitation for the exoplanet searches programs using the radial velocity technique. The Lomb-Scargle periodogram analysis of the Sun-as-a-star spectroscopic data shows that the photospheric line C I 5380 Å and other 11 lines seems to not show significant influence from the rotational or cromospheric magnetic activity modulation. Thus, our analysis suggest that C I 5380 Å line could be used in programs that require extremely line stability.
AN EFFECTIVE THEORY FOR NUCLEAR MATTER WITH GENUINE MANY-BODY FORCES
Authors: VASCONCELLOS CÉSAR A. Z. , HORVATH JORGE , HADJIMICHEF DIMITER , GOMES ROSANA O.
Published: September 2012

Nuclear science has developed many excellent descriptions that embody various properties of the nucleus, and nuclear matter at low, medium and high densities. However, a full microscopic understanding of nuclear systems is still lacking. The aim of our theoretical research group is to shed some light on such challenges and particularly on open questions facing the high density nuclear many-body problem. Here we focus our attention on the conceptual issue of naturalness and its role in shaping the baryon-meson phase space dynamics in the description of the equation of state (EoS) of nuclear matter. In particular, in order to stimulate possible new directions of research, we discuss relevant aspects of a recently developed relativistic effective theory for nuclear matter with natural parametric couplings and genuine many-body forces. Among other topics we discuss in this work the connection of this theory with other known effective QHD models of the literature and its potentiality in describing a new physics for dense matter.
A CALCULATION OF THE J/ψ Ds Ds FORM FACTOR
Authors: OSÓRIO RODRIGUES B. , BRACCO M. E. , CHIAPPARINI M.
Published: September 2012

The form factor and the coupling constant of the vertex J/ψDs Ds was calculated using the QCD Sum Rules. We have considered the cases where the J/ψ and Ds mesons are off-shell.
J/ψ DECAY IN THE C3P0 MODEL
Authors: DE QUADROS J. N. , HADJIMICHEF D.
Published: September 2012

The Fock-Tani representation, is a field theoretic formalism to treat problems involving both composite particles and their constituents. The application of the Fock-Tani transformation to a pair creation Hamiltonian produces the characteristic expansion in powers of the wave function. In lowest order of this expansion, we obtain the model known in the literature: the 3P0 model. In higher orders, the Corrected 3P0 model (C3P0) is obtained by introducing the bound state kernel. In this work, we use the C3P0 model to calculate the J/ψ decay rates in the following channels: ρ π, ω η, ω η′, K*+ K-, [Formula: see text], ϕ η, ϕ η′. We consider that the J/ψ is a mixture given by [Formula: see text].
STT-RAM CELL DESIGN CONSIDERING MTJ ASYMMETRIC SWITCHING
Authors: ZHANG YAOJUN , WEN WUJIE , CHEN YIRAN
Published: September 2012

As one promising candidate for next-generation nonvolatile memory technologies, spin-transfer torque random access memory (STT-RAM) has demonstrated many attractive features, such as nanosecond access time, high integration density, nonvolatility, and good CMOS process compatibility. In this paper, we address the asymmetry in the write operations of STT-RAM cells: the mean and the deviation of the write latency for the switching from low- to high-resistance state is much longer or larger than that of the opposite direction. Some special design concerns, e.g., the data-dependent write reliability, are raised by this observation. We systematically analyze the root reasons for the asymmetric switching of MTJs, including the thermal-induced statistical MTJ magnetization process, the asymmetric biasing condition of NMOS transistors, and the device variations of both NMOS and MTJ. Their impacts on STT-RAM write operations were also investigated. At last, we explore the design spaces of different STT-RAM cell structures by considering the asymmetry of write operations.
Preparation and Characterization of Ba(ZrxTi1-x)O3 Thin Films Using Reactive Sputtering Method
Authors: Kim Jin Woong , Osumi Tsuyoshi , Mastuoka Masashi , Tai Takeshi , Nishide Masamichi , Funakubo Hiroshi , Shima Hiromi , Nishida Ken , Yamamoto Takashi
Published: September 2012

