Science.gov

Sample records for dielectric constant material

  1. Porous low dielectric constant materials for microelectronics.

    PubMed

    Baklanov, Mikhail R; Maex, Karen

    2006-01-15

    Materials with a low dielectric constant are required as interlayer dielectrics for the on-chip interconnection of ultra-large-scale integration devices to provide high speed, low dynamic power dissipation and low cross-talk noise. The selection of chemical compounds with low polarizability and the introduction of porosity result in a reduced dielectric constant. Integration of such materials into microelectronic circuits, however, poses a number of challenges, as the materials must meet strict requirements in terms of properties and reliability. These issues are the subject of the present paper.

  2. Negative Dielectric Constant Material Based on Ion Conducting Materials

    NASA Technical Reports Server (NTRS)

    Gordon, Keith L. (Inventor); Kang, Jin Ho (Inventor); Park, Cheol (Inventor); Lillehei, Peter T. (Inventor); Harrison, Joycelyn S. (Inventor)

    2014-01-01

    Metamaterials or artificial negative index materials (NIMs) have generated great attention due to their unique and exotic electromagnetic properties. One exemplary negative dielectric constant material, which is an essential key for creating the NIMs, was developed by doping ions into a polymer, a protonated poly(benzimidazole) (PBI). The doped PBI showed a negative dielectric constant at megahertz (MHz) frequencies due to its reduced plasma frequency and an induction effect. The magnitude of the negative dielectric constant and the resonance frequency were tunable by doping concentration. The highly doped PBI showed larger absolute magnitude of negative dielectric constant at just above its resonance frequency than the less doped PBI.

  3. Thermal conductivity and dielectric constant of silicate materials

    NASA Technical Reports Server (NTRS)

    Simon, I.; Wechsler, A. E.

    1968-01-01

    Report on the thermal conductivity and dielectric constant of nonmetallic materials evaluates the mechanisms of heat transfer in evacuated silicate powders and establishes the complex dielectric constant of these materials. Experimental measurements and results are related to postulated lunar surface materials.

  4. Novel Materials with Effective Super Dielectric Constants for Energy Storage

    NASA Astrophysics Data System (ADS)

    Cortes, Francisco Javier Quintero; Phillips, Jonathan

    2015-05-01

    To test a theory of the recently discovered phenomenon of super dielectric behavior at very low frequency, the dielectric constants of several `pastes', composed of porous alumina powders filled to the point of incipient wetness with water containing dissolved sodium chloride, were measured. The effective dielectric low frequency constants of some of the pastes were greater than 1010, dramatically higher than that of any material ever reported. Moreover, the total energy density reported for one capacitor generated with NaCl-based super dielectric material is marginally higher than found in any prior report. These results are consistent with this recently postulated model of low frequency super dielectric behavior in porous, non-conductive materials saturated with ion-containing liquids: upon the application of an electric field, ions dissolved in the saturating liquid contained in the pores will travel to the ends of pore-filling liquid droplets creating giant dipoles. The fields of these giant dipoles oppose the applied field, reducing the net field created per unit of charge on the capacitor plates, effectively increasing charge/voltage ratio, hence capacitance. This is simply a version of the theory of `polarizable media' found in most classic texts on electromagnetism. Other observations reported here include (1) the impact of ion concentration on dielectric values, (2) a maximum voltage similar to that associated with the electrical breakdown of water, (3) the loss of capacitance upon drying, (4) the recovery of capacitance upon the addition of water to a dry super dielectric material, and (5) the linear relationship between capacitance and inverse thickness. All observations are consistent with the earlier proposed model of the super dielectric phenomenon. An extrapolation of results suggests this technology can lead to energy density greater than the best lithium-ion battery.

  5. Technique for measuring the dielectric constant of thin materials

    NASA Technical Reports Server (NTRS)

    Sarabandi, K.; Ulaby, F. T.

    1988-01-01

    A practical technique for measuring the dielectric constant of vegetation leaves and similarly thin materials is presented. A rectangular section of the leaf is placed in the tranverse plane in a rectangular waveguide and the magnitude and phase of the reflection coefficient are measured over the desired frequency band using a vector network analyzer. By treating the leaf as an infinitesimally thin resistive sheet, an explicit expression for its dielectric constant is obtained in terms of the reflection coefficient. Because of the thin-sheet approximation, however, this approach is valid only at frequencies below 1.5 GHz. To extend the technique to higher frequencies, higher order approximations are derived and their accuracies are compared to the exact dielectric-slab solution. For a material whose thickness is 0.5 mm or less, the proposed technique was found to provide accurate values of its dielectric constant up to frequencies of 12 GHz or higher. The technique was used to measure the 8 to 12 GHz dielectric spectrum for vegetation leaves, teflon and rock samples.

  6. New high dielectric constant materials for tailoring the B1+ distribution at high magnetic fields.

    PubMed

    Haines, K; Smith, N B; Webb, A G

    2010-04-01

    The spatial distribution of electromagnetic fields within the human body can be tailored using external dielectric materials. Here, we introduce a new material with high dielectric constant, and also low background MRI signal. The material is based upon metal titanates, which can be made into a geometrically-formable suspension in de-ionized water. The material properties of the suspension are characterized from 100 to 400 MHz. Results obtained at 7 T show a significant increase in image intensity in areas such as the temporal lobe and base of the brain with the new material placed around the head, and improved performance compared to purely water-based gels.

  7. Sol-gel composite material characteristics caused by different dielectric constant sol-gel phases

    NASA Astrophysics Data System (ADS)

    Kimoto, Keisuke; Matsumoto, Makoto; Kaneko, Tsukasa; Kobayashi, Makiko

    2016-07-01

    Ultrasonic transducers prepared by a sol-gel composite method have been investigated in the field of nondestructive testing (NDT). Sol-gel composite materials could be ideal piezoelectric materials for ultrasonic transducer applications in the NDT field, and a new sol-gel composite with desirable characteristics has been developed. Three kinds of sol-gel composite materials composed of different dielectric constant sol-gel phases, Pb(Zr,Ti)O3 (PZT), Bi4Ti3O12 (BiT), and BaTiO3 (BT), and the same piezoelectric powder phase, PbTiO3 (PT), were fabricated and their properties were compared quantitatively. As a result, the PT/BT, sol-gel composite with the highest dielectric constant sol-gel phase showed the highest d 33 and signal strength. In addition, only PT/BT was successfully poled by room-temperature corona poling with reasonable signal strength.

  8. Dielectric Constant of Suspensions

    NASA Astrophysics Data System (ADS)

    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.

  9. Novel Characterization Method of Ions in Liquid Crystal Materials by Complex Dielectric Constant Measurements

    NASA Astrophysics Data System (ADS)

    Sawada, Atsushi; Tarumi, Kazuaki; Naemura, Shohei

    1999-03-01

    The frequency dependence of the complex dielectric constant of liquid crystal materials doped with tetra-n-butylammonium iodide (TBAI) is investigated in the low-frequency region, and the experimental results are analyzed in terms of space charge polarization. The contribution from an electric double layer is also taken into consideration in the analysis. By means of curve fitting utilizing theoretical expressions of the space charge polarization, five sets of diffusion coefficient and density values are obtained for mobile ions. It is confirmed by experiments on the temperature dependence that five kinds of ions follow Walden's rule, and verified from the viewpoint of ion radii that two of the five kinds of ions are TBA+ and I-. The frequency-dependent dielectric properties, which are characteristic of the behaviors of ions, can be well explained by this study and the analytical method introduced here is considered to be powerful for the evaluation of the attributes of mobile ions.

  10. Two Layer Magnetodielectric Metamaterial with Enhanced Dielectric Constant as a New Ferrite Like Material

    NASA Astrophysics Data System (ADS)

    Zouganelis, Georgios; Rybin, Oleg

    2006-11-01

    In this study, we present large enhancement of effective dielectric constant of magnetodielectric metamaterials made from two layers of parallel periodic non-magnetized iron wires embedded inside dielectric (wax), in two orientations of them, relative to the incident electromagnetic field. This kind of enhancement is predicted by finite difference time domain (FDTD) method electromagnetic simulations made for infinite size metamaterials of same unit cell and same electromagnetic wave’s geometry of incidence. In this model, the complex internal constants were estimated from the calculated complex S-parameters by using Ross-Nicolson method. The validity of our prediction was tested, from comparison of calculated S-parameters with experimental ones measured on a sample made by rapid prototyping, using a modified strip transmission line method. The dielectric enhancement was found to be about 500%, as it was expected from simulations. Applicability of this family of metamaterials to ferrites like applications is discussed.

  11. Dielectric technique to measure the twist elastic constant of liquid crystals: the case of a bent-core material.

    PubMed

    Salamon, P; Eber, N; Seltmann, J; Lehmann, M; Gleeson, J T; Sprunt, S; Jákli, A

    2012-06-01

    The effect of director pretilt on the twist magnetic Fréedericksz transition of nematics was investigated in a planar cell. The director configuration was calculated as a function of magnetic inductance. The dielectric and optical response of the nematic liquid crystal was numerically modeled. A dielectric measurement method for determining the elastic constant K_{22} is presented. The influence of the conditions for the Mauguin effect is discussed. The theoretical predictions were confirmed by our experiments. Experimental data for all elastic constants of a bent-core nematic material are presented and discussed.

  12. Core@Double-Shell Structured Nanocomposites: A Route to High Dielectric Constant and Low Loss Material.

    PubMed

    Huang, Yanhui; Huang, Xingyi; Schadler, Linda S; He, Jinliang; Jiang, Pingkai

    2016-09-28

    This work reports the advances of utilizing a core@double-shell nanostructure to enhance the electrical energy storage capability and suppress the dielectric loss of polymer nanocomposites. Two types of core@double-shell barium titanate (BaTiO3) matrix-free nanocomposites were prepared using a surface initiated atom transfer radical polymerization (ATRP) method to graft a poly(2-hydroxylethyle methacrylate)-block-poly(methyl methacrylate) and sodium polyacrylate-block-poly(2-hydroxylethyle methacrylate) block copolymer from BaTiO3 nanoparticles. The inner shell polymer is chosen to have either high dielectric constant or high electrical conductivity to provide large polarization, while the encapsulating outer shell polymer is chosen to be more insulating as to maintain a large resistivity and low loss. Finite element modeling was conducted to investigate the dielectric properties of the fabricated nanocomposites and the relaxation behavior of the grafted polymer. It demonstrates that confinement of the more conductive (lossy) phase in this multishell nanostructure is the key to achieving a high dielectric constant and maintaining a low loss. This promising multishell strategy could be generalized to a variety of polymers to develop novel nanocomposites.

  13. Short-length carbon nanotubes as building blocks for high dielectric constant materials in the terahertz range

    NASA Astrophysics Data System (ADS)

    Shuba, M. V.; Paddubskaya, A. G.; Kuzhir, P. P.; Maksimenko, S. A.; Flahaut, E.; Fierro, V.; Celzard, A.; Valusis, G.

    2017-03-01

    Due to the high polarizability of finite-length carbon nanotubes (CNTs) in the quasi-static regime, they can be considered as building blocks for the fabrication of high dielectric constant material. Our theoretical estimations, based on an effective medium approach and solutions of a boundary value problem for individual CNT, predict that composite materials comprising short-length CNTs can have very high dielectric constants (up to 300) and low dielectric loss tangents (below 0.03) in the terahertz range. In order to prove this, 500–1000 nm thick films comprising single- and multi-walled CNTs of both long (0.5–2 μm) and short (0.1–0.4 μm) lengths have been fabricated. The analysis, based on the time-domain terahertz spectroscopy in the range 0.2–1.0 THz, demonstrated a decrease in the dielectric loss tangents of the CNT-based materials with a reduction in CNT length. In the terahertz range, the films comprising short-length CNTs had a relative effective permittivity with a large real part (25–136) and dielectric loss tangent (0.35–0.60).

  14. Dielectric-constant gas thermometry

    NASA Astrophysics Data System (ADS)

    Gaiser, Christof; Zandt, Thorsten; Fellmuth, Bernd

    2015-10-01

    The principles, techniques and results from dielectric-constant gas thermometry (DCGT) are reviewed. Primary DCGT with helium has been used for measuring T-T90 below the triple point of water (TPW), where T is the thermodynamic temperature and T90 is the temperature on the international temperature scale of 1990 (ITS-90), and, in an inverse regime with T as input quantity, for determining the Boltzmann constant at the TPW. Furthermore, DCGT allows the determination of several important material properties including the polarizability of neon and argon as well as the virial coefficients of helium, neon, and argon. With interpolating DCGT (IDCGT), the ITS-90 has been approximated in the temperature range from 4 K to 25 K. An overview and uncertainty budget for each of these applications of DCGT is provided, accompanied by corroborating evidence from the literature or, for IDCGT, a CIPM key comparison.

  15. Laboratory measurement of the complex dielectric constant of soils

    NASA Technical Reports Server (NTRS)

    Wiebe, M. L.

    1971-01-01

    The dielectric constant of a material is an extremely important parameter when considering passive radiometric remote sensing applications. This is because the emitted energy measured by a microwave radiometer is dependent on the dielectric constant of the surface being scanned. Two techniques of measuring dielectric constants are described. The first method involves a dielectric located in air. The second method uses basically the same theoretical approach, but the dielectric under consideration is located inside a section of waveguide.

  16. Boron Nitride Nanotube Mat as a Low- k Dielectric Material with Relative Dielectric Constant Ranging from 1.0 to 1.1

    NASA Astrophysics Data System (ADS)

    Hong, Xinghua; Wang, Daojun; Chung, D. D. L.

    2016-01-01

    This paper reports that a boron nitride nanotube (BNNT) mat containing air and 1.4 vol.% BNNTs is a low- k dielectric material for microelectronic packaging, exhibiting relative dielectric constant of 1.0 to 1.1 (50 Hz to 2 MHz) and elastic modulus of 10 MPa. The mat is prepared by compacting BNNTs at 5.8 kPa. This paper also presents measurements of the dielectric properties of BNNTs (mostly multiwalled). The relative dielectric constant of the BNNT solid in the mat decreases with increasing frequency, with attractively low values ranging from 3.0 to 6.2; the alternating-current (AC) electrical conductivity increases with increasing frequency, with attractively low values ranging from 10-10 S/m to 10-6 S/m and an approximately linear relationship between log conductivity and log frequency. The specific contact capacitance of the interface between BNNTs and the electrical contact decreases with increasing frequency, with attractively high values ranging from 1.6 μF/m2 to 2.3 μF/m2. The AC electrical resistivity of the BNNT-contact interface decreases with increasing frequency, with high values ranging from 0.14 MΩ cm2 to 440 MΩ cm2.

  17. Voltage sensor and dielectric material

    DOEpatents

    Yakymyshyn, Christopher Paul; Yakymyshyn, Pamela Jane; Brubaker, Michael Allen

    2006-10-17

    A voltage sensor is described that consists of an arrangement of impedance elements. The sensor is optimized to provide an output ratio that is substantially immune to changes in voltage, temperature variations or aging. Also disclosed is a material with a large and stable dielectric constant. The dielectric constant can be tailored to vary with position or direction in the material.

  18. Effect of UV curing time on physical and electrical properties and reliability of low dielectric constant materials

    SciTech Connect

    Kao, Kai-Chieh; Cheng, Yi-Lung; Chang, Wei-Yuan; Chang, Yu-Min; Leu, Jihperng

    2014-11-01

    This study comprehensively investigates the effect of ultraviolet (UV) curing time on the physical, electrical, and reliability characteristics of porous low-k materials. Following UV irradiation for various periods, the depth profiles of the chemical composition in the low-k dielectrics were homogeneous. Initially, the UV curing process preferentially removed porogen-related CH{sub x} groups and then modified Si-CH{sub 3} and cage Si-O bonds to form network Si-O bonds. The lowest dielectric constant (k value) was thus obtained at a UV curing time of 300 s. Additionally, UV irradiation made porogen-based low-k materials hydrophobic and to an extent that increased with UV curing time. With a short curing time (<300 s), porogen was not completely removed and the residues degraded reliability performance. A long curing time (>300 s) was associated with improved mechanical strength, electrical performance, and reliability of the low-k materials, but none of these increased linearly with UV curing time. Therefore, UV curing is necessary, but the process time must be optimized for porous low-k materials on back-end of line integration in 45 nm or below technology nodes.

  19. Capacitive Cells for Dielectric Constant Measurement

    ERIC Educational Resources Information Center

    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.

  20. The electro-mechanical phase transition of Gent model dielectric elastomer tube with two material constants

    NASA Astrophysics Data System (ADS)

    Liu, Liwu; Luo, Xiaojian; Fei, Fan; Wang, Yixing; Leng, Jinsong; Liu, Yanju

    2013-04-01

    Applied to voltage, a dielectric elastomer membrane may deform into a mixture of two states under certain conditions. One of which is the flat state and the other is the wrinkled state. In the flat state, the membrane is relatively thick with a small area, while on the contrary, in the wrinkled state, the membrane is relatively thin with a large area. The coexistence of these two states may cause the electromechanical phase transition of dielectric elastomer. The phase diagram of idea dielectric elastomer membrane under unidirectional stress and voltage inspired us to think about the liquid-to-vapor phase transition of pure substance. The practical working cycle of a steam engine includes the thermodynamical process of liquid-to-vapor phase transition, the fact is that the steam engine will do the maximum work if undergoing the phase transition process. In this paper, in order to consider the influence of coexistent state of dielectric elastomer, we investigate the homogeneous deformation of the dielectric elastomer tube. The theoretical model is built and the relationship between external loads and stretch are got, we can see that the elastomer tube experiences the coexistent state before reaching the stretching limit from the diagram. We think these results can guide the design and manufacture of energy harvesting equipments.

  1. Material with high dielectric constant, low dielectric loss, and good mechanical and thermal properties produced using multi-wall carbon nanotubes wrapped with poly(ether sulphone) in a poly(ether ether ketone) matrix

    NASA Astrophysics Data System (ADS)

    Zhang, Shuling; Wang, Hongsong; Wang, Guibin; Jiang, Zhenhua

    2012-07-01

    A material with high dielectric constant, low dielectric loss, and good mechanical and thermal properties was produced using multi-wall carbon nanotubes (MWCNTs) wrapped with poly(ether sulphone) (PES) dispersed in a poly(ether ether ketone) (PEEK) matrix. The material was fabricated using melt-blending, and MWCNT/PEEK composites show different degrees of improvement in the measured dielectric, mechanical, and thermal properties as compared to pure PEEK. This is attributed to the high conductivity of MWCNTs, the effect of wrapping MWCNTs with PES, the good dispersion of the wrapped MWCNTs in PEEK, and the strong interfacial adhesion between the wrapped MWCNTs and the PEEK.

  2. Dielectric constant of water in the interface

    NASA Astrophysics Data System (ADS)

    Dinpajooh, Mohammadhasan; Matyushov, Dmitry V.

    2016-07-01

    We define the dielectric constant (susceptibility) that should enter the Maxwell boundary value problem when applied to microscopic dielectric interfaces polarized by external fields. The dielectric constant (susceptibility) of the interface is defined by exact linear-response equations involving correlations of statistically fluctuating interface polarization and the Coulomb interaction energy of external charges with the dielectric. The theory is applied to the interface between water and spherical solutes of altering size studied by molecular dynamics (MD) simulations. The effective dielectric constant of interfacial water is found to be significantly lower than its bulk value, and it also depends on the solute size. For TIP3P water used in MD simulations, the interface dielectric constant changes from 9 to 4 when the solute radius is increased from ˜5 to 18 Å.

  3. Let's Measure the Dielectric Constant of a Piece of Paper!

    ERIC Educational Resources Information Center

    Karlow, Edwin A.

    1991-01-01

    Described is a simple circuit with which students can observe the effect of common dielectric materials in a capacitor and measure the dielectric constant of a piece of paper. Discussed are the theory, apparatus construction, and experimental procedures for this activity. (CW)

  4. Low-Dielectric-Constant Polyimide Fibers

    NASA Technical Reports Server (NTRS)

    Dorogy, William E., Jr.; Proctor, K. Mason; St. Clair, Anne K.

    1994-01-01

    In experiments performed at NASA Langley Research Center, low-dielectric-constant polyimide fibers produced by use of resin extrusion. These fibers also have high thermal stability and good tensile properties. Useful in industrial and aerospace applications in which fibers required to have dielectric constants less than 3, high thermal stability, and tensile properties in range of those of standard textile fibers. Potential applications include use in printed circuit-boards and in aircraft composites.

  5. Dielectric constants of soils at microwave frequencies

    NASA Technical Reports Server (NTRS)

    Geiger, F. E.; Williams, D.

    1972-01-01

    A knowledge of the complex dielectric constant of soils is essential in the interpretation of microwave airborne radiometer data of the earth's surface. Measurements were made at 37 GHz on various soils from the Phoenix, Ariz., area. Extensive data have been obtained for dry soil and soil with water content in the range from 0.6 to 35 percent by dry weight. Measurements were made in a two arm microwave bridge and results were corrected for reflections at the sample interfaces by solution of the parallel dielectric plate problem. The maximum dielectric constants are about a factor of 3 lower than those reported for similar soils at X-band frequencies.

  6. Spectral curve fitting of dielectric constants

    NASA Astrophysics Data System (ADS)

    Ruzi, M.; Ennis, C.; Robertson, E. G.

    2017-01-01

    Optical constants are important properties governing the response of a material to incident light. It follows that they are often extracted from spectra measured by absorbance, transmittance or reflectance. One convenient method to obtain optical constants is by curve fitting. Here, model curves should satisfy Kramer-Kronig relations, and preferably can be expressed in closed form or easily calculable. In this study we use dielectric constants of three different molecular ices in the infrared region to evaluate four different model curves that are generally used for fitting optical constants: (1) the classical damped harmonic oscillator, (2) Voigt line shape, (3) Fourier series, and (4) the Triangular basis. Among these, only the classical damped harmonic oscillator model strictly satisfies the Kramer-Kronig relation. If considering the trade-off between accuracy and speed, Fourier series fitting is the best option when spectral bands are broad while for narrow peaks the classical damped harmonic oscillator and the Triangular basis fitting model are the best choice.

  7. High dielectric constant polymer nanocomposites for embedded capacitor applications

    NASA Astrophysics Data System (ADS)

    Lu, Jiongxin

    Driven by ever growing demands of miniaturization, increased functionality, high performance and low cost for microelectronic products and packaging, embedded passives will be one of the key emerging techniques for realizing the system integration which offer various advantages over traditional discrete components. Novel materials for embedded capacitor applications are in great demand, for which a high dielectric constant ( k), low dielectric loss and process compatibility with printed circuit boards are the most important prerequisites. To date, no available material satisfies all these prerequisites and research is needed to develop materials for embedded capacitor applications. Conductive filler/polymer composites are likely candidate material because they show a dramatic increase in their dielectric constant close to the percolation threshold. One of the major hurdles for this type of high-k composites is the high dielectric loss inherent in these systems. In this research, material and process innovations were explored to design and develop conductive filler/polymer nanocomposites based on nanoparticles with controlled parameters to fulfill the balance between sufficiently high-k and low dielectric loss, which satisfied the requirements for embedded capacitor applications. This work involved the synthesis of the metal nanoparticles with different parameters including size, size distribution, aggregation and surface properties, and an investigation on how these varied parameters impact the dielectric properties of the high-k nanocomposites incorporated with these metal nanoparticles. The dielectric behaviors of the nanocomposites were studied systematically over a range of frequencies to determine the dependence of dielectric constant, dielectric loss tangent and dielectric strength on these parameters.

  8. High Dielectric Constant Polymer Film Capacitors (PREPRINT)

    DTIC Science & Technology

    2010-02-01

    film, and the test of our first generation prototype capacitors . High-K Polymeric Dielectrics Commercial polypropylene (PP) capacitor film has a...1994). 2. Maurizio Rabuffi and Guido Picci, “Status Quo and Future Prospects for Metallized Polypropylene Energy Storage Capacitors ”, IEEE Trans...AFRL-RZ-WP-TP-2010-2126 HIGH DIELECTRIC CONSTANT POLYMER FILM CAPACITORS (PREPRINT) Shihai Zhang, Brian Zellers, Dean Anderson, Paul

  9. Large dielectric constant, high acceptor density, and deep electron traps in perovskite solar cell material CsGeI3

    DOE PAGES

    Ming, Wenmei; Shi, Hongliang; Du, Mao-Hua

    2016-01-01

    Here we report that many metal halides that contain cations with the ns2 electronic configuration have recently been discovered as high-performance optoelectronic materials. In particular, solar cells based on lead halide perovskites have shown great promise as evidenced by the rapid increase of the power conversion efficiency. In this paper, we show density functional theory calculations of electronic structure and dielectric and defect properties of CsGeI3 (a lead-free halide perovskite material). The potential of CsGeI3 as a solar cell material is assessed based on its intrinsic properties. We find anomalously large Born effective charges and a large static dielectric constantmore » dominated by lattice polarization, which should reduce carrier scattering, trapping, and recombination by screening charged defects and impurities. Defect calculations show that CsGeI3 is a p-type semiconductor and its hole density can be modified by varying the chemical potentials of the constituent elements. Despite the reduction of long-range Coulomb attraction by strong screening, the iodine vacancy in CsGeI3 is found to be a deep electron trap due to the short-range potential, i.e., strong Ge–Ge covalent bonding, which should limit electron transport efficiency in p-type CsGeI3. This is in contrast to the shallow iodine vacancies found in several Pb and Sn halide perovskites (e.g., CH3NH3PbI3, CH3NH3SnI3, and CsSnI3). The low-hole-density CsGeI3 may be a useful solar absorber material but the presence of the low-energy deep iodine vacancy may significantly reduce the open circuit voltage of the solar cell. Still, on the other hand, CsGeI3 may be used as an efficient hole transport material in solar cells due to its small hole effective mass, the absence of low-energy deep hole traps, and the favorable band offset with solar absorber materials such as dye molecules and CH3NH3PbI3.« less

  10. Optimal Super Dielectric Material

    DTIC Science & Technology

    2015-09-01

    electrically insulating materials filled to the point of incipient wetness (paste consistency) with liquids containing dissolved ions. This work...109. This strongly supports the fundamental hypothesis of SDM: In the presence of an electric field any electrically insulating, porous material...ABSTRACT The results of this study establish that powder-based super dielectric materials (SDM) are a large family of porous electrically

  11. Effect of vacuum-ultraviolet irradiation on the dielectric constant of low-k organosilicate dielectrics

    SciTech Connect

    Zheng, H.; Shohet, J. L.; Ryan, E. T.; Nishi, Y.

