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Sample records for bulk dielectric polarization

  1. Influence of bulk dielectric polarization upon PD transients

    DEFF Research Database (Denmark)

    Pedersen, Aage; Crichton, George C; McAllister, Iain Wilson

    1995-01-01

    From a field-theoretical approach, it has been possible to develop a physically valid theory of partial discharge transients. The theory is based upon the concept of the charge induced upon the detecting electrode by the partial discharge. This induced charge is shown to be composed of a component...... associated with the actual space charge in the void, and one related to changes in the bulk polarization brought about by changes in the field external to the void due to this space charge. The magnitude of the induced charge and its components are discussed in relation to a heterogeneous bulk dielectric...

  2. Influence of bulk dielectric polarization upon PD transients: Effect of multiple dielectric layers

    DEFF Research Database (Denmark)

    McAllister, Iain Wilson; Crichton - Fratrådt, George C

    1999-01-01

    A physically valid theory of partial discharge transients has been developed using a field-theoretical approach. The theory is based upon the concept of charge induced upon the detecting electrode by the partial discharge. This induced charge can be resolved into a component associated...... with the actual space charge in the void and one related to changes in the polarization δP&oarr; of the bulk dielectric. These changes are brought about by changes in the field external to the void, which in turn are due to the void space charge. The magnitude of the induced charge component due to δ...

  3. Influence of void geometry and bulk dielectric polarization upon PD transients

    DEFF Research Database (Denmark)

    McAllister, Iain Wilson; Crichton, George C

    1998-01-01

    A physically valid theory of partial dischargetransients has been developed using a field theoretical approach. The theory is based upon the concept of the charge induced upon the detecting electrode by the partial discharge. Mathematically this induced charge is composed of a component associated...... with the actual space charge in the void, and one related to changes in the bulk dielectric polarization brought about by the space charge. In the present paper, the influence of the void geometry upon the changes in the bulk dielectric polarization is examined....

  4. Influence of bulk dielectric polarization upon partial discharge transients: Effect of void geometry and orientation

    DEFF Research Database (Denmark)

    McAllister, Iain Wilson; Crichton, G.C.

    2005-01-01

    The induced charge arising from a partial discharge consists of 2 components. One is associated with the actual space charge in the void. The other is related to changes in the polarization of the bulk dielectric. These changes are a direct consequence of the field produced by the space charge. The...

  5. Influence of bulk dielectric polarization and void geometry upon PD transients

    DEFF Research Database (Denmark)

    McAllister, Iain Wilson; Crichton, George C

    The induced charge arising from a partial discharge consists of a component associated with the actual space charge in the void, and one related to changes in the polarization of the bulk dielectric. These changes are brought about by the field produced by the space charge. The influence of the...

  6. Influence of bulk dielectric polarization upon partial discharge transients effect of heterogeneous dielectric geometry

    DEFF Research Database (Denmark)

    McAllister, Iain Wilson; Crichton, George C.

    2000-01-01

    A physically valid theory of partial discharge (PD) transients is based upon the concept of the charge induced upon the detecting electrode by the PD. This induced charge consists of two components. One is associated with the actual space charge in the void, while the other is related to changes......, the magnitude of the induced charge either increases or decreases depending on the ratio of the dielectric permittivities and within which dielectric the void is located. It is shown that this behavior is directly related to the magnitude and polarity of the polarization component of the induced charge...

  7. Influence of system geometry and bulk dielectric polarization upon PD transients

    DEFF Research Database (Denmark)

    Pedersen, Aage; Crichton, George C; McAllister, Iain Wilson

    1996-01-01

    A physically valid theory of partial discharge transients has been developed through a field theoretical approach. The theory is based upon the concept of the charge induced upon the detecting electrode by the partial discharge. This induced charge consists of a component associated with the actual...... space charge in the void, and one related to changes in the polarization of the bulk dielectric. The latter is brought about by changes in the field external to the void due to the void space charge. The magnitude of the induced charge and its components are discussed with reference to a coaxial...

  8. Re-examination of the dielectric spectra of epoxy resins: Bulk charge transport and interfacial polarization peaks

    OpenAIRE

    Chalashkanov, N. M.; Dodd, S J; Dissado, L. A.; Fothergill, J

    2014-01-01

    The dielectric properties of two amine cured bisphenol-A epoxy resin systems, Araldite CY1301 and Araldite CY1311 have been characterized using dielectric spectroscopy over the frequency range 1 mHz to 100 kHz. These two epoxy resin systems were chosen to allow the dielectric response to be studied from above and below the glass transition, as Araldite CY1311 is a modified version (with added plasticizer) of Araldite CY1301. The dielectric response was found to comprise both bulk and interfac...

  9. Bulk dielectric and magnetic properties of PFW-PZT ceramics: absence of magnetically switched-off polarization

    Czech Academy of Sciences Publication Activity Database

    Kempa, Martin; Kamba, Stanislav; Savinov, Maxim; Maryško, Miroslav; Frait, Zdeněk; Vaněk, Přemysl; Tomczyk, M.; Vilarinho, P. M.

    2010-01-01

    Roč. 22, č. 44 (2010), 445902/1-445902/5. ISSN 0953-8984 R&D Projects: GA ČR(CZ) GA202/09/0682 Institutional research plan: CEZ:AV0Z10100520; CEZ:AV0Z10100521 Keywords : dielectric and magnetic properties * ceramics * polarization * phase transitions Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.332, year: 2010

  10. Bulk dielectric and magnetic properties of PFW-PZT ceramics: absence of magnetically switched-off polarization

    International Nuclear Information System (INIS)

    We investigated ceramics samples of solid solutions of [PbFe2/3W1/3O3]x-[PbZr0.53Ti0.47O3]1-x (PFWx-PZT1-x, x = 0.2 and 0.3) by means of broad-band dielectric spectroscopy, differential scanning calorimetry and SQUID magnetometry. We did not confirm the observations of Kumar et al (2009 J. Phys.: Condens. Matter 21 382204), who reported on reversible suppression of ferroelectric polarization in polycrystalline PFWx-PZT1-x thin films for magnetic fields above 0.5 T. We did not observe any change of ferroelectric polarization with external magnetic fields up to 3.2 T. Pirc et al (2009 Phys. Rev. B 79 214114) developed a theory explaining the reported large magnetoelectric effect in PFWx-PZT1-x, taking into account relaxor magnetic and relaxor ferroelectric properties of the system. Our data revealed classical ferroelectric properties below 525 K and 485 K in samples with x = 0.2 and 0.3, respectively. Moreover, paramagnetic behavior was observed down to 4.5 K instead of previously reported relaxor magnetic behavior. It seems that the reported switching-off of ferroelectric polarization in PFWx-PZT1-x thin films is not an intrinsic property, but probably an effect of electrodes, interlayers, grain boundaries or second phases presented in polycrystalline thin films.

  11. Casimir effect in dielectrics: Bulk energy contribution

    International Nuclear Information System (INIS)

    In a recent series of papers, Schwinger discussed a process that he called the dynamical Casimir effect. The key essence of this effect is the change in zero-point energy associated with any change in a dielectric medium. (In particular, if the change in the dielectric medium is taken to be the growth or collapse of a bubble, this effect may have relevance to sonoluminescence.) The kernel of Schwinger close-quote s result is that the change in Casimir energy is proportional to the change in the volume of the dielectric, plus finite-volume corrections. Other papers have called into question this result, claiming that the volume term should actually be discarded, and that the dominant term remaining is proportional to the surface area of the dielectric. In this paper, which is an expansion of an earlier Letter on the same topic, we present a careful and critical review of the relevant analyses. We find that the Casimir energy, defined as the change in zero-point energy due to a change in the medium, has at leading order a bulk volume dependence. This is in full agreement with Schwinger close-quote s result, once the correct physical question is asked. We have nothing new to say about sonoluminescence itself. copyright 1997 The American Physical Society

  12. Partial discharge transients and the influence of dielectric polarization

    DEFF Research Database (Denmark)

    Pedersen, A.; Crichton, George C; McAllister, Iain Wilson

    1996-01-01

    Based on a field-theoretical approach, a physically valid theory of partial discharge transients has been developed. The theory is based upon the concept of the charge induced upon the detecting electrode by the partial discharge. This induced charge is shown to be composed of a component...... associated with the actual space charge in the void, and one related to changes in the bulk polarization due to this space charge. In the present article, the magnitude of the induced charge and its components are investigated for both homogeneous and heterogeneous dielectric systems. In the former void...... shape is considered. In the latter, the void shape is restricted to one of spherical form. For each system the magnitude of the induced charge is found to be strongly influenced by changes in the bulk polarization. In the former, the polarization component depends dramatically on void shape...

  13. Partial discharges and bulk dielectric field enhancement

    DEFF Research Database (Denmark)

    McAllister, Iain Wilson; Johansson, Torben

    A consequence of partial discharge activity within a gaseous void is the production of a field enhancement in the solid dielectric in the proximity of the void. This situation arises due to the charge created by the partial discharges accumulating at the void wall. The influence of the spatial...

  14. Casimir effect in dielectrics Bulk Energy Contribution

    CERN Document Server

    Carlson, C E; Pérez-Mercader, J; Visser, M; Visser, Matt

    1997-01-01

    In a recent series of papers, Schwinger discussed a process that he called the Dynamical Casimir Effect. The key essence of this effect is the change in zero-point energy associated with any change in a dielectric medium. (In particular, if the change in the dielectric medium is taken to be the growth or collapse of a bubble, this effect may have relevance to sonoluminescence.) The kernel of Schwinger's result is that the change in Casimir energy is proportional to the change in volume of the dielectric, plus finite-volume corrections. Other papers have called into question this result, claiming that the volume term should actually be discarded, and that the dominant term remaining is proportional to the surface area of the dielectric. In this communication, which is an expansion of an earlier letter on the same topic, we present a careful and critical review of the relevant analyses. We find that the Casimir energy, defined as the change in zero-point energy due to a change in the medium, has at leading orde...

  15. Partial discharges and bulk dielectric field enhancement

    OpenAIRE

    McAllister, Iain Wilson; Johansson, Torben

    2000-01-01

    A consequence of partial discharge activity within a gaseous void is the production of a field enhancement in the solid dielectric in the proximity of the void. This situation arises due to the charge created by the partial discharges accumulating at the void wall. The influence of the spatial extent of this wall charge upon the maximum field strength in the solid is examined and discussed.

  16. Exchange-Correlation Hole in Polarized Insulators: Implications for the Microscopic Functional Theory of Dielectrics

    International Nuclear Information System (INIS)

    We present a simple and direct proof that the exchange-correlation hole, and therefore the exchange-correlation energy, in a polarized insulator is not determined by the bulk density alone. It is uniquely characterized by the density and the macroscopic electric polarization of the dielectric medium. copyright 1998 The American Physical Society

  17. Wideband Circularly Polarized Dielectric Rod Antenna

    OpenAIRE

    Min Guo; Ji-Jun Yan; Shun-Shi Zhong; Zhu Sun

    2012-01-01

    A new dielectric rod antenna (DRA) is introduced to produce circular polarization (CP) over a wide frequency band without a complex feed network. Along with the simulated results, measured results of the antenna prototype are presented, showing a 3 dB axial ratio (AR) CP bandwidth of 17.7%. The radiation characteristics of the fabricated antenna are also demonstrated showing the measured gain of better than 6.2 dBi. Moreover, the measured impedance bandwidth (VSWR ≤2) reaches 20.1%, from 8.75...

  18. AC Conductivity and Dielectric Relaxation Behavior of Sb2S3 Bulk Material

    Science.gov (United States)

    Abd El-Rahman, K. F.; Darwish, A. A. A.; Qashou, Saleem I.; Hanafy, T. A.

    2016-07-01

    The Sb2S3 bulk material was used for next-generation anode for lithium-ion batteries. Alternative current (AC) conductivity, dielectric properties and electric modulus of Sb2S3 have been investigated. The measurements were carried out in the frequency range from 40 Hz to 5 MHz and temperature range from 293 K to 453 K. The direct current (DC) conductivity, σ DC, shows an activated behavior and the calculated activation energy is 0.50 eV. The AC conductivity, σ AC, was found to increase with the increase of temperature and frequency. The conduction mechanism of σ AC was controlled by the correlated barrier hopping model. The behavior of the dielectric constant, ɛ', and dielectric loss index, ɛ'', reveal that the polarization process of Sb2S3 is dipolar in nature. The behavior of both ɛ' and ɛ'' reveals that bulk Sb2S3 has no ferroelectric or piezoelectric phase transition. The dielectric modulus, M, gives a simple method for evaluating the activation energy of the dielectric relaxation. The calculated activation energy from M is 0.045 eV.

  19. Wideband Circularly Polarized Dielectric Rod Antenna

    Directory of Open Access Journals (Sweden)

    Min Guo

    2012-01-01

    Full Text Available A new dielectric rod antenna (DRA is introduced to produce circular polarization (CP over a wide frequency band without a complex feed network. Along with the simulated results, measured results of the antenna prototype are presented, showing a 3 dB axial ratio (AR CP bandwidth of 17.7%. The radiation characteristics of the fabricated antenna are also demonstrated showing the measured gain of better than 6.2 dBi. Moreover, the measured impedance bandwidth (VSWR ≤2 reaches 20.1%, from 8.75 GHz to 10.7 GHz, while the CP beamwidth (AR ≤3 dB at the central frequency is measured over 120°.

  20. Dihedron dielectric loaded surface plasmon athermal polarization converter.

    Science.gov (United States)

    Hassan, K; Leroy, F; Colas-des-Francs, G; Weeber, J-C

    2014-02-01

    We investigate numerically a novel plasmonic polarization converter relying on the excitation of a so-called dihedron dielectric loaded plasmon polariton. The dihedron dielectric loaded waveguide consists of a dielectric ridge implemented at the inner corner of a metal-coated dielectric step. For a dielectric ridge with a square cross section, the plasmon polariton modes supported by each side of the metallized step hybridize to create supermodes with crossed polarizations. We show that the two supermodes can be operated in a dual-mode interferometer configuration to perform an efficient (24 dB) TE-TM/TM-TE polarization conversion over typical distances below 30 μm at telecommunications wavelengths. In addition, on the basis of the thermo-optical properties of our device, we find that the dihedron plasmonic polarization converter is temperature insensitive. PMID:24487902

  1. Towards all-dielectric, polarization-independent optical cloaks

    DEFF Research Database (Denmark)

    Andkjær, Jacob Anders; Mortensen, N. Asger; Sigmund, Ole

    2012-01-01

    Fully enclosing, all-dielectric cloaks working for both E-z and H-z polarizations simultaneously are presented in this letter. The cloaks are effective for two antiparallel angles of incidence, and the layout of standard dielectric material in the cloak is determined by topology optimization. Sca...

  2. Novel polar dielectrics with the tetragonal tungsten bronze structure

    OpenAIRE

    Andrei ROTARU

    2013-01-01

    There is great interest in the development of new polar dielectric ceramics and multiferroic materials with new and improved properties. A family of tetragonal tungsten bronze (TTB) relaxors of composition Ba₆M³⁺Nb₉O₃₀ (M³⁺ = Ga³⁺, Sc³⁺ and In³⁺, and also their solid solutions) were studied in an attempt to understand their dielectric properties to enable design of novel polar TTB materials. A combination of electrical measurements (dielectric and impedance spectroscopy) and powder diffr...

  3. Polar phonons and dielectric dispersion in relaxor ferroelectrics

    Czech Academy of Sciences Publication Activity Database

    Kamba, Stanislav; Petzelt, Jan

    XX : Penn State University , 2004 - (Trolier-McKinstry, S.; Cross, L.; Yamashita, Y.), s. 257-276 R&D Projects: GA AV ČR KSK1010104 Keywords : relaxor ferroelectrics * polar clusters * dielectric dispersion * neutron scattering Subject RIV: BM - Solid Matter Physics ; Magnetism

  4. PD-related stresses in the bulk dielectric and their evaluation

    DEFF Research Database (Denmark)

    Pedersen, Aage; Crichton - Fratrådt, George C; McAllister, Iain Wilson

    1993-01-01

    The application of electromagnetic field theory to the subject of partial discharges shows that discharging in a void generates large field distortions within the bulk dielectric in the proximity of the void. Such inherent over-stressing of a dielectric could be the effect which triggers the onset...

  5. A New Wideband Circularly Polarized Dielectric Resonator Antenna

    OpenAIRE

    M Khalily; Kamarudin, M. R.; Mokayef, M.; Sh. Danesh; Ghahferokhi, S. E. A.

    2014-01-01

    A wideband and compact circularly polarized (CP) C-shaped dielectric resonator antenna (DRA) is presented. The proposed C-shaped DR is excited by a simple stripe line connected to a coplanar waveguide (CPW) feeding line. The C-shaped DRA is circularly polarized with 19% axial ratio (AR) bandwidth. It is found that the CP bandwidth can be expanded by using a narrow short circuit strip. The final design achieves CP with 50% AR bandwidth. The proposed circularly polarized DRA (CPDRA) with good r...

  6. Polarization beam splitter based on dielectric periodic structure with different EFCs for two polarizations

    Institute of Scientific and Technical Information of China (English)

    Yuan Zhang; Yurong Jiang; Xia Li; Wei Xue

    2008-01-01

    @@ A dielectric multi-layered structure is studied in this letter. It is found that at some frequency ranges, the equal-frequency contours (EFCs) are almost flat for one polarization but still curve for the other. Based on this property, we propose a novel polarization beam splitter.

  7. Alternating-current conductivity and dielectric relaxation of bulk iodoargentate

    Energy Technology Data Exchange (ETDEWEB)

    Duan, Hai-Bao, E-mail: duanhaibao4660@163.com; Yu, Shan-Shan; Zhou, Hong

    2015-05-15

    Graphical abstract: The electric modulus shows single dielectric relaxation process in the measured frequency range. - Highlights: • The conduction mechanism is described by quantum mechanical tunneling model. • The applications of dielectric modulus give a simple method for evaluating the activation energy of the dielectric relaxation. • The [Ag{sub 2}I{sub 4}]{sup 2−}1-D chain and [Cu(en){sub 2}]{sup 2+} cation column form the layered stacks by hydrogen bond interactions. - Abstract: An inorganic-organic hybrid compound Cu(en){sub 2}Ag{sub 2}I{sub 4} (en = ethylenediamine) (1) was synthesized and single crystal structurally characterized. Along the [001] direction, the inorganic parts form an infinite 1-D chain and [Cu(en){sub 2}]{sup 2+} cations are separated by inorganic chain. The electrical conductivity and dielectric properties of 1 have been investigated over wide ranges of frequency. The alternating-current conductivities have been fitted to the Almond–West type power law expression with use of a single value of S. It is found that S values for 1 are nearly temperature-independent, which indicates that the conduction mechanism could be quantum mechanical tunneling (QMT) model. The dielectric loss and electric modulus show single dielectric relaxation process. The activation energy obtained from temperature-dependent electric modulus compare with the calculated from the dc conductivity plots.

  8. Existence conditions for bulk large-wavevector waves in metal-dielectric and graphene-dielectric multilayer hyperbolic metamaterials

    DEFF Research Database (Denmark)

    Zhukovsky, Sergei; Andryieuski, Andrei; Lavrinenko, Andrei; Sipe, J. E.

    2014-01-01

    We theoretically investigate general existence conditions for broadband bulk large-wavevector (high-k) propagating waves (such as volume plasmon polaritons in hyperbolic metamaterials) in arbitrary subwavelength periodic multilayers structures. Treating the elementary excitation in the unit cell ...... metamaterials, optical waveguide arrays, 2D plasmonic and acoustic metamaterials.......We theoretically investigate general existence conditions for broadband bulk large-wavevector (high-k) propagating waves (such as volume plasmon polaritons in hyperbolic metamaterials) in arbitrary subwavelength periodic multilayers structures. Treating the elementary excitation in the unit cell of......-dielectric and recently introduced graphene-dielectric stacks. We confirm that short-range surface plasmons in thin metal layers can give rise to hyperbolic metamaterial properties and demonstrate that long-range surface plasmons cannot. We also show that graphene-dielectric multilayers tend to support high...

  9. Invited Article: Broadband highly efficient dielectric metadevices for polarization control

    Science.gov (United States)

    Kruk, Sergey; Hopkins, Ben; Kravchenko, Ivan I.; Miroshnichenko, Andrey; Neshev, Dragomir N.; Kivshar, Yuri S.

    2016-06-01

    Metadevices based on dielectric nanostructured surfaces with both electric and magnetic Mie-type resonances have resulted in the best efficiency to date for functional flat optics with only one disadvantage: a narrow operational bandwidth. Here we experimentally demonstrate broadband transparent all-dielectric metasurfaces for highly efficient polarization manipulation. We utilize the generalized Huygens principle, with a superposition of the scattering contributions from several electric and magnetic multipolar modes of the constituent meta-atoms, to achieve destructive interference in reflection over a large spectral bandwidth. By employing this novel concept, we demonstrate reflectionless (˜90% transmission) half-wave plates, quarter-wave plates, and vector beam q-plates that can operate across multiple telecom bands with ˜99% polarization conversion efficiency.

  10. Broadband highly-efficient dielectric metadevices for polarization control

    CERN Document Server

    Kruk, Sergey; Kravchenko, Ivan; Miroshnichenko, Andrey; Neshev, Dragomir N; Kivshar, Yuri S

    2016-01-01

    Metadevices based on dielectric nanostructured surfaces with both electric and magnetic Mie-type resonances have resulted in the best efficiency to date for functional flat optics with only one disadvantage: narrow operational bandwidth. Here we experimentally demonstrate broadband transparent all-dielectric metasurfaces for highly efficient polarization manipulation. We utilize the generalized Huygens principle with a superposition of the scattering contributions from several electric and magnetic multipolar modes of the constituent meta-atoms to achieve destructive interference in reflection over a large spectral bandwidth. By employing this novel concept, we demonstrate reflectionless (~90% transmission) half-wave plates, quarter-wave plates, and vector beam q-plates that can operate across multiple telecom bands with ~99% polarization conversion efficiency.

  11. Circularly polarized dielectric resonator antenna excited by a conformal wire

    OpenAIRE

    Khamas, S.K.

    2008-01-01

    A conformal spiral wire has been used to feed a dielectric resonator antenna to obtain a circular polarization. The parameters of the spiral have been optimized numerically so that minimum axial ratio (AR) and return losses are achieved. The method of moments (MoM) has been used in the analysis and the results have been validated against those from a commercial software package with a good agreement.

  12. A New Wideband Circularly Polarized Dielectric Resonator Antenna

    Directory of Open Access Journals (Sweden)

    M. Khalily

    2014-04-01

    Full Text Available A wideband and compact circularly polarized (CP C-shaped dielectric resonator antenna (DRA is presented. The proposed C-shaped DR is excited by a simple stripe line connected to a coplanar waveguide (CPW feeding line. The C-shaped DRA is circularly polarized with 19% axial ratio (AR bandwidth. It is found that the CP bandwidth can be expanded by using a narrow short circuit strip. The final design achieves CP with 50% AR bandwidth. The proposed circularly polarized DRA (CPDRA with good radiation characteristics offers an impedance bandwidth of 58% between 3.45 and 6.26 GHz for VSWR ≤ 2. The proposed DRA is fabricated and tested. Very good agreement between simulated and measured results is obtained.

  13. Triband Omnidirectional Circularly Polarized Dielectric Resonator Antenna with Top-Loaded Alford Loop

    OpenAIRE

    Chunxia Cheng; Fushun Zhang; Yali Yao; Fan Zhang

    2014-01-01

    A triband omnidirectional circularly polarized dielectric resonator antenna with a top-loaded modified Alford loop for GSM, WLAN, and WiMAX applications is proposed. Fed by an axial probe, the DRA (dielectric resonator antenna) radiates like a vertically polarized electric monopole. The top-loaded modified Alford loop provides an equivalent horizontally polarized magnetic dipole mode at triband. Omnidirectional CP (circular polarized) fields can be obtained when the two orthogonally polarized...

  14. Faraday cage angled-etching of nanostructures in bulk dielectrics

    OpenAIRE

    Latawiec, Pawel; Burek, Michael J.; Sohn, Young-Ik; Lončar, Marko

    2016-01-01

    For many emerging optoelectronic materials, heteroepitaxial growth techniques do not offer the same high material quality afforded by bulk, single-crystal growth. However, the need for optical, electrical, or mechanical isolation at the nanoscale level often necessitates the use of a dissimilar substrate, upon which the active device layer stands. Faraday cage angled-etching (FCAE) obviates the need for these planar, thin-film technologies by enabling in-situ device release and isolation thro...

  15. Bulk and interface dielectric functions: New results within the tight-binding approximation

    International Nuclear Information System (INIS)

    A tight-binding approach is used to analyze the dielectric behaviour of bulk semiconductors and semiconductor interfaces. This time interactions between second nearest neighbours are taken into account and several electrostatic models are proposed for the induced charge density around the atoms. The bulk dielectric function of different semiconductors (Si, Ge, GaAs and AlAs) are obtained and compared with other theoretical and experimental results. Finally, the energy band offset for GaAs-AlAs(1,0,0) interface is obtained and related to bulk properties of both semiconductors. The results presented in this paper show how the use of very simple but more realistic electrostatic models improve the analysis of the screening properties in semiconductors, giving a new support to the consistent tight-binding method for studying characteristics related to those properties. (Author)

  16. Fatigue effect on polarization switching dynamics in polycrystalline bulk ferroelectrics

    Science.gov (United States)

    Zhukov, S.; Glaum, J.; Kungl, H.; Sapper, E.; Dittmer, R.; Genenko, Y. A.; von Seggern, H.

    2016-08-01

    Statistical distribution of switching times is a key information necessary to describe the dynamic response of a polycrystalline bulk ferroelectric to an applied electric field. The Inhomogeneous Field Mechanism (IFM) model offers a useful tool which allows extraction of this information from polarization switching measurements over a large time window. In this paper, the model was further developed to account for the presence of non-switchable regions in fatigued materials. Application of the IFM-analysis to bipolar electric cycling induced fatigue process of various lead-based and lead-free ferroelectric ceramics reveals different scenarios of property degradation. Insight is gained into different underlying fatigue mechanisms inherent to the investigated systems.

  17. High-dielectric-constant ferroelectric thin film and bulk ceramic capacitors for power electronics.

    Energy Technology Data Exchange (ETDEWEB)

    Auciello, O. H.; Baldo, P.; Baumann, P.; Erck, R. A.; Giumarra, J.; Im, J.; Kaufman, D. Y.; Lanagan, M. T.; Pan, M. J.; Streiffer, S. K.; Zebrowski, J.

    1999-08-10

    Significant effort is presently focused on reducing the size and weight of power electronic modules. To achieve these goals in high-power capacitors, alternative materials and fabrication processes are needed. Thin film (<0.5 {micro}m) and bulk capacitors that use perovskite-based ferroelectric dielectrics are promising alternative technologies. Ferroelectrics possess high dielectric constants, thus offering substantial increases in volumetric capacitance. In thin film form, these materials display low loss and high breakdown strength. The unique properties of some of these materials, such as a nonlinear dielectric response or a high energy-storage capacity accompanying a phase change, can be exploited for power electronic capacitors. Prototype capacitors of two such materials, (Ba,Sr)TiO{sub 3} and PbZrO{sub 3}, have been fabricated in both thin film and bulk ceramic form. The influence of fabrication conditions on dielectric properties has been studied. Initial studies have demonstrated the viability of perovskite ferroelectrics for next-generation capacitor components.

  18. Modifying Poisson equation for near-solute dielectric polarization and solvation free energy

    Science.gov (United States)

    Yang, Pei-Kun

    2016-06-01

    The dielectric polarization P is important for calculating the stability of protein conformation and the binding affinity of protein-protein/ligand interactions and for exploring the nonthermal effect of an external electric field on biomolecules. P was decomposed into the product of the electric dipole moment per molecule p; bulk solvent density Nbulk; and relative solvent molecular density g. For a molecular solute, 4πr2p(r) oscillates with the distance r to the solute, and g(r) has a large peak in the near-solute region, as observed in molecular dynamics (MD) simulations. Herein, the Poisson equation was modified for computing p based on the modified Gauss's law of Maxwell's equations, and the potential of the mean force was used for computing g. For one or two charged atoms in a water cluster, the solvation free energies of the solutes obtained by these equations were similar to those obtained from MD simulations.

  19. Manipulation of dielectric Rayleigh particles using highly focused elliptically polarized vector fields.

    Science.gov (United States)

    Gu, Bing; Xu, Danfeng; Rui, Guanghao; Lian, Meng; Cui, Yiping; Zhan, Qiwen

    2015-09-20

    Generation of vectorial optical fields with arbitrary polarization distribution is of great interest in areas where exotic optical fields are desired. In this work, we experimentally demonstrate the versatile generation of linearly polarized vector fields, elliptically polarized vector fields, and circularly polarized vortex beams through introducing attenuators in a common-path interferometer. By means of Richards-Wolf vectorial diffraction method, the characteristics of the highly focused elliptically polarized vector fields are studied. The optical force and torque on a dielectric Rayleigh particle produced by these tightly focused vector fields are calculated and exploited for the stable trapping of dielectric Rayleigh particles. It is shown that the additional degree of freedom provided by the elliptically polarized vector field allows one to control the spatial structure of polarization, to engineer the focusing field, and to tailor the optical force and torque on a dielectric Rayleigh particle. PMID:26406514

  20. Polarizing agents and mechanisms for high-field dynamic nuclear polarization of frozen dielectric solids.

    Science.gov (United States)

    Hu, Kan-Nian

    2011-09-01

    This article provides an overview of polarizing mechanisms involved in high-frequency dynamic nuclear polarization (DNP) of frozen biological samples at temperatures maintained using liquid nitrogen, compatible with contemporary magic-angle spinning (MAS) nuclear magnetic resonance (NMR). Typical DNP experiments require unpaired electrons that are usually exogenous in samples via paramagnetic doping with polarizing agents. Thus, the resulting nuclear polarization mechanism depends on the electron and nuclear spin interactions induced by the paramagnetic species. The Overhauser Effect (OE) DNP, which relies on time-dependent spin-spin interactions, is excluded from our discussion due the lack of conducting electrons in frozen aqueous solutions containing biological entities. DNP of particular interest to us relies primarily on time-independent, spin-spin interactions for significant electron-nucleus polarization transfer through mechanisms such as the Solid Effect (SE), the Cross Effect (CE) or Thermal Mixing (TM), involving one, two or multiple electron spins, respectively. Derived from monomeric radicals initially used in high-field DNP experiments, bi- or multiple-radical polarizing agents facilitate CE/TM to generate significant NMR signal enhancements in dielectric solids at low temperatures (submicron domains or embedded in larger biomolecular complexes. The scope of this review is focused on recently developed DNP polarizing agents for high-field applications and leads up to future developments per the CE DNP mechanism. Because DNP experiments are feasible with a solid-state microwave source when performed at alignment. In addition, the combination of an excited triplet and a stable radical might provide alternative DNP mechanisms without the microwave requirement. PMID:21855299

  1. Dielectric and polarization behaviour of cellulose electro-active paper (EAPap)

    International Nuclear Information System (INIS)

    Dielectric and polarization behaviour of electro-active paper (EAPap) were studied to understand the detailed material behaviour of EAPap as a novel smart material. It was revealed that the dielectric constant of EAPap was temperature and frequency dependent. The largest change in the dielectric constant was observed near 0 0C while the highest dielectric constant was obtained at around 100 0C, which might be related to the dipolar behaviour of the hydroxyl structure of cellulose and adsorbed or existing internal water molecules in cellulose EAPap. By thermal stimulated current measurement for polarization behaviour of cellulose EAPap, it was shown that the maximum current was observed in the temperature range 105-110 0C. Compared with the polarization behaviour in the low temperature range, abnormal polarization was observed under an applied field mainly due to the trapped space charge in EAPap, which indicates that cellulose EAPap has a similar material behaviour to that of electret polymers. (fast track communication)

  2. Surface and bulk scattering by magnetic and dielectric inhomogeneities: a first-order method

    International Nuclear Information System (INIS)

    The scattering of a magneto-dielectric multilayer has been studied by a first-order method. The model reported in this manuscript relies on the equivalence between heterogeneities of the medium and fictitious electric and magnetic sources. Types of inhomogeneities considered are roughness and bulk inhomogeneities and concern both permittivity and permeability. The numerical results are compared to those given in previous papers for optical scattering. It is shown in the microwave spectra that angle-resolved scattering allows identification of the scattering origins (permittivity or permeability spectra). The cases of isotropic films and meta-materials are presented and discussed. (authors)

  3. Polarization-independent and high-efficiency dielectric metasurfaces for visible light.

    Science.gov (United States)

    Li, Qi-Tong; Dong, Fengliang; Wang, Bong; Gan, Fengyuan; Chen, Jianjun; Song, Zhiwei; Xu, Lixua; Chu, Weiguo; Xiao, Yun-Feng; Gong, Qihuang; Li, Yan

    2016-07-25

    Dielectric metasurfaces are capable of completely manipulating the phase, amplitude, and polarization of light with high spatial resolutions. The emerging design based on high-index and low-loss dielectrics has led to the realization of novel metasurfaces with high transmissions, but these devices usually operate at the limited bandwidth, and are sensitive to the incident polarization. Here, we report the realization of the polarization-independent and high-efficiency silicon metasurfaces spanning the visible wavelengths about 200 nm. The fabricated computer-generated meta-holograms exhibit a 90% diffraction efficiency, which are verified by gradient metasurfaces with measured efficiencies up to 93% at 670 nm, and exceeding 75% at the wavelengths from 600 to 800 nm for the two orthogonally polarized incidences. These dielectric metasurfaces effectively decouple the phase modulation from the polarization states and frequencies for visible light, which hold great potential for novel flat optical devices operating over a broad spectrum. PMID:27464084

  4. Effect of polarization on dielectric behaviour of PET/0.8PHB polymer liquid crystals

    International Nuclear Information System (INIS)

    Dielectric constant and loss behaviour of pristine and polarized samples of Poly (p-hydroxybenzoic acid-co-ethylene terephthalate) polymer liquid crystals were studied at continuous temperatures ranging from 20 °C to 250 °C, polarized at potentials 500V and 2000V with high precision d.c. power supply. Dielectric constant appears to be almost linearly dependent in the lower temperature region and is independent in the higher temperature region. Dielectric loss becomes approximately ten times lower at higher temperatures

  5. Dielectric and electrical conductivity studies of bulk lead (II) oxide (PbO)

    Energy Technology Data Exchange (ETDEWEB)

    Darwish, A.A.A., E-mail: aaadarwish@gmail.com [Department of Physics, Faculty of Education at Al-Mahweet, Sana’a University, Al-Mahwit (Yemen); Department of Physics, Faculty of Science, University of Tabuk, P.O. Box 741, Tabuk 71491, Tabuk (Saudi Arabia); El-Zaidia, E.F.M.; El-Nahass, M.M. [Department of Physics, Faculty of Education, Ain Shams University, Rorxy, Cairo 11757 (Egypt); Hanafy, T.A. [Department of Physics, Faculty of Science, University of Tabuk, P.O. Box 741, Tabuk 71491, Tabuk (Saudi Arabia); Department of Physics, Faculty of Science, Fayoum University, 63514 El Fayoum (Egypt); Al-Zubaidi, A.A. [Department of Physics, Faculty of Science, University of Tabuk, P.O. Box 741, Tabuk 71491, Tabuk (Saudi Arabia)

    2014-03-15

    Highlights: • The AC measurements of PbO were measured at temperature range 313–523 K. • The dielectric constants increased with temperature. • The mechanism responsible for AC conduction is electronic hopping. -- Abstract: The dielectric properties, the impedance spectroscopy and AC conductivity of bulk PbO have been investigated as a function of frequency and temperature. The measurements were carried out in the frequency range from 40 to 5 × 10{sup 6} Hz and in temperature range from 313 to 523 K. The frequency response of dielectric constant, ε{sub 1}, and dielectric loss index, ε{sub 2}, as a function of temperature were studied. The values of ε{sub 1} and ε{sub 2} were found to decrease with the increase in frequency. However, they increase with the increase in temperature. The presence of a single arc in the complex modulus spectrum at different temperatures confirms the single-phase character of the PbO. The AC conductivity exhibited a universal dynamic response: σ{sub AC} = Aω{sup s}. The AC conductivity was also found to increase with increasing temperature and frequency. The correlation barrier hopping (CBH) model was found to apply to the AC conductivity data. The calculated values of s were decreased with temperature. This behavior reveals that the conduction mechanism for PbO samples is CBH. The activation energy for AC conductivity decreases with increasing frequency. This confirms that the hopping conduction to the dominant mechanism for PbO samples.

  6. The enhanced spontaneous dielectric polarization in Ga doped CuFeO2

    International Nuclear Information System (INIS)

    The magnetic and dielectric polarization properties of the single crystal samples of CuFe1−xGaxO2 (x = 0 and 0.02) are investigated. Experimental results show that the magnetization and dielectric polarizations are anisotropy and coupled together. Compared with pure CuFeO2, in the case with the magnetic field parallel to the c axis, a field-induced phase transition with a hysteresis is clearly observed between the five-sublattice (5SL) and three-sublattice (3SL) phases. Specially, an obvious spontaneous dielectric polarization is observed in CuFe0.98Ga0.02O2 in a lower magnetic field region, indicating that the Ga doping has an effect on the enhancement of spontaneous dielectric polarization. Based on the dilution effect, change of exchange interaction, and partial release of the spin frustration due to the structural modulation of the Ga ion dopant, the origin of the magnetization, and spontaneous polarization characteristics are discussed and the complete dielectric polarization diagrams are assumed.

  7. Polarization properties and dispersion relations for spiral resonances of a dielectric rod

    CERN Document Server

    Schwefel, H G L; Stone, A D; Schwefel, Harald G. L.; Tureci, Hakan E.

    2005-01-01

    Dielectric microcavities based on cylindrical and deformed cylindrical shapes have been employed as resonators for microlasers. Such systems support spiral resonances with finite momentum along the cylinder axis. For such modes the boundary conditions do not separate and simple TM and TE polarization states do not exist. We formulate a theory for the dispersion relations and polarization properties of such resonances for an infinite dielectric rod of arbitrary cross-section and then solve for these quantities for the case of a circular cross-section (cylinder). Useful analytic formulas are obtained using the eikonal (Einstein-Brillouin-Keller) method which are shown to be excellent approximations to the exact results from the wave equation. The major finding is that the polarization of the radiation emitted into the far-field is linear up to a polarization critical angle (PCA) at which it changes to elliptical. The PCA always lies between the Brewster and total-internal-reflection angles for the dielectric, a...

  8. A new equation for dielectric permittivity of saturated soils based on polarization mechanics

    Institute of Scientific and Technical Information of China (English)

    Ren-peng CHEN; Yun-min CHEN; Wei XU; Zhi-gang LIANG; Wei FENG

    2008-01-01

    Based on polarization mechanisms, such as electronic, ionic and orientatioual polarizations, a new equation for dielectric permittivity of soil is proposed to interpret the dielectric behavior of a mixture like soil, in terms of polarization process of its components and the interactions between its components. The dielectric permittivity is expressed in terms of a frequency-dependent part and a frequency-independent part. These two parts correspond to polarizations occurred at different frequency range. It is a new volumetric mixing model with theoretical background. Based on time domain reflectometry (TDR) measurements of saturated soil samples and test data from literature, comparisons of this model with some well established mixing models show that the curves for saturated sand soils and slurries resulted from the new equation, which agree well with TDR measurements, are close to those calculated from Birchak's model.

  9. Polarization-Independent and High-Efficiency Dielectric Metasurfaces Spanning 600-800 nm Wavelengths

    CERN Document Server

    Li, Qi-Tong; Wang, Bo; Gan, Fengyuan; Chen, Jianjun; Chu, Weiguo; Xiao, Yun-Feng; Gong, Qihuang; Li, Yan

    2015-01-01

    Artificial metasurfaces are capable of completely manipulating the phase, amplitude, and polarization of light with high spatial resolutions. The emerging design based on high-index and low-loss dielectrics has led to the realization of novel metasurfaces with high transmissions, but these devices usually operate at the limited bandwidth, and are sensitive to the incident polarization. Here, for the first time we report experimentally the polarization-independent and high-efficiency dielectric metasurfaces spanning the visible wavelengths about 200 nm, which are of importance for novel flat optical devices operating over a broad spectrum. The diffraction efficiencies of the gradient metasurfaces consisting of the multi-fold symmetric nano-crystalline silicon nanopillars are up to 93% at 670 nm, and exceed 75% at the wavelengths from 600 to 800 nm for the two orthogonally polarized incidences. These dielectric metasurfaces hold great potential to replace prisms, lenses and other conventional optical elements.

  10. Polarization-dependent diffraction in all-dielectric, twisted-band structures

    Energy Technology Data Exchange (ETDEWEB)

    Kardaś, Tomasz M.; Jagodnicka, Anna; Wasylczyk, Piotr, E-mail: pwasylcz@fuw.edu.pl [Photonic Nanostructure Facility, Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warszawa (Poland)

    2015-11-23

    We propose a concept for light polarization management: polarization-dependent diffraction in all-dielectric microstructures. Numerical simulations of light propagation show that with an appropriately configured array of twisted bands, such structures may exhibit zero birefringence and at the same time diffract two circular polarizations with different efficiencies. Non-birefringent structures as thin as 3 μm have a significant difference in diffraction efficiency for left- and right-hand circular polarizations. We identify the structural parameters of such twisted-band matrices for optimum performance as circular polarizers.

  11. Polarization-dependent diffraction in all-dielectric, twisted-band structures

    Science.gov (United States)

    Kardaś, Tomasz M.; Jagodnicka, Anna; Wasylczyk, Piotr

    2015-11-01

    We propose a concept for light polarization management: polarization-dependent diffraction in all-dielectric microstructures. Numerical simulations of light propagation show that with an appropriately configured array of twisted bands, such structures may exhibit zero birefringence and at the same time diffract two circular polarizations with different efficiencies. Non-birefringent structures as thin as 3 μm have a significant difference in diffraction efficiency for left- and right-hand circular polarizations. We identify the structural parameters of such twisted-band matrices for optimum performance as circular polarizers.

  12. To Polarize or Not to Polarize? Charge-on-Spring versus KBFF Models for Water and Methanol Bulk and Vapor-Liquid Interfacial Mixtures.

    Science.gov (United States)

    Ploetz, Elizabeth A; Rustenburg, Ariën S; Geerke, Daan P; Smith, Paul E

    2016-05-10

    Simulations of water and methanol mixtures using polarizable force fields (FFs) for methanol (COS/M and CPC) and water (COS/G2) were performed and compared to experiment and also to a nonpolarizable methanol (KBFF) model with SPC/E water in an effort to quantify the importance of explicit electronic polarization effects in bulk liquid mixtures and vapor-liquid interfaces. The bulk liquid mixture properties studied included the center of mass radial distribution functions, Kirkwood-Buff integrals (KBIs), volumetric properties, isothermal compressibility, enthalpy of mixing, dielectric constant, and diffusion coefficients. The vapor-liquid interface properties investigated included the relative surface probability distributions, surface tension, excess surface adsorption, preferred surface molecule orientations, and the surface dipole. None of the three FFs tested here was clearly superior for all of the properties examined. All the force fields typically reproduced the correct trends with composition for both the bulk and interfacial system properties; the differences between the force fields were primarily quantitative. The overall results suggest that the polarizable FFs are not, at the present stage of development, inherently better able to reproduce the studied bulk and interfacial properties-despite the added degree of explicit transferability that is, by definition, built into the polarizable models. Indeed, the specific parametrization of the FF appears to be just as important as the class of FF. PMID:27045390

  13. Dynamic polarization effects on the angular distributions of protons channeled through carbon nanotubes in dielectric media

    OpenAIRE

    Borka, D.; Mowbray, D. J.; Mišković, Z. L.; Petrović, S.; Nešković, N.

    2008-01-01

    The best level of ordering and straightening of carbon nanotube arrays is often achieved when they are grown in a dielectric matrix, so such structures present the most suitable candidates for future channeling experiments with carbon nanotubes. Consequently, we investigate here how the dynamic polarization of carbon valence electrons in the presence of various surrounding dielectric media affects the angular distributions of protons channeled through (11,~9) single-wall carbon nanotubes. Pro...

  14. Magnetoelectric coupling driven dielectric anomaly in non-polar system SeCuO3

    International Nuclear Information System (INIS)

    The non-polar material SeCuO3, which contains Cu2+ with S=1/2 spin and Se4+, has a highly distorted perovskite structure due to the small radii of Se4+ cations. The dielectric constant displays a critical decrease at 25 K, at which temperature the ferromagnetic ordering of the Cu2+ spin appears, suggesting a strong coupling between the magnetic and dielectric properties. Studies on SeCuO3 show that the magnetic and electrical subsystems reciprocally correlate via the hybridization of sp and pd. We conclude that the spin-pair correlation along the b-axis plays a significant role in the decrease of the dielectric constant around the magnetic transition temperature via the magnetoelectric coupling, and successfully explain the dielectric anomaly. The obtained dielectric constant and the magnetocapacitance for SeCuO3 are quantitative agreement with experimental results.

  15. Dielectric tensor of tetracene single crystals: the effect of anisotropy on polarized absorption and emission spectra.

    Science.gov (United States)

    Tavazzi, S; Raimondo, L; Silvestri, L; Spearman, P; Camposeo, A; Polo, M; Pisignano, D

    2008-04-21

    The full UV-visible dielectric tensor and the corresponding directions of the principal axes of triclinic tetracene crystals are reported as deduced either by polarized absorption and ellipsometry measurements or by calculations based on the molecular and crystallographic data. The results allow the attribution of the polarized bands observed in both absorption and photoluminescence emission spectra. In particular, the spectral line shape and polarization of the emission are found to depend on the sample thickness, and the effect is attributed to the modification of the state of polarization of the emitted light during its propagation inside the crystal. Indeed, the directions of polarization of the lowest optical transitions and the directions of the principal axes of the dielectric tensor are demonstrated not to coincide, in contrast to the assumptions typically made in the literature, thus causing the mixed transverse/longitudinal character of light propagation. PMID:18433260

  16. Excitation of radiationless anapole mode of isotropic dielectric nanoparticles with tightly focused radially polarized beam

    CERN Document Server

    Wei, Lei; Bhattacharya, Nandini; Urbach, H Paul

    2016-01-01

    A high index dielectric nano-sphere can be excited and yet remain radiationless. A method to excite the non-radiating anapole mode of a high index isotropic dielectric nanosphere is presented. With tightly focused radially polarized beam illumination, the main-contributing electric dipole mode and magnetic modes can be zero with only a weak electric quadruple contributing to the total scattering. Further, with a standing wave illumination formed by two counter-propagating focused radially polarized beam under $4\\pi$ configuration, the ideal radiationless ananpole can be excited.

  17. Polarization screening in polymer ferroelectric films: uncommon bulk mechanism

    OpenAIRE

    Mikheev, E.; Stolichnov, I.; Tagantsev, A. K.; Setter, N.

    2012-01-01

    Charge compensation at the interface is a fundamental phenomenon determining the operation conditions of thin-film devices incorporating ferroelectrics. The underlying mechanisms have been thoroughly addressed in perovskite ferroelectrics where the charge compensation originates from injection through the interface-adjacent layer. Here, we demonstrate that polarization screening in the polymer ferroelectric polyvinylidene fluoride-trifluoroethylene (P(VDF-TrFE)) films can be dominated by char...

  18. Metal-Multilayer-Dielectric Structure for Enhancement of s- and p-Polarized Evanescent Waves.

    Science.gov (United States)

    Ilchenko, Svitlana G; Lymarenko, Ruslan A; Taranenko, Victor B

    2016-12-01

    We propose a structure based on combination of multilayer stack of dielectric films and thin metal layer for excitation and enhancement of both s- and p-polarized evanescent waves. It is shown that two different mechanisms of evanescent wave excitation may occur at the same angle of light beam incidence on the structure. Application for evanescent wave polarization holographic recording with the help of this structure is discussed. PMID:26831680

  19. Efficient polarization insensitive complex wavefront control using Huygens' metasurfaces based on dielectric resonant meta-atoms

    OpenAIRE

    Chong, Katie E.; Wang, Lei; Staude, Isabelle; James, Anthony; Dominguez, Jason; Liu, Sheng; Subramania, Ganapathi S; Decker, Manuel; Neshev, Dragomir N.; Brener, Igal; Kivshar, Yuri S.

    2016-01-01

    Subwavelength-thin metasurfaces have shown great promises for the control of optical wavefronts, thus opening new pathways for the development of efficient flat optics. In particular, Huygens' metasurfaces based on all-dielectric resonant meta-atoms have already shown a huge potential for practical applications with their polarization insensitivity and high transmittance efficiency. Here, we experimentally demonstrate a polarization insensitive holographic Huygens' metasurface based on dielec...

  20. Efficient polarization insensitive complex wavefront control using Huygens' metasurfaces based on dielectric resonant meta-atoms

    CERN Document Server

    Chong, Katie E; Staude, Isabelle; James, Anthony; Dominguez, Jason; Liu, Sheng; Subramania, Ganapathi S; Decker, Manuel; Neshev, Dragomir N; Brener, Igal; Kivshar, Yuri S

    2016-01-01

    Subwavelength-thin metasurfaces have shown great promises for the control of optical wavefronts, thus opening new pathways for the development of efficient flat optics. In particular, Huygens' metasurfaces based on all-dielectric resonant meta-atoms have already shown a huge potential for practical applications with their polarization insensitivity and high transmittance efficiency. Here, we experimentally demonstrate a polarization insensitive holographic Huygens' metasurface based on dielectric resonant meta-atoms capable of complex wavefront control at telecom wavelengths. Our metasurface produces a hologram image in the far-field with 82% transmittance efficiency and 40% imaging efficiency. Such efficient complex wavefront control shows that Huygens' metasurfaces based on resonant dielectric meta-atoms are a big step towards practical applications of metasurfaces in wavefront design related technologies, including computer-generated holograms, ultra-thin optics, security and data storage devices.

  1. Analysis of Circularly Polarized Hemispheroidal Dielectric Resonator Antenna Phased Arrays Using the Method of Auxiliary Sources

    DEFF Research Database (Denmark)

    Larsen, Niels Vesterdal; Breinbjerg, Olav

    2007-01-01

    The method of auxiliary sources is employed to model and analyze probe-fed hemispheroidal dielectric resonator antennas and arrays. Circularly polarized antenna elements of different designs are analyzed, and impedance bandwidths of up to 14.7% are achieved. Selected element designs are...

  2. Wideband resonant polarizers made with ultra-sparse dielectric nanowire grids

    CERN Document Server

    Yoon, Jae Woong; Magnusson, Robert

    2015-01-01

    Polarizers are essential in diverse photonics applications including display [1], microscopy [2], polarimetric astrophysical observation [3], laser machining [4], and quantum information processing [5]. Whereas conventional polarizers based on natural crystals and multilayer thin films are commonplace, nanostructured polarizers offer compact integrability [6,7], thermal stability in high-power systems [4,8], and space-variant vector beam generation [9,10]. Here, we introduce a new class of reflectors and polarizers fashioned with dielectric nanowire grids that are mostly empty space. It is fundamentally extremely significant that the wideband spectral expressions presented can be generated in these minimal systems. We provide computed results predicting high reflection and attendant polarization extinction in multiple spectral regions. Experimental results with Si nanowire arrays show ~200-nm-wide band of total reflection for one polarization state and free transmission for the orthogonal state. These results...

  3. Temperature-dependent dielectric and energy-storage properties of Pb(Zr,Sn,Ti)O3 antiferroelectric bulk ceramics

    OpenAIRE

    Xuefeng Chen; Zhen Liu(Pittsburgh Particle physics, Astrophysics, and Cosmology Center, Department of Physics and Astronomy, University of Pittsburgh, 3941 O’Hara St., Pittsburgh, PA 15260, U.S.A.); Chenhong Xu; Fei Cao; Genshui Wang; Xianlin Dong

    2016-01-01

    The dielectric and energy-storage properties of Pb0.99Nb0.02[(Zr0.60Sn0.40)0.95Ti0.05]0.98O3 (PNZST) bulk ceramics near the antiferroelectric (AFE)-ferroelectric (FE) phase boundary are investigated as a function of temperature. Three characteristic temperatures T0, TC, T2 are obtained from the dielectric temperature spectrum. At different temperature regions (below T0, between T0 and TC, and above TC), three types of hysteresis loops are observed as square double loop, slim loop and linear l...

  4. Polarization-tuned Dynamic Color Filters Incorporating a Dielectric-loaded Aluminum Nanowire Array

    Science.gov (United States)

    Raj Shrestha, Vivek; Lee, Sang-Shin; Kim, Eun-Soo; Choi, Duk-Yong

    2015-07-01

    Nanostructured spectral filters enabling dynamic color-tuning are saliently attractive for implementing ultra-compact color displays and imaging devices. Realization of polarization-induced dynamic color-tuning via one-dimensional periodic nanostructures is highly challenging due to the absence of plasmonic resonances for transverse-electric polarization. Here we demonstrate highly efficient dynamic subtractive color filters incorporating a dielectric-loaded aluminum nanowire array, providing a continuum of customized color according to the incident polarization. Dynamic color filtering was realized relying on selective suppression in transmission spectra via plasmonic resonance at a metal-dielectric interface and guided-mode resonance for a metal-clad dielectric waveguide, each occurring at their characteristic wavelengths for transverse-magnetic and electric polarizations, respectively. A broad palette of colors, including cyan, magenta, and yellow, has been attained with high transmission beyond 80%, by tailoring the period of the nanowire array and the incident polarization. Thanks to low cost, high durability, and mass producibility of the aluminum adopted for the proposed devices, they are anticipated to be diversely applied to color displays, holographic imaging, information encoding, and anti-counterfeiting.

  5. Terahertz response of dipolar impurities in polar liquids: On anomalous dielectric absorption of protein solutions

    CERN Document Server

    Matyushov, D V

    2009-01-01

    A theory of radiation absorption by dielectric mixtures is presented. The coarse-grained formulation is based on the wavevector-dependent correlation functions of molecular dipoles of the host polar liquid and a density-density structure factor of the positions of the solutes. A nonlinear dependence of the absorption coefficient on the solute concentration is predicted and originates from the mutual polarization of the liquid surrounding the solutes by the collective field of the solute dipoles aligned along the radiation field. The theory is applied to terahertz absorption of hydrated saccharides and proteins. While the theory gives an excellent account of the observations for saccharides without additional assumptions and fitting parameters, experimental absorption coefficient of protein solutions significantly exceeds theoretical calculations within standard dielectric models and shows a peak against the protein concentration. A substantial polarization of protein's hydration shell is required to explain t...

  6. Polarized neutron powder diffraction studies of antiferromagnetic order in bulk and nanoparticle NiO

    DEFF Research Database (Denmark)

    Brok, Erik; Lefmann, Kim; Deen, Pascale P.; Lebech, Bente; Jacobsen, Henrik; Nilsen, Gøran Jan; Keller, Lukas; Frandsen, Cathrine

    2015-01-01

    surface contribution to the magnetic anisotropy. Here we explore the potential use of polarized neutron diffraction to reveal the magnetic structure in NiO bulk and nanoparticle powders by applying the XYZ-polarization analysis method. Our investigations address in particular the spin orientation in bulk...... NiO and platelet-shaped NiO nanoparticles with thickness from greater than 200 nm down to 2.0 nm. The advantage of the applied method is that it is able to clearly separate the structural, the magnetic, and the spin-incoherent scattering signals for all particle sizes. For platelet-shaped particles...

  7. Dielectric metasurfaces for complete control of phase and polarization with subwavelength spatial resolution and high transmission.

    Science.gov (United States)

    Arbabi, Amir; Horie, Yu; Bagheri, Mahmood; Faraon, Andrei

    2015-11-01

    Metasurfaces are planar structures that locally modify the polarization, phase and amplitude of light in reflection or transmission, thus enabling lithographically patterned flat optical components with functionalities controlled by design. Transmissive metasurfaces are especially important, as most optical systems used in practice operate in transmission. Several types of transmissive metasurface have been realized, but with either low transmission efficiencies or limited control over polarization and phase. Here, we show a metasurface platform based on high-contrast dielectric elliptical nanoposts that provides complete control of polarization and phase with subwavelength spatial resolution and an experimentally measured efficiency ranging from 72% to 97%, depending on the exact design. Such complete control enables the realization of most free-space transmissive optical elements such as lenses, phase plates, wave plates, polarizers, beamsplitters, as well as polarization-switchable phase holograms and arbitrary vector beam generators using the same metamaterial platform. PMID:26322944

  8. Significantly elevated dielectric permittivity of Si-based semiconductor/polymer 2-2 composites induced by high polarity polymers

    International Nuclear Information System (INIS)

    To disclose the essential influence of polymer polarity on dielectric properties of polymer composites filled with semiconductive fillers, a series of Si-based semiconductor/polymer 2-2 composites in a series model was fabricated. The dielectric permittivity of composites is highly dependant on the polarity of polymer layers as well as the electron mobility in Si-based semiconductive sheets. The huge dielectric permittivity achieved in Si-based semiconductive sheets after being coated with high polarity polymer layers is inferred to originate from the strong induction of high polarity polymers. The increased mobility of the electrons in Si-based semiconductive sheets coated by high polarity polymer layers should be responsible for the significantly enhanced dielectric properties of composites. This could be facilely achieved by either increasing the polarity of polymer layers or reducing the percolative electric field of Si-based semiconductive sheets. The most promising 2-2 dielectric composite was found to be made of α-SiC with strong electron mobility and poly(vinyl alcohol) (PVA) with high polarity, and its highest permittivity was obtained as 372 at 100 Hz although the permittivity of α-SiC and PVA is 3–5 and 15, respectively. This work may help in the fabrication of high dielectric constant (high-k) composites by tailoring the induction effect of high polarity polymers to semiconductors. (paper)

  9. Characterization of the influence of polarization orientation on bulk damage in KDP crystals at different wavelengths

    Science.gov (United States)

    Zheng, YinBo; Ding, Lei; Zhou, XinDa; Ba, RongSheng; Yuan, Jing; Xu, HongLei; Na, Jin; Li, YaJun; Yang, XiaoYu; Chai, Liqun; Chen, Bo; Zheng, WanGuo

    2016-08-01

    The investigation of polarization orientation on damage performance of type I doubler KDP crystals under different wavelengths pulses irradiation is presented in this work. Pinpoints densities (PPD) and the size distribution of pinpoints are extracted through light scattering pictures captured by microscope. The obtained results indicate that the measured PPD as a function of the fluence is both wavelength and polarization dependent, although neither fluence nor polarization have impact on the size distribution of pinpoints. We also find that the damage performances can separate into three groups depending on the wavelength, which suggests the existence of different categories of precursors and different mechanisms responsible for bulk damage initiation in SHG KDP crystals.

  10. Gigahertz Dielectric Polarization of Substitutional Single Niobium Atoms in Defective Graphitic Layers.

    Science.gov (United States)

    Zhang, Xuefeng; Guo, Junjie; Guan, Pengfei; Qin, Gaowu; Pennycook, Stephen J

    2015-10-01

    We synthesize two Nb/C composites with an order of magnitude difference in the density of single niobium atoms substituted into defective graphitic layers. The concentration and sites of single Nb atoms are identified using aberration-corrected scanning transmission electron microscopy and density functional theory. Comparing the experimental complex permittivity spectra reveals that a representative dielectric resonance at ∼16  GHz originates from the intrinsic polarization of single Nb atom sites, which is confirmed by theoretical simulations. The single-atom dielectric resonance represents the physical limit of the electromagnetic response of condensed matter, and thus might open up a new avenue for designing electromagnetic wave absorption materials. Single-atom resonance also has important implications in understanding the correlation between the macroscopic dielectric behaviors and the atomic-scale structural origin. PMID:26551823

  11. Dielectric relaxation time of bulk water at 136-140 K, background loss and crystallization effects

    Science.gov (United States)

    Johari, G. P.

    2005-04-01

    Dielectric relaxation time, τ, of ultraviscous bulk water has been determined by analyzing its loss tangent, tanδ, data, which had been measured on heating the vapor-deposited amorphous solid water and hyperquenched glassy water in our earlier studies. [Johari, Hallbrucker, and Mayer, J. Chem. Phys. 95, 2955 (1991); 97, 5851 (1992)]. As for glasses and liquids generally, the measured tanδ of water is the sum of a frequency-independent background loss and a frequency-dependent relaxational loss. A two-frequency method is provided for determining the background loss and used for obtaining the relaxational part of tanδ. After considering the structural relaxation and crystal-nuclei growth effects, τ for water has been determined. At 136±1K, it is 2.5±0.6s when a single relaxation time is (untenably) assumed, and 42±14s when a distribution of relaxation times, a characteristic of viscous liquids, is assumed, with Davidson-Cole distribution parameter of 0.75. Structural relaxation time of ˜70s for water at 136K, which was originally estimated from the DSC endotherm [Johari, Hallbrucker, and Mayer, Nature (London) 330, 552 (1987)], has been revised to ˜33s. Temperature dependence of τ could not be determined because ultraviscous water crystallizes too rapidly to cubic ice containing stacking faults and intergranular water. The study demonstrates that water is a liquid over the 136-155K range, thus removing the basis for a recent contention on its state.