Ba(Zr
x
Ti1-x
)O3 (BZT) thin films with different Zr contents were deposited on (100) MgO and (100) Pt/(100) MgO substrates by RF-magnetron reactive sputtering using metal targets. The BZT (0 < x < 0.89) thin films had a single perovskite phase with only (001)/(100) orientation. In all cases, the ratio of Ba/Ti was stoichiometric according to X-ray fluorescence spectrometry (WDX) measurement. Atomic force microscopy (AFM) study proved that BZT films possess a dense microstructure without cracks or voids. The grain size was found to decrease with increasing of Zr content. The effect of Zr content on the dielectric constant and leakage current was studied. BZT thin films showed ferroelectric-to-paraelectric properties with increasing Zr content and excellent leakage properties according to measurements of electrical properties. These results indicated that we succeeded in depositing high-quality and low-sputter-damage BZT thin films by reactive sputtering using metal targets.
Cross-Section Analysis by Electron Backscatter Diffraction of Textured BaTiO3 Thick Films Prepared by Screen Printing
Authors: Sakai Yuichi , Futakuchi Tomoaki
Published: September 2012

Cross sections of textured BaTiO3-based thick films prepared by screen printing were successfully analyzed by electron backscatter diffraction and scanning electron microscopy. The textured thick films were prepared by repeating the screen printing and firing processes three times. During the firing of the third layer, the calcined powder formed round particles that were integrated into the grain. The results of crystal direction map analysis of the cross sections of the thick films showed that the degree of <100> orientation increased as the firing time increased. This tendency agrees with the change in the value of the Lotgering factor. Many 111 double twins were observed in the textured thick films, which may have facilitated the formation of the textured BaTiO3 thick film.
Piezoelectric, Dielectric, and Structural Properties of Ternary (K0.5Na0.5)Nb0.95O3–BaTiO3–BaZrO3Thin Films Prepared on Pt/TiOx/SiO2/Si Substrates by the Chemical Solution Deposition Method
Authors: Shiraki Hiroshi , Hirose Sakyo , Kageyama Keisuke , Ieki Hideharu
Published: September 2012

Well-controlled polycrystalline (1-x-y)(K0.5Na0.5)Nb0.95O3–xBaTiO3–yBaZrO3(KNN–BTO–BZO; 0≤x,y≤0.1) thin films were systematically synthesized on Pt/TiOx/SiO2/Si substrates by the chemical solution deposition (CSD) method in order to improve the piezoelectric properties by the formation of the morphotropic phase boundary (MPB). The synthesized thin films exhibited excellent insulated resistance and ferroelectric properties. Experimental results indicated that the tetragonal structure was fabricated in the range of at least 0.05≤x≤0.1 in (1-x)KNN–xBTO, whereas the rhombohedral structure was not formed at room temperature in the range of 0≤y≤0.1 in (1-y)KNN–yBZO thin films. Therefore, the desired MPB between tetragonal and rhombohedral structures was not formed in the fabricated KNN–BTO–BZO thin films, which hinders the improvement in the piezoelectric property ofd33*from that of (K0.5Na0.5)Nb0.95O3. This finding demonstrates that the original composition control with the consideration of the effects of the strain from substrate and the small grain size is indispensable for further improvement in the piezoelectric properties of KNN thin films.
Fabrication of 100-Oriented (Na0.5K0.5)NbO3–BaZrO3–(Bi0.5Li0.5)TiO3Films on Si Substrate Using LaNiO3Layer
Authors: Nakao Tomohiro , Yamazoe Seiji , Fukada Masaki , Komaki Kazuki , Noda Toshinari , Adachi Hideaki , Wada Takahiro
Published: September 2012