    2014-11-17

    Vacuum ultraviolet (VUV) irradiation is generated during plasma processing in semiconductor fabrications, while the effect of VUV irradiation on the dielectric constant (k value) of low-k materials is still an open question. To clarify this problem, VUV photons with a range of energies were exposed on low-k organosilicate dielectrics (SiCOH) samples at room temperature. Photon energies equal to or larger than 6.0 eV were found to decrease the k value of SiCOH films. VUV photons with lower energies do not have this effect. This shows the need for thermal heating in traditional ultraviolet (UV) curing since UV light sources do not have sufficient energy to change the dielectric constant of SiCOH and additional energy is required from thermal heating. In addition, 6.2 eV photon irradiation was found to be the most effective in decreasing the dielectric constant of low-k organosilicate films. Fourier Transform Infra-red Spectroscopy shows that these 6.2 eV VUV exposures removed organic porogens. This contributes to the decrease of the dielectric constant. This information provides the range of VUV photon energies that could decrease the dielectric constant of low-k materials most effectively.

  12. BOREAS RSS-17 Dielectric Constant Profile Measurements

    NASA Technical Reports Server (NTRS)

    Hall, Forrest G. (Editor); Nickeson, Jaime (Editor); McDonald, Kyle C.; Zimmerman, Reiner; Way, JoBea

    2000-01-01

    The BOREAS RSS-17 team acquired and analyzed imaging radar data from the ESA's ERS-1 over a complete annual cycle at the BOREAS sites in Canada in 1994 to detect shifts in radar backscatter related to varying environmental conditions. This data set consists of dielectric constant profile measurements from selected trees at various BOREAS flux tower sites. The relative dielectric constant was measured at C-band (frequency = 5 GHz) as a function of depth into the trunk of three trees at each site, Measurements were made during April 1994 with an Applied Microwave Corporation field PDP fitted with a 0.358-cm (0.141-inch) diameter coaxial probe tip. The data are available in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

  13. A preliminary study on the dielectric constant of WPC based on some tropical woods

    NASA Astrophysics Data System (ADS)

    Chia, L. H. L.; Chua, P. H.; Hon, Y. S.; Lee, E.

    The use of WPC as an important insulating material is studied by determining its dielectric constant. The variation of dielectric constant with moisture content is also investigated. Preliminary results show that all untreated woods studied have a higher dielectric constant than their polymer composites with the exception of Kapur and Keruing. It is therefore postulated that the presence of polymers has led to a decrease in the number of polarizable units. Such a material may be useful commercially.

  14. Low dielectric constant Parylene-F-like films for intermetal dielectric applications

    NASA Astrophysics Data System (ADS)

    Hanyaloglu, Bengi; Aydinli, Atilla; Oye, Michael; Aydi, Eray S.

    1999-01-01

    We report on the dielectric properties and thermal stability of thin polymer films that are suitable candidates for replacing silicon dioxide as the intermetal dielectric material in integrated circuits. Parylene-F-like films, (-CF2-C6H4-CF2-)n, were produced by plasma deposition from a mixture of Ar and 1,4-bis(trifluoromethyl)benzene (CF3-C6H4-CF3) discharges and characterized using infrared absorption spectroscopy, spectroscopic ellipsometry, and capacitance measurements. The dielectric constant and the magnitude of the electronic and ionic contributions to the dielectric constant were determined through capacitance measurements and Kramers-Kronig analysis of the infrared absorption data. The film's dielectric constant ranges between 2 and 2.6 depending on the deposition conditions and the largest contribution to the dielectric constant is electronic. The films deposited at 300 °C are stable above 400 °C and further optimization could push this limit to as high as 500 °C.

  15. High dielectric constant, low loss, and low percolation threshold dielectric composites based on polyvinylidene fluoride and ferroferric oxide nanorods

    NASA Astrophysics Data System (ADS)

    Li, Lili; Fu, Qiong; Li, Ya; Li, Weiping

    2016-08-01

    Dielectric super-capacitors call the excellent dielectric materials with high dielectric constant and low dielectric loss, both of which are not easy to obtain at the same time. The work synthesized the high aspect ratio and good crystalline ferroferric oxide (Fe3O4) nanorods by the hydrothermal process and used them as the filler to effectively reduce the percolation threshold value. It was found that the composites here based on the polyvinylidene fluoride (PVDF) polymer and these Fe3O4 nanorods exhibited ultra-high dielectric constant (>3000) and very low loss (<0.04) at very low filler fraction (0.35%). It was also proved that the high aspect ratio filler could help to improve the dielectric constant and suppress the dielectric loss in the percolative composites.

  16. Large dielectric constant, high acceptor density, and deep electron traps in perovskite solar cell material CsGeI3

    SciTech Connect

    Ming, Wenmei; Shi, Hongliang; Du, Mao-Hua

    2016-01-01

    Here we report that many metal halides that contain cations with the ns2 electronic configuration have recently been discovered as high-performance optoelectronic materials. In particular, solar cells based on lead halide perovskites have shown great promise as evidenced by the rapid increase of the power conversion efficiency. In this paper, we show density functional theory calculations of electronic structure and dielectric and defect properties of CsGeI3 (a lead-free halide perovskite material). The potential of CsGeI3 as a solar cell material is assessed based on its intrinsic properties. We find anomalously large Born effective charges and a large static dielectric constant dominated by lattice polarization, which should reduce carrier scattering, trapping, and recombination by screening charged defects and impurities. Defect calculations show that CsGeI3 is a p-type semiconductor and its hole density can be modified by varying the chemical potentials of the constituent elements. Despite the reduction of long-range Coulomb attraction by strong screening, the iodine vacancy in CsGeI3 is found to be a deep electron trap due to the short-range potential, i.e., strong Ge–Ge covalent bonding, which should limit electron transport efficiency in p-type CsGeI3. This is in contrast to the shallow iodine vacancies found in several Pb and Sn halide perovskites (e.g., CH3NH3PbI3, CH3NH3SnI3, and CsSnI3). The low-hole-density CsGeI3 may be a useful solar absorber material but the presence of the low-energy deep iodine vacancy may significantly reduce the open circuit voltage of the solar cell. Still, on the other hand, CsGeI3 may be used as an efficient hole transport material in solar cells due to its small hole effective mass, the absence of low-energy deep hole traps, and the favorable band offset with solar

  17. High Dielectric Constant Oxides for Advanced Micro-Electronic Applications

    DTIC Science & Technology

    2006-11-29

    having an appropriately larger dielectric constant, other physical considerations come into play: a) the material must be thermodynamically stable...substrate bias. 7 The primary activity outside the domain of deposition involved extensive characterization of the physical and electrical properties of...from Si. Interacts with Si when recrystallizing to form silicide and SiO2. LaAlO3 expected ε ~ 29 in crystalline phase but much lower in amorphous

  18. Statistical Modelling of the Soil Dielectric Constant

    NASA Astrophysics Data System (ADS)

    Usowicz, Boguslaw; Marczewski, Wojciech; Bogdan Usowicz, Jerzy; Lipiec, Jerzy

    2010-05-01

    The dielectric constant of soil is the physical property being very sensitive on water content. It funds several electrical measurement techniques for determining the water content by means of direct (TDR, FDR, and others related to effects of electrical conductance and/or capacitance) and indirect RS (Remote Sensing) methods. The work is devoted to a particular statistical manner of modelling the dielectric constant as the property accounting a wide range of specific soil composition, porosity, and mass density, within the unsaturated water content. Usually, similar models are determined for few particular soil types, and changing the soil type one needs switching the model on another type or to adjust it by parametrization of soil compounds. Therefore, it is difficult comparing and referring results between models. The presented model was developed for a generic representation of soil being a hypothetical mixture of spheres, each representing a soil fraction, in its proper phase state. The model generates a serial-parallel mesh of conductive and capacitive paths, which is analysed for a total conductive or capacitive property. The model was firstly developed to determine the thermal conductivity property, and now it is extended on the dielectric constant by analysing the capacitive mesh. The analysis is provided by statistical means obeying physical laws related to the serial-parallel branching of the representative electrical mesh. Physical relevance of the analysis is established electrically, but the definition of the electrical mesh is controlled statistically by parametrization of compound fractions, by determining the number of representative spheres per unitary volume per fraction, and by determining the number of fractions. That way the model is capable covering properties of nearly all possible soil types, all phase states within recognition of the Lorenz and Knudsen conditions. In effect the model allows on generating a hypothetical representative of

  19. Electronic transport in two-dimensional high dielectric constant nanosystems

    PubMed Central

    Ortuño, M.; Somoza, A. M.; Vinokur, V. M.; Baturina, T. I.

    2015-01-01

    There has been remarkable recent progress in engineering high-dielectric constant two dimensional (2D) materials, which are being actively pursued for applications in nanoelectronics in capacitor and memory devices, energy storage, and high-frequency modulation in communication devices. Yet many of the unique properties of these systems are poorly understood and remain unexplored. Here we report a numerical study of hopping conductivity of the lateral network of capacitors, which models two-dimensional insulators, and demonstrate that 2D long-range Coulomb interactions lead to peculiar size effects. We find that the characteristic energy governing electronic transport scales logarithmically with either system size or electrostatic screening length depending on which one is shorter. Our results are relevant well beyond their immediate context, explaining, for example, recent experimental observations of logarithmic size dependence of electric conductivity of thin superconducting films in the critical vicinity of superconductor-insulator transition where a giant dielectric constant develops. Our findings mark a radical departure from the orthodox view of conductivity in 2D systems as a local characteristic of materials and establish its macroscopic global character as a generic property of high-dielectric constant 2D nanomaterials. PMID:25860804

  20. Electronic transport in two-dimensional high dielectric constant nanosystems

    DOE PAGES

    Ortuño, M.; Somoza, A. M.; Vinokur, V. M.; ...

    2015-04-10

    There has been remarkable recent progress in engineering high-dielectric constant two dimensional (2D) materials, which are being actively pursued for applications in nanoelectronics in capacitor and memory devices, energy storage, and high-frequency modulation in communication devices. Yet many of the unique properties of these systems are poorly understood and remain unexplored. Here we report a numerical study of hopping conductivity of the lateral network of capacitors, which models two-dimensional insulators, and demonstrate that 2D long-range Coulomb interactions lead to peculiar size effects. We find that the characteristic energy governing electronic transport scales logarithmically with either system size or electrostatic screeningmore » length depending on which one is shorter. Our results are relevant well beyond their immediate context, explaining, for example, recent experimental observations of logarithmic size dependence of electric conductivity of thin superconducting films in the critical vicinity of superconductor-insulator transition where a giant dielectric constant develops. Our findings mark a radical departure from the orthodox view of conductivity in 2D systems as a local characteristic of materials and establish its macroscopic global character as a generic property of high-dielectric constant 2D nanomaterials.« less

  1. Electronic transport in two-dimensional high dielectric constant nanosystems

    SciTech Connect

    Ortuño, M.; Somoza, A. M.; Vinokur, V. M.; Baturina, T. I.

    2015-04-10

    There has been remarkable recent progress in engineering high-dielectric constant two dimensional (2D) materials, which are being actively pursued for applications in nanoelectronics in capacitor and memory devices, energy storage, and high-frequency modulation in communication devices. Yet many of the unique properties of these systems are poorly understood and remain unexplored. Here we report a numerical study of hopping conductivity of the lateral network of capacitors, which models two-dimensional insulators, and demonstrate that 2D long-range Coulomb interactions lead to peculiar size effects. We find that the characteristic energy governing electronic transport scales logarithmically with either system size or electrostatic screening length depending on which one is shorter. Our results are relevant well beyond their immediate context, explaining, for example, recent experimental observations of logarithmic size dependence of electric conductivity of thin superconducting films in the critical vicinity of superconductor-insulator transition where a giant dielectric constant develops. Our findings mark a radical departure from the orthodox view of conductivity in 2D systems as a local characteristic of materials and establish its macroscopic global character as a generic property of high-dielectric constant 2D nanomaterials.

  2. Electronic transport in two-dimensional high dielectric constant nanosystems

    NASA Astrophysics Data System (ADS)

    Ortuño, M.; Somoza, A. M.; Vinokur, V. M.; Baturina, T. I.

    2015-04-01

    There has been remarkable recent progress in engineering high-dielectric constant two dimensional (2D) materials, which are being actively pursued for applications in nanoelectronics in capacitor and memory devices, energy storage, and high-frequency modulation in communication devices. Yet many of the unique properties of these systems are poorly understood and remain unexplored. Here we report a numerical study of hopping conductivity of the lateral network of capacitors, which models two-dimensional insulators, and demonstrate that 2D long-range Coulomb interactions lead to peculiar size effects. We find that the characteristic energy governing electronic transport scales logarithmically with either system size or electrostatic screening length depending on which one is shorter. Our results are relevant well beyond their immediate context, explaining, for example, recent experimental observations of logarithmic size dependence of electric conductivity of thin superconducting films in the critical vicinity of superconductor-insulator transition where a giant dielectric constant develops. Our findings mark a radical departure from the orthodox view of conductivity in 2D systems as a local characteristic of materials and establish its macroscopic global character as a generic property of high-dielectric constant 2D nanomaterials.

  3. Effective dielectric constants and spectral density analysis of plasmonic nanocomposites

    NASA Astrophysics Data System (ADS)

    Lu, Jin You; Raza, Aikifa; Fang, Nicholas X.; Chen, Gang; Zhang, TieJun

    2016-10-01

    Cermet or ceramic-metal composite coatings promise great potentials in light harvesting, but the complicated composite structure at the nanoscale induces a design challenge to predict their optical properties. We find that the effective dielectric constants of nanocomposites predicted by finite-difference-time-domain (FDTD) simulation results match those of different classical effective medium theories in their respective validity range. However, a precise prediction of the fabricated nanocomposite properties for different filling factors is very challenging. In this work, we extract the spectral density functions in the Bergman representation from the analytical models, numerical simulations, and experimental data of plasmonic nanocomposites. The spectral density functions, which only depend on geometry of the nanocomposite material, provide a unique measure on the contribution of individual and percolated particles inside the nanocomposite. According to the spectral density analysis of measured dielectric constants, the material properties of nanocomposites fabricated by the co-sputtering approach are dominated by electromagnetic interaction among individual metallic particles. While in the case of the nanocomposites fabricated by the multilayer thin film approach, the material properties are dominated by percolated metallic particles inside the dielectric host, as indicated by our FDTD simulation results. This understanding provides new physical insight into the interaction between light and plasmonic nanocomposites.

  4. Photoinduced Giant Dielectric Constant in Lead Halide Perovskite Solar Cells.

    PubMed

    Juarez-Perez, Emilio J; Sanchez, Rafael S; Badia, Laura; Garcia-Belmonte, Germá; Kang, Yong Soo; Mora-Sero, Ivan; Bisquert, Juan

    2014-07-03

    Organic-inorganic lead trihalide perovskites have emerged as an outstanding photovoltaic material that demonstrated a high 17.9% conversion efficiency of sunlight to electricity in a short time. We have found a giant dielectric constant (GDC) phenomenon in these materials consisting on a low frequency dielectric constant in the dark of the order of ε0 = 1000. We also found an unprecedented behavior in which ε0 further increases under illumination or by charge injection at applied bias. We observe that ε0 increases nearly linearly with the illumination intensity up to an additional factor 1000 under 1 sun. Measurement of a variety of samples of different morphologies, compositions, and different types of contacts shows that the GDC is an intrinsic property of MAPbX3 (MA = CH3NH3(+)). We hypothesize that the large dielectric response is induced by structural fluctuations. Photoinduced carriers modify the local unit cell equilibrium and change the polarizability, assisted by the freedom of rotation of MA. The study opens a way for the understanding of a key aspect of the photovoltaic operation of high efficiency perovskite solar cells.

  5. Microwave dielectric behavior of vegetation material

    NASA Technical Reports Server (NTRS)

    Elrayes, Mohamed A.; Ulaby, Fawwaz T.

    1987-01-01

    The microwave dielectric behavior of vegetation was examined through the development of theoretical models involving dielectric dispersion by both bound and free water and supported by extensive dielectric measurements conducted over a wide range of conditions. The experimental data were acquired using an open-ended coaxial probe that was developed for sensing the dielectric constant of thin layers of materials, such as leaves, from measurements of the complex reflection coefficient using a network analyzer. The probe system was successfully used to record the spectral variation of the dielectric constant over a wide frequency range extending from 0.5 to 20.4 GHz at numerous temperatures between -40 to +40 C. The vegetation samples were measured over a wide range of moisture conditions. To model the dielectric spectrum of the bound water component of the water included in vegetation, dielectric measurements were made for several sucrose-water solutions as analogs for the situation in vegetation. The results were used in conjunction with the experimental data for leaves to determine some of the constant coefficients in the theoretical models. Two models, both of which provide good fit to the data, are proposed.

  6. Exploring Strategies for High Dielectric Constant and Low Loss Polymer Dielectrics

    NASA Astrophysics Data System (ADS)

    Zhu, Lei

    Polymer dielectrics having high dielectric constant, high temperature capability, and low loss are attractive for a broad range of applications such as film capacitors, gate dielectrics, artificial muscles, and electrocaloric cooling. Unfortunately, it is generally observed that higher polarization or dielectric constant tends to cause significantly enhanced dielectric loss. It is therefore highly desired that the fundamental physics of all types of polarization and loss mechanisms be thoroughly understood for dielectric polymers. In this presentation, we intend to explore advantages and disadvantages for different types of polarization. Among a number of approaches, dipolar polarization is promising for high dielectric constant and low loss polymer dielectrics, if the dipolar relaxation peak can be pushed to above the gigahertz range. In particular, dipolar glass, paraelectric, and relaxor ferroelectric polymers are discussed for the dipolar polarization approach. This work is supported by NSF Polymers Program (DMR-1402733).

  7. Exploring Strategies for High Dielectric Constant and Low Loss Polymer Dielectrics.

    PubMed

    Zhu, Lei

    2014-11-06

    Polymer dielectrics having high dielectric constant, high temperature capability, and low loss are attractive for a broad range of applications such as film capacitors, gate dielectrics, artificial muscles, and electrocaloric cooling. Unfortunately, it is generally observed that higher polarization or dielectric constant tends to cause significantly enhanced dielectric loss. It is therefore highly desired that the fundamental physics of all types of polarization and loss mechanisms be thoroughly understood for dielectric polymers. In this Perspective, we intend to explore advantages and disadvantages for different types of polarization. Among a number of approaches, dipolar polarization is promising for high dielectric constant and low loss polymer dielectrics, if the dipolar relaxation peak can be pushed to above the gigahertz range. In particular, dipolar glass, paraelectric, and relaxor ferroelectric polymers are discussed for the dipolar polarization approach.

  8. Functionalised graphene sheets as effective high dielectric constant fillers

    PubMed Central

    2011-01-01

    A new functionalised graphene sheet (FGS) filled poly(dimethyl)siloxane insulator nanocomposite has been developed with high dielectric constant, making it well suited for applications in flexible electronics. The dielectric permittivity increased tenfold at 10 Hz and 2 wt.% FGS, while preserving low dielectric losses and good mechanical properties. The presence of functional groups on the graphene sheet surface improved the compatibility nanofiller/polymer at the interface, reducing the polarisation process. This study demonstrates that functionalised graphene sheets are ideal nanofillers for the development of new polymer composites with high dielectric constant values. PACS: 78.20.Ci, 72.80.Tm, 62.23.Kn PMID:21867505

  9. Role of dielectric constant in electrohydrodynamics of conducting fluids

    NASA Technical Reports Server (NTRS)

    Rhodes, Percy H.; Snyder, Robert S.; Roberts, Glyn O.

    1992-01-01

    Electrohydrodynamic (EHD) flows are driven by the interaction of an electric field with variations in electric conductivity or dielectric constant. In reported EHD experiments on the deformation of drops of immiscible dielectric fluids, the role of conductivity has tended to overshadow the role of dielectric constant. Often, large conductivity contrasts were convenient because the conductivities of the dielectric fluid were relatively uncertain. As a result, the observed effects were always qualitatively the same as if there had been no contrast in dielectric constant. Our early experiments studying the EHC deformations of cylindrical streams readily showed the conductivity effect but the dielectric constant effect was not discernible. We have modified our flow chamber and improved our method of observation and can now see an unequivocal dielectric constant effect which is in agreement with the prior theory. In this paper we first give a brief description of the physics of charge buildup at the interface of an immersed spherical drop or flowing cylindrical sample stream and then show how these charge distributions lead to interface distortions and accompanying viscous flows which constitute EHD. We next review theory and experiment describing the deformation of spherical drops. We show that in the reported drop deformation experiments, the contrast in dielectric constant was never sufficient to reverse the deformation due to the conductivity contrast. We review our work describing the deformation of a cylindrical stream of one fluid flowing in a parallel flow of another, and we compare the deformation equations with those for spherical drops. Finally, we show a definite experimental dielectric constant effect for cylindrical stream of aqueous polystyrene latex suspension. The dielectric constant varies with the frequency of the imposed electric field, and the associated EHD flow change is very apparent.

  10. Dielectric constant of liquid alkanes and hydrocarbon mixtures

    NASA Technical Reports Server (NTRS)

    Sen, A. D.; Anicich, V. G.; Arakelian, T.

    1992-01-01

    The complex dielectric constants of n-alkanes with two to seven carbon atoms have been measured. The measurements were conducted using a slotted-line technique at 1.2 GHz and at atmospheric pressure. The temperature was varied from the melting point to the boiling point of the respective alkanes. The real part of the dielectric constant was found to decrease with increasing temperature and correlate with the change in the molar volume. An upper limit to all the loss tangents was established at 0.001. The complex dielectric constants of a few mixtures of liquid alkanes were also measured at room temperature. For a pentane-octane mixture the real part of the dielectric constant could be explained by the Clausius-Mosotti theory. For the mixtures of n-hexane-ethylacetate and n-hexane-acetone the real part of the dielectric constants could be explained by the Onsager theory extended to mixtures. The dielectric constant of the n-hexane-acetone mixture displayed deviations from the Onsager theory at the highest fractions of acetone. The dipole moments of ethylacetate and acetone were determined for dilute mixtures using the Onsager theory and were found to be in agreement with their accepted gas-phase values. The loss tangents of the mixtures exhibited a linear relationship with the volume fraction for low concentrations of the polar liquids.

  11. Dielectric constant of liquid alkanes and hydrocarbon mixtures.

    PubMed

    Sen, A D; Anicich, V G; Arakelian, T

    1992-01-01

    The complex dielectric constants of n-alkanes with two to seven carbon atoms have been measured. The measurements were conducted using a slotted-line technique at 1.2 GHz and at atmospheric pressure. The temperature was varied from the melting point to the boiling point of the respective alkanes. The real part of the dielectric constant was found to decrease with increasing temperature and correlate with the change in the molar volume. An upper limit to all the loss tangents was established at 0.001. The complex dielectric constants of a few mixtures of liquid alkanes were also measured at room temperature. For a pentane-octane mixture the real part of the dielectric constant could be explained by the Clausius-Mosotti theory. For the mixtures of n-hexane-ethylacetate and n-hexane-acetone the real part of the dielectric constants could be explained by the Onsager theory extended to mixtures. The dielectric constant of the n-hexane-acetone mixture displayed deviations from the Onsager theory at the highest fractions of acetone. The dipole moments of ethylacetate and acetone were determined for dilute mixtures using the Onsager theory and were found to be in agreement with their accepted gas-phase values. The loss tangents of the mixtures exhibited a linear relationship with the volume fraction for low concentrations of the polar liquids.

  12. Low-Dielectric Constant Polyimide Nanoporous Films: Synthesis and Properties

    NASA Astrophysics Data System (ADS)

    Mehdipour-Ataei, S.; Rahimi, A.; Saidi, S.

    2007-08-01

    Synthesis of high temperature polyimide foams with pore sizes in the nanometer range was developed. Foams were prepared by casting graft copolymers comprising a thermally stable block as the matrix and a thermally labile material as the dispersed phase. Polyimides derived from pyromellitic dianhydride with new diamines (4BAP and BAN) were used as the matrix material and functionalized poly(propylene glycol) oligomers were used as a thermally labile constituent. Upon thermal treatment the labile blocks were subsequently removed leaving pores with the size and shape of the original copolymer morphology. The polyimides and foamed polyimides were characterized by some conventional methods including FTIR, H-NMR, DSC, TGA, SEM, TEM, and dielectric constant.