  12. Polarizing Agents and Mechanisms for High-Field Dynamic Nuclear Polarization of Frozen Dielectric Solids

    OpenAIRE

    Hu, Kan-Nian

    2011-01-01

    This article provides an overview of polarizing mechanisms involved in high-frequency dynamic nuclear polarization (DNP) of frozen biological samples at temperatures maintained using liquid nitrogen, compatible with contemporary magic-angle spinning (MAS) nuclear magnetic resonance (NMR). Typical DNP experiments require unpaired electrons that are usually exogenous in samples via paramagnetic doping with polarizing agents. Thus, the resulting nuclear polarization mechanism depends on the elec...

  13. Broadbanding of circularly polarized patch antenna by waveguided magneto-dielectric metamaterial

    Directory of Open Access Journals (Sweden)

    Xin Mi Yang

    2015-12-01

    Full Text Available Design of bandwidth-enhanced circularly polarized (CP patch antenna using artificial magneto-dielectric substrate was investigated. The artificial magneto-dielectric material adopted here takes the form of waveguided metamaterial (WG-MTM. In particular, the embedded meander line (EML structure was employed as the building element of the WG-MTM. As verified by the retrieved effective medium parameters, the EML-based waveguided magneto-dielectric metamaterial (WG-MDM exhibits two-dimensionally isotropic magneto-dielectric property with respect to TEM wave excitations applied in two orthogonal directions. A CP patch antenna loaded with the EML-based WG-MDM (WG-MDM antenna has been proposed and its design procedure is described in detail. Simulation results show that the impedance and axial ratio bandwidths of the WG-MDM antenna have increased by 125% and 133%, respectively, compared with those obtained with pure dielectric substrate offering the same patch size. The design of the novel WG-MDM antenna was also validated by measurement results, which show good agreement with their simulated counterparts.

  14. Broadbanding of circularly polarized patch antenna by waveguided magneto-dielectric metamaterial

    Science.gov (United States)

    Yang, Xin Mi; Wen, Juan; Liu, Chang Rong; Liu, Xue Guan; Cui, Tie Jun

    2015-12-01

    Design of bandwidth-enhanced circularly polarized (CP) patch antenna using artificial magneto-dielectric substrate was investigated. The artificial magneto-dielectric material adopted here takes the form of waveguided metamaterial (WG-MTM). In particular, the embedded meander line (EML) structure was employed as the building element of the WG-MTM. As verified by the retrieved effective medium parameters, the EML-based waveguided magneto-dielectric metamaterial (WG-MDM) exhibits two-dimensionally isotropic magneto-dielectric property with respect to TEM wave excitations applied in two orthogonal directions. A CP patch antenna loaded with the EML-based WG-MDM (WG-MDM antenna) has been proposed and its design procedure is described in detail. Simulation results show that the impedance and axial ratio bandwidths of the WG-MDM antenna have increased by 125% and 133%, respectively, compared with those obtained with pure dielectric substrate offering the same patch size. The design of the novel WG-MDM antenna was also validated by measurement results, which show good agreement with their simulated counterparts.

  15. A Single-Point-Fed Wideband Circularly Polarized Rectangular Dielectric Resonator Antenna

    OpenAIRE

    Deqiang Yang; Meng Zou; Jin Pan

    2016-01-01

    A single-point-fed circularly polarized (CP) rectangular dielectric resonator antenna (DRA) with wide CP bandwidth is presented. By using TE111 and TE113 modes of the rectangular DRA, a wideband CP performance is achieved. The coupling slot of the antenna contains a resistor loaded monofilar-spiral-slot and four linear slots. Design concept of the proposed antenna is demonstrated by simulations, and parameter studies are carried out. Prototype of the proposed antenna was fabricated and measur...

  16. Analysis of Circularly Polarized Hemispheroidal Dielectric Resonator Antenna Phased Arrays Using the Method of Auxiliary Sources

    OpenAIRE

    Larsen, Niels Vesterdal; Breinbjerg, Olav

    2007-01-01

    The method of auxiliary sources is employed to model and analyze probe-fed hemispheroidal dielectric resonator antennas and arrays. Circularly polarized antenna elements of different designs are analyzed, and impedance bandwidths of up to 14.7% are achieved. Selected element designs are subsequently employed in a seven-element phased array. The array performance is analyzed with respect to scan loss and main beam directivity as a function of scan angle and frequency, and the influence of elem...

  17. Polarization Dependence of Surface Enhanced Raman Scattering on a Single Dielectric Nanowire

    Directory of Open Access Journals (Sweden)

    Hua Qi

    2012-01-01

    Full Text Available Our measurements of surface enhanced Raman scattering (SERS on Ga2O3 dielectric nanowires (NWs core/silver composites indicate that the SERS enhancement is highly dependent on the polarization direction of the incident laser light. The polarization dependence of the SERS signal with respect to the direction of a single NW was studied by changing the incident light angle. Further investigations demonstrate that the SERS intensity is not only dependent on the direction and wavelength of the incident light, but also on the species of the SERS active molecule. The largest signals were observed on an NW when the incident 514.5 nm light was polarized perpendicular to the length of the NW, while the opposite phenomenon was observed at the wavelength of 785 nm. Our theoretical simulations of the polarization dependence at 514.5 nm and 785 nm are in good agreement with the experimental results.

  18. Triband Omnidirectional Circularly Polarized Dielectric Resonator Antenna with Top-Loaded Alford Loop

    Directory of Open Access Journals (Sweden)

    Chunxia Cheng

    2014-01-01

    Full Text Available A triband omnidirectional circularly polarized dielectric resonator antenna with a top-loaded modified Alford loop for GSM, WLAN, and WiMAX applications is proposed. Fed by an axial probe, the DRA (dielectric resonator antenna radiates like a vertically polarized electric monopole. The top-loaded modified Alford loop provides an equivalent horizontally polarized magnetic dipole mode at triband. Omnidirectional CP (circular polarized fields can be obtained when the two orthogonally polarized fields are equal in amplitude with phase quadrature. The antenna has been successfully simulated, fabricated, and measured. The experimental and numerical results exhibit that the antenna can obtain usable CP bandwidths of 1.925–1.955 GHz, 2.36–2.48 GHz, and 3.502–3.53 GHz with return loss larger than 10 dB and axial ratio less than 3 dB. In addition, over the three bands, the antenna obtains very good omnidirectional CP radiation patterns in the azimuth plane. Moreover, an average CP gain in the azimuth plane of 1.2, 1.6, and −1.5 dBic for the lower, middle, and upper bands has been obtained.

  19. Restoration of s-polarized evanescent waves and subwavelength imaging by a single dielectric slab

    Science.gov (United States)

    El Gawhary, Omar; Schilder, Nick J.; da Costa Assafrao, Alberto; Pereira, Silvania F.; Urbach, H. Paul

    2012-05-01

    It was predicted a few years ago that a medium with negative index of refraction would allow for perfect imaging. Although no material has been found so far that behaves as a perfect lens, some experiments confirmed the theoretical predictions in the near-field, or quasi-static, regime where the behaviour of a negative index medium can be mimicked by a thin layer of noble metal, such as silver. These results are normally attributed to the excitation of surface plasmons in the metal, which only leads to the restoration of p-polarized evanescent waves. In this work, we show that the restoration of s-polarized evanescent waves and, correspondingly, sub-wavelength imaging by a single dielectric slab are possible. Specifically, we show that at λ = 632 nm a thin layer of GaAs behaves as a superlens for s-polarized waves. Replacing the single-metal slab by a dielectric is not only convenient from a technical point of view, it being much easier to deposit and control the thickness and flatness of dielectric films than metal ones, but also invites us to re-think the connection between surface plasmon excitation and the theory of negative refraction.

  20. Restoration of s-polarized evanescent waves and subwavelength imaging by a single dielectric slab

    International Nuclear Information System (INIS)

    It was predicted a few years ago that a medium with negative index of refraction would allow for perfect imaging. Although no material has been found so far that behaves as a perfect lens, some experiments confirmed the theoretical predictions in the near-field, or quasi-static, regime where the behaviour of a negative index medium can be mimicked by a thin layer of noble metal, such as silver. These results are normally attributed to the excitation of surface plasmons in the metal, which only leads to the restoration of p-polarized evanescent waves. In this work, we show that the restoration of s-polarized evanescent waves and, correspondingly, sub-wavelength imaging by a single dielectric slab are possible. Specifically, we show that at λ = 632 nm a thin layer of GaAs behaves as a superlens for s-polarized waves. Replacing the single-metal slab by a dielectric is not only convenient from a technical point of view, it being much easier to deposit and control the thickness and flatness of dielectric films than metal ones, but also invites us to re-think the connection between surface plasmon excitation and the theory of negative refraction. (paper)

  1. Dielectric properties measurement method in the microwave frequencies range for non-polar/polar liquid mixtures characterization

    Science.gov (United States)

    Surducan, E.; Neamtu, C.; Ienciu, M.; Surducan, V.; Limare, A.; Fourel, L.

    2015-12-01

    We present a method based on dielectric properties measurements over a large spectrum of frequencies, in the microwave (MW) domain, in order to characterize a liquid mixture. The liquid mixtures consist of non-polar fluids (silicone oil, diesel fuel) and polar additives, in order to increase the specific MW absorption of the mixture for further MW power processing. We have measured the MW specific absorptions for mixtures of silicone oil with 20% and 30% (w/w) isopropanol. In both cases, the mixtures are sufficiently stable over time to allow further studies of thermal convection dynamics initiated by MW heating. For a mixture of diesel fuel with 10% (w/w) alkyl polyglycoside, the main observation was that its MW specific absorption varies over time after the mechanical mixing process.

  2. Enhanced dielectric polarization and electro-responsive characteristic of graphene oxide-wrapped titania microspheres

    International Nuclear Information System (INIS)

    Electric field-induced particle polarization is essential to the electro-responsive electrorheological (ER) effect of particle suspensions. In this work, we use graphene oxide (GO) as a soft and polar coating shell to prepare GO-wrapped titania dielectric microspheres for use as the dispersal phase of an ER suspension. Under a DC electric field, the ER characteristic of GO-wrapped titania microspheres dispersed in silicone oil is investigated by rheological tests, and then compared with that of a suspension of bare titania microspheres. The results show that the suspension of GO-wrapped titania microspheres possesses an enhanced ER characteristic. Its field-induced shear yield stress and storage modulus are much higher than those of the suspension of bare titania microspheres. The soft and polar GO shell is regarded as the origin of the ER enhancement. Dielectric analysis indicates that wrapping GO can enhance the interfacial polarization and thus improve the ER characteristics of titania microspheres. Wrapping GO onto the surface of titania microspheres can also reduce the particle sedimentation velocity of the suspension. (paper)

  3. Design of polarization-insensitive superconducting single photon detectors with high-index dielectrics

    CERN Document Server

    Redaelli, Luca; Monroy, E; Gérard, J M

    2016-01-01

    In this paper, the design of superconducting-nanowire single-photon detectors which are insensitive to the polarization of the incident light is investigated. By using high-refractive-index dielectrics, the index mismatch between the nanowire and the surrounding media is reduced. This enhances the absorption of light with electric field vector perpendicular to the nanowire segments, which is generally hindered in this kind of detectors. Building on this principle and focusing on NbTiN nanowire devices, we present several easy-to-realize cavity architectures which allow high absorption efficiency (in excess of 90%) and polarization insensitivity simultaneously. Designs based on ultranarrow nanowires, for which the polarization sensitivity is much more marked, are also presented. Finally, we briefly discuss the specific advantages of this approach in the case of WSi or MoSi nanowires.

  4. Polarization and angle insensitive dual-band bandpass frequency selective surface using all-dielectric metamaterials

    Science.gov (United States)

    Yu, Fei; Wang, Jun; Wang, Jiafu; Ma, Hua; Du, Hongliang; Xu, Zhuo; Qu, Shaobo

    2016-04-01

    In this paper, we demonstrate a dual-band bandpass all-dielectric frequency selective surface (FSS), the building elements of which are high-permittivity ceramic particles rather than metallic patterns. With proper structural design and parameter adjustment, the resonant frequency can be tuned at will. Dual-band bandpass response can be realized due to the coupling between electric and magnetic resonances. As an example, a dual-band bandpass FSS is designed in Ku band, which is composed of two-dimensional periodic arrays of complementary quatrefoil structures (CQS) cut from dielectric plates. Moreover, cylindrical dielectric resonators are introduced and placed in the center of each CQS to broaden the bandwidth and to sharpen the cut-off frequency. Theoretical analysis shows that the bandpass response arises from impedance matching caused by electric and magnetic resonances. In addition, effective electromagnetic parameters and dynamic field distributions are presented to explain the mechanism of impedance matching. The proposed FSS has the merits of polarization independence, stable transmission, and sharp roll-off frequency. The method can also be used to design all-dielectric FSSs with continuum structures at other frequencies.

  5. Dielectric Constant of Titan's South Polar Region from Cassini Radio Science Bistatic Scattering Observations

    Science.gov (United States)

    Marouf, E.; Rappaport, N.; French, R.; Simpson, R.; Kliore, A.; McGhee, C.; Schinder, P.; Anabtawi, A.

    2008-12-01

    Four out of six Radio Science bistatic scattering (bistatic-radar) observations of Titan's surface completed during the Cassini nominal mission yielded detectable quasi-specular 3.6 cm-λ (X-band) surface echoes, making Titan the most distant solar system object for which bistatic echoes have been successfully detected. Right circularly polarized sinusoidal signal was transmitted by Cassini and both the right and left circularly polarized (RCP and LCP) surface reflected components were observed at the 70-m stations of NASA Deep Space Network. Cassini was maneuvered continuously to track the region of Titan's surface where mirror-like (quasi-specular) reflected signals may be observed. The experiments were designed for incidence angles θ close to the Brewster, or polarization, angle of likely surface compositions. Careful measurement of the system noise temperature allowed determination of the absolute power in each polarized echo component and hence their ratio. The polarization ratio, the known observation geometry, and Fresnel reflection theory were then used to determine the dielectric constant ɛ. Three near-equatorial (~ 5 to 15° S) observations on flyby T14 inbound and outbound and on flyby T34 inbound yielded weak but clearly detectable echoes. The echoes were intermittent along the ground track, indicating mostly rough terrain occasionally interrupted by patches of relatively flat areas. For the two observations on T14, polarization ratio measurements for two localized but widely separated surface regions (~ 15° S, ~ 14 and 140° W) conducted at angles θ ~ 56° and 64°, close to the Brewster angle for ices, imply ɛ ~ 1.6 for both regions, suggesting liquid hydrocarbons although alternative interpretations are possible (Marouf et al., 2006 Fall AGU, P11A- 07). In sharp contrast, a single high latitude (~81-86° S, ~ 45-155° W) observation on T27 inbound yielded much stronger surface echoes that lasted for almost the full duration of the experiment

  6. Tight focusing of a double-ring-shaped, azimuthally polarized beam through a dielectric interface.

    Science.gov (United States)

    Shu, Jianhua; Chen, Ziyang; Pu, Jixiong; Liu, Yongxin

    2014-06-01

    We investigate the tight focusing properties of a double-ring-shaped, azimuthally polarized vector beam (DRS-APVB) by use of vectorial Debye theory. It is shown that a dark channel with an ultralong depth of focus (~106λ) and subwavelength focal holes (~0.5λ) can be generated by focusing a DRS-APVB through a dielectric interface with an annular high-numerical aperture (NA) objective lens. The influence of the NA of the objective, the relative refractive indices of two dielectric media, and the probe depth of the system on the focusing properties of the dark channel has been studied in detail. Such a non-diffracting dark channel could find potential applications in atom optical experiments, such as with atomic lenses, atom traps, and atom switches. PMID:24977354

  7. Design of Yagi-Uda antennas based on high-permittivity dielectric bulk materials

    OpenAIRE

    Bueno Díez, Miguel Ángel

    2012-01-01

    [ANGLÈS] Dielectrics are insulators and they might therefore seem to be unlikely materials out of which to try and make antennas, but if they are excited in the right way they can be made to radiate very efficiently. Taking advantage of the properties of dielectric materials, a Yagi-Uda antenna based on a high-permittivity ceramic material operating at 3.68 GHz is described. The three-element array features a simulated directivity of approximately 8 dBi and a front-to-back ratio of 10.5 dB. M...

  8. Dielectric relaxation phenomena of rigid polar liquid molecules under giga hertz electric field

    Indian Academy of Sciences (India)

    K Dutta; S K Sit; S Acharyya

    2001-10-01

    The dielectric relaxation phenomena of rigid polar liquid molecules chloral and ethyltrichloroacetate () in benzene, -hexane and -heptane () under 4.2, 9.8 and 24.6 GHz electric fields at 30°C are studied to show the possible existence of double relaxation times 2 and 1 for rotations of the whole and the flexible parts of molecules. The probability of showing double relaxation is more in aliphatic solvents indicating their nonrigidity. The symmetric and asymmetric distribution parameters and are obtained from $'_{ij}/_{0ij}$ and $''_{ij}/_{0ij}$ at $w_{j}→ 0$ where $'_{ij}$ and $''_{ij}$ are real and imaginary parts of the complex orientational susceptibility $^{*}_{ij}$ and $_{0ij}$ is the low frequency susceptibility which is real. $_{ij}$’s are involved with the measured dielectric relative permittivities $'_{ij}$, $''_{ij}$, $_{0ij}$ and $_{∞ ij}$ of solutions. The theoretical weighted contributions $c_{1}$ and $c_{2}$ towards dielectric dispersions by Fröhlich’s method are compared with the experimental ones obtained from the graphical variation of $'_{ij}/_{0ij}$ and $''_{ij}/_{0ij}$ with weight fractions $w_{j}$’s at $w_{j}→ 0$. The measured dipole moments $_{2}$ and $_{1}$ of the whole and the flexible part of a polar molecule in terms of the linear coefficients 's of $'_{ij}$’s with $w_{j}$’s and the estimated $_{2}$ and $_{1}$ reveal their associations with aliphatic solvents. The theoretical dipole moments $_{\\text{theo}}$’s from the available bond angles and bond moments of the substituent polar groups of the molecules with the estimated ’s suggest the mesomeric, inductive and electromeric effects in them under GHz electric field.

  9. Core–shell nanoparticles and enhanced polarization in polymer based nanocomposite dielectrics

    International Nuclear Information System (INIS)

    We present a detailed study of the evolution and nature of metallic core–oxide shell particles and the role of nanostructure in the physics of enhanced polarization in polymer-nanocomposite (PNC) based dielectrics. Nylon-6 based PNCs consisting of aluminium (core)–aluminium oxide (shell) nanoparticles were fabricated by a vacuum deposition technique. Their resulting high polarizability was closely related to the formation and chemistry of the core–shell structure that was revealed by transmission electron microscopy to comprise a highly-defective, strained and non-stoichiometric semi-crystalline/amorphous Al-oxide shell. (paper)

  10. A Simple Method for Estimation of Dielectric Constants and Polarizabilities of Nonpolar and Slightly Polar Hydrocarbons

    Science.gov (United States)

    Panuganti, Sai R.; Wang, Fei; Chapman, Walter G.; Vargas, Francisco M.

    2016-07-01

    Many of the liquids that are used as electrical insulators are nonpolar or slightly polar petroleum-derived hydrocarbons, such as the ones used for cable and/or transformer oils. In this work, semi-empirical expressions with no adjustable parameters for the dielectric constant and the polarizability of nonpolar and slightly polar hydrocarbons and their mixtures are proposed and validated. The expressions that were derived using the Vargas-Chapman One-Third rule require the mass density and the molecular weight of the substance of interest. The equations were successfully tested for various hydrocarbons and polymers with dipole moments densities from 500 to 1200 kg\\cdot hbox {m}^{-3}. The predictions are in good agreement with the experimental data in a wide range of temperatures and pressures. The proposed expressions eliminate the need of extensive experimental data and require less input parameters compared to existing correlations.

  11. Influence of polarization to the dielectric properties of polymers and piezocomposites with a nonequilibrium structure

    International Nuclear Information System (INIS)

    Full text: In this work the frequency temperature dependence of tgδ and ε of the polarized PE, PP films and piezocomposites on the basis of PE/ZTP-19, PP/ZTP-19 (40:60 vol.%), obtained at different crystallization regimes, have been investigated. It has been shown that, at crystallization velocity of 1800-2000 degree/min, the obtained samples has a nonequilibrium structure and frequency of ω =(4†4.3). 104 Hs on tgδ (ω) dependence of the samples piezocomposites observed a losses of the dielectric maximum, which has a relaxation nature. It is established that, in PE, PP polarized films takes place the capture of stabilized charge carriers on traps, under influence of the intrinsic field, which in results observes the decrease of the tgδ and ε

  12. A novel microwave cancellation circuit for measuring nonlinear dielectric changes of polar solution under microwave fields

    Science.gov (United States)

    Sun, Hao-Ran; Huang, Ka-Ma

    2015-12-01

    In this paper, an experimental set-up based on a novel microstrip cancellation circuit is presented for investigating the effects of external microwave fields on the dielectric properties of polar solution. The circuit consists of a 3 dB Wilkinson power combiner, a conventional 20 dB backward coupler, and a specially designed 20 dB single-sectioned forward coupler. Besides, in order to realize a uniform electric field in the tested solution, a nicked microstrip ring is designed in the circuit. An improvement of measurement sensitivity in the proposed circuit was obtained when compared to the conventional transmission lines method. We exploit interference cancellation processes to suppress the probing signal at the output port under the principle that two identical amplitude signals with 180° phase difference will completely cancel each other. The measurements are carried out at the frequency of 2.45 GHz, and the temperature effects caused by microwave heating are excluded by the flowing fluid. Experimental results show that the dielectric properties of DMSO-methanol/ethanol mixtures change at the electric field intensity of 105 V m  -  1 and present a distinctly nonlinear dielectric change with the electric fields. The study of the microwave-material interaction has expanded our insights into the high-power microwave’s industry application.

  13. Microwave characterization of bulk ferroelectrics and relaxors using composite dielectric resonator

    Czech Academy of Sciences Publication Activity Database

    Veljko, Sergiy; Bovtun, Viktor; Krupka, J.; Nuzhnyy, Dmitry; Borisov, V.; Kamba, Stanislav; Petzelt, Jan

    Danvers, MA: IEEE, 2007 - (Kostenko, A.; Nosich, A.; Yakovenko, V.), s. 794-796 ISBN 1-4244-1237-4. [MSMW '07. International Kharkov Symposium /6./. Kharkov (UA), 25.06.2007-30.06.2007] R&D Projects: GA ČR(CZ) GA202/06/0403 Institutional research plan: CEZ:AV0Z10100520 Keywords : microwave dielectric properties * ferroelectrics * phase transitions Subject RIV: BM - Solid Matter Physics ; Magnetism

  14. Dielectric relaxation studies of methyl cellulose with phenol derivatives in non-polar solvents using time domain reflectometry

    International Nuclear Information System (INIS)

    Dielectric relaxation measurements of methyl cellulose with substituted phenols p-cresol, m-cresol and o-cresol mixture in different non-polar solvents CCl4, benzene and 1,4-dioxan for different concentrations over the frequency range of 10 MHz-20 GHz at 303 K have been carried out using Time Domain Reflectometry (TDR). Dielectric parameters such as static permittivity (ε0) and relaxation time (τ) were determined and discussed to yield information on the molecular structure and dynamics of the mixture. The dielectric constant and relaxation time were found to be high for methyl cellulose with p-cresol in CCl4 compared with the other mixtures.

  15. Polarization-independent visible wavelength filter incorporating a symmetric metal-dielectric resonant structure.

    Science.gov (United States)

    Park, Chang-Hyun; Yoon, Yeo-Taek; Lee, Sang-Shin

    2012-10-01

    A nanophotonic polarization-independent visible wavelength filter is presented, incorporating a symmetric metal-dielectric resonant structure on quartz substrate, where a sub-wavelength grating, made up of a two-dimensional array of Al square sheets, is integrated with a Si(3)N(4) slab waveguide via an oxide layer. Incident light is orthogonally diffracted by the symmetric grating towards two directions of the grating groove, and then resonantly coupled to both transverse electric and transverse magnetic guided modes associated with the underlying waveguide, irrespective of light polarization. Polarization independent bandpass filtering was thus achieved around specific wavelengths, determined by the grating pitch and the effective index of the waveguide. Three devices, operating in the blue, green and red spectral bands, were built through design and analysis drawing upon the finite-difference time-domain method. The devices, DEV I, II, and III, were constructed with grating pitches of 285, 355 and 395 nm, respectively, while the core was 100 nm thick. They were inspected to function as an efficient bandpass filter, centered at 460, 560 and 610 nm, with bandwidths of about 13, 14 and 17 nm, respectively; the peak transmission efficiencies were consistently over 85%. Furthermore, the transfer characteristics, insensitive to light polarization, were satisfactorily confirmed for normal incidence. PMID:23188342

  16. Bulk Cr tips for scanning tunneling microscopy and spin-polarized scanning tunneling microscopy

    OpenAIRE

    Bassi, A. Li; Casari, C. S.; D. Cattaneo; Donati, F.; Foglio, S.; M. Passoni; Bottani, C. E.; Biagioni, P.; Brambilla, A.; Finazzi, M.; F. Ciccacci; Duo', L.

    2007-01-01

    A simple, reliable method for preparation of bulk Cr tips for Scanning Tunneling Microscopy (STM) is proposed and its potentialities in performing high-quality and high-resolution STM and Spin Polarized-STM (SP-STM) are investigated. Cr tips show atomic resolution on ordered surfaces. Contrary to what happens with conventional W tips, rest atoms of the Si(111)-7x7 reconstruction can be routinely observed, probably due to a different electronic structure of the tip apex. SP-STM measurements of...

  17. Modelling and experimental verification of tip-induced polarization in Kelvin probe force microscopy measurements on dielectric surfaces

    DEFF Research Database (Denmark)

    Nielsen, Dennis Achton; Popok, Vladimir; Pedersen, Kjeld

    2015-01-01

    Kelvin probe force microscopy is a widely used technique for measuring surface potential distributions on the micro- and nanometer scale. The data are, however, often analyzed qualitatively, especially for dielectrics. In many cases, the phenomenon of polarization and its influence on the measured...... signals is disregarded leading to misinterpretation of the results. In this work, we present a model that allows prediction of the surface potential on a metal/polymer heterostructure as measured by Kelvin probe force microscopy by including the tip-induced polarization of the dielectric that arises...

  18. Tailoring the Dielectric Layer Structure for Enhanced Performance of Organic Field-Effect Transistors: The Use of a Sandwiched Polar Dielectric Layer

    Directory of Open Access Journals (Sweden)

    Shijiao Han

    2016-07-01

    Full Text Available To investigate the origins of hydroxyl groups in a polymeric dielectric and its applications in organic field-effect transistors (OFETs, a polar polymer layer was inserted between two polymethyl methacrylate (PMMA dielectric layers, and its effect on the performance as an organic field-effect transistor (OFET was studied. The OFETs with a sandwiched dielectric layer of poly(vinyl alcohol (PVA or poly(4-vinylphenol (PVP containing hydroxyl groups had shown enhanced characteristics compared to those with only PMMA layers. The field-effect mobility had been raised more than 10 times in n-type devices (three times in the p-type one, and the threshold voltage had been lowered almost eight times in p-type devices (two times in the n-type. The on-off ratio of two kinds of devices had been enhanced by almost two orders of magnitude. This was attributed to the orientation of hydroxyl groups from disordered to perpendicular to the substrate under gate-applied voltage bias, and additional charges would be induced by this polarization at the interface between the semiconductor and dielectrics, contributing to the accumulation of charge transfer.

  19. Monolithic integrated system with an electrowetting-on-dielectric actuator and a film-bulk-acoustic-resonator sensor

    International Nuclear Information System (INIS)

    Although digital microfluidics has shown great potential in a wide range of applications, a lab-on-a-chip with integrated digital droplet actuators and powerful biochemical sensors is still lacking. To address the demand, a fully integrated chip with electrowetting-on-dielectric (EWOD) and a film bulk acoustic resonator (FBAR) sensor is introduced, where an EWOD actuator manipulates digital droplets and the FBAR sensor detects the presence of substances in the droplets, respectively. The piezoelectric layer of the FBAR sensor and the dielectric layer of the EWOD share the same aluminum nitride (AlN) thin film, which is a key factor to achieve the full integration of the two completely different devices. The liquid droplets are reliably managed by the EWOD actuator to sit on or move off the FBAR sensor precisely. Sessile drop experiments and limit of detection (LOD) experiments are carried out to characterize the EWOD actuator and the FBAR sensor, respectively. Taking advantage of the digital droplet operation, a ‘dry sensing mode’ of the FBAR sensor in the lab-on-a-chip microsystem is proposed, which has a much higher signal to noise ratio than the conventional ‘wet sensing mode’. Hg2+ droplets with various concentrations are transported and sensed to demonstrate the capability of the integrated system. The EWOD–FBAR chip is expected to play an important role in many complex lab-on-a-chip applications. (paper)

  20. Monolithic integrated system with an electrowetting-on-dielectric actuator and a film-bulk-acoustic-resonator sensor

    Science.gov (United States)

    Zhang, Menglun; Cui, Weiwei; Chen, Xuejiao; Wang, Chao; Pang, Wei; Duan, Xuexin; Zhang, Daihua; Zhang, Hao

    2015-02-01

    Although digital microfluidics has shown great potential in a wide range of applications, a lab-on-a-chip with integrated digital droplet actuators and powerful biochemical sensors is still lacking. To address the demand, a fully integrated chip with electrowetting-on-dielectric (EWOD) and a film bulk acoustic resonator (FBAR) sensor is introduced, where an EWOD actuator manipulates digital droplets and the FBAR sensor detects the presence of substances in the droplets, respectively. The piezoelectric layer of the FBAR sensor and the dielectric layer of the EWOD share the same aluminum nitride (AlN) thin film, which is a key factor to achieve the full integration of the two completely different devices. The liquid droplets are reliably managed by the EWOD actuator to sit on or move off the FBAR sensor precisely. Sessile drop experiments and limit of detection (LOD) experiments are carried out to characterize the EWOD actuator and the FBAR sensor, respectively. Taking advantage of the digital droplet operation, a ‘dry sensing mode’ of the FBAR sensor in the lab-on-a-chip microsystem is proposed, which has a much higher signal to noise ratio than the conventional ‘wet sensing mode’. Hg2+ droplets with various concentrations are transported and sensed to demonstrate the capability of the integrated system. The EWOD-FBAR chip is expected to play an important role in many complex lab-on-a-chip applications.

  1. Polarity Determination using Opinion Mining in Stocks and Shares-advertising Unsolicited Bulk e-mails

    Directory of Open Access Journals (Sweden)

    Dr. Jatinderkumar R. Saini

    2012-04-01

    Full Text Available e-mail has become an important means of electronic communication but the viability of its usage is marred by Un-solicited Bulk e-mail (UBE messages. UBE consists of many types like pornographic, virus infected messages, ‘cry-for-help’ messages as well as fake and fraudulent offers/advertisements/promotions of stocks and shares, jobs, winnings, and medicines. UBE poses technical and socio-economic challenges to usage of e-mails. To meet this challenge and combat this menace, we need to understand UBE. Towards this end, a content-based textual analysis of more than 3100 stocks and shares-advertising unstructured UBE documents is presented. The paper is aimed at polarity determination of such UBE through its sentiment analysis. Technically, this is an application of Opinion Mining approached with help of Text Parsing, Tokenization, BOW and VSDM techniques. Sentiment Analysis is used to determine the polarity of the document because such UBE contain opinion of the spammer about specific stock symbol of share market. The Sentiment-depicting words are analyzed in the UBE corpus, scaled and extremes of positive and negative opinions are identified. An attempt has been made for polarity-based distribution of such UBE. It has been found that for almost 50�0of cases, the opinions expressed through such UBE have positive polarity, almost 30�0cases are negatively opined whereas almost 20�0cases contain neutral opinion. To the best knowledge and based on review of related literature, determination of UBE polarity using Opinion Mining for understanding spammer behaviour is a new concept.

  2. Dynamic polarization effects on the angular distributions of protons channeled through carbon nanotubes in dielectric media

    CERN Document Server

    Borka, D; Mišković, Z L; Petrović, S; Nešković, N

    2008-01-01

    The best level of ordering and straightening of carbon nanotube arrays is often achieved when they are grown in a dielectric matrix, so such structures present the most suitable candidates for future channeling experiments with carbon nanotubes. Consequently, we investigate here how the dynamic polarization of carbon valence electrons in the presence of various surrounding dielectric media affects the angular distributions of protons channeled through (11,~9) single-wall carbon nanotubes. Proton speeds between 3 and 10 a.u., corresponding to energies of 0.223 and 2.49 MeV, are chosen with the nanotube's length varied between 0.1 and 1 $\\mu$m. We describe the repulsive interaction between a proton and the nanotube's atoms in a continuum-potential approximation based on the Doyle-Turner potential, whereas the attractive image force on a proton is calculated using a two-dimensional hydrodynamic model for the dynamic response of the nanotube valence electrons, while assigning to the surrounding medium an appropri...

  3. Extraction of Water from Polar Lunar Permafrost with Microwaves - Dielectric Property Measurements

    Science.gov (United States)

    Ethridge, Edwin C.; Kaukler, William

    2009-01-01

    Remote sensing indicates the presence of hydrogen rich regions associated with the lunar poles. The logical hypothesis is that there is cryogenically trapped water ice located in craters at the lunar poles. Some of the craters have been in permanent darkness for a billion years. The presence of water at the poles as well as other scientific advantages of a polar base, have influenced NASA plans for the lunar outpost. The lunar outpost has water and oxygen requirements on the order of 1 ton per year scaling up to as much as 10 tons per year. Microwave heating of the frozen permafrost has unique advantages for water extraction. Proof of principle experiments have successfully demonstrated that microwaves will couple to the cryogenic soil in a vacuum and the sublimed water vapor can be successfully captured on a cold trap. The dielectric properties of lunar soil will determine the hardware requirements for extraction processes. Microwave frequency dielectric property measurements of lunar soil simulant have been measured.

  4. Compensating for Electrode Polarization in Dielectric Spectroscopy Studies of Colloidal Suspensions: Theoretical Assessment of Existing Methods

    Science.gov (United States)

    Chassagne, Claire; Dubois, Emmanuelle; Jiménez, María L.; van der Ploeg, J. P. M; van Turnhout, Jan

    2016-01-01

    Dielectric spectroscopy can be used to determine the dipole moment of colloidal particles from which important interfacial electrokinetic properties, for instance their zeta potential, can be deduced. Unfortunately, dielectric spectroscopy measurements are hampered by electrode polarization (EP). In this article, we review several procedures to compensate for this effect. First EP in electrolyte solutions is described: the complex conductivity is derived as function of frequency, for two cell geometries (planar and cylindrical) with blocking electrodes. The corresponding equivalent circuit for the electrolyte solution is given for each geometry. This equivalent circuit model is extended to suspensions. The complex conductivity of a suspension, in the presence of EP, is then calculated from the impedance. Different methods for compensating for EP are critically assessed, with the help of the theoretical findings. Their limit of validity is given in terms of characteristic frequencies. We can identify with one of these frequencies the frequency range within which data uncorrected for EP may be used to assess the dipole moment of colloidal particles. In order to extract this dipole moment from the measured data, two methods are reviewed: one is based on the use of existing models for the complex conductivity of suspensions, the other is the logarithmic derivative method. An extension to multiple relaxations of the logarithmic derivative method is proposed. PMID:27486575

  5. A Single-Point-Fed Wideband Circularly Polarized Rectangular Dielectric Resonator Antenna

    Directory of Open Access Journals (Sweden)

    Deqiang Yang

    2016-01-01

    Full Text Available A single-point-fed circularly polarized (CP rectangular dielectric resonator antenna (DRA with wide CP bandwidth is presented. By using TE111 and TE113 modes of the rectangular DRA, a wideband CP performance is achieved. The coupling slot of the antenna contains a resistor loaded monofilar-spiral-slot and four linear slots. Design concept of the proposed antenna is demonstrated by simulations, and parameter studies are carried out. Prototype of the proposed antenna was fabricated and measured. Good agreement between the simulation and measurement is obtained. The measured impedance bandwidth (|S11|<-10 dB and 3 dB axial-ratio (AR bandwidth are 51.4% (1.91–3.23 GHz and 33.0% (2.15–3.00 GHz, respectively.

  6. 2 MeV electron irradiation effects on bulk and interface of atomic layer deposited high-k gate dielectrics on silicon

    International Nuclear Information System (INIS)

    2 MeV electron irradiation effects on the electrical properties of Al2O3 and HfO2-based metal–insulator–semiconductor capacitors have been studied. High-k dielectrics were directly grown on silicon by atomic layer deposition. Capacitors were exposed to three different electron irradiation doses of 0.025, 0.25 and 2.5 MGy. Capacitance–voltage, deep-level transient spectroscopy, conductance transients, flat-band voltage transients and current–voltage techniques were used to characterize the defects induced or activated by irradiation on the dielectric bulk and on the interface with silicon substrate. In all cases, positive charge is trapped in the dielectric bulk after irradiation indicating the existence of hole traps in the dielectric. When the samples are exposed to 2 MeV electron beam (e-beam) irradiation, electron–hole pairs are created and holes are then captured by the hole traps. Insulator/semiconductor interface quality slightly improves for low irradiation doses, but it is degraded for high doses. Irradiation always degrades the dielectric layers in terms of gate leakage current: the trapped holes are mobile charge which can contribute to leakage current by hopping from trap to trap. - Highlights: ► Positive charge accumulates inside dielectrics after electron irradiation. ► Irradiation improves oxide/semiconductor interface for low doses. ► Irradiation increases gate leakage current

  7. 2 MeV electron irradiation effects on bulk and interface of atomic layer deposited high-k gate dielectrics on silicon

    Energy Technology Data Exchange (ETDEWEB)

    García, H., E-mail: hecgar@ele.uva.es [Departamento de Electricidad y Electrónica, ETSI Telecomunicación, Universidad de Valladolid, 47011 Valladolid (Spain); Castán, H.; Dueñas, S.; Bailón, L. [Departamento de Electricidad y Electrónica, ETSI Telecomunicación, Universidad de Valladolid, 47011 Valladolid (Spain); Campabadal, F.; Rafí, J.M.; Zabala, M.; Beldarrain, O. [Institut de Microelectrònica de Barcelona (IMB-CNM), CSIC, Campus UAB, 08193 Bellaterra (Spain); Ohyama, H.; Takakura, K.; Tsunoda, I. [Department of Electronic Engineering, Kumamoto National College of Technology, Kumamoto 861-1102 (Japan)

    2013-05-01

    2 MeV electron irradiation effects on the electrical properties of Al{sub 2}O{sub 3} and HfO{sub 2}-based metal–insulator–semiconductor capacitors have been studied. High-k dielectrics were directly grown on silicon by atomic layer deposition. Capacitors were exposed to three different electron irradiation doses of 0.025, 0.25 and 2.5 MGy. Capacitance–voltage, deep-level transient spectroscopy, conductance transients, flat-band voltage transients and current–voltage techniques were used to characterize the defects induced or activated by irradiation on the dielectric bulk and on the interface with silicon substrate. In all cases, positive charge is trapped in the dielectric bulk after irradiation indicating the existence of hole traps in the dielectric. When the samples are exposed to 2 MeV electron beam (e-beam) irradiation, electron–hole pairs are created and holes are then captured by the hole traps. Insulator/semiconductor interface quality slightly improves for low irradiation doses, but it is degraded for high doses. Irradiation always degrades the dielectric layers in terms of gate leakage current: the trapped holes are mobile charge which can contribute to leakage current by hopping from trap to trap. - Highlights: ► Positive charge accumulates inside dielectrics after electron irradiation. ► Irradiation improves oxide/semiconductor interface for low doses. ► Irradiation increases gate leakage current.

  8. Dielectric relaxation of binary polar liquid mixture measured in benzene at 10 GHz frequency

    Indian Academy of Sciences (India)

    S Sahoo; K Dutta; S Acharyya; S K Sit

    2008-03-01

    The dielectric relaxation times 's and dipole moments 's of the binary () polar liquid mixture of N,N-dimethyl acetamide (DMA) and acetone (Ac) dissolved in benzene (i) are estimated from the measured real ′ and imaginary ″ parts of complex high frequency conductivity * of the solution for different weight fractions 's of 0.0, 0.3, 0.5, 0.7 and 1.0 mole fractions of Ac and temperatures (25, 30, 35 and 40°C) respectively under 9.88 GHz electric field. 's are obtained from the ratio of slopes of ″ - and ′ - curves at → 0 as well as linear slope of ″ - ′ curves of the existing method (Murthy et al, 1989) in order to eliminate polar-polar interaction in the latter case. The calculated 's are in excellent agreement with the reported 's due to Gopalakrishna's method. 's are also estimated from slopes 's of total conductivity - curves at → 0 and the values agree well with the reported 's from G.K. method. The variation of 's and 's with of Ac reveals that solute-solute molecular association occurs within 0.0-0.3 of Ac beyond which solute-solvent molecular association is predicted. The theoretical dipole moments theo's are calculated from bond angles and bond moments to have exact 's only to show the presence of inductive, mesomeric and electromeric effects in the substituent polar groups. The thermodynamic energy parameters are estimated from ln () against 1/ linear curve from Eyring's rate theory to know the molecular dynamics of the system and to establish the fact that the mixture obeys the Debye-Smyth relaxation mechanism.

  9. Surface and bulk scattering by magnetic and dielectric inhomogeneities: a first-order method.

    Science.gov (United States)

    Dieudonné, É; Malléjac, N; Amra, C; Enoch, S

    2013-09-01

    The scattering of a magnetodielectric multilayer has been studied by a first-order method. The model reported in this manuscript relies on the equivalence between heterogeneities of the medium and fictitious electric and magnetic sources. Types of inhomogeneities considered are roughness and bulk inhomogeneities and concern both permittivity and permeability. The numerical results are compared to those given in previous papers for optical scattering. It is shown in the microwave spectra that angle-resolved scattering allows identification of the scattering origins (permittivity or permeability spectra). The cases of isotropic films and metamaterials are presented and discussed. PMID:24323258

  10. Surface passivation and interface properties of bulk GaAs and epitaxial-GaAs/Ge using atomic layer deposited TiAlO alloy dielectric.

    Science.gov (United States)

    Dalapati, G K; Chia, C K; Tan, C C; Tan, H R; Chiam, S Y; Dong, J R; Das, A; Chattopadhyay, S; Mahata, C; Maiti, C K; Chi, D Z

    2013-02-01

    High quality surface passivation on bulk-GaAs substrates and epitaxial-GaAs/Ge (epi-GaAs) layers were achieved by using atomic layer deposited (ALD) titanium aluminum oxide (TiAlO) alloy dielectric. The TiAlO alloy dielectric suppresses the formation of defective native oxide on GaAs layers. X-ray photoelectron spectroscopy (XPS) analysis shows interfacial arsenic oxide (As(x)O(y)) and elemental arsenic (As) were completely removed from the GaAs surface. Energy dispersive X-ray diffraction (EDX) analysis and secondary ion mass spectroscopy (SIMS) analysis showed that TiAlO dielectric is an effective barrier layer for reducing the out-diffusion of elemental atoms, enhancing the electrical properties of bulk-GaAs based metal-oxide-semiconductor (MOS) devices. Moreover, ALD TiAlO alloy dielectric on epi-GaAs with AlGaAs buffer layer realized smooth interface between epi-GaAs layers and TiAlO dielectric, yielding a high quality surface passivation on epi-GaAs layers, much sought-after for high-speed transistor applications on a silicon platform. Presence of a thin AlGaAs buffer layer between epi-GaAs and Ge substrates improved interface quality and gate dielectric quality through the reduction of interfacial layer formation (Ga(x)O(y)) and suppression of elemental out-diffusion (Ga and As). The AlGaAs buffer layer and TiAlO dielectric play a key role to suppress the roughening, interfacial layer formation, and impurity diffusion into the dielectric, which in turn largely enhances the electrical property of the epi-GaAs MOS devices. PMID:23331503

  11. Low temperature y-ray spectrometers based on bulk superconducting and dielectric absorber crystals

    Energy Technology Data Exchange (ETDEWEB)

    Netel, H

    1999-11-19

    Many areas of research rely on the detection of radiation, in the form of single photons or particles. By measuring the photons or particles coming from an object a lot can be learned about the object under study. In some cases there is a simple need to know the number of photons coming from the source. In cases like this a simple counter, like a Geiger-Mueller survey meter, will suffice. In other cases one want to know the spectral distribution of the photons coming from the source. In cases like that a spectrometer is needed that can distinguish between photons with different energies, like a diffraction or transmission grating. The work presented in this thesis focused on the development of a new generation broad band spectrometer that has a high energy resolving power, combined with a high absorption efficiency for photon energies above 10 keV and up to 500 keV. The spectrometers we are developing are based on low-temperature sensors, like superconducting tunnel junctions or transition edge sensors, that are coupled to bulk absorber crystals. We use the low-temperature sensors because they can offer a significant improvement in energy resolving power, compared to conventional spectrometers. We couple the low-temperature sensors to bulk absorber crystals to increase the absorption efficiency. In this chapter I introduce different types of radiation detectors and spectrometers and areas where they are being used. I also discuss the history and motivation of low-temperature spectrometers and show some of the impressive results that have been achieved in this field over the last few years. Finally I discuss the outline of this thesis.

  12. Influence of void geometry and bulk dielectric polarization upon PD transients

    DEFF Research Database (Denmark)

    McAllister, Iain Wilson; Crichton, George C

    A physically valid theory of partial dischargetransients has been developed using a field theoretical approach. The theory is based upon the concept of the charge induced upon the detecting electrode by the partial discharge. Mathematically this induced charge is composed of a component associated...

  13. Spontaneous Polarization and Bulk Photovoltaic Effect Driven by Polar Discontinuity in LaFeO3 /SrTiO3 Heterojunctions

    Science.gov (United States)

    Nakamura, M.; Kagawa, F.; Tanigaki, T.; Park, H. S.; Matsuda, T.; Shindo, D.; Tokura, Y.; Kawasaki, M.

    2016-04-01

    Structurally coherent and chemically abrupt interfaces formed between polar and nonpolar perovskite oxides provide an ideal platform for examining the purely electronic reconstruction known as the polar catastrophe and the emergence of mobile or bound charges at the interface. The appearance of mobile charges induced by the polar catastrophe is already established in the LaAlO3 /SrTiO3 heterojunctions. Although not experimentally verified, the polar catastrophe can also lead to the emergence of spontaneous polarization. We report that thin films of originally nonpolar LaFeO3 grown on SrTiO3 are converted to polar as a consequence of the polar catastrophe. The induced spontaneous polarization evokes photovoltaic properties distinct from conventional p -n junctions, such as a switching of the photocurrent direction by changing the interfacial atomic sequence. The control of the bulk polarization by engineering the interface demonstrated here will expand the possibilities for designing and realizing new polar materials with photovoltaic functions.

  14. Electrical analysis of high dielectric constant insulator and metal gate metal oxide semiconductor capacitors on flexible bulk mono-crystalline silicon

    KAUST Repository

    Ghoneim, Mohamed T.

    2015-06-01

    We report on the electrical study of high dielectric constant insulator and metal gate metal oxide semiconductor capacitors (MOSCAPs) on a flexible ultra-thin (25 μm) silicon fabric which is peeled off using a CMOS compatible process from a standard bulk mono-crystalline silicon substrate. A lifetime projection is extracted using statistical analysis of the ramping voltage (Vramp) breakdown and time dependent dielectric breakdown data. The obtained flexible MOSCAPs operational voltages satisfying the 10 years lifetime benchmark are compared to those of the control MOSCAPs, which are not peeled off from the silicon wafer. © 2014 IEEE.

  15. Polarization and Dielectric Study of Methylammonium Lead Iodide Thin Film to Reveal its Nonferroelectric Nature under Solar Cell Operating Conditions

    Energy Technology Data Exchange (ETDEWEB)

    Hoque, Md Nadim Ferdous; Yang, Mengjin; Li, Zhen; Islam, Nazifah; Pan, Xuan; Zhu, Kai; Fan, Zhaoyang

    2016-07-08

    Researchers have debated whether methylammonium lead iodide (MAPbI3), with a perovskite crystal structure, is ferroelectric and therefore contributes to the current--voltage hysteresis commonly observed in hybrid perovskite solar cells (PSCs). We thoroughly investigated temperature-dependent polarization, dielectric, and impedance spectroscopies, and we found no evidence of ferroelectric effect in a MAPbI3 thin film at normal operating conditions. Therefore, the effect does not contribute to the hysteresis in PSCs, whereas the large component of ionic migration observed may play a critical role. Our temperature-based polarization and dielectric studies find that MAPbI3 exhibits different electrical behaviors below and above ca. 45 degrees C, suggesting a phase transition around this temperature. In particular, we report the activation energies of ionic migration for the two phases and temperature-dependent permittivity of MAPbI3. This study contributes to the understanding of the material properties and device performance of hybrid perovskites.

  16. Single Feed Aperture-Coupled Wideband Dielectric Resonator Antenna with Circular Polarization for Ku-Band Applications

    Directory of Open Access Journals (Sweden)

    Joshua M. Patin

    2012-01-01

    Full Text Available A novel single feed aperture-coupled wideband dielectric resonator antenna (DRA exhibiting righ-handed circular polarization (RHCP operating in the Ku-band frequency range is presented. The aperture-coupled single feed design utilizes back-side microstrip excitation through a novel bow-tie-shaped cross-slots in the ground plane. Extensive simulation parametric studies resulted in a 3 dB axial ratio (AR bandwidth of 17.24% at a center frequency of 13 GHz, where the dielectric resonator is excited in its HEM11δ resonant mode. A prototype DRA was fabricated with some limitations and experimentally verified for the impedance matching and radiation patterns showing circular polarization.

  17. Correction of electrode polarization contributions to the dielectric properties of normal and cancerous breast tissues at audio/radiofrequencies

    International Nuclear Information System (INIS)

    Spurious contributions from electrode polarization (EP) are a major nuisance in dielectric measurements of biological tissues and hamper accurate determination of tissue properties in the audio/radiofrequencies. Various electrode geometries and/or treatments have been employed traditionally to reduce EP contributions, although none succeeded to completely remove EP from measurements on tissues for all practical frequency ranges. A method of correction for contributions of EP to the dielectric properties of tissues is proposed. The method is based on modeling the electrode impedance with suitable functions and on the observation that certain parameters are only dependent on electrodes properties and can thus be determined separately. The method is tested on various samples with known properties, and its usefulness is demonstrated with samples of normal and cancerous human female breast tissue. It is observed that the dielectric properties of the tissues over the frequency range 40 Hz-100 MHz are significantly different among different types of breast tissue. This observation is used further to demonstrate that, by scanning the tip of the measuring dielectric probe (with modest spatial resolution) across a sample of excised breast tissue, significant variations in the electrical properties are detected at a position where a tumor is located. This study shows that dielectric spectroscopy has the potential to offer a viable alternative to the current methods for detection of breast cancer in vivo

  18. Modelling and experimental verification of tip-induced polarization in Kelvin probe force microscopy measurements on dielectric surfaces

    OpenAIRE

    Nielsen, Dennis Achton; Popok, Vladimir; Pedersen, Kjeld

    2015-01-01

    Kelvin probe force microscopy is a widely used technique for measuring surface potential distributions on the micro- and nanometer scale. The data are, however, often analyzed qualitatively, especially for dielectrics. In many cases, the phenomenon of polarization and its influence on the measured signals is disregarded leading to misinterpretation of the results. In this work, we present a model that allows prediction of the surface potential on a metal/polymerheterostructure as measured by ...

  19. Impact of Molecular Orientation and Packing Density on Electronic Polarization in the Bulk and at Surfaces of Organic Semiconductors

    KAUST Repository

    Ryno, Sean M.

    2016-05-16

    The polarizable environment surrounding charge carriers in organic semiconductors impacts the efficiency of the charge transport process. Here, we consider two representative organic semiconductors, tetracene and rubrene, and evaluate their polarization energies in the bulk and at the organic-vacuum interface using a polarizable force field that accounts for induced-dipole and quadrupole interactions. Though both oligoacenes pack in a herringbone motif, the tetraphenyl substituents on the tetracene backbone of rubrene alter greatly the nature of the packing. The resulting change in relative orientations of neighboring molecules is found to reduce the bulk polarization energy of holes in rubrene by some 0.3 eV when compared to tetracene. The consideration of model organic-vacuum interfaces highlights the significant variation in the electrostatic environment for a charge carrier at a surface although the net change in polarization energy is small; interestingly, the environment of a charge even just one layer removed from the surface can be viewed already as representative of the bulk. Overall, it is found that in these herringbone-type layered crystals the polarization energy has a much stronger dependence on the intralayer packing density than interlayer packing density.

  20. Impact of Molecular Orientation and Packing Density on Electronic Polarization in the Bulk and at Surfaces of Organic Semiconductors.

    Science.gov (United States)

    Ryno, Sean M; Risko, Chad; Brédas, Jean-Luc

    2016-06-01

    The polarizable environment surrounding charge carriers in organic semiconductors impacts the efficiency of the charge transport process. Here, we consider two representative organic semiconductors, tetracene and rubrene, and evaluate their polarization energies in the bulk and at the organic-vacuum interface using a polarizable force field that accounts for induced-dipole and quadrupole interactions. Though both oligoacenes pack in a herringbone motif, the tetraphenyl substituents on the tetracene backbone of rubrene alter greatly the nature of the packing. The resulting change in relative orientations of neighboring molecules is found to reduce the bulk polarization energy of holes in rubrene by some 0.3 eV when compared to tetracene. The consideration of model organic-vacuum interfaces highlights the significant variation in the electrostatic environment for a charge carrier at a surface although the net change in polarization energy is small; interestingly, the environment of a charge even just one layer removed from the surface can be viewed already as representative of the bulk. Overall, it is found that in these herringbone-type layered crystals the polarization energy has a much stronger dependence on the intralayer packing density than interlayer packing density. PMID:27183361

  1. Hexatic and blue phases in a chiral liquid crystal: optical polarizing microscopy, synchrotron radiation and dielectric study

    International Nuclear Information System (INIS)

    Phase behavior, structure and molecular dynamics of a chiral liquid crystalline compound, which exhibits SmG*, SmJ*, SmF*, SmI*, SmC*, SmA*, N* and BP*, have been investigated. Observed optical textures, synchrotron radiation diffraction data and frequency dependent dielectric spectroscopic study clearly depict the temperature evolution of the different hexatic smectic phases along with cholesteric and blue phase in a single compound. In hexatic phases dielectric absorption spectra show one low frequency relaxation process, related to the phase fluctuation of the bond orientational order, and one high frequency process related to amplitude fluctuation of the bond orientational order coupled with the polarization and tilt of the molecules. Goldstone and soft mode relaxation processes are detected, respectively, in SmC* and SmA* phases. (paper)

  2. High linearly polarized light emission from GaN-based LED with patterned dielectric/metal structures

    Science.gov (United States)

    Wang, Miao; Cao, Bing; Xu, Fuyang; Hu, Jingpei; Wang, Jianfeng; Xu, Ke; Wang, Chinhua

    2015-07-01

    We proposed and demonstrated an integrated high linearly polarized InGaN/GaN green LED grown on (0001) oriented sapphire with a structure of combined dielectric/metal wire grids (CDMWG). Both theoretical and experimental results show that the CDMWG can effectively loosen the requirement on the dimension of the grating, and the introduction of a low-refractive dielectric layer can further enhance both TMT and ER significantly for the GaN-type LED. An InGaN/ GaN green LED with an integrated CDMWG of 220 nm period has been fabricated, and a measured extinction ratio(ER) of higher than 20 dB and TMT of 65% within an angle of +/-40° is obtained directly from a InGaN/GaN LED.

  3. Cavity-water interface is polar

    OpenAIRE

    Friesen, Allan D.; Matyushov, Dmitry V.

    2010-01-01

    We present the results of numerical simulations of the electrostatics and dynamics of water hydration shells surrounding Kihara cavities given by a Lennard-Jones (LJ) layer at the surface of a hard-sphere cavity. The local dielectric response of the hydration layer substantially exceeds that of bulk water, with the magnitude of the dielectric constant peak in the shell increasing with the growing cavity size. The polar shell propagates into bulk water to approximately the cavity radius. The s...

  4. Quasi 2D electronic states with high spin-polarization in centrosymmetric MoS2 bulk crystals

    Science.gov (United States)

    Gehlmann, Mathias; Aguilera, Irene; Bihlmayer, Gustav; Młyńczak, Ewa; Eschbach, Markus; Döring, Sven; Gospodarič, Pika; Cramm, Stefan; Kardynał, Beata; Plucinski, Lukasz; Blügel, Stefan; Schneider, Claus M.

    2016-06-01

    Time reversal dictates that nonmagnetic, centrosymmetric crystals cannot be spin-polarized as a whole. However, it has been recently shown that the electronic structure in these crystals can in fact show regions of high spin-polarization, as long as it is probed locally in real and in reciprocal space. In this article we present the first observation of this type of compensated polarization in MoS2 bulk crystals. Using spin- and angle-resolved photoemission spectroscopy (ARPES), we directly observed a spin-polarization of more than 65% for distinct valleys in the electronic band structure. By additionally evaluating the probing depth of our method, we find that these valence band states at the point in the Brillouin zone are close to fully polarized for the individual atomic trilayers of MoS2, which is confirmed by our density functional theory calculations. Furthermore, we show that this spin-layer locking leads to the observation of highly spin-polarized bands in ARPES since these states are almost completely confined within two dimensions. Our findings prove that these highly desired properties of MoS2 can be accessed without thinning it down to the monolayer limit.

  5. Semiempirical self-consistent polarization description of bulk water, the liquid-vapor interface, and cubic ice.

    Science.gov (United States)

    Murdachaew, Garold; Mundy, Christopher J; Schenter, Gregory K; Laino, Teodoro; Hutter, Jürg

    2011-06-16

    We have applied an efficient electronic structure approach, the semiempirical self-consistent polarization neglect of diatomic differential overlap (SCP-NDDO) method, previously parametrized to reproduce properties of water clusters by Chang, Schenter, and Garrett [ J. Chem. Phys. 2008 , 128 , 164111 ] and now implemented in the CP2K package, to model ambient liquid water at 300 K (both the bulk and the liquid-vapor interface) and cubic ice at 15 and 250 K. The SCP-NDDO potential retains its transferability and good performance across the full range of conditions encountered in the clusters and the bulk phases of water. In particular, we obtain good results for the density, radial distribution functions, enthalpy of vaporization, self-diffusion coefficient, molecular dipole moment distribution, and hydrogen bond populations, in comparison to experimental measurements. PMID:21370904

  6. Polarization Dependence of Born Effective Charge and Dielectric Constant in KNbO$_3$

    OpenAIRE

    Wang, Cheng-Zhang; Yu, Rici; Krakauer, Henry

    1996-01-01

    The Born effective charge Z^{*} and dielectric tensor \\epsilon_{\\infty} of KNbO_3 are found to be very sensitive to the atomic geometry, changing by as much as 27% between the paraelectric cubic and ferroelectric tetragonal and rhombohedral phases. Subtracting the bare ionic contribution reveals changes of the dynamic component of Z^{*} as large as 50%, for atomic displacements that are typically only a few percent of the lattice constant. Z^{*}, \\epsilon_{\\infty} and all phonon frequencies a...

  7. Surface and bulk sensitive measurements of polarized XANES using synchrotron radiation

    International Nuclear Information System (INIS)

    XANES ( X-ray Absorption Near Edge Structure) with polarized synchrotron light is now established to be one of the important techniques for the study of electronic structure of HTc superconductors in respect of finding out the symmetry of holes and their implication to the theoretical model proposed to explain superconductivity in these cuprates. The XANES spectra measured by two methods namely, total yield (TY) and fluorescence yield (FY) have given different results in respect of out-of-plane Cu 3d symmetry holes. The reason of this discrepancy is still unclear. In this communication, we report our polarized XANES measurements on Bi-2212 single crystal at the Cu L3 edge by TY and FY methods and discuss the results in detail. (author). 19 refs., 5 figs

  8. Towards low-loss, infrared and THz nanophotonics and metamaterials: surface phonon polariton modes in polar dielectric crystals (Presentation Recording)

    Science.gov (United States)

    Caldwell, Joshua D.; Lindsey, Lucas; Giannini, Vincenzo; Vurgaftman, Igor; Reinecke, Thomas L.; Maier, Stefan A.; Glembocki, Orest J.