0.92(Na0.5K0.5)NbO3–0.06BaZrO3–0.02(Bi0.5Li0.5)TiO3(NKN–BZ–BLT) thin films were fabricated by pulsed laser deposition (PLD) on a (100)Si substrate on which a 100-oriented LaNiO3(LNO) bottom layer was fabricated by the chemical solution deposition method. The NKN–BZ–BLT films were characterized by X-ray diffraction (XRD) analysis, θ/2θ scan and ψ–2θ/ω scan, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The properties were compared with those of the NKN–BZ–BLT film deposited on the (111)Pt/Ti/SiO2/(100)Si substrate. We demonstrated that the LNO layer plays an important role in obtaining 100-oriented NKN–BZ–BLT films on the Si substrate. SEM surface and cross-sectional images showed that the NKN–BZ–BLT films fabricated at a substrate temperature of 800 °C had a high density and a relatively smooth surface. From the TEM image, this NKN–BZ–BLT film fabricated at 800 °C was composed of the columnar grains and some vertical-long pores could be observed. The energy dispersive X-ray (EDX) analysis showed that the LNO layer is decomposed to La2NiO4by its reaction with Nb. The dielectric properties showed that the NKN–BZ–BLT film on the LNO electrode had a small dielectric constant of 82, compared with the NKN–BZ–BLT film (εr= 3127) on the (111)Pt/Ti/SiO2/(100)Si substrate. This difference is due to the polarization direction of the film and the polarization axis of the NKN–BZ–BLT film on the LNO electrode exists in a direction perpendicular to the surface of the substrate. However, the NKN–BZ–BLT film on LNO showed a smallPrvalue. This is due to the dispersion of Ni from the LNO layer.
Fabrication of (Bi,Pr)(Fe,Mn)O3 Thin Films on Polycrystalline Diamond Substrates by Chemical Solution Deposition and Their Properties
Authors: Kawae Takeshi , Kawasaki Hiroki , Nakajima Takashi , Tokuda Norio , Okamura Soichiro , Morimoto Akiharu , Takano Yoshihiko
Published: September 2012

(Bi,Pr)(Fe,Mn)O3 (BPFM) thin films were deposited on the conductive B-doped diamond coated polycrystalline diamond substrates by chemical solution deposition method. BPFM thin films were crystallized with random orientation on the polycrystalline diamond. The BPFM/B-doped diamond layered film showed polarization vs electric field (P–E) hysteresis loops without any influences of leakage current at room temperature. The remnant polarization 2P
r and the coercive field 2E
c at the maximum electric field of 1000 kV/cm were 135 µC/cm2 and 700 kV/cm, respectively. In the range of room temperature to 130 °C, the prepared film capacitor showed saturated-loop shape in the P–E curve without influences of leakage current.
Effects of A-Site Occupancy of Bismuth Ions on the Dielectric Tunable Properties of Pyrochlore Bismuth Zinc Niobate Films
Authors: Nakajima Mitsumasa , Yamada Tomoaki , Okaura Shingo , Funakubo Hiroshi
Published: September 2012

The A-site composition dependence of cubic pyrochlore Bi–Zn–Nb–O (BZN) thin films of dielectric tunable properties was investigated. (111)-textured BZN films with a wide range of Bi/Nb ratios (0.62–1.26) were fabricated by metal organic chemical vapor deposition. Raman spectral analysis revealed that by changing the Bi/Nb ratio in BZN films, the Bi concentration of the A-site mainly varied. Dielectric constant and dielectric tunability were found to increase with increasing Bi ion occupancy of the A site. These experimental findings suggest that the Bi occupancy of A site is an important factor for designing Bi based pyrochlore dielectric tunable materials.
Composition Dependence of Piezoelectric Properties of Pb(Zr,Ti)O3Films Prepared by Combinatorial Sputtering
Authors: Tomioka Kohei , Kurokawa Fumiya , Yokokawa Ryuji , Kotera Hidetoshi , Adachi Kazuhiko , Kanno Isaku
Published: September 2012

We examined the composition and orientation dependences of the piezoelectric properties by combinatorial sputtering. PbTiO3and PbZrO3were simultaneously sputtered to prepare composition gradient Pb(Zr,Ti)O3(PZT) films on Pt/Ti/Si substrates, and an almost linear composition gradient was observed in a range of Zr/(Zr+Ti) ratios from 0.33 to 0.76. Dielectric and piezoelectric properties attained maximum at the Zr/Ti composition close to the morphotropic phase boundary (MPB), which is consistent with that of PZT ceramics. 100-oriented PZT films showed a higher dielectric constant than the PZT films with the other orientations, while the PZT films with 111 + 100 mixed orientation showed larger values ofe31f. These results suggest that thea-axis orientation is dominant in the 100-oriented PZT films. In this study, we demonstrated that the combinatorial sputtering method enables the precise evaluation of the composition dependence of piezoelectric and dielectric properties.
Strain-Induced Electrical Properties of Lead Zirconate Titanate Thin Films on a Si wafer with Controlled Oxide Electrode Structure
Authors: Ohno Tomoya , Ishiduka Masaaki , Arai Takashi , Yanagida Hiroaki , Matsuda Takeshi , Sakamoto Naonori , Wakiya Naoki , Suzuki Hisao
Published: September 2012