  13. Effective Dielectric Constants of Foliage Media

    DTIC Science & Technology

    1990-07-01

    APPROVED: JOHN K. SCHINDLER Director of Electromagnetics FOR THE COMMANDER: JAMES W. HYDE III Directorate of Plans & Programs DESTRUCTION NOTICE - For...PARAMETERS FOR A HETEROGENEOUS MEDIUM 3 2.1 Basic Theory of the Transition Matrix 3 2.2 The Transition Operator Nomenclature 5 2.2.1 The Average T...parameter approximation equations and dielectric properties of forest components, respectively. 2.1 Basic Theory of the Transition Matrix In this section

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

    SciTech Connect

    Dong, L. F.; Fan, W. L.; Wang, S.; Ji, Y. F.; Liu, Z. W.; Chen, Q.

    2011-03-15

    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.

  15. PECVD of low-dielectric constant films for ULSI

    NASA Astrophysics Data System (ADS)

    Shimogaki, Yukihiro

    1998-10-01

    We studied the reduction mechanism of the dielectric constant of F-doped silicon oxide films prepared by PECVD from SiH_4/N_2O/CF4 mixture. From the estimation of the dielectric constant at various frequencies, ranging from 1MHz to 100THz, using CV measurement, Kramers-Kronig relation and the square of the refractive index, we suggest that the dielectric constant due to ionic and electronic polarization is not the dominant factor in decreasing the dielectric constant. It is important to remove -OH in films to obtain very low dielectric constant F-doped silicon oxide films, because Si-OH is the main factor of the orientational polarization in silicon oxide films made by PECVD. To investigate the reaction mechanism which controls the film structure, we changed the residence time of gas in chamber by varying the flow rate. When the residence time in chamber decreases, the film deposition rate increases. We tried to explain flow rate dependency of the deposition rate using a simple CSTR (continuous stirred tank reactor) model. It can be concluded that there are two paths to deposit the films. One route is a deposition by the precursors with poor step coverage profile, and the other route is deposition through intermediates formed by gas phase reactions that contribute to have better step coverage. The overall gas phase reaction rate constant was estimated from these kinetic studies. Same approach was also carried out on the PECVD of C:F film deposition.

  16. Thermal stability of low dielectric constant porous silica films

    NASA Astrophysics Data System (ADS)

    Esposito, L.; Ottaviani, G.; Carollo, E.; Bacchetta, M.

    2005-12-01

    Thermal stability of porous-silica-based low dielectric constant, k, material deposited by chemical vapor deposition has been investigated in a wide temperature range. The films as-deposited and after heat treatments up to 600°C have Si1O1.6C1.4H2.3 composition, permittivity k ≈2.8, and porosity h ≈0.25. A skeleton of silicon dioxide and empty pores justifies the permittivity and porosity values. Permeation experiments with deuterated water vapor indicate that pores are interconnected. At 700°C, the film has Si1O1.6C1.4H1.4 composition, k ≈2.4, and h ≈0.21. Bonds with lower polarizability could be responsible for the decrease of k. Above 800°C, carbon segregation and nanoclusters formation occur.

  17. Measurements of the dielectric constants for planetary volatiles

    NASA Technical Reports Server (NTRS)

    Anicich, Vincent G.; Huntress, Wesley T., Jr.

    1987-01-01

    The model of Titan at present has the surface temperature, pressure, and composition such that there is a possibility of a binary ethane-methane ocean. Proposed experiments for future Titan flybys include microwave mappers. Very little has been measured of the dielectric properties of the small hydrocarbons at these radar frequencies. An experiment was conducted utilizing a slotted line to measure the dielectric properties of the hydrocarbons, methane to heptane, from room temperature to -180 C. Measurements of the real part of the dielectric constants are accurate to + or - 0.006 and the imaginary part (the loss tangent) of the liquids studied is less than or equal to 0.001. In order to verify this low loss tangent, the real part of the dielectric constant of hexane at 25 C was studied as a function of the frequency range of the slotted line system used. The dielectric constant of hexane at room temperature, between 500 MHz and 3 MHz, is constant within experimental error.

  18. Thermally driven sign switch of static dielectric constant of VO2 thin film

    NASA Astrophysics Data System (ADS)

    Kana Kana, J. B.; Vignaud, G.; Gibaud, A.; Maaza, M.

    2016-04-01

    Smart multifunctional materials exhibiting phase transition and tunable optical and/electrical properties provide a new direction towards engineering switchable devices. Specifically, the reversible, tunable and sign switch dielectric constants via external temperature stimuli observed in vanadium dioxide (VO2) make it a candidate of choice for tunable and switchable technologies devices. Here we report new aspect of the metal-insulator transition (MIT) through the sign switch of the static dielectric constant εS of pure VO2. As it is shown, the static dielectric constant showed an abrupt change from positive at T < 70 °C to negative at T > 70 °C. εS > 0 confirms the insulating phase where charges are localized while εS < 0 confirms the metallic phase of VO2 where charges are delocalized. We report for the first time the tunability of the dielectric constant from a negative sign for the static dielectric constant of VO2 thin film rarely found in real physical systems. We also demonstrate the tunability and switchability of the real and imaginary part of the dielectric constant (ε) via external temperature stimuli. More specifically, the real (ε) and Imaginary (ε) showed an abrupt thermal hysteresis which clearly confirms the phase transition.

  19. Role of dielectric constant in electrohydrodynamics of conducting fluids

    NASA Technical Reports Server (NTRS)

    Rhodes, Percy H.; Snyder, Robert S.; Roberts, Glyn O.

    1994-01-01

    Electrohydrodynamic sample distortion during continuous flow electrophoresis is an experiment to be conducted during the second International Microgravity Laboratory (IML-2) in July 1994. The specific objective of this experiment is the distortion caused by the difference in dielectric constant between the sample and surrounding buffer. Although the role of sample conductivity in electrohydrodynamic has been the subject of both flight and ground experiments, the separate role of dielectric constant, independent of sample conductivity, has not been measured. This paper describes some of the laboratory research and model development that will support the flight experiment on IML-2.

  20. Dielectric constants of soils at microwave frequencies-2

    NASA Technical Reports Server (NTRS)

    Wang, J.; Schmugge, T.; Williams, D.

    1978-01-01

    The dielectric constants of several soil samples were measured at frequencies of 5 and 19 GHz using the infinite transmission line method. The results of these measurements are presented and discussed with respect to soil types and texture structures. A comparison is made with other measurements at 1.4 GHz. At all three frequencies, the dependence of dielectric constant on soil moisture can be approximated by two straight lines. At low moisture, the slope is less than at high moisture level. The intersection of the two lines is believed to be a function of soil texture.

  1. Remote Sensing of Salinity: The Dielectric Constant of Sea Water

    NASA Technical Reports Server (NTRS)

    LeVine, David M.; Lang, R.; Utku, C.; Tarkocin, Y.

    2011-01-01

    Global monitoring of sea surface salinity from space requires an accurate model for the dielectric constant of sea water as a function of salinity and temperature to characterize the emissivity of the surface. Measurements are being made at 1.413 GHz, the center frequency of the Aquarius radiometers, using a resonant cavity and the perturbation method. The cavity is operated in a transmission mode and immersed in a liquid bath to control temperature. Multiple measurements are made at each temperature and salinity. Error budgets indicate a relative accuracy for both real and imaginary parts of the dielectric constant of about 1%.

  2. High dielectric constant 0-3 ceramic-polymer composites

    NASA Astrophysics Data System (ADS)

    Shan, Xiaobing

    0-3 ceramic-polymer composites using both nano-size and micro-size CaCu3Ti4O12 ceramic particles were studied. The micro-size ceramic particles were prepared from the CaCu3Ti 4O12 pellets by milling. The CaCu3Ti4O 12 ceramics were prepared using conventional solid-state reaction under different conditions, such as molding pressure, milling media and time, and calcination temperature and time. Based on the analysis of the dielectric spectrum, it was found that the dielectric responses of CaCu3Ti 4O12 ceramics are determined by three different processes. The effect of thickness of the ceramics on the dielectric properties was observed and studied. Although the dielectric response at low frequency increases with decreasing thickness, the dielectric behavior for the high frequency relaxation process is weakly dependent on thickness. 0-3 composites with different concentrations (0-50 vo% CaCu3Ti 4O12 ceramics) were prepared using solution casting. However, a clear polymer-rich layer was found in as-cast film due to the poor wettability between ceramic and polymer matrix. The HP was used to modify the morphology of the composites. Different configurations were studied for the HP process. Composites with a dielectric constant of 510 at 1 kHz were obtained in 50vol% CaCu3Ti4O12 composite with CC HP at room temperature. It was found that the relaxation time of the major relaxation process obtained in the composite changes with processing condition, such as annealing, HP and concentration. It indicates that the interfacial layers between ceramic particles and polymer matrix play an important role on the dielectric response of the composite. As for the HP samples, it was interestingly observed that as HP time changes, there is a critical HP time at which the composite exhibits a much higher dielectric constant. Based on the dielectric spectrum of the composites at different temperatures, it was concluded that the loss of the composites at low frequency is controlled by a

  3. Table of Dielectric Constants of Pure Liquids

    DTIC Science & Technology

    1951-08-10

    Mathematics Series, Building Materials and Structures Reports, Miscellaneous Publications, and Circulars. Each issue contains 12 or more two-column pages...2.2 Standard liquids ---------------------- ----------- 2.3 Chemical formulas and the order of listing of substances _II 2.4 Estimated accuracy of...Numdriques XI, Fasicule 2, 1931-34; that are recommended as reference liquids because XII, Fasicule :32, 1935-:36 and earlier volumes of of their chemical

  4. Millimeter Wave Dielectric Properties of Materials

    NASA Astrophysics Data System (ADS)

    Button, Kenneth J.; Afsar, M. N.

    1983-10-01

    Highly accurate continuous spectra of the absorption coefficient and refractive index of some potentially useful materials have been made over the 60-420 GHz range. Measurements have been made on some common ceramic, semiconductor, crystalline and glass materials. The absorption coefficient of low loss materials increases with frequency which implies that microwave data cannot be used for the design of millimeter wave dielectric waveguides, devices, windows and quasi-optical elements. The data in this paper show the millimeter wave frequency dependence of tan δ, the real and imaginary parts of the dielectric permittivity and the optical constants, namely, the refractive index and absorption coefficient. The measurements have been made in a plane-wave Michelson interferometer operating as a polarizing, dispersive Fourier transform spectrometer. The accuracy and reproducability of the refractive index is six significant figures.

  5. Low-Dielectric-Constant Polyimide/Glass Composites

    NASA Technical Reports Server (NTRS)

    Stoakley, Diane M.; St. Clair, Anne K.; Baucom, Robert M.; Proctor, K. Mason; Smith, Ricky E.; Smith, Janice Y.

    1994-01-01

    Advance in polymer technology yields composites having relatively low dielectric constants. Reduction achieved by reducing interactions between linear polyimide chains and by incorporation of fluorine into polymer backbones. Further reductions obtained by physically incorporating selected diamic acid additives into polyimides. Strong potential for use in microelectronics industry for fabrication of printed-circuit boards and fabrication of components for military aircraft.

  6. Effect of Cold Temperature on the Dielectric Constant of Soil

    DTIC Science & Technology

    2012-04-01

    25.8 mm, d = 17.0 mm, si = 37.0 mm, and so = 37.5 mm. The ring and its feedlines are signal-carrying conductors in microstrip . Beneath the ring...is a printed circuit board (PCB) of uniform thickness and dielectric constant, and beneath the PCB dielectric is a metal ground plane. RF energy...Modeling of Ring Resonators; in Microwave Ring Circuits and Related Structures, 2nd ed., Hoboken, NJ: John Wiley & Sons, 2004, h. 2, Sec. 2.2, pp. 6

  7. Core-shell structured polystyrene/BaTiO3 hybrid nanodielectrics prepared by in situ RAFT polymerization: a route to high dielectric constant and low loss materials with weak frequency dependence.

    PubMed

    Yang, Ke; Huang, Xingyi; Xie, Liyuan; Wu, Chao; Jiang, Pingkai; Tanaka, Toshikatsu

    2012-11-23

    A novel route to prepare core-shell structured nanocomposites with excellent dielectric performance is reported. This approach involves the grafting of polystyrene (PS) from the surface of BaTiO(3) by an in situ RAFT polymerization. The core-shell structured PS/BaTiO(3) nanocomposites not only show significantly increased dielectric constant and very low dielectric loss, but also have a weak frequency dependence of dielectric properties over a wide range of frequencies. In addition, the dielectric constant of the nanocomposites can also be easily tuned by varying the thickness of the PS shell. Our method is very promising for preparing high-performance nanocomposites used in energy-storage devices.

  8. Asymmetric Dielectric Elastomer Composite Material

    NASA Technical Reports Server (NTRS)

    Stewart, Brian K. (Inventor)

    2014-01-01

    Embodiments of the invention provide a dielectric elastomer composite material comprising a plurality of elastomer-coated electrodes arranged in an assembly. Embodiments of the invention provide improved force output over prior DEs by producing thinner spacing between electrode surfaces. This is accomplished by coating electrodes directly with uncured elastomer in liquid form and then assembling a finished component (which may be termed an actuator) from coated electrode components.

  9. Defect density and dielectric constant in perovskite solar cells

    SciTech Connect

    Samiee, Mehran; Konduri, Siva; Abbas, Hisham A.; Joshi, Pranav; Zhang, Liang; Dalal, Vikram; Ganapathy, Balaji; Kottokkaran, Ranjith; Noack, Max; Kitahara, Andrew

    2014-10-13

    We report on measurement of dielectric constant, mid-gap defect density, Urbach energy of tail states in CH{sub 3}NH{sub 3}PbI{sub x}Cl{sub 1−x} perovskite solar cells. Midgap defect densities were estimated by measuring capacitance vs. frequency at different temperatures and show two peaks, one at 0.66 eV below the conduction band and one at 0.24 eV below the conduction band. The attempt to escape frequency is in the range of 2 × 10{sup 11}/s. Quantum efficiency data indicate a bandgap of 1.58 eV. Urbach energies of valence and conduction band are estimated to be ∼16 and ∼18 meV. Measurement of saturation capacitance indicates that the relative dielectric constant is ∼18.

  10. Thickness-Dependent Dielectric Constant of Few-Layer In₂Se₃ Nanoflakes.

    PubMed

    Wu, Di; Pak, Alexander J; Liu, Yingnan; Zhou, Yu; Wu, Xiaoyu; Zhu, Yihan; Lin, Min; Han, Yu; Ren, Yuan; Peng, Hailin; Tsai, Yu-Hao; Hwang, Gyeong S; Lai, Keji

    2015-12-09

    The dielectric constant or relative permittivity (ε(r)) of a dielectric material, which describes how the net electric field in the medium is reduced with respect to the external field, is a parameter of critical importance for charging and screening in electronic devices. Such a fundamental material property is intimately related to not only the polarizability of individual atoms but also the specific atomic arrangement in the crystal lattice. In this Letter, we present both experimental and theoretical investigations on the dielectric constant of few-layer In2Se3 nanoflakes grown on mica substrates by van der Waals epitaxy. A nondestructive microwave impedance microscope is employed to simultaneously quantify the number of layers and local electrical properties. The measured ε(r) increases monotonically as a function of the thickness and saturates to the bulk value at around 6-8 quintuple layers. The same trend of layer-dependent dielectric constant is also revealed by first-principles calculations. Our results of the dielectric response, being ubiquitously applicable to layered 2D semiconductors, are expected to be significant for this vibrant research field.

  11. The effects of sintering temperature on dielectric constant of Barium Titanate (BaTiO3)

    NASA Astrophysics Data System (ADS)

    Sandi, DianisaKhoirum; Supriyanto, Agus; Anif; Jamaluddin; Iriani, Yofentina

    2016-02-01

    Barium Titanate (BT) has been synthesized using solid-state reaction method. Raw materials are Barium Carbonate (BaCO3) and Titanium Dioxide (TiO2). These materials are mixed for 6 h and sintered at a temperature of 1000oC, 1100oC, and 1200oC for 2 h. The sintering temperature was varied to investigate its effects on microstructure and dielectric constant of BT. The XRD patterns showed that BT becomes homogenous, with the large lattice parameter as the increase of sintering temperature. The crystal structure of BT is tetragonal. The crystalline size and crystallinity of BT at a sintering temperature of 1000oC are 37 nm and 97%. Those values for BT at a sintering temperature of 1100oC are 38 nm and 96%. At a sintering temperature of 1200oC, the values are 41 nm and 97%. The dielectric constant of BT at a sintering temperature of 1000oC, 1100oC, and 1200oC are 148, 163, and 185, respectively. It can be concluded that sintering temperature affects microstructure and dielectric constant of BT. High sintering temperature produces a high dielectric constant of BT. It indicates that crystalline size increases.

  12. Preparation of dielectric coating of variable dielectric constant by plasma polymerization

    NASA Technical Reports Server (NTRS)

    Hudis, M.; Wydeven, T. (Inventor)

    1979-01-01

    A plasma polymerization process for the deposition of a dielectric polymer coating on a substrate comprising disposing of the substrate in a closed reactor between two temperature controlled electrodes connected to a power supply is presented. A vacuum is maintained within the closed reactor, causing a monomer gas or gas mixture of a monomer and diluent to flow into the reactor, generating a plasma between the electrodes. The vacuum varies and controls the dielectric constant of the polymer coating being deposited by regulating the gas total and partial pressure, the electric field strength and frequency, and the current density.

  13. Organic/Inorganic Nano-hybrids with High Dielectric Constant for Organic Thin Film Transistor Applications

    NASA Astrophysics Data System (ADS)

    Yu, Yang-Yen; Jiang, Ai-Hua; Lee, Wen-Ya

    2016-11-01

    The organic material soluble polyimide (PI) and organic-inorganic hybrid PI-barium titanate (BaTiO3) nanoparticle dielectric materials (IBX, where X is the concentration of BaTiO3 nanoparticles in a PI matrix) were successfully synthesized through a sol-gel process. The effects of various BaTiO3 contents on the hybrid film performance and performance optimization were investigated. Furthermore, pentacene-based organic thin film transistors (OTFTs) with PI-BaTiO3/polymethylmethacrylate or cyclic olefin copolymer (COC)-modified gate dielectrics were fabricated and examined. The hybrid materials showed effective dispersion of BaTiO3 nanoparticles in the PI matrix and favorable thermal properties. X-ray diffraction patterns revealed that the BaTiO3 nanoparticles had a perovskite structure. The hybrid films exhibited high formability and planarity. The IBX hybrid dielectric films exhibited tunable insulating properties such as the dielectric constant value and capacitance in ranges of 4.0-8.6 and 9.2-17.5 nF cm-2, respectively. Adding the modified layer caused the decrease of dielectric constant values and capacitances. The modified dielectric layer without cross-linking displayed a hydrophobic surface. The electrical characteristics of the pentacene-based OTFTs were enhanced after the surface modification. The optimal condition for the dielectric layer was 10 wt% hybrid film with the COC-modified layer; moreover, the device exhibited a threshold voltage of 0.12 V, field-effect mobility of 4.32 × 10-1 cm2 V-1 s-1, and on/off current of 8.4 × 107.

  14. Organic/Inorganic Nano-hybrids with High Dielectric Constant for Organic Thin Film Transistor Applications.

    PubMed

    Yu, Yang-Yen; Jiang, Ai-Hua; Lee, Wen-Ya

    2016-12-01

    The organic material soluble polyimide (PI) and organic-inorganic hybrid PI-barium titanate (BaTiO3) nanoparticle dielectric materials (IBX, where X is the concentration of BaTiO3 nanoparticles in a PI matrix) were successfully synthesized through a sol-gel process. The effects of various BaTiO3 contents on the hybrid film performance and performance optimization were investigated. Furthermore, pentacene-based organic thin film transistors (OTFTs) with PI-BaTiO3/polymethylmethacrylate or cyclic olefin copolymer (COC)-modified gate dielectrics were fabricated and examined. The hybrid materials showed effective dispersion of BaTiO3 nanoparticles in the PI matrix and favorable thermal properties. X-ray diffraction patterns revealed that the BaTiO3 nanoparticles had a perovskite structure. The hybrid films exhibited high formability and planarity. The IBX hybrid dielectric films exhibited tunable insulating properties such as the dielectric constant value and capacitance in ranges of 4.0-8.6 and 9.2-17.5 nF cm(-2), respectively. Adding the modified layer caused the decrease of dielectric constant values and capacitances. The modified dielectric layer without cross-linking displayed a hydrophobic surface. The electrical characteristics of the pentacene-based OTFTs were enhanced after the surface modification. The optimal condition for the dielectric layer was 10 wt% hybrid film with the COC-modified layer; moreover, the device exhibited a threshold voltage of 0.12 V, field-effect mobility of 4.32 × 10(-1) cm(2) V(-1) s(-1), and on/off current of 8.4 × 10(7).

  15. Dielectric Constant Measurements on Lead Azide Single Crystals

    DTIC Science & Technology

    1980-09-01

    1000 Hz. The dielectric constants of the azides of TI, Na, and K Vere also measured and compared to published values. Calculations takf’ into account ...and W. McCrone , "Lead Azide, Pb(N 3 ) 2 , Aial. Chem. 28, 1791 (1956). 9 5 i:% 8. W.L. Garrett, "The Growth of Large Lead Azide Crystals," Mat. Res...10. Handbook of Chemistry and Physics, The Chemical Rubber Publishing Co., 1963. 11. J.N. Appleton, and J. Sharma, "Growth of Single Crystals of

  16. Nearly constant dielectric loss behavior in poly(3-hydroxybutyrate-co-3-hydroxyvalerate) biodegradable polyester

    NASA Astrophysics Data System (ADS)

    Ke, Shanming; Huang, Haitao; Ren, Li; Wang, Yingjun

    2009-05-01

    The measurement of dielectric spectroscopy over a broad frequency range of 0.01-107 Hz has been conducted to examine the segmental motions in poly[3-hydroxybutyrate-co-3-hydroxyvalerate] (PHBV) biopolymers. The ac conductivity at either low temperatures or high frequencies is almost temperature independent, indicating clearly that the nearly constant loss (NCL) phenomenon also takes place in polymers. The respective data were analyzed by adding a NCL term to the Jonscher relation. NCL in PHBV is discussed to be originated from the vibrational motion model. PHBV may have potential application as a biodegradable dielectric material.

  17. Dielectric constant and surface morphology of the elemental diffused polyimide

    NASA Astrophysics Data System (ADS)

    Majeed, Riyadh M. A. Abdul; Datar, A.; Bhoraskar, S. V.; Alegaonkar, P. S.; Bhoraskar, V. N.

    2006-11-01

    Polyimide (C22H10N2O5, PMDA-ODA, Kapton-H) samples were doped with phosphorous or boron and fluorine using the radiation assisted diffusion technique, with Co-60 gamma-rays over the dose range ~64 384 kGy, at room temperature. The diffusion of phosphorus and fluorine was confirmed by the RBS technique and that of boron by the neutron depth profiling technique. The elemental concentration on the surface was studied by the XPS technique. The relative concentration of phosphorus, fluorine and boron increased with increasing dose of gamma-rays. The dielectric constant, ɛ', of the polyimide increased by ~43% after phosphorus doping but decreased by ~33% after boron and fluorine doping. The increase in ɛ' is attributed to the radiation induced chemical coupling of the phosphorus atoms across the intra-molecular polyimide chains. The down shift in ɛ' is attributed to the decrease in the degree of electronic polarization and to the increase in the free volume due to the diffused boron or fluorine atoms. For all the doped samples the dielectric constant, ɛ', decreased very slowly with increasing frequency, over the range 100 Hz 7 MHz. AFM results reveal that the surface morphology and the roughness of the doped polyimide are appreciably different than that of virgin polyimide.

  18. Three dielectric constants and orientation order parameters in nematic mesophases

    NASA Astrophysics Data System (ADS)

    Yoon, Hyung Guen; Jeong, Seung Yeon; Kumar, Satyendra; Park, Min Sang; Park, Jung Ok; Srinivasarao, M.; Shin, Sung Tae

    2011-03-01

    Temperature dependence of the three components ɛ1 , ɛ2 , and ɛ3 of dielectric constant and orientation order parameters in the nematic phase of mesogens with rod, banana, and zero-order dendritic shape were measured using the in-plane and vertical switching geometries, and micro-Raman technique. Results on the well-known uniaxial (Nu) nematogens, E7 and 5CB, revealed two components ɛ1 = ~ɛ| | and ɛ2 = ~ɛ3 = ~ɛ⊥ , as expected. The three dielectric constants were different for two azo substituted (A131 and A103) and an oxadiazole based (ODBP-Ph-C12) bent core mesogens, and a Ge core tetrapode. In some cases, two of the components became the same indicating a loss of biaxiality at temperatures coinciding with the previously reported Nu to biaxial nematic transition. This interpretation is substantiated by micro-Raman measurements of the uniaxial and biaxial nematic order parameters. Supported by the US Department of Energy, Basic Energy Sciences grant ER46572 and by Samsung Electronics Corporation.

  19. Improved dielectric constant and breakdown strength of γ-phase dominant super toughened polyvinylidene fluoride/TiO2 nanocomposite film: an excellent material for energy storage applications and piezoelectric throughput.