    2015-09-01

    The field of nanophotonics is based on the ability to confine light to sub-diffractional dimensions. Up until recently, research in this field has been primarily focused on the use of plasmonic metals. However, the high optical losses inherent in such metal-based surface plasmon materials has led to an ever-expanding effort to identify, low-loss alternative materials capable of supporting sub-diffractional confinement. One highly promising alternative are polar dielectric crystals whereby sub-diffraction confinement of light can be achieved through the stimulation of surface phonon polaritons within an all-dielectric, and thus low loss material system. Both SiC and hexagonal BN are two exemplary SPhP systems, which along with a whole host of alternative materials promise to transform nanophotonics and metamaterials in the mid-IR to THz spectral range. In addition to the lower losses, these materials offer novel opportunities not available with traditional plasmonics, for instance hyperbolic optical behavior in natural materials such as hBN, enabling super-resolution imaging without the need for complex fabrication. This talk will provide an overview of the SPhP phenomenon, a discussion of what makes a `good' SPhP material and recent results from SiC and the naturally hyperbolic material, hBN from our research group.

  9. The Hartman paradox and new model of scattering the plane TE polarized light wave on a dielectric layer

    CERN Document Server

    Chuprikov, N L

    2011-01-01

    The problem of describing the temporal aspects of scattering the plane light wave on an uniform dielectric layer is reconsidered. In the standard model of this scattering process a correct definition of the transmission (tunneling) time is impossible in principle, because it does not provide a complete description of the transmitted wave in all stages of scattering. The latter is the main reason to lead to the Hartman paradox, in the standard model, in introducing the transmission time in the case of a frustrated total internal reflection (FTIR). We present an alternative model of scattering the plane TE polarized light wave, which treats this process as a complex one consisting of two subprocesses (transmission and reflection), with their individual description in all stages of scattering. The transmission velocity of the TE wave, introduced as the velocity of transferring its {\\it energy} through the layer, obeys two requirements (violated in the standard approach): (\\i) it respects the principles of relati...

  10. Improved linearity in AlGaN/GaN metal-insulator-semiconductor high electron mobility transistors with nonlinear polarization dielectric

    International Nuclear Information System (INIS)

    We demonstrate highly improved linearity in a nonlinear ferroelectric of Pb(Zr0.52Ti0.48)-gated AlGaN/GaN metal-insulator-semiconductor high electron mobility transistor (MIS-HEMT). Distinct double-hump feature in the transconductance-gate voltage (gm-Vg) curve is observed, yielding remarkable enhancement in gate voltage swing as compared to MIS-HEMT with conventional linear gate dielectric. By incorporating the ferroelectric polarization into a self-consistent calculation, it is disclosed that in addition to the common hump corresponding to the onset of electron accumulation, the second hump at high current level is originated from the nonlinear polar nature of ferroelectric, which enhances the gate capacitance by increasing equivalent dielectric constant nonlinearly. This work paves a way for design of high linearity GaN MIS-HEMT by exploiting the nonlinear properties of dielectric

  11. Improved linearity in AlGaN/GaN metal-insulator-semiconductor high electron mobility transistors with nonlinear polarization dielectric

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Tao [Fundamental Science on EHF Laboratory, University of Electronic Science and Technology of China (UESTC), Chengdu 611731 (China); Science and Technology on Monolithic Integrated Circuits and Modules Laboratory, Nanjing Electronic Devices Institute, Nanjing 210016 (China); Xu, Ruimin [Fundamental Science on EHF Laboratory, University of Electronic Science and Technology of China (UESTC), Chengdu 611731 (China); Kong, Yuechan, E-mail: kycfly@163.com; Zhou, Jianjun; Kong, Cen; Dong, Xun; Chen, Tangsheng [Science and Technology on Monolithic Integrated Circuits and Modules Laboratory, Nanjing Electronic Devices Institute, Nanjing 210016 (China)

    2015-06-15

    We demonstrate highly improved linearity in a nonlinear ferroelectric of Pb(Zr{sub 0.52}Ti{sub 0.48})-gated AlGaN/GaN metal-insulator-semiconductor high electron mobility transistor (MIS-HEMT). Distinct double-hump feature in the transconductance-gate voltage (g{sub m}-V{sub g}) curve is observed, yielding remarkable enhancement in gate voltage swing as compared to MIS-HEMT with conventional linear gate dielectric. By incorporating the ferroelectric polarization into a self-consistent calculation, it is disclosed that in addition to the common hump corresponding to the onset of electron accumulation, the second hump at high current level is originated from the nonlinear polar nature of ferroelectric, which enhances the gate capacitance by increasing equivalent dielectric constant nonlinearly. This work paves a way for design of high linearity GaN MIS-HEMT by exploiting the nonlinear properties of dielectric.

  12. Multiwalled carbon nanotubes for dielectric sensing of biological systems: An effective treatment of polarization

    Science.gov (United States)

    Picaud, F.; Girardet, C.

    We determine the efficiency of semi-conducting multiwalled carbon nanotubes in resonator configuration acting as sensors of biological systems. The resonance frequency shifts due to the dielectric changes of the resonator upon adsorption of highly idealized micelles schematized by a set of concentric shells of polarizable centers surrounded by a water shell to mimic the solvent are calculated on the basis of an effective polarizability distribution in the tube and the sensed system. Cylindrical and spherical geometries including different sizes are considered for the micelles to show that size and geometry selectivity could be reached with such an approach.

  13. Dielectric function and magneto-optical Voigt constant of Cu2O: A combined spectroscopic ellipsometry and polar magneto-optical Kerr spectroscopy study

    Science.gov (United States)

    Haidu, Francisc; Fronk, Michael; Gordan, Ovidiu D.; Scarlat, Camelia; Salvan, Georgeta; Zahn, Dietrich R. T.

    2011-11-01

    Cuprous oxide is a highly interesting material for the emerging field of transparent oxide electronics. In this work the energy dispersion of the dielectric function of Cu2O bulk material is revised by spectroscopic ellipsometry measurements in an extended spectral range from 0.73 to 10 eV. For the first time, the magneto-optical Kerr effect was measured in the spectral range from 1.7 to 5.5 eV and the magneto-optical Voigt constant of Cu2O was obtained by numerical calculations from the magneto-optical Kerr effect spectra and the dielectric function.

  14. Analysis and Measurement of Polarization Conversion in a Periodically Loaded Dielectric Waveguide

    OpenAIRE

    Ando, Takashi; Murata, Toshiyuki; Nakayama, Hiroki; Yamauchi, Junji; Nakano, Hisamatsu

    2002-01-01

    The full-vectorial beam-propagation method with theimproved finite-difference formula is applied to the analysis of aTE/TM mode converter based on an asymmetric periodic loadedwaveguide. The polarization conversion behavior is measured at amicrowave frequency. It is demonstrated that the calculated completeconversion length is in agreement with the experimental result.

  15. High Dielectric and Mechanical Properties Achieved in Cross-Linked PVDF/α-SiC Nanocomposites with Elevated Compatibility and Induced Polarization at the Interface.

    Science.gov (United States)

    Feng, Yefeng; Miao, Bei; Gong, Honghong; Xie, Yunchuan; Wei, Xiaoyong; Zhang, Zhicheng

    2016-07-27

    Remarkably improved dielectric properties including high-k, low loss, and high breakdown strength combined with promising mechanical performance such as high flexibility, good heat, and chemical resistivity are hard to be achieved in high-k dielectric composites based on the current composite fabrication strategy. In this work, a family of high-k polymer nanocomposites has been fabricated from a facile suspension cast process followed by chemical cross-linking at elevated temperature. Internal double bonds bearing poly(vinylidene fluoride-chlorotrifluoroethylene) (P(VDF-CTFE-DB)) in total amorphous phase are employed as cross-linkable polymer matrix. α-SiC particles with a diameter of 500 nm are surface modified with 3-aminpropyltriethoxysilane (KH-550) as fillers for their comparable dielectric performance with PVDF polymer matrix, low conductivity, and high breakdown strength. The interface between SiC particles and PVDF matrix has been finely tailored, which leads to the significantly elevated dielectric constant from 10 to over 120 in SiC particles due to the strong induced polarization. As a result, a remarkably improved dielectric constant (ca. 70) has been observed in c-PVDF/m-SiC composites bearing 36 vol % SiC, which could be perfectly predicted by the effective medium approximation (EMA) model. The optimized interface and enhanced compatibility between two components are also responsible for the depressed conductivity and dielectric loss in the resultant composites. Chemical cross-linking constructed in the composites results in promising mechanical flexibility, good heat and chemical stability, and elevated tensile performance of the composites. Therefore, excellent dielectric and mechanical properties are finely balanced in the PVDF/α-SiC composites. This work might provide a facile and effective strategy to fabricate high-k dielectric composites with promising comprehensive performance. PMID:27377185

  16. Multiwavelength polarization insensitive lenses based on dielectric metasurfaces with meta-molecules

    CERN Document Server

    Arbabi, Ehsan; Kamali, Seyedeh Mahsa; Horie, Yu; Faraon, Andrei

    2016-01-01

    Metasurfaces are nano-structured devices composed of arrays of subwavelength scatterers (or meta-atoms) that manipulate the wavefront, polarization, or intensity of light. Like other diffractive optical devices, metasurfaces suffer from significant chromatic aberrations that limit their bandwidth. Here, we present a method for designing multiwavelength metasurfaces using unit cells with multiple meta-atoms, or meta-molecules. Transmissive lenses with efficiencies as high as 72% and numerical apertures as high as 0.46 simultaneously operating at 915 nm and 1550 nm are demonstrated. With proper scaling, these devices can be used in applications where operation at distinct known wavelengths is required, like various fluorescence microscopy techniques.

  17. Design and simulation of Pt-based microhotplate, and fabrication of suspended dielectric membrane by bulk micromachining

    Science.gov (United States)

    Prasad, Mahanth; Yadav, R. P.; Sahula, V.; Khanna, V. K.

    2012-10-01

    The paper presents the design and simulation of double spiral Pt-based microhotplate (MHP) for gas sensing application. A platinum resistor of 52 Ω has been designed and simulated on a 0.3 micron thick SiO2 suspended membrane of size 40 × 40 μm2 using ANSYS. The SiO2 membrane of size 40 × 40 μμm2 and thickness 0.3 micron has been fabricated successfully by bulk micromachining in TMAH) solution. The simulated temperature and transit time response of microhotplate were obtained as 600.5 °C and 0.2 ms respectively at 4.8 mW power consumption.

  18. Enhanced dielectric properties of electrically poled poly(vinylidene fluoride) (PVDF) and polycarbonate (PC) multilayer films via interfacial polarization

    Science.gov (United States)

    Tseng, Jung-Kai; Mackey, Matthew; Zhou, Zheng; Carr, Joel; Schuele, Donald E.; Baer, Eric; Zhu, Lei

    2014-03-01

    Electrically poled poly(vinylidene fluoride) (PVDF) and polycarbonate (PC) multilayer films can be considered as a polymer electret, which stores quasi-permanent charges (i.e., ions) at PVDF/PC interfaces. In this study, the corresponding dielectric properties of electrically poled PVDF/PC multilayer films are investigated experimentally. First, the bipolar hysteresis loop becomes narrower for the poled PVDF/PC multilayer films upon increasing the poling time, because the impurity ions in PVDF are locked at the PVDF/PC interfaces. Second, asymmetric DC conductivity in poled PVDF/PC multilayer films is observed because of the pre-existing electric field in the electret layers. When the pre-existing field is in the same direction of the applied external field, enhanced DC conductivity is observed in the leakage current measurement. In contrast, if the pre-existing field is opposite to the applied external field, decreased DC conductivity is seen. More experimental evidence of polarized charge at the PVDF/PC interfaces in poled PVDF/PC multilayer films is also manifested by thermally stimulated depolarization current (TSDC) experiments.

  19. Effects of a resistively coated dielectric strip on the TM-polarized resonant backscatter behavior of a slotted conducting rectangular shell

    Science.gov (United States)

    Wu, Lin-Kun; Lu, Cheng-Hung

    1993-06-01

    The performance of a resistively coated dielectric strip used to suppress the first TM-type resonant backscatter associated with a 2D slotted conducting rectangular shell is analyzed in this paper using the moment method technique. Results obtained indicate that almost perfect resonance damping performances are attained when a finite-dimensioned resistively coated dielectric strip with dielectric constant epsilon(r) = 4 - j(0.4) and film resistance R(s) = 188.5 ohms is placed: (1) at the slot (which directly faces the normally incident TM-polarized plane wave), (2) on the interior perimeter of the shell adjacent to the slot, or (3) at the center of the back wall of the shell. Poorer damping performances are observed, however, when the resistively coated dielectric strip is placed at other positions and/or with the same or higher film resistance. Finally, it is also shown that in general the knowledge of the waveguide theory can be used advantageously in the placement of the resistively coated dielectric strip for achieving best resonance damping performance.

  20. Dielectrics in electric fields

    CERN Document Server

    Raju, Gorur G

    2003-01-01

    Discover nontraditional applications of dielectric studies in this exceptionally crafted field reference or text for seniors and graduate students in power engineering tracks. This text contains more than 800 display equations and discusses polarization phenomena in dielectrics, the complex dielectric constant in an alternating electric field, dielectric relaxation and interfacial polarization, the measurement of absorption and desorption currents in time domains, and high field conduction phenomena. Dielectrics in Electric Fields is an interdisciplinary reference and text for professionals and students in electrical and electronics, chemical, biochemical, and environmental engineering; physical, surface, and colloid chemistry; materials science; and chemical physics.

  1. Quasi index matching for minimum reflectance at a dielectric-conductor interface for obliquely incident p- and s-polarized light.

    Science.gov (United States)

    Azzam, R M A; Alsamman, A

    2008-06-10

    Conditions for reducing the reflectance of a dielectric-conductor interface for p- and s-polarized light to a minimum at any angle of incidence phi are determined. The refractive indices of a transparent immersion medium (liquid) that achieve minimum reflectance at normal incidence, phi=0, and at phi=45 degrees are independent of polarization. These indices provide sufficient data to determine the real and imaginary parts of the complex refractive index of an absorbing substrate. Reflection at a dielectric-Au interface at 500 nm wavelength is considered as an example. It is shown that the lowest possible reflectance is attained for p-polarized light at phi=45 degrees and that the associated p-reflection phase shift is also minimum at that angle. For phi> or =65 degrees the lowest reflectance of p-polarized light occurs when the ambient is vacuum or air. However, this lowest reflectance at the air-Au interface is not a true minimum in a mathematical sense. PMID:18545295

  2. Effect of in-material losses on terahertz absorption, transmission, and reflection in photonic crystals made of polar dielectrics

    International Nuclear Information System (INIS)

    The effect of the material absorption factor on terahertz absorption (A), transmittance (T), and reflectance (R) for slabs of PhC that comprise rods made of GaAs, a polar dielectric, is studied. The main goal was to illustrate how critical a choice of the absorption factor for simulations is and to indicate the importance of the possible modification of the absorption ability by using either active or lossy impurities. The spectra of A, T, and R are strongly sensitive to the location of the polaritonic gap with respect to the photonic pass and stop bands connected with periodicity that enables the efficient combination of the effects of material and structural parameters. It will be shown that the spectra can strongly depend on the utilized value of the material absorption factor. In particular, both narrow and wide absorption bands may appear owing to a variation of the material parameters with a frequency in the vicinity of the polaritonic gap. The latter are often achieved at wideband suppression of transmission, so that an ultra-wide stop band can appear as a result of adjustment of the stop bands having different origin. The results obtained at simultaneous variation of the absorption factor and frequency, and angle of incidence and frequency, indicate the possibility of the existence of wide ranges of tolerance, in which the basic features do remain. This allows for mitigating the accuracy requirements for the absorption factor in simulations and promises the efficient absorption of nonmonochromatic waves and beams with a wide angular spectrum. Suppression of narrowband effects in transmission is demonstrated at rather large values of the absorption factor, when they appear due to either the defect modes related to structural defects or dispersion inspired variations of the material parameters in the vicinity of the polaritonic gap. Comparison with auxiliary structures helps one to detect the common features and differences of homogeneous slabs and slabs of a

  3. Effect of in-material losses on terahertz absorption, transmission, and reflection in photonic crystals made of polar dielectrics

    Energy Technology Data Exchange (ETDEWEB)

    Serebryannikov, Andriy E., E-mail: andser@amu.edu.pl [Faculty of Physics, Adam Mickiewicz University, 61-614 Poznań (Poland); Nanotechnology Research Center—NANOTAM, Bilkent University, 06800 Ankara (Turkey); Nojima, S. [Yokohama City University, Department of Nanosystem Science, Graduate School of Nanobioscience, Kanazawa Ku, 22-2 Seto, Yokohama, Kanagawa 2360027 (Japan); Alici, K. B. [TUBITAK Marmara Research Center, Materials Institute, 41470 Gebze, Kocaeli (Turkey); Ozbay, Ekmel [Nanotechnology Research Center—NANOTAM, Bilkent University, 06800 Ankara (Turkey)

    2015-10-07

    The effect of the material absorption factor on terahertz absorption (A), transmittance (T), and reflectance (R) for slabs of PhC that comprise rods made of GaAs, a polar dielectric, is studied. The main goal was to illustrate how critical a choice of the absorption factor for simulations is and to indicate the importance of the possible modification of the absorption ability by using either active or lossy impurities. The spectra of A, T, and R are strongly sensitive to the location of the polaritonic gap with respect to the photonic pass and stop bands connected with periodicity that enables the efficient combination of the effects of material and structural parameters. It will be shown that the spectra can strongly depend on the utilized value of the material absorption factor. In particular, both narrow and wide absorption bands may appear owing to a variation of the material parameters with a frequency in the vicinity of the polaritonic gap. The latter are often achieved at wideband suppression of transmission, so that an ultra-wide stop band can appear as a result of adjustment of the stop bands having different origin. The results obtained at simultaneous variation of the absorption factor and frequency, and angle of incidence and frequency, indicate the possibility of the existence of wide ranges of tolerance, in which the basic features do remain. This allows for mitigating the accuracy requirements for the absorption factor in simulations and promises the efficient absorption of nonmonochromatic waves and beams with a wide angular spectrum. Suppression of narrowband effects in transmission is demonstrated at rather large values of the absorption factor, when they appear due to either the defect modes related to structural defects or dispersion inspired variations of the material parameters in the vicinity of the polaritonic gap. Comparison with auxiliary structures helps one to detect the common features and differences of homogeneous slabs and slabs of a

  4. Effects of interface and bulk properties of gate-dielectric on the performance and stability of hydrogenated amorphous silicon thin-film transistors

    Science.gov (United States)

    Ando, M.; Wakagi, M.; Onisawa, K.

    2015-12-01

    In order to investigate the effects of interface and bulk properties of gate insulator on the threshold voltage (Vth) and the gate-bias induced instability of hydrogenated amorphous silicon thin-film transistors (a-Si:H TFTs), four kinds of TFT structures were fabricated with SiNx and SiOx insulators stacked to make different combinations of the bulk and interface in the gate-dielectric layers. It was found that the Vth and the stability are independently controlled by tuning stoichiometry and thickness of the SiOx insertion layer between a-Si:H and SiNx. In TFTs with SiOx insertion layer of 50 nm thickness, on increasing oxygen/silicon (O/Si = x) ratio from 1.7 to 1.9, Vth increased from 0 V to 9 V. In these TFTs with a relatively thick SiOx insertion layer, positive Vth shift with negative bias stress was observed, confirmed to be due to defect creation in a-Si:H with the thermalization barrier energy of 0.83 eV. On reducing the thickness of the SiOx insertion layer down to approximately 1 nm, thin enough for hole injection through SiOx by tunneling effect, stable operation was obtained while keeping the high Vth value under negative stress bias. These results are consistently explained as follows: (1) the high value for Vth is caused by the dipole generated at the interface between a-Si:H and SiOx; and (2) two causes for Vth shift, charge injection to the gate insulator and defect creation in a-Si:H, are mutually related to each other through the "effective bias stress," Vbseff = Vbs - ΔVfb (Vbs: applied bias stress and ΔVfb: flat band voltage shift due to the charge injection). It was experimentally confirmed that there should be an optimum thickness of SiOx insertion layer of approximately 1 nm with stable high Vth, where enhanced injection increases ΔVfb, reduces Vbseff to reduce defect creation, and totally minimizes Vth shift.

  5. Effects of swift heavy ion irradiation on dielectric relaxation and conduction mechanism in Ba0.90Sr0.10TiO3

    Science.gov (United States)

    Mohan, C. R. K.; Dey, Ranajit; Patel, Shiv P.; Pandey, R. K.; Sharma, M. P.; Bajpai, P. K.

    2016-04-01

    The effects of 100 MeV O8+ ion beam irradiation on the structural and dielectric behavior of Ba0.90Sr0.10TiO3 ceramics have been analyzed. Ion irradiation does not change the crystalline structure, however the tetragonal distortion increases. The low frequency dielectric dispersion especially at high temperatures increases significantly after ion irradiation. The dielectric relaxation phenomenon has been probed through complex impedance and electric modulus approaches. The observed dielectric relaxation has distributed relaxation times and is a thermally activated process. Ion irradiation enhances the cationic disordering. The contributions of grains and grains boundaries towards impedance have been separated. It is inferred that the grain boundaries become more resistive due to ion irradiation and is associated to oxygen vacancies annihilation. Ion irradiation also decreases the bulk ferroelectric polarization demonstrating that the surface or near surface modifications may tune the bulk properties in polar dielectrics.

  6. Dielectric Enhancement from Non-Insulating Particles with Ideally Polarized Interfaces and Zero $\\zeta$-Potential I: Exact Solution

    CERN Document Server

    Qian, Jiang

    2016-01-01

    We solve exactly the dielectric response of a non-insulating sphere of radius $a$ suspended in symmetric, univalent electrolyte solution, with ideally-polarizable interface but without significant $\\zeta$-potential. We then use this solution to derive the dielectric response of a dilute random suspension of such spheres, with volume fraction $f\\ll1$, within the Maxwell-Garnett Effective Medium Approximation. Surprisingly, we discover a huge dielectric enhancement in this bare essential model of dielectric responses of solids in electrolyte solution: at low frequency $\\omega\\tau_D \\ll (\\lambda/a) / (\\sigma_w / \\sigma_s+1/2)$, the real part of the effective dielectric constant of the mixture is $1-(3f/2)+(9f/4)(a/\\lambda)$. Here $\\sigma_{w/s}$ is the conductivity of the electrolyte solution/solids, $\\lambda$ is the Debye screening length in the solution, $\\tau_D=\\lambda^2/D$ is the standard time scale of diffusion and $D$ is the ion diffusion coefficient. As $\\lambda$ is of the order nm even for dilute electrol...

  7. Generalized Brewster effect in dielectric metasurfaces.

    Science.gov (United States)

    Paniagua-Domínguez, Ramón; Yu, Ye Feng; Miroshnichenko, Andrey E; Krivitsky, Leonid A; Fu, Yuan Hsing; Valuckas, Vytautas; Gonzaga, Leonard; Toh, Yeow Teck; Kay, Anthony Yew Seng; Luk'yanchuk, Boris; Kuznetsov, Arseniy I

    2016-01-01

    Polarization is a key property defining the state of light. It was discovered by Brewster, while studying light reflected from materials at different angles. This led to the first polarizers, based on Brewster's effect. Now, one of the trends in photonics is the study of miniaturized devices exhibiting similar, or improved, functionalities compared with bulk optical elements. In this work, it is theoretically predicted that a properly designed all-dielectric metasurface exhibits a generalized Brewster's effect potentially for any angle, wavelength and polarization of choice. The effect is experimentally demonstrated for an array of silicon nanodisks at visible wavelengths. The underlying physics is related to the suppressed scattering at certain angles due to the interference between the electric and magnetic dipole resonances excited in the nanoparticles. These findings open doors for Brewster phenomenon to new applications in photonics, which are not bonded to a specific polarization or angle of incidence. PMID:26783075

  8. Force acting on a dielectric particle in a concentration gradient by ionic concentration polarization under an externally applied DC electric field.

    Science.gov (United States)

    Kang, Kwan Hyoung; Li, Dongqing

    2005-06-15

    There is a concentration-polarization (CP) force acting on a particle submerged in an electrolyte solution with a concentration (conductivity) gradient under an externally applied DC electric field. This force originates from the two mechanisms: (i) gradient of electrohydrodynamic pressure around the particle developed by the Coulombic force acting on induced free charges by the concentration polarization, and (ii) dielectric force due to nonuniform electric field induced by the conductivity gradient. A perturbation analysis is performed for the electric field, the concentration field, and the hydrodynamic field, under the assumptions of creeping flow and small concentration gradient. The leading order component of this force acting on a dielectric spherical particle is obtained by integrating the Maxwell and the hydrodynamic stress tensors. The analytical results are validated by comparing the surface pressure and the skin friction to those of a numerical analysis. The CP force is proportional to square of the applied electric field, effective for electrically neutral particles, and always directs towards the region of higher ionic concentration. The magnitude of the CP force is compared to that of the electrophoretic and the conventional dielectrophoretic forces. PMID:15897097

  9. Significance of the double-layer capacitor effect in polar rubbery dielectrics and exceptionally stable low-voltage high transconductance organic transistors

    Science.gov (United States)

    Wang, Chao; Lee, Wen-Ya; Kong, Desheng; Pfattner, Raphael; Schweicher, Guillaume; Nakajima, Reina; Lu, Chien; Mei, Jianguo; Lee, Tae Hoon; Wu, Hung-Chin; Lopez, Jeffery; Diao, Ying; Gu, Xiaodan; Himmelberger, Scott; Niu, Weijun; Matthews, James R.; He, Mingqian; Salleo, Alberto; Nishi, Yoshio; Bao, Zhenan

    2015-12-01

    Both high gain and transconductance at low operating voltages are essential for practical applications of organic field-effect transistors (OFETs). Here, we describe the significance of the double-layer capacitance effect in polar rubbery dielectrics, even when present in a very low ion concentration and conductivity. We observed that this effect can greatly enhance the OFET transconductance when driven at low voltages. Specifically, when the polar elastomer poly(vinylidene fluoride-co-hexafluoropropylene) (e-PVDF-HFP) was used as the dielectric layer, despite a thickness of several micrometers, we obtained a transconductance per channel width 30 times higher than that measured for the same organic semiconductors fabricated on a semicrystalline PVDF-HFP with a similar thickness. After a series of detailed experimental investigations, we attribute the above observation to the double-layer capacitance effect, even though the ionic conductivity is as low as 10-10 S/cm. Different from previously reported OFETs with double-layer capacitance effects, our devices showed unprecedented high bias-stress stability in air and even in water.

  10. Linearly polarized, Q-switched, erbium-doped fiber laser incorporating a bulk-structured bismuth telluride/polyvinyl alcohol saturable absorber

    Science.gov (United States)

    Lee, Jinho; Lee, Junsu; Koo, Joonhoi; Chung, Hojai; Lee, Ju Han

    2016-07-01

    We experimentally demonstrate a linearly polarized, passively Q-switched, erbium (Er)-doped fiber laser using a saturable absorber (SA) based on a composite consisting of a bulk-structured bismuth telluride (Bi2Te3) topological insulator (TI) and polyvinyl alcohol (PVA). The SA was constructed on a polarization maintaining (PM) fiber ferrule platform, which had a sandwich structure. Its saturation intensity and modulation depth were measured to be ˜ and ˜4.1%, respectively. Using the prepared Bi2Te3/PVA SA in a PM Er-doped fiber ring laser, stable Q-switched pulses with a degree of polarization of ˜98.6% and an azimuth angle of ˜-0.34 deg were demonstrated. The minimum pulse width was measured to be ˜1.58 μs at a repetition rate of 47.1 kHz. This experimental demonstration verifies that a thin film based on a bulk-structured Bi2Te3 TI can fit into a sandwich-structured SA based on PM fiber ferrules.

  11. The critical behavior of the dielectric constant in the polar + polar binary liquid mixture nitromethane + 3-pentanol: an unusual sign of its critical amplitude in the one-phase region.

    Science.gov (United States)

    Leys, Jan; Losada-Pérez, Patricia; Troncoso, Jacobo; Glorieux, Christ; Thoen, Jan

    2011-07-14

    Dielectric constant measurements have been carried out in the one- and two-phase regions near the critical point of the polar + polar binary liquid mixture nitromethane + 3-pentanol. In the two-phase region, evidence for the |t|(2β) singularity in the coexistence-curve diameter has been detected, thus confirming the novel predictions of complete scaling theory for liquid-liquid criticality. In the one-phase region, an "unusual" negative sign for the amplitude of the |t|(1-α) singularity has been encountered for the first time in an upper critical solution temperature type of binary liquid mixture at atmospheric pressure. Mass density measurements have also been carried out to provide additional information related to such experimental finding, which entails an increase of the critical temperature T(c) under an electric field. PMID:21766958

  12. Resonant dielectric metamaterials

    Energy Technology Data Exchange (ETDEWEB)

    Loui, Hung; Carroll, James; Clem, Paul G; Sinclair, Michael B

    2014-12-02

    A resonant dielectric metamaterial comprises a first and a second set of dielectric scattering particles (e.g., spheres) having different permittivities arranged in a cubic array. The array can be an ordered or randomized array of particles. The resonant dielectric metamaterials are low-loss 3D isotropic materials with negative permittivity and permeability. Such isotropic double negative materials offer polarization and direction independent electromagnetic wave propagation.

  13. Lorentz factor determination for local electric fields in semiconductor devices utilizing hyper-thin dielectrics

    International Nuclear Information System (INIS)

    The local electric field (the field that distorts, polarizes, and weakens polar molecular bonds in dielectrics) has been investigated for hyper-thin dielectrics. Hyper-thin dielectrics are currently required for advanced semiconductor devices. In the work presented, it is shown that the common practice of using a Lorentz factor of L = 1/3, to describe the local electric field in a dielectric layer, remains valid for hyper-thin dielectrics. However, at the very edge of device structures, a rise in the macroscopic/Maxwell electric field Ediel occurs and this causes a sharp rise in the effective Lorentz factor Leff. At capacitor and transistor edges, Leff is found to increase to a value 2/3 < Leff < 1. The increase in Leff results in a local electric field, at device edge, that is 50%–100% greater than in the bulk of the dielectric. This increase in local electric field serves to weaken polar bonds thus making them more susceptible to breakage by standard Boltzmann and/or current-driven processes. This has important time-dependent dielectric breakdown (TDDB) implications for all electronic devices utilizing polar materials, including GaN devices that suffer from device-edge TDDB

  14. Lorentz factor determination for local electric fields in semiconductor devices utilizing hyper-thin dielectrics

    Energy Technology Data Exchange (ETDEWEB)

    McPherson, J. W., E-mail: mcpherson.reliability@yahoo.com [McPherson Reliability Consulting LLC, 2805 Shelton Way, Plano, Texas 75093 (United States)

    2015-11-28

    The local electric field (the field that distorts, polarizes, and weakens polar molecular bonds in dielectrics) has been investigated for hyper-thin dielectrics. Hyper-thin dielectrics are currently required for advanced semiconductor devices. In the work presented, it is shown that the common practice of using a Lorentz factor of L = 1/3, to describe the local electric field in a dielectric layer, remains valid for hyper-thin dielectrics. However, at the very edge of device structures, a rise in the macroscopic/Maxwell electric field E{sub diel} occurs and this causes a sharp rise in the effective Lorentz factor L{sub eff}. At capacitor and transistor edges, L{sub eff} is found to increase to a value 2/3 < L{sub eff} < 1. The increase in L{sub eff} results in a local electric field, at device edge, that is 50%–100% greater than in the bulk of the dielectric. This increase in local electric field serves to weaken polar bonds thus making them more susceptible to breakage by standard Boltzmann and/or current-driven processes. This has important time-dependent dielectric breakdown (TDDB) implications for all electronic devices utilizing polar materials, including GaN devices that suffer from device-edge TDDB.

  15. Measurement of wall relaxation times of polarized Helium-3 in bulk liquid Helium-4 for the neutron electric dipole moment experiment

    Science.gov (United States)

    Yoder, Jacob

    The Neutron Electric Dipole Moment (nEDM) experiment that will take place at the Spallation Neutron Source (SNS) in Oak Ridge, Tennessee will measure the electric dipole moment (EDM) of the neutron with a precision of order 10-28 e-cm, utilizing spin-polarized 3He in bulk liquid 4He to detect neutron precession in a 10 mG magnetic field and 50 kV/cm electric field. Since depolarized 3He will produce a background, relaxation of the polarized 3He, characterized by the probability of depolarization per bounce, Pd, was measured for materials that will be in contact with polarized 3He. Depolarization probabilities were determined from measurements of the longitudinal relaxation time of polarized 3He in bulk liquid 4He inside an acrylic cell coated with the wavelength shifter deuterated tetraphenyl butadiene (d-TPB), which will be used to coat the nEDM measurement cell. Relaxation measurements were also performed while rods, made from plumbing material Torlon and valve bellows material BeCu, were present in the cell. The BeCu was coated with Pyralin resin prior to relaxation measurements, while relaxation measurements were performed both before and after the Torlon rod was coated with Pyralin resin. The depolarization probabilities were found to be Pd-TPBd <1.32x10-7 PBareTorlon d=1.01+/-0.08 x10-6 PCoatedTorlon d=2.5+/-0.1 x10-7 PCoatedBeCu d=7.9+/-0.3 x10-7 The relaxation rates extrapolated from the observed values of Pd for d-TPB, coated Torlon, and coated BeCu in the nEDM apparatus were found to be consistent with design goals.

  16. Complex reflection coefficients of p- and s-polarized light at the pseudo-Brewster angle of a dielectric-conductor interface.

    Science.gov (United States)

    Azzam, R M A

    2013-10-01

    The complex Fresnel reflection coefficients r(p) and r(s) of p- and s-polarized light and their ratio ρ=r(p)/r(s) at the pseudo-Brewster angle (PBA) φ(pB) of a dielectric-conductor interface are evaluated for all possible values of the complex relative dielectric function ε=|ε|exp(-jθ)=ε(r)-jε(i), ε(i)>0 that share the same φ(pB). Complex-plane trajectories of r(p), r(s), and ρ at the PBA are presented at discrete values of φ(pB) from 5° to 85° in equal steps of 5° as θ is increased from 0° to 180°. It is shown that for φ(pB)>70° (high-reflectance metals in the IR) r(p) at the PBA is essentially pure negative imaginary and the reflection phase shift δ(p)=arg(r(p))≈-90°. In the domain of fractional optical constants (vacuum UV or light incidence from a high-refractive-index immersion medium) 0<φ(pB)<45° and r(p) is pure real negative (δ(p)=π) when θ=tan(-1)(√(cos(2φ(pB)))), and the corresponding locus of ε in the complex plane is obtained. In the limit of ε(i)=0, ε(r)<0 (interface between a dielectric and plasmonic medium) the total reflection phase shifts δ(p), δ(s), Δ=δ(p)-δ(s)=arg(ρ) are also determined as functions of φ(pB). PMID:24322852

  17. Comparative study on interface and bulk charges in AlGaN/GaN metal-insulator-semiconductor heterostructures with Al2O3, AlN, and Al2O3/AlN laminated dielectrics

    Science.gov (United States)

    Zhu, Jie-Jie; Ma, Xiao-Hua; Chen, Wei-Wei; Hou, Bin; Xie, Yong; Hao, Yue

    2016-05-01

    In this paper, the interface and bulk charges in AlGaN/GaN metal-insulator-semiconductor (MIS) heterostructures with AlN, Al2O3, and Al2O3/AlN laminated dielectrics were studied. In situ plasma pretreatment resulted negligible interface trap states and voltage hysteresis. The fixed charge density at Al2O3/AlN (or Al2O3/barrier) interface was estimated to be 1.66 × 1013 cm-2 by using flat-band voltage shift, and the oxide bulk charge concentration was 2.86 × 1017 cm-3. The interface charge density at other interfaces were at the order of 1011 cm-2. Simulation results using the above charge density/concentration indicated that Al2O3/AlN interface fixed charges dominated the dielectric-related voltage shift in AlGaN/GaN MIS heterostructures, which caused a large voltage shift of -3 V with 10 nm Al2O3 thickness, while the flat-band voltage variety resulting from other types of charges was within 0.1 V.

  18. Chain length effect on dynamical structure of poly(vinyl pyrrolidone)–polar solvent mixtures in dilute solution of dioxane studied by microwave dielectric relaxation measurement

    Indian Academy of Sciences (India)

    R J Sengwa; Sonu Sankhila

    2006-08-01

    Dielectric relaxation study of the binary mixtures of poly(vinyl pyrrolidone) (PVP) (Mw = 24000, 40000 and 360000 g mol-1) with ethyl alcohol (EA) and poly(ethylene glycol)s (PEGs) (Mw = 200 and 400 g mol-1) in dilute solutions of dioxane were carried out at 10.1 GHz and 35°} C. The relaxation time of PVP–EA mixtures was interpreted by the consideration of a wait-and-switch model in the local structure of self-associated ethyl alcohol molecules and also the PVP chain length as a geometric constraint for the reorientational motion of ethyl alcohol molecules. The formation of complexes and effect of PVP chain length on the molecular dynamics, chain flexibility and stretching of PEG molecules in PVP–PEG mixtures were explored from the comparative values of dielectric relaxation time. Further, relaxation time values in dioxane and benzene solvent confirm the viscosity independent molecular dynamics in PVP–EA mixtures but the values vary significantly with the non-polar solvent environment.

  19. Resonance scattering of a dielectric sphere illuminated by electromagnetic Bessel non-diffracting (vortex) beams with arbitrary incidence and selective polarizations

    International Nuclear Information System (INIS)

    A complete description of vector Bessel (vortex) beams in the context of the generalized Lorenz–Mie theory (GLMT) for the electromagnetic (EM) resonance scattering by a dielectric sphere is presented, using the method of separation of variables and the subtraction of a non-resonant background (corresponding to a perfectly conducting sphere of the same size) from the standard Mie scattering coefficients. Unlike the conventional results of standard optical radiation, the resonance scattering of a dielectric sphere in air in the field of EM Bessel beams is examined and demonstrated with particular emphasis on the EM field’s polarization and beam order (or topological charge). Linear, circular, radial, azimuthal polarizations as well as unpolarized Bessel vortex beams are considered. The conditions required for the resonance scattering are analyzed, stemming from the vectorial description of the EM field using the angular spectrum decomposition, the derivation of the beam-shape coefficients (BSCs) using the integral localized approximation (ILA) and Neumann–Graf’s addition theorem, and the determination of the scattering coefficients of the sphere using Debye series. In contrast with the standard scattering theory, the resonance method presented here allows the quantitative description of the scattering using Debye series by separating diffraction effects from the external and internal reflections from the sphere. Furthermore, the analysis is extended to include rainbow formation in Bessel beams and the derivation of a generalized formula for the deviation angle of high-order rainbows. Potential applications for this analysis include Bessel beam-based laser imaging spectroscopy, atom cooling and quantum optics, electromagnetic instrumentation and profilometry, optical tweezers and tractor beams, to name a few emerging areas of research

  20. Resonance scattering of a dielectric sphere illuminated by electromagnetic Bessel non-diffracting (vortex) beams with arbitrary incidence and selective polarizations

    Energy Technology Data Exchange (ETDEWEB)

    Mitri, F.G., E-mail: F.G.Mitri@ieee.org [Chevron, Area 52 Technology–ETC, 5 Bisbee Ct., Santa Fe, NM 87508 (United States); Li, R.X., E-mail: rxli@mail.xidian.edu.cn [School of Physics and Optoelectronic Engineering, Xidian University, Xi’an 710071 (China); Collaborative Innovation Center of Information Sensing and Understanding, Xidian University, Xi’an 710071 (China); Guo, L.X. [School of Physics and Optoelectronic Engineering, Xidian University, Xi’an 710071 (China); Collaborative Innovation Center of Information Sensing and Understanding, Xidian University, Xi’an 710071 (China); Ding, C.Y. [School of Physics and Optoelectronic Engineering, Xidian University, Xi’an 710071 (China)

    2015-10-15

    A complete description of vector Bessel (vortex) beams in the context of the generalized Lorenz–Mie theory (GLMT) for the electromagnetic (EM) resonance scattering by a dielectric sphere is presented, using the method of separation of variables and the subtraction of a non-resonant background (corresponding to a perfectly conducting sphere of the same size) from the standard Mie scattering coefficients. Unlike the conventional results of standard optical radiation, the resonance scattering of a dielectric sphere in air in the field of EM Bessel beams is examined and demonstrated with particular emphasis on the EM field’s polarization and beam order (or topological charge). Linear, circular, radial, azimuthal polarizations as well as unpolarized Bessel vortex beams are considered. The conditions required for the resonance scattering are analyzed, stemming from the vectorial description of the EM field using the angular spectrum decomposition, the derivation of the beam-shape coefficients (BSCs) using the integral localized approximation (ILA) and Neumann–Graf’s addition theorem, and the determination of the scattering coefficients of the sphere using Debye series. In contrast with the standard scattering theory, the resonance method presented here allows the quantitative description of the scattering using Debye series by separating diffraction effects from the external and internal reflections from the sphere. Furthermore, the analysis is extended to include rainbow formation in Bessel beams and the derivation of a generalized formula for the deviation angle of high-order rainbows. Potential applications for this analysis include Bessel beam-based laser imaging spectroscopy, atom cooling and quantum optics, electromagnetic instrumentation and profilometry, optical tweezers and tractor beams, to name a few emerging areas of research.

  1. Dielectric decrement effects in electrokinetics

    Science.gov (United States)

    Figliuzzi, Bruno; Chan, Wai Hong Ronald; Buie, Cullen; Moran, Jeffrey

    2015-11-01

    Understanding the nonlinear phenomena that occur in the electric double layer (EDL) that forms at charged surfaces is a key issue in electrokinetics. In recent studies, Nakayama and Andelman [J. Chem. Physics 2015] Hatlo et al. [EPL 2012], and Zhao and Zhai [JFM 2013] demonstrated that dielectric decrement significantly influences the ionic concentration in the electric double layer (EDL) at high zeta potential, leading to the formation of a condensed layer near the particle's surface. In this presentation, we apply the dielectric decrement model to study two archetypal problems in electrokinetics, namely the electrophoresis of particles with fixed surface charges and the electrophoresis of ideally polarizable particles. Our aim is to rely on numerical simulations to incorporate nonlinear effects including crowding effects due to the finite size of ions, dielectric decrement in the EDL, surface conduction, concentration polarization and advection in the bulk solution. In parallel, we derive a simplified composite layer model that enables us to obtain analytical estimates of the physical quantities involved in the physical description of the problem.

  2. Effect of the external fields on the polar and dielectric properties of Eu0.8Y0.2MnO3

    Science.gov (United States)

    Moreira, J. Agostinho; Almeida, A.; Ferreira, W. S.; Chaves, M. R.; Vilela, S. M. F.; Tavares, P. B.; Kundys, B.; Ranjith, R.; Prellier, W.

    2010-01-01

    Eu0.8Y0.2MnO3 has been widely studied due to its very distinctive phase diagram, where it is still poorly understood the actual ferroelectric character of the low temperature magnetic phases. In order to figure out what is the origin of the microscopic mechanisms that drive its behavior, we carried out a detailed study of the displacement currents for both different starting conditions and polarizing electric fields, and of the field dependent magnetodielectric effect in Eu0.8Y0.2MnO3 ceramics. The experimental results provide clear evidence for the existence of two dipolar systems, one stemming from an electric field-induced process, likely associated with the isovalent substitution of Eu3+ by the smaller off-center Y3+ ions at A-lattice sites, which is independent of any cooperative phenomena occurring in the system. The other dipolar system, strongly dependent on the existence of the first one, drives the polar behavior of the nonmodulated magnetic phase AFM-2, stable in the temperature range of 23-30 K, and is associated with the ferroelectric character of this phase. The magnetic field dependence of the complex dielectric constant clearly shows that the magnetodielectric effect is strongly dependent on the phase it is being considered, and provides further evidence for the ferroelectric character of the AFM-2 phase referred to above.

  3. Studies of linear correlation factor of dielectric polarization and excess dipolar free energies of amides in apolar solvents

    Indian Academy of Sciences (India)

    M Malathi; R Sabesan; S Krishnan

    2005-09-01

    The Kirkwood–Frohlich correlation factor (), Eyring's parameters and * and the dipolar excess free energies of dilute solutions of formamide, acetamide, -methyl acetamide, , -dimethyl formamide and , -dimethyl acetamide in 1,4-dioxan/benzene were obtained from a measurement of their static dielectric permittivities at 308 K. The fluid structure of these amides is discussed. Both in formamide and acetamide a dimeric linear chain with the individual dipoles more or less parallely oriented is preferred. In -methyl acetamide, the antiparallel orientation of dipoles at lower concentrations turns into a parallel orientation with increase of concentration. In tertiary amides, with increase of concentration, parallel orientation of dipoles with global value of tending to unity is observed. The dipolar excess free energy of mixing in a given solvent is of the order primary amide > secondary amide > tertiary amide.

  4. A comparative study of structural, magnetic, dielectric behaviors and impedance spectroscopy for bulk and nanometric double perovskite Sm2CoMnO6

    International Nuclear Information System (INIS)

    A comparative study regarding the structural, magnetic, dielectric and conductivity behavior and impedance spectroscopy of double perovskite Sm2CoMnO6 (SCMO) with different grain sizes of nearly 35 nm (SCMON) and 1 μm (SCMOB) synthesized by a chemical sol-gel route has been performed in detail. The high-resolution recorded XRD pattern confirms the crystalline phase with monoclinic symmetry (space group P21/n) in SCMOB. The XRD pattern of SCMON discloses the coexistence of both monoclinic and orthorhombic (Pnma) phases in the system. The magnetic measurements reveal that, in SCMON, the increase of the disordered phase (orthorhombic phase) results in an increase in the Curie temperature and a decrease in the magnetic moment. SCMOB shows ferromagnetic behavior with two magnetic transitions, whereas the absence of a high-temperature magnetic transition reveals the disorder nature of the SCMON sample. The value of effective paramagnetic moment peff (5.75 μB) of SCMOB is comparable to the calculated value of the spin-only moment for intermediate-spin Co3+ and high-spin Mn3+, as well as high-spin Mn2+ and Co4+, whereas the observed reduced peff (5.5 μB) value is attributed to the spin-only moment due to the increased number of high-spin Mn3+ and low-spin Co3+ in SCMON. SCMOB exhibits a high dielectric constant with prominent high-frequency dielectric dispersion as compared to SCMON. The impedance spectroscopy studies disclose different conduction processes at the grain and grain boundary where the grain boundary obeys Arrhenius behavior and the grains follow the variable range hopping (VRH) model. SCMON shows high grain and grain boundary resistance as compared to SCMOB. The grain and grain boundary capacitance show an anomaly near the dielectric relaxation. The nature of the temperature-dependant exponent s in the ac conductivity predicts that the overlapping large polaron tunneling mechanism (QLPT) is the dominant conduction mechanism for both the SCMOB and SCMON

  5. Maximizing the dielectric response of molecular thin films via quantum chemical design.

    Science.gov (United States)

    Heitzer, Henry M; Marks, Tobin J; Ratner, Mark A

    2014-12-23

    Developing high-capacitance organic gate dielectrics is critical for advances in electronic circuitry based on unconventional semiconductors. While high-dielectric constant molecular substances are known, the mechanism of dielectric response and the fundamental chemical design principles are not well understood. Using a plane-wave density functional theory formalism, we show that it is possible to map the atomic-scale dielectric profiles of molecule-based materials while capturing important bulk characteristics. For molecular films, this approach reveals how basic materials properties such as surface coverage density, molecular tilt angle, and π-system planarity can dramatically influence dielectric response. Additionally, relatively modest molecular backbone and substituent variations can be employed to substantially enhance film dielectric response. For dense surface coverages and proper molecular alignment, conjugated hydrocarbon chains can achieve dielectric constants of >8.0, more than 3 times that of analogous saturated chains, ∼2.5. However, this conjugation-related dielectric enhancement depends on proper molecular orientation and planarization, with enhancements up to 60% for proper molecular alignment with the applied field and an additional 30% for conformations such as coplanarity in extended π-systems. Conjugation length is not the only determinant of dielectric response, and appended polarizable high-Z substituents can increase molecular film response more than 2-fold, affording estimated capacitances of >9.0 μF/cm2. However, in large π-systems, polar substituent effects are substantially attenuated. PMID:25415650

  6. Intrinsic spin polarized electronic structure of CrO{sub 2} epitaxial film revealed by bulk-sensitive spin-resolved photoemission spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Fujiwara, Hirokazu; Sunagawa, Masanori; Kittaka, Tomoko [Research Laboratory for Surface Science and Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530 (Japan); Terashima, Kensei; Wakita, Takanori; Muraoka, Yuji; Yokoya, Takayoshi [Research Laboratory for Surface Science and Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530 (Japan); Research Center of New Functional Materials for Energy Production, Storage, and Transport, Okayama University, Okayama 700-8530 (Japan)

    2015-05-18

    We have performed bulk-sensitive spin-resolved photoemission spectroscopy in order to clarify the intrinsic spin-resolved electronic states of half-metallic ferromagnet CrO{sub 2}. We used CrO{sub 2} epitaxial films on TiO{sub 2}(100), which shows a peak at 1 eV with a clear Fermi edge, consistent with the bulk-sensitive PES spectrum for CrO{sub 2}. In spin-resolved spectra at 40 K, while the Fermi edge was observed in the spin up (majority spin) state, no states at the Fermi level (E{sub F}) with an energy gap of 0.5 eV below E{sub F} were observed in the spin down (minority spin) state. At 300 K, the gap in the spin down state closes. These results are consistent with resistivity measurements and magnetic hysteresis curves of the fabricated CrO{sub 2} film, constituting spectroscopic evidence for the half-metallicity of CrO{sub 2} at low temperature and reducing the spin polarization at room temperature. We also discuss the electron correlation effects of Cr 3d.

  7. Intrinsic spin polarized electronic structure of CrO2 epitaxial film revealed by bulk-sensitive spin-resolved photoemission spectroscopy

    International Nuclear Information System (INIS)

    We have performed bulk-sensitive spin-resolved photoemission spectroscopy in order to clarify the intrinsic spin-resolved electronic states of half-metallic ferromagnet CrO2. We used CrO2 epitaxial films on TiO2(100), which shows a peak at 1 eV with a clear Fermi edge, consistent with the bulk-sensitive PES spectrum for CrO2. In spin-resolved spectra at 40 K, while the Fermi edge was observed in the spin up (majority spin) state, no states at the Fermi level (EF) with an energy gap of 0.5 eV below EF were observed in the spin down (minority spin) state. At 300 K, the gap in the spin down state closes. These results are consistent with resistivity measurements and magnetic hysteresis curves of the fabricated CrO2 film, constituting spectroscopic evidence for the half-metallicity of CrO2 at low temperature and reducing the spin polarization at room temperature. We also discuss the electron correlation effects of Cr 3d

  8. High resolution technique for measuring charge and polarization distributions in dielectrics by piezoelectrically induced pressure step waves (PPS)

    OpenAIRE

    Haardt, Martin; Eisenmenger, Wolfgang

    1982-01-01

    Our step wave technique, so far, has been discussed with respect to the investigation of already prepared samples. In some situations it is of interest to study the buildup of charge and polarization distributions during the poling procedure. This can be accomplished by inserting an additional insulating film, e.g. mylar between the conducting rubber electrode and the sample film. The insulating film acts as a series capacitor reducing the signal amplitude with no influence on the signal shap...

  9. PREFACE: Dielectrics 2009: Measurement Analysis and Applications

    Science.gov (United States)

    Vaughan, Alun; Williams, Graham

    2009-07-01

    The conference Dielectrics 2009: Measurements, Analysis and Applications represents a significant milestone in the evolution of dielectrics research in the UK. It is reasonable to state that the academic study of dielectrics has led to many fundamental advances and that dielectric materials underpin the modern world in devices ranging from field effect transistors, which operate at extremely high fields, albeit low voltages, to the high voltage plants that provide the energy that powers our economy. The origins of the Dielectrics Group of the Institute of Physics (IOP), which organized this conference, can be traced directly back to the early 1960s, when Professor Mansel Davies was conducting research into the dielectric relaxation behaviour of polar liquids and solids at The Edward Davies Chemical Laboratories of the University College of Wales, Aberystwyth. He was already well-known internationally for his studies of molecular structure and bonding of small molecules, using infra-red-spectroscopy, and of the physical properties of hydrogen-bonded liquids and solids, using thermodynamic methods. Dielectric spectroscopy was a fairly new area for him and he realized that opportunities for scientists in the UK to gather together and discuss their research in this developing area of physical chemistry/chemical physics were very limited. He conceived the idea of forming a Dielectrics Discussion Group (DDG), which would act as a meeting point and provide a platform for dielectrics research in the UK and beyond and, as a result, a two-day Meeting was convened in the spring of 1968 at Gregynog Hall of the University of Wales, near Newtown, Montgomeryshire. It was organized by Mansel Davies, Alun Price and Graham Williams, all physical chemists from the UCW, Aberystwyth. Fifty scientists attended, being a mix of physical chemists, theoretical chemists, physicists, electrical engineers, polymer and materials scientists, all from the UK, except Dr Brendan Scaife of Trinity

  10. Dielectric relaxation of ethanol and -methyl acetamide polar mixture in C6H6 at 9.90 GHz

    Indian Academy of Sciences (India)

    S Sahoo; T R Middya; S K Sit

    2014-10-01

    Debye relaxation times $(_{jk})$ and dipole moments $(_{jk})$ of binary ($jk$) polar mixtures of ethanol (EtOH) and -methyl acetamide (NMA) dissolved in benzene(i) are studied by studying conductivity of solution at 9.90 GHz for different temperatures, different mole fractions ($x_j$) of ethanol and different weight fractions $(w_{jk})$ of the mixtures, respectively. The variation of $_{jk}−x_j$ from linear slope of imaginary ($''_{ijk}$) against real ($'_{ijk}$) part of total conductivity ($^{*}_{ijk}$) curve reveals solute–solute (dimer) or solute–solvent (monomer) molecular associations up to $x_j$ = 0.0−0.3 and thereafter, solute–solvent molecular associations. $_{jk}$s from the ratio of slopes of $''_{ijk}$−w_{jk}$ and $'_{ijk}$−w_{jk}$ curves exhibit solute–solvent molecular association for all $x_j$s which are consistent with the $_{jk}−x_j$ curves at all temperatures except at 35°C. This signifies the validity of both the proposed methods in estimating and . The molecular dynamics of the polar mixture are ascertained from Eyring rate theory. Theoretical dipole moments from bond angles and bond moments ($_{\\text{theo}}$) are also calculated to predict associational aspects.

  11. Dielectric behaviour of strontium tartrate single crystals

    Indian Academy of Sciences (India)

    S K Arora; Vipul Patel; Brijesh Amin; Anjana Kothari

    2004-04-01

    Strontium tartrate trihydrate (STT) crystals have been grown in silica hydrogel. Various polarization mechanisms such as atomic polarization of lattice, orientational polarization of dipoles and space charge polarization in the grown crystals have been understood using results of the measurements of dielectric constant (') and dielectric loss (tan ) as functions of frequency and temperature. Ion core type polarization is seen in the temperature range 75–180°C, and above 180°C, there is interfacial polarization for relatively lower frequency range. One observes dielectric dispersion at lower frequency presumably due to domain wall relaxation.

  12. Using Wood to Demonstrate the Dielectric Polarization in the Electrostatic Field%木条演示电介质在静电场中的极化现象

    Institute of Scientific and Technical Information of China (English)

    杨兆刚

    2011-01-01

    介绍了用木条演示电介质在静电场中的极化现象的实验方法,指出了实验时要注意的问题%It introduced the way of using wood to demonstrate the dielectric polarization in the electrostatic field,and pointed out the need to pay attention to for the experiment.

  13. [INVITED] Ultrafast laser photoinscription of large-mode-area waveguiding structures in bulk dielectrics. Invited paper for the section : Hot topics in Ultrafast Lasers

    Science.gov (United States)

    Stoian, R.; D'Amico, C.; Bhuyan, M. K.; Cheng, G.

    2016-06-01

    Ultrafast laser photoinscription and laser-based refractive index engineering develop towards a unique way for three-dimensional optical design inside bulk materials for the conception of embedded photonic applications. The specific optical functions for the light guiding elements, notably their single mode characteristics and the accessible spectral domains, depend on the achieved refractive index contrast in the material transparency window and on the characteristic dimensions of the optical modification. We give here an overview of several laser processing options, developed to increase the effective index area and contrast using pulse engineering methods in space and time, and optical design involving focal shaping, tubular concepts, evanescently coupled waveguide arrays, or structured waveguides.

  14. Oxide or carbide nanoparticles synthesized by laser ablation of a bulk Hf target in liquids and their structural, optical, and dielectric properties

    Science.gov (United States)

    Semaltianos, N. G.; Friedt, J.-M.; Chassagnon, R.; Moutarlier, V.; Blondeau-Patissier, V.; Combe, G.; Assoul, M.; Monteil, G.

    2016-05-01

    Laser ablation of a bulk Hf target in deionized (DI) water, ethanol, or toluene was carried out for the production of nanoparticles' colloidal solutions. Due to the interaction of the ablation plasma plume species with the species which are produced by the liquid decomposition at the plume-liquid interface, hafnia (HfO2) nanoparticles are synthesized in DI water, hafnium carbide (HfC) nanoparticles in toluene, and a mixture of these in ethanol. The hafnia nanoparticles are in the monoclinic low temperature phase and in the tetragonal and fcc high temperature phases. Their size distribution follows log-normal function with a median diameter in the range of 4.3-5.3 nm. Nanoparticles synthesized in DI water have band gaps of 5.6 and 5.4 eV, in ethanol 5.72 and 5.65 eV (using low and high pulse energy), and in toluene 3 eV. The values for the relative permittivity in the range of 7.74-8.90 were measured for hafnia nanoparticles' thin films deposited on substrates by drop-casting (self-assembled layers) in parallel plate capacitor structures.

  15. Dielectric properties of fly ash

    Indian Academy of Sciences (India)

    S C Raghavendra; R L Raibagkar; A B Kulkarni

    2002-02-01

    This paper reports the dielectric properties of fly ash. The dielectric measurements were performed as a function of frequency and temperature. The sample of fly ash shows almost similar behaviour in the frequency and temperature range studied. The large value of dielectric constant in the typical frequency range is because of orientation polarization and tight binding force between the ions or atoms in the fly ash. The sample of fly ash is of great scientific and technological interest because of its high value of dielectric constant (104).

  16. Generalized Brewster-Kerker effect in dielectric metasurfaces

    CERN Document Server

    Paniagua-Dominguez, Ramon; Miroschnichenko, Andrey E; Krivitsky, Leonid A; Fu, Yuan Hsing; Valuckas, Vytautas; Gonzaga, Leonard; Toh, Yeow Teck; Kay, Anthony Yew Seng; Luk'yanchuk, Boris; Kuznetsov, Arseniy I

    2015-01-01

    Polarization is one of the key properties defining the state of light. It was discovered in the early 19th century by Brewster, among others, while studying light reflected from materials at different angles. These studies led to the first polarizers, based on Brewster's effect. One of the most active trends in photonics now is devoted to the study of miniaturized, sub-wavelength devices exhibiting similar, or even improved, functionalities compared to those achieved with bulk optical elements. In the present work, it is theoretically predicted that a properly designed all-dielectric metasurface exhibits a generalized Brewster effect potentially for any angle, wavelength and polarization of choice. The effect is experimentally demonstrated for an array of silicon nanodisks at visible wavelengths. The underlying physics of this effect can be understood in terms of the suppressed scattering at certain angles that results from the interference between the electric and magnetic dipole resonances excited in the na...

  17. Dielectric behaviour of polycarbonate

    Science.gov (United States)

    El-Shabasy, M.; Riad, A. S.

    1996-05-01

    The dielectric constant and the dielectric loss of polycarbonate are investigated in the frequency range 30-10 5 Hz and at temperature from 297 to 365 K. The frequency dependence of the impedance spectra plotted in the complex plane shows semicircles. The system could be represented by an equivalent circuit of a bulk resistance in series with a parallel surface resistance-capacitance combination. The Cole-Cole diagrams have been used to determine the molecular relaxation time τ. The temperature dependence of τ is expressed by a thermally activated process. Analysis of the AC conductivity reveals semiconducting features based predominantly on a hopping mechanism.

  18. Electromagnetic wave speed in polar ice: Validation of the CMP technique with high resolution dielectric-profiling and gamma-density measurements

    OpenAIRE

    Eisen, Olaf; Nixdorf, Uwe; Wilhelms, Frank; Miller, Heinrich

    2002-01-01

    The accuracy of the traveltime-velocity and traveltime-depth profile derived from ground-penetrating radar (GPR) common-midpoint (CMP) surveys at different frequencies is investigated for the first time ever by direct comparison with the profile calculated from high resolution dielectric-profiling (DEP) ice core data.In addition, we compare two traveltime profiles calculated from ice core density data by means of different dielectrical mixture models with the DEP based profile.CMP surveys wer...