This paper shows the electrical properties of ferroelectric thin films with large compressive residual stress. In this study, the large compressive strain was applied to lead zirconate titanate (PZT) thin films by designing the bottom electrode structure on a Si wafer. The materials selected for the bottom electrode were lanthanum nickel oxide (LNO) and lanthanum strontium cobalt oxide [LSCO; (La0.5Sr0.5)CoO3] from the viewpoint of thermal expansion coefficients. As a result, the PZT thin films with morphotropic phase boundary (MPB) composition received compressive residual stress up to approximately 0.8 GPa from the bottom electrode even on a Si wafer. The compressive residual stress concomitantly increased with increasing LSCO layer thickness. In addition, the remanent polarization of the PZT thin films increased with increasing compressive residual stress.
Film Thickness Dependence of Crystal Structure in 100-Oriented Epitaxial Pb(Zr0.65Ti0.35)O3 Films Grown on Single-Crystal Substrates with Different Thermal Expansion Coefficients
Authors: Ehara Yoshitaka , Yasui Shintaro , Ishii Koji , Funakubo Hiroshi
Published: September 2012

100-oriented epitaxial Pb(Zr0.65Ti0.35)O3 films with various film thicknesses from 0.1 to 3 µm were grown on (100)
c
SrRuO3 ∥ (100)SrTiO3 and (100)
c
SrRuO3 ∥ (100)LaNiO3 ∥ (001)CaF2 substrates. The out-of-plane/in-plane lattice parameter ratio of the films on the CaF2 substrates was larger than that on the SrTiO3 substrates up to 1.1 µm film thickness, while (90°-α) (α was defined as the internal tilt angle) was almost 0°. Results of analysis of Raman spectra and piezoresponse images suggest that the 1.1-µm-thick film grown on the (100)
c
SrRuO3 ∥ (100)LaNiO3 ∥ (001)CaF2 substrate had tetragonal symmetry with a polar-axis orientation. Moreover, the saturation polarization values of the films measured from P–E hysteresis loops correspond to the two P
s values estimated from the thermodynamic theory, assuming the change in the polar direction due to the symmetry change to tetragonal, and from the crystal distortion in tetragonal symmetry. This can be explained by the large compressive stress from the CaF2 substrate having a large thermal expansion coefficient.
Polarization Properties of Bismuth Strontium Tantalate Ceramic Films Deposited by Aerosol Deposition Method
Authors: Suzuki Muneyasu , Nishihara Yoshiya , Uesu Yoshiaki , Akedo Jun
Published: September 2012

We report aerosol deposition (AD) method for preparation of bismuth layer-structured ferroelectric thick films with enhanced ferroelectric and insulating properties. Constitution phase, crystal structure, polarization and leakage current properties of SrBi2Ta2O9 (SBTa) thick films with thickness of 2–4 µm were investigated. While obtained as-deposited SBTa films have slight c-axis grain orientation, the degree of orientation for the films annealed at higher than 1000 °C was the same as that for sintered bulks. Fracture cross-sectional scanning electron microscopy (SEM) images revealed that the as-deposited SBTa films on glass substrates had a fully dense microstructure. The low leakage current density (J) of less than 10-7 A/cm2 at 1 MV/cm was observed for SBTa films annealed at less than 900 °C, and the SBTa films annealed at 900 °C indicated a remanent polarization (P
r) of 5.7 µC/cm2, which is larger than that of sintered bulks (P
r of 4.7 µC/cm2) fabricated by conventional solid-state reaction using the same starting raw powder used for the AD method.
Thermally Stimulated Current Analysis of Defects in Sol–Gel Derived SrTa2O6 Thin-Film Capacitors
Authors: Lu Li , Nishida Takashi , Echizen Masahiro , Ishikawa Yasuaki , Uchiyama Kiyoshi , Shiosaki Tadashi , Uraoka Yukiharu
Published: September 2012