    PubMed

    Alam, Md Mehebub; Ghosh, Sujoy Kumar; Sarkar, Debabrata; Sen, Shrabanee; Mandal, Dipankar

    2017-01-06

    Titanium dioxide (TiO2) nanoparticles (NPs) embedded γ-phase containing polyvinylidene fluoride (PVDF) nanocomposite (PNC) film turns to an excellent material for energy storage application due to an increased dielectric constant (32 at 1 kHz), enhanced electric breakdown strength (400 MV m(-1)). It also exhibits a high energy density of 4 J cm(-3) which is 25 times higher than that of virgin PVDF. 98% of the electroactive γ-phase has been acheived by the incorporation of TiO2 NPs and the resulting PNC behaves like a super-toughened material due to a dramatic improvement (more than 80%) in the tensile strength. Owing to their electroactive nature and extraordinary mechanical properties, PNC films have a strong ability to fabricate the piezoelectric nanogenerators (PNGs) that have recently been an area of focus regarding mechanical energy harvesting. The feasibility of piezoelectric voltage generation from PNGs is demostrated under the rotating fan that also promises further utility such as rotational speed (RPM) determination.

  20. Improved dielectric constant and breakdown strength of γ-phase dominant super toughened polyvinylidene fluoride/TiO2 nanocomposite film: an excellent material for energy storage applications and piezoelectric throughput

    NASA Astrophysics Data System (ADS)

    Mehebub Alam, Md; Ghosh, Sujoy Kumar; Sarkar, Debabrata; Sen, Shrabanee; Mandal, Dipankar

    2017-01-01

    Titanium dioxide (TiO2) nanoparticles (NPs) embedded γ-phase containing polyvinylidene fluoride (PVDF) nanocomposite (PNC) film turns to an excellent material for energy storage application due to an increased dielectric constant (32 at 1 kHz), enhanced electric breakdown strength (400 MV m-1). It also exhibits a high energy density of 4 J cm-3 which is 25 times higher than that of virgin PVDF. 98% of the electroactive γ-phase has been acheived by the incorporation of TiO2 NPs and the resulting PNC behaves like a super-toughened material due to a dramatic improvement (more than 80%) in the tensile strength. Owing to their electroactive nature and extraordinary mechanical properties, PNC films have a strong ability to fabricate the piezoelectric nanogenerators (PNGs) that have recently been an area of focus regarding mechanical energy harvesting. The feasibility of piezoelectric voltage generation from PNGs is demostrated under the rotating fan that also promises further utility such as rotational speed (RPM) determination.

  1. Millimeter-wave dielectric properties of infrared window materials

    NASA Astrophysics Data System (ADS)

    Ho, W. W.

    1987-01-01

    The millimeter-wave dielectric properties of a series of IR window materials were determined over the temperature range 23-1000 C. Materials studied included Al2O3, ZnS, ZnSe, aluminum oxynitride (ALON), and magnesium-spinel (MgAl2O4). These materials all exhibited fairly high millimeter-wave dielectric constants, but with essentially negligible room-temperature losses for most applications. However, both the dielectric constant and loss tangent increase significantly with increasing temperatures. The increases in dielectric constant with temperature can be analyzed in terms of a macroscopic dielectric virial expansion model, and are primarily due to the effective increase in volume for each polarizable unit of the material. Consequently, a strategy to overcome this degradation would be to search for new materials or composite structures with low thermal expansion coefficients. The observed millimeter-wave loss properties are characteristic of contributions from intergranular impurities and show an onset of increased absorption at about 500. However, even at 1000 C, typical loss tangents are still below 0.05, and should be acceptable in most millimeter-wave window applications for reasonable thicknesses.

  2. Application of FEM to estimate complex permittivity of dielectric material at microwave frequency using waveguide measurements

    NASA Technical Reports Server (NTRS)

    Deshpande, M. D.; Reddy, C. J.

    1995-01-01

    A simple waveguide measurement technique is presented to determine the complex dielectric constant of a dielectric material. The dielectric sample is loaded in a shorted x-band rectangular waveguide. Using a network analyzer; the reflection coefficient of the shorted waveguide (loaded with sample) is measured. Using the Finite Element Method (FEM), the exact reflection coefficient of the shorted waveguide (loaded with sample) is determined as a function of the dielectric constant. Matching the measured value of the reflection coefficient with the reflection coefficient calculated using the FEM utilizing the Newton-Raphson Method, an estimate of the dielectric constant of a dielectric material is obtained. A comparison of estimated values of dielectric constant obtained from simple waveguide modal theory and the present approach is presented.

  3. An Explanation of the Photoinduced Giant Dielectric Constant of Lead Halide Perovskite Solar Cells.

    PubMed

    Almond, Darryl P; Bowen, Chris R

    2015-05-07

    A photoinduced giant dielectric constant of ~10(6) has been found in impedance spectroscopy measurements of lead halide perovskite solar cells. We report similar effects in measurements of a porous lead zirconate titanate (PZT) sample saturated with water. The principal effect of the illumination of the solar cell and of the introduction of water into the pore volume of the PZT sample is a significant increase in conductivity and dielectric loss. This is shown to exhibit low frequency power law dispersion. Application of the Kramers-Kronig relationships show the large measured values of permittivity to be related to the power law changes in conductivity and dielectric loss. The power law dispersions in the electrical responses are consistent with an electrical network model of microstructure. It is concluded that the high apparent values of permittivity are features of the microstructural networks and not fundamental effects in the two perovskite materials.

  4. Thin film dielectric composite materials

    DOEpatents

    Jia, Quanxi; Gibbons, Brady J.; Findikoglu, Alp T.; Park, Bae Ho

    2002-01-01

    A dielectric composite material comprising at least two crystal phases of different components with TiO.sub.2 as a first component and a material selected from the group consisting of Ba.sub.1-x Sr.sub.x TiO.sub.3 where x is from 0.3 to 0.7, Pb.sub.1-x Ca.sub.x TiO.sub.3 where x is from 0.4 to 0.7, Sr.sub.1-x Pb.sub.x TiO.sub.3 where x is from 0.2 to 0.4, Ba.sub.1-x Cd.sub.x TiO.sub.3 where x is from 0.02 to 0.1, BaTi.sub.1-x Zr.sub.x O.sub.3 where x is from 0.2 to 0.3, BaTi.sub.1-x Sn.sub.x O.sub.3 where x is from 0.15 to 0.3, BaTi.sub.1-x Hf.sub.x O.sub.3 where x is from 0.24 to 0.3, Pb.sub.1-1.3x La.sub.x TiO.sub.3+0.2x where x is from 0.23 to 0.3, (BaTiO.sub.3).sub.x (PbFeo.sub.0.5 Nb.sub.0.5 O.sub.3).sub.1-x where x is from 0.75 to 0.9, (PbTiO.sub.3).sub.- (PbCo.sub.0.5 W.sub.0.5 O.sub.3).sub.1-x where x is from 0.1 to 0.45, (PbTiO.sub.3).sub.x (PbMg.sub.0.5 W.sub.0.5 O.sub.3).sub.1-x where x is from 0.2 to 0.4, and (PbTiO.sub.3).sub.x (PbFe.sub.0.5 Ta.sub.0.5 O.sub.3).sub.1-x where x is from 0 to 0.2, as the second component is described. The dielectric composite material can be formed as a thin film upon suitable substrates.

  5. Use of Amorphous Oxides as High Temperature Dielectric Material in Wound Capacitors (PREPRINT)

    DTIC Science & Technology

    2008-02-01

    produce a capacitor. Capacitors fabricated using amorphous silicon dioxide as the dielectric have been shown to have stable capacitance...a higher dielectric constant in order to improve the energy density. These materials include hafnium dioxide and zirconium dioxide . Initial results...TERMS capacitor, dissipation factor, breakdown threshold, silicon dioxide , zirconium dioxide and dielectric 16. SECURITY CLASSIFICATION OF: 17

  6. Dielectric Constant Measurements on Lunar Soils and Terrestrial Minerals

    NASA Technical Reports Server (NTRS)

    Anderson, R. C.; Buehler, M. G.; Seshardri, S.; Schaap, M. G.

    2004-01-01

    The return to the Moon has ignited the need to characterize the lunar regolith using in situ methods. An examination of the lunar regolith samples collected by the Apollo astronauts indicates that only a few minerals (silicates and oxides) need be considered for in situ resource utilization (ISRU). This simplifies the measurement requirements and allows a detailed analysis using simple methods. Characterizing the physical properties of the rocks and soils is difficult because of many complex parameters such as soil temperature, mineral type, grain size, porosity, and soil conductivity. In this presentation, we will show that the dielectric constant measurement can provide simple detection for oxides such as TiO2, FeO, and water. Their presence is manifest by an unusually large imaginary permittivity.

  7. Dielectric Loss Measurements on Raw Materials.

    ERIC Educational Resources Information Center

    Mwanje, J.

    1980-01-01

    Describes an experiment used to study dielectric properties of materials. Values of the dielectric loss tangent can be determined at low frequencies from Lissajous figures formed on an oscilloscope. Some mineral rock specimens show Debye-type relaxation peaks at frequencies in the region of 1 to 500 Hz. (Author/DS)

  8. Crosslinked polymeric dielectric materials and electronic devices incorporating same

    NASA Technical Reports Server (NTRS)

    Marks, Tobin J. (Inventor); Facchetti, Antonio (Inventor); Wang, Zhiming (Inventor); Choi, Hyuk-Jin (Inventor); Suh, legal representative, Nae-Jeong (Inventor)

    2012-01-01

    Solution-processable dielectric materials are provided, along with precursor compositions and processes for preparing the same. Composites and electronic devices including the dielectric materials also are provided.

  9. Flexible and transparent dielectric film with a high dielectric constant using chemical vapor deposition-grown graphene interlayer.

    PubMed

    Kim, Jin-Young; Lee, Jongho; Lee, Wi Hyoung; Kholmanov, Iskandar N; Suk, Ji Won; Kim, Taeyoung; Hao, Yufeng; Chou, Harry; Akinwande, Deji; Ruoff, Rodney S

    2014-01-28

    We have devised a dielectric film with a chemical vapor deposited graphene interlayer and studied the effect of the graphene interlayer on the dielectric performance. The highly transparent and flexible film was a polymer/graphene/polymer 'sandwich-structure' fabricated by a one-step transfer method that had a dielectric constant of 51, with a dielectric loss of 0.05 at 1 kHz. The graphene interlayer in the film forms a space charge layer, i.e., an accumulation of polarized charge carriers near the graphene, resulting in an induced space charge polarization and enhanced dielectric constant. The characteristic of the space charge layer for the graphene dielectric film, the sheet resistance of the graphene interlayer, was adjusted through thermal annealing that caused partial oxidation. The dielectric film with higher sheet resistance due to the oxidized graphene interlayer had a significantly lower dielectric constant compared to that with the graphene with lower interlayer sheet resistance. Oxidizing the graphene interlayer yields a smaller and thinner space charge density in the dielectric film, ultimately leading to decreased capacitance. Considering the simplicity of the fabrication process and high dielectric performance, as well as the high transparency and flexibility, this film is promising for applications in plastic electronics.

  10. Energy deposition characteristics of nanosecond dielectric barrier discharge plasma actuators: Influence of dielectric material

    NASA Astrophysics Data System (ADS)

    Correale, G.; Winkel, R.; Kotsonis, M.

    2015-08-01

    An experimental study aimed at the characterization of energy deposition of nanosecond Dielectric Barrier Discharge (ns-DBD) plasma actuators was carried out. Special attention was given on the effect of the thickness and material used for dielectric barrier. The selected materials for this study were polyimide film (Kapton), polyamide based nylon (PA2200), and silicone rubber. Schlieren measurements were carried out in quiescent air conditions in order to observe density gradients induced by energy deposited. Size of heated area was used to qualify the energy deposition coupled with electrical power measurements performed using the back-current shunt technique. Additionally, light intensity measurements showed a different nature of discharge based upon the material used for barrier, for a fixed thickness and frequency of discharge. Finally, a characterisation study was performed for the three tested materials. Dielectric constant, volume resistivity, and thermal conductivity were measured. Strong trends between the control parameters and the energy deposited into the fluid during the discharge were observed. Results indicate that efficiency of energy deposition mechanism relative to the thickness of the barrier strongly depends upon the material used for the dielectric barrier itself. In general, a high dielectric strength and a low volumetric resistivity are preferred for a barrier, together with a high heat capacitance and a low thermal conductivity coefficient in order to maximize the efficiency of the thermal energy deposition induced by an ns-DBD plasma actuator.

  11. Dielectric properties of amorphous phase-change materials

    NASA Astrophysics Data System (ADS)

    Chen, C.; Jost, P.; Volker, H.; Kaminski, M.; Wirtssohn, M.; Engelmann, U.; Krüger, K.; Schlich, F.; Schlockermann, C.; Lobo, R. P. S. M.; Wuttig, M.

    2017-03-01

    The dielectric function of several amorphous phase-change materials has been determined by employing a combination of impedance spectroscopy (9 kHz-3 GHz) and optical spectroscopy from the far- (20 c m-1 , 0.6 THz) to the near- (12 000 c m-1 , 360 THz) infrared, i.e., from the DC limit to the first interband transition. While phase-change materials undergo a change from covalent bonding to resonant bonding on crystallization, the amorphous and crystalline phases of ordinary chalcogenide semiconductors are both governed by virtually the same covalent bonds. Here, we study the dielectric properties of amorphous phase-change materials on the pseudobinary line between GeTe and S b2T e3 . These data provide important insights into the charge transport and the nature of bonding in amorphous phase-change materials. No frequency dependence of permittivity and conductivity is discernible in the impedance spectroscopy measurements. Consequently, there are no dielectric relaxations. The frequency-independent conductivity is in line with charge transport via extended states. The static dielectric constant significantly exceeds the optical dielectric constant. This observation is corroborated by transmittance measurements in the far infrared, which show optical phonons. From the intensity of these phonon modes, a large Born effective charge is derived. Nevertheless, it is known that crystalline phase-change materials such as GeTe possess even significantly larger Born effective charges. Crystallization is hence accompanied by a huge increase in the Born effective charge, which reveals a significant change of bonding upon crystallization. In addition, a clear stoichiometry trend in the static dielectric constant along the pseudobinary line between GeTe and S b2T e3 has been identified.

  12. Composite Dielectric Materials for Electrical Switching

    SciTech Connect

    Modine, F.A.

    1999-04-25

    Composites that consist of a dielectric host containing a particulate conductor as a second phase are of interest for electrical switching applications. Such composites are "smart" materials that can function as either voltage or current limiters, and the difference in fimction depends largely upon whether the dielectric is filled to below or above the percolation threshold. It also is possible to combine current and voltage limiting in a single composite to make a "super-smart" material.

  13. High aspect ratio patterning of photosensitive polyimide with low thermal expansion coefficient and low dielectric constant

    NASA Astrophysics Data System (ADS)

    Dick, Andrew R.; Bell, William K.; Luke, Brendan; Maines, Erin; Mueller, Brennen; Rawlings, Brandon; Kohl, Paul A.; Grant Willson, C.

    2016-07-01

    A photosensitive polyimide system based on amine catalyzed imidization of a precursor poly(amic ester) is described. The material is based on the meta ethyl ester of pyromellitic dianhydride and 2,2' bis(trifluoromethyl)benzidine. It acts as a negative tone resist when formulated with a photobase generator. The material exhibits a dielectric constant of 3.0 in the gigahertz range, a coefficient of thermal expansion of 6±2 ppm/K, and can be patterned to aspect ratios of >2 when formulated with a highly quantum efficient cinnamide type photobase generator.

  14. Structure and performance of dielectric films based on self-assembled nanocrystals with a high dielectric constant

    SciTech Connect

    Huang, LM; Liu, SY; Van Tassell, BJ; Liu, XH; Byro, A; Zhang, HN; Leland, ES; Akins, DL; Steingart, DA; Li, J; O'Brien, S

    2013-09-24

    Self-assembled films built from nanoparticles with a high dielectric constant are attractive as a foundation for new dielectric media with increased efficiency and range of operation, due to the ability to exploit nanofabrication techniques and emergent electrical properties originating from the nanoscale. However, because the building block is a discrete one-dimensional unit, it becomes a challenge to capture potential enhancements in dielectric performance in two or three dimensions, frequently due to surface effects or the presence of discontinuities. This is a recurring theme in nanoparticle film technology when applied to the realm of thin film semiconductor and device electronics. We present the use of chemically synthesized. (Ba; Sr)TiO3 nanocrystals, and a novel deposition-polymerization technique, as a means to fabricate the dielectric layer. The effective dielectric constant of the film is tunable according to nanoparticle size, and effective film dielectric constants of up to 34 are enabled. Wide area and multilayer dielectrics of up to 8 cm(2) and 190 nF are reported, for which the building block is an 8 nm nanocrystal. We describe models for assessing dielectric performance, and distinct methods for improving the dielectric constant of a nanocrystal thin film. The approach relies on evaporatively driven assembly of perovskite nanocrystals with uniform size distributions in a tunable 7-30 nm size range, coupled with the use of low molecular weight monomer/polymer precursor chemistry that can infiltrate the porous nanocrystal thin film network post assembly. The intercrystal void space (low k dielectric volume fraction) is minimized, while simultaneously promoting intercrystal connectivity and maximizing volume fraction of the high k dielectric component. Furfuryl alcohol, which has good affinity to the surface of. (Ba; Sr ) TiO3 nanocrystals and miscibility with a range of solvents, is demonstrated

  15. Dielectric Measurements of Millimeter-Wave Materials

    NASA Astrophysics Data System (ADS)

    Afsar, M. N.

    1984-12-01

    It is no longer necessary to use extrapolated microwave dielectric data when designing millimeter-wave components, devices, and systems. Precision measurements can now be made to generate highly accurate millimeter-wave (5 to 1/2 mm) continuous spectra on complex refractive index, complex dielectric permittivity, and loss tangent for a variety of materials such as common ceramics, semiconductors, crystalline, and glassy materials. The continuous spectra reveal an increase in dielectric loss with increase in frequency in this wavelength range for most materials. Reliable measurements also reveal that the method of preparation of nominally identical specimens can change the dielectric losses by many factors. These broad-band measurements were carried out employing dispersive Fourier transform spectroscopy applied to a modular two-beam polarization interferometer. Data obtained with Fabry-Perot open resonator methods at wavelengths of 5 mm and longer will also be compared.

  16. Dielectric constant measurement probe assembly and apparatus and method

    NASA Astrophysics Data System (ADS)

    Neel, Michael M.; Schiavone, Frank J.

    1992-10-01

    A dielectric constant measurement probe assembly includes a coaxial cable having an outer electrical conductor and a center electrical conductor extending within the outer conductor and terminating at an end portion which projects beyond an end portion of the outer conductor. An adapter member has a central passage receiving the coaxial cable with the outer conductor of the cable extending through the passage of the adapter member and projecting therefrom. An outer tube has a bore composed of first and second axial sections. The second bore section is smaller in diameter than the first bore section. The adapter member is inserted in the first bore section with the end portion of the coaxial cable outer conductor inserted into the second bore section and making electrical contact therewith such that the outer tube thus constitutes an extension of the outer conductor. A resonant rod is coupled with the end portion of the center conductor of the coaxial cable and an annular sleeve supports the resonant rod in the second bore section of the outer tube such that the rod constitutes an extension of the center conductor. The resonant rod and outer tube together define an open end of the coaxial cable such that the rod being capable of acting as a resonant structure upon energizing the coaxial cable produces fringing fields that protrude from the open end and penetrate a test sample disposed adjacent thereto.

  17. On the Dielectric Constant for Acetanilide: Experimental Measurements and Effect on Energy Transport

    NASA Astrophysics Data System (ADS)

    Careri, G.; Compatangelo, E.; Christiansen, P. L.; Halding, J.; Skovgaard, O.

    1987-01-01

    Experimental measurements of the dielectric constant for crystalline acetanilide powder for temperatures ranging from - 140°C to 20°C and for different hydration levels are presented. A Davydov-soliton computer model predicts dramatic changes in the energy transport and storage for typically increased values of the dielectric constant.

  18. Use of the finite-element method for a dielectric-constant gas-thermometry experiment

    NASA Astrophysics Data System (ADS)

    Zandt, T.; Gaiser, C.; Fellmuth, B.; Haft, N.; Thiele-Krivoi, B.; Kuhn, A.

    2013-09-01

    The finite-element method is a well-established computational methodology for the numerical treatment of partial differential equations. It is primarily used for solving problems in applied engineering and science. In previous publications, we have shown that the method is suitable to solve problems in temperature metrology, for instance to predict temperature profiles and thermal equilibration processes in complex measurement setups. In this paper, the method is used for a primary thermometry experiment, namely dielectric-constant gas thermometry. Within the framework of an international project directed to the new definition of the base unit kelvin, measurements were performed at the triple point of water in order to determine the Boltzmann constant k. The finite-element method was used for the data evaluation in different ways: calculation of the effective compressibility of the measuring capacitor by describing the deformation of its electrodes under the influence of the pressure of the gas, the dielectric constant of which has to be determined; calculation of resonance frequencies for the determination of the elastic constants of the electrode material by resonant ultrasound spectroscopy; electrostatic simulations for calculating capacitance values; estimation of uncertainty components, which allowed to draw conclusions concerning the future reduction of uncertainty components.

  19. Liquid Crystalline Epoxies with Lateral Substituents Showing a Low Dielectric Constant and High Thermal Conductivity

    NASA Astrophysics Data System (ADS)

    Guo, Huilong; Lu, Mangeng; Liang, Liyan; Wu, Kun; Ma, Dong; Xue, Wei

    2017-02-01

    In this work, liquid crystalline epoxies with lateral substituents were synthesized and cured with aromatic amines or anhydride. The liquid crystalline phase structure of liquid crystalline epoxies with lateral substituents was determined by polarized optical microscopy. The relationship between thermal conductivity and dielectric properties and liquid crystalline domain structure was discussed in the paper. The samples show high thermal conductivity up to 0.29 W/(m × K), due to the orientation of mesogenic units in epoxies. The sample's low dielectric constant of 2.29 is associated with the oriented mesogenic units and long nonpolar lateral substituents. This indicates a new way to obtain materials with high thermal conductivity and a low dielectric constant by introducing oriented mesogenic units into cross-linked epoxy systems. The water repellency is reflected in the contact angles of 92-98°, which are apparently higher than that of conventional epoxy systems. It was also found that the better toughness of liquid crystalline epoxies with lateral substituents was attributed to the existence of long flexible alkyl lateral substituents.

  20. Tailorable Dielectric Material with Complex Permittivity Characteristics

    NASA Technical Reports Server (NTRS)

    Dudley, Kenneth L. (Inventor); Elliott, Holly A (Inventor); Connell, John W. (Inventor); Smith, Joseph G. (Inventor); Ghose, Sayata (Inventor); Watson, Kent A. (Inventor); Delozier, Donavon Mark (Inventor)

    2014-01-01

    A dielectric material includes a network of nanosubstrates, such as but not limited to nanotubes, nanosheets, or other nanomaterials or nanostructures, a polymer base material or matrix, and nanoparticles constructed at least partially of an elemental metal. The network has a predetermined nanosubstrate loading percentage by weight with respect to a total weight of the dielectric material, and a preferential or predetermined longitudinal alignment with respect to an orientation of an incident electrical field. A method of forming the dielectric material includes depositing the metal-based nanoparticles onto the nanosubstrates and subsequently mixing these with a polymer matrix. Once mixed, alignment can be achieved by melt extrusion or a similar mechanical shearing process. Alignment of the nanosubstrate may be in horizontal or vertical direction with respect to the orientation of an incident electrical field.

  1. Three-phase percolative silver-BaTiO3-epoxy nanocomposites with high dielectric constants

    SciTech Connect

    Qi, Lai; Lee, Burtrand I.; Samuels, William D.; Exarhos, Gregory J.; Parker, Sam G.

    2006-08-01

    A three-phase epoxy-based composite with randomly distributed Ag nanoparticles and BaTiO3 particles was synthesized in this work. By integrating Ag nanoparticles into the epoxy resin, the dielectric properties of the resin is significantly enhanced, which provides an ideal host for further mixing with BaTiO3 to prepare high-dielectric-constant polymer-based dielectrics. The devices that adopt these composites demonstrate high relative dielectric constants (?r ? 450) at room temperature, which is 110 times higher than that of the epoxy matrix. These nanocomposites were found with potential to be applied in the embedded capacitor applications.

  2. Development of low dielectric constant alumina-based ceramics for microelectronic substrates

    SciTech Connect

    Wu, Shun Jackson

    1993-05-01

    The performance of high speed computers depends not only on IC chips, but also on the signal propagation speed between these chips. The signal propagation delay in a computer is determined by the dielectric constant of the substrate material to which the IC chips are attached. In this study, a ceramic substrate with a low dielectric constant (k ≈ 5.0) has been developed. When compared with the traditional alumina substrate (k ≈ 10.0), the new material corresponds to a 37% decrease in the signal propagation delay. Glass hollow spheres are used to introduce porosity (k = 1.0) to the alumina matrix in a controlled manner. A surface coating technique via heterogeneous nucleation in aqueous solution has been used to improve the high temperature stability of these spheres. After sintering at 1,400 C, isolated spherical pores are uniformly distributed in the almost fully dense alumina matrix; negligible amounts of matrix defects can be seen. All pores are isolated from each other. Detailed analyses of the chemical composition find that the sintered sample consists of α-alumina, mullite and residual glass. Mullite is the chemical reaction product of alumina and the glass spheres. Residual glass exists because current firing conditions do not complete the mullitization reaction. The dielectric constant of the sintered sample is measured and then compared with the predicted value using Maxwell`s model. Mechanical strength is evaluated by a four-point bending test. Although the flexural strength decreases exponentially with porosity, samples with 34% porosity (k ≈ 5.0) still maintain adequate mechanical strength for the proper operation of a microelectronic substrate.