  19. Upper bounds on the electrocaloric effect in polar solids

    Science.gov (United States)

    Pirc, R.; Kutnjak, Z.; Blinc, R.; Zhang, Q. M.

    2011-01-01

    Physical upper bounds on the electrocaloric effect (ECE) in bulk polar solids are derived using thermodynamic and statistical mechanics arguments. It is shown that the maximum ECE temperature change ΔT under saturation can be estimated from the dielectric data, such as the saturation polarization and effective Curie constant, as well as from the orientational degeneracy Ω of the elementary dipolar entities in the system and the specific heat of the material. Also obtained is a universal relation for the theoretical maximum value of ΔT, which depends only on Ω and the molar specific heat.

  20. A nanosecond surface dielectric barrier discharge in air at high pressures and different polarities of applied pulses: transition to filamentary mode

    Science.gov (United States)

    Stepanyan, S. A.; Starikovskiy, A. Yu; Popov, N. A.; Starikovskaia, S. M.

    2014-08-01

    The development of a nanosecond surface dielectric barrier discharge in air at pressures 1-6 bar is studied. At atmospheric pressure, the discharge develops as a set of streamers starting synchronously from the high-voltage electrode and propagating along the dielectric layer. Streamers cover the dielectric surface creating a ‘quasi-uniform’ plasma layer. At high pressures and high voltage amplitudes on the cathode, filamentation of the discharge is observed a few nanoseconds after the discharge starts. Parameters of the observed ‘streamers-to-filaments’ transition are measured; physics of transition is discussed on the basis of theoretical estimates and numerical modeling. Ionization-heating instability on the boundary of the cathode layer is suggested as a mechanism of filamentation.

  1. Giant and negative dielectric tunability induced by interfacial polarization in Pb(Fe1/2Nb1/2)1-xTixO3 single crystals

    OpenAIRE

    Liu, Kui; Zhang, Xinyi; Xiao, Jingzhong

    2008-01-01

    The giant and negative dielectric tunability of Pb(Fe1/2Nb1/2)1-xTixO3 single crystals is reported. A low field of 120 V/cm can induce a great reduction of the capacitance, and the tunability is larger than 80% in low frequency range (

  2. Microwave dielectric method for moisture sensing almonds

    Science.gov (United States)

    A dielectric –based method was developed for rapid and nondestructive determination of moisture content in almond kernels independent of bulk density from measurement of their dielectric properties at a single microwave frequency. Calibration equations for moisture determination with temperature com...

  3. Multi-wavelength superlensing with layered phonon-resonant dielectrics.

    Science.gov (United States)

    Li, Peining; Taubner, Thomas

    2012-05-21

    We theoretically propose a multilayered polar-dielectric superlens system capable of sub-diffraction limited imaging simultaneously at different wavelengths. Our theory and simulation results show that this multilayered lens can fulfill a superlensing condition at multiple different wavelengths due to phonon resonances of polar dielectrics, and the number of superlensing wavelengths of the lens can be easily tuned by controlling the number of polar dielectrics. Ideally, by suitably choosing polar dielectrics, our lens can cover wavelengths ranging from infrared to THz frequencies. PMID:22714166

  4. Electrical surface-resistivity, dielectric resonance, polarization and magnetic properties of Bi0.5Sr0.5FeO3-δ thin films grown by pulsed laser deposition

    Science.gov (United States)

    Balamurugan, K.; Ramachandran, B.; Krishna Surendra, M.; Kumar, N. Harish; Ramachandra Rao, M. S.; Santhosh, P. N.

    2014-09-01

    Polycrystalline and highly preferred (1\\,0\\,\\bar{{2}}) orientated Bi0.5Sr0.5FeO3-δ thin films were grown by pulsed laser deposition (PLD) on n-Si (2 0 0) and MgO (2 0 0) single crystalline substrates respectively. The thin films were inspected using x-ray diffraction, scanning electron microscopy, energy dispersive x-ray spectroscopy and atomic force microscopy techniques. The electrical surface-resistivity, dielectric resonance, electric polarization, and magnetic properties of the thin films were studied. At room temperature, depending on deposition conditions, the polycrystalline thin films grown on n-Si substrates were found to exhibit an electrical surface-resistivity of the order of 103-106 Ω, a piezoelectric resonance in the frequency range of about 25-26 MHz, a relaxor-type ferroelectric hysteresis with a maximum polarization of 0.015-0.055 µC cm-2 and magnetic hysteresis. Similarly, the thin films grown on MgO substrates exhibited an electrical surface-resistivity of the order of 109 Ω, multiple piezoelectric resonances in the frequency range of about 8-45 MHz, a linear variation of polarization with applied electric field and either a linearly varying magnetization or magnetic hysteresis which depends on the deposition conditions.

  5. Electrical surface-resistivity, dielectric resonance, polarization and magnetic properties of Bi0.5Sr0.5FeO3−δ thin films grown by pulsed laser deposition

    International Nuclear Information System (INIS)

    Polycrystalline and highly preferred (1 0 2-bar ) orientated Bi0.5Sr0.5FeO3−δ thin films were grown by pulsed laser deposition (PLD) on n-Si (2 0 0) and MgO (2 0 0) single crystalline substrates respectively. The thin films were inspected using x-ray diffraction, scanning electron microscopy, energy dispersive x-ray spectroscopy and atomic force microscopy techniques. The electrical surface-resistivity, dielectric resonance, electric polarization, and magnetic properties of the thin films were studied. At room temperature, depending on deposition conditions, the polycrystalline thin films grown on n-Si substrates were found to exhibit an electrical surface-resistivity of the order of 103–106 Ω, a piezoelectric resonance in the frequency range of about 25–26 MHz, a relaxor-type ferroelectric hysteresis with a maximum polarization of 0.015–0.055 µC cm−2 and magnetic hysteresis. Similarly, the thin films grown on MgO substrates exhibited an electrical surface-resistivity of the order of 109 Ω, multiple piezoelectric resonances in the frequency range of about 8–45 MHz, a linear variation of polarization with applied electric field and either a linearly varying magnetization or magnetic hysteresis which depends on the deposition conditions. (paper)

  6. Giant flexoelectric polarization in a micromachined ferroelectric diaphragm

    KAUST Repository

    Wang, Zhihong

    2012-08-14

    The coupling between dielectric polarization and strain gradient, known as flexoelectricity, becomes significantly large on the micro- and nanoscale. Here, it is shown that giant flexoelectric polarization can reverse remnant ferroelectric polarization in a bent Pb(Zr0.52Ti0.48) O3 (PZT) diaphragm fabricated by micromachining. The polarization induced by the strain gradient and the switching behaviors of the polarization in response to an external electric field are investigated by observing the electromechanical coupling of the diaphragm. The method allows determination of the absolute zero polarization state in a PZT film, which is impossible using other existing methods. Based on the observation of the absolute zero polarization state and the assumption that bending of the diaphragm is the only source of the self-polarization, the upper bound of flexoelectric coefficient of PZT film is calculated to be as large as 2.0 × 10-4 C m -1. The strain gradient induced by bending the diaphragm is measured to be on the order of 102 m-1, three orders of magnitude larger than that obtained in the bulk material. Because of this large strain gradient, the estimated giant flexoelectric polarization in the bent diaphragm is on the same order of magnitude as the normal remnant ferroelectric polarization of PZT film. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Terahertz-frequency dielectric response of liquids

    DEFF Research Database (Denmark)

    Jepsen, Peter Uhd; Møller, Uffe; Cooke, David

    -induced dipole moments. In the polar liquid water the fastest relaxational dynamics is found at terahertz frequencies, just below the first intermolecular vibrational and librational modes. In this presentation we will discuss optical terahertz spectroscopic techniques for measurement of the full dielectric...... function of liquids at terahertz frequencies. We will review the current understanding of the high-frequency dielectric spectrum of water, and discuss the relation between the dielectric spectrum and the thermodynamic properties of certain aqueous solutions....

  8. Correlation effects beyond Hartree-Fock theory and polarization dependence of four-wave mixing in bulk GaAs at high magnetic field

    International Nuclear Information System (INIS)

    Combining linear polarization excitation and magnetic-field breaking of chiral symmetry of optical transitions in Group-III-V semiconductors, we use resonant degenerate four-wave mixing to observe effects beyond the time-dependent Hartree-Fock theory that are not seen by other techniques. (c) 2000 The American Physical Society

  9. Studies of bulk heterojunction solar cells

    Science.gov (United States)

    Cossel, Raquel; McIntyre, Max; Tzolov, Marian

    We are studying bulk heterojunction solar cells that were fabricated using a mixture of PCPDTBT and PCBM­C60. The impedance data of the cells in dark responded like a simple RC circuit. The value of the dielectric constant derived from these results is consistent with the values reported in the literature for these materials. We are showing that the parallel resistance in the equivalent circuit of linear lump elements can be interpreted using the DC current­voltage measurements. The impedance spectra under light illumination indicated the existence of additional polarization. This extra feature can be described by a model that includes a series RC circuit in parallel with the equivalent circuit for a device in dark. The physical interpretation of the additional polarization is based on photo­generated charges getting trapped in wells, which have a characteristic relaxation time corresponding to the observed break frequency in the impedance spectra. We have studied the influence of the anode and cathode interface on this phenomena, either by using different interface materials, or by depositing the metal electrode while the substate is heated.

  10. Penta prism laser polarizer.

    Science.gov (United States)

    Lotem, H; Rabinovitch, K

    1993-04-20

    A novel type of laser prism polarizer is proposed. The polarizer is characterized by a high transmission efficiency, a high optical damage threshold, and a high extinction ratio. The polarizer is shaped like a regular penta prism and, thus, it is a constant deviation angle device. Polarization effects occur upon the two internal cascade reflections in the prism. Anisotropic and Isotropic types of the polarizer are discussed. The isotropic polarizer is a prism made of a high refractive-index glass coated by multilayer polarization-type dielectric coatings. Efficient s-state polarization is obtained because of p-state leakage upon the two internal cascade reflections. The anisotropic polarizer is made of a birefringent crystal in which angular polarization splitting is obtained by the bireflectance (double-reflection) effect. Fanning of a laser beam into up to eight polarized beams is possible in a prism made of a biaxial crystal. PMID:20820335

  11. A Review on Conduction Mechanisms in Dielectric Films

    OpenAIRE

    Fu-Chien Chiu

    2014-01-01

    The conduction mechanisms in dielectric films are crucial to the successful applications of dielectric materials. There are two types of conduction mechanisms in dielectric films, that is, electrode-limited conduction mechanism and bulk-limited conduction mechanism. The electrode-limited conduction mechanism depends on the electrical properties at the electrode-dielectric interface. Based on this type of conduction mechanism, the physical properties of the barrier height at the electrode-diel...

  12. High power, diffraction limited picosecond oscillator based on Nd:GdVO4 bulk crystal with σ polarized in-band pumping.

    Science.gov (United States)

    Lin, Hua; Guo, Jie; Gao, Peng; Yu, Hai; Liang, Xiaoyan

    2016-06-27

    We report on a high power passively mode-locked picosecond oscillator based on Nd:GdVO4 crystal with σ polarized in-band pumping. Thermal gradient and thermal aberration was greatly decreased with proposed configuration. Maximum output power of 37 W at 81 MHz repetition rate with 19.3 ps pulse duration was achieved directly from Nd:GdVO4 oscillator, corresponding to 51% optical efficiency. The oscillator maintained diffraction limited beam quality of M2 pulse duration between 11.2 ps to 19.3 ps. PMID:27410558

  13. All-dielectric metamaterials

    Science.gov (United States)

    Jahani, Saman; Jacob, Zubin

    2016-01-01

    The ideal material for nanophotonic applications will have a large refractive index at optical frequencies, respond to both the electric and magnetic fields of light, support large optical chirality and anisotropy, confine and guide light at the nanoscale, and be able to modify the phase and amplitude of incoming radiation in a fraction of a wavelength. Artificial electromagnetic media, or metamaterials, based on metallic or polar dielectric nanostructures can provide many of these properties by coupling light to free electrons (plasmons) or phonons (phonon polaritons), respectively, but at the inevitable cost of significant energy dissipation and reduced device efficiency. Recently, however, there has been a shift in the approach to nanophotonics. Low-loss electromagnetic responses covering all four quadrants of possible permittivities and permeabilities have been achieved using completely transparent and high-refractive-index dielectric building blocks. Moreover, an emerging class of all-dielectric metamaterials consisting of anisotropic crystals has been shown to support large refractive index contrast between orthogonal polarizations of light. These advances have revived the exciting prospect of integrating exotic electromagnetic effects in practical photonic devices, to achieve, for example, ultrathin and efficient optical elements, and realize the long-standing goal of subdiffraction confinement and guiding of light without metals. In this Review, we present a broad outline of the whole range of electromagnetic effects observed using all-dielectric metamaterials: high-refractive-index nanoresonators, metasurfaces, zero-index metamaterials and anisotropic metamaterials. Finally, we discuss current challenges and future goals for the field at the intersection with quantum, thermal and silicon photonics, as well as biomimetic metasurfaces.

  14. All-dielectric metamaterials.

    Science.gov (United States)

    Jahani, Saman; Jacob, Zubin

    2016-01-01

    The ideal material for nanophotonic applications will have a large refractive index at optical frequencies, respond to both the electric and magnetic fields of light, support large optical chirality and anisotropy, confine and guide light at the nanoscale, and be able to modify the phase and amplitude of incoming radiation in a fraction of a wavelength. Artificial electromagnetic media, or metamaterials, based on metallic or polar dielectric nanostructures can provide many of these properties by coupling light to free electrons (plasmons) or phonons (phonon polaritons), respectively, but at the inevitable cost of significant energy dissipation and reduced device efficiency. Recently, however, there has been a shift in the approach to nanophotonics. Low-loss electromagnetic responses covering all four quadrants of possible permittivities and permeabilities have been achieved using completely transparent and high-refractive-index dielectric building blocks. Moreover, an emerging class of all-dielectric metamaterials consisting of anisotropic crystals has been shown to support large refractive index contrast between orthogonal polarizations of light. These advances have revived the exciting prospect of integrating exotic electromagnetic effects in practical photonic devices, to achieve, for example, ultrathin and efficient optical elements, and realize the long-standing goal of subdiffraction confinement and guiding of light without metals. In this Review, we present a broad outline of the whole range of electromagnetic effects observed using all-dielectric metamaterials: high-refractive-index nanoresonators, metasurfaces, zero-index metamaterials and anisotropic metamaterials. Finally, we discuss current challenges and future goals for the field at the intersection with quantum, thermal and silicon photonics, as well as biomimetic metasurfaces. PMID:26740041

  15. Dielectric lattice gauge theory

    International Nuclear Information System (INIS)

    Dielectric lattice gauge theory models are introduced. They involve variables PHI(b)epsilong that are attached to the links b = (x+esub(μ),x) of the lattice and take their values in the linear space g which consists of real linear combinations of matrices in the gauge group G. The polar decomposition PHI(b)=U(b)osub(μ)(x) specifies an ordinary lattice gauge field U(b) and a kind of dielectric field epsilonsub(ij)proportionalosub(i)osub(j)sup(*)deltasub(ij). A gauge invariant positive semidefinite kinetic term for the PHI-field is found, and it is shown how to incorporate Wilson fermions in a way which preserves Osterwalder Schrader positivity. Theories with G = SU(2) and without matter fields are studied in some detail. It is proved that confinement holds, in the sense that Wilson loop expectation values show an area law decay, if the Euclidean action has certain qualitative features which imply that PHI = 0 (i.e. dielectric field identical 0) is the unique maximum of the action. (orig.)

  16. Circularly-Polarized Microstrip Antenna

    Science.gov (United States)

    Stanton, P. H.

    1985-01-01

    Microstrip construction compact for mobile applications. Circularly polarized microstrip antenna made of concentric cylindrical layers of conductive and dielectric materials. Coaxial cable feedlines connected to horizontal and vertical subelements from inside. Vertical subelement acts as ground for horizontal subelement.

  17. Correlation between structural, electrical and magnetic properties of GdMnO{sub 3} bulk ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Samantaray, S. [Institute of Materials Science, Planetarium Building, Bhubaneswar 751013, Odisha (India); Mishra, D.K. [Department of Physics, Institute of Technical Education and Research, S ‘O’ A University, Bhubaneswar 751030, Odisha (India); Pradhan, S.K. [Institute of Materials Science, Planetarium Building, Bhubaneswar 751013, Odisha (India); Mishra, P.; Sekhar, B.R. [Institue of Physics, Sachivalaya Marg, Bhubaneswar, Odisha (India); Behera, Debdhyan [Advanced Materials Technology Department, CSIR-Institute of Minerals and Materials Technology, Bhubaneswar 751013, Odisha (India); Rout, P.P.; Das, S.K. [Institute of Materials Science, Planetarium Building, Bhubaneswar 751013, Odisha (India); Sahu, D.R. [School of Physics, University of the Witwatersrand, Johannesburg (South Africa); Roul, B.K., E-mail: ims@iopb.res.in [Institute of Materials Science, Planetarium Building, Bhubaneswar 751013, Odisha (India)

    2013-08-15

    This paper reports the effect of sintering temperature on ferroelectric properties of GdMnO{sub 3} (GMO) bulk ceramics at room temperature prepared by the conventional solid state reaction route following slow step sintering schedule. Ferroelectric hysteresis loop as well as sharp dielectric anomaly in pure (99.999%) GMO sintered ceramics has been clearly observed. Samples sintered at 1350 °C become orthorhombic with Pbnm space group and showed frequency independent sharp dielectric anomalies at 373 K and a square type of novel ferroelectric hysteresis loop was observed at room temperature. Interestingly, dielectric anomalies and ferroelectric behavior were observed to be dependent upon sintering temperature of GdMnO{sub 3}. Room temperature dielectric constant (ε{sub r}) value at different frequencies is observed to be abnormally high. The magnetic field and temperature dependent magnetization show antiferromagnetic behavior at 40 K for both 1350 °C and 1700 °C sintered GMO. Present findings showed the possibility of application of GdMnO{sub 3} at room temperature as multifunctional materials. - Highlights: • Preparation of single-phasic polycrystalline GdMnO{sub 3} sample by the solid state sintering route. • Observation of square type P–E hysteresis loop with higher saturation and remnant polarization. • Observation of antiferromagnetic behavior at 40 K in polycrystalline GdMnO{sub 3}. • Possibility of room temperature application of GdMnO{sub 3} as multifunctional material.

  18. Correlation between structural, electrical and magnetic properties of GdMnO3 bulk ceramics

    International Nuclear Information System (INIS)

    This paper reports the effect of sintering temperature on ferroelectric properties of GdMnO3 (GMO) bulk ceramics at room temperature prepared by the conventional solid state reaction route following slow step sintering schedule. Ferroelectric hysteresis loop as well as sharp dielectric anomaly in pure (99.999%) GMO sintered ceramics has been clearly observed. Samples sintered at 1350 °C become orthorhombic with Pbnm space group and showed frequency independent sharp dielectric anomalies at 373 K and a square type of novel ferroelectric hysteresis loop was observed at room temperature. Interestingly, dielectric anomalies and ferroelectric behavior were observed to be dependent upon sintering temperature of GdMnO3. Room temperature dielectric constant (εr) value at different frequencies is observed to be abnormally high. The magnetic field and temperature dependent magnetization show antiferromagnetic behavior at 40 K for both 1350 °C and 1700 °C sintered GMO. Present findings showed the possibility of application of GdMnO3 at room temperature as multifunctional materials. - Highlights: • Preparation of single-phasic polycrystalline GdMnO3 sample by the solid state sintering route. • Observation of square type P–E hysteresis loop with higher saturation and remnant polarization. • Observation of antiferromagnetic behavior at 40 K in polycrystalline GdMnO3. • Possibility of room temperature application of GdMnO3 as multifunctional material

  19. Bulk undercooling

    Science.gov (United States)

    Kattamis, T. Z.

    1984-01-01

    Bulk undercooling methods and procedures will first be reviewed. Measurement of various parameters which are necessary to understand the solidification mechanism during and after recalescence will be discussed. During recalescence of levitated, glass-encased large droplets (5 to 8 mm diam) high speed temperature sensing devices coupled with a rapid response oscilloscope are now being used at MIT to measure local thermal behavior in hypoeutectic and eutectic binary Ni-Sn alloys. Dendrite tip velocities were measured by various investigators using thermal sensors or high speed cinematography. The confirmation of the validity of solidification models of bulk-undercooled melts is made difficult by the fineness of the final microstructure, the ultra-rapid evolution of the solidifying system which makes measurements very awkward, and the continuous modification of the microstructure which formed during recalescence because of precipitation, remelting and rapid coarsening.

  20. Materials Fundamentals of Gate Dielectrics

    CERN Document Server

    Demkov, Alexander A

    2006-01-01

    This book presents materials fundamentals of novel gate dielectrics that are being introduced into semiconductor manufacturing to ensure the continuous scalling of the CMOS devices. This is a very fast evolving field of research so we choose to focus on the basic understanding of the structure, thermodunamics, and electronic properties of these materials that determine their performance in device applications. Most of these materials are transition metal oxides. Ironically, the d-orbitals responsible for the high dielectric constant cause sever integration difficulties thus intrinsically limiting high-k dielectrics. Though new in the electronics industry many of these materials are wel known in the field of ceramics, and we describe this unique connection. The complexity of the structure-property relations in TM oxides makes the use of the state of the art first-principles calculations necessary. Several chapters give a detailed description of the modern theory of polarization, and heterojunction band discont...

  1. First-principles calculation of dielectric response in molecule-based materials.

    Science.gov (United States)

    Heitzer, Henry M; Marks, Tobin J; Ratner, Mark A

    2013-07-01

    The dielectric properties of materials are of fundamental significance to many chemical processes and the functioning of numerous solid-state device technologies. While experimental methods for measuring bulk dielectric constants are well-established, far less is known, either experimentally or theoretically, about the origin of dielectric response at the molecular/multimolecular scale. In this contribution we report the implementation of an accurate first-principles approach to calculating the dielectric response of molecular systems. We assess the accuracy of the method by reproducing the experimental dielectric constants of several bulk π-electron materials and demonstrating the ability of the method to capture dielectric properties as a function of frequency and molecular orientation in representative arrays of substituted aromatic derivatives. The role of molecular alignment and packing density on dielectric response is also examined, showing that the local dielectric behavior of molecular assemblies can diverge significantly from that of the bulk material. PMID:23734640

  2. Aluminum nanoparticle/acrylate copolymer nanocomposites for dielectric elastomers with high dielectric constants

    Science.gov (United States)

    Hu, Wei; Zhang, Suki N.; Niu, Xiaofan; Liu, Chao; Pei, Qibing

    2014-03-01

    Dielectric elastomers are useful for large-strain actuation and energy harvesting. Their application has been limited by their low dielectric constants and consequently high driving voltage. Various fillers with high dielectric constants have been incorporated into different elastomer systems to improve the actuation strain, force output and energy density of the compliant actuators and generators. However, agglomeration may happen in these nanocomposites, resulting in a decrease of dielectric strength, an increase of leakage current, and in many instances the degree of enhancement of the dielectric constant. In this work, we investigated aluminum nanoparticles as nanofillers for acrylate copolymers. This metallic nanoparticle was chosen because the availability of free electrons could potentially provide an infinite value of dielectric constant as opposed to dielectric materials including ferroelectric nanocrystals. Moreover, aluminum nanoparticles have a self-passivated oxide shell effectively preventing the formation of conductive path. The surfaces of the aluminum nanoparticles were functionalized with methacrylate groups to assist the uniform dispersion in organic solutions and additionally enable copolymerization with acrylate copolymer matrix during bulk polymerization, and thus to suppress large range drifting of the nanoparticles. The resulting Al nanoparticle-acrylate copolymer nanocomposites were found to exhibit higher dielectric constant and increased stiffness. The leakage current under high electric fields were significantly lower than nanocomposites synthesized without proper nanoparticle surface modification. The dielectric strengths of the composites were comparable with the pristine polymers. In dielectric actuation evaluation, the actuation force output and energy specific work density were enhanced in the nanocomposites compared to the pristine copolymer.

  3. Molecular density functional theory of water including density-polarization coupling.

    Science.gov (United States)

    Jeanmairet, Guillaume; Levy, Nicolas; Levesque, Maximilien; Borgis, Daniel

    2016-06-22

    We present a three-dimensional molecular density functional theory of water derived from first-principles that relies on the particle's density and multipolar polarization density and includes the density-polarization coupling. This brings two main benefits: (i) scalar density and vectorial multipolar polarization density fields are much more tractable and give more physical insight than the full position and orientation densities, and (ii) it includes the full density-polarization coupling of water, that is known to be non-vanishing but has never been taken into account. Furthermore, the theory requires only the partial charge distribution of a water molecule and three measurable bulk properties, namely the structure factor and the Fourier components of the longitudinal and transverse dielectric susceptibilities. PMID:27116250

  4. Molecular density functional theory of water including density–polarization coupling

    Science.gov (United States)

    Jeanmairet, Guillaume; Levy, Nicolas; Levesque, Maximilien; Borgis, Daniel

    2016-06-01

    We present a three-dimensional molecular density functional theory of water derived from first-principles that relies on the particle’s density and multipolar polarization density and includes the density–polarization coupling. This brings two main benefits: (i) scalar density and vectorial multipolar polarization density fields are much more tractable and give more physical insight than the full position and orientation densities, and (ii) it includes the full density–polarization coupling of water, that is known to be non-vanishing but has never been taken into account. Furthermore, the theory requires only the partial charge distribution of a water molecule and three measurable bulk properties, namely the structure factor and the Fourier components of the longitudinal and transverse dielectric susceptibilities.

  5. Molecular density functional theory of water including density-polarization coupling

    CERN Document Server

    Jeanmairet, Guillaume; Levesque, Maximilien; Borgis, Daniel

    2016-01-01

    We present a three-dimensional molecular density functional theory (MDFT) of water derived from first-principles that relies on the particle's density and multipolar polarization density and includes the density-polarization coupling. This brings two main benefits: ($i$) a scalar density and a vectorial multipolar polarization density fields are much more tractable and give more physical insight than the full position and orientation densities, and ($ii$) it includes the full density-polarization coupling of water, that is known to be non-vanishing but has never been taken into account. Furthermore, the theory requires only the partial charge distribution of a water molecule and three measurable bulk properties, namely the structure factor and the Fourier components of the longitudinal and transverse dielectric susceptibilities.

  6. Dielectric Behavior of Middle Phase Microemulsion

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Dielectric measurements were performed on middle phase microemulsions composed of sodium dodecylsulfate(SDS), cetyltrimethylammonium bromide(CTAB), n-butanol, n-heptane and brine. Distinct and unique dielectric behavior, with characteristic frequency dependence regularity on the salinity of the microemulsions, was observed in the low-frequency range from 10-103Hz. It can be considered to be an interfacial polarization mechanism.

  7. Bulk size crystal growth, spectroscopic, dielectric and surface studies of 4-N,N-dimethylamino-4-N'-methylstilbazolium m-nitrobenzenesulfonate (DSMNS): A potential THz crystal of stilbazolium family.

    Science.gov (United States)

    Antony Raj, A; John Sundaram, S; Gunaseelan, R; Sagayaraj, P

    2015-10-01

    The synthesis and growth of a potentially useful and efficient nonlinear optical organic single crystal of 4-N,N-dimethylamino-4-N'-methylstilbazolium m-nitrobenzenesulfonate (DSMNS) is reported. The growth experiment involved the slope nucleation method coupled with slow cooling as well as slow solvent evaporation techniques. Single crystal X-ray diffraction (XRD), Fourier transform infrared (FT-IR), FT-Raman and nuclear magnetic resonance (NMR) techniques have been employed to ascertain the structure and composition of the crystal. Second harmonic generation (SHG) efficiency of the sample has been examined by Kurtz and Perry powder test. Thermogravimetry (TG), differential thermal analysis (DTA) and differential scanning calorimetry (DSC) techniques are employed to investigate the thermal behavior of the grown crystal. The frequency/temperature dependent dielectric properties of the organic crystal of DSMNS are studied. The surface features of the grown crystal are investigated by chemical etching study and atomic force microscopy (AFM). PMID:26010563

  8. High numerical aperture all-dielectric metasurface micro-lenses

    NARCIS (Netherlands)

    Silvestri, F.; Gerini, G.; Pisano, E.; Galdi, V.

    2015-01-01

    In this paper, the design principles and the sensitivity analysis needed for the realization of a high numerical aperture metasurface micro-lens are presented. The metasurface micro-lens is realized defining a surface with spatially-variant dielectric resonators embedded in a dielectric bulk. The de

  9. Dielectric dispersion of Y-type hexaferrites at low frequencies

    International Nuclear Information System (INIS)

    A series of polycrystalline Y-type hexaferrites with composition Ba2Ni2-xZnxFe12O22 (where 0.0≤x≤2.0) were prepared by the standard ceramic method to study the effect of the frequency, temperature and composition on their AC electrical conductivity σ'AC, and dielectric properties. It was found that, the AC conductivity shows dispersion at high frequencies. This dispersion was attributed to the interfacial polarization arising from the inhomogeneous structure of the material. At low frequencies the dielectric constant, ε', is abnormally high and decreases rapidly with increasing frequency. Dielectric relaxation peaks were observed on the tan δ(F) curves. The results of the dielectric constant and dielectric loss were explained on the basis of the assumption that the mechanism of dielectric polarization is similar to that of the conduction process

  10. Dielectric Actuation of Polymers

    OpenAIRE

    Niu, Xiaofan

    2013-01-01

    Dielectric polymers are widely used in a plurality of applications, such as electrical insulation, dielectric capacitors, and electromechanical actuators. Dielectric polymers with large strain deformations under an electric field are named dielectric elastomers (DE), because of their relative low modulus, high elongation at break, and outstanding resilience. Dielectric elastomer actuators (DEA) are superior to traditional transducers as a muscle-like technology: large strains, high energy den...

  11. Dielectric and phase behavior of dipolar spheroids.

    Science.gov (United States)

    Johnson, Lewis E; Benight, Stephanie J; Barnes, Robin; Robinson, Bruce H

    2015-04-23

    The Stockmayer fluid, composed of dipolar spheres, has a well-known isotropic-ferroelectric phase transition at high dipole densities. However, there has been little investigation of the ferroelectric transition in nearly spherical fluids at dipole densities corresponding to those found in many polar solvents and in guest-host organic electro-optic materials. In this work, we examine the transition to ordered phases of low-aspect-ratio spheroids under both unperturbed and poled conditions, characterizing both the static dielectric response and thermodynamic properties of spheroidal systems. Spontaneous ferroelectric ordering was confined to a small region of aspect ratios about unity, indicating that subtle changes in sterics can have substantial influence on the behavior of coarse-grained liquid models. Our results demonstrate the importance of molecular shape in obtaining even qualitatively correct dielectric responses and provide an explanation for the success of the Onsager model as a phenomenological representation for the dielectric behavior of polar organic liquids. PMID:25821921

  12. Circularly polarized antennas for active holographic imaging through barriers

    Science.gov (United States)

    McMakin, Douglas L [Richland, WA; Severtsen, Ronald H [Richland, WA; Lechelt, Wayne M [West Richland, WA; Prince, James M [Kennewick, WA

    2011-07-26

    Circularly-polarized antennas and their methods of use for active holographic imaging through barriers. The antennas are dielectrically loaded to optimally match the dielectric constant of the barrier through which images are to be produced. The dielectric loading helps to remove barrier-front surface reflections and to couple electromagnetic energy into the barrier.

  13. Nonlinear polariton waves in dielectric medium

    CERN Document Server

    Dzedolik, Igor V

    2012-01-01

    We theoretically investigate the properties of phonon-polariton inhomogeneous harmonic wave, cnoidal wave and spatial soliton propagating in boundless dielectric medium and compute the shape of nonlinear vector polariton wave. We obtain analytically the envelopes of linearly polarized nonlinear polariton waves in the self-focusing and self-defocusing media.

  14. Autonomous dielectric elastomer generator using electret

    Science.gov (United States)

    Vu-Cong, T.; Jean-Mistral, C.; Sylvestre, A.

    2013-04-01

    Dielectric elastomers can work as a variable capacitor to convert mechanical energy such as human motion into electrical energy. Nevertheless, scavengers based on dielectric elastomers require a high voltage source to polarize them, which constitutes the major disadvantage of these transducers. We propose here to combine dielectric elastomer with an electret, providing a quasi-permanent potential, thus replacing the high voltage supply. Our new scavenger is fully autonomous, soft, lightweight and low cost. Our structure is made of a dielectric elastomer (Polypower from Danfoss) and an electret developing a potential of -1000V (Teflon from Dupont). The transducer is designed specifically to scavenge energy from human motion. Thus, it works on pure-shear mode with maximum strain of about 50% and it is textured in 3D form because electret is not deformable. The shape of the hybrid structure is critical to insure huge capacitance variation and thus higher scavenged energy. We present in this paper our process for the optimization of the 3D shape that leads us to the developpment and characterization of our first prototype. From an appropriate electromechanical analytical model, an energy density of about 1.48mJ.g-1 is expected on an optimal electrical load. Our new autonomous dielectric generator can produce about 0.55mJ.g-1 on a resistive load, and can further be improved by enhancing the performance of dielectric elastomer such as dielectric permittivity or by increasing the electret potential.

  15. Complete polarization conversion using one crystal with dual transverse Pockels effect.

    Science.gov (United States)

    Li, Changsheng

    2008-05-01

    Based on dual transverse Pockels effect, complete polarization conversion can be achieved by using only one electro-optic crystal and its two externally applied voltages. The electro-optic phase retardation and the azimuth angle of the field-induced principal dielectric axes of the crystal can be independently and linearly controlled by the amplitude and direction of the applied electric field, and the formulas for this correlation are deduced for arbitrary input and output polarization states. The candidate crystals mainly include the uniaxial crystals of 3 m, 62 m, and 32 symmetry groups, and the cubic crystals of 43 m and 23 symmetry groups. Theoretical analysis demonstrates that one crystal exhibiting both dual transverse Pockels effect and optical activity can also be used for complete polarization converter. The continuous polarization rotation of a linearly polarized light from 0 degrees to 180 degrees has been performed experimentally by use of single lithium niobate crystal with four lateral electrodes. In addition the light beam position-dependent polarization conversion by using a bulk electro-optic crystal is also measured in the experiment. This new type of polarization converter will have potential applications in many fields due to its simple configuration, explicit control logic of polarization conversion, and lower power consumption. PMID:18449288

  16. Electric and magnetic hotspots in dielectric nanowire dimers.

    Science.gov (United States)

    Mirzaei, Ali; Miroshnichenko, Andrey E

    2015-04-14

    We study the formation of the electric and magnetic near-field hotspots in dielectric cylindrical dimers. We compare dielectric and metallic dimers by using experimental data for all materials and consider both TM and TE polarizations of light. We demonstrate that dielectric dimers allow us to simultaneously achieve pure magnetic and electric near-field hotspots for both polarizations in contrast to plasmonic structures. This offers new approaches for near-field engineering such as sensing, control of spontaneous emission, and enhanced Raman scattering. PMID:25773044

  17. Magneto-Optical Activity in High Index Dielectric Nanoantennas

    CERN Document Server

    de Sousa, N; Sáenz, J J; García-Martín, A

    2016-01-01

    The magneto-optical activity, namely the polarization conversion capabilities of high-index, non-absorbing, core-shell dielectric nanospheres is theoretically analyzed. We show that, in analogy with their plasmonic counterparts, the polarization conversion in resonant dielectric particles is linked to the amount of electromagnetic field probing the magneto-optical material in the system. However, in strong contrast with plasmon nanoparticles, due to the peculiar distribution of the internal fields in resonant dielectric spheres, the magneto-optical response is fully governed by the magnetic (dipolar and quadrupolar) resonances with little effect of the electric ones.

  18. Bulk metamaterials: Design, fabrication and characterization

    DEFF Research Database (Denmark)

    Andryieuski, Andrei; Malureanu, Radu; Alabastri, Alessandro;

    2009-01-01

    Bulk metamaterials claim a lot of attention worldwide. We report about our activity and advances in design, fabrication and characterization of metal-dielectric composites with three-dimensional lattices. The nomenclature of designs exhibiting negative index behaviour in the near infrared include......-layers-thick polymer woodpile photonic crystal. Characterization of such samples before and after metal deposition in the 700 nm 1700 nm range exposes some unpredictable features like an enhanced broadband transmission, which still waits to be explained.......Bulk metamaterials claim a lot of attention worldwide. We report about our activity and advances in design, fabrication and characterization of metal-dielectric composites with three-dimensional lattices. The nomenclature of designs exhibiting negative index behaviour in the near infrared includes...

  19. Electromechanical Interplay in Deformable Dielectric Elastomer Networks.

    Science.gov (United States)

    Cohen, Noy; deBotton, Gal

    2016-05-20

    A systematic, statistical-mechanics-based analysis of the response of dielectric elastomers to coupled electromechanical loading is conducted, starting from the monomer level through the polymer chain and ending with closed-form expressions for the polarization and stress fields. It is found that the apparent response at the macrolevel is dictated by four microscopic parameters-the monomer type and polarizability and the chain length and density. Our analysis further reveals a new electrostrictive effect that either reinforces or opposes the polarization-induced deformation. The validity of the results is attested through comparisons with well-established experimental measurements of both the polarization field and the electrostrictive stress. PMID:27258888

  20. Dielectric Laser Acceleration

    OpenAIRE

    England, R. Joel; Noble, Robert J.; Wu, Ziran; Qi, Minghao

    2013-01-01

    We describe recent advances in the study of particle acceleration using dielectric near-field structures driven by infrared lasers, which we refer to as Dielectric Laser Accelerators. Implications for high energy physics and other applications are discussed.

  1. Computing the dielectric constant of liquid water at constant dielectric displacement

    CERN Document Server

    Zhang, Chao

    2015-01-01

    The static dielectric constant of liquid water is computed using classical force field based molecular dynamics simulation at fixed electric displacement D. The method to constrain the electric displacement is the finite temperature classical variant of the constant-D method developed by Stengel, Spaldin and Vanderbilt (Nat. Phys. 2009, 5: 304). There is also a modification of this scheme imposing fixed values of the macroscopic field E. The method is applied to the popular SPC/E model of liquid water. We compare four different estimates of the dielectric constant, two obtained from fluctuations of the polarization at D = 0 and E = 0 and two from the variation of polarization with finite D and E. It is found that all four estimates agree when properly converged. The computational effort to achieve convergence varies however, with constant D calculations being substantially more efficient. We attribute this difference to the much shorter relaxation time of longitudinal polarization compared to transverse polar...

  2. A comparative study of second-harmonic generation in plasmonic and dielectric gratings made of centrosymmetric materials (Presentation Recording)

    Science.gov (United States)

    Weismann, Martin; Gallagher, Dominic F. G.; Panoiu, Nicolae-Coriolan

    2015-09-01

    We present a new numerical method for the analysis of second-harmonic generation (SHG) in one- and two-dimensional (1D, 2D) diffraction gratings containing centrosymmetric quadratically nonlinear materials. Thus, the nonlinear optical properties of a material are determined by its symmetry properties: non-centrosymmetric materials lack inversion symmetry and therefore allow local even-order SHG in the bulk of the material, whereas this process is forbidden in centrosymmetric materials. The inversion symmetry of centrosymmetric materials is broken at their surface whence they allow local surface SHG. Additionally, centrosymmetric materials give rise to nonlocal (bulk) SHG. Our numerical method extends the linear generalized source method (GSM), which is an efficient numerical method for solving the problem of linear diffraction in periodic structures of arbitrary geometry. The nonlinear GSM is a three-step algorithm: for a given excitation at the fundamental frequency the linear field is computed using the linear GSM. This field gives rise to a nonlinear source polarization at the second harmonic (SH) frequency. This nonlinear polarization comprises surface and bulk polarizations as additional source terms and is subsequently used to compute the nonlinear near- and far-field optical response at the SH. We study the convergence characteristics of the nonlinear GSM for 1D and 2D periodic structures and emphasize the numerical intricacies caused by the surface SH polarization term specific to centrosymmetric materials. In order to illustrate the practical significance of our numerical method, we apply it to metallic gratings made of Au and Ag as well as dielectric grating structures made of silicon and investigate the relative contribution of the bulk and surface nonlinearity to the nonlinear optical response at the SH. Particular attention is paid to optical effects that have a competing influence to the nonlinear optical response of the grating structures, namely the

  3. Open dielectric branes

    International Nuclear Information System (INIS)

    We derive leading terms in the effective actions describing the coupling of bulk supergravity fields to systems of arbitrary numbers of Dp-branes and D(p+4)-branes in type-IIA/IIB string theory. We use these actions to investigate the physics of Dp-D(p+4) systems in the presence of weak background fields. In particular, we construct various solutions describing collections of Dp-branes blown up into open D(p+2)-branes ending on D(p+4)-branes. The configurations are stabilized by the presence of background fields and represent an open-brane analogue of the Myers dielectric effect. To deduce the D-brane actions, we use supersymmetry to derive operators corresponding to moments of various conserved currents in the Berkooz-Douglas matrix model of M-theory in the presence of longitudinal M5-branes and then use dualities to relate these operators to the worldvolume operators appearing in the Dp-D(p+4)-brane effective actions. (author)

  4. Tunable dielectric response of transition metals dichalcogenides MX2 (M=Mo, W; X=S, Se, Te): Effect of quantum confinement

    Science.gov (United States)

    Kumar, Ashok; Ahluwalia, P. K.

    2012-12-01

    The first principle calculations have been performed to study the influence of number of layers on the dielectric properties of dichalcogenides of Mo and W for in-plan (E⊥c) as well as out-of-plan polarization (E∥c). We have taken bulk, mono, bi, four and 6-layer setup for this study. The EELS shows significant red shift in the energies of π plasmons, while prominent red shift has been found for the energies of (π+σ) plasmons of all the studied materials by reducing the number of layers from bulk to monolayer limit. The ɛs has been found to red shifted by 62.5% (66.3%), 48.5% (62.1%), 52.7% (66.2%), 61.7% (64.6%), 61.5% (66.7%) and 62.5% (70.5%) from bulk values of MoS2, MoSe2, MoTe2, WS2, WSe2, WTe2 respectively for E⊥c(E∥c) as one goes from bulk to monolayer of these materials. The interband transitions are found to remain independent of the number of layers, however their intensity decreases with decrease in the number of layers. The dielectric functions are highly anisotropic in low energy range and becomes isotropic in high energy range.

  5. Tunable dielectric response of transition metals dichalcogenides MX{sub 2} (M=Mo, W; X=S, Se, Te): Effect of quantum confinement

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Ashok, E-mail: ashok.1777@yahoo.com [Physics Department, Himachal Pradesh University, Shimla, Himachal Pradesh 171005 (India); Ahluwalia, P.K. [Physics Department, Himachal Pradesh University, Shimla, Himachal Pradesh 171005 (India)

    2012-12-15

    The first principle calculations have been performed to study the influence of number of layers on the dielectric properties of dichalcogenides of Mo and W for in-plan (E Up-Tack c) as well as out-of-plan polarization (E Parallel-To c). We have taken bulk, mono, bi, four and 6-layer setup for this study. The EELS shows significant red shift in the energies of {pi} plasmons, while prominent red shift has been found for the energies of ({pi}+{sigma}) plasmons of all the studied materials by reducing the number of layers from bulk to monolayer limit. The {epsilon}{sub s} has been found to red shifted by 62.5% (66.3%), 48.5% (62.1%), 52.7% (66.2%), 61.7% (64.6%), 61.5% (66.7%) and 62.5% (70.5%) from bulk values of MoS{sub 2}, MoSe{sub 2}, MoTe{sub 2}, WS{sub 2}, WSe{sub 2}, WTe{sub 2} respectively for E Up-Tack c(E Parallel-To c) as one goes from bulk to monolayer of these materials. The interband transitions are found to remain independent of the number of layers, however their intensity decreases with decrease in the number of layers. The dielectric functions are highly anisotropic in low energy range and becomes isotropic in high energy range.

  6. Dielectric Properties of Water in Butter and Water-AOT-Heptane Systems Measured using Terahertz Time-Domain Spectroscopy

    DEFF Research Database (Denmark)

    Møller, Uffe; Folkenberg, Jacob Riis; Jepsen, Peter Uhd

    2010-01-01

    We investigate the dielectric properties of water confined in nanometer-sized inverse micelles in mixtures of water, AOT, and heptane. We show that the dielectric properties of the confined water are dependent on the water pool size and different from those of bulk water. We also discuss the...... dielectric properties of different vegetable oils, lard, and butter, and use these properties to deduce the dielectric properties of water in butter, which are shown to deviate significantly from the dielectric properties of bulk water....

  7. Dielectric properties of Jordanian oil shales

    Energy Technology Data Exchange (ETDEWEB)

    Al-Harahsheh, Mohammad; Alnawafleh, Hani [Department of Mining Engineering, College of Mining and Environmental Engineering, Al-Hussein Bin Talal University, Ma' an 20 (Jordan); Kingman, Sam; Saeid, Abdurrahman; Robinson, John; Dimitrakis, Georgios [Process and Environmental Research Division Faculty of Engineering, University of Nottingham, Nottingham, NG7 2RD (United Kingdom)

    2009-10-15

    Microwave heating has been suggested by various authors as a suitable technology for extraction of organic material from oil shales. However, one of the limiting factors in the development of this technology is a lack of accurate dielectric property data for design purposes. In this study the dielectric behaviour of El-lajun oil shale is quantified. The dielectric constant and loss factor of El-lajun oil shale were measured at 2470 and 912 MHz using the cavity perturbation technique. The effects of organic content, temperature, and moisture content on the microwave heating efficiency were quantified. Coaxial probe technique was also employed to study the effect of frequency on dielectric properties of oil shale. Generally, it was found that all samples were of low dielectric loss at room temperature with the imaginary part of permittivity falling significantly after the moisture was removed. This suggests that the major contribution in the dielectric loss is due to the presence of free and/or interlayer water. It was found that both the real and imaginary part of complex permittivity increased with a rise in temperature from 20 up to 80 C, then dropped significantly at about 100 C before staying approximately constant up to a temperature of about 480 C. From this temperature both the real and imaginary parts of complex permittivity increased sharply with further increase in temperature. An attempt was also made to correlate the dielectric properties of the bulk shale sample with the organic content. However, no correlation between dielectric properties and organic matter content was found. (author)

  8. Dispersion analysis with inverse dielectric function modelling.

    Science.gov (United States)

    Mayerhöfer, Thomas G; Ivanovski, Vladimir; Popp, Jürgen

    2016-11-01

    We investigate how dispersion analysis can profit from the use of a Lorentz-type description of the inverse dielectric function. In particular at higher angles of incidence, reflectance spectra using p-polarized light are dominated by bands from modes that have their transition moments perpendicular to the surface. Accordingly, the spectra increasingly resemble inverse dielectric functions. A corresponding description can therefore eliminate the complex dependencies of the dispersion parameters, allow their determination and facilitate a more accurate description of the optical properties of single crystals. PMID:27294550

  9. Systematic effects induced by a flat isotropic dielectric slab

    CERN Document Server

    Macculi, C; Cortiglioni, S; Peverini, O A; Tascone, R; Zannoni, M; Carretti, Ettore; Cortiglioni, Stefano; Macculi, Claudio; Peverini, Oscar Antonio; Tascone, Riccardo; Zannoni, Mario

    2006-01-01

    The instrumental polarization induced by a flat isotropic dielectric slab in microwave frequencies is faced. We find that, in spite of its isotropic nature, such a dielectric can produce spurious polarization either by transmitting incoming anisotropic diffuse radiation or emitting when it is thermally inhomogeneous. We present evaluations of instrumental polarization generated by materials usually adopted in Radioastronomy, by using the Mueller matrix formalism. As an application, results for different slabs in front of a 32 GHz receiver are discussed. Such results are based on measurements of their complex dielectric constant. We evaluate that a 0.33 cm thick Teflon slab introduces negligible spurious polarization ($< 2.6 \\times 10^{-5}$ in transmission and $< 6 \\times 10^{-7}$ in emission), even minimizing the leakage ($< 10^{-8}$ from $Q$ to $U$ Stokes parameters, and viceversa) and the depolarization ($\\sim 1.3 \\times 10^{-3}$).

  10. Coupling of phonon-polariton modes at dielectric-dielectric interfaces by the ATR technique

    Science.gov (United States)

    Cocoletzi, G. H.; Olvera Hernández, J.; Martínez Montes, G.

    1989-08-01

    We report the calculated ATR dispersion relation of the interface phonon-polariton modes in the prism-dielectric-dielectric configuration. Comparison of electromagnetic dispersion relations (EMDR) with the ATR dispersion relations are presented for three different interfaces: I) GaAs/GaP, II) CdF2/CaF2 and III) CaF2/GaP in two propagation windows, using the Otto and Kretschmann geometries for p-polarized light. We have studied the three cases using angle and frequency scans for each window and geometry. The results indicate that it is possible to excite and detect phonon-polariton modes at the dielectric-dielectric interface.

  11. Lattices of dielectric resonators

    CERN Document Server

    Trubin, Alexander

    2016-01-01

    This book provides the analytical theory of complex systems composed of a large number of high-Q dielectric resonators. Spherical and cylindrical dielectric resonators with inferior and also whispering gallery oscillations allocated in various lattices are considered. A new approach to S-matrix parameter calculations based on perturbation theory of Maxwell equations, developed for a number of high-Q dielectric bodies, is introduced. All physical relationships are obtained in analytical form and are suitable for further computations. Essential attention is given to a new unified formalism of the description of scattering processes. The general scattering task for coupled eigen oscillations of the whole system of dielectric resonators is described. The equations for the  expansion coefficients are explained in an applicable way. The temporal Green functions for the dielectric resonator are presented. The scattering process of short pulses in dielectric filter structures, dielectric antennas  and lattices of d...

  12. Dielectric and permeability

    Science.gov (United States)

    Cole, K. D.

    1982-01-01

    Using the unabridged Maxwell equations (including vectors D, E and H) new effects in collisionless plasmas are uncovered. In a steady state, it is found that spatially varying energy density of the electric field (E perpendicular) orthogonal to B produces electric current leading, under certain conditions, to the relationship P perpendicular+B(2)/8 pi-epsilon E perpendicular(2)/8 pi = constant, where epsilon is the dielectric constant of the plasma for fields orthogonal to B. In steady state quasi-two-dimensional flows in plasmas, a general relationship between the components of electric field parallel and perpendicular to B is found. These effects are significant in goephysical and astrophysical plasmas. The general conditions for a steady state in collisionless plasma are deduced. With time variations in a plasma, slow compared to ion-gyroperiod, there is a general current, (j*), which includes the well-known polarisation current, given by J*=d/dt (ExM)+(PxB)xB B(-2) where M and P are the magnetization and polarization vectors respectively.

  13. Atomic-scale microstructures, Raman spectra and dielectric properties of cubic pyrochlore-typed Bi1.5MgNb1.5O7 dielectric ceramics

    KAUST Repository

    Li, Yangyang

    2014-07-01

    Single-phase cubic pyrochlore-typed Bi1.5MgNb 1.5O7 (BMN) dielectric ceramics were synthesized at temperatures of 1050-1200 °C by solid-state reaction method. Their atomic-scale microstructures and dielectric properties were investigated. X-ray diffraction patterns revealed that the BMN ceramics had an average cubic pyrochlore structure, whereas the Raman spectra indicated that they had an essentially cubic symmetry with small local deviations at the A and O\\' sites of the cubic pyrochlore structure. This was confirmed by selected electron area diffraction (SAED) patterns, where the reflections of {442} (not allowed in the cubic pyrochlore with Fd3̄m symmetry) were clearly observed. SEM and TEM images revealed that the average grain size was increased with the sintering temperature, and an un-homogeneous grain growth was observed at high temperatures. HRTEM images and SAED patterns revealed the single-crystalline nature of the BMN ceramic grains. Energy dispersive spectroscopy (EDS) elemental mapping studies indicated that the compositional distributions of Bi, Mg, Nb and O elements in the ceramic grains were homogenous, and no elemental precipitation was observed at the grain boundary. Quantitative EDS data on ceramic grains revealed the expected cationic stoichiometry based on the initial composition of Bi1.5MgNb1.5O7. Dielectric constants of all the BMN samples exhibited almost frequency independent characteristic in the frequency range of 102-106 Hz, and the highest value was 195 for the BMN ceramics sintered at sintered at 1150 °C with the highest bulk density. The dielectric losses were stable and less than 0.002 in the frequency range of 102-105 Hz. The high dielectric constants of the present BMN samples can be ascribed to the local atomic deviations at the A and O\\' sites from the ideal atomic positions of the pyrochlore structure, which affect the different polarization mechanisms in the BMN ceramics, and which in turn enhance the dielectric

  14. A Superlens Based on Metal-Dielectric Composites

    OpenAIRE

    Cai, Wenshan; Genov, Dentcho A.; Shalaev, Vladimir M.

    2005-01-01

    Pure noble metals are typically considered to be the materials of choice for a near-field superlens that allows subwavelength resolution by recovering both propagating and evanescent waves. However, a superlens based on bulk metal can operate only at a single frequency for a given dielectric host. In this Letter, it is shown that a composite metal-dielectric film, with an appropriate metal filling factor, can operate at practically any desired wavelength in the visible and near-infrared range...

  15. Anomalous Dielectric Behavior of Water in Ionic Newton Black Films

    OpenAIRE

    Faraudo, Jordi; Bresme, Fernando

    2004-01-01

    The electrostatics of two charged surfactant layers in aqueous media (surfactant/water/surfactant films) is investigated using molecular dynamics simulations. In the films studied (with a surfactant-surfactant distance from ~35 Å to contact) we observe an anomalous dielectric response of water. The electrostatic potential Φ(z) inside the aqueous core of the films (containing bulk water with ρ = 1 g/cm3) is completely different from that expected for a film containing a dielectric medium wi...

  16. Broadband Dielectric Spectroscopy on Human Blood

    CERN Document Server

    Wolf, M; Lunkenheimer, P; Loidl, A

    2011-01-01

    Dielectric spectra of human blood reveal a rich variety of dynamic processes. Achieving a better characterization and understanding of these processes not only is of academic interest but also of high relevance for medical applications as, e.g., the determination of absorption rates of electromagnetic radiation by the human body. The dielectric properties of human blood are studied using broadband dielectric spectroscopy, systematically investigating the dependence on temperature and hematocrit value. By covering a frequency range from 1 Hz to 40 GHz, information on all the typical dispersion regions of biological matter is obtained. We find no evidence for a low-frequency relaxation (alpha-relaxation) caused, e.g., by counterion diffusion effects as reported for some types of biological matter. The analysis of a strong Maxwell-Wagner relaxation arising from the polarization of the cell membranes in the 1-100 MHz region (beta-relaxation) allows for the test of model predictions and the determination of variou...

  17. Dielectric and specific heat relaxations in vapor deposited glycerol

    Energy Technology Data Exchange (ETDEWEB)

    Kasina, A., E-mail: angeline.kasina@fys.kuleuven.be, E-mail: wubbenhorst@fys.kuleuven.be; Putzeys, T.; Wübbenhorst, M., E-mail: angeline.kasina@fys.kuleuven.be, E-mail: wubbenhorst@fys.kuleuven.be [Department of Physics and Astronomy, Soft Matter and Biophysics Section, KU Leuven, Leuven (Belgium)

    2015-12-28

    Recently [S. Capponi, S. Napolitano, and M. Wübbenhorst, Nat. Commun. 3, 1233 (2012)], vapor deposited glasses of glycerol have been found to recover their super-cooled liquid state via a metastable, ordered liquid (MROL) state characterized by a tremendously enhanced dielectric strength along with a slow-down of the relaxation rate of the structural relaxation. To study the calorimetric signature of this phenomenon, we have implemented a chip-based, differential AC calorimeter in an organic molecular beam deposition setup, which allows the simultaneous measurement of dielectric relaxations via interdigitated comb electrodes and specific heat relaxation spectra during deposition and as function of the temperature. Heating of the as-deposited glass just above the bulk T{sub g} and subsequent cooling/reheating revealed a step-wise increase in c{sub p} by in total 9%, indicating unambiguously that glycerol, through slow vapour deposition, forms a thermodynamically stable glass, which has a specific heat as low as that of crystalline glycerol. Moreover, these glasses were found to show excellent kinetic stability as well as evidenced by both a high onset-temperature and quasi-isothermal recovery measurements at −75 °C. The second goal of the study was to elucidate the impact of the MROL state on the specific heat and its relaxation to the super-cooled state. Conversion of “MROL glycerol” to its “normal” (ordinary liquid, OL) state revealed a second, small (∼2%) increase of the glassy c{sub p}, a little gain (<10%) in the relaxed specific heat, and no signs of deviations of τ{sub cal} from that of normal “bulk” glycerol. These findings altogether suggest that the MROL state in glycerol comprises largely bulk-type glycerol that coexist with a minor volume fraction (<10%) of PVD-induced structural anomalies with a crystal-like calorimetric signature. Based on the new calorimetric findings, we have proposed a new physical picture that assumes the

  18. Computing the Kirkwood g-Factor by Combining Constant Maxwell Electric Field and Electric Displacement Simulations: Application to the Dielectric Constant of Liquid Water.

    Science.gov (United States)

    Zhang, Chao; Hutter, Jürg; Sprik, Michiel

    2016-07-21

    In his classic 1939 paper, Kirkwood linked the macroscopic dielectric constant of polar liquids to the local orientational order as measured by the g-factor (later named after him) and suggested that the corresponding dielectric constant at short-range is effectively equal to the macroscopic value just after "a distance of molecular magnitude" [ Kirkwood, J. Chem. Phys., 1939, 7, 911 ]. Here, we show a simple approach to extract the short-ranged Kirkwood g-factor from molecular dynamics (MD) simulation by superposing the outcomes of constant electric field E and constant electric displacement D simulations [ Zhang and Sprik, Phys. Rev. B: Condens. Matter Mater. Phys., 2016, 93, 144201 ]. Rather than from the notoriously slow fluctuations of the dipole moment of the full MD cell, the dielectric constant can now be estimated from dipole fluctuations at short-range, accelerating the convergence. Exploiting this feature, we computed the bulk dielectric constant of liquid water modeled in the generalized gradient approximation (PBE) to density functional theory and found it to be at least 40% larger than the experimental value. PMID:27352038

  19. Infrared Dielectric Resonator Metamaterial

    CERN Document Server

    Ginn, James C; Peters, David W; Wendt, Joel R; Stevens, Jeffrey O; Hines, Paul F; Basilio, Lorena I; Warne, Larry K; Ihlefeld, Jon F; Clem, Paul G; Sinclair, Michael B

    2011-01-01

    We demonstrate, for the first time, an all-dielectric metamaterial resonator in the mid-wave infrared based on high-index tellurium cubic inclusions. Dielectric resonators are desirable compared to conventional metallo-dielectric metamaterials at optical frequencies as they are largely angular invariant, free of ohmic loss, and easily integrated into three-dimensional volumes. With these low-loss, isotropic elements, disruptive optical metamaterial designs, such as wide-angle lenses and cloaks, can be more easily realized.

  20. Highly tunable elastic dielectric metasurface lenses

    OpenAIRE

    Kamali, Seyedeh Mahsa; Arbabi, Ehsan; Arbabi, Amir; Horie, Yu; Faraon, Andrei

    2016-01-01

    Dielectric metasurfaces are two-dimensional structures composed of nano-scatterers that manipulate phase and polarization of optical waves with subwavelength spatial resolution, enabling ultra-thin components for free-space optics. While high performance devices with various functionalities, including some that are difficult to achieve using conventional optical setups have been shown, most demonstrated components have a fixed functionality. Here we demonstrate highly tunable metasurface devi...

  1. The influence of incompatibility and dielectric contrast on the electric field-induced orientation of lamellar block copolymers

    International Nuclear Information System (INIS)

    We investigate the influence of incompatibility and dielectric contrast on the reorientation kinetics of concentrated solutions of lamellar block copolymers in the presence of an external DC electric field. We study solutions of AC diblock copolymer and ABC triblock terpolymers. The inclusion of a short, polar middle block B is used to tailor both the degree of incompatibility and the dielectric contrast between the two majority phases. In situ synchrotron radiation small-angle X-ray scattering is used to monitor the reorientation process. For the AC diblock copolymer sample only weak electric field induced reorientation could be achieved, following a very slow kinetics, whereas for the ABC triblock terpolymer, reorientation is observed above a threshold value of 0.3 kV/mm. The orientation kinetics is well described by a single exponential with characteristic time constants varying between a few seconds and several minutes depending on the polymer concentration and the electric field strength. We identify a narrow concentration window, in which the interplay between chain mobility and gain in free energy in the electric field allows the preparation of highly anisotropic bulk polymer samples by exposure to an electric field. The results are compared to free energy calculations revealing a distinct difference in the driving force for reorientation as a consequence of an increase in dielectric contrast and chain mobility upon introduction of the B middle block.