In this research, we demonstrated that defect states in sol–gel-derived SrTa2O6 (STA) thin films can be detected by a thermal simulated current (TSC) technique. We also tentatively explained leakage current properties using these defect states. Similar defect states were found in STA thin films that were annealed at 700 and 800 °C by the TSC technique. Defects that caused the TSC peak at measurement temperatures of 130–150 °C showed higher trap densities in the 800 °C-annealed STA thin film. These defects were likely to be caused by diffused Ti, which mainly contributed to the larger leakage current in the 800 °C-annealed STA thin film. Oxygen-vacancy-related defect states were also clearly observed with the change in measurement atmosphere from air to vacuum.
Investigation of Sputtering Damage in SrRuO3 Films Prepared by Sputtering with Raman and X-ray Photoemission Spectroscopies
Authors: Tai Takeshi , Nishide Masamichi , Matsuoka Masashi , Kamo Takafumi , Funakubo Hiroshi , Katoda Takashi , Shima Hiromi , Nishida Ken , Yamamoto Takashi
Published: September 2012

Sputtering damage of SrRuO3 (SRO) films prepared by RF magnetron sputtering under various growth pressures was investigated by Raman spectroscopy and X-ray photoemission spectroscopy (XPS). Phonon modes that were related to Ru and Sr ions changed and XPS spectra shifted with decreasing growth pressure. These results indicate that Sr ions switched place with Ru ions in SRO films when the SRO films had sputtering damage under low-growth-pressure sputtering condition as determined from Raman spectroscopy and XPS measurement. The antisite ion content increased with decreasing growth pressure. The resistivity of the SRO films also increased with increasing antisite ion content. The dynamics of sputtering damage revealed that the antisite Sr and Ru ions were formed in SRO films.
Ferroelectricity and Ferromagnetism of BaTiO3/BaFeO3 Superlattice Thin Films
Authors: Fukatani Ryosuke , Yokota Hiroko , Ogura Shingo , Uesu Yoshiaki , Bartasyte Ausrine , Fukunaga Mamoru , Noda Yukio
Published: September 2012

Ferroelectric BaTiO3 and antiferromagnetic BaFeO3 are deposited alternatively by a pulsed laser deposition method with the aim of fabricating room-temperature multiferroic materials. X-ray diffraction (XRD) analysis reveals that the superlattice structure is fabricated with a designed periodicity and thin film quality is improved by increasing BaFeO3 layers. Ferroelectricity and ferromagnetic properties are examined by the double-wave method (DWM) of D–E hysteresis loops, an XRD dilatometry, and a superconducting quantum interference device magnetometer. Our superlattice thin film shows multiferroicity, i.e., the coexistence of ferroelectricity and ferromagnetism, at room temperature.
Structural and Ferroelectric Properties of Domain-Structure-Controlled BiFeO3 Thin Films Prepared by Dual-Ion-Beam Sputtering
Authors: Nakashima Seiji , Fujisawa Hironori , Tsujita Yosuke , Seto Shota , Kobune Masafumi , Shimizu Masaru
Published: September 2012

BiFeO3 (BFO) thin films have been grown on vicinal SrTiO3 (STO) (001) substrates by dual-ion-beam sputtering. The Bi/Fe composition ratio was optimized by adjusting the beam current ratio of a dual-ion beam. The domain structure was controlled using a vicinal STO substrate along <100> and <110>. From the results of X-ray diffraction analysis and piezoelectric force microscopy, it is found that BFO thin films grown on vicinal STO along <100> and <110> show stripe and single-domain structures, respectively. It is found that the reduction in the length of non-180° domain walls improves leakage current characteristics, resulting in an enhancement of ferroelectric D–E characteristics. The single-domain BFO thin film shows excellent D–E hysteresis loops at room temperature, with a double remanent polarization (2P
r) and a double coercive field (2E
c) of 140 µC/cm2 and 340 kV/cm, respectively.
Thickness Dependence of Extrinsic Dielectric Response in Reduced Ni-Doped KTaO3
Authors: Tsukada Shinya , Akishige Yukikuni
Published: September 2012