  3. Theoretical Study of the Transverse Dielectric Constant of Superlattices and Their Alloys. Ph.D Thesis

    NASA Technical Reports Server (NTRS)

    Kahen, K. B.

    1986-01-01

    The optical properties of III to V binary and ternary compounds and GaAs-Al(x)Ga(1-x)As superlattices are determined by calculating the real and imaginary parts of the transverse dielectric constant. Emphasis is given to determining the influence of different material and superlattice parameters on the values of the index of refraction and absorption coefficient. In order to calculate the optical properties of a material, it is necessary to compute its electronic band structure. This was accomplished by introducing a partition band structure approach based on a combination of the vector k x vector p and nonlocal pseudopotential techniques. The advantages of this approach are that it is accurate, computationally fast, analytical, and flexible. These last two properties enable incorporation of additional effects into the model, such as disorder scattering, which occurs for alloy materials and excitons. Furthermore, the model is easily extended to more complex structures, for example multiple quantum wells and superlattices. The results for the transverse dielectric constant and absorption coefficient of bulk III to V compounds compare well with other one-electron band structure models and the calculations show that for small frequencies, the index of refraction is determined mainly by the contibution of the outer regions of the Brillouin zone.

  4. General theory of the transverse dielectric constant of III-V semiconducting compounds

    NASA Technical Reports Server (NTRS)

    Kahen, K. B.; Leburton, J. P.

    1985-01-01

    A general model of the transverse dielectric constant of III-V compounds is developed using a hybrid method which combines the kp method with a nonlocal pseudopotential calculation. In this method the Brillouin zone is partitioned into three regions by expanding the energy bands and matrix elements about the F, X, and L symmetry points. The real and imaginary parts of the dielectric constant are calculated as a sum of the individual contributions of each region. By using this partition method, it is possible to get good insight into the dependence of the dielectric constant on the shape of the band structure.

  5. Complex dielectric constant of various biomolecules as a function of wavelength using surface plasmon resonance

    NASA Astrophysics Data System (ADS)

    Paliwal, Ayushi; Tomar, Monika; Gupta, Vinay

    2014-07-01

    Present study focuses on determination of complex dielectric constant of biomolecules as function of frequency by means of surface plasmon resonance (SPR) technique without losing their biofunctionality. Surface plasmon modes have been excited in Kretschmann configuration at interface of ZnO-Au thin films. Various biomolecules (glucose oxidase, cholesterol oxidase, urease, and uricase) have been immobilized successfully on surface of ZnO thin film by electrostatic interaction. SPR reflectance curves for all biomolecules were recorded separately at different wavelengths (407-635 nm). Complex dielectric constant was determined by fitting the experimental SPR data with Fresnel's equations. Dielectric constant of all biomolecules shows frequency dispersion and attributed to ionic polarization.

  6. New Advanced Dielectric Materials for Accelerator Applications

    SciTech Connect

    Kanareykin, A.

    2010-11-04

    We present our recent results on the development and experimental testing of advanced dielectric materials that are capable of supporting the high RF electric fields generated by electron beams or pulsed high power microwaves. These materials have been optimized or specially designed for accelerator applications. The materials discussed here include low loss microwave ceramics, quartz, Chemical Vapor Deposition diamonds and nonlinear Barium Strontium Titanate based ferroelectrics.

  7. Structure and performance of dielectric films based on self-assembled nanocrystals with a high dielectric constant

    NASA Astrophysics Data System (ADS)

    Huang, Limin; Liu, Shuangyi; Van Tassell, Barry J.; Liu, Xiaohua; Byro, Andrew; Zhang, Henan; Leland, Eli S.; Akins, Daniel L.; Steingart, Daniel A.; Li, Jackie; O'Brien, Stephen

    2013-10-01

    Self-assembled films built from nanoparticles with a high dielectric constant are attractive as a foundation for new dielectric media with increased efficiency and range of operation, due to the ability to exploit nanofabrication techniques and emergent electrical properties originating from the nanoscale. However, because the building block is a discrete one-dimensional unit, it becomes a challenge to capture potential enhancements in dielectric performance in two or three dimensions, frequently due to surface effects or the presence of discontinuities. This is a recurring theme in nanoparticle film technology when applied to the realm of thin film semiconductor and device electronics. We present the use of chemically synthesized (Ba,Sr)TiO3 nanocrystals, and a novel deposition-polymerization technique, as a means to fabricate the dielectric layer. The effective dielectric constant of the film is tunable according to nanoparticle size, and effective film dielectric constants of up to 34 are enabled. Wide area and multilayer dielectrics of up to 8 cm2 and 190 nF are reported, for which the building block is an 8 nm nanocrystal. We describe models for assessing dielectric performance, and distinct methods for improving the dielectric constant of a nanocrystal thin film. The approach relies on evaporatively driven assembly of perovskite nanocrystals with uniform size distributions in a tunable 7-30 nm size range, coupled with the use of low molecular weight monomer/polymer precursor chemistry that can infiltrate the porous nanocrystal thin film network post assembly. The intercrystal void space (low k dielectric volume fraction) is minimized, while simultaneously promoting intercrystal connectivity and maximizing volume fraction of the high k dielectric component. Furfuryl alcohol, which has good affinity to the surface of (Ba,Sr)TiO3 nanocrystals and miscibility with a range of solvents, is demonstrated to be ideal for the production of nanocomposites. The

  8. Critical role of morphology on the dielectric constant of semicrystalline polyolefins.

    PubMed

    Misra, Mayank; Mannodi-Kanakkithodi, Arun; Chung, T C; Ramprasad, Rampi; Kumar, Sanat K

    2016-06-21

    A particularly attractive method to predict the dielectric properties of materials is density functional theory (DFT). While this method is very popular, its large computational requirements allow practical treatments of unit cells with just a small number of atoms in an ordered array, i.e., in a crystalline morphology. By comparing DFT and Molecular Dynamics (MD) simulations on the same ordered arrays of functional polyolefins, we confirm that both methodologies yield identical estimates for the dipole moments and hence the ionic component of the dielectric storage modulus. Additionally, MD simulations of more realistic semi-crystalline morphologies yield estimates for this polar contribution that are in good agreement with the limited experiments in this field. However, these predictions are up to 10 times larger than those for pure crystalline simulations. Here, we show that the constraints provided by the surrounding chains significantly impede dipolar relaxations in the crystalline regions, whereas amorphous chains must sample all configurations to attain their fully isotropic spatial distributions. These results, which suggest that the amorphous phase is the dominant player in the context, argue strongly that the proper polymer morphology needs to be modeled to ensure accurate estimates of the ionic component of the dielectric constant.

  9. Dielectric constant of liquids confined in the extended nanospace measured by a streaming potential method.

    PubMed

    Morikawa, Kyojiro; Kazoe, Yutaka; Mawatari, Kazuma; Tsukahara, Takehiko; Kitamori, Takehiko

    2015-02-03

    Understanding liquid structure and the electrical properties of liquids confined in extended nanospaces (10-1000 nm) is important for nanofluidics and nanochemistry. To understand these liquid properties requires determination of the dielectric constant of liquids confined in extended nanospaces. A novel dielectric constant measurement method has thus been developed for extended nanospaces using a streaming potential method. We focused on the nonsteady-state streaming potential in extended nanospaces and successfully measured the dielectric constant of liquids within them without the use of probe molecules. The dielectric constant of water was determined to be significantly reduced by about 3 times compared to that of the bulk. This result contributes key information toward further understanding of the chemistry and fluidics in extended nanospaces.

  10. The effect of diamic acid additives on the dielectric constant of polyimides

    NASA Technical Reports Server (NTRS)

    Stoakley, Diane M.; St. Clair, Anne K.

    1988-01-01

    The effect of six selected diamic acids additives (including 2,2-prime bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride-aniline (An); 4,4-prime-oxydiphthalic anhydride-An, 3,3-prime diaminodiphenyl sulfone-phthalic anhydride (PA); 4,4-prime-oxydianiline-PA; 2,2-bis 4(4-aminophenoxy)phenyl hexafluoropropane-PA; and 2,2-bis 4(3-aminophenoxy)phenyl hexafluoropropane-PA) on the dielectric constants of low-dielectric-constant polyimide resins was evaluated. It was found that the effect of the incorporation of the diamic acids on reducing the dielectric constant of polyimides may be limited as the dielectric constant of the base resin itself becomes very low. The additives were found to lower the resin's values of glass transition temperature, with no effect on thermooxidative stability.

  11. High performance dielectric materials development

    NASA Astrophysics Data System (ADS)

    Piche, Joe; Kirchner, Ted; Jayaraj, K.

    1994-09-01

    The mission of polymer composites materials technology is to develop materials and processing technology to meet DoD and commercial needs. The following are outlined in this presentation: high performance capacitors, high temperature aerospace insulation, rationale for choosing Foster-Miller (the reporting industry), the approach to the development and evaluation of high temperature insulation materials, and the requirements/evaluation parameters. Supporting tables and diagrams are included.

  12. High performance dielectric materials development

    NASA Technical Reports Server (NTRS)

    Piche, Joe; Kirchner, Ted; Jayaraj, K.

    1994-01-01

    The mission of polymer composites materials technology is to develop materials and processing technology to meet DoD and commercial needs. The following are outlined in this presentation: high performance capacitors, high temperature aerospace insulation, rationale for choosing Foster-Miller (the reporting industry), the approach to the development and evaluation of high temperature insulation materials, and the requirements/evaluation parameters. Supporting tables and diagrams are included.

  13. High-throughput screening of inorganic compounds for the discovery of novel dielectric and optical materials.

    PubMed

    Petousis, Ioannis; Mrdjenovich, David; Ballouz, Eric; Liu, Miao; Winston, Donald; Chen, Wei; Graf, Tanja; Schladt, Thomas D; Persson, Kristin A; Prinz, Fritz B

    2017-01-31

    Dielectrics are an important class of materials that are ubiquitous in modern electronic applications. Even though their properties are important for the performance of devices, the number of compounds with known dielectric constant is on the order of a few hundred. Here, we use Density Functional Perturbation Theory as a way to screen for the dielectric constant and refractive index of materials in a fast and computationally efficient way. Our results constitute the largest dielectric tensors database to date, containing 1,056 compounds. Details regarding the computational methodology and technical validation are presented along with the format of our publicly available data. In addition, we integrate our dataset with the Materials Project allowing users easy access to material properties. Finally, we explain how our dataset and calculation methodology can be used in the search for novel dielectric compounds.

  14. High-throughput screening of inorganic compounds for the discovery of novel dielectric and optical materials

    PubMed Central

    Petousis, Ioannis; Mrdjenovich, David; Ballouz, Eric; Liu, Miao; Winston, Donald; Chen, Wei; Graf, Tanja; Schladt, Thomas D.; Persson, Kristin A.; Prinz, Fritz B.

    2017-01-01

    Dielectrics are an important class of materials that are ubiquitous in modern electronic applications. Even though their properties are important for the performance of devices, the number of compounds with known dielectric constant is on the order of a few hundred. Here, we use Density Functional Perturbation Theory as a way to screen for the dielectric constant and refractive index of materials in a fast and computationally efficient way. Our results constitute the largest dielectric tensors database to date, containing 1,056 compounds. Details regarding the computational methodology and technical validation are presented along with the format of our publicly available data. In addition, we integrate our dataset with the Materials Project allowing users easy access to material properties. Finally, we explain how our dataset and calculation methodology can be used in the search for novel dielectric compounds. PMID:28140408

  15. High-throughput screening of inorganic compounds for the discovery of novel dielectric and optical materials

    NASA Astrophysics Data System (ADS)

    Petousis, Ioannis; Mrdjenovich, David; Ballouz, Eric; Liu, Miao; Winston, Donald; Chen, Wei; Graf, Tanja; Schladt, Thomas D.; Persson, Kristin A.; Prinz, Fritz B.

    2017-01-01

    Dielectrics are an important class of materials that are ubiquitous in modern electronic applications. Even though their properties are important for the performance of devices, the number of compounds with known dielectric constant is on the order of a few hundred. Here, we use Density Functional Perturbation Theory as a way to screen for the dielectric constant and refractive index of materials in a fast and computationally efficient way. Our results constitute the largest dielectric tensors database to date, containing 1,056 compounds. Details regarding the computational methodology and technical validation are presented along with the format of our publicly available data. In addition, we integrate our dataset with the Materials Project allowing users easy access to material properties. Finally, we explain how our dataset and calculation methodology can be used in the search for novel dielectric compounds.

  16. High dielectric constant nickel-doped titanium oxide films prepared by liquid-phase deposition

    NASA Astrophysics Data System (ADS)

    Lee, Ming-Kwei; Yen, Chih-Feng; Fan, Cho-Han

    2014-09-01

    The electrical characteristics of nickel-doped titanium oxide films prepared by liquid-phase deposition on p-type (100) silicon substrate were investigated. The aqueous solutions of ammonium hexafluorotitanate and boric acid were used as precursors for the growth of titanium oxide films and the dielectric constant is 29. The dielectric constant can be improved to 94 by nickel doping at the thermal annealing at 700 °C in nitrous oxide.

  17. Open-access dielectric elastomer material database

    NASA Astrophysics Data System (ADS)

    Vertechy, R.; Fontana, M.; Stiubianu, G.; Cazacu, M.

    2014-03-01

    Dielectric Elastomer Transducers (DETs) are deformable capacitors that can be used as sensors, actuators and generators. The design of effective and optimized DETs requires the knowledge of a set of relevant properties of the employed Dielectric Elastomer (DE) material, which make it possible to accurately predict their electromechanical dynamic behavior. In this context, an open-access database for DE materials has been created with the aim of providing the practicing engineer with the essential information for the design and optimization of new kinds of DET. Among the electrical properties, dielectric susceptibility, dielectric strength and conductivity are considered along with their dependence on mechanical strain. As regards mechanical behavior, experimental stress-strain curves are provided to predict hyperelasticity, plasticity, viscosity, Mullins effect and mechanical rupture. Properties of commercial elastomeric membranes have been entered in the database and made available to the research community. This paper describes the instrumentations, experimental setups and procedures that have been employed for the characterization of the considered DE materials. To provide an example, the experimental data acquired for a commercially available natural rubber membrane (OPPO Band Red 8012) are presented.

  18. RESEARCH NOTE Static dielectric constant of the polarizable NCC water model

    NASA Astrophysics Data System (ADS)

    Millot, Jean-Christophe Soetens Marilia T. C. Martins Costa Claude

    The static dielectric constant epsilon0 of the ab initio water model NCC including polarizability (Niesar, U., Corongiu, G., Clementi, E., Kneller, G. R., and Bhattacharya, D. K., 1990, J. phys. Chem., 94, 7949) has been computed by molecular dynamics simulation at 25oC and a density of 1gcm-3. The long range electrostatic interactions are taken into account by the reaction field method. Values of 100 8 and 8ps are found for the static dielectric constant and dielectric relaxation time, respectively.

  19. The dielectric constant of water. Computer simulations with the MCY potential

    NASA Astrophysics Data System (ADS)

    Neumann, Martin

    1985-06-01

    Despite the sizable literature on computer simulations of water and aqueous solutions, very little is known about one of the most interesting properties of water, namely its dielectric constant. In this paper it is demonstrated that the methodological as well as technological problems that have hitherto impeded the calculation of dielectric properties of realistic model systems have now been overcome. Using a small dedicated array processor, a series of extensive simulations with the MCY (Matsuoka-Clementi-Yoshimine) potential for water have been performed in reaction field geometry, and it is shown that consistent (i.e., free from boundary effects) and accurate results may be obtained for the full frequency-dependent dielectric constant, from the static up to the submillimeter range. At the same time it is found that the rather popular MCY model is not able to satisfactorily reproduce the dielectric properties of real water: Both the static dielectric constant and the principal dielectric relaxation time are much lower than the experimental values, and the temperature dependence of the Kirkwood g factor has the wrong sign. It is concluded that in the future the calculation of the dielectric constant, being a measure of orientational correlations between molecules, will play an important part in assessing the reliability of model potentials for water.

  20. A theory of electrical conductivity, dielectric constant, and electromagnetic interference shielding for lightweight graphene composite foams

    NASA Astrophysics Data System (ADS)

    Xia, Xiaodong; Wang, Yang; Zhong, Zheng; Weng, George J.

    2016-08-01

    This work was driven by the need to understand the electromagnetic interference (EMI) shielding effectiveness (SE) of light weight, flexible, and high performance graphene composite foams, but as EMI SE of a material depends on its electrical conductivity, dielectric permittivity, and magnetic permeability, the investigation of these three properties also became a priority. In this paper, we first present a continuum theory to determine these three electromagnetic properties, and then use the obtained properties to evaluate the EMI SE of the foam. A two-scale composite model is conceived to evaluate these three properties, with the large one being the skeleton-void composite and the small one being the graphene-polymer composite that serves as the skeleton of the foam. To evaluate the properties of the skeleton, the effective-medium approach is taken as the starting point. Subsequently, the effect of an imperfect interface and the contributions of electron tunneling to the interfacial conductivity and Maxwell-Wagner-Sillars polarization mechanism to the dielectric constant are also implemented. The derived skeleton properties are then utilized on the large scale to determine the three properties of the composite foam at a given porosity. Then a uniform plane electromagnetic wave is considered to evaluate the EMI SE of the foam. It is demonstrated that the electrical conductivity, dielectric constant, and EMI SE of the foam calculated from the developed theory are in general agreement with the reported experimental data of graphene/PDMS composite foams. The theory is further proven to be valid for the EMI SE of solid graphene/epoxy and solid carbon nanotube/epoxy nanocomposites. It is also shown that, among the three electromagnetic properties, electrical conductivity has the strongest influence on the EMI shielding effectiveness.

  1. Cu-Induced Dielectric Breakdown of Porous Low-Dielectric-Constant Film

    NASA Astrophysics Data System (ADS)

    Cheng, Yi-Lung; Lee, Chih-Yen; Huang, Yao-Liang; Sun, Chung-Ren; Lee, Wen-Hsi; Chen, Giin-Shan; Fang, Jau-Shiung; Phan, Bach Thang

    2017-02-01

    Dielectric breakdown induced by Cu ion migration in porous low-k dielectric films has been investigated in alternating-polarity bias conditions using a metal-insulator-metal capacitor with Cu top metal electrode. The experimental results indicated that Cu ions migrated into the dielectric film under stress with positive polarity, leading to weaker dielectric strength and shorter time to failure (TTF). In the alternating-polarity test, the measured TTFs increased with decreasing stressing frequency, implying backward migration of Cu ions during reverse-bias stress. Additionally, compared with a direct-current stress condition, the measured TTFs were higher as the frequency was decreased to 10-2 Hz. The electric-field acceleration factor for porous low-k dielectric film breakdown in the alternating-polarity test was also found to increase. This Cu backward migration effect is effective when the stressing time under negative polarity is longer than 0.1 s.

  2. An investigation of the relationship between tree water potential and dielectric constant

    NASA Technical Reports Server (NTRS)

    Mcdonald, Kyle C.; Zimmermann, Reiner; Way, Jobea; Oren, Ram

    1992-01-01

    An experiment that has been performed to verify the relationship between the dielectric constant of several tree species and their respective water potentials is described. The water potential, xylem flow and dielectric properties of five tree species were continuously monitored while simultaneously manipulating canopy transpiration and water status. An analysis of the data recorded during these manipulations is presented. Results of this analysis demonstrate a clear coincidence of change in dielectric constant and water status. The implication of this relationship for the utilization of remotely sensed data to study canopy water relations is explored. Preliminary backscatter modeling results demonstrate that the changes in dielectric constant that occur as a result of changes in water status are significant enough to be observable with microwave radar.

  3. Dielectric constant of ices and water: a lesson about water interactions.

    PubMed

    Aragones, J L; MacDowell, L G; Vega, C

    2011-06-16

    In this paper, the dielectric constant has been evaluated for ices Ih, III, V, VI, and VII for several water models using two different methodologies. Using Monte Carlo simulations, with special moves to sample proton-disordered configurations, the dielectric constant has been rigorously evaluated. We also used an approximate route in which proton-disordered configurations satisfying the Bernal-Fowler rules were generated following the algorithm proposed by Buch et al. (Buch, V.; Sandler, P.; Sadlej, J. J. Phys. Chem. B 1998, 102, 8641), and the dielectric constant was estimated assuming that all configurations have the same statistical weight (as Pauling did when estimating the residual entropy of ice). The predictions of the Pauling model for the dielectric constant differ in general from those obtained rigorously by computer simulations because proton-disordered configurations satisfying the Bernal-Fowler rules can differ in their energies by as much as 0.10-0.30 NkT (at 243 K). These differences in energy significantly affect properties that vary from one configuration to another such as polarization, leading to different values of the dielectric constant. The Pauling predictions differ from the simulation results, especially for SPC/E and TIP5P, but yield reasonable results for TIP4P-like models. We suggest that for three charge models the polarization factor (G) in condensed phases depends on the ratio of the dipole to the quadrupole moment. The SPC/E, TIP5P, TIP4P, TIP4P/2005, TIP4P/ice models of water are unable to describe simultaneously both the experimental dielectric constants of water and ice Ih. Nonpolarizable models cannot describe the dielectric constants of the different condensed phases of water because their dipole moments (about 2.3 D) are much smaller that those estimated from first principles (of the order of 3 D). However, the predictions of TIP4P models provide an overall qualititatively correct description of the dielectric constant of the

  4. Image brightening in samples of high dielectric constant

    NASA Astrophysics Data System (ADS)

    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 4.0 T, in a cylindrical phantom of radius 9.25 cm, filled with 0.05 M 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

  5. Solving constant-coefficient differential equations with dielectric metamaterials

    NASA Astrophysics Data System (ADS)

    Zhang, Weixuan; Qu, Che; Zhang, Xiangdong

    2016-07-01

    Recently, the concept of metamaterial analog computing has been proposed (Silva et al 2014 Science 343 160-3). Some mathematical operations such as spatial differentiation, integration, and convolution, have been performed by using designed metamaterial blocks. Motivated by this work, we propose a practical approach based on dielectric metamaterial to solve differential equations. The ordinary differential equation can be solved accurately by the correctly designed metamaterial system. The numerical simulations using well-established numerical routines have been performed to successfully verify all theoretical analyses.

  6. Molecular Donor-Bridge-Acceptor Strategies for High-Capacitance Organic Dielectric Materials.

    PubMed

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

    2015-06-10

    Donor-bridge-acceptor (DBA) systems occupy a rich history in molecular electronics and photonics. A key property of DBA materials is their typically large and tunable (hyper)polarizabilities. While traditionally, classical descriptions such as the Clausius-Mossotti formalism have been used to relate molecular polarizabilities to bulk dielectric response, recent work has shown that these classical equations are inadequate for numerous materials classes. Creating high-dielectric organic materials is critically important for utilizing unconventional semiconductors in electronic circuitry. Employing a plane-wave density functional theory formalism, we investigate the dielectric response of highly polarizable DBA molecule-based thin films. Such films are found to have large dielectric response arising from cooperative effects between donor and acceptor units when mediated by a conjugated bridge. Moreover, the dielectric response can be systematically tuned by altering the building block donor, acceptor, or bridge structures and is found to be nonlinearly dependent on electric field strength. The computed dielectric constants are largely independent of the density functional employed, and qualitative trends are readily evident. Remarkably large computed dielectric constants >15.0 and capacitances >6.0 μF/cm(2) are achieved for squaraine monolayers, significantly higher than in traditional organic dielectrics. Such calculations should provide a guide for designing high-capacitance organic dielectrics that should greatly enhance transistor performance.

  7. Use of material dielectric properties for agricultural applications

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The use of dielectric properties of materials for applications in agriculture are reviewed, and research findings on use of dielectric heating of materials and on sensing of product moisture content and other quality factors are discussed. Dielectric heating applications, include treatment of seed...

  8. Use of material dielectric properties in agricultural applications

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The use of dielectric properties of materials for applications in agriculture are reviewed, and research findings on use of dielectric heating of materials and on sensing of product moisture content and other quality factors are discussed. Dielectric heating applications, include treatment of seed...

  9. A chemically triggered and thermally switched dielectric constant transition in a metal cyanide based crystal.

    PubMed

    Shi, Chao; Zhang, Xi; Cai, Ying; Yao, Ye-Feng; Zhang, Wen

    2015-05-18

    A dielectric constant transition is chemically triggered and thermally switched in (HPy)2[Na(H2O)Co(CN)6] (2, HPy=pyridinium cation) by single-crystal-to-single-crystal transformation and structural phase transition, respectively. Upon dehydration, (HPy)2[Na(H2O)2Co(CN)6] (1) transforms to its semi-hydrated form 2, accompanying a transition from a low-dielectric state to a high-dielectric state, and vice versa. This dielectric switch is also realized by a structural phase transition in 2 that occurs between room- and low-temperature phases, and which corresponds to high- and low-dielectric states, respectively. The switching property is due to the variation in the environment surrounding the HPy cation, that is, the hydrogen-bonding interactions and the crystal packing, which exert predominant influences on the dynamics of the cations that transit between the static and motional states.