  2. Soil water sensor response to bulk electrical conductivity

    Science.gov (United States)

    Soil water monitoring using electromagnetic (EM) sensors can facilitate observations of water content at high temporal and spatial resolutions. These sensors measure soil dielectric permittivity (Ka) which is largely a function of volumetric water content. However, bulk electrical conductivity BEC c...

  3. Nested structures approach for bulk 3D negative index materials

    DEFF Research Database (Denmark)

    Andryieuski, Andrei; Malureanu, Radu; Lavrinenko, Andrei

    2009-01-01

    We propose a generic conceptual idea to obtain bulk 3D negative index metamaterials, which exhibit isotropic properties. The design is based on the nested structures approach, when one element providing magnetic response is inserted into another design with negative dielectric constant. Both...

  4. LOW-FREQUENCY DIELECTRIC RELAXATION IN SILVER STEARATE LAYERS

    Directory of Open Access Journals (Sweden)

    Smirnov, A.P.

    2016-05-01

    Full Text Available The low-frequency dielectric relaxation process in silver stearate layers was studied. The increasing of dielectric permittivity with frequency decreasing and temperature increasing in studied sample are associated with the dipole-relaxation polarization mechanisms. The dispersion of loss factor could be connected with the contribution of relaxation mechanism and conductivity. The shape of the Cole-Cole diagram shows that silver stearate is a non-Debye dielectric material characterized by a wide distribution of relaxators, according to the Cole-Cole relaxation model.

  5. Bulk Moisture and Salinity Sensor

    Science.gov (United States)

    Nurge, Mark; Monje, Oscar; Prenger, Jessica; Catechis, John

    2013-01-01

    Measurement and feedback control of nutrient solutions in plant root zones is critical to the development of healthy plants in both terrestrial and reduced-gravity environments. In addition to the water content, the amount of fertilizer in the nutrient solution is important to plant health. This typically requires a separate set of sensors to accomplish. A combination bulk moisture and salinity sensor has been designed, built, and tested with different nutrient solutions in several substrates. The substrates include glass beads, a clay-like substrate, and a nutrient-enriched substrate with the presence of plant roots. By measuring two key parameters, the sensor is able to monitor both the volumetric water content and salinity of the nutrient solution in bulk media. Many commercially available moisture sensors are point sensors, making localized measurements over a small volume at the point of insertion. Consequently, they are more prone to suffer from interferences with air bubbles, contact area of media, and root growth. This makes it difficult to get an accurate representation of true moisture content and distribution in the bulk media. Additionally, a network of point sensors is required, increasing the cabling, data acquisition, and calibration requirements. measure the dielectric properties of a material in the annular space of the vessel. Because the pore water in the media often has high salinity, a method to measure the media moisture content and salinity simultaneously was devised. Characterization of the frequency response for capacitance and conductance across the electrodes was completed for 2-mm glass bead media, 1- to 2-mm Turface (a clay like media), and 1- to 2-mm fertilized Turface with the presence of root mass. These measurements were then used to find empirical relationships among capacitance (C), the dissipation factor (D), the volumetric water content, and the pore water salinity.

  6. Dielectric analysis of halloysite nanotubes LLDPE nanocomposite compounds

    Science.gov (United States)

    Čermák, M.; Kadlec, P.; Kruliš, Z.; Polanský, R.

    2016-03-01

    The aim of this paper is to investigate the influence of HNT on the dielectric properties of LLDPE (linear low density polyethylene) nanocomposite compounds in the different level of fulfillment (0, 1, 3, 7 wt%). The utilization of these HNT/LLDPE nanocomposite compounds can be seen in the cable industry, where the dielectric properties are essential. Used experimental compounds have been prepared in the laboratory blades mixer Brabender W50 EHT and the plasticorder Brabender PLE 651. Immediately after mixing, the molten compounds were removed from the mixer, inserted into the spacer, and pressed into films of 0.25 mm thickness. Dielectric properties in the DC field (polarization current, reading of polarization index, volume resistivity) of the individual samples were measured and the temperature and frequency range by Broadband dielectric spectroscopy Alpha-A (Novocontrol) were investigated. Samples have been subjected to the dielectric strength test according to standards. As results showed, experimental samples were affected by HNT, especially in the dielectric relaxation phenomena, when during the increment of the level of fulfilment occurred the increasing of the nearly lossless dielectric relaxations. The volume resistivity of the samples was affected in the range of one magnitude.

  7. Manipulation of stored charge in anodic aluminium oxide/SiO2 dielectric stacks by the use of pulsed anodisation

    Science.gov (United States)

    Lu, Zhong; Ouyang, Zi; Grant, Nicholas; Wan, Yimao; Yan, Di; Lennon, Alison

    2016-02-01

    A method of fabricating anodic aluminium oxide (AAO) with the capability of manipulating its stored charge is reported. This method involves the use of a pulsed current source to anodise aluminium layers instead of the typically used constant current/voltage source, with the test structures experiencing positive and negative cycles periodically. By tuning the positive cycle percentage, it is demonstrated that the effective stored charge density can be manipulated in a range from -5.2 × 1011 to 2.5 × 1012 q/cm2 when the AAO is formed over a 12 nm SiO2 layer. An investigation of the stored charge distribution in the dielectric stacks indicates a positive fixed charge at the SiO2/Si interface, a negative fixed charge at the AAO/SiO2 interface and a positive bulk charge within the AAO layer. The effective stored charge density and interface states were found to be affected by annealing conditions and it is suggested that oxygen annealing can reduce the bulk positive charge while post-metallisation anneal is most effective in reducing silicon interface defects. Charge manipulation using pulsed anodisation is shown to reduce carrier recombination on boron-diffused silicon surfaces highlighting the potential of the process to be used to tune the electrical properties of dielectric layers so that they can reduce surface recombination on silicon surfaces having different dopant polarity and concentrations.

  8. Optics of dielectric microstructures

    DEFF Research Database (Denmark)

    Søndergaard, Thomas

    2002-01-01

    From the work carried out within the ph.d. project two topics have been selected for this thesis, namely emission of radiation by sources in dielectric microstructures, and planar photonic crystal waveguides. The work done within the first topic, emission of radiation by sources in dielectric mic...

  9. Terahertz Artificial Dielectric Lens

    Science.gov (United States)

    Mendis, Rajind; Nagai, Masaya; Wang, Yiqiu; Karl, Nicholas; Mittleman, Daniel M.

    2016-03-01

    We have designed, fabricated, and experimentally characterized a lens for the THz regime based on artificial dielectrics. These are man-made media that mimic properties of naturally occurring dielectric media, or even manifest properties that cannot generally occur in nature. For example, the well-known dielectric property, the refractive index, which usually has a value greater than unity, can have a value less than unity in an artificial dielectric. For our lens, the artificial-dielectric medium is made up of a parallel stack of 100 μm thick metal plates that form an array of parallel-plate waveguides. The convergent lens has a plano-concave geometry, in contrast to conventional dielectric lenses. Our results demonstrate that this lens is capable of focusing a 2 cm diameter beam to a spot size of 4 mm, at the design frequency of 0.17 THz. The results further demonstrate that the overall power transmission of the lens can be better than certain conventional dielectric lenses commonly used in the THz regime. Intriguingly, we also observe that under certain conditions, the lens boundary demarcated by the discontinuous plate edges actually resembles a smooth continuous surface. These results highlight the importance of this artificial-dielectric technology for the development of future THz-wave devices.

  10. Surface properties of dielectrics

    International Nuclear Information System (INIS)

    Importance of defects on dielectric behaviour (breakdown), mechanical behaviour (fracture, adhesion) and thermochemical behaviour of insulating materials is recalled. Then effect of a mechanical stress on breakdown voltage is studied. An experimental verification shows that fracture of Y2O3 is propagated in grain boundaries enriched in oxygen vacancies for a non stoichiometric sample by local variation of dielectric constant

  11. Fluctuation-Induced Interaction between Randomly Charged Dielectrics

    OpenAIRE

    Naji, Ali; Dean, David S.; Sarabadani, Jalal; Horgan, Ron R.; Podgornik, Rudolf

    2009-01-01

    Monopolar charge disorder effects are studied in the context of fluctuation-induced interactions between neutral dielectric slabs. It is shown that quenched bulk charge disorder gives rise to an additive contribution to the net interaction force which decays as the inverse distance between the slabs and may thus completely mask the standard Casimir--van der Waals force at large separations. By contrast, annealed (bulk or surface) charge disorder leads to a net interaction force whose large-di...

  12. Dielectric strength of parylene HT

    International Nuclear Information System (INIS)

    The dielectric strength of parylene HT (PA-HT) films was studied at room temperature in a wide thickness range from 500 nm to 50 μm and was correlated with nano- and microstructure analyses. X-ray diffraction and polarized optical microscopy have revealed an enhancement of crystallization and spherulites development, respectively, with increasing the material thickness (d). Moreover, a critical thickness dC (between 5 and 10 μm) is identified corresponding to the beginning of spherulite developments in the films. Two distinct behaviors of the dielectric strength (FB) appear in the thickness range. For d ≥ dC, PA-HT films exhibit a decrease in the breakdown field following a negative slope (FB ∼ d−0.4), while for d C, it increases with increasing the thickness (FB ∼ d0.3). An optimal thickness doptim ∼ 5 μm corresponding to a maximum dielectric strength (FB ∼ 10 MV/cm) is obtained. A model of spherulite development in PA-HT films with increasing the thickness is proposed. The decrease in FB above dC is explained by the spherulites development, whereas its increase below dC is induced by the crystallites growth. An annealing of the material shows both an enhancement of FB and an increase of the crystallites and spherulites dimensions, whatever the thickness. The breakdown field becomes thickness-independent below dC showing a strong influence of the nano-scale structural parameters. On the contrary, both nano- and micro-scale structural parameters appear as influent on FB for d ≥ dC

  13. Dielectric strength of parylene HT

    Energy Technology Data Exchange (ETDEWEB)

    Diaham, S., E-mail: sombel.diaham@laplace.univ-tlse.fr; Bechara, M.; Locatelli, M.-L.; Khazaka, R. [Université de Toulouse, UPS, INPT, LAPLACE, 118 route de Narbonne-Bât. 3R3, F-31062 Toulouse Cedex 9 (France); CNRS, LAPLACE, F-31062 Toulouse (France); Tenailleau, C. [Université de Toulouse, UPS, Laboratoire CIRIMAT/LCMIE, 118 route de Narbonne-Bât. 2R1, F-31062 Toulouse Cedex 9 (France); Kumar, R. [Speciality Coating Systems, Inc. (SCS), Cookson Electronics, 7645 Woodland Drive, Indianapolis, Indiana 46278 (United States)

    2014-02-07

    The dielectric strength of parylene HT (PA-HT) films was studied at room temperature in a wide thickness range from 500 nm to 50 μm and was correlated with nano- and microstructure analyses. X-ray diffraction and polarized optical microscopy have revealed an enhancement of crystallization and spherulites development, respectively, with increasing the material thickness (d). Moreover, a critical thickness d{sub C} (between 5 and 10 μm) is identified corresponding to the beginning of spherulite developments in the films. Two distinct behaviors of the dielectric strength (F{sub B}) appear in the thickness range. For d ≥ d{sub C}, PA-HT films exhibit a decrease in the breakdown field following a negative slope (F{sub B} ∼ d{sup −0.4}), while for d < d{sub C}, it increases with increasing the thickness (F{sub B} ∼ d{sup 0.3}). An optimal thickness d{sub optim} ∼ 5 μm corresponding to a maximum dielectric strength (F{sub B} ∼ 10 MV/cm) is obtained. A model of spherulite development in PA-HT films with increasing the thickness is proposed. The decrease in F{sub B} above d{sub C} is explained by the spherulites development, whereas its increase below d{sub C} is induced by the crystallites growth. An annealing of the material shows both an enhancement of F{sub B} and an increase of the crystallites and spherulites dimensions, whatever the thickness. The breakdown field becomes thickness-independent below d{sub C} showing a strong influence of the nano-scale structural parameters. On the contrary, both nano- and micro-scale structural parameters appear as influent on F{sub B} for d ≥ d{sub C}.

  14. Tunable Liquid Dielectric Antenna

    Directory of Open Access Journals (Sweden)

    Kamal Raj Singh Rajoriya

    2012-06-01

    Full Text Available This paper presents on modified the dielectric properties of liquid with varying salinity that was based on monopole structure. Dielectric resonator antennas (DRAs can be made with a wide range of materials and allow many excitation methods [2]. Pure water does not work at high frequency (> 1 GHz but increase in the salinity of water modifies the dielectric properties of water. Here proposed antenna shows that when the salinity increases in form of molar solution, the antenna was tuned at different frequency with increases return loss.

  15. Research on the Circularly Polarized Radial Line Slot Antenna with Low Dielectric Constant%低相对介电常数的圆极化径向缝隙天线的研究

    Institute of Scientific and Technical Information of China (English)

    王宜颖; 肖怀宝; 逯贵祯; 吕英华; 林金才; 郭永坤

    2014-01-01

    径向缝隙天线是高增益、高效率的平面缝隙阵列天线。天线缝隙阵列按一定的规律排布在径向波导的上表面,径向波导内部填充由慢波材料来抑制天线的栅瓣,其中慢波材料的相对介电常数一般的选择范围是1.5~2.5。本文设计的径向缝隙天线中填充径向波导的慢波材料的相对介电常数为1.06。依据径向缝隙天线的设计原则,适当调整缝隙的排布,所设计天线并未出现栅瓣,并且有较好的方向性。天线的仿真结果与测量结果吻合的较好。%The Radial Line Slot Antenna (RLSA) is a planar slotted array antenna, which possesses high gain and high efficiency. The slot pairs are arranged on the top of the radial line waveguide, the waveguide filled with the slow wave material to suppress the grating lobes, generally, the relative dielectric constant is between 1.5 and 2.5. However, this paper presents an antenna that the relative dielectric constant is 1.06. Adjusting the length of the slots, the grating lobes are not appeared, and the direction is very well. And the simulation results are consistent well with the measurement results.

  16. Cast dielectric composite linear accelerator

    Science.gov (United States)

    Sanders, David M.; Sampayan, Stephen; Slenes, Kirk; Stoller, H. M.

    2009-11-10

    A linear accelerator having cast dielectric composite layers integrally formed with conductor electrodes in a solventless fabrication process, with the cast dielectric composite preferably having a nanoparticle filler in an organic polymer such as a thermosetting resin. By incorporating this cast dielectric composite the dielectric constant of critical insulating layers of the transmission lines of the accelerator are increased while simultaneously maintaining high dielectric strengths for the accelerator.

  17. Dielectric materials for electrical engineering

    CERN Document Server

    Martinez-Vega, Juan

    2013-01-01

    Part 1 is particularly concerned with physical properties, electrical ageing and modeling with topics such as the physics of charged dielectric materials, conduction mechanisms, dielectric relaxation, space charge, electric ageing and life end models and dielectric experimental characterization. Part 2 concerns some applications specific to dielectric materials: insulating oils for transformers, electrorheological fluids, electrolytic capacitors, ionic membranes, photovoltaic conversion, dielectric thermal control coatings for geostationary satellites, plastics recycling and piezoelectric poly

  18. Short range ferromagnetic, magneto-electric, and magneto-dielectric effect in ceramic Co3TeO6

    International Nuclear Information System (INIS)

    We report observation of magneto-electric and magneto-dielectric couplings along with short range ferromagnetic order in ceramic Cobalt Tellurate (Co3TeO6, CTO) using magnetic, structural, dielectric, pyroelectric, and polarization studies. DC magnetization along with dielectric constant measurements indicate a coupling between magnetic order and electrical polarization. A strong anomaly in the dielectric constant at ∼17.4 K in zero magnetic field indicates spontaneous electric polarization, consistent with a recent neutron diffraction study. Observation of weak short range ferromagnetic order at lower temperatures is attributed to the Griffiths-like ferromagnetism. Furthermore, magnetic field dependence of the ferroelectric transition follows earlier theoretical predictions, applicable to single crystal CTO. Finally, combined dielectric, pyroelectric, and polarization measurements suggest that the ground state of CTO may possess spontaneous symmetry breaking in the absence of magnetic field

  19. Transformation Algorithm of Dielectric Response in Time-Frequency Domain

    Directory of Open Access Journals (Sweden)

    Ji Liu

    2014-01-01

    Full Text Available A transformation algorithm of dielectric response from time domain to frequency domain is presented. In order to shorten measuring time of low or ultralow frequency dielectric response characteristics, the transformation algorithm is used in this paper to transform the time domain relaxation current to frequency domain current for calculating the low frequency dielectric dissipation factor. In addition, it is shown from comparing the calculation results with actual test data that there is a coincidence for both results over a wide range of low frequencies. Meanwhile, the time domain test data of depolarization currents in dry and moist pressboards are converted into frequency domain results on the basis of the transformation. The frequency domain curves of complex capacitance and dielectric dissipation factor at the low frequency range are obtained. Test results of polarization and depolarization current (PDC in pressboards are also given at the different voltage and polarization time. It is demonstrated from the experimental results that polarization and depolarization current are affected significantly by moisture contents of the test pressboards, and the transformation algorithm is effective in ultralow frequency of 10−3 Hz. Data analysis and interpretation of the test results conclude that analysis of time-frequency domain dielectric response can be used for assessing insulation system in power transformer.

  20. Circularly polarized antennas

    CERN Document Server

    Gao, Steven; Zhu, Fuguo

    2013-01-01

    This book presents a comprehensive insight into the design techniques for different types of CP antenna elements and arrays In this book, the authors address a broad range of topics on circularly polarized (CP) antennas. Firstly, it introduces to the reader basic principles, design techniques and characteristics of various types of CP antennas, such as CP patch antennas, CP helix antennas, quadrifilar helix antennas (QHA), printed quadrifilar helix antennas (PQHA), spiral antenna, CP slot antennas, CP dielectric resonator antennas, loop antennas, crossed dipoles, monopoles and CP horns. Adva

  1. Generating stable tractor beams with dielectric metasurfaces

    Science.gov (United States)

    Pfeiffer, Carl; Grbic, Anthony

    2015-03-01

    Propagation-invariant beams that pull objects towards a light source are commonly known as tractor beams. Here, an efficient, linearly polarized tractor beam with improved stability is introduced. The beam consists of a superposition of transverse-electric and transverse-magnetic polarized Bessel beams of orders m =+1 and m =-1 . It is shown that this beam can stably pull a wide range of dielectric microparticles arbitrarily long distances, independent of ambient conditions. Next, a straightforward method of generating these high-performance beams is proposed. A Si metasurface transforms an incident linearly polarized Gaussian beam into the desired tractor beam. Full-wave simulations demonstrate that it is possible for this simple geometry to pull a polystyrene sphere a distance equal to the nondiffracting range of the Bessel beam. The simplicity of the setup and the robust performance of the proposed tractor beam significantly enhance the ability to manipulate matter with light.

  2. A spherical cavity model for quadrupolar dielectrics.

    Science.gov (United States)

    Dimitrova, Iglika M; Slavchov, Radomir I; Ivanov, Tzanko; Mosbach, Sebastian

    2016-03-21

    The dielectric properties of a fluid composed of molecules possessing both dipole and quadrupole moments are studied based on a model of the Onsager type (molecule in the centre of a spherical cavity). The dielectric permittivity ε and the macroscopic quadrupole polarizability αQ of the fluid are related to the basic molecular characteristics (molecular dipole, polarizability, quadrupole, quadrupolarizability). The effect of αQ is to increase the reaction field, to bring forth reaction field gradient, to decrease the cavity field, and to bring forth cavity field gradient. The effects from the quadrupole terms are significant in the case of small cavity size in a non-polar liquid. The quadrupoles in the medium are shown to have a small but measurable effect on the dielectric permittivity of several liquids (Ar, Kr, Xe, CH4, N2, CO2, CS2, C6H6, H2O, CH3OH). The theory is used to calculate the macroscopic quadrupolarizabilities of these fluids as functions of pressure and temperature. The cavity radii are also determined for these liquids, and it is shown that they are functions of density only. This extension of Onsager's theory will be important for non-polar solutions (fuel, crude oil, liquid CO2), especially at increased pressures. PMID:27004882

  3. Noncontact Dielectric Friction

    OpenAIRE

    Kuehn, Seppe; Marohn, John A.; Loring, Roger F.

    2006-01-01

    Dielectric fluctuations are shown to be the dominant source of noncontact friction in high-sensitivity scanning probe microscopy of dielectric materials. Recent measurements have directly determined the friction acting on custom-fabricated single-crystal silicon cantilevers whose capacitively charged tips are located 3–200 nm above thin films of poly(methyl methacrylate), poly(vinyl acetate), and polystyrene. Differences in measured friction among these polymers are explained here by relating...

  4. Pattern formation in dielectric barrier discharges with different dielectric materials

    International Nuclear Information System (INIS)

    The influence of dielectric material on the bifurcation and spatiotemporal dynamics of the patterns in dielectric barrier discharge in argon/air at atmospheric pressure is studied. It is found that pattern bifurcation sequences are different with different dielectric materials. The spatiotemporal dynamics of the hexagonal pattern in dielectric barrier discharge depends on the dielectric material. The hexagon pattern with glass dielectric is an interleaving of two rectangular sublattices appearing at different moments. The hexagon pattern with quartz dielectric is composed of one set of hexagonal lattice discharging twice in one half cycle of the applied voltage, one is at the rising edge and the other at the falling edge. It results in that the accumulation of wall charges in individual microdischarges in a hexagon pattern with quartz dielectric is greater than that with glass dielectric, which is in agreement with the electron density measurement by Stark broadening of Ar I 696.54 nm.

  5. Temperature dependence of the dielectric constant of acrylic dielectric elastomer

    Energy Technology Data Exchange (ETDEWEB)

    Sheng, Junjie; Chen, Hualing; Li, Bo; Chang, Longfei [Xi' an Jiaotong University, State Key Laboratory for Strength and Vibration of Mechanical Structures, Xi' an (China); Xi' an Jiaotong University, School of Mechanical Engineering, Xi' an (China)

    2013-02-15

    The dielectric constant is an essential electrical parameter to the achievable voltage-induced deformation of the dielectric elastomer. This paper primarily focuses on the temperature dependence of the dielectric constant (within the range of 173 K to 373 K) for the most widely used acrylic dielectric elastomer (VHB 4910). First the dielectric constant was investigated experimentally with the broadband dielectric spectrometer (BDS). Results showed that the dielectric constant first increased with temperature up to a peak value and then dropped to a relative small value. Then by analyzing the fitted curves, the Cole-Cole dispersion equation was found better to characterize the rising process before the peak values than the Debye dispersion equation, while the decrease process afterward can be well described by the simple Debye model. Finally, a mathematical model of dielectric constant of VHB 4910 was obtained from the fitted results which can be used to further probe the electromechanical stability of the dielectric elastomers. (orig.)

  6. Anisotropic dielectric substrate as thin dielectric resonator

    Czech Academy of Sciences Publication Activity Database

    Bovtun, Viktor; Pashkov, V.; Kempa, Martin; Molchanov, V.; Kamba, Stanislav; Poplavko, Y.; Yakymenko, Y.

    Sevastopol: Weber Publishing, 2012 - (Yermolov, P.), s. 573-574 ISBN 978-966-335-370-8. [International Conference Microwave & Telecommunication Technology /22./. Sevastopol (UA), 10.09.2012-14.09.2012] R&D Projects: GA ČR GAP204/12/1163 Institutional research plan: CEZ:AV0Z10100520 Keywords : dielectric resonator * substrate * microwave Subject RIV: BM - Solid Matter Physics ; Magnetism http://www.crimico.org/en/

  7. Size effect on dielectric properties of synthetic diamond

    Science.gov (United States)

    Batsanov, Stepan S.; Dan’kin, Dmitry A.

    2016-07-01

    Reducing sizes of diamond crystals in the micrometer range progressively increases their dielectric permittivity. This effect is due to the surface shells of solids where under-coordinated atoms diminish the energy of chemical bonding on a surface that reduces the frequency of atomic vibration but also create a distortion in atomic order causing spontaneous polarization.

  8. Scattering of Slow Metastable Argon Atoms by Dielectric Nanospheres

    Science.gov (United States)

    Baudon, J.; Hamamda, M.; Grucker, J.; Perales, F.; Dutier, G.; Ducloy, M.; Bocvarski, V.

    2009-11-01

    The elastic scattering at low energy of metastable argon atoms with internal angular momentum J = 0 and 2 by dielectric nanospheres is investigated. The differential cross sections are calculated for both isotropic and anisotropic interactions. A polarization effect is clearly evidenced. The possible use of a metastable atom beam as a probe of an ensemble of nanospheres deposited on a passive substrate is examined.

  9. Dielectric resonances in disordered media

    Science.gov (United States)

    Raymond, L.; Laugier, J.-M.; Schäfer, S.; Albinet, G.

    2003-02-01

    Binary disordered systems are usually obtained by mixing two ingredients in variable proportions: conductor and insulator, or conductor and super-conductor. They present very specific properties, in particular the second-order percolation phase transition, with its fractal geometry and the multi-fractal properties of the current moments. These systems are naturally modeled by regular bi-dimensional or tri-dimensional lattices, on which sites or bonds are chosen randomly with given probabilities. The two significant parameters are the ratio h = σ1/σ of the complex conductances, σ and σ1, of the two components, and their relative abundances p (or, respectively, 1 - p). In this article, we calculate the impedance of the composite by two independent methods: the so-called spectral method, which diagonalises Kirchhoff's Laws via a Green function formalism, and the Exact Numerical Renormalization method (ENR). These methods are applied to mixtures of resistors and capacitors (R-C systems), simulating e.g. ionic conductor-insulator systems, and to composites constituted of resistive inductances and capacitors (LR-C systems), representing metal inclusions in a dielectric bulk. The frequency dependent impedances of the latter composites present very intricate structures in the vicinity of the percolation threshold. In this paper, we analyse the LR-C behavior of compounds formed by the inclusion of small conducting clusters (``n-legged animals'') in a dielectric medium. We investigate in particular their absorption spectra who present a pattern of sharp lines at very specific frequencies of the incident electromagnetic field, the goal being to identify the signature of each animal. This enables us to make suggestions of how to build compounds with specific absorption or transmission properties in a given frequency domain.

  10. Photonic Crystal Polarizing and Non-Polarizing Beam Splitters

    Institute of Scientific and Technical Information of China (English)

    GUAN Chun-Ying; SHI Jin-Hui; YUAN Li-Bo

    2008-01-01

    A polarizing beam splitter(PBS)and a non-polarizing beam splitter(NPBS)based on a photonic crystal(PC)directional coupler are demonstrated.The photonic crystal directional coupler consists of a hexagonal lattice of dielectric pillars in air and has a complete photonic band gap.The photonic band structure and the band gap map are calculated using the plane wave expansion(PWE)method.The splitting properties of the splitter are investigated numerically using the finite difference time domain(FDTD)method.

  11. Magnetic and dielectric properties of Mn2V2O7

    Science.gov (United States)

    Sannigrahi, J.; Giri, S.; Majumdar, S.

    2016-02-01

    The magnetic and dielectric properties of the manganese di-vanadate compound Mn2V2O7 are reported. The sample shows martensitic type structural transition close to room temperature which is evident both in the magnetic and dielectric data. Mn2V2O7 shows signature of antiferromagnetic type ordering around 17 K with concomitant anomaly in the dielectric properties at the same point, although no spontaneous electric polarization was found below 17 K. This clearly signifies a magnetic order driven electric anomaly and possibly it is antiferroelectric type with no net polarization. The dielectric relaxation behaviours show marked difference across the structural transition close to room temperature. Interestingly, the sample shows reversible switching behaviour across the structural transition close to 300 K between high and low dielectric states which can have important practical applications.

  12. Raman Spectra of High-κ Dielectric Layers Investigated with Micro-Raman Spectroscopy Comparison with Silicon Dioxide

    OpenAIRE

    Borowicz, P.; A. Taube; Rzodkiewicz, W.; Latek, M.; S. Gierałtowska

    2013-01-01

    Three samples with dielectric layers from high- κ dielectrics, hafnium oxide, gadolinium-silicon oxide, and lanthanum-lutetium oxide on silicon substrate were studied by Raman spectroscopy. The results obtained for high- κ dielectrics were compared with spectra recorded for silicon dioxide. Raman spectra suggest the similarity of gadolinium-silicon oxide and lanthanum-lutetium oxide to the bulk nondensified silicon dioxide. The temperature treatment of hafnium oxide shows the evolution of the...

  13. Polar molecule dominated electrorheological effect

    Institute of Scientific and Technical Information of China (English)

    Lu Kun-Quan; Shen Rong; Wang Xue-Zhao; Sun Gang; Wen Wei-Jia; Liu Ji-Xing

    2006-01-01

    The yield stress of our newly developed electrorheological (ER) fluids consisting of dielectric nano-particles suspended in silicone oil reaches hundreds of kPa, which is orders of magnitude higher than that of conventional ones. We found that the polar molecules adsorbed on the particles play a decisive role in such new ER fluids. To explain this polar molecule dominated ER (PM-ER) effect a model is proposed based on the interaction of polar molecule-charge between the particles, where the local electric field is significantly enhanced and results in the polar molecules aligning in the direction of the electric field. The model can well explain the giant ER effect and a near-linear dependence of the yield stress on the electric field. The main effective factors for achieving high-performance PM-ER fluids are discussed. The PM-ER fluids with the yield stress higher than one MPa can be expected.

  14. Inhomogeneous screening near the dielectric interface

    Science.gov (United States)

    Wang, Rui; Wang, Zhen-Gang

    2016-04-01

    Screening is one of the most important concepts in the study of charged systems. Near a dielectric interface, the ion distribution in a salt solution can be highly nonuniform. Here, we develop a theory that self-consistently treats the inhomogeneous screening effects. At higher concentrations when the bulk Debye screening length is comparable to the Bjerrum length, the double layer structure and interfacial properties are significantly affected by the inhomogeneous screening. In particular, the depletion zone is considerably wider than that predicted by the bulk screening approximation or the WKB approximation. The characteristic length of the depletion layer in this regime scales with the Bjerrum length, resulting in a linear increase of the negative adsorption of ions with concentration, in agreement with experiments. For asymmetric salts, inhomogeneous screening leads to enhanced charge separation and surface potential.

  15. High temperature dielectric relaxation anomaly of Y3+ and Mn2+ doped barium strontium titanate ceramics

    Science.gov (United States)

    Yan, Shiguang; Mao, Chaoliang; Wang, Genshui; Yao, Chunhua; Cao, Fei; Dong, Xianlin

    2014-10-01

    Relaxation like dielectric anomaly is observed in Y3+ and Mn2+ doped barium strontium titanate ceramics when the temperature is over 450 K. Apart from the conventional dielectric relaxation analysis method with Debye or modified Debye equations, which is hard to give exact temperature dependence of the relaxation process, dielectric response in the form of complex impedance, assisted with Cole-Cole impedance model corrected equivalent circuits, is adopted to solve this problem and chase the polarization mechanism in this paper. Through this method, an excellent description to temperature dependence of the dielectric relaxation anomaly and its dominated factors are achieved. Further analysis reveals that the exponential decay of the Cole distribution parameter n with temperature is confirmed to be induced by the microscopic lattice distortion due to ions doping and the interaction between the defects. At last, a clear sight to polarization mechanism containing both the intrinsic dipolar polarization and extrinsic distributed oxygen vacancies hopping response under different temperature is obtained.

  16. A dipole in a dielectric Intriguing results and shape dependence of the distant electric field

    CERN Document Server

    Amaral, R L P G

    2003-01-01

    The field of a point electric dipole in an infinite dielectric is obtained by placing the dipole at the center of a spherical cavity of radius $R$ inside the dielectric and then letting $R\\to 0$. The result disagrees with the elementary answer found in textbooks. The mathematical and physical reasons for the disagreement are discussed. The discrepancy is confirmed by the same limiting procedure applied to a uniformly polarized sphere embedded in the dielectric. We next solve the same problem for a polarized spheroid immersed in an infinite dielectric and find that the asymptotic potential shows an unexpected shape dependence, even after taking the limit of an arbitrarily small spheroid. By considering both oblate and prolate spheroids and taking appropriate limits, we recover either the elementary textbook answer or the previous result found for the polarized sphere.

  17. Dielectric Constant of Suspensions

    Science.gov (United States)

    Mendelson, Kenneth S.; Ackmann, James J.

    1997-03-01

    We have used a finite element method to calculate the dielectric constant of a cubic array of spheres. Extensive calculations support preliminary conclusions reported previously (K. Mendelson and J. Ackmann, Bull. Am. Phys. Soc. 41), 657 (1996).. At frequencies below 100 kHz the real part of the dielectric constant (ɛ') shows oscillations as a function of the volume fraction of suspension. These oscillations disappear at low conductivities of the suspending fluid. Measurements of the dielectric constant (J. Ackmann, et al., Ann. Biomed. Eng. 24), 58 (1996). (H. Fricke and H. Curtis, J. Phys. Chem. 41), 729 (1937). are not sufficiently sensitive to show oscillations but appear to be consistent with the theoretical results.

  18. PREFACE: Dielectrics 2013

    Science.gov (United States)

    Hadjiloucas, Sillas; Blackburn, John

    2013-11-01

    This volume records the 42nd Dielectrics Group Proceedings of the Dielectrics Conference that took place at the University of Reading UK from 10-12 April 2013. The meeting is part of the biennial Dielectrics series of the Dielectrics Group, and formerly Dielectrics Society, and is organised by the Institute of Physics. The conference proceedings showcase some of the diversity and activity of the Dielectrics community worldwide, and bring together contributions from academics and industrial researchers with a diverse background and experiences from the Physics, Chemistry and Engineering communities. It is interesting to note some continuing themes such as Insulation/HV Materials, Dielectric Spectroscopy, Dielectric Measurement Techniques and Ferroelectric materials have a growing importance across a range of technologically important areas from the Energy sector to Materials research, Semiconductor and Electronics industries, and Metrology. We would like to thank all of our colleagues and friends in the Dielectrics community who have supported this event by contributing manuscripts and participating in the event. The conference has provided excellent networking opportunities for all delegates. Our thanks go also to our theme chairs: Dr Stephen Dodd (University of Leicester) on Insulation/HV Materials, Professor Darryl Almond (University of Bath) on Dielectric Spectroscopy, Dr John Blackburn (NPL) on Dielectric Measurement Techniques and Professor Anthony R West (University of Sheffield) on Ferroelectric Materials. We would also like to thank the other members of the Technical Programme Committee for their support, and refereeing the submitted manuscripts. Our community would also like to wish a full recovery to our plenary speaker Prof John Fothergill (City University London) who was unexpectedly unable to give his talk as well as thank Professor Alun Vaughan for stepping in and giving an excellent plenary lecture in his place at such very short notice. We are also

  19. Development of dielectric microcalorimeter

    International Nuclear Information System (INIS)

    A prototype dielectric microcalorimeter was fabricated from 0.99SrTiO3-0.01SrTa2O6, a dielectric material. To estimate the operation performance of the microcalorimeter, a simple evaluation model is introduced by employing the block diagram formalism. Pulse height and fall time constant of the detection signal are analyzed as a function of the thermal conductance of the heat link. The dielectric microcalorimeter maintained at 100 mK was irradiated by 5.5 MeV α-particles emitting from an 241Am source. Responsivity was found to be 2.7x10-19 C/eV. (author)

  20. Reduced dielectric response in spatially varying electric fields

    DEFF Research Database (Denmark)

    Hansen, Jesper Schmidt

    2015-01-01

    In this paper, the dynamical equation for polarization is derived. From this the dielectric response to a spatially varying electric field is analyzed showing a reduced response due to flux of polarization in the material. This flux is modeled as a diffusive process through linear constitutive...... relations between the flux and the gradient of the polarization. Comparison between the theory and molecular dynamics simulations confirms this effect. The effect is significant for small length scale electric field variations and the inclusion of the flux is thus important in nanoscale modeling...

  1. Plasmonic Route to Reconfigurable Polarization Optics

    CERN Document Server

    Li, L; Tang, X M; Wang, S M; Wang, Q J; Zhu, S N

    2014-01-01

    Surface plasmon polariton (SPP) as a bounded mode on a metal/dielectric interface intrinsically has a definite transverse magnetic (TM) polarization that usually lacks further manipulations. However, the in-plane longitudinal components of SPP field can produce versatile polarization states when two orthogonal propagating SPP interfere with each other. Here, we demonstrated a plasmonic polarization router by designing appropriate nanohole arrays that can selectively scatter the interfered SPP fields to desired light beams. It is well proved that our device is able to reconfigure a certain input polarization to all kinds of states with respect to a scattered light. Accompanied with a composite phase modulation by diffractions, multiple focusing beams with different polarization states are simultaneously achieved, promising the possibility in polarization multiplexing and related signal processing. Our design offers a new route for achieving full control of the optical polarizations as well as the optical spin-...

  2. Dielectric behaviour of Zn substituted Cu nano-ferrites

    Energy Technology Data Exchange (ETDEWEB)

    Parashar, Jyoti, E-mail: phyjyoti.2@gmail.com [Department of Physics, University of Rajasthan, Jaipur 302055 (India); Saxena, V.K.; Jyoti; Bhatnagar, Deepak [Department of Physics, University of Rajasthan, Jaipur 302055 (India); Sharma, K.B. [Department of Physics, S.S. Jain Subodh P.G. College, Jaipur 302004 (India)

    2015-11-15

    Herein, the dielectric properties such as permittivity (real part ε′ and imaginary part ε′′) and dielectric loss tangent (tan δ) are reported for Zn substituted Cu ferrites (Cu{sub 1−x}Zn{sub x}Fe{sub 2}O{sub 4}; 0≤x≤1) composite using the sol–gel auto-combustion method. The variations of real and imaginary part of dielectric constant, tan δ and AC conductivity (σ{sub ac}) are studied at room temperature in the frequency range of 100 Hz–120 MHz. The real part of dielectric constant decrease with increasing frequency and the imaginary part (ε′′) varies with frequency showing the characteristic peak for each sample. The relation of tan δ with frequency shows relaxation spectra. Further, the σ{sub ac} tended to increase with increase in frequency. The variation in dielectric constant may be explained on the basis of space charge polarization, according to Maxwell and Wagner two-layer model. The dielectric constant and tan δ as a function of temperature are also studied with different temperatures ranging from 323 K to 583 K. - Highlights: • Zn substituted Cu nano-ferrite samples bearing formula Cu{sub 1−x}Zn{sub x}Fe{sub 2}O{sub 4}(0≤x≤1) are synthesized by the sol–gel auto combustion method. • The variation of real and imaginary parts of dielectric constant, dielectric loss tangent (tan δ) and AC conductivity with frequency are reported in the frequency range from 100 Hz to 120 MHz at room temperature. • The real part of dielectric constant (ε′) decreases with increasing frequency where as the AC conductivity (σ{sub ac}) increases with increase in frequency. The relation of tan δ with frequency shows relaxation spectra. • The variation in dielectric constant may be explained on the basis of space charge polarization, according to Maxwell and Wagner two-layer model. • Dielectric constant as a function of temperature is studied at different temperatures ranging from 323 K to 583 K.

  3. Dielectric measurements of activated electrorheological fluids (ERF)

    Energy Technology Data Exchange (ETDEWEB)

    Korobko, E. [Academy of Sciences of Belarus, Minsk (Belarus). Heat and Mass Transfer Inst.

    1994-12-31

    The dependence of the dielectric characteristics of electrorheological fluids of different compositions on the electric field intensity and frequency has been found experimentally. The observed variation of tg{delta} and {epsilon} are attributed to the relaxations between polarization and electric conductivity inducing heavy structurization in the ERF. ER suspensions find wide application in mechanical engineering, instrument manufacture, motor-car industry, robotics, aerospace technology, and ship-building industry. Perspective developments of valves without moving parts, clamps, brakes and shock absorbers, vibro-protection systems, hydraulic drives, step-by-step motors, two-stage batching devices, clutches, tensioning devices, display units, acoustic lenses, delay units and many others are known.

  4. Multilayer dielectric diffraction gratings

    Science.gov (United States)

    Perry, Michael D.; Britten, Jerald A.; Nguyen, Hoang T.; Boyd, Robert; Shore, Bruce W.

    1999-01-01

    The design and fabrication of dielectric grating structures with high diffraction efficiency used in reflection or transmission is described. By forming a multilayer structure of alternating index dielectric materials and placing a grating structure on top of the multilayer, a diffraction grating of adjustable efficiency, and variable optical bandwidth can be obtained. Diffraction efficiency into the first order in reflection varying between 1 and 98 percent has been achieved by controlling the design of the multilayer and the depth, shape, and material comprising the grooves of the grating structure. Methods for fabricating these gratings without the use of ion etching techniques are described.

  5. On the Theory of Dielectric Spectroscopy of Protein Solutions

    CERN Document Server

    Matyushov, Dmitry V

    2012-01-01

    We present a theory of the dielectric response of a solution containing large solutes, of a nanometer size, in a molecular solvent. It combines the molecular dipole moment of the solute with the polarization of a large subensemble of solvent molecules at the solute-solvent interface. The goal of the theory is two-fold: (i) to formulate the problem of the dielectric response avoiding the reliance on the cavity-field concepts of dielectric theories and (ii) to separate the non-additive polarization of the interface, jointly produced by the external field of the laboratory experiment and the solute, from specific solute-solvent interactions contributing to the dielectric signal. The theory is applied to experimentally reported frequency-dependent dielectric spectra of lysozyme in solution. The analysis of the data in the broad range of frequencies up to 700 GHz shows that the cavity field susceptibility, critical for the theory formulation, is consistent with the prediction of Maxwell's electrostatics in the fre...

  6. An experimental investigation of the dielectric properties of electrorheological fluids

    International Nuclear Information System (INIS)

    A home-made electrorheological (ER) fluid, known as ETSERF, has been created with suspension-based powders dispersed in silicone oil. Because of the special structure of their particles, ETSERF suspensions present a complex behavior. In the absence of an electric field, the ETSERF fluid manifests a near-Newtonian behavior, but when an electric field is applied, it exhibits a pseudoplastic behavior with yield stress. The ER effect under DC electric fields has been experimentally investigated using both hydrous and anhydrous ER fluids. The ER properties are strongly dependent on the dielectric properties of ETSERF suspensions, and hydrous ER fluids have a high dielectric constant and a high relaxation frequency which show a strong electrorheological effect. The relationship between the electrorheological effect and the permittivity of ER fluids has also been extensively studied. Experimental results show that the interfacial polarization plays an important role in the electrorheological phenomenon. The ageing of ETSERF fluids was also studied and it was found that the dielectric properties (mainly the dielectric loss tangent) and ER properties are strongly related to the duration of ageing. A fresh ETSERF suspension exhibits high relaxation frequency and high dielectric constant. These results are mainly explained by the effect of interfacial polarizations

  7. Crystal structure, thermal, dielectric and vibrational properties of a novel polar crystal: 4-Aminopyridinium-hydrogen maleate-maleic acid, [4-NH 2 C 5 H 4 NH][C 4 H 3 O 4 ][C 4 H 4 O 4

    Science.gov (United States)

    Tarasiewicz, J.; Gągor, A.; Jakubas, R.; Kulicka, B.; Baran, J.

    2011-09-01

    [4-NH 2C 5H 4NH][C 4H 3O 4][C 4H 4O 4] (APM) complex with rare stoichiometric ratio 1:2 has been synthesized and characterized by a single-crystal X-ray diffraction and powder X-ray diffraction in a wide temperature range (from 100 K up to 338 K), calorimetry and dielectric spectroscopy. The APM undergoes structural phase transition at 307/312 K (cooling/heating) of first order type classified as an order-disorder. The crystal structure of APM below 307 K consists of ordered 4-aminopyridinium cations, hydrogen maleate anions (HM) and neutral maleic acid molecules (MM) that interact via hydrogen bonds. The room temperature phase II and the high temperature phase one I is polar, space group P2 1, which is confirmed by the pyroelectric effect. The I → II phase transition is accompanied by a distinct electric permittivity anomaly ( ɛmax ≈ 55 at 150 kHz) that is characteristic of ferroelectric crystals. The infrared spectra of polycrystalline APM are presented and compared with other closely related analogs.

  8. Dyes with high dielectric constants

    OpenAIRE

    Langhals, Heinz

    1988-01-01

    The dielectric constants of perylene dyes, perylene-3,4: 9,10-tetracarboxylic bisimides, are reported. With aromatic substituents, dielectric constants up to 110 are obtained. With polymeric dyes, the dielectric constants rise to 260. Mechanisms and applications are discussed.

  9. Characterizing dielectric tensors of anisotropic materials from a single measurement

    Science.gov (United States)

    Smith, Paula Kay

    Ellipsometry techniques look at changes in polarization states to measure optical properties of thin film materials. A beam reflected from a substrate measures the real and imaginary parts of the index of the material represented as n and k, respectively. Measuring the substrate at several angles gives additional information that can be used to measure multilayer thin film stacks. However, the outstanding problem in standard ellipsometry is that it uses a limited number of incident polarization states (s and p). This limits the technique to isotropic materials. The technique discussed in this paper extends the standard process to measure anisotropic materials by using a larger set of incident polarization states. By using a polarimeter to generate several incident polarization states and measure the polarization properties of the sample, ellipsometry can be performed on biaxial materials. Use of an optimization algorithm in conjunction with biaxial ellipsometry can more accurately determine the dielectric tensor of individual layers in multilayer structures. Biaxial ellipsometry is a technique that measures the dielectric tensors of a biaxial substrate, single-layer thin film, or multi-layer structure. The dielectric tensor of a biaxial material consists of the real and imaginary parts of the three orthogonal principal indices (n x + ikx, ny +iky and nz + i kz) as well as three Euler angles (alpha, beta and gamma) to describe its orientation. The method utilized in this work measures an angle-of-incidence Mueller matrix from a Mueller matrix imaging polarimeter equipped with a pair of microscope objectives that have low polarization properties. To accurately determine the dielectric tensors for multilayer samples, the angle-of-incidence Mueller matrix images are collected for multiple wavelengths. This is done in either a transmission mode or a reflection mode, each incorporates an appropriate dispersion model. Given approximate a priori knowledge of the dielectric

  10. On the theory of dielectric spectroscopy of protein solutions

    International Nuclear Information System (INIS)

    We present a theory of the dielectric response of solutions containing large solutes, of the nanometer size, in a molecular solvent. It combines the molecular dipole moment of the solute with the polarization of a large subensemble of solvent molecules at the solute-solvent interface. The goal of the theory is two-fold: (i) to formulate the problem of the dielectric response avoiding the reliance on the cavity-field susceptibility of dielectric theories and (ii) to separate the non-additive polarization of the interface, jointly produced by the external field of the laboratory experiment and the solute, from specific solute-solvent interactions contributing to the dielectric signal. The theory is applied to experimentally reported frequency-dependent dielectric spectra of lysozyme in solution. The analysis of the data in the broad range of frequencies up to 700 GHz shows that the cavity-field susceptibility, critical for the theory formulation, is consistent with the prediction of Maxwell’s electrostatics in the frequency range of 10-200 GHz, but deviates from it outside this range. In particular, it becomes much smaller than the Maxwell result, and shifts to negative values, at small frequencies. The latter observation implies a dia-electric response, or negative dielectrophoresis, of hydrated lysozyme. It also implies that the effective protein dipole recorded by dielectric spectroscopy is much smaller than the value calculated from the protein’s charge distribution. We suggest an empirical equation that describes both the increment of the static dielectric constant and the decrement of the Debye water peak with increasing protein concentration. It gives fair agreement with broad-band dispersion and loss spectra of protein solutions, but misses the δ-dispersion region. (paper)

  11. Structural and magneto-dielectric properties of rare earth based double perovskites RE2NiMnO6 (RE = La, Pr, Sm, Tb)

    International Nuclear Information System (INIS)

    Double perovskite oxides, A2B'B''O6, (A- alkaline earth metals such as Ca, Ba, Sr etc., or rare earth ions of larger ionic radii, B' and B''-transition metal cations or lanthanides with smaller ionic radii) have received paramount of interest since they provide a unique opportunity to induce and control multiferroic behaviors in oxide systems. Among the rare earth based double perovskites La2NiMnO6, a single material platform with multiple functions such as ferromagnetic semiconductor, spin-phonon and magnetoelectric coupling properties near ambient temperature, is expected to lead to unprecedented device applications. These complex physical properties are arising from competing interactions between magnetic (spins), structural (phonons) and polarization (charges) order parameters. While most transition metal involved single perovskites are antiferromagnetic insulators due to negative super exchange interaction between the transition metal ions, distorted double perovskite La2NiMnO6 is a ferromagnetic insulator due to positive super exchange interaction between Ni and Mn cations. Such behavior is significant for exploring spintronics materials since it allows magneto-dielectric properties to be achieved. It has been observed, the properties of the La2NiMnO6 will generally change noticeably with the substitution of La ion by Rare-Earth (RE) elements with smaller ionic radii. Moreover, the entire series of these oxides (RE2NiMnO6) have been reported to be ferromagnetic with a decrease in Tc, but the investigation of RE2NiMnO6 ceramics is relatively sparse as compared to La2NiMnO6. The present investigation focuses on the structural and magneto-dielectric properties of RE2NiMnO6 (RE = La, Pr, Sm, Tb). The pure monoclinic bulk phase of RE2NiMnO6 is an intrinsic B-site disordered ferromagnet showing interesting magnetic phase transitions due to the inherent coupling of Ni - Mn network with RE3+ ion. Further, the high dielectric permittivity

  12. Static dielectric properties of dense ionic fluids.

    Science.gov (United States)

    Zarubin, Grigory; Bier, Markus

    2015-05-14

    The static dielectric properties of dense ionic fluids, e.g., room temperature ionic liquids (RTILs) and inorganic fused salts, are investigated on different length scales by means of grandcanonical Monte Carlo simulations. A generally applicable scheme is developed which allows one to approximately decompose the electric susceptibility of dense ionic fluids into the orientation and the distortion polarization contribution. It is shown that at long range, the well-known plasma-like perfect screening behavior occurs, which corresponds to a diverging distortion susceptibility, whereas at short range, orientation polarization dominates, which coincides with that of a dipolar fluid of attached cation-anion pairs. This observation suggests that the recently debated interpretation of RTILs as dilute electrolyte solutions might not be simply a yes-no-question but it might depend on the considered length scale. PMID:25978895

  13. Dielectric, ferroelectric and pyroelectric properties of PMNT ceramics

    International Nuclear Information System (INIS)

    In the present study, different PMNT samples in the MPB range were prepared in single perovskite phase using Columbite technique. After poling, dielectric constant (εr) of PMNT 70/30 samples decreases and of PMNT 68/32 and PMNT 66/34 samples increases. Polarization vs. electric field (P-E) hysteresis loops of PMNT samples show their ferroelectric nature. Transition temperature (Tc) obtained from pyroelectric coefficient (pi) variation with temperature increases with the increase in PT content in PMNT samples near MPB and agrees with Tc obtained from the dielectric study

  14. The general dielectric tensor for bi-kappa magnetized plasmas

    CERN Document Server

    Gaelzer, Rudi; Meneses, Anelise Ramires

    2016-01-01

    In this paper we derive the dielectric tensor for a plasma containing particles described by an anisotropic superthermal (bi-kappa) velocity distribution function. The tensor components are written in terms of the two-variables kappa plasma special functions, recently defined by Gaelzer and Ziebell [Phys. Plasmas 23, 022110 (2016)]. We also obtain various new mathematical properties for these functions, which are useful for the analytical treatment, numerical implementation and evaluation of the functions and, consequently, of the dielectric tensor. The formalism developed here and in the previous paper provides a mathematical framework for the study of electromagnetic waves propagating at arbitrary angles and polarizations in a superthermal plasma.

  15. Dual band metamaterial perfect absorber based on artificial dielectric "molecules".

    Science.gov (United States)

    Liu, Xiaoming; Lan, Chuwen; Li, Bo; Zhao, Qian; Zhou, Ji

    2016-01-01

    Dual band metamaterial perfect absorbers with two absorption bands are highly desirable because of their potential application areas such as detectors, transceiver system, and spectroscopic imagers. However, most of these dual band metamaterial absorbers proposed were based on resonances of metal patterns. Here, we numerically and experimentally demonstrate a dual band metamaterial perfect absorber composed of artificial dielectric "molecules" with high symmetry. The artificial dielectric "molecule" consists of four "atoms" of two different sizes corresponding to two absorption bands with near unity absorptivity. Numerical and experimental absorptivity verify that the dual-band metamaterial absorber is polarization insensitive and can operate in wide-angle incidence. PMID:27406699

  16. Analysis of the temporal electric fields in lossy dielectric media

    DEFF Research Database (Denmark)

    McAllister, Iain Wilson; Crichton, George C

    1991-01-01

    The time-dependent electric fields associated with lossy dielectric media are examined. The analysis illustrates that, with respect to the basic time constant, these lossy media can take a considerable time to attain a steady-state condition. Time-dependent field enhancement factors are considered......, and inherent surface-charge densities quantified. The calculation of electrostatic forces on a free, lossy dielectric particle is illustrated. An extension to the basic analysis demonstrates that, on reversal of polarity, the resultant tangential field at the interface could play a decisive role...

  17. Microstrip Antenna Generates Circularly Polarized Beam

    Science.gov (United States)

    Huang, J.

    1986-01-01

    Circular microstrip antenna excited with higher order transverse magnetic (TM) modes generates circularly polarized, conical radiation patterns. Found both theoretically and experimentally that peak direction of radiation pattern is varied within wide angular range by combination of mode selection and loading substrate with materials of different dielectric constants.

  18. Measurements on polar liquids at a microwave frequency – evaluation of molecular parameters – a new method

    Indian Academy of Sciences (India)

    M B R Murthy; B S Dyasagar; R L Patil

    2003-10-01

    A simple method of estimating the dipole moment () and relaxation time () of polar molecules in liquid state, from a single set of dielectric measurements at high frequency, is proposed by using the concept of dielectric virial coefficients and employing Onsager model. The proposed method is tested in a number of polar liquids and the results are discussed.

  19. AC conductivity and dielectric properties of Te doped LaMnO3

    International Nuclear Information System (INIS)

    We have studied the structural and dielectric properties of La1-xTexMnO3 (x=0.00, 0.10 and 0.20) samples. All the samples show a rhombohedral structure with space group R3-bar c, at room temperature. The dielectric constant and the ac conductivity are measured at room temperature as a function of frequency, ranging from (75 KHz-7MHz).The dielectric constant shows a normal behaviour and the dielectric loss tangent exhibit anomalous behaviour. The ac conductivity obeys super linear power law σ(ω)= Bωn. The real part (ω'), imaginary part (ω) of dielectric constant, loss tangent, and ac conductivity have been explained on the basis of space charge polarization according to Maxwell-Wagner's two layer model and Koops phenomenological theory. The occurrence of giant or colossal dielectric constant is most likely due to electrode polarization or interface polarization effect. The depletion layers arising due to the formation of Schottky diodes at the metallic contacts of semiconducting samples, which may be formed by grain boundaries, can give rise to Maxwell-Wagner type relaxation and apparently very high dielectric constants. (author)

  20. Isotopic signatures by bulk analyses

    International Nuclear Information System (INIS)

    Los Alamos National Laboratory has developed a series of measurement techniques for identification of nuclear signatures by analyzing bulk samples. Two specific applications for isotopic fingerprinting to identify the origin of anthropogenic radioactivity in bulk samples are presented. The first example is the analyses of environmental samples collected in the US Arctic to determine the impact of dumping of radionuclides in this polar region. Analyses of sediment and biota samples indicate that for the areas sampled the anthropogenic radionuclide content of sediments was predominantly the result of the deposition of global fallout. The anthropogenic radionuclide concentrations in fish, birds and mammals were very low. It can be surmised that marine food chains are presently not significantly affected. The second example is isotopic fingerprinting of water and sediment samples from the Rocky Flats Facility (RFP). The largest source of anthropogenic radioactivity presently affecting surface-waters at RFP is the sediments that are currently residing in the holding ponds. One gram of sediment from a holding pond contains approximately 50 times more plutonium than 1 liter of water from the pond. Essentially 100% of the uranium in Ponds A-1 and A-2 originated as depleted uranium. The largest source of radioactivity in the terminal Ponds A-4, B-5 and C-2 was naturally occurring uranium and its decay product radium. The uranium concentrations in the waters collected from the terminal ponds contained 0.05% or less of the interim standard calculated derived concentration guide for uranium in waters available to the public. All of the radioactivity observed in soil, sediment and water samples collected at RFP was naturally occurring, the result of processes at RFP or the result of global fallout. No extraneous anthropogenic alpha, beta or gamma activities were detected. The plutonium concentrations in Pond C-2 appear to vary seasonally

  1. Bulk chemicals from biomass

    NARCIS (Netherlands)

    Haveren, van J.; Scott, E.L.; Sanders, J.P.M.

    2008-01-01

    Given the current robust forces driving sustainable production, and available biomass conversion technologies, biomass-based routes are expected to make a significant impact on the production of bulk chemicals within 10 years, and a huge impact within 20-30 years. In the Port of Rotterdam there is a

  2. Ferromagnetic bulk glassy alloys

    International Nuclear Information System (INIS)

    This paper deals with the review on the formation, thermal stability and magnetic properties of the Fe-based bulk glassy alloys in as-cast bulk and melt-spun ribbon forms. A large supercooled liquid region over 50 K before crystallization was obtained in Fe-(Al, Ga)-(P, C, B, Si), Fe-(Cr, Mo, Nb)-(Al, Ga)-(P, C, B) and (Fe, Co, Ni)-Zr-M-B (M=Ti, Hf, V, Nb, Ta, Cr, Mo and W) systems and bulk glassy alloys were produced in a thickness range below 2 mm for the Fe-(Al, Ga)-(P, C, B, Si) system and 6 mm for the Fe-Co-(Zr, Nb, Ta)-(Mo, W)-B system by copper-mold casting. The ring-shaped glassy Fe-(Al, Ga)-(P, C, B, Si) alloys exhibit much better soft magnetic properties as compared with the ring-shaped alloy made from the melt-spun ribbon because of the formation of the unique domain structure. The good combination of high glass-forming ability and good soft magnetic properties indicates the possibility of future development as a new bulk glassy magnetic material

  3. Heat transport in bulk/nanoporous/bulk silicon devices

    Energy Technology Data Exchange (ETDEWEB)

    Criado-Sancho, M. [Departamento de Ciencias y Técnicas Físicoquimicas, Facultad de Ciencias, UNED, Senda del Rey 9, 20040 Madrid (Spain); Jou, D., E-mail: David.Jou@uab.cat [Departament de Física, Universitat Autònoma de Barcelona, 08193 Bellaterra, Catalonia (Spain); Institut d' Estudis Catalans, Carme 47, 08001 Barcelona, Catalonia (Spain)

    2013-02-04

    We study heat transport in bulk/nanoporous/bulk silicon devices; we show that, despite bulk/nanoporous devices may act as thermal rectifiers, the non-linear aspects of their joint thermal conductance are not strong enough to lead to a negative differential thermal resistance, necessary to allow bulk/nanoporous/bulk Si devices to act as thermal transistors. Furthermore, we explicitly study the effective thermal conductivity of the mentioned devices for several temperatures, geometries, porosities, and pore size.

  4. Dielectric Properties of Rhombohedral PbNb2O6

    Directory of Open Access Journals (Sweden)

    Kriti Ranjan Sahu

    2013-01-01

    Full Text Available Dielectric materials are needed in many electrical and electronic applications. So, basic characterizations need to be done for all dielectrics. PbNb2O6 (PN is ferroelectric and piezoelectric only in its orthorhombic phase, with potential high temperature applications. So, its rhombohedral phase, frequently formed as an undesirable impurity in the preparation of orthorhombic PN, has been ignored with respect to possible dielectric characterizations. Here, essentially single phase rhombohedral PN has been prepared, checking structure from XRD Rietveld Analysis, and the real and imaginary parts of permittivity measured in an Impedance Spectrometer (IS up to ~700∘C and over 20 Hz to 5.5 MHz range, for heating and some cooling runs. Variations, with temperature, of relaxation time constant (τ, AC and DC conductivity, bulk resistance, activation energy and capacitance have been explored from our IS data.

  5. Dielectric behavior of manganese titanate in the paraelectric phase

    Science.gov (United States)

    Acharya, Truptimayee; Choudhary, R. N. P.

    2015-11-01

    Rhombohedral MnTiO3 powder has been synthesized by a high-temperature solid-state reaction method. The formation of single-phase compound is confirmed through XRD, Rietveld refinement and FTIR analysis. The optical band in MnTiO3 obtained from the UV-Vis absorption spectrum has been analyzed. The study of SEM micrographs suggested that the prepared material has good sinter ability and high density with homogeneous grain distribution on the surface and in the bulk. From the impedance and dielectric measurements, the electrical parameters were obtained. It was found that the magnitude of relative dielectric constant ( ɛ r) was relatively high with low dielectric loss. The study of frequency dependence of AC conductivity suggests that the material obeys Jonscher's universal power law. The variation of DC conductivity with inverse of absolute temperature follows the Arrhenius relation.