The dielectric response of reduced 1.0 mol %-Ni-doped KTaO3 single crystals was studied to determine the mechanism of the high dielectric constant of 160000, with a low dielectric loss of less than 0.1. The dielectric constant depends on the sample thickness, sample color, and electrode material. The obtained results strongly support the existence of a Schottky barrier at the interface between the crystal and electrodes, and we deduce that a large number of free electrons are essential for inducing the extrinsic dielectric effect.
Fabrication and Characterization of Dielectric Nanocube Self-Assembled Structures
Authors: Mimura Ken-ichi , Kato Kazumi , Imai Hiroaki , Wada Satoshi , Haneda Hajime , Kuwabara Makoto
Published: September 2012

Orderly assemblies of BaTiO3 (BT) cube-shaped nanocrystals (nanocubes) and BT–SrTiO3 (ST) mixture nanocubes were fabricated on Pt-coated Si substrates directly by capillary-force-assisted solution self-assembly and heat treatment. These dielectric nanocubes aligned face to face in quite a wide region of 10×50 µm2 on the average with a height of 1 µm. The local microstructure of the nanocube assembly was observed by high-resolution transmission electron microscopy. It was revealed that the lattice strain at the interface of the neighboring nanocubes was locally induced. The piezoresponse of the BT–ST mixture nanocube assembly showed a nonlinear curve and a stepwise behavior at a high poling field, which differed from the ferroelectric BT and paraelectric ST assemblies investigated by scanning probe microscopy. The characteristic behavior might be attributed to the interfacial lattice strain in mixture assemblies.
Percolative BaTiO3/Carbon-Nanotube Composite Films Employing Aerosol Deposition
Authors: Kim Yoon-Hyun , Osada Minoru , Kim Hong-Ki , Nam Song-Min
Published: September 2012

Percolative BaTiO3/multiwalled carbon nanotube (MWNT) composite thick films were developed using an aerosol deposition (AD) process at room temperature. Well-dispersed mixed powders with various volume ratios were utilized as the starting powders for AD, and dense BaTiO3/MWNT composite thick films were successfully fabricated with the starting mixed powders with 0.01 vol % MWNTs. The existence of MWNTs in the composite films was confirmed using Raman spectroscopy. The composite films show a high relative dielectric constant (657 at 1 kHz), which is approximately 7 times larger than that (91 at 1 kHz) of the BaTiO3 films. In addition, the strong frequency dispersion of the dielectric constant in the low-frequency range was confirmed for the composite films. The dielectric properties of the composite films were investigated using the dielectric mechanism used in percolative composites.
High-Power Piezoelectric Characteristics of C-Axis Crystal-Oriented (Sr,Ca)2NaNb5O15 Ceramics
Authors: Shimizu Hiroyuki , Doshida Yutaka , Mizuno Youichi , Tanaka Satoshi , Uematsu Keizou , Tamura Hideki
Published: September 2012

The high-power piezoelectric characteristics of c-axis crystal-oriented (Sr,Ca)2NaNb5O15 (SCNN) ceramics were studied by the constant-motional-current driving method, and compared with those of the randomly oriented ceramics superior to those of hard Pb(Ti,Zr)O3 (PZT) ceramics. The c-axis crystal-oriented SCNN ceramic showed a large Lotgering factor of 0.98. The effective piezoelectric constant d
33
* was 260 pm/V, as large as those of hard PZT ceramics. In the 31-mode of the rectangular plate, the quality factor, Q, was five times larger than that of the randomly oriented ceramic, and almost constant at approximately 3300 up to the maximum vibration velocity of 1.84 m/s rms. The resonant frequency change was also stable up to a vibration velocity of 1.84 m/s rms. The change was approximately +0.05% in the driving range, which was much smaller than that of +0.8% of the randomly oriented ceramic. The high-power piezoelectric characteristics were also clarified by a comparison with the mechanical characteristics. Therefore, the highly c-axis crystal-oriented SCNN ceramics are good candidates for high-power piezoelectric applications in comparison with hard PZT ceramics.
Grain-Size-Controlled (Li,Na,K)NbO3 Ceramics Using Powder Source Classified by Centrifugal Separator
Authors: Kakimoto Ken-ichi , Kaneko Ryosuke , Kagomiya Isao
Published: September 2012