  10. Dielectric constants and electrical conductivities of sodium dodecyl sulfate in aqueous solutions

    SciTech Connect

    Abe, M.; Ogino, K.

    1981-03-01

    Dielectric properties of sodium dodecyl sulfate in aqueous solution have been studied. The dielectric constant and ac electrical conductivity were measured in the frequency range 30 Hz to 6 MHz. At lower frequencies, with increasing concentrations of sodium dodecyl sulfate, dielectric properties were greatly affected by polarization on the surfaces of the electrode, the so-called space charge polarization. ac electrical conductivities were dependent on the concentration of sodium dodecyl sulfate at all frequencies. The activation energies of dc electrical conduction were much larger in the molecular state than in the aggregation state. The radius of a spherical particle with an electric double layer could be calculated through the measurement of dielectric constant and dc electrical conductivity. 18 references.

  11. Investigation of W-band dielectric constant of coals by free space method

    NASA Astrophysics Data System (ADS)

    Jia, Cheng-yan; Fan, Wei; Hu, Wei; Yang, Chuan-fa; Liu, Ling-yu; Chang, Tian-ying; Cui, Hong-liang

    2015-11-01

    The dielectric constant of Shandong anthracite coals of China was studied in the frequency range of 75~110 GHz (W-band), using the free space method for the first time. The measurement system is based on the Vector Network Analyzer of Agilent Technology and a VDI extension module with frequency range from 75 GHz to 110GHz. The dielectric constants of coals were calculated from the scattering parameters by implementing an algorithm. Correctness of the test results is verified by measuring the dielectric constant of air and timber. The dielectric constant of each selected coal with different moisture contents is investigated. It is found that both the real and imaginary parts of selected coals exhibit an apparent increasing trend with increasing water content of coals. The real part of coals with different water content varies from 2.61 to 4.97, and the imaginary part from 0.06 to 0.41 at the frequency of 110 GHz. We also obtained the diversification of the dielectric constant by increasing the frequency at the W-band. The real part of coals with different frequency varies from 3.85 to 3.91, and the imaginary part from 0.32 to 0.37 at W-band.

  12. Processable fluoropolymers with low dielectric constants: Preparation and structure-property relationships of polyacrylates and polymethacrylates

    SciTech Connect

    Hu, H. S.W.; Griffith, J.R.

    1993-12-31

    The preparation of a series of processable heavily fluorinated acrylic and methacrylic homo- and co-polymers with low dielectric constants is carried out to elucidate the structure-property relationships. The monomers were prepared through the condensation of the respective alcohols with acryloyl and methacryloyl chloride. Unlike tetrafluoroethylene, these monomers are easy to process into transparent polymers under normal conditions due to their liquid or semisolid nature. All polymers exhibit dielectric constants around 2.06-2.41 with variation within 0.03 over a frequency region of 500 MHz to 18.5 GHz. These values are very close to the minimum known dielectric constants of 2.0-2.08 for Teflon and 1.89-1.93 for Teflon AF. The factors which affect the dielectric constant include the fluorine content, the polymer type and molecular features. Lower dielectric constants are obtained as fluorine contents from polymer backbone or sidechain increase, when acrylate is replaced by methacrylate, when ether linkages are present in the fluorocarbon and when aromatic structure is symmetrically meta-substituted.

  13. Behavior of the dielectric constant of Ar near the critical point.

    PubMed

    Hidalgo, Marcelo; Coutinho, Kaline; Canuto, Sylvio

    2015-03-01

    The fundamental question of the behavior of the dielectric constant near the critical point is addressed using Ar as the probe system. The neighborhood of the liquid-vapor critical point of Ar is accessed by classical Monte Carlo simulation and then explicit quantum mechanics calculations are performed to study the behavior of the dielectric constant. The theoretical critical temperature is determined by calculating the position of the discontinuity of the specific heat and is found to be at T(c)Theor=148.7K, only 2 K below the experimental value. The large fluctuations and the inhomogeneity of the density that characterize the critical point rapidly disappear and are not seen at T=T(c)Theor+2K. The structure of Ar obtained by the radial distribution function is found to be in very good agreement with experiment both in the liquid phase and 2 K above the critical temperature. The behavior of the dielectric constant is then analyzed after calculating the static dipole polarizability and using a many-body Clausius-Mossotti equation. The dielectric constant shows a density-independent behavior around the critical density, 2 K above the critical temperature. At this point, the calculated value of the dielectric constant is 1.173±0.005 in excellent agreement with the experimental value of 1.179.

  14. Photoimageable Polyimide: A Dielectric Material For High Aspect Ratio Structures

    NASA Astrophysics Data System (ADS)

    Cech, Jay M.; Oprysko, Modest M.; Young, Peter L.; Li, Kin

    1986-07-01

    Polyimide has been identified as a useful material for microelectronic packaging because of its low dielectric constant and high temperature stability. Difficulties involved with reactive ion etching (RIE), a conventional technique for patterning thick polyimide films (thickness greater than 5 microns) with vertical walls, can be overcome by using photimageable polyimide precursors. The processing steps are similar to those used with negative photoresists. EM Chemical's HTR-3 photosensitive polyimide has been spun on up to a thickness of 12 microns. Exposure with a dose of 780 mJcm-2 of ultraviolet light, followed by spin development produces clean patterns as small as 5 microns corresponding to an aspect ratio of 2.4. When the patterned precursor is heated, an imidization reaction occurs converting the patterned film to polyimide. Baking to ca. 400 degrees C results in substantial loss in the thickness and in line width. However, shrinkage occurs reproducibly so useful rules for mask design can be formulated. Near vertical wall structures can be fabricated by taking advantage of the optical and shrinkage properties of the polyimide precursor. After development, an undercut wall profile can be produced since the bottom of the film receives less exposure and is hence more soluble in the developer. During heating, lateral shrinkage pulls the top of the film inward producing a vertical wall since the bottom is fixed to the substrate by adhesion. As a result, fully cured polyimide structures with straight walls and aspect ratios greater than one can be obtained. Dielectric properties of the fully imidized films were investigated with capacitor test structures. A relative dielectric constant of 3.3 and a loss tangent of .002 were measured at 20 kHz. It was also found that the dielectric constant increases as a linear function of relative humidity.

  15. Solution processable high dielectric constant nanocomposites based on ZrO2 nanoparticles for flexible organic transistors.

    PubMed

    Beaulieu, Michael R; Baral, Jayanta K; Hendricks, Nicholas R; Tang, Yuying; Briseño, Alejandro L; Watkins, James J

    2013-12-26

    A solution-based strategy for fabrication of high dielectric constant (κ) nanocomposites for flexible organic field effect transistors (OFETs) has been developed. The nanocomposite was composed of a high-κ polymer, cyanoethyl pullulan (CYELP), and a high-κ nanoparticle, zirconium dioxide (ZrO2). Organic field effect transistors (OFETs) based on neat CYELP exhibited anomalous behavior during device operation, such as large hysteresis and variable threshold voltages, which yielded inconsistent devices and poor electrical characteristics. To improve the stability of the OFET, we introduced ZrO2 nanoparticles that bind with residual functional groups on the high-κ polymer, which reduces the number of charge trapping sites. The nanoparticles, which serve as physical cross-links, reduce the hysteresis without decreasing the dielectric constant. The dielectric constant of the nanocomposites was tuned over the range of 15.6-21 by varying the ratio of the two components in the composite dielectrics, resulting in a high areal capacitance between 51 and 74 nF cm(-2) at 100 kHz and good insulating properties of a low leakage current of 1.8 × 10(-6) A cm(-2) at an applied voltage of -3.5 V (0.25 MV cm(-1)). Bottom-gate, top-contact (BGTC) low operating voltage p-channel OFETs using these solution processable high-κ nanocomposites were fabricated by a contact film transfer (CFT) technique with poly(3-hexylthiophene) (P3HT) as the charge transport layer. Field effect mobilities as high as 0.08 cm(2) V(-1) s(-1) and on/off current ratio of 1.2 × 10(3) for P3HT were measured for devices using the high-κ dielectric ZrO2 nanocomposite. These materials are promising for generating solution coatable dielectrics for low cost, large area, low operating voltage flexible transistors.

  16. Dielectric barrier discharge processing of aerospace materials

    NASA Astrophysics Data System (ADS)

    Scott, S. J.; Figgures, C. C.; Dixon, D. G.

    2004-08-01

    We report the use of atmospheric pressure, air based, dielectric barrier discharges (DBD) to treat materials commonly used in the aerospace industries. The material samples were processed using a test-bed of a conventional DBD configuration in which the sample formed one of the electrodes and was placed in close proximity to a ceramic electrode. The discharges generated a powerful, cold oxidizing environment which was able to remove organic contaminants, etch primer and paint layers, oxidize aluminium and roughen carbon fibre composites by the selective removal of resin.

  17. Spacecraft dielectric material properties and spacecraft charging

    NASA Technical Reports Server (NTRS)

    Frederickson, A. R.; Wall, J. A.; Cotts, D. B.; Bouquet, F. L.

    1986-01-01

    The physics of spacecraft charging is reviewed, and criteria for selecting and testing semiinsulating polymers (SIPs) to avoid charging are discussed and illustrated. Chapters are devoted to the required properties of dielectric materials, the charging process, discharge-pulse phenomena, design for minimum pulse size, design to prevent pulses, conduction in polymers, evaluation of SIPs that might prevent spacecraft charging, and the general response of dielectrics to space radiation. SIPs characterized include polyimides, fluorocarbons, thermoplastic polyesters, poly(alkanes), vinyl polymers and acrylates, polymers containing phthalocyanine, polyacene quinones, coordination polymers containing metal ions, conjugated-backbone polymers, and 'metallic' conducting polymers. Tables summarizing the results of SIP radiation tests (such as those performed for the NASA Galileo Project) are included.

  18. Process and Microstructure to Achieve Ultra-high Dielectric Constant in Ceramic-Polymer Composites

    PubMed Central

    Zhang, Lin; Shan, Xiaobing; Bass, Patrick; Tong, Yang; Rolin, Terry D.; Hill, Curtis W.; Brewer, Jeffrey C.; Tucker, Dennis S.; Cheng, Z.-Y.

    2016-01-01

    Influences of process conditions on microstructure and dielectric properties of ceramic-polymer composites are systematically studied using CaCu3Ti4O12 (CCTO) as filler and P(VDF-TrFE) 55/45 mol.% copolymer as the matrix by combining solution-cast and hot-pressing processes. It is found that the dielectric constant of the composites can be significantly enhanced–up to about 10 times – by using proper processing conditions. The dielectric constant of the composites can reach more than 1,000 over a wide temperature range with a low loss (tan δ ~ 10−1). It is concluded that besides the dense structure of composites, the uniform distribution of the CCTO particles in the matrix plays a key role on the dielectric enhancement. Due to the influence of the CCTO on the microstructure of the polymer matrix, the composites exhibit a weaker temperature dependence of the dielectric constant than the polymer matrix. Based on the results, it is also found that the loss of the composites at low temperatures, including room temperature, is determined by the real dielectric relaxation processes including the relaxation process induced by the mixing. PMID:27767184

  19. Process and Microstructure to Achieve Ultra-high Dielectric Constant in Ceramic-Polymer Composites

    NASA Astrophysics Data System (ADS)

    Zhang, Lin; Shan, Xiaobing; Bass, Patrick; Tong, Yang; Rolin, Terry D.; Hill, Curtis W.; Brewer, Jeffrey C.; Tucker, Dennis S.; Cheng, Z.-Y.

    2016-10-01

    Influences of process conditions on microstructure and dielectric properties of ceramic-polymer composites are systematically studied using CaCu3Ti4O12 (CCTO) as filler and P(VDF-TrFE) 55/45 mol.% copolymer as the matrix by combining solution-cast and hot-pressing processes. It is found that the dielectric constant of the composites can be significantly enhanced–up to about 10 times – by using proper processing conditions. The dielectric constant of the composites can reach more than 1,000 over a wide temperature range with a low loss (tan δ ~ 10‑1). It is concluded that besides the dense structure of composites, the uniform distribution of the CCTO particles in the matrix plays a key role on the dielectric enhancement. Due to the influence of the CCTO on the microstructure of the polymer matrix, the composites exhibit a weaker temperature dependence of the dielectric constant than the polymer matrix. Based on the results, it is also found that the loss of the composites at low temperatures, including room temperature, is determined by the real dielectric relaxation processes including the relaxation process induced by the mixing.

  20. Hybrid gate dielectric materials for unconventional electronic circuitry.

    PubMed

    Ha, Young-Geun; Everaerts, Ken; Hersam, Mark C; Marks, Tobin J

    2014-04-15

    Recent advances in semiconductor performance made possible by organic π-electron molecules, carbon-based nanomaterials, and metal oxides have been a central scientific and technological research focus over the past decade in the quest for flexible and transparent electronic products. However, advances in semiconductor materials require corresponding advances in compatible gate dielectric materials, which must exhibit excellent electrical properties such as large capacitance, high breakdown strength, low leakage current density, and mechanical flexibility on arbitrary substrates. Historically, conventional silicon dioxide (SiO2) has dominated electronics as the preferred gate dielectric material in complementary metal oxide semiconductor (CMOS) integrated transistor circuitry. However, it does not satisfy many of the performance requirements for the aforementioned semiconductors due to its relatively low dielectric constant and intransigent processability. High-k inorganics such as hafnium dioxide (HfO2) or zirconium dioxide (ZrO2) offer some increases in performance, but scientists have great difficulty depositing these materials as smooth films at temperatures compatible with flexible plastic substrates. While various organic polymers are accessible via chemical synthesis and readily form films from solution, they typically exhibit low capacitances, and the corresponding transistors operate at unacceptably high voltages. More recently, researchers have combined the favorable properties of high-k metal oxides and π-electron organics to form processable, structurally well-defined, and robust self-assembled multilayer nanodielectrics, which enable high-performance transistors with a wide variety of unconventional semiconductors. In this Account, we review recent advances in organic-inorganic hybrid gate dielectrics, fabricated by multilayer self-assembly, and their remarkable synergy with unconventional semiconductors. We first discuss the principals and functional

  1. Combining RAFT polymerization and thiol-ene click reaction for core-shell structured polymer@BaTiO3 nanodielectrics with high dielectric constant, low dielectric loss, and high energy storage capability.

    PubMed

    Yang, Ke; Huang, Xingyi; Zhu, Ming; Xie, Liyuan; Tanaka, Toshikatsu; Jiang, Pingkai

    2014-02-12

    Nanodielectric materials with high dielectric constant, low dielectric loss, and high energy storage capability are highly desirable in modern electric and electronics industries. It has been proved that the preparation of core-shell structured dielectric polymer nanocomposites via "grafting from" method is an effective approach to these materials. However, by using this approach, the deep understanding of the structure-dielectric property relationship of the core-shell structured nanodielectrics has been limited because of the lack of detailed information (e.g., molecular weight, grafting density) about the macromolecules grafted onto the nanoparticle surfaces. In this work, by the combination of reversible addition-fragmentation chain transfer (RAFT) polymerization and thiol-ene click reaction, two types of core-shell structured polymer@BaTiO3 (polymer@BT) nanocomposites with high dielectric constant and low dielectric loss were successfully prepared via a "grafting to" method. Compared with the "grafting from" method, this "grafting to" method has two merits: the molecular weight of the polymer chains in the shell layer can be easily controlled and the grafting density can be tailored by changing the molecular weight of the grafting polymer. Moreover, a clear insight into the relationship among the dielectric properties and energy storage capability of the core-shell structured polymer@BT nanocomposites, the molecular weight of the polymer chains, and the grafting density of the core-shell structured nanoparticles was achieved. The study provides new insights into the design and preparation of nanodielectric materials with desirable dielectric properties.

  2. Chemical and mineral composition of dust and its effect on the dielectric constant

    SciTech Connect

    Sharif, S.

    1995-03-01

    Chemical analysis is carried out for dust sample collected from central Sudan and the dust chemical constituents are obtained. The mineral composition of dust are identified by the X-ray diffraction techniques. The mineral quantities are obtained by a technique developed based on the chemical analytical methods. Analyses show that Quartz is the dominant mineral while the SiO{sub 2} is the dominant oxide. A simple model is derived for the dust chemical constituents. This model is used with models for predicting the mixture dielectric constant to estimate the dust dielectric constant; the results of which are seen to be in a good agreement with the measured values. The effects of the different constituents on the dust dielectric constant are studied and results are given.

  3. High dielectric constant, low loss and high photocatalytic activity in Gd doped ZnO systems

    NASA Astrophysics Data System (ADS)

    Divya, N. K.; Pradyumnan, P. P.

    2017-01-01

    Enhanced photocatalytic activity and high dielectric constant values are achieved by gadolinium (Gd) doping in ZnO. The changes that happened to the wurtzite structure of ZnO on doping are depicted in detail by using x-ray diffraction spectroscopy. The chemical composition is confirmed using energy dispersive x-ray spectroscopy (EDAX). The influence of Gd incorporation in the emission spectra of ZnO is analysed from photoluminescence studies. The photocatalytic activity enhancement occurred in ZnO system on Gd doping was explored by kinetic rate analysis. The optimum incorporation of Gd has enhanced the dielectric constant value and decreased the loss of pristine. The high dielectric constant value and low loss make the system suitable for large scale of applications in microelectronics. The work also proposes large scale synthesis of highly efficient fluorescent Gd doped ZnO photocatalysts.

  4. L-band Dielectric Constant Measurements of Seawater (Oral presentation and SMOS Poster)

    NASA Technical Reports Server (NTRS)

    Lang, Roger H.; Utku, Cuneyt; LeVine, David M.

    2003-01-01

    This paper describes a resonant cavity technique for the measurement of the dielectric constant of seawater as a function of its salinity. Accurate relationships between salinity and dielectric constant (which determines emissivity) are needed for sensor systems such as SMOS and Aquarius that will monitor salinity from space in the near future. The purpose of the new measurements is to establish the dependence of the dielectric constant of seawater on salinity in contemporary units (e.g. psu) and to take advantage of modern instrumentation to increase the accuracy of these measurements. The measurement device is a brass cylindrical cavity 16cm in diameter and 7cm in height. The seawater is introduced into the cavity through a slender glass tube having an inner diameter of 0.1 mm. By assuming that this small amount of seawater slightly perturbs the internal fields in the cavity, perturbation theory can be employed. A simple formula results relating the real part of the dielectric constant to the change in resonant frequency of the cavity. In a similar manner, the imaginary part of the dielectric constant is related to the change in the cavity s Q. The expected accuracy of the cavity technique is better than 1% for the real part and 1 to 2% for the imaginary part. Presently, measurements of methanol have been made and agree with precision measurements in the literature to within 1% in both real and imaginary parts. Measurements have been made of the dielectric constant of seawater samples from Ocean Scientific in the United Kingdom with salinities of 10, 30, 35 and 38 psu. All measurements were made at room temperature. Plans to make measurements at a range of temperatures and salinities will be discussed.

  5. Trends of microwave dielectric materials for antenna application

    NASA Astrophysics Data System (ADS)

    Sulong, T. A. T.; Osman, R. A. M.; Idris, M. S.

    2016-07-01

    Rapid development of a modern microwave communication system requires a high quality microwave dielectric ceramic material to be used as mobile and satellite communication. High permittivity of dielectric ceramics leads to fabrication of compact device for electronic components. Dielectric ceramics which used for microwave applications required three important parameters such as high or appropriate permittivity (ɛr), high quality factor (Q f ≥ 5000GH z) and good temperature coefficient of resonant frequency (τf). This paper review of various dielectric ceramic materials used as microwave dielectric materials and related parameters for antenna applications.

  6. Band gaps and dielectric constants of amorphous hafnium silicates: A first-principles investigation

    NASA Astrophysics Data System (ADS)

    Broqvist, Peter; Pasquarello, Alfredo

    2007-02-01

    Electronic band gaps and dielectric constants are obtained for amorphous hafnium silicates using first-principles methods. Models of amorphous (HfO2)x(SiO2)1-x for varying x are generated by ab initio molecular dynamics. The calculations show that the presence of Hf gives rise to low-lying conduction states which explain the experimentally observed nonlinear dependence of the band gap on hafnium content. Static dielectric constants are found to depend linearly on x, supporting recent experimental data.

  7. Performance of dielectric elastomer actuators and materials

    NASA Astrophysics Data System (ADS)

    Sommer-Larsen, Peter; Kofod, Guggi; Shridhar, M. H.; Benslimane, Mohammed; Gravesen, Peter

    2002-07-01

    Dielectric elastomer actuators performance depends on their construction and the way they are driven. We describe the governing equations for the dynamic performance of actuators and show examples of their use. Both the properties of the base elastomer material and the compliant electrodes influence the actuators performance. The mechanical and electrical properties of elastomers are discussed with a focus on an acrylate pressure sensitive adhesive from 3M, which is used by a number of groups. The influence of these properties on the actuator properties is analyzed.

  8. Tunable Dielectric Materials and Devices for Broadband Wireless Communications

    NASA Technical Reports Server (NTRS)

    Mueller, Carl H.; Miranda, Felix A.; Dayton, James A. (Technical Monitor)

    1998-01-01

    Wireless and satellite communications are a rapidly growing industries which are slated for explosive growth into emerging countries as well as countries with advanced economies. The dominant trend in wireless communication systems is towards broadband applications such as multimedia file transfer, video transmission and Internet access. These applications require much higher data transmission rates than those currently used for voice transmission applications. To achieve these higher data rates, substantially larger bandwidths and higher carrier frequencies are required. A key roadblock to implementing these systems at K-band (18-26.5 GHz) and Ka-band (26.5-40 GHz) is the need to develop hardware which meets the requirements for high data rate transmission in a cost effective manner. In this chapter, we report on the status of tunable dielectric thin films for devices, such as resonators, filters, phased array antennas, and tunable oscillators, which utilize nonlinear tuning in the control elements. Paraelectric materials such as Barium Strontium Titanate ((Ba, Sr)TiO3) have dielectric constants which can be tuned by varying the magnitude of the electric field across the material. Therefore, these materials can be used to control the frequency and/or phase response of various devices such as electronically steerable phased array antennas, oscillators, and filters. Currently, tunable dielectric devices are being developed for applications which require high tunability, low loss, and good RF power-handling capabilities at microwave and millimeter-wave frequencies. These properties are strongly impacted by film microstructure and device design, and considerable developmental work is still required. However, in the last several years enormous progress has occurred in this field, validating the potential of tunable dielectric technology for broadband wireless communication applications. In this chapter we summarize how film processing techniques, microwave test

  9. Electromechanical and electro-optical functions of plasticized PVC with colossal dielectric constant

    NASA Astrophysics Data System (ADS)

    Sato, Hiromu; Hirai, Toshihiro

    2013-04-01

    A soft dielectric polymer, plasticized poly(vinyl chloride) (PVC gel), has been known as a characteristic actuator with electrotactic creep deformation. The deformation can be applied for bending and contraction. The mechanism of the deformation has been attributed to the colossal dielectric constant of the gel induced by dc field. The dielectric constant at 1 Hz, jumps from less than10 to thousand times larger value. The huge dielectric constant suggests the gel can have electro-optic function. In this paper, we introduce the gel can bend light direction by applying a dc electric field. The PVC gel can bend light direction depending on the electric field. Detailed feature of the light bending will be introduced and discussed. Bending angle can be controlled by dielectric plasticizer and electric field. The components of the gel, PVC and plasticizer themselves, did not show any effect of electro-optical function like the PVC gel. The same feature can be observed in other polymer, like poly(vinyl alcohol)-dimethyl sulphoxide gel, too.

  10. Giant voltage-induced deformation of a dielectric elastomer under a constant pressure

    NASA Astrophysics Data System (ADS)

    Godaba, Hareesh; Foo, Choon Chiang; Zhang, Zhi Qian; Khoo, Boo Cheong; Zhu, Jian

    2014-09-01

    Dielectric elastomer actuators coupled with liquid have recently been developed as soft pumps, soft lenses, Braille displays, etc. In this paper, we investigate the performance of a dielectric elastomer actuator, which is coupled with water. The experiments demonstrate that the membrane of a dielectric elastomer can achieve a giant voltage-induced area strain of 1165%, when subject to a constant pressure. Both theory and experiment show that the pressure plays an important role in determining the electromechanical behaviour. The experiments also suggest that the dielectric elastomer actuators, when coupled with liquid, may suffer mechanical instability and collapse after a large amount of liquid is enclosed by the membrane. This failure mode needs to be taken into account in designing soft actuators.

  11. Method for preparing dielectric composite materials

    DOEpatents

    Lauf, Robert J.; Anderson, Kimberly K.; Montgomery, Frederick C.; Collins, Jack L.; Felten, John J.

    2004-11-23

    The invention allows the fabrication of small, dense beads of dielectric materials with selected compositions, which are incorporated into a polymeric matrix for use in capacitors, filters, and the like. A porous, generally spherical bead of hydrous metal oxide containing titanium or zirconium is made by a sol-gel process to form a substantially rigid bead having a generally fine crystallite size and correspondingly finely distributed internal porosity. The resulting gel bead may be washed and hydrothermally reacted with a soluble alkaline earth salt (typically Ba or Sr) at elevated temperature and pressure to convert the bead into a mixed hydrous titanium- or zirconium-alkaline earth oxide while retaining the generally spherical shape. Alternatively, the gel bead may be made by coprecipitation. This mixed oxide bead is then washed, dried and calcined to produce the desired (BaTiO.sub.3, PbTiO.sub.3, SrZrO.sub.3) structure. The sintered beads are incorporated into a selected polymer matrix. The resulting dielectric composite material may be electrically "poled" if desired.