  6. Antenna with Dielectric Having Geometric Patterns

    Science.gov (United States)

    Dudley, Kenneth L. (Inventor); Elliott, Holly A. (Inventor); Cravey, Robin L. (Inventor); Connell, John W. (Inventor); Ghose, Sayata (Inventor); Watson, Kent A. (Inventor); Smith, Jr., Joseph G. (Inventor)

    2013-01-01

    An antenna includes a ground plane, a dielectric disposed on the ground plane, and an electrically-conductive radiator disposed on the dielectric. The dielectric includes at least one layer of a first dielectric material and a second dielectric material that collectively define a dielectric geometric pattern, which may comprise a fractal geometry. The radiator defines a radiator geometric pattern, and the dielectric geometric pattern is geometrically identical, or substantially geometrically identical, to the radiator geometric pattern.

  7. Short range ferromagnetic, magneto-electric, and magneto-dielectric effect in ceramic Co{sub 3}TeO{sub 6}

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Harishchandra, E-mail: singh85harish@gmail.com, E-mail: singh85harish@rrcat.gov.in; Ghosh, Haranath [Homi Bhabha National Institute, Raja Ramanna Center for Advanced Technology, Indore 452013 (India); Indus Synchrotrons Utilization Division, Raja Ramanna Center for Advanced Technology, Indore 452013 (India); Chandrasekhar Rao, T. V. [Technical Physics Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Sharma, G.; Saha, J.; Patnaik, S. [School of Physical Sciences, Jawaharlal Nehru University, New Delhi 110067 (India)

    2016-01-28

    We report observation of magneto-electric and magneto-dielectric couplings along with short range ferromagnetic order in ceramic Cobalt Tellurate (Co{sub 3}TeO{sub 6}, CTO) using magnetic, structural, dielectric, pyroelectric, and polarization studies. DC magnetization along with dielectric constant measurements indicate a coupling between magnetic order and electrical polarization. A strong anomaly in the dielectric constant at ∼17.4 K in zero magnetic field indicates spontaneous electric polarization, consistent with a recent neutron diffraction study. Observation of weak short range ferromagnetic order at lower temperatures is attributed to the Griffiths-like ferromagnetism. Furthermore, magnetic field dependence of the ferroelectric transition follows earlier theoretical predictions, applicable to single crystal CTO. Finally, combined dielectric, pyroelectric, and polarization measurements suggest that the ground state of CTO may possess spontaneous symmetry breaking in the absence of magnetic field.

  8. Electronic relaxation of deep bulk trap and interface state in ZnO ceramics

    Institute of Scientific and Technical Information of China (English)

    Yang Yan; Li Sheng-Tao; Ding Can; Cheng Peng-Fei

    2011-01-01

    This paper investigates the electronic relaxation of deep bulk trap and interface state in ZnO ceramics based on dielectric spectra measured in a wide range of temperature, frequency and bias, in addition to the steady state response. It discusses the nature of net current flowing over the barrier affected by interface state, and then obtains temperature-dependent barrier height by approximate calculation from steady Ⅰ-Ⅴ (current-voltage) characteristics. Additional conductance and capacitance arising from deep bulk trap relaxation are calculated based on the displacement of the cross point between deep bulk trap and Fermi level under small AC signal. Prom the resonances due to deep bulk trap relaxation on dielectric spectra, the activation energies are obtained as 0.22 eV and 0.35 eV, which are consistent with the electronic levels of the main defect interstitial Zn and vacancy oxygen in the depletion layer. Under moderate bias, another resonance due to interface relaxation is shown on the dielectric spectra. The DC-like conductance is also observed in high temperature region on dielectric spectra, and the activation energy is much smaller than the barrier height in steady state condition, which is attributed to the displacement current coming from the shallow bulk trap relaxation or other factors.

  9. Optimization of structural and dielectric properties of CdSe loaded poly(diallyl dimethyl ammonium chloride) polymer in a desired frequency and temperature window

    Energy Technology Data Exchange (ETDEWEB)

    Tyagi, Chetna, E-mail: ctyagi05@gmail.com; Sharma, Ambika, E-mail: ambikasharma2004@yahoo.com [Department of Applied Sciences, The NorthCap University (Formerly ITM University), Gurgaon, 122017 Haryana (India)

    2016-01-07

    In the present paper, investigations of CdSe loaded poly(diallyl dimethyl ammonium chloride) (PDADMAC) nanocomposites and pure PDADMAC synthesized by wet chemical technique have been carried out. Fourier transform infrared and X-ray diffraction analysis have been performed to reveal the structural details of pure polymer and polymer nanocomposite (PNC). The dielectric behavior of pure polymer and PNC has been recorded, which results in higher value of the real and imaginary part of dielectric constant for PNC, as compared with pure PDADMAC. The increase is attributed to the addition of CdSe quantum dots to the pure polymer. The contribution of ionic and electronic polarization has been observed at higher frequency. The theoretical fitting of Cole-Cole function to the experimental data of dielectric constant of PNC and pure PDADMAC results in the determination of relaxation time and conductivity of space charge carriers. The CdSe loaded polymer nanocomposite has been used as an electrolyte in the battery fabrication with configuration Al/PNC/Ag{sub 2}O. The ac conductivity measurements have been carried out for both samples in a frequency window of 1 kHz–5 MHz and at different temperatures varying from 298 K to 523 K. Activation energy (E{sub a}) has been determined for pure polymer as well as PNC and is found to be less for PNC, as compared with pure polymer. Further, impedance measurement at different temperatures results in two frequency ranges corresponding to ionic conduction and blocking electrode effect. The value of bulk resistance for pure polymer and PNC has been found to be 3660 Ω and 442 Ω, respectively, at 298 K temperature. Electric modulus has been determined and is observed to support the dielectric constant data; it further reveals the deviation from Debye behavior at a higher frequency.

  10. Optimization of structural and dielectric properties of CdSe loaded poly(diallyl dimethyl ammonium chloride) polymer in a desired frequency and temperature window

    International Nuclear Information System (INIS)

    In the present paper, investigations of CdSe loaded poly(diallyl dimethyl ammonium chloride) (PDADMAC) nanocomposites and pure PDADMAC synthesized by wet chemical technique have been carried out. Fourier transform infrared and X-ray diffraction analysis have been performed to reveal the structural details of pure polymer and polymer nanocomposite (PNC). The dielectric behavior of pure polymer and PNC has been recorded, which results in higher value of the real and imaginary part of dielectric constant for PNC, as compared with pure PDADMAC. The increase is attributed to the addition of CdSe quantum dots to the pure polymer. The contribution of ionic and electronic polarization has been observed at higher frequency. The theoretical fitting of Cole-Cole function to the experimental data of dielectric constant of PNC and pure PDADMAC results in the determination of relaxation time and conductivity of space charge carriers. The CdSe loaded polymer nanocomposite has been used as an electrolyte in the battery fabrication with configuration Al/PNC/Ag2O. The ac conductivity measurements have been carried out for both samples in a frequency window of 1 kHz–5 MHz and at different temperatures varying from 298 K to 523 K. Activation energy (Ea) has been determined for pure polymer as well as PNC and is found to be less for PNC, as compared with pure polymer. Further, impedance measurement at different temperatures results in two frequency ranges corresponding to ionic conduction and blocking electrode effect. The value of bulk resistance for pure polymer and PNC has been found to be 3660 Ω and 442 Ω, respectively, at 298 K temperature. Electric modulus has been determined and is observed to support the dielectric constant data; it further reveals the deviation from Debye behavior at a higher frequency

  11. Nonequilibrium Atom-Dielectric Forces Mediated by a Quantum Field

    OpenAIRE

    Behunin, Ryan Orson; Hu, Bei-Lok

    2011-01-01

    In this paper we give a first principles microphysics derivation of the nonequilibrium forces between an atom, treated as a three dimensional harmonic oscillator, and a bulk dielectric medium modeled as a continuous lattice of oscillators coupled to a reservoir. We assume no direct interaction between the atom and the medium but there exist mutual influences transmitted via a common electromagnetic field. By employing concepts and techniques of open quantum systems we introduce coarse-grainin...

  12. Design of 50nm Vertical MOSFET Incorporating a Dielectric Pocket

    OpenAIRE

    Donaghy, D; Hall, S.; De Groot, C. H. (Kees); Kunz, V. D.; Ashburn, P.

    2004-01-01

    A new architecture for a vertical MOS transistor is proposed that incorporates a so-calle dielectric pocket (DP) for suppression of short channel effects and bulk punch-through. We outline the advantages that the DP brings and propose a basic fabrication process to realize the device. The design issues of a 50-nm channel device are addressed by numerical simulation. The gate delay of an associated CMOS inverter is assessed in the context of the International Technology Roadmap for Semiconduct...

  13. Polarization charge: Theory and applications to aqueous interfaces

    Science.gov (United States)

    Shi, Bobo; Agnihotri, Mithila V.; Chen, Si-Han; Black, Richie; Singer, Sherwin J.

    2016-04-01

    When an electric field is applied across an interface, a dielectric will acquire a polarization charge layer, assumed infinitely thin in the theory of macroscopic dielectrics and also in most treatments of electrokinetic phenomena in nanoscale structures. In this work we explore the polarization charge layer in molecular detail. Various formal relations and a linear response theory for the polarization charge are presented. Properties of the polarization charge layer are studied for three aqueous interfaces: air-water, a crystalline silica surface with water, and an amorphous silica surface with water. The polarization charge is calculated from equilibrium simulations via linear response theory and from non-equilibrium simulations, and the results are within statistical error. The polarization charge is found to be distributed within a region whose width is on the order of a nanometer.

  14. Polarization charge: Theory and applications to aqueous interfaces.

    Science.gov (United States)

    Shi, Bobo; Agnihotri, Mithila V; Chen, Si-Han; Black, Richie; Singer, Sherwin J

    2016-04-28

    When an electric field is applied across an interface, a dielectric will acquire a polarization charge layer, assumed infinitely thin in the theory of macroscopic dielectrics and also in most treatments of electrokinetic phenomena in nanoscale structures. In this work we explore the polarization charge layer in molecular detail. Various formal relations and a linear response theory for the polarization charge are presented. Properties of the polarization charge layer are studied for three aqueous interfaces: air-water, a crystalline silica surface with water, and an amorphous silica surface with water. The polarization charge is calculated from equilibrium simulations via linear response theory and from non-equilibrium simulations, and the results are within statistical error. The polarization charge is found to be distributed within a region whose width is on the order of a nanometer. PMID:27131558

  15. Dielectric Wakefield Researches

    International Nuclear Information System (INIS)

    Excitation of wakefield in cylindrical dielectric waveguide/resonator by a sequence of relativistic electron bunches was investigated using an electron linac 'Almaz-2' (4.5 MeV, 6·103 bunches of duration 60 ps and charge 0.32 nC each). Energy spectrum of electrons, radial topography and longitudinal distribution of wakefield, and total energy of excited wakefield were measured by means of magnetic analyzer, high frequency probe, and a sensitive calorimeter

  16. New dielectric elastomers with improved properties for energy harvesting and actuation

    Science.gov (United States)

    Stiubianu, George; Bele, Adrian; Tugui, Codrin; Musteata, Valentina

    2015-02-01

    New materials with large value for dielectric constant were obtained by using siloxane and chemically modified lignin. The modified lignin does not act as a stiffening filler material for the siloxane but acts as bulk filler, preserving the softness and low value of Young's modulus specific for silicones. The measured values for dielectric constant compare positively with the ones for previously tested dielectric elastomers based on siloxane rubber or acrylic rubber loaded with ceramic nanoparticles. The new materials use the well-known silicone chemistry and lignin which is available worldwide in large amounts as a by-product of pulp and paper industry, making its manufacturing affordable. The prepared dielectric elastomers were tested for possible applications for wave, wind and kinetic body motion energy harvesting. Siloxane, lignin, dielectric

  17. Polarization Dependence of Linewidth Enhancement Factor in Semiconductor Optical Amplifier and Its Implication for Nonlinear Polarization Rotation

    Institute of Scientific and Technical Information of China (English)

    ZHAO Shuang; WU Chong-Qing; WANG Yong-Jun

    2009-01-01

    Linewidth enhancement factors (LEFs) of the transverse electric mode and the transverse magnetic mode in bulk semiconductor optical amplifiers are measured using the nonlinear optical loop mirror method and the principal state of polarization vector method.The polarization dependence of LEFs plays an important role in the nonlinear polarization rotation.The relationship between the polarization-dependence of LEFs and nonlinear polarization rotation in the Stokes space is demonstrated.

  18. The flexoelectric effect associated size dependent pyroelectricity in solid dielectrics

    Energy Technology Data Exchange (ETDEWEB)

    Bai, Gang, E-mail: baigang@njupt.edu.cn [Jiangsu Provincial Engineering Laboratory for RF Integration and Micropackaging and College of Electronic Science and Engineering, Nanjing University of Posts and Telecommunications, Nanjing 210023 (China); Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093 (China); Liu, Zhiguo [Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093 (China); Xie, Qiyun; Guo, Yanyan; Li, Wei [Jiangsu Provincial Engineering Laboratory for RF Integration and Micropackaging and College of Electronic Science and Engineering, Nanjing University of Posts and Telecommunications, Nanjing 210023 (China); Yan, Xiaobing [College of Electronic and information Engineering, Hebei University, Baoding 071002 (China)

    2015-09-15

    A phenomenological thermodynamic theory is used to investigate the effect of strain gradient on the pyroelectric effect in centrosymmetric dielectric solids. Direct pyroelectricity can exist as external mechanical stress is applied to non-pyroelectric dielectrics with shapes such as truncated pyramids, due to elastic strain gradient induced flexoelectric polarization. Effective pyroelectric coefficient was analyzed in truncated pyramids. It is found to be controlled by size, ambient temperature, stress, and aspect ratio and depends mainly on temperature sensitivity of flexoelectric coefficient (TSFC) and strain gradient of the truncated pyramids dielectric solids. These results show that the pyroelectric property of Ba{sub 0.67}Sr{sub 0.33}TiO{sub 3} above T{sub c} similar to PZT and other lead-based ferroelectrics can be obtained. This feature might widely broaden the selection of materials for infrared detectors with preferable properties.

  19. Modifications of the Dielectric Properties of Biological Membranes by Heating

    CERN Document Server

    Savescu, S B

    2004-01-01

    Biological cell suspensions are known to show dielectric dispersions due to the Maxwell-Wagner mechanism. Many examples are summarized in a number of papers by Schwan [7, 9, 10]. By the application of an appropriate analysis to the dielectric dispersion, it is possible to estimate electrical phase parameters related to protoplasm and cell membrane. A dielectric theory of interfacial polarization for a suspension of conducting particles (protoplasm) covered with poorly conducting shells (plasma membrane) was developed by Pauly and Schwan [7], and was satisfactory applied for low volume fractions of suspended particles (less than about 0.2). The purpose of this paper is to examine the change in yeast plasma membrane permittivity after heating treatment, by using the Pauly and Schwan's theory.

  20. The flexoelectric effect associated size dependent pyroelectricity in solid dielectrics

    International Nuclear Information System (INIS)

    A phenomenological thermodynamic theory is used to investigate the effect of strain gradient on the pyroelectric effect in centrosymmetric dielectric solids. Direct pyroelectricity can exist as external mechanical stress is applied to non-pyroelectric dielectrics with shapes such as truncated pyramids, due to elastic strain gradient induced flexoelectric polarization. Effective pyroelectric coefficient was analyzed in truncated pyramids. It is found to be controlled by size, ambient temperature, stress, and aspect ratio and depends mainly on temperature sensitivity of flexoelectric coefficient (TSFC) and strain gradient of the truncated pyramids dielectric solids. These results show that the pyroelectric property of Ba0.67Sr0.33TiO3 above Tc similar to PZT and other lead-based ferroelectrics can be obtained. This feature might widely broaden the selection of materials for infrared detectors with preferable properties

  1. Temporal variation of dielectric properties of preserved blood

    International Nuclear Information System (INIS)

    Rabbit blood was preserved at 277 K in Alsever's solution for 37 days, and its dielectric permittivity was monitored in a frequency range from 0.05 to 110 MHz throughout the period. The relaxation time and Cole-Cole parameter of the interfacial polarization process for erythrocytes remained nearly constant during the first 20 days and then started to increase and decrease, respectively. On the other hand, the relaxation strength and the cell volume fraction continued to decrease for 37 days, but the decrease rates of both changed discontinuously on about the 20th day. Microscope observation showed that approximately 90% of the erythrocytes were spinous echinocytes at the beginning of preservation and started to be transformed into microspherocytes around the 20th day. Therefore, dielectric spectroscopy is a sensitive tool to monitor the deterioration of preserved blood accompanied by morphological transition of erythrocytes through the temporal variation of their dielectric properties

  2. Bulk materials handling review

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2007-02-15

    The paper provides details of some of the most important coal handling projects and technologies worldwide. It describes development by Aubema Crushing Technology GmbH, Bedeschi, Cimbria Moduflex, DBT, Dynamic Air Conveying Systems, E & F Services, InBulk Technologies, Nord-Sen Metal Industries Ltd., Pebco Inc, Primasonics International Ltd., R.J.S. Silo Clean (International) Ltd., Takraf GmbH, and The ACT Group. 17 photos.

  3. Gold Photoluminescence: Wavelength and Polarization Engineering

    DEFF Research Database (Denmark)

    Andersen, Sebastian Kim Hjælm; Pors, Anders Lambertus; Bozhevolnyi, Sergey I.

    2015-01-01

    We demonstrate engineering of the spectral content and polarization of photoluminescence (PL) from arrayed gold nanoparticles atop a subwavelength-thin dielectric spacer and optically-thick gold film, a configuration that supports gap-surface plasmon resonances (GSPRs). Choice of shapes and...... dimensions of gold nanoparticles influences the GSPR wavelength and polarization characteristics, thereby allowing us to enhance and spectrally mold the plasmon-assisted PL while simultaneously controlling its polarization. In order to understand the underlying physics behind the plasmon-enhanced PL, we...

  4. Influence of absorbed moisture on the dielectric properties of epoxy resins

    OpenAIRE

    Dodd, S J; Chalashkanov, N. M.; Dissado, L. A.; Fothergill, J

    2010-01-01

    The dielectric response of two bisphenol-A epoxy resin systems Araldite CY1301 (Tg ~ 50°C) and Araldite CY1311 (Tg ~0°C) was studied at different levels of absorbed moisture. The dielectric measurements were carried out over the frequency range 1 mHz to 100 kHz and the results were characterised in terms of dc bulk electrical conduction and dielectric processes. The characteristic parameters (frequency and magnitude) of all processes have been found to be moisture dependent. In both resins ab...

  5. Dielectric behavior of a-Sn-Se-Pb-Ge chalcogenide glass

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Prashant, E-mail: prashantshrm5@gmail.com; Modgil, Vivek; Choudhary, Shobhana; Nidhi, A. V.; Rangra, V. S. [Department of Physics, Himachal Pradesh University, Summerhill Shimla 171005 (India)

    2015-05-15

    The bulk material Sn{sub 8}Se{sub 74}Pb{sub 18-x}Ge{sub x}(7≤x≤11) has been prepared by melt quenching technique. The viterous and glassy nature have been confirmed by X-Ray Diffraction (XRD) and Differential Scanning Calorimetery (DSC) techniques respectively. The material exhibits the good thermal stability and high value of glass transition temperature. The dielectric behavior has been studied in frequency range 50Hz-1MHz, using pallet method. The universal dielectric behaviour of amorphous semiconductors has been observed for the glass system. The compositional dependence of dielectric behavior has also been observed.

  6. Electronically Reconfigurable Liquid Crystal Based Mm-Wave Polarization Converter

    OpenAIRE

    Doumanis, E.; Goussetis, G.; Dickie, R.; CAHILL, R; Baine, P; Bain, M; V. Fusco; Encinar, J. A.; Toso, G

    2014-01-01

    An electronically tunable reflection polarizer which exploits the dielectric anisotropy of nematic liquid crystals (LC) has been designed, fabricated and measured in a frequency band centered at 130 GHz. The phase agile polarizing mirror converts an incident slant 45° signal upon reflection to right hand circular (RHCP), orthogonal linear (-45 °) or left hand circular (LHCP) polarization depending on the value of the voltage biasing the LC mixture. In the experimental set-up this is achieved ...

  7. Graphene-based magnetless converter of terahertz wave polarization

    Science.gov (United States)

    Melnikova, Veronica S.; Polischuk, Olga V.; Popov, Vyacheslav V.

    2016-04-01

    The polarization conversion of terahertz radiation by the periodic array of graphene nanoribbons located at the surface of a high-refractive-index dielectric substrate (terahertz prism) is studied theoretically. Giant polarization conversion at the plasmon resonance frequencies takes place without applying external DC magnetic field. It is shown that the total polarization conversion can be reached at the total internal reflection of THz wave from the periodic array of graphene nanoribbons even at room temperature.

  8. Scanning nonlinear dielectric potentiometry

    Energy Technology Data Exchange (ETDEWEB)

    Yamasue, Kohei, E-mail: yamasue@riec.tohoku.ac.jp; Cho, Yasuo [Research Institute of Electrical Communication, Tohoku University, 2-1-1, Katahira, Aoba, Sendai 980-8577 (Japan)

    2015-09-15

    Measuring spontaneous polarization and permanent dipoles on surfaces and interfaces on the nanoscale is difficult because the induced electrostatic fields and potentials are often influenced by other phenomena such as the existence of monopole fixed charges, screening charges, and contact potential differences. A method based on tip-sample capacitance detection and bias feedback is proposed which is only sensitive to polarization- or dipole-induced potentials, unlike Kelvin probe force microscopy. The feasibility of this method was demonstrated by simultaneously measuring topography and polarization-induced potentials on a reconstructed Si(111)-(7 × 7) surface with atomic resolution.

  9. Scanning nonlinear dielectric potentiometry.

    Science.gov (United States)

    Yamasue, Kohei; Cho, Yasuo

    2015-09-01

    Measuring spontaneous polarization and permanent dipoles on surfaces and interfaces on the nanoscale is difficult because the induced electrostatic fields and potentials are often influenced by other phenomena such as the existence of monopole fixed charges, screening charges, and contact potential differences. A method based on tip-sample capacitance detection and bias feedback is proposed which is only sensitive to polarization- or dipole-induced potentials, unlike Kelvin probe force microscopy. The feasibility of this method was demonstrated by simultaneously measuring topography and polarization-induced potentials on a reconstructed Si(111)-(7 × 7) surface with atomic resolution. PMID:26429445

  10. Improvements of dielectric properties of Cu doped LaTiO3+δ

    Directory of Open Access Journals (Sweden)

    Yan Chen

    2016-04-01

    Full Text Available The ceramic composites of Cu-doped La1−xCuxTiO3+δ (x=0.05, 0.15, 0.3, 0.5 were synthesized by conventional solid-state reaction. The complex dielectric properties of the composites were investigated as a function of temperature (77 K≤T≤320 K and frequency (100 Hz≤f≤1 MHz separately. In all composites, the dielectric constants increase monotonously and the dielectric loss undulates with temperature. And it is clearly observed that extraordinarily high low-frequency dielectric constant (~104 appear at room temperature in La0.5Cu0.5TiO3+δ, which is ~100 times larger than that of La0.95Cu0.05TiO3+δ. Interestingly, the dielectric constants increase remarkably with the doped Cu contents, meanwhile the dielectric loss for all samples is ideal lower than 1 at room temperature in the measured frequency range. By means of complex impedance analysis, the improvements of dielectric properties are attributed to both bulk contribution and grain boundary effect, in which the bulk polaronic relaxation and the Maxwell–Wagner relaxation due to grain boundary response are heightened remarkably with the high doped Cu contents.

  11. Communication: Linking the dielectric Debye process in mono-alcohols to density fluctuations.

    Science.gov (United States)

    Hecksher, Tina

    2016-04-28

    This work provides the first direct evidence that the puzzling dielectric Debye process observed in mono-alcohols is coupled to density fluctuations. The results open up for an explanation of the Debye process within the framework of conventional liquid-state theory. The spectral shape of the dynamical bulk modulus of the two studied mono-alcohols, 2-ethyl-1-hexanol and 4-methyl-3-heptanol, is nearly identical to that of their corresponding shear modulus, and thus the supramolecular structures believed to be responsible for the slow dielectric Debye process are manifested in the bulk modulus in the same way as in the shear modulus. PMID:27131521

  12. Communication: Linking the dielectric Debye process in mono-alcohols to density fluctuations

    Science.gov (United States)

    Hecksher, Tina

    2016-04-01

    This work provides the first direct evidence that the puzzling dielectric Debye process observed in mono-alcohols is coupled to density fluctuations. The results open up for an explanation of the Debye process within the framework of conventional liquid-state theory. The spectral shape of the dynamical bulk modulus of the two studied mono-alcohols, 2-ethyl-1-hexanol and 4-methyl-3-heptanol, is nearly identical to that of their corresponding shear modulus, and thus the supramolecular structures believed to be responsible for the slow dielectric Debye process are manifested in the bulk modulus in the same way as in the shear modulus.

  13. Additive manufacturing of graded dielectrics

    International Nuclear Information System (INIS)

    A method for the fabrication of graded dielectrics within a structural composite is presented. This system employs an ultrasonic powder deposition head to print high dielectric powders onto a woven fabric composite substrate. It is shown how this system can integrate 3D variations of dielectric properties at millimeter resolution within a mechanically rugged substrate. To conclude, the system’s practical application is demonstrated with experimental results from a graded index lens. (paper)

  14. Oscillatory Dynamical Switching System of Bulk Ferroelectrics

    Directory of Open Access Journals (Sweden)

    M. N.A. Halif

    2005-01-01

    Full Text Available This study gives a detailed account of calculation of the bulk ferroelectric (FE oscillatory dynamical system switching to first and second-order phase transition, respectively. All the formalism is delineated in the framework of Landau free-energy expansion and Landau-Khalatnikov (LK equation of motion where the effect of external energy may affray FE atoms similar to the spring damped oscillatory system. Here we scrutinized the switching properties from free-energy expansion and hysteresis loop. The polarization and current switching appropriate to the estimated complete switching time, changing of temperature, electric field and damping are scrutinized and discussed.

  15. Dielectric relaxation in solid collagen over a wide temperature range

    International Nuclear Information System (INIS)

    Dielectric constant ε' and loss factor ε'' have been measured in bovine tendon collagen in the frequency range 30 Hz - 3 MHz and temperature range 30 deg. C to 200 deg. C. Frequency dependence curve of ε'' shows a low frequency strong α-dispersion attributed to phonon assisted proton hopping between localized sites and a weak high frequency. α2 - dispersion attributed to reorientation of polar components of collagen molecules. Temperature dependence of the dielectric data show release of bound moisture as a three step process with discrete peaks at 50 deg. C, 90 deg. C and 125 deg. C. These peaks have been attributed to release of adsorbed surface water, water bound to exposed polar sites and strongly bound internal moisture respectively. A peak observed at 160 deg. C has been attributed to thermally induced helix-coil transition of collagen molecules. (author)

  16. Polaron-electron assisted giant dielectric dispersion in SrZrO3 high-k dielectric

    Science.gov (United States)

    Borkar, Hitesh; Barvat, Arun; Pal, Prabir; Shukla, A. K.; Pulikkotil, J. J.; Kumar, Ashok

    2016-06-01

    The SrZrO3 is a well known high-k dielectric constant (˜22) and high optical bandgap (˜5.8 eV) material and one of the potential candidates for future generation nanoelectronic logic elements (8 nm node technology) beyond silicon. Its dielectric behavior is fairly robust and frequency independent till 470 K; however, it suffers a strong small-polaron based electronic phase transition (Te) linking 650 to 750 K. The impedance spectroscopy measurements revealed the presence of conducting grains and grain boundaries at elevated temperature which provide energetic mobile charge carriers with activation energy in the range of 0.7 to 1.2 eV supporting the oxygen ions and proton conduction. X-ray photoemission spectroscopy measurements suggest the presence of weak non-stoichiometric O2- anions and hydroxyl species bound to different sites at the surface and bulk. These thermally activated charge carriers at elevated temperature significantly contribute to the polaronic based dielectric anomaly and conductivity. Our dielectric anomaly supports pseudo phase transition due to high degree of change in ZrO6 octahedral angle in the temperature range of 650-750 K, where electron density and phonon vibration affect the dielectric and conductivity properties.

  17. Origin of dielectric tunability in DNA-CTMA film at microwave frequencies

    Science.gov (United States)

    Aga, Roberto S., Jr.; Bartsch, Carrie M.; Telek, Brian A.; Subramanyam, Guru; Heckman, Emily M.; Grote, James G.

    2011-09-01

    DNA-CTMA is an attractive material to explore for reconfigurable optical and electronic devices. Its dielectric constant at microwave frequencies can be tuned by applying a DC electric field. In this work, the origin of dielectric tunability and other ferroelectric-like behavior observed in DNA-CTMA films is investigated. Results suggest that the dominant polarization mechanism is ionic in nature and is caused by intentionally retaining excess ions in the DNA-CTMA precipitate during processing.

  18. Dynamic Heterogeneous Dielectric Generalized Born (DHDGB): An implicit membrane model with a dynamically varying bilayer thickness

    OpenAIRE

    Panahi, Afra; Feig, Michael

    2013-01-01

    An extension to the heterogeneous dielectric generalized Born (HDGB) implicit membrane formalism is presented to allow dynamic membrane deformations in response to membrane-inserted biomolecules during molecular dynamic simulations. The flexible membrane is implemented through additional degrees of freedom that represent the membrane deformation at the contact points of a membrane-inserted solute with the membrane. The extra degrees of freedom determine the dielectric and non-polar solvation ...

  19. Ferroelectric polymer networks with high energy density and improved discharged efficiency for dielectric energy storage.

    Science.gov (United States)

    Khanchaitit, Paisan; Han, Kuo; Gadinski, Matthew R; Li, Qi; Wang, Qing

    2013-01-01

    Ferroelectric polymers are being actively explored as dielectric materials for electrical energy storage applications. However, their high dielectric constants and outstanding energy densities are accompanied by large dielectric loss due to ferroelectric hysteresis and electrical conduction, resulting in poor charge-discharge efficiencies under high electric fields. To address this long-standing problem, here we report the ferroelectric polymer networks exhibiting significantly reduced dielectric loss, superior polarization and greatly improved breakdown strength and reliability, while maintaining their fast discharge capability at a rate of microseconds. These concurrent improvements lead to unprecedented charge-discharge efficiencies and large values of the discharged energy density and also enable the operation of the ferroelectric polymers at elevated temperatures, which clearly outperforms the melt-extruded ferroelectric polymer films that represents the state of the art in dielectric polymers. The simplicity and scalability of the described method further suggest their potential for high energy density capacitors. PMID:24276519

  20. Problems in the theory of the thermal Casimir force between dielectrics and semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Klimchitskaya, G L; Geyer, B [Center of Theoretical Studies and Institute for Theoretical Physics, Leipzig University, D-04009, Leipzig (Germany)

    2008-04-25

    The application of the Lifshitz theory to describe the thermal Casimir force between dielectrics and semiconductors is considered. It is shown that for all true dielectrics (i.e., for all materials having zero conductivity at zero temperature) the inclusion of a nonzero conductivity arising at nonzero temperature into the model of dielectric response leads to the violation of the Nernst heat theorem. This result refers equally to simple insulators, intrinsic semiconductors, Mott-Hubbard dielectrics and doped semiconductors with doping concentration below a critical value. We demonstrate that in the insulator-metal transition the Casimir free energy changes abruptly irrespective of whether the conductivity changes continuously or discontinuously. The application of the Lifshitz formula to polar dielectrics results in a large thermal correction that is linear in temperature. A rule is formulated on how to apply the Lifshitz theory to real materials in agreement with thermodynamics and experiment.

  1. Spin dynamics in bulk CdTe at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Nahalkova, P. [Faculty of Mathematics and Physics, Charles University in Prague, Ke Karlovu 3, 121 16 Prague 2 (Czech Republic); Nemec, P. [Faculty of Mathematics and Physics, Charles University in Prague, Ke Karlovu 3, 121 16 Prague 2 (Czech Republic)]. E-mail: nemec@karlov.mff.cuni.cz; Sprinzl, D. [Faculty of Mathematics and Physics, Charles University in Prague, Ke Karlovu 3, 121 16 Prague 2 (Czech Republic); Belas, E. [Faculty of Mathematics and Physics, Charles University in Prague, Ke Karlovu 3, 121 16 Prague 2 (Czech Republic); Horodysky, P. [Faculty of Mathematics and Physics, Charles University in Prague, Ke Karlovu 3, 121 16 Prague 2 (Czech Republic); Franc, J. [Faculty of Mathematics and Physics, Charles University in Prague, Ke Karlovu 3, 121 16 Prague 2 (Czech Republic); Hlidek, P. [Faculty of Mathematics and Physics, Charles University in Prague, Ke Karlovu 3, 121 16 Prague 2 (Czech Republic); Maly, P. [Faculty of Mathematics and Physics, Charles University in Prague, Ke Karlovu 3, 121 16 Prague 2 (Czech Republic)

    2006-01-25

    In this paper, we report on the room temperature dynamics of spin-polarized carriers in undoped bulk CdTe. Platelets of CdTe with different concentration of preparation-induced dislocations were prepared by combining the mechanical polishing and chemical etching. Using the polarization-resolved pump-probe experiment in transmission geometry, we have observed a systematic decrease of both the signal polarization and the electron spin dephasing time (from 52 to 36 ps) with the increased concentration of defects. We have suggested that the Elliot-Yafet mechanism might be the dominant spin dephasing mechanism in platelets of CdTe at room temperature.

  2. Spin dynamics in bulk CdTe at room temperature

    International Nuclear Information System (INIS)

    In this paper, we report on the room temperature dynamics of spin-polarized carriers in undoped bulk CdTe. Platelets of CdTe with different concentration of preparation-induced dislocations were prepared by combining the mechanical polishing and chemical etching. Using the polarization-resolved pump-probe experiment in transmission geometry, we have observed a systematic decrease of both the signal polarization and the electron spin dephasing time (from 52 to 36 ps) with the increased concentration of defects. We have suggested that the Elliot-Yafet mechanism might be the dominant spin dephasing mechanism in platelets of CdTe at room temperature

  3. Polarization holography

    DEFF Research Database (Denmark)

    Nikolova, L.; Ramanujam, P.S.

    Current research into holography is concerned with applications in optically storing, retrieving, and processing information. Polarization holography has many unique properties compared to conventional holography. It gives results in high efficiency, achromaticity, and special polarization...... properties. This books reviews the research carried out in this field over the last 15 years. The authors provide basic concepts in polarization and the propagation of light through anisotropic materials, before presenting a sound theoretical basis for polarization holography. The fabrication and...... characterization of azobenzene based materials, which remain the most efficient for the purpose, is described in detail. This is followed by a description of other materials that are used in polarization holography. An in-depth description of various applications, including display holography and optical storage...

  4. Dielectric Behaviour of Binary Mixture of 2-Chloroaniline with 2-Methoxyethanol and 2-Ethoxyethanol

    Directory of Open Access Journals (Sweden)

    Bhupesh G. Nemmaniwar

    2013-05-01

    Full Text Available Densities, viscosities, refractive indices, dielectric constant (ε' and dielectric loss (ε'' of 2-chloroaniline (2CA + 2-methoxyethanol (2ME and 2-chloroaniline (2CA + 2-ethoxyethanol (2EE for different mole fractions of 2-chloroaniline in binary mixture have been measured at single microwave frequency 10.985 GHz at 300C by Surber method using microwave X-band. The values of dielectric parameters (ε' and ε''   have been used to evaluate the molar polarization (P12 loss tangent (tanδ, viscosity (η, activation energy (Ea, excess permittivity (Δε', excess dielectric loss (Δε'', excess viscosities (Δη, excess polarization (ΔP12 and excess activation energy (ΔEa  have also been estimated. These parameters have been used to explain the formation of complexes in the system. It is found that dielectric constant (ε', dielectric loss (ε'', loss tangent (tanδ, molar polarization (P12 varies non-linearly but activation energy (Ea , viscosity (η ,density (ρ, and refractive index (n varies linearly with increasing mole fraction in binary mixture of 2-chloroaniline (2-CA + 2-methoxyethanol (2-ME and 2-chloroaniline (2-CA + 2-ethoxyethanol (2-EE. Hence, solute-solvent molecular associations have been reported. 

  5. Dielectric Behaviour of Binary Mixture of 2-Chloroaniline with 2-Methoxyethanol and 2-Ethoxyethanol

    OpenAIRE

    Bhupesh G Nemmaniwar; Kalyankar, Namdeo V.; Pothaji L. Kadam

    2013-01-01

    Densities, viscosities, refractive indices, dielectric constant (ε') and dielectric loss (ε'') of 2-chloroaniline (2CA) + 2-methoxyethanol (2ME) and 2-chloroaniline (2CA) + 2-ethoxyethanol (2EE) for different mole fractions of 2-chloroaniline in binary mixture have been measured at single microwave frequency 10.985 GHz at 300C by Surber method using microwave X-band. The values of dielectric parameters (ε' and ε'' )  have been used to evaluate the molar polarization (P12) loss tangent (tanδ),...

  6. Dielectric Behavior of Binary Mixture of 2, 3-Dichloroaniline with 2-Methoxyethanol at 200 C

    OpenAIRE

    Bhupesh G Nemmaniwar; Vijaykumar Panchal; Potaji Kadam

    2014-01-01

    Densities, viscosities, refractive indices, dielectric constant (ɛ`) and dielectric loss (ɛ``) of 2,3-Dichloroaniline (2,3-DCA) and 2-methoxyethanol (2-ME) for different mole fractions of 2,3-Dichloroaniline in binary mixture have been measured at single microwave frequency 10.985 GHz at 200C by Surber method at microwave X-band. The values of dielectric parameters (ɛ`and ɛ``) have been used to evaluate the molar polarization (P12) and loss tangent (tan δ) excess permittivity (Δɛ``), exces...

  7. Variational principles and governing equations in nano-dielectrics with the flexoelectric effect

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The flexoelectric effect is very strong and coupled with large strain gradients for nanoscale dielectrics. At the nanoscale, the electrostatic force cannot be ignored. In this paper, we have established the electric enthalpy variational principle for nanosized dielectrics with the strain gradient and the polarization gradient effect, as well as the effect of the electrostatic force. The complete governing equations, which include the effect of the electrostatic force, are derived from this variational principle, and based on the principle the generalized electrostatic stress is obtained, the generalized electrostatic stress contains the Maxwell stress corresponding to the polarization and strain, and stress related to the polarization gradient and strain gradient. This work provides the basis for the analysis and computations for the electromechanical problems in nanosized dielectric materials.

  8. Boron nitride as two dimensional dielectric: Reliability and dielectric breakdown

    International Nuclear Information System (INIS)

    Boron Nitride (BN) is a two dimensional insulator with excellent chemical, thermal, mechanical, and optical properties, which make it especially attractive for logic device applications. Nevertheless, its insulating properties and reliability as a dielectric material have never been analyzed in-depth. Here, we present the first thorough characterization of BN as dielectric film using nanoscale and device level experiments complementing with theoretical study. Our results reveal that BN is extremely stable against voltage stress, and it does not show the reliability problems related to conventional dielectrics like HfO2, such as charge trapping and detrapping, stress induced leakage current, and untimely dielectric breakdown. Moreover, we observe a unique layer-by-layer dielectric breakdown, both at the nanoscale and device level. These findings may be of interest for many materials scientists and could open a new pathway towards two dimensional logic device applications

  9. Boron nitride as two dimensional dielectric: Reliability and dielectric breakdown

    Energy Technology Data Exchange (ETDEWEB)

    Ji, Yanfeng; Pan, Chengbin; Hui, Fei; Shi, Yuanyuan; Lanza, Mario, E-mail: mlanza@suda.edu.cn [Institute of Functional Nano and Soft Materials, Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, 199 Ren-Ai Road, Suzhou 215123 (China); Zhang, Meiyun; Long, Shibing [Key Laboratory of Microelectronics Devices & Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029 (China); Lian, Xiaojuan; Miao, Feng [National Laboratory of Solid State Microstructures, School of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China); Larcher, Luca [DISMI, Università di Modena e Reggio Emilia, 42122 Reggio Emilia (Italy); Wu, Ernest [IBM Research Division, Essex Junction, Vermont 05452 (United States)

    2016-01-04

    Boron Nitride (BN) is a two dimensional insulator with excellent chemical, thermal, mechanical, and optical properties, which make it especially attractive for logic device applications. Nevertheless, its insulating properties and reliability as a dielectric material have never been analyzed in-depth. Here, we present the first thorough characterization of BN as dielectric film using nanoscale and device level experiments complementing with theoretical study. Our results reveal that BN is extremely stable against voltage stress, and it does not show the reliability problems related to conventional dielectrics like HfO{sub 2}, such as charge trapping and detrapping, stress induced leakage current, and untimely dielectric breakdown. Moreover, we observe a unique layer-by-layer dielectric breakdown, both at the nanoscale and device level. These findings may be of interest for many materials scientists and could open a new pathway towards two dimensional logic device applications.

  10. Wormholes in Bulk Viscous Cosmology

    OpenAIRE

    Jamil, Mubasher

    2008-01-01

    We investigate the effects of the accretion of phantom energy with non-zero bulk viscosity onto a Morris-Thorne wormhole. We have found that if the bulk viscosity is large then the mass of wormhole increases rapidly as compared to small or zero bulk viscosity.

  11. Polarized electroproduction

    International Nuclear Information System (INIS)

    A new type of information on proton structure, its internal spin structure, has recently become available from a new type of experiment, polarized electroproduction. The scattering of longitudinally polarized electrons was measured by longitudinally polarized protons. The quantity measured was the asymmetry A, the normalized difference between the differential scattering cross sections for the antiparallel and parallel spin configurations. Data have been obtained for elastic, deep inelastic, and reasonance region scattering. Polarized electrons were obtained by the photoionization of polarized Li atomic beam with pulsed UV light. The important characteristics of the polarized electron beam are the intensity of 109 e-/1.5 μs pulse at repetition rate of 120 pps, and polarization of 0.85 +- 0.08. A number of data on deep inelastic scattering, preliminary asymmetry in the resonance region and others are described and illustrated in several graphs. There are several implications in these data; 1) test of Bjorken sum rule, 2) scaling, and 3) models of proton structure, which are mentioned hereinafter. The Bjorken sum rule predicts equality in the scaling limit between an integral over ω of the product of spin-averaged nucleon structure function W2 and spin dependent function A, and the ratio of axial vector to vector weak coupling constants of beta decay. Data on the asymmetries in deep inelastic and resonance region scattering will make possible the evaluation of a famous old problem -- the effect of proton polarizability on the hyperfine structure interval in hydrogen. (Wakatsuki, Y.)

  12. Treatment of polycarbonate by dielectric barrier discharge (DBD) at atmospheric pressure

    Science.gov (United States)

    Kostov, K. G.; Hamia, Y. A. A.; Mota, R. P.; dos Santos, A. L. R.; Nascente, P. A. P.

    2014-05-01

    Generally most plastic materials are intrinsically hydrophobic, low surface energy materials, and thus do not adhere well to other substances. Surface treatment of polymers by discharge plasmas is of great and increasing industrial application because it can uniformly modify the surface of sample without changing the material bulk properties and is environmentally friendly. The plasma processes that can be conducted under ambient pressure and temperature conditions have attracted special attention because of their easy implementation in industrial processing. Present work deals with surface modification of polycarbonate (PC) by a dielectric barrier discharge (DBD) at atmospheric pressure. The treatment was performed in a parallel plate reactor driven by a 60Hz power supply. The DBD plasmas at atmospheric pressure were generated in air and nitrogen. Material characterization was carried out by contact angle measurements, and X-ray photoelectron spectroscopy (XPS). The surface energy of the polymer surface was calculated from contact angle data by Owens-Wendt method using distilled water and diiodomethane as test liquids. The plasma-induced chemical modifications are associated with incorporation of polar oxygen and nitrogen containing groups on the polymer surface. Due to these surface modifications the DBD-treated polymers become more hydrophilic. Aging behavior of the treated samples revealed that the polymer surfaces were prone to hydrophobic recovery although they did not completely recover their original wetting properties.

  13. Effects of porous carbon additives and induced fluorine on low dielectric constant polyimide synthesized with an e-beam

    International Nuclear Information System (INIS)

    We report the synthesis of a polyimide matrix with a low dielectric constant for application as an intercalation material between metal interconnections in electronic devices. Porous activated carbon was embedded in the polyimide to reduce the dielectric constant, and a thin film of the complex was obtained using the spin-coating and e-beam irradiation methods. The surface of the thin film was modified with fluorine functional groups to impart water resistance and reduce the dielectric constant further. The water resistance was significantly improved by the modification with hydrophobic fluorine groups. The dielectric constant was effectively decreased by porous activated carbon. The fluorine modification also resulted in a low dielectric constant on the polyimide surface by reducing the polar surface free energy. The dielectric constant of polyimide film decreased from 2.98 to 1.9 by effects of porous activated carbon additive and fluorine surface modification.

  14. Dielectric laser accelerators

    Science.gov (United States)

    England, R. Joel; Noble, Robert J.; Bane, Karl; Dowell, David H.; Ng, Cho-Kuen; Spencer, James E.; Tantawi, Sami; Wu, Ziran; Byer, Robert L.; Peralta, Edgar; Soong, Ken; Chang, Chia-Ming; Montazeri, Behnam; Wolf, Stephen J.; Cowan, Benjamin; Dawson, Jay; Gai, Wei; Hommelhoff, Peter; Huang, Yen-Chieh; Jing, Chunguang; McGuinness, Christopher; Palmer, Robert B.; Naranjo, Brian; Rosenzweig, James; Travish, Gil; Mizrahi, Amit; Schachter, Levi; Sears, Christopher; Werner, Gregory R.; Yoder, Rodney B.

    2014-10-01

    The use of infrared lasers to power optical-scale lithographically fabricated particle accelerators is a developing area of research that has garnered increasing interest in recent years. The physics and technology of this approach is reviewed, which is referred to as dielectric laser acceleration (DLA). In the DLA scheme operating at typical laser pulse lengths of 0.1 to 1 ps, the laser damage fluences for robust dielectric materials correspond to peak surface electric fields in the GV /m regime. The corresponding accelerating field enhancement represents a potential reduction in active length of the accelerator between 1 and 2 orders of magnitude. Power sources for DLA-based accelerators (lasers) are less costly than microwave sources (klystrons) for equivalent average power levels due to wider availability and private sector investment. Because of the high laser-to-particle coupling efficiency, required pulse energies are consistent with tabletop microJoule class lasers. Combined with the very high (MHz) repetition rates these lasers can provide, the DLA approach appears promising for a variety of applications, including future high-energy physics colliders, compact light sources, and portable medical scanners and radiative therapy machines.

  15. Dielectric Actuation of Polymers

    Science.gov (United States)

    Niu, Xiaofan

    Dielectric polymers are widely used in a plurality of applications, such as electrical insulation, dielectric capacitors, and electromechanical actuators. Dielectric polymers with large strain deformations under an electric field are named dielectric elastomers (DE), because of their relative low modulus, high elongation at break, and outstanding resilience. Dielectric elastomer actuators (DEA) are superior to traditional transducers as a muscle-like technology: large strains, high energy densities, high coupling efficiency, quiet operation, and light weight. One focus of this dissertation is on the design of DE materials with high performance and easy processing. UV radiation curing of reactive species is studied as a generic synthesis methodology to provide a platform for material scientists to customize their own DE materials. Oligomers/monomers, crosslinkers, and other additives are mixed and cured at appropriate ratios to control the stress-strain response, suppress electromechanical instability of the resulting polymers, and provide stable actuation strains larger than 100% and energy densities higher than 1 J/g. The processing is largely simplified in the new material system by removal of the prestretching step. Multilayer stack actuators with 11% linear strain are demonstrated in a procedure fully compatible with industrial production. A multifunctional DE derivative material, bistable electroactive polymer (BSEP), is invented enabling repeatable rigid-to-rigid deformation without bulky external structures. Bistable actuation allows the polymer actuator to have two distinct states that can support external load without device failure. Plasticizers are used to lower the glass transition temperature to 45 °C. Interpenetrating polymer network structure is established inside the BSEP to suppress electromechanical instability, providing a breakdown field of 194 MV/m and a stable bistable strain as large as 228% with a 97% strain fixity. The application of BSEP

  16. Substantial bulk photovoltaic effect enhancement via nanolayering.

    Science.gov (United States)

    Wang, Fenggong; Young, Steve M; Zheng, Fan; Grinberg, Ilya; Rappe, Andrew M

    2016-01-01

    Spontaneous polarization and inversion symmetry breaking in ferroelectric materials lead to their use as photovoltaic devices. However, further advancement of their applications are hindered by the paucity of ways of reducing bandgaps and enhancing photocurrent. By unravelling the correlation between ferroelectric materials' responses to solar irradiation and their local structure and electric polarization landscapes, here we show from first principles that substantial bulk photovoltaic effect enhancement can be achieved by nanolayering PbTiO3 with nickel ions and oxygen vacancies ((PbNiO2)x(PbTiO3)(1-x)). The enhancement of the total photocurrent for different spacings between the Ni-containing layers can be as high as 43 times due to a smaller bandgap and photocurrent direction alignment for all absorption energies. This is due to the electrostatic effect that arises from nanolayering. This opens up the possibility for control of the bulk photovoltaic effect in ferroelectric materials by nanoscale engineering of their structure and composition. PMID:26791545

  17. Ferroelectric properties of bulk and thin films of PMNT system

    International Nuclear Information System (INIS)

    Perovskite phase development study for bulk and thin films of PMNT 68/32 composition was carried out. B-site Columbite precursor technique was used for bulk system preparation whereas, sol-gel technique was used for thin film deposition on ITO coated glass substrates. Approximately 100% and 95% perovskite phase with grains of micron and sub-micron sizes were observed in bulk and thin films, respectively. Curie transition temperature, T c, for bulk and thin films were ∼150 deg. C and 190 deg. C, respectively. Polarization vs. electric field, P-E, hysteresis loops of PMNT 68/32 bulk and thin films showed remnant polarization, P r, ∼21.67 μC/cm2 and 1.1 μC/cm2 and coercive fields, E c, ∼3.9 and 7.7 kV/cm, respectively. Strain vs. electric field, S-E, behavior of PMNT 68/32 bulk ceramic showed piezoelectric nature of the material with a high value of maximum strain ∼1% at 19 kV/cm

  18. Creating bulk nanocrystalline metal.

    Energy Technology Data Exchange (ETDEWEB)

    Fredenburg, D. Anthony (Georgia Institute of Technology, Atlanta, GA); Saldana, Christopher J. (Purdue University, West Lafayette, IN); Gill, David D.; Hall, Aaron Christopher; Roemer, Timothy John (Ktech Corporation, Albuquerque, NM); Vogler, Tracy John; Yang, Pin

    2008-10-01

    Nanocrystalline and nanostructured materials offer unique microstructure-dependent properties that are superior to coarse-grained materials. These materials have been shown to have very high hardness, strength, and wear resistance. However, most current methods of producing nanostructured materials in weapons-relevant materials create powdered metal that must be consolidated into bulk form to be useful. Conventional consolidation methods are not appropriate due to the need to maintain the nanocrystalline structure. This research investigated new ways of creating nanocrystalline material, new methods of consolidating nanocrystalline material, and an analysis of these different methods of creation and consolidation to evaluate their applicability to mesoscale weapons applications where part features are often under 100 {micro}m wide and the material's microstructure must be very small to give homogeneous properties across the feature.

  19. Explosive bulk charge

    Science.gov (United States)

    Miller, Jacob Lee

    2015-04-21

    An explosive bulk charge, including: a first contact surface configured to be selectively disposed substantially adjacent to a structure or material; a second end surface configured to selectively receive a detonator; and a curvilinear side surface joining the first contact surface and the second end surface. The first contact surface, the second end surface, and the curvilinear side surface form a bi-truncated hemispherical structure. The first contact surface, the second end surface, and the curvilinear side surface are formed from an explosive material. Optionally, the first contact surface and the second end surface each have a substantially circular shape. Optionally, the first contact surface and the second end surface consist of planar structures that are aligned substantially parallel or slightly tilted with respect to one another. The curvilinear side surface has one of a smooth curved geometry, an elliptical geometry, and a parabolic geometry.

  20. The Incredible Bulk

    CERN Document Server

    Fukushima, Keita; Kumar, Jason; Sandick, Pearl; Yamamoto, Takahiro

    2014-01-01

    Recent experimental results from the LHC have placed strong constraints on the masses of colored superpartners. The MSSM parameter space is also constrained by the measurement of the Higgs boson mass, and the requirement that the relic density of lightest neutralinos be consistent with observations. Although large regions of the MSSM parameter space can be excluded by these combined bounds, leptophilic versions of the MSSM can survive these constraints. In this paper we consider a scenario in which the requirements of minimal flavor violation, vanishing $CP$-violation, and mass universality are relaxed, specifically focusing on scenarios with light sleptons. We find a large region of parameter space, analogous to the original bulk region, for which the lightest neutralino is a thermal relic with an abundance consistent with that of dark matter. We find that these leptophilic models are constrained by measurements of the magnetic and electric dipole moments of the electron and muon, and that these models have ...

  1. Bulk muscles, loose cables.

    Science.gov (United States)

    Liyanage, Chamari R D G; Kodali, Venkata

    2014-01-01

    The accessibility and usage of body building supplements is on the rise with stronger internet marketing strategies by the industry. The dangers posed by the ingredients in them are underestimated. A healthy young man came to the emergency room with palpitations and feeling unwell. Initial history and clinical examination were non-contributory to find the cause. ECG showed atrial fibrillation. A detailed history for any over the counter or herbal medicine use confirmed that he was taking supplements to bulk muscle. One of the components in these supplements is yohimbine; the onset of symptoms coincided with the ingestion of this product and the patient is symptom free after stopping it. This report highlights the dangers to the public of consuming over the counter products with unknown ingredients and the consequential detrimental impact on health. PMID:25326558

  2. Thermally stimulated discharge current (TSDC) and dielectric constant of semiconducting glasses

    Indian Academy of Sciences (India)

    D K Burghate; V S Deogaonkar; S B Sawarkar; S P Yawale; S V Pakade

    2003-02-01

    In this paper the results of thermally stimulated discharge current (TSDC) and dielectric constant for 40PbO–60Bi2O3 glass thermoelectrets are presented. Measurements of TSDC and dielectric constant, $\\varepsilon'$, have been carried out in the temperature range 30–300°C. The thermoelectrets were prepared at different polarizing fields. The various observed peaks in the thermograms are discussed on the basis of space charge polarization. The trap energy is evaluated from the Garlick–Gibson plot of initial rise method. Similarly other parameters such as relaxation time, charge release etc are evaluated.

  3. Lattice dynamics and dielectric spectroscopy of BZT and NBT lead-free perovskite relaxors - comparison with lead-based relaxors

    Czech Academy of Sciences Publication Activity Database

    Petzelt, Jan; Nuzhnyy, Dmitry; Bovtun, Viktor; Kempa, Martin; Savinov, Maxim; Kamba, Stanislav; Hlinka, Jiří

    2015-01-01

    Roč. 88, č. 3 (2015), 320-332. ISSN 0141-1594 R&D Projects: GA ČR GA13-15110S Institutional support: RVO:68378271 Keywords : relaxor ferroelectrics * polar phonons * polar nanoregions * dielectric spectroscopy * off-centred ions Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.954, year: 2014

  4. RF and microwave dielectric properties of stored-grain insects and their implications for potential insect control

    International Nuclear Information System (INIS)

    The permittivities of bulk samples of adult insects of the rice weevil, red flour beetle, sawtoothed grain beetle, and lesser grain borer were measured at single frequencies of 9.4 and 11.7 Ghz in X-band waveguide at about 23 degrees C, and permittivities of homogenized samples of the same species were measured from 0.2 to 20 GHz at temperatures from 10 to 70 degrees C with an open-ended coaxial-line probe and network analyzer. Sample densities for the coaxial-line probe measurements were determined from the X-band measurements with a linear relationship between the cube root of the dielectric constant and sample bulk density determined from permittivity measurements on bulk samples of the adult insects in a waveguide sample holder taken with the short-circuited line technique. Since linearity of the cube root of the dielectric constant with bulk density is consistent with the Landau and Lifshitz, Looyenga dielectric mixture equation, this equation was used to calculate estimated dielectric constants and loss factors of the insects from measured permittivities and volume fractions determined from measured bulk density and adult insect density determined by air-comparison pycnometer measurements. Estimated dielectric constants and loss factors of the insects are presented graphically for temperatures from 10 to 70 degrees C, and tabulated data are provided for range information and comparative purposes

  5. Anomalous optical nonlinearity of dielectric nanodispersions

    Science.gov (United States)

    Milichko, V. A.; Dzyuba, V. P.; Kul'chin, Yurii N.

    2013-06-01

    We present the results of studying the nonlinear optical response of nanodispersions of semiconductor (TiO2, ZnO) and dielectric (SiO2, Al2O3) nanoparticles of spherical, spheroidal and flake shape, suspended in polar and nonpolar dielectric matrices (water, isopropanol, polymethylsiloxane and transformer oil) by means of z-scanning in the field of low-intensity visible laser radiation. It is found that, unlike semiconductor nanoparticles and particles of spherical shape, flake-shaped SiO2 and Al2O3 nanoparticles suspended in nonpolar matrices exhibit nonlinear optical response within the intensity interval from 0 to 500 W cm-2 that vanishes at higher intensities. The diagrams of energy states of the optical electrons in nanoparticles that allow explanation of differences in the nonlinear-optical properties of nanodispersions are proposed. Good agreement between the experimental and theoretical dependences of nonlinear refractive indices and absorption coefficients on the intensity of radiation is observed.

  6. Investigation of correlation between dielectric parameters and nanostructures in aqueous solution grown poly(vinyl alcohol-montmorillonite clay nanocomposites by dielectric relaxation spectroscopy

    Directory of Open Access Journals (Sweden)

    2010-09-01

    Full Text Available Poly(vinyl alcohol (PVA-montmorillonite (MMT clay nanocomposite films up to 10 wt% clay concentration were synthesized by aqueous solution grown technique. The relative complex dielectric function, alternating current electrical conductivity, electric modulus and impedance properties of these organic-inorganic nanocomposites were investigated in the frequency range from 20 Hz to 1 MHz at ambient temperature. The PVA-MMT clay nanocomposite films show a large decrease in the real part and loss of relative dielectric function at 1 wt% MMT clay loading compared to pure PVA film and anomalous behaviour is observed with further increase of clay concentration in PVA matrix. Two dielectric relaxation processes were observed in these nanocomposites; a high frequency relaxation associated with PVA segmental motion and a low frequency relaxation resulting from PVA/dispersed MMT clay interfacial polarization (Maxwell-Wagner relaxation. Dielectric relaxation times corresponding to these processes were determined by fitting dc conductivity corrected complex dielectric function data to the Havriliak-Negami expression. A correlation between change in dielectric relaxation strength, relaxation time and hindrance to the PVA-chain dynamics with the degree of exfoliated structures of dispersed nanoscale MMT clay filler in the PVA matrix were explored. Results confirm the application of dielectric relaxation spectroscopy as a potential tool in the confirmation of nanocomposite formation and their structure characterization.

  7. Highly tunable elastic dielectric metasurface lenses

    CERN Document Server

    Kamali, Seyedeh Mahsa; Arbabi, Amir; Horie, Yu; Faraon, Andrei

    2016-01-01

    Dielectric metasurfaces are two-dimensional structures composed of nano-scatterers that manipulate phase and polarization of optical waves with subwavelength spatial resolution, enabling ultra-thin components for free-space optics. While high performance devices with various functionalities, including some that are difficult to achieve using conventional optical setups have been shown, most demonstrated components have a fixed functionality. Here we demonstrate highly tunable metasurface devices based on subwavelength thick silicon nano-posts encapsulated in a thin transparent elastic polymer. As proof of concept, we demonstrate a metasurface microlens operating at 915 nm, with focal distance tuning from 600 $\\mu$m to 1400 $\\mu$m through radial strain, while maintaining a diffraction limited focus and a focusing efficiency above 50$\\%$. The demonstrated tunable metasurface concept is highly versatile for developing ultra-slim, multi-functional and tunable optical devices with widespread applications ranging f...

  8. Microwave axial dielectric properties of carbon fiber

    Science.gov (United States)

    Hong, Wen; Xiao, Peng; Luo, Heng; Li, Zhuan

    2015-10-01

    Randomly distributed carbon fibers (CFs) reinforced epoxy resin composites are prepared by the pouring method, the dielectric properties of CF composites with different fiber content and length have been performed in the frequency range from 8.2 to 12.4 GHz. The complex permittivity of the composite increases with the fiber length, which is attributed to the decrease of depolarization field, and increases with the volume fraction, which is attributed to the increase of polarization. A formula, based on the theory of Reynolds-Hugh, is proposed to calculate the effective permittivity of CF composites, and validated by the experiments. The proposed formula is further applied to derive the axial permittivity of CF and analyze the effect of fiber length on the axial permittivity.