A model experiment on the grain-size-related dielectric and ferroelectric properties of lead-free Li0.04(Na0.50K0.50)0.96NbO3 piezoelectric ceramics has been carried out. Firstly, the size classification of calcined powders was achieved by a wet-type centrifugal separation technique to obtain size-classified powders with different mean particle sizes. Then, spark plasma sintering (SPS) under an identical condition at 960 °C for 10 min at a pressure of 80 MPa was performed for the size-classified powder sources to synthesize dense ceramics and control their mean grain sizes so that they ranged from 500 nm to approximately 5 µm. The results clearly allowed the distinguishing of different dielectric and ferroelectric properties on the basis of grain size. By increasing the grain size from 0.5 to 2.8 µm, the remanent polarization P
r gradually increases from 4.2 to 16.8 µC/cm2, but a further increase in grain size to 4.8 µm causes a decrease in P
r to 9.2 µC/cm2, while the coercive field E
c tends to increase with decreasing grain size. Our findings and the new technique to control grain size may stimulate further systematic investigation of grain-size-related properties for the development of lead-free alkali niobate piezoelectric ceramics showing excellent electrical properties.
Effect of Polymer Stabilization on Molecular Alignment of Ferroelectric Liquid Crystal in Wide-Gap Cell
Authors: Furue Hirokazu , Tanaka Daichi , Akaogi Junichi
Published: September 2012

We have investigated the molecular alignment structure of ferroelectric liquid crystals (FLCs) in a wide-gap cell for application to optical devices, such as an electrically controlled lens. The transformation of the smectic layer structure has been observed under an electric field, particularly under a low electric field in the wide-gap cell. We have attempted to suppress this transformation, which considerably degrades the optical performance of FLCs, by the polymer stabilization technique. As a result, we have found that the layer transformation can be suppressed successfully. However, the disarray of the FLC molecular alignment may occur owing to the deformation of polymer networks accompanied by FLC molecular reorientation caused by the application of an electric field.
Measurements of Acoustical Physical Constants of La3Ta0.5Ga5.3Al0.2O14 Single Crystals at High Temperatures
Authors: Karaki Tomoaki , Lv Tao , Adachi Masatoshi , Ohashi Yuji , Arakawa Mototaka , Kushibiki Jun-ichi
Published: September 2012

The dielectric, elastic, and piezoelectric constants of langasite family single-crystal La3Ta0.5Ga5.3Al0.2O14 (LTGA) were measured by combing plane-wave ultrasonic microspectroscopy (PW-UMS) technology with the resonance–antiresonance method in a range from room temperature to 1000 °C. The influence of dielectric loss at high temperatures on resonance and antiresonance frequencies was discussed. At room temperature, the piezoelectric constants d
11 and d
14 were 6.62 and -4.65 pC/N, respectively. d
11 increased to 7.5 pC/N at 1000 °C. The electromechanical coupling factor k
12 was about 16.8% in the entire temperature range. All the necessary parameters of the LTGA crystal for acoustic wave applications at high temperatures were determined in this research.
Identicalness between Piezoelectric Loss and Dielectric Loss in Converse Effect of Piezoelectric Ceramic Resonators
Authors: Hagiwara Manabu , Hoshina Takuya , Takeda Hiroaki , Tsurumi Takaaki
Published: September 2012

The relationship between piezoelectric loss (tan δP) and dielectric loss (tan δE) in the converse piezoelectric effect in piezoelectric ceramics was investigated theoretically and experimentally. The theoretical consideration was based on the assumption that strain should be proportional to polarization without phase delay in both the intrinsic contribution due to lattice deformation and the extrinsic contribution due to domain wall motion. It was expected that the piezoelectric loss in the converse piezoelectric effect should be identical to the dielectric loss. In order to experimentally verify the identicalness between the losses, the immittance curves of the piezoelectric response of various Pb(Zr,Ti)O3-based ceramic resonators were fitted if the piezoelectric loss tan δP(1) is equal to zero, (2) exists as the independent variable, and (3) is the same as the dielectric loss tan δE. The observation result clearly proved that tan δPis identical to tan δE. This identicalness was also demonstrated by analyzing the phase angle of vibration velocity in mechanical response.