  12. Dielectric composite materials and method for preparing

    DOEpatents

    Lauf, Robert J.; Anderson, Kimberly K.; Montgomery, Frederick C.; Collins, Jack L.; Felten, John J.

    2003-07-29

    The invention allows the fabrication of small, dense beads of dielectric materials with selected compositions, which are incorporated into a polymeric matrix for use in capacitors, filters, and the like. A porous, generally spherical bead of hydrous metal oxide containing titanium or zirconium is made by a sol-gel process to form a substantially rigid bead having a generally fine crystallite size and correspondingly finely distributed internal porosity. The resulting gel bead may be washed and hydrothermally reacted with a soluble alkaline earth salt (typically Ba or Sr) at elevated temperature and pressure to convert the bead into a mixed hydrous titanium- or zirconium-alkaline earth oxide while retaining the generally spherical shape. Alternatively, the gel bead may be made by coprecipitation. This mixed oxide bead is then washed, dried and calcined to produce the desired (BaTiO.sub.3, PbTiO.sub.3, SrZrO.sub.3) structure. The sintered beads are incorporated into a selected polymer matrix. The resulting dielectric composite material may be electrically "poled" if desired.

  13. Note: Extraction of hydrogen bond thermodynamic properties of water from dielectric constant and relaxation time data

    NASA Astrophysics Data System (ADS)

    Rastogi, Abhishek; Yadav, Siddharth; Suresh, S. J.

    2011-08-01

    We recently proposed a theory [Suresh, J. Chem. Phys. 113, 9727 (2000)], 10.1063/1.1320822, based on the principles of statistical mechanics, for describing the temperature variation of static dielectric constant of water and the average number of H-bonds per molecule in the liquid phase. The theoretical model contains three parameters; two of them pertain to the energy and entropy changes accompanying bond-formation, and the third (ɛ∞) represents the dielectric constant at a frequency that is sufficiently low for atomic and electronic polarization, but sufficiently high for intermolecular relaxation processes involving the movement of permanent dipole moments to be inoperative. In the absence of a consensus in the literature for the value of ɛ∞ to be used in dielectric constant calculations, it was arbitrarily set to a commonly accepted value of 1.77 (corresponding to refractive index of 1.33). Values for H-bond parameters were then estimated by best fitting model calculations to experimental data for dielectric constant across temperatures ranging from melting to the critical point of water. It is the purpose of the present Note to eliminate the ambiguity on the choice of ɛ∞ and propose refined values for the H-bond parameters.

  14. Dielectric-constant measurements in a system of NbC grains near the percolation threshold

    NASA Astrophysics Data System (ADS)

    McLachlan, D. S.; Oblakova, I. I.; Pakhomov, A. B.

    1994-06-01

    Measurements of the complex dielectric constant (ε‧ + iε″) on a series on NbC-KCl composites in a wide range of concentrations are performed as a function of φ (the volume fraction of the 1-3 μm NbC grains) at frequencies of 10 2, 10 3, 10 4 and 10 5 Hz. Frequency scaling of ε = ε‧ + iε″ at the metal-insulator transition is different from one which follows from the scaling theory of an ideal percolation system. We observe two different values of the critical volume fraction of metal. The first critical concentration, φ c1, is a cross-over point where the dielectric-constant frequency dependence changes and the loss factor is on the order of unity. The temperature behavior of the complex dielectric constant below the superconducting transition temperature Tc reveals a transformation of a system of isolated NbC grains into a system of weakly coupled tunneling junctions at φ c1. The expected divergence of ε‧ is observed as the second critical volume concentration φ c2 > φ c1 is approached. At this concentration a cross-over from the capacitive tunneling junction medium to a truly metallic state occurs. At φ > φ c2, ε‧ decreases rapidly as a function of φ and becomes negative at φ - φ c2∼0.01, due to the negative effective real dielectric constant of the percolation metallic cluster which spans the system.

  15. Characterization of the Dielectric Constant in the Trichoderma reesei Cel7B Active Site.

    PubMed

    Song, Xiangfei; Wang, Yefei; Zhang, Shujun; Yan, Shihai; Li, Tong; Yao, Lishan

    2015-07-27

    An attempt is made to evaluate the dielectric constant of the Trichoderma reesei Cel7B active site. Through kinetic measurements, the pKa value of the catalytic acid E201 is determined. Mutations (away from E201) with net charge changes are introduced to perturb the E201 pKa. It is shown that the mutation with a +1 charge change (including G225R, G230R, and A335R) decreases the pKa of E201, whereas the mutation with a -1 charge change (including Q149E, A222D, G225D, and G230D) increases the pKa. This effect is consistent with the electrostatic interaction between the changed charge and the E201 side chain. The fitting of the experimental data yields an apparent dielectric constant of 25-80. Molecular dynamics simulations with explicit water molecules indicate that the high solvent accessibility of the active site contributes largely to the high dielectric constant. ONIOM calculations show that high dielectric constant benefits the catalysis through decreasing the energy of the transition state relative to that of the enzyme substrate complex.

  16. Examination of Effective Dielectric Constants Derived from Non-Spherical Melting Hydrometeor

    NASA Astrophysics Data System (ADS)

    Liao, L.; Meneghini, R.

    2009-04-01

    The bright band, a layer of enhanced radar echo associated with melting hydrometeors, is often observed in stratiform rain. Understanding the microphysical properties of melting hydrometeors and their scattering and propagation effects is of great importance in accurately estimating parameters of the precipitation from spaceborne radar and radiometers. However, one of the impediments in the study of the radar signature of the melting layer is the determination of effective dielectric constants of melting hydrometeors. Although a number of mixing formulas are available to compute the effective dielectric constants, their results vary to a great extent when water is a component of the mixture, such as in the case of melting snow. It is also physically unclear as to how to select among these various formulas. Furthermore, the question remains as to whether these mixing formulas can be applied to computations of radar polarimetric parameters from non-spherical melting particles. Recently, several approaches using numerical methods have been developed to derive the effective dielectric constants of melting hydrometeors, i.e., mixtures consisting of air, ice and water, based on more realistic melting models of particles, in which the composition of the melting hydrometeor is divided into a number of identical cells. Each of these cells is then assigned in a probabilistic way to be water, ice or air according to the distribution of fractional water contents for a particular particle. While the derived effective dielectric constants have been extensively tested at various wavelengths over a range of particle sizes, these numerical experiments have been restricted to the co-polarized scattering parameters from spherical particles. As polarimetric radar has been increasingly used in the study of microphysical properties of hydrometeors, an extension of the theory to polarimetric variables should provide additional information on melting processes. To account for polarimetric

  17. Process for lowering the dielectric constant of polyimides using diamic acid additives

    NASA Technical Reports Server (NTRS)

    Stoakley, Diane M. (Inventor); St.clair, Anne K. (Inventor)

    1990-01-01

    Linear aromatic polyimides with low dielectric constants are produced by adding a diamic acid additive to the polyamic acid resin formed by the condensation of an aromatic dianhydride with an aromatic diamine. The resulting modified polyimide is a better electrical insulator than state-of-the-art commercially available polyimides.

  18. Accurate Measurements of the Dielectric Constant of Seawater at L Band

    NASA Technical Reports Server (NTRS)

    Lang, Roger; Zhou, Yiwen; Utku, Cuneyt; Le Vine, David

    2016-01-01

    This paper describes measurements of the dielectric constant of seawater at a frequency of 1.413 GHz, the center of the protected band (i.e., passive use only) used in the measurement of sea surface salinity from space. The objective of the measurements is to accurately determine the complex dielectric constant of seawater as a function of salinity and temperature. A resonant cylindrical microwave cavity in transmission mode has been employed to make the measurements. The measurements are made using standard seawater at salinities of 30, 33, 35, and 38 practical salinity units over a range of temperatures from 0 degree C to 35 degree C in 5 degree C intervals. Repeated measurements have been made at each temperature and salinity. Mean values and standard deviations are then computed. The total error budget indicates that the real and imaginary parts of the dielectric constant have a combined standard uncertainty of about 0.3 over the range of salinities and temperatures considered. The measurements are compared with the dielectric constants obtained from the model functions of Klein and Swift and those of Meissner and Wentz. The biggest differences occur at low and high temperatures.

  19. THE ONSET OF ELECTRICAL BREAKDOWN IN DUST LAYERS: II. EFFECTIVE DIELECTRIC CONSTANT AND LOCAL FIELD ENHANCEMENT

    EPA Science Inventory

    Part 1 of the work has shown that electrical breakdown in dust layers obeys Paschen's Law, but occurs at applied field values which appear too small to initiate the breakdown. In this paper the authors show how an effective dielectric constant characterizing the dust layer can be...

  20. Angular sensitivity for a Fabry-Perot structure incorporating different dielectric materials

    NASA Astrophysics Data System (ADS)

    Wu, Shangliang; Ye, Yan; Zhou, Yun; Huang, Wenbin; Liu, Yanhua; Qiao, Wen; Wang, Yanyan; Luo, Minghui; Chen, Linsen

    2016-11-01

    Color filters based on different Fabry-Perot structures are investigated extensively, and incident angle dependency is an important characteristic in practical applications. Here, we investigated a color filter incorporating a Fabry-Perot structure, discussing its reflective angular sensitivity related to refractive index of its dielectric material. By finite difference time domain(FDTD) theory, the refractive index of the dielectric material is found to influence the angular sensitivity greatly while the optical thickness keeps constant. The simulated results shows that the higher the dielectric layer's refractive index is, the more angular insensitive of the reflection will be obtained and a good angular insensitive will achieved when the refractive index is larger than 2.1. Finally, samples with different dielectric layer are fabricated in experiment and the measured results verify influence of the refractive index of dielectric layer on the spectra angular sensitivity, which is helpful for the application of color filter in color display, image sensors and decoration.

  1. Nanocomposites of TiO₂/cyanoethylated cellulose with ultra high dielectric constants.

    PubMed

    Madusanka, Nadeesh; Shivareddy, Sai G; Hiralal, Pritesh; Eddleston, Mark D; Choi, Youngjin; Oliver, Rachel A; Amaratunga, Gehan A J

    2016-05-13

    A novel dielectric nanocomposite containing a high permittivity polymer, cyanoethylated cellulose (CRS) and TiO2 nanoparticles was successfully prepared with different weight percentages (10%, 20% and 30%) of TiO2. The intermolecular interactions and morphology within the polymer nanocomposites were analysed. TiO2/CRS nanofilms on SiO2/Si wafers were used to form metal-insulator-metal type capacitors. Capacitances and loss factors in the frequency range of 1 kHz-1 MHz were measured. At 1 kHz CRS-TiO2 nanocomposites exhibited ultra high dielectric constants of 118, 176 and 207 for nanocomposites with 10%, 20% and 30% weight of TiO2 respectively, significantly higher than reported values of pure CRS (21), TiO2 (41) and other dielectric polymer-TiO2 nanocomposite films. Furthermore, all three CRS-TiO2 nanocomposites show a loss factor <0.3 at 1 kHz and low leakage current densities (10(-6)-10(-7) A cm(-2)). Leakage was studied using conductive atomic force microscopy and it was observed that the leakage is associated with TiO2 nanoparticles embedded in the CRS polymer matrix. A new class of ultra high dielectric constant hybrids using nanoscale inorganic dielectrics dispersed in a high permittivity polymer suitable for energy management applications is reported.

  2. Nanocomposites of TiO2/cyanoethylated cellulose with ultra high dielectric constants

    NASA Astrophysics Data System (ADS)

    Madusanka, Nadeesh; Shivareddy, Sai G.; Hiralal, Pritesh; Eddleston, Mark D.; Choi, Youngjin; Oliver, Rachel A.; Amaratunga, Gehan A. J.

    2016-05-01

    A novel dielectric nanocomposite containing a high permittivity polymer, cyanoethylated cellulose (CRS) and TiO2 nanoparticles was successfully prepared with different weight percentages (10%, 20% and 30%) of TiO2. The intermolecular interactions and morphology within the polymer nanocomposites were analysed. TiO2/CRS nanofilms on SiO2/Si wafers were used to form metal-insulator-metal type capacitors. Capacitances and loss factors in the frequency range of 1 kHz-1 MHz were measured. At 1 kHz CRS-TiO2 nanocomposites exhibited ultra high dielectric constants of 118, 176 and 207 for nanocomposites with 10%, 20% and 30% weight of TiO2 respectively, significantly higher than reported values of pure CRS (21), TiO2 (41) and other dielectric polymer-TiO2 nanocomposite films. Furthermore, all three CRS-TiO2 nanocomposites show a loss factor <0.3 at 1 kHz and low leakage current densities (10-6-10-7 A cm-2). Leakage was studied using conductive atomic force microscopy and it was observed that the leakage is associated with TiO2 nanoparticles embedded in the CRS polymer matrix. A new class of ultra high dielectric constant hybrids using nanoscale inorganic dielectrics dispersed in a high permittivity polymer suitable for energy management applications is reported.

  3. Quasi-optical measurement of complex dielectric constant at 300 GHz

    NASA Astrophysics Data System (ADS)

    Stöckel, Bernd

    1993-10-01

    A two beam interferometer in the Martin-Puplett configuration is used to determine the complex dielectric constant at 300 GHz of teflon, TPX-plastics, SPECTRALON and paraffin waxes with melting temperatures of 48° C and 72° C, respectively. The design of the quasi-optical system leads to a constant beam diameter at the power detector independent of path delay and frequency. The power detector signal is recorded not only along one period but over about 50 periods. A spectrum estimation routine allows to determine more exactly amplitude and phase angle of the signal. A basic problem is noticed: imperfect detector and source match cause harmonic distortion of the power detector signal. The effects on processing the loss tangent and the invalidation are shown. Finally loss tangent and dielectric constant are determined indirectly by optimizing an equivalent microwave circuit using a commercial available microwave design system to take multiple reflections and losses in consideration.

  4. Dielectric constant and loss tangent of Eccofoam PT, at 2.3 GHz, for various packing densities

    NASA Technical Reports Server (NTRS)

    Lane, F. L.

    1973-01-01

    The dielectric constant and loss tangent for Eccofoam PT, at various densities, are determined; the resulting density gradients are provided. The range of densites over which the dielectric constant and loss tangent are determined are from approximately 320 to 1280 kg/cu m (20 to 80 lb/cu ft).

  5. Communication: Temperature derivative of the dielectric constant gives access to multipoint correlations in polar liquids

    NASA Astrophysics Data System (ADS)

    Matyushov, Dmitry V.; Richert, Ranko

    2016-01-01

    Fluctuations of the dipole moment of a macroscopic dielectric sample are induced by thermal motions. The variance of the sample dipole moment, characterizing the extent of thermal fluctuations, is a decaying function of temperature for many polar liquids. This result is inconsistent with the Nyquist (fluctuation-dissipation) theorem predicting the variance of a macroscopic property to grow linearly with temperature. The reason for a qualitatively different behavior is in strong multi-particle correlations of dipolar orientations. An equation connecting the temperature slope of the dielectric constant to a static three-point correlation function is derived. When applied to experimental data for polar and hydrogen-bonding liquids at normal conditions, the three-point correlations of different liquids fall on a single master curve as a function of the dielectric constant. Static three-point correlation functions can potentially reflect the growing spatial correlation length on approach to the glass transition. However, the measured temperature slope of the dielectric constant of glycerol does not indicate a change in such a lengthscale.

  6. Role of polymer matrix in large enhancement of dielectric constant in polymer-metal composites

    NASA Astrophysics Data System (ADS)

    Panda, Maheswar; Srinivas, V.; Thakur, A. K.

    2011-07-01

    Dielectric behavior of polymer (polar/nonpolar)-metal nanocomposites (PMCs) prepared under identical processing conditions have been compared. A high effective dielectric constant (ɛeff>2500) with a moderate loss and a lower ɛeff (74) with low loss was observed, respectively, for polar and nonpolar PMC at their respective percolation thresholds (fc). The results have been explained with the help of percolation theory and dipolar polarization. Similar value of fc observed in both the PMC is attributed to the same order of conductivity of polymer matrices. The dipolar polarization present in the polymer plays a major role in the enhancement of ɛeff.

  7. Low-dielectric-constant fluorinated diamond-like carbon thin films by plasma-enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Yi, Jeong Woo

    Fluorinated amorphous carbon (a-C:F) thin films are developed for a low dielectric constant interlayer dielectric material from hexafluorobenze (C 6F6) or 1,1,1,2-tetrafluoroethane (FCH2CF 4) as the source gas and argon as the diluent gas in an asymmetric capacitively coupled rf (radio frequency) plasma reactor and an inductively coupled plasma reactor. Effects of input rf power, fluorination, applied bias voltage and post annealing on the properties of a-C:F films are investigated. For depositing a-C:F films from highly diluted C6F6 (3%) and argon (97%) in the capacitively rf plasma reactor at 150 mTorr, the dielectric constant of the film increases from 2.0 to 2.8 as the rf power is increased from 10 W to 70 W, while the optical energy gap decreases from 2.6 eV to 1.9 eV and the transparency in a ultra-violet range is degraded. At input power of 100 W, the deposited film exhibits high residual stress of 40 MPa and easily peeled off by a Scotch tape test. This is due to high self-bias voltage (-230 V) developed at the substrate holder during deposition. When depositing amorphous carbon films from tetrafluoroethane (TFE) and methane in the capacitively coupled plasma reactor, the incorporation of fluorine in the film is increased with increasing TFE fraction in the feed gas mixture. The dielectric constant of the a-C:F film deposited from pure TFE is as low as 2.3, but the film exhibits poor thermal stability while a-C:H (diamond-like carbon) film deposited from pure methane has a dielectric constant of 3.8 and shows good thermal stability up to 400°C. As the TFE content in the feed is increased, the dielectric constant and the refractive index decrease while the transparency of the film is enhanced significantly. When depositing a-C:F films from C6F6 (4 sccm) and Ar (5 sccm) in the inductively coupled rf plasma reactor, the bias voltage (from a separate 100 KHz source) applied to the substrate holder affects the film properties significantly. As the negative bias

  8. Negative Refraction in a Uniaxial Absorbent Dielectric Material

    ERIC Educational Resources Information Center

    Jen, Yi-Jun; Lakhtakia, Akhlesh; Yu, Ching-Wei; Lin, Chin-Te

    2009-01-01

    Refraction of light from an isotropic dielectric medium to an anisotropic dielectric material is a complicated phenomenon that can have several different characteristics not usually discussed in electromagnetics textbooks for undergraduate students. With a simple problem wherein the refracting material is uniaxial with its optic axis normal to the…

  9. Dielectric properties of agricultural materials and their application

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This book is prepared as a comprehensive source of information on dielectric properties of agricultural materials for scientific researchers and engineers involved in practical application of radio-frequency and microwave energy for potential problem solutions. Dielectric properties of materials det...

  10. Dielectric constants of chrysoberyl, spinel, phenacite, and forsterite and the oxide additivity rule

    NASA Astrophysics Data System (ADS)

    Shannon, R. D.; Subramanian, M. A.

    1989-11-01

    The dielectric constants and dielectric loss values of BeAl2O4 (chrysoberyl), MgAl2O4 (spinel), Be2SiO4 (phenacite), and Mg2SiO4 (forsterite) were measured at 1 MHz using a two-terminal method and empirically determined edge corrections. The results are: chrysoberyl, κ' a =9.436, κ' b =9.071, κ' c =8.269; spinel, κ' a =8.18; phenacite, κ' a =6.28, κ' c =6.06; and forsterite, κ' a =6.867, κ' b =7.392, κ' c =6.739. The agreement between measured dielectric polarizabilities as determined from the Clausius-Mosotti equation and those calculated from the sum of oxide polarizabilities according to αD(M2M'X4) = 2αD(MX)+αD(M'X2) is ~ 1.0%.

  11. Empirical Estimation of Local Dielectric Constants: Toward Atomistic Design of Collagen Mimetic Peptides

    PubMed Central

    Pike, Douglas H.; Nanda, Vikas

    2017-01-01

    One of the key challenges in modeling protein energetics is the treatment of solvent interactions. This is particularly important in the case of peptides, where much of the molecule is highly exposed to solvent due to its small size. In this study, we develop an empirical method for estimating the local dielectric constant based on an additive model of atomic polarizabilities. Calculated values match reported apparent dielectric constants for a series of Staphylococcus aureus nuclease mutants. Calculated constants are used to determine screening effects on Coulombic interactions and to determine solvation contributions based on a modified Generalized Born model. These terms are incorporated into the protein modeling platform protCAD, and benchmarked on a data set of collagen mimetic peptides for which experimentally determined stabilities are available. Computing local dielectric constants using atomistic protein models and the assumption of additive atomic polarizabilities is a rapid and potentially useful method for improving electrostatics and solvation calculations that can be applied in the computational design of peptides. PMID:25784456

  12. Utilizing Calibrated GPS Reflected Signals to Estimate Soil Reflectivity and Dielectric Constant: Results from SMEX02

    NASA Technical Reports Server (NTRS)

    Katzberg, Stephen J.; Torres, Omar; Grant, Michael S.; Masters, Dallas

    2006-01-01

    Extensive reflected GPS data was collected using a GPS reflectometer installed on an HC130 aircraft during the Soil Moisture Experiment 2002 (SMEX02) near Ames, Iowa. At the same time, widespread surface truth data was acquired in the form of point soil moisture profiles, areal sampling of near-surface soil moisture, total green biomass and precipitation history, among others. Previously, there have been no reported efforts to calibrate reflected GPS data sets acquired over land. This paper reports the results of two approaches to calibration of the data that yield consistent results. It is shown that estimating the strength of the reflected signals by either (1) assuming an approximately specular surface reflection or (2) inferring the surface slope probability density and associated normalization constants give essentially the same results for the conditions encountered in SMEX02. The corrected data is converted to surface reflectivity and then to dielectric constant as a test of the calibration approaches. Utilizing the extensive in-situ soil moisture related data this paper also presents the results of comparing the GPS-inferred relative dielectric constant with the Wang-Schmugge model frequently used to relate volume moisture content to dielectric constant. It is shown that the calibrated GPS reflectivity estimates follow the expected dependence of permittivity with volume moisture, but with the following qualification: The soil moisture value governing the reflectivity appears to come from only the top 1-2 centimeters of soil, a result consistent with results found for other microwave techniques operating at L-band. Nevertheless, the experimentally derived dielectric constant is generally lower than predicted. Possible explanations are presented to explain this result.

  13. High-k Dielectric Nanosheets for Two-Dimensional material Electronics

    NASA Astrophysics Data System (ADS)

    Hao, Yufeng; Cui, Xu; Yin, Jun; Lee, Gwan-Hyoung; Arefe, Ghidewon; Osada, Minoru; Sasaki, Takayoshi; Hone, James

    2015-03-01

    Two-dimensional (2D) materials, such as graphene, hexagonal boron nitride (hBN), transition metal dichalcogenides, have shown great potential in nano-electronics because of their unique and superior physical properties. Among them, hBN has been known as an alternative dielectric that is atomically flat and free of trapped charges, which drastically enhance the mobility of graphene or MoS2. However, low dielectric constant (k ~ 3.5) of hBN limits its use in transistors as gate lengths are scaled down to tens of nanometers. Here we demonstrate high performance graphene and MoS2 field effect transistors by using ultrathin Ca2NaNb4O13 nanosheet as a dielectric and mechanically stacking 2D materials. We developed a facile transfer strategy to build 2D materials devices based on the Ca2NaNb4O13 nanosheets. We measured and found that the oxide nanosheet has high dielectric strength, along with high dielectric constant at thickness of a few tens of nanometer. Therefore, multiple-stacked heterostructure of 2D materials shows high mobility at small operating voltage. This study shows possibility of high-k dielectric nanosheets for 2D electronics.

  14. Dielectric response based characterization and strength prediction of cementitious materials

    NASA Astrophysics Data System (ADS)

    Manchiryal, Ram Kishore

    Electrical property based methods are powerful tools to sense the properties of cement based materials. Among the several non-invasive investigative techniques, those based on monitoring the electrical properties during the initial setting and in the subsequent hardening period have immense potential in performance prediction of concrete. Electrical impedance spectroscopy (EIS) has emerged as one of the promising techniques to non-invasively probe the microstructure and property development in cement based materials. This thesis reports the results of a systematic investigation carried out to understand the influence of material parameters on the dielectric response of cement pastes and concretes, and also a methodology to property prediction in cementitious system using electrical properties. The influence of cement type, water-to-cementing materials ratio (w/cm), and the presence of fly ash as a cement replacement material on the conductivity of cement pastes is studied. The electrical conductivity---time relationships of cement pastes and concretes are expressed using a model that facilitates the extraction of initial and final conductivities, and a characteristic time parameter. These terms are used to derive information about the microstructural changes occurring with time in cement pastes. The experimental results are subjected to a range analysis to isolate the significant factors and factor interactions that influence the initial and final conductivities as well as the time parameter from the conductivity-time model for concrete mixtures. The material parameters that influence the measured conductivity are identified and their influence quantified. The changes in dielectric constant and conductivity spectra of cement paste and concretes are attributed to the polarization phenomena. There is an observed dielectric enhancement for fly ash modified pastes. The dielectric response of concrete is very similar to that of pastes, and the effect of dilution by the

  15. Improved ground-state electronic structure and optical dielectric constants with a semilocal exchange functional

    NASA Astrophysics Data System (ADS)

    Vlček, Vojtěch; Steinle-Neumann, Gerd; Leppert, Linn; Armiento, Rickard; Kümmel, Stephan

    2015-01-01

    A recently published generalized gradient approximation functional within density functional theory (DFT) has shown, in a few paradigm tests, an improved KS orbital description over standard (semi)local approximations. The characteristic feature of this functional is an enhancement factor that diverges like s ln(s ) for large reduced density gradients s which leads to unusual properties. We explore the improved orbital description of this functional more thoroughly by computing the electronic band structure, band gaps, and the optical dielectric constants in semiconductors, Mott insulators, and ionic crystals. Compared to standard semilocal functionals, we observe improvement in both the band gaps and the optical dielectric constants. In particular, the results are similar to those obtained with orbital functionals or by perturbation theory methods in that it opens band gaps in systems described as metallic by standard (semi)local density functionals, e.g., Ge, α -Sn, and CdO.