  9. Poly(methyl methacrylate) as a self-assembled gate dielectric for graphene field-effect transistors

    Science.gov (United States)

    Sanne, A.; Movva, H. C. P.; Kang, S.; McClellan, C.; Corbet, C. M.; Banerjee, S. K.

    2014-02-01

    We investigate poly(methyl methacrylate) (PMMA) as a low thermal budget organic gate dielectric for graphene field effect-transistors (GFETs) based on a simple process flow. We show that high temperature baking steps above the glass transition temperature (˜130 °C) can leave a self-assembled, thin PMMA film on graphene, where we get a gate dielectric almost for "free" without additional atomic layer deposition type steps. Electrical characterization of GFETs with PMMA as a gate dielectric yields a dielectric constant of k = 3.0. GFETs with thinner PMMA dielectrics have a lower dielectric constant due to decreased polarization arising from neutralization of dipoles and charged carriers as baking temperatures increase. The leakage through PMMA gate dielectric increases with decreasing dielectric thickness and increasing electric field. Unlike conventional high-k gate dielectrics, such low-k organic gate dielectrics are potentially attractive for devices such as the proposed Bilayer pseudoSpin Field-Effect Transistor or flexible high speed graphene electronics.

  10. Multilayer optical dielectric coating

    Science.gov (United States)

    Emmett, John L.

    1990-01-01

    A highly damage resistant, multilayer, optical reflective coating includes alternating layers of doped and undoped dielectric material. The doping levels are low enough that there are no distinct interfaces between the doped and undoped layers so that the coating has properties nearly identical to the undoped material. The coating is fabricated at high temperature with plasma-assisted chemical vapor deposition techniques to eliminate defects, reduce energy-absorption sites, and maintain proper chemical stoichiometry. A number of differently-doped layer pairs, each layer having a thickness equal to one-quarter of a predetermined wavelength in the material are combined to form a narrowband reflective coating for a predetermined wavelength. Broadband reflectors are made by using a number of narrowband reflectors, each covering a portion of the broadband.

  11. Microwave dielectric properties of (Zn1-xMgx)TiO3 (ZMT) ceramics for dielectric resonator antenna application

    International Nuclear Information System (INIS)

    Highlights: → Experimental studies on ZMT fabricated cylindrical dielectric resonator antennas. → Fabricated CDRAs provided broad beam, low side lobe and cross-polarized lobe levels. → Fabricated CDRAs have potential application in wireless communication field. - Abstract: Present investigation provides experimental studies on cylindrical dielectric resonator antennas (CDRAs) fabricated from (Zn1-xMgx)TiO3 (ZMT) ceramic material with different substitution of Mg in place of Zn (x = 0.1, 0.2, 0.3, 0.4 and 0.5) along with measurement of material permittivity in C-band of microwave frequencies. The dielectric properties of the ZMT ceramic materials with different x values (x = 0.1-0.5) have been measured at microwave frequencies using Hakki-Coleman method modified by Courtney. The value of dielectric constant and loss tangent decreases with the increase in Mg content. The dielectric constant is minimum for x = 0.3 and loss tangent is minimum for x = 0.5. The variations of return loss and input impedance versus frequency and radiation patterns of CDRAs at their respective resonant frequencies are studied experimentally. The measured results for resonant frequency and return loss bandwidth of the CDRAs are also compared with theoretical ones. The measured resonant frequencies of all the four CDRAs are nearly in agreement with respective theoretical values and the values of input resistance at respective resonant frequencies of the CDRAs match well with the coaxial feed impedance of 50 Ω. The designed CDRAs have broad beam, low side lobe and cross-polarized lobe levels.

  12. Microwave losses of bulk CaC 6

    Science.gov (United States)

    Cifariello, G.; Di Gennaro, E.; Lamura, G.; Andreone, A.; Emery, N.; Hérold, C.; Marêché, J. F.; Lagrange, P.

    2007-09-01

    We report a study of the temperature dependence of the surface resistance RS in the graphite intercalated compound (GIC) CaC6, where superconductivity at 11.5 K was recently discovered. Experiments are carried out using a copper dielectrically loaded cavity operating at 7 GHz in a "hot finger" configuration. Bulk CaC6 samples have been synthesized from highly oriented pyrolytic graphite. Microwave data allow to extract unique information on the quasiparticle density and on the nature of pairing in superconductors. The analysis of RS(T) confirms our recent experimental findings that CaC6 behaves as a weakly-coupled, fully gapped, superconductor.

  13. Light-induced space-charge fields for the structuration of dielectric materials

    International Nuclear Information System (INIS)

    Light-induced space-charge fields in lithium-niobate crystals are used for patterning of dielectric materials. This includes tailored ferroelectric domains in the bulk of the crystal, different sorts of micro and nanoparticles on a crystal surface, as well as poling of electrooptic chromophores. A stochastical model is introduced, which can describe the spatial inhomogeneous domain inversion. (orig.)

  14. Application of dielectric soil moisture sensors for real-time automated irrigation control

    OpenAIRE

    Kuyper, M.; Balendonck, J.

    2001-01-01

    In this article the irrigation control system to be developed in the running Waterman project is outlined. Also, the following process monitoring considerations are discussed: what soil moisture state to measure, calibration for soil water content, and the temperature dependence of soil dielectric constant and bulk electrical conductivity (EC).

  15. Dielectric Decrement Effects on Nonlinear Electrophoresis of Ideally Polarizable Particles

    Science.gov (United States)

    Moran, Jeffrey L.; Chan, Wai Hong Ronald; Buie, Cullen R.; Figliuzzi, Bruno

    2014-11-01

    We present numerical simulations of nonlinear electrophoresis of ideally polarizable particles that specifically include the effects of a spatially non-uniform dielectric permittivity near the particle surface. Models for this dielectric decrement phenomenon have been developed by several authors, including Ben-Yaakov et al. [J. Phys.: Condens. Matter 2009] Hatlo et al. [EPL 2012], and Zhao & Zhai [JFM 2013]. We extend this work to ideally polarizable particles and include the effects of surface conduction and advective transport in the electric double layer. By numerically solving for the coupled velocity field, electric potential, and ionic concentration distributions in the bulk solution surrounding the particle, we demonstrate that the dielectric decrement model predicts ionic saturation around the particle and thus physical implications that resemble those resulting from the steric model developed by Kilic et al. [PRE 2007], albeit with differences that reflect the nonlinearity of the modified Poisson-Boltzmann equation. In addition, we develop a generalized condensed layer model that approximates both the steric and dielectric decrement models in the limits of strong electric fields and negligible surface conduction to obtain more physical insights into these models. We demonstrate that the mobility in both models asymptotically scales as the square root of the electric field at high fields, recovering the result of Bazant et al. [Adv. Colloid Interface Sci. 2009].

  16. Inflation from bulk viscosity

    CERN Document Server

    Bamba, Kazuharu

    2015-01-01

    We explore the perfect fluid description of the inflationary universe. In particular, we investigate a fluid model with the bulk-viscosity term. We find that the three observables of inflationary cosmology: the spectral index of the curvature perturbations, the tensor-to-scalar ratio of the density perturbations, and the running of the spectral index, can be consistent with the recent Planck results. We also reconstruct the explicit equation of state (EoS) of the viscous fluid from the spectral index of the curvature perturbations compatible with the Planck analysis. In the reconstructed models of the viscous fluid, the tensor-to-scalar ratio of the density perturbations can satisfy the constraints obtained from the Planck satellite. The running of the spectral index can explain the Planck data. In addition, it is demonstrated that in the reconstructed models of the viscous fluid, the graceful exit from inflation can be realized. Furthermore, we show that the singular inflation can occur in the viscous fluid ...

  17. Bulk-Fill Resin Composites

    DEFF Research Database (Denmark)

    Benetti, Ana Raquel; Havndrup-Pedersen, Cæcilie; Honoré, Daniel;

    2015-01-01

    restorative procedure. The aim of this study, therefore, was to compare the depth of cure, polymerization contraction, and gap formation in bulk-fill resin composites with those of a conventional resin composite. To achieve this, the depth of cure was assessed in accordance with the International Organization...... for Standardization 4049 standard, and the polymerization contraction was determined using the bonded-disc method. The gap formation was measured at the dentin margin of Class II cavities. Five bulk-fill resin composites were investigated: two high-viscosity (Tetric EvoCeram Bulk Fill, SonicFill) and...... three low-viscosity (x-tra base, Venus Bulk Fill, SDR) materials. Compared with the conventional resin composite, the high-viscosity bulk-fill materials exhibited only a small increase (but significant for Tetric EvoCeram Bulk Fill) in depth of cure and polymerization contraction, whereas the low...

  18. Thermal conductivity of dielectric thin films

    International Nuclear Information System (INIS)

    A direct reading thermal comparator has been used to measure the thermal conductivity of dielectric thin film coatings. In the past, the thermal comparator has been used extensively to measure the thermal conductivity of bulk solids, liquids, and gases. The technique has been extended to thin film materials by making experimental improvements and by the application of an analytical heat flow model. Our technique also allows an estimation of the thermal resistance of the film/substrate interface which is shown to depend on the method of film deposition. The thermal conductivity of most thin films was found to be several orders of magnitude lower than that of the material in bulk form. This difference is attributed to structural disorder of materials deposited in thin film form. The experimentation to date has centered primarily on optical coating materials. These coatings, used to enhance the optical properties of components such as lenses and mirrors, are damaged by thermal loads applied in high-power laser applications. It has been widely postulated that there may be a correlation between the thermal conductivity and the damage threshold of these materials. 31 refs., 11 figs., 8 tabs

  19. Lunar true polar wander inferred from polar hydrogen.

    Science.gov (United States)

    Siegler, M A; Miller, R S; Keane, J T; Laneuville, M; Paige, D A; Matsuyama, I; Lawrence, D J; Crotts, A; Poston, M J

    2016-03-24

    The earliest dynamic and thermal history of the Moon is not well understood. The hydrogen content of deposits near the lunar poles may yield insight into this history, because these deposits (which are probably composed of water ice) survive only if they remain in permanent shadow. If the orientation of the Moon has changed, then the locations of the shadowed regions will also have changed. The polar hydrogen deposits have been mapped by orbiting neutron spectrometers, and their observed spatial distribution does not match the expected distribution of water ice inferred from present-day lunar temperatures. This finding is in contrast to the distribution of volatiles observed in similar thermal environments at Mercury's poles. Here we show that polar hydrogen preserves evidence that the spin axis of the Moon has shifted: the hydrogen deposits are antipodal and displaced equally from each pole along opposite longitudes. From the direction and magnitude of the inferred reorientation, and from analysis of the moments of inertia of the Moon, we hypothesize that this change in the spin axis, known as true polar wander, was caused by a low-density thermal anomaly beneath the Procellarum region. Radiogenic heating within this region resulted in the bulk of lunar mare volcanism and altered the density structure of the Moon, changing its moments of inertia. This resulted in true polar wander consistent with the observed remnant polar hydrogen. This thermal anomaly still exists and, in part, controls the current orientation of the Moon. The Procellarum region was most geologically active early in lunar history, which implies that polar wander initiated billions of years ago and that a large portion of the measured polar hydrogen is ancient, recording early delivery of water to the inner Solar System. Our hypothesis provides an explanation for the antipodal distribution of lunar polar hydrogen, and connects polar volatiles to the geologic and geophysical evolution of the Moon

  20. Understanding Nonlinear Dielectric Properties in a Biaxially Oriented Poly(vinylidene fluoride) Film at Both Low and High Electric Fields.

    Science.gov (United States)

    Li, Yue; Ho, Janet; Wang, Jianchuan; Li, Zhong-Ming; Zhong, Gan-Ji; Zhu, Lei

    2016-01-13

    Understanding nonlinear dielectric behavior in polar polymers is crucial to their potential application as next generation high energy density and low loss dielectrics. In this work, we studied nonlinear dielectric properties of a biaxially oriented poly(vinylidene fluoride) (BOPVDF) film under both low and high electric fields. For fundamental nonlinear dielectric constants at low fields (measure up to the third harmonics. It was observed that the low-field dielectric nonlinearity for the BOPVDF disappeared above 10 Hz at room temperature, suggesting that the low-field dielectric nonlinearity originated from ionic migration of impurity ions rather than dipolar relaxation of the amorphous segments. Above the coercive field (EC ≈ 70 MV/m), bipolar electric displacement-electric field (D-E) loop tests were used to extract the nonlinear behavior for pure PVDF crystals, which had a clear origin of ferroelectric switching of polar crystalline dipoles and domains and nonpolar-to-polar (α → δ → β) phase transformations. By using HVBDS, it was observed that the ferroelectric switching of polar crystalline dipoles and domains in BOPVDF above the EC always took place between 20 and 500 Hz regardless of a broad range of temperature from -30 to 100 °C. This behavior was drastically different from that of the amorphous PVDF dipoles, which had a strong dependence on frequency over orders of magnitude. PMID:26698912

  1. Temperature and directional dependences of the infrared dielectric function of free standing silicon nanowire

    Energy Technology Data Exchange (ETDEWEB)

    Kazan, M.; Bruyant, A.; Sedaghat, Z.; Arnaud, L.; Blaize, S.; Royer, P. [Laboratoire de Nanotechnologie et d' Instrumentation Optique, Institut Charles Delaunay, Universite de Technologie de Troyes, CNRS FRE 2848, 12 Rue Marie Curie, 10010 Troyes, Cedex (France)

    2011-03-15

    An approach to calculate the infrared dielectric function of semiconductor nanostructures is presented and applied to silicon (Si) nanowires (NW's). The phonon modes symmetries and frequencies are calculated by means of the elastic continuum medium theory. The modes strengths and damping are calculated from a model for lattice dynamics and perturbation theory. The data are used in anisotropic Lorentz oscillator model to generate the temperature and directional dependences of the infrared dielectric function of free standing Si NW's. Our results showed that in the direction perpendicular to the NW axis, the complex dielectric function is identical to that of bulk Si. However, along the NW axis, the infrared dielectric function is a strong function of the wavelength. (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  2. Thermal kinetic and dielectric parameters of acenaphthene crystal grown by vertical Bridgman technique

    Science.gov (United States)

    Karuppusamy, S.; Dinesh Babu, K.; Nirmal Kumar, V.; Gopalakrishnan, R.

    2016-05-01

    The bulk acenaphthene crystal was grown in a single-wall ampoule by vertical Bridgman technique. X-ray diffraction analysis confirmed the orthorhombic crystal system of title compound with space group Pcm21. Thermal behavior of compound was studied using thermogravimetry—differential scanning calorimetry analysis. Thermal kinetic parameters like activation energy, frequency factor, Avrami exponent, reaction rate and degree of conversion were calculated using Kissingers and Ozawa methods under non-isothermal condition for acenaphthene crystal and reported for the first time. The calculated thermal kinetic parameters are presented. Dielectric studies were performed to calculate the dielectric parameters such as dielectric constant, dielectric loss, AC conductivity, and activation energy from Arrhenius plot.

  3. Spontaneous polarization behaviors in hybrid halide perovskite film

    International Nuclear Information System (INIS)

    Spontaneous polarization behaviors of hybrid perovskite CH3NH3PbI3 film were confirmed by in situ PFM and spectroscopic ellipsometry. The film exhibits uniform spontaneous polarization and ferroelectric domain inversion performance. The fitted dielectric constants spectra agree well with the calculated ones. We attribute the spontaneous polarization behaviors of hybrid perovskite to lone pair electrons, and its outstanding photovoltaic performance partially originates from spontaneous polarization and plasma resonance. This report will facilitate understanding of the instinct physical essence of hybrid perovskite solar cells

  4. Frequency selective and polarization sensitive reflector antennas

    OpenAIRE

    Edenhofer, Peter

    1997-01-01

    A variety of backscattering structures and grids is discussed to achieve frequency selection or/and polarization sensitivity. Theoretical concepts are reviewed numerically to compute co- and crosspolar reflection and transmission coefficients depending on parameters such as signal frequency, angle of incidence and grid orientation, grid geometry, and dielectric substrate. Special attention is given to technical applications in terms of dipole gridded antenna reflectors. Specific features such...

  5. State of water in starch-water systems in the gelatinization temperature range as investigated using dielectric relaxation spectroscopy

    Science.gov (United States)

    Motwani, Tanuj

    Starch-water interactions occurring during gelatinization are critical for developing a mechanistic understanding of the gelatinization process. The overall goal of this project was to investigate the state of water in starch-water systems in the gelatinization temperature range using dielectric relaxation spectroscopy. In the first part of the project, the dielectric response of native wheat starch-water slurries was measured at seven different starch concentrations between 5--60% starch (w/w) in the frequency range of 200 MHz--20 GHz at 25°C. The deconvolution of the dielectric spectra using the Debye model revealed presence of up to three relaxation processes. The relaxation time range of what were considered to be the high, intermediate and low frequency relaxations were 4--9 ps, 20--25 ps and 230--620 ps, respectively. The high frequency relaxation was observed at all starch concentrations, while the intermediate and low frequency relaxation were only observed at starch concentrations of 10% and above, and 30% and above, respectively. The high frequency relaxation was attributed to bulk water, while the intermediate and low frequency relaxations were attributed to rotationally restrained water molecules present in the starch-water system. To investigate the state of water in the gelatinization temperature range, the dielectric response, gelatinization enthalpy and water absorption by 10%, 30% or 50% starch slurries were measured after heating the slurries to different end temperatures between 40--90°C for 30 min. The high frequency relaxation time for 10% starch slurry dropped significantly (Pstarch slurries, high frequency relaxation times were not significantly influenced (P>0.159) by heating up to 80°C. The intermediate and low frequency relaxation times were not significantly influenced (P>0.712) by heating for all starch concentrations. Also, the amount of water associated with the three relaxations was not significantly influenced by heating (P >0

  6. Polarization fluctuation dominated electrical transport processes of polymer-based ferroelectric field effect transistors

    Science.gov (United States)

    Senanayak, Satyaprasad P.; Guha, S.; Narayan, K. S.

    2012-03-01

    Ferroelectric field effect transistors (FE-FETs) consisting of tunable dielectric layers are utilized to investigate interfacial transport processes. Large changes in the dielectric constant as a function of temperature are observed in FE-FETs in conjunction with the ferroelectric to paraelectric transition. The devices offer a test bed to evaluate specific effects of polarization on the electrical processes. FE-FETs have dominant contributions from polarization fluctuation rather than static dipolar disorder prevalent in high k paraelectric dielectric-based FETs. Additionally, photo-excitation measurements in the depletion mode reveal clear features in the FET response at different temperatures, indicative of different transport regimes.

  7. Influence of dielectric polarization upon PD transients: Use of hollow dielectric spheres

    DEFF Research Database (Denmark)

    McAllister, Iain Wilson

    Hollow glass spheres have recently been employed to provide a reproducible source of partial discharges. The influence of the shell permittivity upon the PD transients is examined. It is shown that, relative to the non-shell situation, the magnitude of such transients may be increased or decreased...

  8. Dielectric and Ferroelectric Properties of Complex Perovskite Ceramics Under Compressive Stress

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Dielectric and ferroelectric properties of complex perovskite PZT-PZN ceramic system were investigated under the influence of the compressive stress. The results showed that the dielectric properties, i.e. dielectric constant ( εr ) and dielectric loss ( tan δ), and the ferroelectric characteristics, i.e. the area of the ferroelectric hysteresis loops, the saturation polarization ( P(sat) ), and the remnant polarization (Pr) changed significantly with increasing compressive stress. These changes depended strongly on the ceramic compositions. The experimental results on the dielectric properties could be explained by both intrinsic and extrinsic domain-related mechanisms involving domain wall motions, as well as the de-aging phenomenon. The stress-induced domain wall motion suppression and non-180° ferroelectric domain switching processes were responsible for the changes observed in the ferroelectric parameters. In addition,a significant decrease in those parameters after a cycle of stress was observed and attributed to the stress induced decrease in switchable part of spontaneous polarization. This study clearly show that the applied stress had significant influence on the electrical properties of complex perovskite ceramics.

  9. Electromagnetic identification of dielectric materials

    Directory of Open Access Journals (Sweden)

    A. F. Yanenko

    2010-05-01

    Full Text Available The electromagnetic features and parameters of dielectric materials, which are used in light industry and stomatology. The results of measuring are analyzed and the method of authentication is offered.

  10. Characterization, Microstructure, and Dielectric properties of cubic pyrochlore structural ceramics

    KAUST Repository

    Li, Yangyang

    2013-05-01

    The (BMN) bulk materials were sintered at 1050°C, 1100°C, 1150°C, 1200°C by the conventional ceramic process, and their microstructure and dielectric properties were investigated by Scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, Transmission electron microscopy (TEM) (including the X-ray energy dispersive spectrometry EDS and high resolution transmission electron microscopy HRTEM) and dielectric impedance analyzer. We systematically investigated the structure, dielectric properties and voltage tunable property of the ceramics prepared at different sintering temperatures. The XRD patterns demonstrated that the synthesized BMN solid solutions had cubic phase pyrochlore-type structure when sintered at 1050°C or higher, and the lattice parameter (a) of the unit cell in BMN solid solution was calculated to be about 10.56Å. The vibrational peaks observed in the Raman spectra of BMN solid solutions also confirmed the cubic phase pyrochlore-type structure of the synthesized BMN. According to the Scanning Electron Microscope (SEM) images, the grain size increased with increasing sintering temperature. Additionally, it was shown that the densities of the BMN ceramic tablets vary with sintering temperature. The calculated theoretical density for the BMN ceramic tablets sintered at different temperatures is about 6.7521 . The density of the respective measured tablets is usually amounting more than 91% and 5 approaching a maximum value of 96.5% for sintering temperature of 1150°C. The microstructure was investigated by using Scanning Transmission Electron Microscope (STEM), X-ray diffraction (XRD). Combined with the results obtained from the STEM and XRD, the impact of sintering temperature on the macroscopic and microscopic structure was discussed. The relative dielectric constant ( ) and dielectric loss ( ) of the BMN solid solutions were measured to be 161-200 and (at room temperature and 100Hz-1MHz), respectively. The BMN solid

  11. Interplay between quantum confinement and dielectric mismatch for ultrashallow dopants

    Science.gov (United States)

    Mol, J. A.; Salfi, J.; Miwa, J. A.; Simmons, M. Y.; Rogge, S.

    2013-06-01

    Understanding the electronic properties of dopants near an interface is a critical challenge for nanoscale devices. We have determined the effect of dielectric mismatch and quantum confinement on the ionization energy of individual acceptors beneath a hydrogen passivated silicon (100) surface. While dielectric mismatch between the vacuum and the silicon at the interface results in an image charge which enhances the binding energy of subsurface acceptors, quantum confinement is shown to reduce the binding energy. Using scanning tunneling spectroscopy we measure resonant transport through the localized states of individual acceptors. Thermal broadening of the conductance peaks provides a direct measure for the absolute energy scale. Our data unambiguously demonstrates that these two independent effects compete with the result that the ionization energy is less than 5 meV lower than the bulk value for acceptors less than a Bohr radius from the interface.

  12. Dielectric to pyroelectric phase transition induced by defect migration

    International Nuclear Information System (INIS)

    Subjecting strontium titanate single crystals to an electric field in the order of 106 V m−1 is accompanied by a distortion of the cubic crystal structure, so that inversion symmetry vanishes and a polar phase is established. Since the polar nature of the migration-induced field-stabilized polar (MFP) phase is still unclear, the present work investigates and confirms the pyroelectric structure. We present measurements of thermally stimulated and pyroelectric currents that reveal a pyroelectric coefficient pMFP in the order of 30 μC K−1m−2. Therefore, a dielectric to pyroelectric phase transition in an originally centrosymmetric crystal structure with an inherent dipole moment is found, which is induced by defect migration. From symmetry considerations, we derive space group P4mm for the MFP phase of SrTiO3. The entire electroformation cycle yields additional information about the directed movement and defect chemistry of oxygen vacancies. (paper)

  13. Effects of membrane disruption on dielectric properties of biological cells

    International Nuclear Information System (INIS)

    Disruption of the plasma membrane causes serious changes in the dielectric properties of biological cells. The changes have been simulated with spherical cell models having holes in the plasma membrane. The complex permittivity of a cubic system including a cell model was calculated by a numerical technique based on the three-dimensional finite difference method. For a cell without hole, the complex permittivity showed dielectric relaxation (β-dispersion) as predicted from interfacial polarization theories for the single-shell model. When there is one hole in the membrane, the cell has anisotropic dielectric properties depending on whether the axis through the centres of the hole and the sphere is parallel (the parallel orientation) or perpendicular (the perpendicular orientation) to the electric field direction. In the parallel orientation, dielectric relaxation (called 'α-dispersion') appeared at lower frequencies in addition to the β-dispersion, whereas only the β-dispersion was found in the perpendicular orientation. When there were two holes at the opposite poles of the cell, the 'α-dispersion' did not appear and the intensity of the β-dispersion decreased with increasing size of the holes. When two holes located in the hemisphere of the cell, however, the 'α-dispersion' appeared again. These results suggest that the occurrence of the 'α-dispersion' requires either the presence of one hole or the localization of holes

  14. Dielectric tuned surface plasmon resonances on metallic gratings

    Science.gov (United States)

    Hauser, Adam; Flaherty, Bill; Law, Ka Ming; Mikheev, Evgeny; Kajdos, Adam; Stemmer, Susanne; Allen, S. James

    2015-03-01

    We explore the effect of substrate dielectric constant on the dispersion of infrared surface plasmons supported by micron scale metal gratings. Of particular interest are substrate dielectrics that can be tuned by electric fields and thereby make possible gated plasmonic devices. Angle resolved s and p polarized reflectivity is used to observe the plasmon dispersion for Pt gratings on various oxide dielectrics and heterostructures, LSAT, SrTiO3, Nb:SrTiO3 and LSAT/SrTiO3/GdTiO3. Most striking is the shift in the plasmon dispersion upon Nb doping of SrTiO3 caused by the free carrier contribution to the dielectric constant. We focus our attention on a metal-oxide-metal heterostructure, Pt/BaxSr1-xTiO3/Pt-grating that serves to confine the infrared field to the electric field modulated region enhancing the potential for a gated plasmonic structure. Supported by the ONR MURI ``Extreme electron density electronics'' N00014-12-0976.

  15. Dielectric modelling of cell division for budding and fission yeast

    International Nuclear Information System (INIS)

    The frequency dependence of complex permittivity or the dielectric spectrum of a system including a cell in cell division has been simulated by a numerical technique based on the three-dimensional finite difference method. Two different types of cell division characteristic of budding and fission yeast were examined. The yeast cells are both regarded as a body of rotation, and thus have anisotropic polarization, i.e. the effective permittivity of the cell depends on the orientation of the cell to the direction of an applied electric field. In the perpendicular orientation, where the rotational axis of the cell is perpendicular to the electric field direction, the dielectric spectra for both yeast cells included one dielectric relaxation and its intensity depended on the cell volume. In the parallel orientation, on the other hand, two dielectric relaxations appeared with bud growth for budding yeast and with septum formation for fission yeast. The low-frequency relaxation was shifted to a lower frequency region by narrowing the neck between the bud and the mother cell for budding yeast and by increasing the degree of septum formation for fission yeast. After cell separation, the low-frequency relaxation disappeared. The simulations well interpreted the oscillation of the relative permittivity of culture broth found for synchronous cell growth of budding yeast

  16. Dielectric modelling of cell division for budding and fission yeast

    Science.gov (United States)

    Asami, Koji; Sekine, Katsuhisa

    2007-02-01

    The frequency dependence of complex permittivity or the dielectric spectrum of a system including a cell in cell division has been simulated by a numerical technique based on the three-dimensional finite difference method. Two different types of cell division characteristic of budding and fission yeast were examined. The yeast cells are both regarded as a body of rotation, and thus have anisotropic polarization, i.e. the effective permittivity of the cell depends on the orientation of the cell to the direction of an applied electric field. In the perpendicular orientation, where the rotational axis of the cell is perpendicular to the electric field direction, the dielectric spectra for both yeast cells included one dielectric relaxation and its intensity depended on the cell volume. In the parallel orientation, on the other hand, two dielectric relaxations appeared with bud growth for budding yeast and with septum formation for fission yeast. The low-frequency relaxation was shifted to a lower frequency region by narrowing the neck between the bud and the mother cell for budding yeast and by increasing the degree of septum formation for fission yeast. After cell separation, the low-frequency relaxation disappeared. The simulations well interpreted the oscillation of the relative permittivity of culture broth found for synchronous cell growth of budding yeast.

  17. Polar Stratigraphy

    Science.gov (United States)

    1999-01-01

    These three images were taken on three different orbits over the north polar cap in April 1999. Each shows a different part of the same ice-free trough. The left and right images are separated by a distance of more than 100 kilometers (62 miles). Note the similar layers in each image.

  18. Polarization diffraction grating produced by femtosecond laser nanostructuring in glass

    OpenAIRE

    Beresna, M.; Kazansky, P.G.

    2010-01-01

    We demonstrate polarization sensitive diffractive optical element fabrication by femtosecond direct writing in the bulk of silica glass. Modulation of the anisotropic properties is produced by controlling light-induced self-assembled nano-gratings.

  19. A broadband, circular-polarization selective surface

    Science.gov (United States)

    Momeni Hasan Abadi, Seyed Mohamad Amin; Behdad, Nader

    2016-06-01

    We introduce a new technique for designing wideband circular-polarization selective surfaces (CPSSs) based on anisotropic miniaturized element frequency selective surfaces. The proposed structure is a combination of two linear-to-circular polarization converters sandwiching a linear polarizer. This CPSS consists of a number of metallic layers separated from each other by thin dielectric substrates. The metallic layers are in the form of two-dimensional arrays of subwavelength capacitive patches and inductive wire grids with asymmetric dimensions and a wire grid polarizer with sub-wavelength period. The proposed device is designed to offer a wideband circular-polarization selection capability allowing waves with left-hand circular polarization to pass through while rejecting those having right-hand circular polarization. A synthesis procedure is developed that can be used to design the proposed CPSS based on its desired band of operation. Using this procedure, a prototype of the proposed CPSS operating in the 12-18 GHz is designed. Full-wave electromagnetic simulations are used to predict the response of this structure. These simulation results confirm the validity of the proposed design concept and synthesis procedure and show that proposed CPSS operates within a fractional bandwidth of 40% with a co-polarization transmission discrimination of more than 15 dB. Furthermore, the proposed design is shown to be capable of providing an extremely wide field of view of ±60°.

  20. Calculating the dielectric anisotropy of nematic liquid crystals: a reinvestigation of the Maier-Meier theory

    Institute of Scientific and Technical Information of China (English)

    Zhang Ran; He Jun; Peng Zeng-Hui; Xuan Li

    2009-01-01

    This paper investigates the average dielectric permittivity (-ε) in the Maier-Meier theory for calculating the dielectric anisotropy (△ε) of nematic liquid crystals. For the reason that e of nematics has the same expression as the dielectric permittivity of the isotropic state, the Onsager equation for isotropic dielectric was used to calculate it. The computed -ε shows reasonable agreement with the results of the numerical methods used in the literature. Molecular parameters, such as the polarizability and its anisotropy, the dipole moment and its angle with the molecular long axis,were taken from semi-empirical quantum chemistry (MOCPAC/AM1) modeling. The calculated values of Ae according to the Maier-Meier equation are in good agreement with the experimental results for the investigated compounds having different core structures and polar substituents.

  1. Dielectric investigations of vanadium modified barium zirconium titanate ceramics obtained from mixed oxide method

    Energy Technology Data Exchange (ETDEWEB)

    Moura, F. [Laboratorio Interdisciplinar em Ceramica, Departamento de Fisico-Quimica, Instituto de Quimica Universidade Estadual Paulista, Bairro Quitandinha, CEP 14800-900, Araraquara, SP (Brazil); Simoes, A.Z. [Universidade Federal de Itajuba - Unifei - Campus Itabira, Rua Sao Paulo 377, Bairro Amazonas - Itabira-MG, CEP 35900-373 (Brazil)], E-mail: alezipo@yahoo.com; Aguiar, E.C.; Nogueira, I.C.; Zaghete, M.A.; Varela, J.A.; Longo, E. [Laboratorio Interdisciplinar em Ceramica, Departamento de Fisico-Quimica, Instituto de Quimica Universidade Estadual Paulista, Bairro Quitandinha, CEP 14800-900, Araraquara, SP (Brazil)

    2009-06-24

    Vanadium modified barium zirconium titanate ceramics Ba(Zr{sub 0.10}Ti{sub 0.90})O{sub 3}:2V (BZT:2V) were prepared from the mixed oxide method. According to X-ray diffraction analysis, addition of vanadium leads to ceramics free of secondary phases. Electrical characteristics reveal a dielectric permittivity at around 15,000 with low dielectric loss with a remnant polarization (P{sub r}) of 8 {mu}C/cm{sup 2} at 2 kV/cm. From the obtained results, we assume that vanadium substitution in the BZT lattice affects dielectric characteristics due to the electron-relaxation-mode in which carriers (polarons, protons, and so on) are coupled with existing dielectric modes.

  2. Dielectric investigations of vanadium modified barium zirconium titanate ceramics obtained from mixed oxide method

    International Nuclear Information System (INIS)

    Vanadium modified barium zirconium titanate ceramics Ba(Zr0.10Ti0.90)O3:2V (BZT:2V) were prepared from the mixed oxide method. According to X-ray diffraction analysis, addition of vanadium leads to ceramics free of secondary phases. Electrical characteristics reveal a dielectric permittivity at around 15,000 with low dielectric loss with a remnant polarization (Pr) of 8 μC/cm2 at 2 kV/cm. From the obtained results, we assume that vanadium substitution in the BZT lattice affects dielectric characteristics due to the electron-relaxation-mode in which carriers (polarons, protons, and so on) are coupled with existing dielectric modes.

  3. Enhanced dielectric and ferroelectric properties of Ca2+ substituted sodium bismuth titanate

    Science.gov (United States)

    Bharti, Chandrahas; Sen, A.; Sinha, T. P.

    2013-02-01

    In order to find the environmental friendly materials for various possible applications in near future, We have synthesized a series of new complex perovskite oxides CaxNa1-x(Bi1/2Ti1/2)O3 (CNBT) (where x = 0.00, 0.25, 0.50 and 0.75) by solid state reaction technique and studied the effect of Ca substitution in Na(Bi1/2Ti1/2)O3 through the microstructure, dielectric and ferroelectric properties. The frequency dependence of the dielectric constant at room temperature shows that the value of dielectric constant increases with Ca2+ substitution at room temperature. The analysis of real part of the dielectric permittivity shows Debye like relaxation with frequency at room temperature. The polarization hysteresis loops plotted at room temperature reveal the ferroelectric property for all compositions of the CNBT samples.

  4. Calculating the dielectric anisotropy of nematic liquid crystals: a reinvestigation of the Maier–Meier theory

    International Nuclear Information System (INIS)

    This paper investigates the average dielectric permittivity (ε-bar ) in the Maier–Meier theory for calculating the dielectric anisotropy (Δε) of nematic liquid crystals. For the reason that ε-bar of nematics has the same expression as the dielectric permittivity of the isotropic state, the Onsager equation for isotropic dielectric was used to calculate it. The computed ε-bar shows reasonable agreement with the results of the numerical methods used in the literature. Molecular parameters, such as the polarizability and its anisotropy, the dipole moment and its angle with the molecular long axis, were taken from semi-empirical quantum chemistry (MOCPAC/AM1) modeling. The calculated values of Δε according to the Maier–Meier equation are in good agreement with the experimental results for the investigated compounds having different core structures and polar substituents. (condensed matter: structure, thermal and mechanical properties)

  5. Structural, dielectric and magnetic behavior of nanocrystalline zinc substituted magnesium ferrite

    International Nuclear Information System (INIS)

    Zinc substituted magnesium ferrites Zn0.2Mg0.8Fe2O4 and Zn0.4Mg0.6Fe2O4 were prepared by sol-gel auto combustion method. Rietveld profile refinement of the XRD patterns confirms the formation of a cubic spinel structure in single phase. The dielectric properties viz. dielectric constant and dielectric loss tangent tanδ increase with increasing temperature. The dielectric behavior is explained by using the mechanism of polarization process, which is correlated to that of electron exchange interaction. The saturation magnetization, coercivity and remanent magnetization decreases appreciably with increase in Zn which could be attributed to change in cation distribution

  6. Dielectric coated ion thruster

    International Nuclear Information System (INIS)

    This paper describes an ion accelerator apparatus. It comprises: a source of free electrons; a chamber connected to the source of free electrons; means for accelerating the free electrons within the chamber; means for introducing a flow of a gas comprising atoms having a neutral charge into the chamber, the accelerated free electrons colliding with the atoms of the gas causing valence shell electrons to be lost by the atoms, producing therefrom a plasma of positively charged ions; and a metallic grid plate comprising one wall of the chamber and provided with spaced apart perforations extending therethrough, the grid plate being coated on both its inner and outer sides with a layer of an insulating material having a much higher dielectric constant that the metallic grid plate, the grid plate being connected to an electric potential substantially more negative than the positively charged ions so that ions drifting into the vicinity of the metallic grid plate are accelerated toward it, passing out of the chamber through the perforations. The surface of the layer of insulating material on the inner side of the metallic grid plate has an electric potential approximately equal to that of the plasma and thus acting as a screen grid, both layers of insulating material protecting the metallic grid plate from erosion by charged ions and insulating the chamber against thermal and electrical losses

  7. Experimental Studies of Antenna Miniaturization Using Magneto-Dielectric and Dielectric Materials

    OpenAIRE

    Karilainen, Antti O.; Ikonen, Pekka M. T.; Constantin R. Simovski; Tretyakov, Sergei A.; Lagarkov, Andrey N.; Maklakov, Sergei A.; Rozanov, Konstantin N.; Starostenko, Sergey N.

    2009-01-01

    Measurement results for a meandered planar inverted-F antenna (PIFA) loaded with magneto-dielectric and dielectric materials are presented. Figures of merit and ways to compare antennas with different fillings materials are discussed. The used magneto-dielectric material is described, the radiation mechanism of the meandered PIFA is studied, and the proper position for dielectric and magneto-dielectric filling is discussed and identified. Identical-size antennas with dielectric and magneto-di...

  8. Transverse shift of a beam with orbital angular momentum under reflection from a dielectric film

    CERN Document Server

    Kundikova, N D

    2013-01-01

    We present the results of numerical analysis of Gauss-Bessel beam reflection from a dielectric film under different angles of incidence. A transverse shift of the beam under the orbital momentum sign change is observed. The value of the shift is independent of the polarization state of the incident beam.

  9. Dielectric properties of liquid systems: the ideal complex permittivity in liquid mixtures

    OpenAIRE

    Adrián H. Buep

    2009-01-01

    A general definition for ideal complex permittivity in a liquid mixture was reached by considering a thermodynamically ideal mixture under the effect of an applied harmonic electric field. The resulting definition is independent of any particular dielectric model, as well as the polarity of the components.

  10. Dielectric behaviour of (Ba,Sr)TiO3 perovskite borosilicate glass ceramics

    International Nuclear Information System (INIS)

    Various perovskite (Ba,Sr)TiO3 borosilicate glasses were prepared by rapid melt-quench technique in the glass system ((Ba1-xSrx).TiO3)-(2SiO2.B2O3)-(K2O)-(La2O3). On the basis of differential thermal analysis results, glasses were converted into glass ceramic samples by regulated heat treatment schedules. The dielectric behaviour of crystallized barium strontium titanate borosilicate glass ceramic samples shows diffuse phase transition. The study depicts the dielectric behaviour of glass ceramic sample BST5K1L0.2S814. The double relaxation was observed in glass ceramic samples corresponding 80/20% Ba/Sr due to change in crystal structure from orthorhombic to tetragonal and tetragonal to cubic with variation of temperature. The highest value of dielectric constant was found to be 48289 for the glass ceramic sample BST5K1L0.2S814. The high value of dielectric constant attributed to space charge polarization between the glassy phase and perovskite phase. Due to very high value of dielectric constant, such glass ceramics are used for high energy storage devices. La2O3 acts as nucleating agent for crystallization of glass to glass ceramics and enhances the dielectric constant and retarded dielectric loss. Such glass ceramics can be used in high energy storage devices such as barrier layer capacitors, multilayer capacitors etc. (author)

  11. Introduction of effective dielectric constant to the Poisson-Nernst-Planck model

    Science.gov (United States)

    Sawada, Atsushi

    2016-05-01

    The Poisson-Nernst-Planck (PNP) model has been widely used for analyzing impedance or dielectric spectra observed for dilute electrolytic cells. In the analysis, the behavior of mobile ions in the cell under an external electric field has been explained by a conductive nature regardless of ionic concentrations. However, if the cell has parallel-plate blocking electrodes, the mobile ions may also play a role as a dielectric medium in the cell by the effect of space-charge polarization when the ionic concentration is sufficiently low. Thus the mobile ions confined between the blocking electrodes can have conductive and dielectric natures simultaneously, and their intensities are affected by the ionic concentration and the adsorption of solvent molecules on the electrodes. The balance of the conductive and dielectric natures is quantitatively determined by introducing an effective dielectric constant to the PNP model in the data analysis. The generalized PNP model with the effective dielectric constant successfully explains the anomalous frequency-dependent dielectric behaviors brought about by the mobile ions in dilute electrolytic cells, for which the conventional PNP model fails in interpretation.

  12. Polarization-induced transport in TIPS-pentacene field-effect transistors

    Science.gov (United States)

    Laudari, Amrit; Guha, Suchi

    The dielectric constant of polymer ferroelectric dielectrics can be tuned by changing the temperature, offering a platform for monitoring the changes in interfacial transport in organic field-effect transistors (FETs), as the polarization strength is tuned. Temperature dependent transport studies of FETs have been carried out from a solution-processed organic semiconductor, 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene), using both ferroelectric and non-ferroelectric gate insulators. Non-polar dielectric based TIPS-pentacene FETs show a clear activated transport in contrast to the ferroelectric dielectric polymer, poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE), where a negative temperature coefficient of the mobility is observed in the ferroelectric temperature range. We attribute the weak temperature-dependence of the charge carrier mobility to a polarization fluctuation driven transport resulting from a coupling of the charge carriers to the surface phonons of the polar dielectric. The negative coefficient of mobility (dμ/dT ferroelectric dielectrics is not a signature of an extended-state conduction but rather denotes polarization fluctuation driven transport. This work was supported by National Science Foundation under Grant No. ECCS-1305642.

  13. Dielectric multilayer waveguides for TE and TM mode matching

    CERN Document Server

    Shyroki, D M; Shyroki, Dzmitry M.; Lavrinenko, Andrei V.

    2003-01-01

    We analyse theoretically for the first time to our knowledge the perfect phase matching of guided TE and TM modes with a multilayer waveguide composed of linear isotropic dielectric materials. Alongside strict investigation into dispersion relations for multilayer systems, we give an explicit qualitative explanation for the phenomenon of mode matching on the basis of the standard one-dimensional homogenization technique, and discuss the minimum number of layers and the refractive index profile for the proposed device scheme. Direct applications of the scheme include polarization-insensitive, intermodal dispersion-free planar propagation, efficient fibre-to-planar waveguide coupling and, potentially, mode filtering. As a self-sufficient result, we present compact analytical expressions for the mode dispersion in a finite, N-period, three-layer dielectric superlattice.

  14. Fifty years of Szigeti's dielectric theory – A review

    Indian Academy of Sciences (India)

    D B Sirdeshmukh; L Sirdeshmukh; K G Subhadra

    2007-10-01

    During the period 1949–1961 Szigeti published four seminal papers on the dielectric behaviour of crystals. Szigeti's theory is applicable to isotropic and anisotropic, ionic and covalent crystals with different structures. Szigeti's theory connects dielectric, spectroscopic and elastic properties. An important outcome of Szigeti's theory is the concept of the effective ionic charge (). It is pointed out that correlates with a number of physical properties and is a measure of ionicity of the interatomic bond. Since Szigeti's work, several theoretical models have been proposed to account for the fact that < 1. These models provide an insight into the complex polarization mechanisms in solids. This review summarizes Szigeti's work and the work that followed; the implications and applications of Szigeti's theory are discussed. Some new results are also included.

  15. Analog Optical Computing Based on Dielectric Meta-reflect-array

    CERN Document Server

    Chizari, Ata; Jamali, Mohammad Vahid; Salehi, Jawad A

    2016-01-01

    In this paper, we realize the concept of analog computing using an array of engineered gradient dielectric meta-reflect-array. The proposed configuration consists of individual subwavelength silicon nanobricks in combination with fused silica spacer and silver ground plane realizing a reflection beam with full phase coverage $2\\pi$ degrees as well as amplitude range $0$ to $1$. Spectrally overlapping electric and magnetic dipole resonances, such high-index dielectric metasurfaces can locally and independently manipulate the amplitude and phase of the incident electromagnetic wave. This practically feasible structure overcomes substantial limitations imposed by plasmonic metasurfaces such as absorption losses and low polarization conversion efficiency in the visible range. Using such CMOS-compatible and easily integrable platforms promises highly efficient ultrathin planar wave-based computing systems which circumvent the drawbacks of conventional bulky lens-based signal processors. Based on these key properti...

  16. Methods for investigating thin dielectric films in the millimeter range

    Science.gov (United States)

    Vlasov, S. N.; Parshin, V. V.; Serov, E. A.

    2010-12-01

    An original method based on determining the characteristics of open Fabry-Perot resonator modes with different polarizations is proposed for measuring parameters of dielectric plates and films with a thickness smaller than λ/2 in the millimeter and submillimeter wavelength ranges. This method is used for determining the refractive index and tanδ, as well as the thickness of films made of isotropic materials. For anisotropic films of known thickness, the method makes it possible to measure the permittivity tensor components. Popular film materials such as Teflon (polytetrafluoroethylene, PTFE), lavsan (Mylar, polyethyleneterephthalate, PETP), and polyamide with a minimal thickness of ˜5 μm are investigated. Appreciable anisotropy of roll film materials and the dependence of the dielectric properties on the thickness, which is associated with manufacturing technology, are revealed. The dependence of the refractive index and tanδ on the air humidity is investigated

  17. Stiff, strong, yet tough free-standing dielectric films of graphene nanosheets-polyurethane nanocomposites with very high dielectric constant and loss

    Science.gov (United States)

    Jan, Rahim; Habib, Amir; Gul, Iftikhar Hussain

    2016-01-01

    In this study, graphene nanosheets (GNS) prepared through a liquid exfoliation technique are dispersed in thermoplastic polyurethane (TPU) at a volume fraction (Vf) of up to 0.19. Then, the electrical and mechanical properties of the obtained composites are characterized. The dielectric spectroscopy shows an excessive variation in dielectric constant (1.1 to 3.53 × 107) and dielectric tangent loss (0.03 to 2515) with varying Vf over the frequency range of 25 kHz to 5 MHz. A considerable enhancement in electrical conductivity (DC) is found, from 3.87 × 10-10 S/m (base polymer) to 53.5 S/m for the 0.19 Vf GNS-TPU nanocomposite. The GNS-TPU composites are mechanically robust, with a considerable increase in stiffness (˜4-fold) and strength (almost twice), maintaining its ductility up to 0.09 Vf GNS. The high dielectric constant at lower frequencies is attributed to the well-established Maxwell-Wagner polarization effect, whereas the high dielectric tangent loss is due to leakage currents as a physical conducting network is formed at high filler loadings. The layered structure, high aspect ratio, and improved dispersion of GNS are the main reasons for the improvement in both the dielectric characteristics and the mechanical properties of the host polymer. [Figure not available: see fulltext.

  18. Dielectric properties of nanocrystalline Co-Mg ferrites

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Jyoti, E-mail: jyotijoshi.phy2008@gmail.com [Department of Physics, University of Rajasthan, Jaipur (India); Sharma, Neha [Department of Physics, VEC Lakhanpur, Sarguja University, Ambikapur (C.G.) (India); Parashar, Jyoti; Saxena, V.K.; Bhatnagar, D. [Department of Physics, University of Rajasthan, Jaipur (India); Sharma, K.B. [Department of Physics, S. S. Jain Subodh P. G. College, Jaipur (India)

    2015-11-15

    Nanocrystalline powder samples with chemical formula Co{sub x}Mg{sub 1−x}Fe{sub 2}O{sub 4} (x = 0, 0.2, 0.4, 0.6, 0.8 and 1.0) have been synthesized by sol–gel auto combustion method using citric acid as fuel agent. The rietveld refinement study of x-ray diffraction patterns confirmed the spinel single phase formation for all samples. Dielectric constant (ε′), dielectric loss tangent (tan δ) and AC conductivity of Co{sub x}Mg{sub 1−x}Fe{sub 2}O{sub 4} ferrite nanoparticles have been measured at room temperature in the frequency range from 1000 Hz to 120 MHz. The dielectric dispersion observed at lower frequency region is attributed to Maxwell–Wagner two layer model, which is in agreement with Koops phenomenological theory. The observed results have been explained by polarization which is attributed to the electron exchange between Fe{sup 2+} and Fe{sup 3+} ions. The temperature variation of ε′ and tanδ for some particular frequencies were studied. The rapid increase in ε′ and tan δ has been explained using thermally activated electron exchange between Fe{sup 2+} ↔ Fe{sup 3+} and Co{sup 2+} ↔ Co{sup 3+} ions at adjacent octahedral sites. The role of interfacial polarization has been focused to explain the high dispersion in ε′ and tanδ with temperature observed at low frequencies. - Graphical abstract: (a) TEM image of Co{sub 0.4}Mg{sub 0.6}Fe{sub 2}O{sub 4} shows the nano size of the synthesized ferrite particles and (b) Dielectric constant behavior with frequency of Co{sub x}Mg{sub 1−x}Fe{sub 2}O{sub 4} ferrite.

  19. Mining the bulk positron lifetime

    Energy Technology Data Exchange (ETDEWEB)

    Aourag, H.; Guittom, A. [Centre de Recherche Nucleaire d' Alger (CRNA), Alger Gare - Algiers (Algeria)

    2009-02-15

    We introduce a new approach to investigate the bulk positron lifetimes of new systems based on data-mining techniques. Through data mining of bulk positron lifetimes, we demonstrate the ability to predict the positron lifetimes of new semiconductors on the basis of available semiconductor data already studied. Informatics techniques have been applied to bulk positron lifetimes for different tetrahedrally bounded semiconductors in order to discover computational design rules. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  20. Mining the bulk positron lifetime

    International Nuclear Information System (INIS)

    We introduce a new approach to investigate the bulk positron lifetimes of new systems based on data-mining techniques. Through data mining of bulk positron lifetimes, we demonstrate the ability to predict the positron lifetimes of new semiconductors on the basis of available semiconductor data already studied. Informatics techniques have been applied to bulk positron lifetimes for different tetrahedrally bounded semiconductors in order to discover computational design rules. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  1. Advances in bulk port development

    Energy Technology Data Exchange (ETDEWEB)

    Soros, P. (Soros Associates Consulting Engineers, New York, NY (USA))

    1991-03-01

    The article features several recently developed bulk ports which illustrate aspects of new technology or concepts in maritime transport. Low handling capacity bulk terminals at Ponta da Madeira, Brazil and Kooragang Island, Australia and the low-cost bulk port at Port of Corpus Christi, Texas are described. Operations at the ports of Pecket and Tocopilla in Chile, which had special technical problems, are mentioned. Coal terminals at Port Kembla, Australia and St. Johns River in Florid Jacksonville, Florida are featured as examples of terminals which had to be designed to meet high environmental standards. 13 refs., 2 figs., 14 photos.

  2. Dielectric properties of water in Triton X-100 (nonionic detergent)-water mixtures

    International Nuclear Information System (INIS)

    Dielectric measurements were carried out for mixtures of Triton X-100 (TX, a nonionic detergent with a poly(ethylene oxide) chain) and water with or without electrolytes over a frequency range of 1 MHz to 10 GHz to study the structure and dynamics of water molecules in the mixtures. Dielectric relaxation was found above 100 MHz, being assigned to the dielectric relaxation of water. The intensity of the dielectric relaxation was proportional to the water content above 0 deg. C. Below the freezing temperature of bulk water, the relaxation intensity decreased at TX concentrations (CTX) below 50 wt% at -10 deg. Cand below 60 wt% at -20 deg. Cbecause frozen water shifts the dielectric relaxation to a frequency region far below 1 MHz. This indicated that there is no bulk water at CTX above 50 wt% and that at least two water molecules per ethylene oxide (EO) unit are tightly associated with the ethylene oxide chain. The low-frequency conductivity of the mixtures of TX and electrolyte solutions was well represented by Bruggeman's mixture equation at CTX below 40 wt%, if two water molecules per EO unit form an insulating shell surrounding TX micelles

  3. Polarization entangled state measurement on a chip

    CERN Document Server

    Sansoni, L; Vallone, G; Mataloni, P; Crespi, A; Ramponi, R; Osellame, R

    2010-01-01

    The emerging strategy to overcome the limitations of bulk quantum optics consists of taking advantage of the robustness and compactness achievable by the integrated waveguide technology. Here we report the realization of a directional coupler, fabricated by femtosecond laser waveguide writing, acting as an integrated beam splitter able to support polarization encoded qubits. This maskless and single step technique allows to realize circular transverse waveguide profiles able to support the propagation of Gaussian modes with any polarization state. Using this device, we demonstrate the quantum interference with polarization entangled states and singlet state projection.

  4. Image brightening in samples of high dielectric constant.

    Science.gov (United States)

    Tropp, James

    2004-03-01

    An analytic solution is given for the electromagnetic problem of a lossy dielectric cylinder of infinite length, irradiated by a circularly polarized radiofrequency (RF) magnetic field; the NMR-active components of the field inside the cylinder are projected out by transforming the RF Hamiltonian to the rotating frame and retaining only those terms independent of time; it is noted that the resulting cartesian field components are required to be real. The squared magnitude of the NMR-active fields are then used to calculate the gradient-recalled images of the cylinder, for small tip angles of the magnetization; and the result is shown to predict almost quantitatively the intensity patterns of experimental proton images at 3.0 and 4.0T, in a cylindrical phantom of radius 9.25cm, filled with 0.05M aqueous NaCl. In particular, the artifactual brightening at the center of the recorded image is convincingly reproduced in a simulation, whose underlying model excludes wave propagation along the direction of the cylinder axis. Formation of the artifact is explained in terms of the focussing of the RF magnetic field at the center of the cylinder, as illustrated by contour plots showing the time evolution of the rotating flux. An extended electromagnetic model--having the dielectric cylinder enclosed in a long, shielded volume resonator (e.g., of bird cage type)--is then sketched. The mathematical details appear in Appendix A; and the simulated images are shown to be virtually indistinguishable from those of the simpler original model. The theory of the Q, or quality factor, of the dielectric cylinder--considered itself as a resonant object--is developed for the enclosed cylinder model, where flux containment by the shield permits an unambiguous treatment of both the stored energy and the radiative losses. This is extended to treat the Q of a lossy dielectric sphere without shielding. Further plots of flux contours are given for the sphere, excited at 208 MHz with a uniform

  5. Freezing of the Nb5 + ion dynamics in AgNbO3 studied by linear and nonlinear dielectric response

    Science.gov (United States)

    Miga, S.; Kania, A.; Dec, J.

    2011-04-01

    Linear and nonlinear dielectric measurements of AgNbO3 ceramics and single crystals were carried out for the M phases (77-673 K). The linear dielectric response is dominated by the contribution of the submillimetre relaxational mode related to the Nb5 + ion dynamics (M2-M3). On the other hand, nonlinear dielectric χ3' susceptibility revealed anomalies at three characteristic temperatures: 90, 325 and 448 K. Two later ones are connected with changes of the Nb5 + ion dynamics. At Tf = 448 K a partial freezing of the Nb5 + ion displacement to the anti-polar, antiferroelectric array takes place. At 325 K further freezing of Nb and Ag displacements to the polar weak relaxor ferroelectric or dipolar glass transition occurs. This polar state coexists with the ground antiferroelectric one.

  6. Freezing of the Nb5+ ion dynamics in AgNbO3 studied by linear and nonlinear dielectric response

    International Nuclear Information System (INIS)

    Linear and nonlinear dielectric measurements of AgNbO3 ceramics and single crystals were carried out for the M phases (77-673 K). The linear dielectric response is dominated by the contribution of the submillimetre relaxational mode related to the Nb5+ ion dynamics (M2-M3). On the other hand, nonlinear dielectric χ3' susceptibility revealed anomalies at three characteristic temperatures: 90, 325 and 448 K. Two later ones are connected with changes of the Nb5+ ion dynamics. At Tf = 448 K a partial freezing of the Nb5+ ion displacement to the anti-polar, antiferroelectric array takes place. At 325 K further freezing of Nb and Ag displacements to the polar weak relaxor ferroelectric or dipolar glass transition occurs. This polar state coexists with the ground antiferroelectric one.

  7. Comparative Study Between Dispersive and Non-Dispersive Dielectric Permittivity in Spectral Remittances of Chiral Sculptured Zirconia Thin Films

    CERN Document Server

    Babaei, Ferydon; 10.1016/j.optcom.2008.02.012

    2010-01-01

    The transmission and reflection spectra from a right-handed chiral sculptured zirconia thin film are calculated using the piecewise homogeneity approximation method and the Bruggeman homogenization formalism by considering that the propagation of both dispersive and non-dispersive dielectric function occurs for axial and non-axial states. The comparison of spectral results shows that the dispersion of the dielectric function has a considerable effect on the results. In axial excitation of cross-polarized reflectances and co-polarized transmittances the dispersion effect becomes more pronounced at wavelengths further away from the homogenization wavelength. This is also true in case of non-axial excitation of circular transmittances, while there are considerable differences for cross-polarized reflectances where (wavelength) the first Bragg peak occurs. At wavelengths in the vicinity of the homogenization wavelength the dispersion effect of the dielectric function in becomes more significant.

  8. Bulk Nuclear Properties from Reactions

    OpenAIRE

    Danielewicz, P.

    2002-01-01

    Extraction of bulk nuclear properties by comparing reaction observables to results from semiclassical transport-model simulations is discussed. Specific properties include the nuclear viscosity, incompressibility and constraints on the nuclear pressure at supranormal densities.

  9. Bulk charges in eleven dimensions

    CERN Document Server

    Hawking, Stephen William

    1998-01-01

    Eleven dimensional supergravity has electric type currents arising from the Chern-Simon and anomaly terms in the action. However the bulk charge integrates to zero for asymptotically flat solutions with topological trivial spatial sections. We show that by relaxing the boundary conditions to generalisations of the ALE and ALF boundary conditions in four dimensions one can obtain static solutions with a bulk charge preserving between 1/16 and 1/4 of the supersymmetries. One can introduce membranes with the same sign of charge into these backgrounds. This raises the possibility that these generalized membranes might decay quantum mechanically to leave just a bulk distribution of charge. Alternatively and more probably, a bulk distribution of charge can decay into a collection of singlely charged membranes. Dimensional reductions of these solutions lead to novel representations of extreme black holes in four dimensions with up to four charges. We discuss how the eleven-dimensional Kaluza-Klein monopole wrapped a...

  10. Composite surface-plasmon-polariton waves guided by a thin metal layer sandwiched between a homogeneous isotropic dielectric material and a periodically multilayered isotropic dielectric material

    Science.gov (United States)

    Chiadini, Francesco; Fiumara, Vincenzo; Scaglione, Antonio; Lakhtakia, Akhlesh

    2015-01-01

    Multiple p- and s-polarized compound surface-plasmon-polariton (SPP) waves at a fixed frequency can be guided by a structure consisting of a metal layer sandwiched between a homogeneous isotropic dielectric (HID) material and a periodic multilayered isotropic dielectric (PMLID) material. For any thickness of the metal layer, at least one compound SPP wave must exist. It possesses the p-polarization state, and is strongly bound to the metal/HID interface when the metal thickness is large but to both metal/dielectric interfaces when the metal thickness is small. When the metal layer vanishes, this compound SPP wave transmutes into a Tamm wave. Additional compound SPP waves exist, depending on the thickness of the metal layer, the relative permittivity of the HID material, and the period and composition of the PMLID material. Some of these are p-polarized, the others are s-polarized. All of them differ in phase speed, attenuation rate, and field profile, even though all are excitable at the same frequency. The multiplicity and dependence of the number of compound SPP waves on the relative permittivity of the HID material when the metal layer is thin could be useful for optical sensing applications and intrachip plasmonic optical communication.

  11. Compound surface-plasmon-polariton waves guided by a thin metal layer sandwiched between a homogeneous isotropic dielectric material and a periodically multilayered isotropic dielectric material

    CERN Document Server

    Chiadini, Francesco; Scaglione, Antonio; Lakhtakia, Akhlesh

    2015-01-01

    Multiple p- and s-polarized compound surface plasmon-polariton (SPP) waves at a fixed frequency can be guided by a structure consisting of a metal layer sandwiched between a homogeneous isotropic dielectric (HID) material and a periodic multilayered isotropic dielectric (PMLID) material. For any thickness of the metal layer, at least one compound SPP wave must exist. It possesses the p-polarization state, is strongly bound to the metal/HID interface when the metal thickness is large but to both metal/dielectric interfaces when the metal thickness is small. When the metal layer vanishes, this compound SPP wave transmutes into a Tamm wave. Additional compound SPP waves exist, depending on the thickness of the metal layer, the relative permittivity of the HID material, and the period and the composition of the PMLID material. Some of these are p polarized, the others being s polarized. All of them differ in phase speed, attenuation rate, and field profile, even though all are excitable at the same frequency. The...

  12. Surface optical phonon scattering in N-polar GaN quantum well channels

    OpenAIRE

    Singisetti, Uttam

    2013-01-01

    N-polar GaN channel mobility is important for high frequency device applications. In this Letter, we report the theoretical calculations on the surface optical (SO) phonon scattering rate of two-dimensional electron gas (2-DEG) in N-polar GaN quantum well channels with high-k dielectrics. The effect of SO phonons on 2-DEG mobility was found to be small at >5 nm channel thickness. However, the SO mobility in 3 nm N-polar GaN channels with high-k dielectrics is low and limits the total mobility...

  13. All-dielectric bianisotropic nanoantennas

    CERN Document Server

    Alaee, Rasoul; Rahimzadegan, Aso; Mirmoosa, Mohammad S; Kivshar, Yuri S; Rockstuhl, Carsten

    2015-01-01

    The study of high-index dielectric nanoparticles and nanoantennas currently attracts a lot of attention. They do not suffer from absorption but promise to provide control on the properties of light comparable to plasmonic nanoantennas. To further advance the field, it is important to identify versatile dielectric nanoantennas with unconventional properties. Here, we show that breaking the symmetry of an all-dielectric nanoantenna leads to a geometrically tunable magneto-electric coupling, i.e. a strong bianisotropy. The suggested nanoantenna exhibits different backscatterings and, as an interesting consequence, different optical scattering forces for opposite illumination directions. An array of such nanoantennas provides different reflection phases when illuminated from opposite directions. With a proper geometrical tuning, this bianisotropic nanoantenna is capable of providing a $2\\pi$ phase change in the reflection spectrum while possessing a rather large and constant amplitude. This allows creating reflec...

  14. High permittivity gate dielectric materials

    CERN Document Server

    2013-01-01

    "The book comprehensively covers all the current and the emerging areas of the physics and the technology of high permittivity gate dielectric materials, including, topics such as MOSFET basics and characteristics, hafnium-based gate dielectric materials, Hf-based gate dielectric processing, metal gate electrodes, flat-band and threshold voltage tuning, channel mobility, high-k gate stack degradation and reliability, lanthanide-based high-k gate stack materials, ternary hafnia and lanthania based high-k gate stack films, crystalline high-k oxides, high mobility substrates, and parameter extraction. Each chapter begins with the basics necessary for understanding the topic, followed by a comprehensive review of the literature, and ultimately graduating to the current status of the technology and our scientific understanding and the future prospects."

  15. Dielectric Bow-tie Nanocavity

    CERN Document Server

    Lu, Qijing; Zou, Chang-Ling

    2013-01-01

    We propose a novel dielectric bow-tie nanocavity consisting of two tip-to-tip opposite triangle semiconductor nanowires, whose end faces are coated by silver nanofilms. Based on the advantages of the dielectric slot and tip structures, and the high reflectivity from the silver mirror, light can be confined in this nanocavity with low loss. We demonstrate that the mode excited in this nanocavity has a deep subwavelength mode volume of 2.8*10^-4 um3 and a high quality factor of 4.9*10^4 (401.3), consequently an ultrahigh Purcell factor of 1.6*10^7 (1.36*10^5), at 4.5 K (300 K) around the resonance wavelength of 1550 nm. This dielectric bow-tie nanocavity may find applications for integrated nanophotonic circuits, such as high-efficiency single photon source, thresholdless nanolaser, and cavity QED strong coupling experiments.

  16. Probing dielectric-response effects with attosecond time-resolved streaked photoelectron spectroscopy of metal surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, C.-H.; Thumm, U. [Department of Physics, Kansas State University, Manhattan, Kansas 66506 (United States)

    2011-12-15

    The release of conduction-band electrons from a metal surface by a subfemtosecond extreme ultraviolet (XUV) pulse and their propagation through the solid provoke a dielectric response in the solid that acts back on the photoelectron wave packet. We calculated the (wake) potential associated with this photoelectron self-interaction in terms of bulk and surface plasmon excitations and show that it induces a considerable, XUV-frequency-dependent temporal shift in laser-streaked XUV photoemission spectra, suggesting the observation of the ultrafast solid-state dielectric response in contemporary streaked photoemission experiments.

  17. Dielectric Constants and Lattice Vibrations in Ionic Crystals

    International Nuclear Information System (INIS)

    A number of relations have been derived between the static and high-frequency dielectric constants of crystals and the frequencies and polarization properties of optic phonons of small wave-number. The concept of ''apparent charge'' is important in this connection. It is a quantity which can be measured experimentally but is not the same as ionic charge. It should be possible to determine apparent charges by a combination of the results of measurement of reflectivity in the infra-red, and of neutron inelastic scattering. (author)

  18. Detection of bacterial concentration variations based on dielectric magnetic flux.

    Science.gov (United States)

    Chen, Jingyao; Cai, Jie; Huang, Xingjian; Yi, Tian; Wang, Kexing; Pan, Siyi

    2016-02-01

    This study is based on the development of bacterial count quantification generated by medium dielectric variations and consequent polarization material release. The proposed approach is an action method for the fast detection of bacterial concentration in orange juice. The sensing method relies on bacterial attachment up to biofilm formation. Furthermore, different media provide more oxygen group content to enhance capacitance and self-discharge. The test took only 30 min and it provided the means for rapid bacterial detection in the juice industry. PMID:26304394

  19. Channeling of Protons Through Carbon Nanotubes Embedded in Dielectric Media

    OpenAIRE

    Borka, D.; Mowbray, D. J.; Mišković, Z. L.; Petrović, S.; Nešković, N.

    2008-01-01

    We investigate how the dynamic polarization of the carbon atoms valence electrons affects the spatial distributions of protons channeled in the (11, 9) single-wall carbon nanotubes placed in vacuum and embedded in various dielectric media. The initial proton speed is varied between 3 and 8 a.u., corresponding to the energies between 0.223 and 1.59 MeV, respectively, while the nanotube length is varied between 0.1 and 0.8 $\\mu$m. The spatial distributions of channeled protons are generated usi...

  20. Fringe integral equation method for a truncated grounded dielectric slab

    DEFF Research Database (Denmark)

    Jørgensen, Erik; Maci, S.; Toccafondi, A.

    2001-01-01

    The problem of scattering by a semi-infinite grounded dielectric slab illuminated by an arbitrary incident TMz polarized electric field is studied by solving a new set of “fringe” integral equations (F-IEs), whose functional unknowns are physically associated to the wave diffraction processes...... occurring at the truncation. The F-IEs are obtained by subtracting from the surface/surface integral equations pertinent to the truncated slab, an auxiliary set of equations obtained for the canonical problem of an infinite grounded slab illuminated by the same source. The F-IEs are solved by the method of...

  1. Capacitive Cells for Dielectric Constant Measurement

    Science.gov (United States)

    Aguilar, Horacio Munguía; Maldonado, Rigoberto Franco

    2015-01-01

    A simple capacitive cell for dielectric constant measurement in liquids is presented. As an illustrative application, the cell is used for measuring the degradation of overheated edible oil through the evaluation of their dielectric constant.

  2. Dielectric Bow-tie Nanocavity

    OpenAIRE

    Lu, Qijing; Shu, Fang-Jie; Zou, Chang-Ling

    2013-01-01

    We propose a novel dielectric bow-tie nanocavity consisting of two tip-to-tip opposite triangle semiconductor nanowires, whose end faces are coated by silver nanofilms. Based on the advantages of the dielectric slot and tip structures, and the high reflectivity from the silver mirror, light can be confined in this nanocavity with low loss. We demonstrate that the mode excited in this nanocavity has a deep subwavelength mode volume of 2.8*10^-4 um3 and a high quality factor of 4.9*10^4 (401.3)...

  3. Dielectric Resonator Metasurface for Dispersion Engineering

    OpenAIRE

    Achouri, Karim; Yahyaoui, Ali; Gupta, Shulabh; Rmili, Hatem; Caloz, Christophe

    2016-01-01

    We introduce a practical dielectric metasurface design for microwave frequencies. The metasurface is made of an array of dielectric resonators held together by dielectric connections thus avoiding the need of a mechanical support in the form of a dielectric slab and the spurious multiple reflections that such a slab would generate. The proposed design can be used either for broadband metasurface applications or monochromatic wave transformations. The capabilities of the concept to manipulate ...

  4. Dielectric crystal in the Planck blackbody

    CERN Document Server

    Pardy, Miroslav

    2015-01-01

    The dielectric crystal with the index of refraction n is inserted in the Planck blackbody. The spectral formula for photons in such dielectric medium is derived with the equation for the temperature of internal photons. The derived equation is solved for the constant index of refraction. The photon ow initiates the osmotic pressure of he Debye phonons in the dielectric blackbody. Key words: Thermodynamics, blackbody, photons, phonons, dielectric medium, dispersion.

  5. Dielectric response of the human tooth dentine

    Energy Technology Data Exchange (ETDEWEB)

    Leskovec, J. [Dental Clinic, Faculty of Medicine, University of Ljubljana, Hrvatski trg 6, 1104 Ljubljana (Slovenia); Filipic, C. [Jozef Stefan Institute, P.O. Box 3000, 1001 Ljubljana (Slovenia); Levstik, A. [Jozef Stefan Institute, P.O. Box 3000, 1001 Ljubljana (Slovenia)]. E-mail: adrijan.levstik@ijs.si

    2005-07-15

    Dielectric properties of tooth dentine can be well described by the model which was developed for the dielectric response to hydrating porous cement paste. It is shown that the normalized dielectric constant and the normalized specific conductivity are proportional to the model parameters -bar {sub v0} and {sigma}{sub v}, indicating the deposition of AgCl in the dentine tubules during the duration of the precipitation. The fractal dimension of the tooth dentine was determined by dielectric spectroscopy.

  6. Dielectric response of the human tooth dentine

    International Nuclear Information System (INIS)

    Dielectric properties of tooth dentine can be well described by the model which was developed for the dielectric response to hydrating porous cement paste. It is shown that the normalized dielectric constant and the normalized specific conductivity are proportional to the model parameters -bar v0 and σv, indicating the deposition of AgCl in the dentine tubules during the duration of the precipitation. The fractal dimension of the tooth dentine was determined by dielectric spectroscopy

  7. Casimir-Lifshitz interaction between dielectric heterostructures

    International Nuclear Information System (INIS)

    The interaction between arbitrary dielectric heterostructures is studied within the framework of a recently developed dielectric contrast perturbation theory. It is shown that periodically patterned dielectric or metallic structures lead to oscillatory lateral Casimir-Lifshitz forces, as well as modulations in the normal force as they are displaced with respect to one another. The strength of these oscillatory contributions increases with decreasing gap size and increasing contrast in the dielectric properties of the materials used in the heterostructures.

  8. Casimir-Lifshitz interaction between dielectric heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Azari, Arash; Samanta, Himadri S; Golestanian, Ramin [Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH (United Kingdom)], E-mail: r.golestanian@sheffield.ac.uk

    2009-09-15

    The interaction between arbitrary dielectric heterostructures is studied within the framework of a recently developed dielectric contrast perturbation theory. It is shown that periodically patterned dielectric or metallic structures lead to oscillatory lateral Casimir-Lifshitz forces, as well as modulations in the normal force as they are displaced with respect to one another. The strength of these oscillatory contributions increases with decreasing gap size and increasing contrast in the dielectric properties of the materials used in the heterostructures.

  9. Dielectric response of the human tooth dentine

    Science.gov (United States)

    Leskovec, J.; Filipič, C.; Levstik, A.

    2005-07-01

    Dielectric properties of tooth dentine can be well described by the model which was developed for the dielectric response to hydrating porous cement paste. It is shown that the normalized dielectric constant and the normalized specific conductivity are proportional to the model parameters ɛ and σv, indicating the deposition of AgCl in the dentine tubules during the duration of the precipitation. The fractal dimension of the tooth dentine was determined by dielectric spectroscopy.

  10. Silicon-on-insulator integrated tunable polarization controller (Conference Presentation)

    Science.gov (United States)

    Sarmiento-Merenguel, Jose-Dario; Alonso-Ramos, Carlos; Halir, Robert; Le Roux, Xavier; Vivien, Laurent; Cheben, Pavel; Durán-Valdeiglesias, Elena; Molina-Fernández, Iñigo; Marris-Morini, Delphine; Xu, Danxia; Schmid, Jens H.; Janz, Siegfried; Ortega-Moñux, Alejandro

    2016-05-01

    Polarization management is a key functionality in many photonic applications, including optical communications, imaging or quantum information. Developing integrated devices capable of reliably controlling polarization state would result in compact and low cost circuits with improved stability compared with fiber or bulk optics solutions. However, stringent fabrication tolerances make the integration of polarization managing elements highly challenging. The main challenge in polarization controllers, composed by polarization rotators and polarization phase shifters, is to precisely control rotation angle in integrated polarization rotators. Proposed solutions typically require sophisticated fabrication processes or extremely tight fabrication tolerances, seriously hindering their practical application. Here we present a technology independent polarization controller scheme that relies on phase shifters to largely relax fabrication tolerances of polarization rotators. In addition, these phase shifters enable dynamic wavelength tuning. In our scheme, three polarization rotation elements are interconnected with two tunable phase shifters to adjust the polarization extinction ratio, while an output polarization phase shifter is used to select the relative phase. This way we can achieve any desired output state of polarization. We have implemented this scheme in the silicon-on-insulator platform, experimentally demonstrating a record polarization extinction range of 40 dB (± 20 dB) with a 98% coverage of the Poincaré sphere. Furthermore, the device is tunable in the complete C-band. These results constitute, to the best of our knowledge, the highest polarization extinction range achieved in a fully integrated device.

  11. Quantum effects on propagation of bulk and surface waves in a thin quantum plasma film

    International Nuclear Information System (INIS)

    The propagation of bulk and surface plasma waves in a thin quantum plasma film is investigated, taking into account the quantum effects. The generalized bulk and surface plasma dispersion relation due to quantum effects is derived, using the quantum hydrodynamic dielectric function and applying appropriate additional boundary conditions. The quantum mechanical and film geometric effects on the bulk and surface modes are discussed. It is found that quantum effects become important for a thin film of small thickness. - Highlights: • New bulk and surface plasma dispersion relations due to quantum effects are derived, in a thin quantum plasma film. • It is found that quantum effects become important for a thin quantum film of small thickness

  12. Strong surface effect on direct bulk flexoelectric response in solids

    Energy Technology Data Exchange (ETDEWEB)

    Yurkov, A. S. [Ioffe Physical-Technical Institute, 26 Politekhnicheskaya, 194021 St. Petersburg (Russian Federation); Tagantsev, A. K. [Ceramics Laboratory, Swiss Federal Institute of Technology (EPFL), CH-1015 Lausanne (Switzerland); Ioffe Physical-Technical Institute, 26 Politekhnicheskaya, 194021 St. Petersburg (Russian Federation)

    2016-01-11

    In the framework of a continuum theory, it is shown that the direct bulk flexoelectric response of a finite sample essentially depends on the surface polarization energy, even in the thermodynamic limit where the body size tends to infinity. It is found that a modification of the surface energy can lead to a change in the polarization response by a factor of two. The origin of the effect is an electric field produced by surface dipoles induced by the strain gradient. The unexpected sensitivity of the polarization response to the surface energy in the thermodynamic limit is conditioned by the fact that the moments of the surface dipoles may scale as the body size.

  13. Strong surface effect on direct bulk flexoelectric response in solids

    International Nuclear Information System (INIS)

    In the framework of a continuum theory, it is shown that the direct bulk flexoelectric response of a finite sample essentially depends on the surface polarization energy, even in the thermodynamic limit where the body size tends to infinity. It is found that a modification of the surface energy can lead to a change in the polarization response by a factor of two. The origin of the effect is an electric field produced by surface dipoles induced by the strain gradient. The unexpected sensitivity of the polarization response to the surface energy in the thermodynamic limit is conditioned by the fact that the moments of the surface dipoles may scale as the body size

  14. Femtosecond resolved solvation dynamics in polar solvents

    Science.gov (United States)

    Kahlow, Michael A.; Jarzeba, Włodzimierz; Kang, Tai Jong; Barbara, Paul F.

    1989-01-01

    The transient solvation of a polar fluorescent probe has been studied by the time resolved Stokes shift technique with roughly five times shorter time resolution than previously reported. New shorter time components in the solvation relaxation function C(t) have been discovered for methanol, propionitrile, and propylene carbonate; the C(t) function for acetonitrile is singly exponential within the limitations of the instrument. The observed C(t) has been compared to theoretical calculations using the dielectric continuum (DC) model for each solvent, with non-Debye expressions for the solvent dielectric response. For methanol the DC model predictions agree closely with experiment. For the polar aprotic solvents propylene carbonate and propionitrile, the shape of the experimental decay is different from the DC predictions, but the average decay times are closer to the DC predictions than previously reported. The comparison of theory and experiment is clearly limited by the inconsistencies and limited frequency range of the dielectric relaxation data found in the literature. The dynamic solvation measurements have also been compared to predictions of the mean spherical approximation as applied to solvation dynamics, which appear to give slower solvation rates than are observed experimentally.

  15. Dielectric-branes

    CERN Document Server

    Myers, R C

    1999-01-01

    We extend the usual world-volume action for a Dp-brane to the case of N coincident Dp-branes where the world-volume theory involves a U(N) gauge theory. The guiding principle in our construction is that the action should be consistent with the familiar rules of T-duality. The resulting action involves a variety of potential terms, i.e., nonderivative interactions, for the nonabelian scalar fields. This action also shows that Dp-branes naturally couple to RR potentials of all form degrees, including both larger and smaller than p+1. We consider the dynamics resulting from this action for Dp-branes moving in nontrivial background fields, and illustrate how the Dp-branes are ``polarized'' by external fields. In a simple example, we show that a system of D0-branes in an external RR four-form field expands into a noncommutative two-sphere, which is interpreted as the formation of a spherical D2-D0 bound state.

  16. Cluster synthesis of monodisperse rutile-TiO2 nanoparticles and dielectric TiO2-vinylidene fluoride oligomer nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Balasubramanian, B; Kraemer, KL; Valloppilly, SR; Ducharme, S; Sellmyer, DJ

    2011-09-13

    The embedding of oxide nanoparticles in polymer matrices produces a greatly enhanced dielectric response by combining the high dielectric strength and low loss of suitable host polymers with the high electric polarizability of nanoparticles. The fabrication of oxide-polymer nanocomposites with well-controlled distributions of nanoparticles is, however, challenging due to the thermodynamic and kinetic barriers between the polymer matrix and nanoparticle fillers. In the present study, monodisperse TiO2 nanoparticles having an average particle size of 14.4 nm and predominant rutile phase were produced using a cluster-deposition technique without high-temperature thermal annealing and subsequently coated with uniform vinylidene fluoride oligomer (VDFO) molecules using a thermal evaporation source, prior to deposition as TiO2-VDFO nanocomposite films on suitable substrates. The molecular coatings on TiO2 nanoparticles serve two purposes, namely to prevent the TiO2 nanoparticles from contacting each other and to couple the nanoparticle polarization to the matrix. Parallel-plate capacitors made of TiO2-VDFO nanocomposite film as the dielectric exhibit minimum dielectric dispersion and low dielectric loss. Dielectric measurements also show an enhanced effective dielectric constant in TiO2-VDFO nanocomposites as compared to that of pure VDFO. This study demonstrates for the first time a unique electroactive particle coating in the form of a ferroelectric VDFO that has high-temperature stability as compared to conventionally used polymers for fabricating dielectric oxide-polymer nanocomposites.

  17. Tailored Optical Polarization in Nano-Structured Metamaterials

    CERN Document Server

    Mendoza, Bernardo S

    2016-01-01

    A very efficient method for the calculation of the effective optical response of nano-structured composite systems allows the design of metamaterials tailored for specific optical polarization properties. We use our method to design 2D periodic arrays of sub-wavelength dielectric inclusions within nanometric supported metallic thin films which behave as either an almost perfect linearly dichroic system, as a controllable source of circular polarized light, as a system with a large circular dichroism, or as a circular polarizer. All of these systems may be tuned over a wide energy range.

  18. Hollow waveguides as polarization converting elements: a theoretical study

    Science.gov (United States)

    Helfert, S. F.; Edelmann, A.; Jahns, J.

    2015-02-01

    Subwavelength apertures in a metallic film act as hollow waveguides. By using a non-quadratic cross-section, an anisotropic transmission behaviour results for the two polarization states. Thus, an array of metallic subwavelength apertures may be used as polarization converter, e.g., as a half-wave plate. By varying orientation and shape of the cross-sections locally, one can design polarization shifting elements for complex wave fields. Here, we present a theoretical consideration on the physical properties and compare with dielectric form birefringence.

  19. Exp6-polar thermodynamics of dense supercritical water

    Energy Technology Data Exchange (ETDEWEB)

    Bastea, S; Fried, L E

    2007-12-13

    We introduce a simple polar fluid model for the thermodynamics of dense supercritical water based on a Buckingham (exp-6) core and point dipole representation of the water molecule. The proposed exp6-polar thermodynamics, based on ideas originally applied to dipolar hard spheres, performs very well when tested against molecular dynamics simulations. Comparisons of the model predictions with experimental data available for supercritical water yield excellent agreement for the shock Hugoniot, isotherms and sound speeds, and are also quite good for the self-diffusion constant and relative dielectric constant. We expect the present approach to be also useful for other small polar molecules and their mixtures.

  20. Counteracting Gravitation In Dielectric Liquids

    Science.gov (United States)

    Israelsson, Ulf E.; Jackson, Henry W.; Strayer, Donald M.

    1993-01-01

    Force of gravity in variety of dielectric liquids counteracted by imposing suitably contoured electric fields. Technique makes possible to perform, on Earth, variety of experiments previously performed only in outer space and at great cost. Also used similarly in outer space to generate sort of artificial gravitation.

  1. Dielectric waveguide amplifiers and lasers

    NARCIS (Netherlands)

    Pollnau, M.

    2014-01-01

    The performance of semiconductor amplifiers and lasers has made them the preferred choice for optical gain on a micro-chip. In the past few years, we have demonstrated that also rare-earth-ion-doped dielectric waveguides show remarkable performance, ranging from a small-signal gain per unit length o

  2. Analytic Franz-Keldysh effect in one-dimensional polar semiconductors

    International Nuclear Information System (INIS)

    The optical properties of a one-dimensional polar semiconductor in a strong electric field are considered. This class of materials includes non-centrosymmetric III-V inorganic quantum wires but also polar conjugated polymers such as polymethineimine. The polar Franz-Keldysh effect is derived via an analytic expression for the complex dielectric constant including line broadening and linear field terms. Results for the high-field non-perturbative regime as well as the low-field expansion are presented

  3. Analytic Franz-Keldysh effect in one-dimensional polar semiconductors

    CERN Document Server

    Pedersen, T G

    2003-01-01

    The optical properties of a one-dimensional polar semiconductor in a strong electric field are considered. This class of materials includes non-centrosymmetric III-V inorganic quantum wires but also polar conjugated polymers such as polymethineimine. The polar Franz-Keldysh effect is derived via an analytic expression for the complex dielectric constant including line broadening and linear field terms. Results for the high-field non-perturbative regime as well as the low-field expansion are presented.

  4. Spatial concentration distribution analysis of cells in electrode-multilayered microchannel by dielectric property measurement.

    Science.gov (United States)

    Yao, Jiafeng; Kodera, Tatsuya; Obara, Hiromichi; Sugawara, Michiko; Takei, Masahiro

    2015-07-01

    The spatial concentration distribution of cells in a microchannel is measured by combining the dielectric properties of cells with the specific structure of the electrode-multilayered microchannel. The dielectric properties of cells obtained with the impedance spectroscopy method includes the cell permittivity and dielectric relaxation, which corresponds to the cell concentration and structure. The electrode-multilayered microchannel is constructed by 5 cross-sections, and each cross-section contains 5 electrode-layers embedded with 16 micro electrodes. In the experiment, the dielectric properties of cell suspensions with different volume concentrations are measured with different electrode-combinations corresponding to different electric field distributions. The dielectric relaxations of different cell concentrations are compared and discussed with the Maxwell-Wagner dispersion theory, and the relaxation frequencies are analysed by a cell polarization model established based on the Hanai cell model. Moreover, a significant linear relationship with AC frequency dependency between relative permittivity and cell concentration was found, which provides a promising way to on-line estimate cell concentration in microchannel. Finally, cell distribution in 1 cross-section of the microchannel (X and Y directions) was measured with different electrode-combinations using the dielectric properties of cell suspensions, and cell concentration distribution along the microchannel (Z direction) was visualized at flowing state. The present cell spatial sensing study provides a new approach for 3 dimensional non-invasive online cell sensing for biological industry. PMID:26392831

  5. Diurnal effect of water stress on the dielectric properties of corn

    Science.gov (United States)

    van Emmerik, T. H.; Steele-Dunne, S. C.; Judge, J.; Van De Giesen, N.

    2013-12-01

    Microwave emission and backscatter of vegetated surfaces are influenced by the vegetation dielectric constant, a function of vegetation water content. In turn, the vegetation water content varies depending on the availability of moisture in the root zone. Understanding the variation in vegetation dielectric properties in response to root zone water availability could improve soil moisture retrievals using microwaves above vegetated areas. Here we present a unique dataset of leaf dielectric properties collected during a two month field campaign in Citra (Florida, USA). In-vivo dielectric property measurements were conducted on three corn leaves at various heights. Destructive sampling was used to determine vegetation water content. Water stress was quantified by calculating the evaporation deficit of the corn field and by monitoring the soil water tension. We will present results illustrating the influence of the observed increase in water stress on the vegetation water content and leaf dielectric properties. Simulations using the water-cloud model demonstrate the impact of the changes in vegetation water content on radar backscatter at different frequencies and polarizations. The dielectric measurements revealed the complex diurnal response of vegetation to water stress and highlight the potential for vegetation and soil water status monitoring using microwave remote sensing.

  6. Electrical conductivity and dielectric relaxation of 2-(antipyrin-4-ylhydrazono)-2-(4-nitrophenyl)acetonitrile

    International Nuclear Information System (INIS)

    The electrical and dielectric properties of the synthesized 2-(antipyrin-4-ylhydrazono)-2-(4-nitrophenyl)acetonitrile (AHNA) have been studied. The direct and alternating current (DC and AC) conductivities and complex dielectric constant were investigated in temperature range 303–403 K. The AC conductivity and dielectric properties of AHNA were investigated over frequency range 100 Hz–5 MHz. From DC and AC measurements, electrical conduction is found to be a thermally activated process. The frequency-dependent AC conductivity obeys Jonscher's universal power law in which the frequency exponent decreases with increasing temperature. The correlated barrier hopping (CBH) is the predominant model for describing the charge carrier transport in which the electrical parameters are evaluated. The activation energy is found to decrease with increasing frequency. The behaviors of dielectric and dielectric loss are discussed in terms of a polarization mechanism. The dielectric loss shows frequency power law from which the maximum barrier height is determined as 0.19 eV in terms of the Guintini model

  7. Electrical conductivity and dielectric relaxation of 2-(antipyrin-4-ylhydrazono)-2-(4-nitrophenyl)acetonitrile

    Energy Technology Data Exchange (ETDEWEB)

    El-Menyawy, E.M., E-mail: emad_elmenyawy@yahoo.com [Solid State Electronics Laboratory, Solid State Physics Department, Physics Division, National Research Center, Dokki, Cairo 12311 (Egypt); Zedan, I.T. [Basic Science Department, High Institute of Engineering and Technology, El-Arish, North Sinai (Egypt); Nawar, H.H. [Department of Chemistry, Faculty of Education, Al Jabal Al Gharbi University (Libya)

    2014-03-15

    The electrical and dielectric properties of the synthesized 2-(antipyrin-4-ylhydrazono)-2-(4-nitrophenyl)acetonitrile (AHNA) have been studied. The direct and alternating current (DC and AC) conductivities and complex dielectric constant were investigated in temperature range 303–403 K. The AC conductivity and dielectric properties of AHNA were investigated over frequency range 100 Hz–5 MHz. From DC and AC measurements, electrical conduction is found to be a thermally activated process. The frequency-dependent AC conductivity obeys Jonscher's universal power law in which the frequency exponent decreases with increasing temperature. The correlated barrier hopping (CBH) is the predominant model for describing the charge carrier transport in which the electrical parameters are evaluated. The activation energy is found to decrease with increasing frequency. The behaviors of dielectric and dielectric loss are discussed in terms of a polarization mechanism. The dielectric loss shows frequency power law from which the maximum barrier height is determined as 0.19 eV in terms of the Guintini model.

  8. Magnetic and dielectric studies of nanocrystalline zinc substituted Cu-Mn ferrites

    Energy Technology Data Exchange (ETDEWEB)

    Hankare, P.P., E-mail: p_hankarep@rediffmail.co [Department of Chemistry, Shivaji University, Kolhapur 416 004 (India); Sankpal, U.B., E-mail: sankpalumes@yahoo.co.i [Department of Chemistry, Shivaji University, Kolhapur 416 004 (India); Patil, R.P.; Jadhav, A.V.; Garadkar, K.M. [Department of Chemistry, Shivaji University, Kolhapur 416 004 (India); Chougule, B.K. [Department of Physics, Shivaji University, Kolhapur 416 004 (India)

    2011-03-15

    Ferrites with the general formula Cu{sub 1-x}Zn{sub x}FeMnO{sub 4} (where 0{<=}x{<=}1) were prepared through a citrate gel auto-combustion route. Structural characterizations carried out by X-ray diffraction reveal that the lattice constant increases with increase in zinc content. Transmission electron microscopic measurements confirm the nanoscale nature of the particles. Room temperature saturation magnetization was measured as a function of zinc concentration. The saturation magnetization increases up to x=0.25 and then decreases as zinc concentration increases. Dielectric permittivity, dielectric loss tangent, ac conductivity and complex dielectric impedance were studied in the frequency range 20 Hz-1 MHz. The results indicated a usual dielectric dispersion due to the Maxwell-Wagner type of interfacial polarization. Dielectric loss showed similar behavior as dielectric permittivity. The ac conductivity increased linearly with frequency. Complex impedance spectroscopic studies confirmed that conduction in the samples is via grain boundaries. In general, substitution of zinc plays an important role in changing the structural, electrical and magnetic properties of these ferrites.

  9. Comparison of conductor and dielectric inks in printed organic complementary transistors

    Science.gov (United States)

    Ng, Tse Nga; Mei, Ping; Whiting, Gregory L.; Schwartz, David E.; Abraham, Biby; Wu, Yiliang; Veres, Janos

    2014-10-01

    Two types of printable conductor and a bilayer gate dielectric are evaluated for use in all-additive, inkjetprinted complementary OTFTs. The Ag nanoparticle ink based on nonpolar alkyl amine surfactant or stabilizer enables good charge injection into p-channel devices, but this ink also leaves residual stabilizer that modifies the transistor backchannel and shifts the turn-on voltage to negative values. The Ag ink based on polar solvent requires dopant modification to improve charge injection to p-channel devices, but this ink allows the OTFT turn-on voltage to be close to 0 V. The reverse trend is observed for n-channel OTFTs. For gate insulator, a bilayer dielectric is demonstrated that combines the advantages of two types of insulator materials, in which a fluoropolymer reduces dipolar disorder at the semiconductor-dielectric interface, while a high-k PVDF terpolymer dielectric facilitates high gate capacitance. The dielectric is incorporated into an inverter and a three-stage ring oscillator, and the resulting circuits were demonstrated to operate at a supply voltage as low as 2 V, with bias stress levels comparable to circuits with other types of dielectrics.

  10. Thin dielectric technology and memory devices

    Science.gov (United States)

    King, Ya-Chin

    into a CMOS process for low-power dynamic or quasi-nonvolatile memory applications. Another method of embedding charge storage nodes into the gate dielectric employs germanium nano-crystals formed by oxidation of Si1-xGex . The device consists of a MOSFET with Ge nano-crystals embedded within the gate dielectric. This trap-formation method provides for precise control of the thicknesses of the oxide layers which sandwich the charge-traps, via thermal oxidation. Memory devices with write/erase speed/voltage and retention time superior to previously reported nano-crystal memory devices are demonstrated. A novel method of growing multiple gate oxide thicknesses below 5nm using oxygen implantation is presented. Experimental results show that multiple thicknesses of gate oxide with differences of up to 20A can be achieved on the same wafer without de gradation of the oxide interface and bulk properties. Unlike oxides grown with nitrogen implantation, oxides fabricated by the proposed method exhibit comparable reliability to that of thermally grown oxides.

  11. Linear and nonlinear dielectric theory for a slab: The connections between the phenomenological coefficients and the susceptibilities.

    Science.gov (United States)

    Fulton, Robert L

    2016-08-28

    The response of dielectric media to electromagnetic fields can be described by using either the response to a Maxwell field E or to an externally produced field E. The former response is measured by phenomenological (dielectric) coefficients and the latter by susceptibilities. With the purpose of clarifying some recent proposals, the connections between the linear (two-point) and first non-vanishing nonlinear (four-point) dielectric coefficients and the susceptibilities for media confined to a slab are examined using a general procedure developed sometime ago. Unlike the relations found for correlations between a local polarization density and the integrated polarization densities (total polarizations), the point-point connections give rise to non-vanishing cross correlations between polarization densities which are parallel and perpendicular to the slab surfaces. The cross correlations in the two-point connections vanish when one polarization density is integrated to form the correlations between a local polarization density and the total polarization thereby losing angular information. The integrated parallel and perpendicular correlations remain different. When the four-point connections are similarly integrated most, but not all, cross correlations vanish. The angular correlations induced by the slab surfaces render the use of point-point correlations that are valid for isotropic media invalid for use in the integrated slab densities. In addition, the nonlinear fluctuations in the perpendicular components are drastically reduced relative to those in the parallel components or in isotropic media. PMID:27586902

  12. Tunable positive and negative refraction of infrared radiation in graphene-dielectric multilayers

    International Nuclear Information System (INIS)

    Graphene-dielectric multilayers consisting of alternating layers of atom-thick graphene and nanometer-scale dielectric films exhibit characteristics of hyperbolic metamaterials, in which one positive and one negative permittivity are defined for orthogonal directions. Negative permittivity for electric field polarized in the direction parallel to the conductive graphene sheets gives rise to a negative angle of refraction and low-loss transmission for the side-incidence perspective proposed in this work. The Poynting vector tracing demonstrates the switching between positive and negative refraction in the mid-infrared region by tuning the chemical potential of graphene. This adjustable dual-mode metamaterial holds promise for infrared imaging applications

  13. Feasibility of KTa(1-x)Nb(x)O3 as a dielectric or pyroelectric microcalorimeter

    Science.gov (United States)

    Pfafman, T. E.; Silver, E.; Labov, S.; Beeman, J.; Goulding, F.; Landis, D.; Madden, N.

    1992-01-01

    We are developing a dielectric microcalorimeter for X-ray spectroscopy. We will present the results of our measurement of the dielectric permittivity, the spontaneous polarization, and the pyroelectric coefficient of the mixed-crystal quantum ferroelectric KTa(1-x)Nb(x)O3 with a doping of x = 0.012, as a function of temperature and bias voltage across the device. The effects of surface layers on the permittivity and the pyroelectric coefficient are discussed. We also show the signal results from infrared LED and alpha-particle radiation.

  14. Enhancement of the evanescent field pressure on a dielectric film by coupling with surface plasmons

    CERN Document Server

    Han, B M; Lee, S S

    1999-01-01

    We investigate theoretically the optical pressure acting on a dielectric film in a surface-plasmon-coupled evanescent wave which is produced near the surface of a thin metal-coated prism illuminated by a p-polarized plane electromagnetic wave. We show that the pressure arising from the surface-plasmon-coupled evanescent waves in a metal-coated multilayer system is about ten times as large as that on the surface of a bare dielectric prism. The evanescent field pressure has a potential application in manipulating or sorting a planar-type particle near the surface of a thin metal.

  15. Looking for a bulk point

    CERN Document Server

    Maldacena, Juan; Zhiboedov, Alexander

    2015-01-01

    We consider Lorentzian correlators of local operators. In perturbation theory, singularities occur when we can draw a position-space Landau diagram with null lines. In theories with gravity duals, we can also draw Landau diagrams in the bulk. We argue that certain singularities can arise only from bulk diagrams, not from boundary diagrams. As has been previously observed, these singularities are a clear diagnostic of bulk locality. We analyze some properties of these perturbative singularities and discuss their relation to the OPE and the dimensions of double-trace operators. In the exact nonperturbative theory, we expect no singularity at these locations. We prove this statement in 1+1 dimensions by CFT methods.

  16. Gamma probe dry bulk densities

    International Nuclear Information System (INIS)

    The gamma density probe is a useful instrument for measuring water content in small volumes of soil. Essentially, the gamma probe measures the density of the soil and water between a source and a detector. To transpose the gamma densities into water content, the dry bulk density of the soil is needed. A nondestructive method for estimating dry bulk densities for use with the gamma probe is proposed. The procedure is based on the assumption that water content values in a field dry condition were more stable than the dry bulk density values and could be transferred from one point to another. The procedure was successfully used on three areas in Reynolds Creek Experimental Watershed in southwest Idaho. (U.S.)

  17. Polarimetric scattering behavior of rough dielectric materials at terahertz frequencies

    Science.gov (United States)

    Digiovanni, David Anthony

    Technologies in the terahertz region of the spectrum are finding increased usage in areas such as communications, remote sensing, and imaging, For example, driven by the promise of greater data transfer rates, free-space communication that traditionally operate in the radio and microwave bands are being developed at terahertz frequencies. Successful transition of communication systems to higher frequencies, particularly for systems located in indoor or urban environments, will require a thorough understanding of the reflection, transmission, absorption, and scattering behavior of a wide variety of materials and surface types. Scattering properties of rough surfaces have been studied extensively at radio and microwave frequencies, however, such properties have only recently become of interest at higher frequencies. The goal of this thesis was to develop a better understanding of electromagnetic scattering from dielectric rough surfaces at millimeter wavelengths and terahertz frequencies. This goal was achieved by measuring the polarimetric scattering behavior of dielectric materials and comparing the measured data to predictions made by rough surface scattering theory. The dielectric properties and the roughness of the samples were tailored in order to provide a controlled parameter space to investigate. Fully polarimetric radar imagery of the rough surfaces were acquired at 160 GHz, 240 GHz, and 1.55 THz. The backscattering measurements were collected as a function of polarization, incident angle, and frequency. The applicability of various rough surface scattering theories was determined for the different roughness regimes studied.

  18. Analysis of dielectric antennas by a diffraction method

    Science.gov (United States)

    Mahdjoubi, K.; Terret, C.

    1983-06-01

    Performance comparisons and assessment of the compatibility of microstrip patch antennas and leaky-wave dielectric antennas for millimeter wave communications are presented. The antennas are formed of scattering material, placed in the near field of the excitation source, and equipped with circular waveguides functioning in the fundamental mode. An integral formulation is devised for the diffraction field around the antennas with either homogeneous or composite structures. The calculations center around a singularity and are expressed by means of the Green function, which is solved by a method of moments technique involving point-segments. An approximate solution is defined for diffraction in the near field for a body of revolution, and experimental results are provided for the directivity of the radiation from a source in two planes of polarization. The calculations are applied to scattering by a dielectric body using the method of volumic equivalence, showing good agreement with experimental values, particularly when a good adaptation is made between the dielectric bodies and the waveguide source. The equivalence method is suggested to be suitable for modeling the diffraction field around heterogeneous antennas.

  19. Experimental study on surface modification of PET films under bipolar nanosecond-pulse dielectric barrier discharge in atmospheric air

    International Nuclear Information System (INIS)

    Highlights: • Homogeneous DBD is generated under bipolar nanosecond pulse in atmospheric air. • Effects of surface modification under homogeneous DBD are discussed. • Dielectric properties of the PET films are fully studied from relative dielectric constant εr, dielectric loss tangent tan δ and breakdown voltages Vb. • Oxygen-containing polar groups are considered to be the most essential reason for dielectric property changes. - Abstract: Dielectric barrier discharge (DBD) is widely used for surface modification of polymer films. In this paper, DBD characteristics under bipolar repetitive frequency nanosecond pulse in atmospheric air are studied and surface properties of polyethylene terephthalate films under homogeneous DBD and filamentary DBD modification are compared through scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and dielectric test equipment. It is found that the discharge is homogeneous when gap spacing d is less than 1.2 mm and filamentary when d is within the range of 3.0 mm to 5.8 mm. SEM pictures reveal that films under homogeneous DBD present a smooth surface while intensive “gully-like” etches appear on the surface of the films under filamentary DBD, which can result in local insulation defects and is disadvantageous to surface modification. It is found from the XPS analysis that a number of oxygen-containing polar groups are introduced onto the surface of the film modified by homogeneous DBD compared with the untreated one. Experimental results for dielectric properties indicate that the three parameters: relative dielectric constant εr, dielectric loss tangent tan δ and breakdown voltages Vb are all changed in different degree after surface modification. And possible reason for the phenomenon is discussed

  20. Bulk Viscosity of Interacting Hadrons

    OpenAIRE

    Wiranata, A.; M. Prakash

    2009-01-01

    We show that first approximations to the bulk viscosity $\\eta_v$ are expressible in terms of factors that depend on the sound speed $v_s$, the enthalpy, and the interaction (elastic and inelastic) cross section. The explicit dependence of $\\eta_v$ on the factor $(\\frac 13 - v_s^2)$ is demonstrated in the Chapman-Enskog approximation as well as the variational and relaxation time approaches. The interesting feature of bulk viscosity is that the dominant contributions at a given temperature ari...

  1. Bulk Viscosity of Interacting Hadrons

    CERN Document Server

    Wiranata, A

    2009-01-01

    We show that first approximations to the bulk viscosity $\\eta_v$ are expressible in terms of factors that depend on the sound speed $v_s$, the enthalpy, and the interaction (elastic and inelastic) cross section. The explicit dependence of $\\eta_v$ on the factor $(\\frac 13 - v_s^2)$ is demonstrated in the Chapman-Enskog approximation as well as the variational and relaxation time approaches. The interesting feature of bulk viscosity is that the dominant contributions at a given temperature arise from particles which are neither extremely nonrelativistic nor extremely relativistic. Numerical results for a model binary mixture are reported.

  2. Bulk and Interface effects on voltage linearity of ZrO2-SiO2 multilayered metal-insulator-metal capacitors for analog mixed-signal applications

    Science.gov (United States)

    Park, S. D.; Park, C.; Gilmer, D. C.; Park, H. K.; Kang, C. Y.; Lim, K. Y.; Burham, C.; Barnett, J.; Kirsch, P. D.; Tseng, H. H.; Jammy, R.; Yeom, G. Y.

    2009-07-01

    Quadratic voltage coefficient of capacitance (VCC) for ZrO2-SiO2 multilayered dielectric metal-insulator-metal capacitors depends strongly on the stacking sequence of the layered dielectrics. The quadratic VCC of an optimized SiO2/ZrO2/SiO2 stack and ZrO2/SiO2/ZrO2 stack were +42 and -1094 ppm/V2, respectively, despite the same total SiO2 and ZrO2 dielectric thickness in the stack. The observed difference in quadratic VCC depending on dielectric stacking sequence is explained by taking into account both the interface and bulk dielectric responses to the applied voltage.

  3. Heavy Quarkonium Production and Polarization

    Science.gov (United States)

    Kang, Zhong-Bo; Qiu, Jian-Wei; Sterman, George

    2012-03-01

    We present a perturbative QCD factorization formalism for the production of heavy quarkonia of large transverse momentum pT at collider energies, which includes both the leading-power (LP) and next-to-leading-power (NLP) contributions to the cross section in the mQ2/pT2 expansion for heavy quark mass mQ. We estimate fragmentation functions in the nonrelativistic QCD formalism and reproduce the bulk of the large enhancement found in explicit next-to-leading-order calculations in the color-singlet model. Heavy quarkonia produced from NLP channels prefer longitudinal polarization.

  4. A Simple Bipolar Jet Model for the Polarization of Core-Collapse Supernovae

    CERN Document Server

    Jeffery, D J

    2004-01-01

    We propose a bipolar jet model for supernova polarization. Light from the main component of the supernova (which we call the bulk supernova for short) scatters off electrons in the jets and is polarized: this polarized light is added to the direct emission from the bulk supernova and causes the overall supernova emission to be polarized. The motivation for the bipolar jet model is to resolve the potential paradox set by an analysis which suggests strong spherical symmetry for Type Ib supernovae and the expectation that Type Ib supernovae should be highly polarized in the continuum up to perhaps about 4 %. For the model we have derived simple, non-relativistic, approximate analytic formulae for relative amount of scattered flux and polarization. The polarization formula qualitatively reproduces two main features observed for at least some supernovae: (1) the rise to a polarization maximum and then decline with time; (2) the inverted P Cygni polarization profiles of lines. The model is strictly axisymmetric and...

  5. Raman Spectra of High-κ Dielectric Layers Investigated with Micro-Raman Spectroscopy Comparison with Silicon Dioxide

    Directory of Open Access Journals (Sweden)

    P. Borowicz

    2013-01-01

    Full Text Available Three samples with dielectric layers from high-κ dielectrics, hafnium oxide, gadolinium-silicon oxide, and lanthanum-lutetium oxide on silicon substrate were studied by Raman spectroscopy. The results obtained for high-κ dielectrics were compared with spectra recorded for silicon dioxide. Raman spectra suggest the similarity of gadolinium-silicon oxide and lanthanum-lutetium oxide to the bulk nondensified silicon dioxide. The temperature treatment of hafnium oxide shows the evolution of the structure of this material. Raman spectra recorded for as-deposited hafnium oxide are similar to the results obtained for silicon dioxide layer. After thermal treatment especially at higher temperatures (600°C and above, the structure of hafnium oxide becomes similar to the bulk non-densified silicon dioxide.

  6. Light-induced space-charge fields for the structuration of dielectric materials; Lichtinduzierte Raumladungsfelder zur Strukturierung dielektrischer Materialien

    Energy Technology Data Exchange (ETDEWEB)

    Eggert, H.A.

    2006-11-15

    Light-induced space-charge fields in lithium-niobate crystals are used for patterning of dielectric materials. This includes tailored ferroelectric domains in the bulk of the crystal, different sorts of micro and nanoparticles on a crystal surface, as well as poling of electrooptic chromophores. A stochastical model is introduced, which can describe the spatial inhomogeneous domain inversion. (orig.)

  7. Dielectric barrier discharges in analytical chemistry.

    Science.gov (United States)

    Meyer, C; Müller, S; Gurevich, E L; Franzke, J

    2011-06-21

    The present review reflects the importance of dielectric barrier discharges in analytical chemistry. Special about this discharge is-and in contrast to usual discharges with direct current-that the plasma is separated from one or two electrodes by a dielectric barrier. This gives rise to two main features of the dielectric barrier discharges; it can serve as dissociation and excitation device and as ionization mechanism, respectively. The article portrays the various application fields for dielectric barrier discharges in analytical chemistry, for example the use for elemental detection with optical spectrometry or as ionization source for mass spectrometry. Besides the introduction of different kinds of dielectric barrier discharges used for analytical chemistry from the literature, a clear and concise classification of dielectric barrier discharges into capacitively coupled discharges is provided followed by an overview about the characteristics of a dielectric barrier discharge concerning discharge properties and the ignition mechanism. PMID:21562672

  8. Structural and dielectric properties of CuO-doped SrTiO{sub 3} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Naidu, K. Chandra Babu, E-mail: chandrababu954@gmail.com; Sarmash, T. Sofi; Maddaiah, M.; Reddy, V. Narasimha; Subbarao, T. [Materials Science Lab, Department of Physics, S K University, Anantapur – 515003, A. P (India)

    2015-06-24

    Copper-doped SrTiO{sub 3} (ST) ceramic powders were processed by solid-state route diffusion (SRD) bulk preparation technique. We reported the effect of Cu{sup +2} ions on the dielectric response of ST and it established the substantial increase in dielectric constant (ε{sub r}) than undoped ST from 303K-673K and low loss (tanδ) for good dielectric applications. In respect of the electrical properties ac- activation energies were computed of range 0.089-0.319eV using lnσ Vs 1/T plots. The microstructure was examined with grain sizes 6-9µm of uniform distribution by field emission scanning electron microscope (FESEM). Some additional phases SrCu{sub 3}Ti{sub 4}O{sub 12} and TiO{sub 2} rutiles were detected by X-ray diffraction technique.

  9. The conductivity and dielectric behavior of solutions of bitumen in toluene

    Energy Technology Data Exchange (ETDEWEB)

    Chow, R.S.; Tse, D.L.; Takamura, K.

    1988-06-01

    Previous work on the conductivity and dielectric behavior of residual oil (the fraction remaining in the distillation tower) has suggested that the asphaltene fraction (pentane insolubles) was responsible for the conductivity behavior of solutions of this oil in organic solvents. In this work it is shown that the asphaltenes in heavy crude oils determine the conductivity behavior of solutions of the bulk oil in toluene, while the dielectric behavior is influenced by each component of the oil. The strong dependence of the conductivity on the asphaltene fraction makes it possible to determine the asphaltene content of a heavy crude oil by a conductimetric technique. The conductivity and dielectric behavior of crude oils and fractions of the crude oils, as well as the technique for determining the asphaltene content by conductivity will be presented.

  10. Structural and dielectric properties of CuO-doped SrTiO3 ceramics

    International Nuclear Information System (INIS)

    Copper-doped SrTiO3 (ST) ceramic powders were processed by solid-state route diffusion (SRD) bulk preparation technique. We reported the effect of Cu+2 ions on the dielectric response of ST and it established the substantial increase in dielectric constant (εr) than undoped ST from 303K-673K and low loss (tanδ) for good dielectric applications. In respect of the electrical properties ac- activation energies were computed of range 0.089-0.319eV using lnσ Vs 1/T plots. The microstructure was examined with grain sizes 6-9µm of uniform distribution by field emission scanning electron microscope (FESEM). Some additional phases SrCu3Ti4O12 and TiO2 rutiles were detected by X-ray diffraction technique

  11. Investigation of thickness effects on the dielectric constant barium strontium titanate thin films

    CERN Document Server

    Grattan, L J

    2002-01-01

    The collapse in dielectric constant at small thickness commonly observed in ferroelectric thin films was measured and investigated in barium strontium titanate (Ba sub 0 sub . sub 5 Sr sub 0 sub . sub 5 TiO sub 3). The possible mechanisms responsible for this effect are reviewed. Functional measurements were performed on BST thin films, of 7.5 to 950 nm, by incorporating them into capacitor structures with bottom electrodes of strontium ruthenate (SRO) and thermally- evaporated Au top electrodes. A discussion on thin film growth considerations, optimal PLD conditions and the measurement techniques employed in the project is presented. The experimentally determined dielectric constant - thickness profile was fitted using the series capacitor model assuming low dielectric constant interfacial layers in series with the bulk. Consideration of the case where the combined 'dead layer' thickness was close to the total BST thickness revealed that, for this system, the total 'dead layer' thickness had to be less than ...

  12. Two-phase mixed media dielectric with macro dielectric beads for enhancing resistivity and breakdown strength

    Science.gov (United States)

    Falabella, Steven; Meyer, Glenn A; Tang, Vincent; Guethlein, Gary

    2014-06-10

    A two-phase mixed media insulator having a dielectric fluid filling the interstices between macro-sized dielectric beads packed into a confined volume, so that the packed dielectric beads inhibit electro-hydrodynamically driven current flows of the dielectric liquid and thereby increase the resistivity and breakdown strength of the two-phase insulator over the dielectric liquid alone. In addition, an electrical apparatus incorporates the two-phase mixed media insulator to insulate between electrical components of different electrical potentials. And a method of electrically insulating between electrical components of different electrical potentials fills a confined volume between the electrical components with the two-phase dielectric composite, so that the macro dielectric beads are packed in the confined volume and interstices formed between the macro dielectric beads are filled with the dielectric liquid.

  13. Bulk charges in eleven dimensions

    Science.gov (United States)

    Hawking, S. W.; Taylor-Robinson, M. M.

    1998-07-01

    Eleven dimensional supergravity has electric type currents arising from the Chern-Simon and anomaly terms in the action. However the bulk charge integrates to zero for asymptotically flat solutions with topological trivial spatial sections. We show that by relaxing the boundary conditions to generalisations of the ALE and ALF boundary conditions in four dimensions one can obtain static solutions with a bulk charge. Solutions involving anomaly terms preserve between 1/16 and 1/4 of the supersymmetries but Chern-Simons fluxes generally break all of the remaining supersymmetry. One can introduce membranes with the same sign of charge into these backgrounds. This raises the possibility that these generalized membranes might decay quantum mechanically to leave just a bulk distribution of charge. Alternatively and more probably, a bulk distribution of charge can decay into a collection of singly charged membranes. Dimensional reductions of these solutions lead to novel representations of extreme black holes in four dimensions with up to four charges. We discuss how the eleven-dimensional Kaluza-Klein monopole wrapped around a space with non-zero first Pontryagin class picks up an electric charge proportional to the Pontryagin number.

  14. Bulk viscosity and deflationary universes

    CERN Document Server

    Lima, J A S; Waga, I

    2007-01-01

    We analyze the conditions that make possible the description of entropy generation in the new inflationary model by means of a nearequilibrium process. We show that there are situations in which the bulk viscosity cannot describe particle production during the coherent field oscillations phase.

  15. Longitudinal bulk acoustic mass sensor

    DEFF Research Database (Denmark)

    Hales, Jan Harry; Teva, Jordi; Boisen, Anja;

    2009-01-01

    A polycrystalline silicon longitudinal bulk acoustic cantilever is fabricated and operated in air at 51 MHz. A mass sensitivity of 100 Hz/fg (1 fg=10(-15) g) is obtained from the preliminary experiments where a minute mass is deposited on the device by means of focused ion beam. The total noise i...

  16. An experimental study of electrical and dielectric properties of consolidated clayey materials

    International Nuclear Information System (INIS)

    This study is devoted to the electrical and dielectric properties of consolidated clays. A better understanding of the conduction and polarization phenomena in clays is necessary to better interpret in situ measurements in terms of water saturation and texture. An experimental study was carried out on synthetic clay samples (kaolinite and smectite) compacted with various water contents, porosities and mineralogical compositions, on a large frequency range, using three laboratory setups. The electrical properties of natural argillites (from ANDRA) were then investigated. We found that the response of the synthetic samples is mainly controlled by water content on the whole frequency range; two polarization phenomena were observed, which were related to the Maxwell-Wagner polarization and the electrical double layer polarization around the clay particles. The electrical response of argillites is more complex; it is controlled by water content but also by the microstructure of the rock. In these rocks, the electrical and dielectric anisotropies are high; anisotropy was also measured for the synthetic clays. The existing models explain the high frequency limit of the dielectric permittivity of the clayey materials, but the low frequency part of the spectra (≤1 MHz) needs theoretical developments. (author)

  17. First-principles study of optical properties of α-CuSe/klockmannite: Bulk and nano-layers

    Energy Technology Data Exchange (ETDEWEB)

    Shojaei, Ali Reza, E-mail: Ali.r.shojaei@gmail.com [Department of Physics, Lenjan Branch, Islamic Azad University, Isfahan (Iran, Islamic Republic of); Faculty of Science, Physics Department, University of Isfahan, 81746-73441 Isfahan (Iran, Islamic Republic of); Vaez, Aminollah; Nourbakhsh, Zahra; Madaniyan, Zeynab Sadat [Faculty of Science, Physics Department, University of Isfahan, 81746-73441 Isfahan (Iran, Islamic Republic of)

    2014-04-01

    The optical properties of α-CuSe bulk and its nano-layers (NLs) have been studied by the first principles theoretical study in the framework of density functional theory. These properties are calculated with regard to dielectric function, refractive index, extinction coefficient, reflection coefficient, absorption coefficient, energy-loss function, and optical conductivity. To create NLs, two different thicknesses through CuSe bulk are chosen in the (0001) direction as the first and second thicknesses. The former thickness is divided into six different NLs with variant alternations. These NLs have the same chemical composition and are structural isomers. Among the NLs, the optical properties of the most stable NL and its double thickness are calculated and compared with the bulk state. The imaginary part of dielectric function has a main peak at low energies because α-CuSe is a conductive compound in the bulk state. The electronic structure of NLs shows that they have remained conductive in x (or y) direction, but they interestingly have a dielectric behavior with an ultra-low electrical conductivity in z direction. The optical curves in the bulk and NLs show the anisotropic feature between x and z directions. In the range of infrared to red light, the bulk refractive index, n{sub z}(ω), is very large, about 6, while n{sub x}(ω) is about 3. Results show that the NLs have wide absorption curves in the range of solar spectrum from infrared to ultraviolet. - Highlights: • Optical properties of α-CuSe bulk and its nano-layers (NLs) are studied • Our calculations are performed within framework of Density functional theory using full potential method. • The NLs stabilities and thickness effect on their optical properties are discussed. • Bulk and NLs optical curves show anisotropic feature between x (or y) and z directions. • NLs showed conductivity in x (or y) direction but ultra-low conductivity in z direction.

  18. DNA-nucleobases: gate dielectric/passivation layer for flexible GFET-based sensor applications

    Science.gov (United States)

    Williams, Adrienne D.; Ouchen, Fahima; Kim, Steve S.; Elhamri, Said; Naik, Rajesh R.; Grote, James

    2015-09-01

    The main goal of this research was to maintain the bulk charge carrier mobility of graphene, after deposition of the gate dielectric layer used for making transistor devices. The approach was introducing a thin film of deoxyribonucleic acid (DNA) nucleobase purine guanine, deposited by physical vapor deposition (PVD), onto layers of graphene that were transferred onto various flexible substrates. Several test platforms were fabricated with guanine as a standalone gate dielectric, as the control, and guanine as a passivation layer between the graphene and PMMA. It was found that the bulk charge carrier mobility of graphene was best maintained and most stable using guanine as a passivation layer between the graphene and PMMA. Other transport properties, such as charge carrier concentration, conductivity type and electrical resistivity were investigated as well. This is an important first step to realizing high performance graphene-based transistors that have potential use in bio and environmental sensors, computer-processing and electronics.

  19. Polymerisationseigenschaften von Bulk-Fill Kompositen

    OpenAIRE

    Maier, Eva

    2015-01-01

    Hintergrund und Ziele: Untersuchung der Polymerisationseigenschaften von Bulk-Fill Kompositen bzgl. Konversionsrate (degree of conversion = DC), Vickers-Härte (HV), Polymerisationsschrumpfungsstress (PSS) und Polymerisationsvolumenschrumpfung (PVS) im Vergleich zu konventionellen Kompositen. Material und Methode: Untersucht wurden die Bulk-Fill Komposite Filtek Bulk Fill Flowable (FBF, 3M ESPE, Seefeld), Surefil Smart Dentin Replacement (SDR, Dentsply, Konstanz), Tetric EvoCeram Bulk Fill...

  20. Dielectric properties of crystalline organic molecular films in the limit of zero overlap

    Energy Technology Data Exchange (ETDEWEB)

    D’Avino, Gabriele, E-mail: gabriele.davino@gmail.com [Laboratory for Chemistry of Novel Materials, University of Mons, Place du Parc 20, BE-7000 Mons, Belgium and Department of Physics, University of Liège, Allée du 6 Août 17, BE-4000 Liège (Belgium); Vanzo, Davide; Soos, Zoltán G., E-mail: soos@princeton.edu [Department of Chemistry, Princeton University, Princeton, New Jersey 08544 (United States)

    2016-01-21

    We present the calculation of the static dielectric susceptibility tensor and dipole field sums in thin molecular films in the well-defined limit of zero intermolecular overlap. Microelectrostatic and charge redistribution approaches are applied to study the evolution of dielectric properties from one to a few molecular layers in films of different conjugated molecules with organic electronics applications. Because of the conditional convergence of dipolar interactions, dipole fields depend on the shape of the sample and different values are found in the middle layer of a thick film and in the bulk. The shape dependence is eliminated when depolarization is taken into account, and the dielectric tensor of molecular films converges to the bulk limit within a few molecular layers. We quantify the magnitude of surface effects and interpret general trends among different systems in terms of molecular properties, such as shape, polarizability anisotropy, and supramolecular organization. A connection between atomistic models for molecular dielectrics and simpler theories for polarizable atomic lattices is also provided.