  16. Determination of a dielectric waveguide propagation constant using a multifilament-current model.

    PubMed

    Cory, H; Altman, Z; Leviatan, Y

    1989-09-15

    A moment method using a multifilament-current model is presented to analyze the modes propagating in a cylindrical dielectric waveguide. In this model, analytically derivable fields of filamentary electric and magnetic currents (of yet unknown propagation constant and amplitude) are used to simulate the field of each mode inside and outside the guiding core. A simple point-matching procedure is subsequently used to enforce the boundary conditions at the core periphery and results in a homogeneous matrix equation. The longitudinal propagation constant of each mode and the currents that yield the field distribution of this mode are then found by solving this equation. As an example, a circular dielectric waveguide is analyzed and the results are presented.

  17. Time and voltage dependences of nanoscale dielectric constant modulation on indium tin oxide films

    NASA Astrophysics Data System (ADS)

    Li, Liang; Hao, Haoyue; Zhao, Hua

    2017-01-01

    The modulation of indium tin oxide (ITO) films through surface charge accumulation plays an important role in many different applications. In order to elaborately study the modulation, we measured the dielectric constant of the modulated layer through examining the excitation of surface plasmon polaritons. Charges were pumped on the surfaces of ITO films through applying high voltage in appropriate directions. Experiments unveiled that the dielectric constant of the modulated layer had large variation along with the nanoscale charge accumulation. Corresponding numerical results were worked out through combining Drude model and Mayadas-Shatzkes model. Based on the above results, we deduced the time and voltage dependences of accumulated charge density, which revealed a long-time charge accumulation process.

  18. Dielectric-Constant Gas Thermometry and the Relation to the Virial Coefficients

    NASA Astrophysics Data System (ADS)

    Gaiser, C.; Fellmuth, B.; Zandt, T.

    2014-04-01

    At PTB new dielectric-constant gas thermometry (DCGT) measurements were performed at the temperature of the triple point of water. As discussed recently in an accompanying paper, the main goal was the determination of the Boltzmann constant as a contribution to the international efforts directed to a new definition of the base unit kelvin via fixing the value of . Besides the linear term in the series expansion used for fitting the results of measurements of DCGT isotherms that reveals , in this paper the higher-order terms are analyzed. For retrieving highly accurate virial coefficients of helium from the data obtained at gas pressures up to 7 MPa, an extended DCGT working equation is developed. Applying this equation, information is deduced on the viral coefficients up to the fourth density virial coefficient. Finally, comparisons with the latest ab initio calculations for the second and third density virial coefficients as well as the second dielectric virial coefficient are performed.

  19. Advanced Artificial Dielectric Materials for Millimeter Wavelength Applications. Part A

    DTIC Science & Technology

    1989-11-30

    permeability and permilttivity) of artificial dielectrics with metal particles (I Auto 37 j)randomly loaded into both polymeric and inorganic binders. The alloy...Part B, which contains classified material, treats magneto- i dielectric composites. A model dielectric consisting of a randomly packed, metal ... metal particles (.-I ý= to .-37 jm) randomly loaded into both polymeric and inorganic glassy binders up Sto 40 vol%. The metal alloy powder, N192Cr8, is

  20. One-dimensional photonic crystals with an amplitude-modulated dielectric constant in the unit cell.

    PubMed

    Carretero, Luis; Ulibarrena, Manuel; Blaya, Salvador; Fimia, Antonio

    2004-05-10

    Photonic band structures of one-dimensional photonic crystals with an amplitude-modulated dielectric constant in the unit cell were studied. With this structure two bandgaps in the visible and one in the IR region were predicted. Experimental measurements of the two photonic bandgaps in the visible spectrum were made in a photonic crystal recorded in a holographic emulsion. Good agreement between experimental and theoretical results was obtained.

  1. Determination of the dielectric constant of GaN in the kHz frequency range

    NASA Astrophysics Data System (ADS)

    Kane, M. J.; Uren, M. J.; Wallis, D. J.; Wright, P. J.; Soley, D. E. J.; Simons, A. J.; Martin, T.

    2011-08-01

    Capacitance techniques are used to show that the dielectric constant ɛ|| of GaN in the kHz frequency range is 10.6 ± 0.3. The data allow depth information to be accurately extracted using methods such as mercury probe capacitance profiling. The measurements complement the pre-existing data which are derived from infrared reflectivity and which give a value of 10.4 ± 0.3.

  2. Measurement of the Dielectric Constant of Seawater at L-Band: Techniques and Measurements

    NASA Technical Reports Server (NTRS)

    Lang, R.; Utku, C.; Tarkocin, Y.; LeVine, D.

    2009-01-01

    Satellite instruments, that will monitor salinity from space in the near future, require an accurate relationship between salinity/temperature and seawater dielectric constant. This paper will review measurements that were made of the dielectric constant of seawater during the past several years. The objective of the measurements is to determine the dependence of the dielectric constant of seawater on salinity and on temperature, more accurately than in the past. by taking advantage of modem instrumentation. The measurements of seawater permittivity have been performed as a function of salinity and temperature using a transmission resonant cavity technique. The measurements have been made in the salinity range of 10 to 38 psu and in the temperature range of IOU C to 35 C. These results will be useful in algorithm development for sensor systems such as SMOS and Aquarius. The measurement system consists of a brass microwave cavity that is resonant at 1.413 GHz. The seawater is introduced into the cavity through a capillary glass tube having an inner diameter of 0.1 mm. The diameter of the tube has been made very small so that the amount of seawater introduced in the cavity is small - thus maintaining the sensitivity of the measurements and allowing the use of perturbation theory predicting the seawater permittivity. The change in resonant frequency and the change in cavity Q can be used to determine the real and imaginary pare of the dielectric constant of seawater introduced into the slender tube. The microwave measurements are made by an HPS722D network analyzer. The cavity has been immersed in a uateriethylene-glycol bath which is connected to a Lauda circulator. The circulator keeps the brass cavity at a temperature constant to within 0.01 degrees. The system is automated using a Visual Basic program to control the analyzer and to collect the data. The results of the dielectric constant measurements of seawater will be presented. The measurement results will be

  3. Models for ionic contribution to the complex dielectric constant of nematic liquid crystals.

    PubMed

    Alexe-Ionescu, A L; Barbero, G; Lelidis, I

    2009-12-01

    We analyze the models that account the ionic contribution to the complex dielectric constant of a nematic liquid crystal. We compare the predictions of the model of [Sawada, Mol. Cryst. Liq. Cryst. Sci. Technol., Sect. A 318, 225 (1998)] based on the assumption that the electric field in the liquid coincides with the applied one, with the model of Macdonald where the electric field in the sample is determined in self-consistent manner by solving the equation of Poisson. We show that the model of Sawada , widely used to determine the bulk density of ions and their diffusion coefficient in liquid crystal cells, predicts a thickness dependence of the real and imaginary parts of the dielectric constant different from that predicted by the model of Macdonald. On the contrary, the predictions of the two models coincide for what concerns the frequency dependencies of the two components of the dielectric constant. By considering a typical case, we show that the numerical values of the ionic properties derived by means of the model of Sawada may differ even more than 1 order of magnitude by those predicted by the model of Macdonald. A rescaling procedure allowing to evaluate the bulk density of ions and the ionic diffusion coefficient determined by means of the model of Sawada in agreement with the one of Macdonald is proposed.

  4. Improved SPC force field of water based on the dielectric constant: SPC/ ε

    NASA Astrophysics Data System (ADS)

    Fuentes-Azcatl, Raúl; Mendoza, Noé; Alejandre, José

    2015-02-01

    In a recent work, Fuentes and Alejandre (2014) found that for TIP4P models there is a dipole moment of minimum density at 240 K and that the Lennard-Jones parameters can be adjusted to match the experimental dielectric constant at 300 K and the temperature of maximum density, respectively. The same procedure is used in this work to re-parameterize the simple point charge (SPC) model keeping the original geometry. The new model fails to reproduce the experimental self-diffusion coefficient and shear viscosity but improves the results at different temperatures and pressures of dielectric constant, isothermal compressibility, thermal expansion coefficient, surface tension, coexisting densities at the liquid-vapor interface, equation of state of ice Ih and equation of state of liquids at high pressures. A second model that reproduces the dielectric constant, self-diffusion coefficient and shear viscosity is proposed but the temperature of maximum density is 250 K, compared with the experimental value of 277 K. Both models improve the SPC/E results for almost all properties. The TIP3P model was also analyzed but the liquid density at 240 K always increases and a minimum in the dipole moment was not found. It is not possible to adjust for that model the charge distribution and short range interaction parameters to reproduce at the same time the target properties.

  5. Accurate Measurements of the Dielectric Constant of Seawater at L Band

    NASA Technical Reports Server (NTRS)

    Lang, Roger H.; Utku, Cuneyt; Tarkocin, Yalcin; LeVine, David M.

    2010-01-01

    This report describes measurements of the dielectric constant of seawater at a frequency of 1.413 GHz that is at the center of the L-Sand radiometric protected frequency spectrum. Aquarius will be sensing the sea surface salinity from space in this band. The objective of the project is to refine the model function for the dielectric constant as a function of salinity and temperature so that remote sensing measurements can be made with the accuracy needed to meet the measurement goals (0.2 psu) of the Aquarius mission. The measurements were made, using a microwave cavity operated in the transmission configuration. The cavity's temperature was accurately regulated to 0.02 C by immersing it in a temperature controlled bath of distilled water and ethanol glycol. Seawater had been purchased from Ocean Scientific International Limited (OS1L) at salinities of 30, 35 and 38 psu. Measurements of these seawater samples were then made over a range of temperatures, from l0 C to 35 C in 5 C intervals. Repeated measurements were made at each temperature and salinity, Mean values and standard deviations were then computed. Total error budgets indicated that the real and imaginary parts of the dielectric constant had a relative accuracy of about l%.

  6. A new force field of formamide and the effect of the dielectric constant on miscibility.

    PubMed

    de la Luz, Alexander Pérez; Méndez-Maldonado, G Arlette; Núñez-Rojas, Edgar; Bresme, Fernando; Alejandre, José

    2015-06-09

    Current force fields underestimate significantly the dielectric constant of formamide at standard conditions. We present a derivation of an accurate potential for formamide, with a functional form based on the OPLS/AA force field. Our procedure follows the approach introduced by Salas et al. ( J. Chem. Theory Comput. 2015 , 11 , 683 - 693 ) that relies on ab initio calculations and molecular dynamics simulations. We consider several strategies to derive the atomic charges of formamide. We find that the inclusion of polarization effects in the quantum mechanical computations is essential to obtain reliable force fields. By varying the atomic charges and the Lennard-Jones parameters describing the dispersion interactions in the OPLS/AA force field, we derive an optimum set of parameters that provides accurate results for the dielectric constant, surface tension, and bulk density of liquid formamide in a wide range of thermodynamic states. We test the transferability of our parameters to investigate liquid/liquid mixtures. We have chosen as case study an equimolar mixture of formamide and hexan-2-one. This mixture involves two fluids with very different polar characteristics, namely, large differences in their dielectric constants and their performance as solvents. The new potential predicts a liquid/liquid phase separation, in good agreement with experimental data, and highlights the importance of the correct parametrization of the pure liquid phases to investigate liquid mixtures. Finally, we examine the microscopic origin of the observed inmiscibility between formamide and hexa-2-one.

  7. Dielectric breakdown of additively manufactured polymeric materials

    SciTech Connect

    Monzel, W. Jacob; Hoff, Brad W.; Maestas, Sabrina S.; French, David M.; Hayden, Steven C.

    2016-01-11

    Dielectric strength testing of selected Polyjet-printed polymer plastics was performed in accordance with ASTM D149. This dielectric strength data is compared to manufacturer-provided dielectric strength data for selected plastics printed using the stereolithography (SLA), fused deposition modeling (FDM), and selective laser sintering (SLS) methods. Tested Polyjet samples demonstrated dielectric strengths as high as 47.5 kV/mm for a 0.5 mm thick sample and 32.1 kV/mm for a 1.0 mm sample. As a result, the dielectric strength of the additively manufactured plastics evaluated as part of this study was lower than the majority of non-printed plastics by at least 15% (with the exception of polycarbonate).

  8. Dielectric breakdown of additively manufactured polymeric materials

    DOE PAGES

    Monzel, W. Jacob; Hoff, Brad W.; Maestas, Sabrina S.; ...

    2016-01-11

    Dielectric strength testing of selected Polyjet-printed polymer plastics was performed in accordance with ASTM D149. This dielectric strength data is compared to manufacturer-provided dielectric strength data for selected plastics printed using the stereolithography (SLA), fused deposition modeling (FDM), and selective laser sintering (SLS) methods. Tested Polyjet samples demonstrated dielectric strengths as high as 47.5 kV/mm for a 0.5 mm thick sample and 32.1 kV/mm for a 1.0 mm sample. As a result, the dielectric strength of the additively manufactured plastics evaluated as part of this study was lower than the majority of non-printed plastics by at least 15% (with themore » exception of polycarbonate).« less

  9. Electrodynamic acceleration of dielectric bodies in a rail gun in the constant current regime

    NASA Astrophysics Data System (ADS)

    Drobyshevskii, E. M.; Zhukov, B. G.; Nazarov, E. V.; Rozov, S. I.; Sokolov, V. M.; Kurakin, R. O.; Savel'Ev, M. A.; Iuferov, S. V.

    1991-04-01

    Rail gun experiments are reported in which dielectric bodies were accelerated magnetohydrodynamically by a plasma piston to velocities at which the kinetic energy per each atom became comparable with or greater than the chemical bond energy. In the constant current approximation, a simple expression is obtained which unambiguously relates the acceleration path length to the amount of electricity passing through the system, irrespective of the acceleration rate and final velocity of the body. Practically constant accelerations of about 3 x 10 exp 6 g were achieved for polycarbonate projectiles with a linear current density close to the limit of explosive electrode evaporation (about 60 kA/mm)

  10. Sulfone-Containing Dipolar Glass Polymers with High Dielectric Constant and Low Loss Property

    NASA Astrophysics Data System (ADS)

    Zhu, Yufeng; Zhang, Zhongbo; Litt, Morton; Zhu, Lei

    Sulfone-containing polyoxetanes are designed and synthesized for high dielectric constant and low loss dipolar glasses. The precursor polymer, poly(3,3-bis(chloromethyl)oxetane) (PBCMO) is synthesized by bulk cationic polymerization with boron trifluoride diethyl etherate as initiator. The number-average molecular weight of PBCMO is 73 kDa, with a polydispersity of 1.53 as obtained from size-exclusion chromatography results. Post-modification of PBCMO yields the dipolar glass polymer, poly(3,3-bis(methylsulfonylmethyl)oxetane) (MST). Nuclear magnetic resonance result shows 100% conversion. Differential scanning calorimetry result indicates that MST has a glass transition temperature of ca. 120 °C. Due to the large dipole moment (4.25 D) and small size of the side-chain sulfone groups, MST exhibits a high dielectric constant of 8.7 and a low dissipation factor of 0.01 at 25 °C and 1 Hz. This study suggests that dipolar glass polymers with large dipole moments and small-sized dipoles in the side chains are promising candidates for high energy density and low loss dielectric applications. This work is supported by NSF Polymers Program (DMR-1402733).

  11. Investigation of Biodiesel Through Photopyroelectric and Dielectric-Constant Measurements as a Function of Temperature: Freezing/Melting Interval

    NASA Astrophysics Data System (ADS)

    Zanelato, E. B.; Machado, F. A. L.; Rangel, A. B.; Guimarães, A. O.; Vargas, H.; da Silva, E. C.; Mansanares, A. M.

    2015-06-01

    Biodiesel is a promising option for alternative fuels since it derives from natural and renewable materials; it is biodegradable and less polluting than fossil fuels. A gradual replacement of diesel by biodiesel has been adopted by many countries, making necessary the investigation of the physical properties of biodiesel and of its mixture in diesel. Photothermal techniques, specifically the photopyroelectric technique (PPE), have proved to be suitable in the characterization of biodiesel and of its precursor oils, as well as of the biodiesel/diesel mixtures. In this paper, we investigate thermal and electrical properties of animal fat-based biodiesel as a function of temperature, aiming to characterize the freezing/melting interval and the changes in the physical properties from the solid to the liquid phase. The samples were prepared using the transesterification method, by the ethylic route. Optical transmittance experiments were carried out in order to confirm the phase transition interval. Solid and liquid phases present distinct thermal diffusivities and conductivities, as well as dielectric constants. The PPE signal amplitude is governed by the changes in the thermal diffusivity/conductivity. As a consequence, the amplitude of the signal becomes like a step function, which is smoothed and sometimes delayed by the nucleation processes during cooling. A similar behavior is found in the dielectric constant data, which is higher in the liquid phase since the molecules have a higher degree of freedom. Both methods (PPE/dielectric constant) proved to be useful in the characterization of the freezing/melting interval, as well as to establish the distinction in the physical properties of solid and liquid phases. The methodology allowed a discussion of the cloud point and the pour point of the samples in the temperature variation interval.

  12. Performance of superconducting microwave devices passivated with dielectric materials

    SciTech Connect

    Henderson, M.L.; Kohl, P.A.; Eddy, M.M.; Zuck, B.F.

    1997-09-01

    We present a set of experiments which show that three dielectric processing variables in particular affect the performance of superconducting microwave devices: processing time and temperature, moisture content of the dielectric material, and surface interactions with the high temperature superconductor (HTS). The changes in microwave performance of a straight-line microstrip resonator before and after passivation were quantified by measurements of the loaded and unloaded quality factors for each resonator. Dielectric materials of varying moisture content were used. The dielectrics were processed at different times and temperatures. This study shows that the degradation of the microwave devices can be minimized by choosing dielectrics which (i) have a low moisture content, (ii) interact as little as possible with the HTS surface, and (iii) can be rapidly processed at relatively low temperatures. {copyright} {ital 1997 American Institute of Physics.}

  13. Evaluation of Dielectric-Barrier-Discharge Actuator Substrate Materials

    NASA Technical Reports Server (NTRS)

    Wilkinson, Stephen P.; Siochi, Emilie J.; Sauti, Godfrey; Xu, Tian-Bing; Meador, Mary Ann; Guo, Haiquan

    2014-01-01

    A key, enabling element of a dielectric barrier discharge (DBD) actuator is the dielectric substrate material. While various investigators have studied the performance of different homogeneous materials, most often in the context of related DBD experiments, fundamental studies focused solely on the dielectric materials have received less attention. The purpose of this study was to conduct an experimental assessment of the body-force-generating performance of a wide range of dielectric materials in search of opportunities to improve DBD actuator performance. Materials studied included commonly available plastics and glasses as well as a custom-fabricated polyimide aerogel. Diagnostics included static induced thrust, electrical circuit parameters for 2D surface discharges and 1D volume discharges, and dielectric material properties. Lumped-parameter circuit simulations for the 1D case were conducted showing good correspondence to experimental data provided that stray capacitances are included. The effect of atmospheric humidity on DBD performance was studied showing a large influence on thrust. The main conclusion is that for homogeneous, dielectric materials at forcing voltages less than that required for streamer formation, the material chemical composition appears to have no effect on body force generation when actuator impedance is properly accounted for.

  14. Fluorinated Graphene as High Performance Dielectric Materials and the Applications for Graphene Nanoelectronics

    PubMed Central

    Ho, Kuan-I; Huang, Chi-Hsien; Liao, Jia-Hong; Zhang, Wenjing; Li, Lain-Jong; Lai, Chao-Sung; Su, Ching-Yuan

    2014-01-01

    There is broad interest in surface functionalization of 2D materials and its related applications. In this work, we present a novel graphene layer transistor fabricated by introducing fluorinated graphene (fluorographene), one of the thinnest 2D insulator, as the gate dielectric material. For the first time, the dielectric properties of fluorographene, including its dielectric constant, frequency dispersion, breakdown electric field and thermal stability, were comprehensively investigated. We found that fluorographene with extremely thin thickness (5 nm) can sustain high resistance at temperature up to 400°C. The measured breakdown electric field is higher than 10 MV cm−1, which is the heightest value for dielectric materials in this thickness. Moreover, a proof-of-concept methodology, one-step fluorination of 10-layered graphene, is readily to obtain the fluorographene/graphene heterostructures, where the top-gated transistor based on this structure exhibits an average carrier mobility above 760 cm2/Vs, higher than that obtained when SiO2 and GO were used as gate dielectric materials. The demonstrated fluorographene shows excellent dielectric properties with fast and scalable processing, providing a universal applications for the integration of versatile nano-electronic devices. PMID:25081226

  15. Fluorinated graphene as high performance dielectric materials and the applications for graphene nanoelectronics.

    PubMed

    Ho, Kuan-I; Huang, Chi-Hsien; Liao, Jia-Hong; Zhang, Wenjing; Li, Lain-Jong; Lai, Chao-Sung; Su, Ching-Yuan

    2014-07-31

    There is broad interest in surface functionalization of 2D materials and its related applications. In this work, we present a novel graphene layer transistor fabricated by introducing fluorinated graphene (fluorographene), one of the thinnest 2D insulator, as the gate dielectric material. For the first time, the dielectric properties of fluorographene, including its dielectric constant, frequency dispersion, breakdown electric field and thermal stability, were comprehensively investigated. We found that fluorographene with extremely thin thickness (5 nm) can sustain high resistance at temperature up to 400 °C. The measured breakdown electric field is higher than 10 MV cm(-1), which is the heightest value for dielectric materials in this thickness. Moreover, a proof-of-concept methodology, one-step fluorination of 10-layered graphene, is readily to obtain the fluorographene/graphene heterostructures, where the top-gated transistor based on this structure exhibits an average carrier mobility above 760 cm(2)/Vs, higher than that obtained when SiO₂ and GO were used as gate dielectric materials. The demonstrated fluorographene shows excellent dielectric properties with fast and scalable processing, providing a universal applications for the integration of versatile nano-electronic devices.

  16. Millimeter wave and terahertz dielectric properties of biological materials

    NASA Astrophysics Data System (ADS)

    Khan, Usman Ansar

    Broadband dielectric properties of materials can be employed to identify, detect, and characterize materials through their unique spectral signatures. In this study, millimeter wave, submillimeter wave, and terahertz dielectric properties of biological substances inclusive of liquids, solids, and powders were obtained using Dispersive Fourier Transform Spectroscopy (DFTS). Two broadband polarizing interferometers were constructed to test materials from 60 GHz to 1.2 THz. This is an extremely difficult portion of the frequency spectrum to obtain a material's dielectric properties since neither optical nor microwave-based techniques provide accurate data. The dielectric characteristics of liquids such as cyclohexane, chlorobenzene, benzene, ethanol, methanol, 1,4 dioxane, and 10% formalin were obtained using the liquid interferometer. Subsequently the solid interferometer was utilized to determine the dielectric properties of human breast tissues, which are fixed and preserved in 10% formalin. This joint collaboration with the Tufts New England Medical Center demonstrated a significant difference between the dielectric response of tumorous and non-tumorous breast tissues across the spectrum. Powders such as anthrax, flour, talc, corn starch, dry milk, and baking soda have been involved in a number of security threats and false alarms around the globe in the last decade. To be able to differentiate hoax attacks and serious security threats, the dielectric properties of common household powders were also examined using the solid interferometer to identify the powders' unique resonance peaks. A new sample preparation kit was designed to test the powder specimens. It was anticipated that millimeter wave and terahertz dielectric characterization will enable one to clearly distinguish one powder from the other; however most of the powders had relatively close dielectric responses and only Talc had a resonance signature recorded at 1.135 THz. Furthermore, due to

  17. High dielectric constant and low dielectric loss hybrid nanocomposites fabricated with ferroelectric polymer matrix and BaTiO3 nanofibers modified with perfluoroalkylsilane

    NASA Astrophysics Data System (ADS)

    Zhang, Xianhong; Ma, Yuhong; Zhao, Changwen; Yang, Wantai

    2014-06-01

    Interfacial interaction and compatibility between the ceramic dielectric and polymer matrix have strong impact on the dielectric permittivity and dielectric loss of their composites. In this work, we presented a simple strategy to fabricate flexible dielectric composite of high dielectric constant BaTiO3 (BT) nanofiber and ferroelectric poly(vinylidene fluoride) (PVDF) matrix. The electrospun BT nanofiber was sintered at about 800 °C to form perovskite crystalline. Fluorosilane 1H,1H,2H,2H-perfluorooctyltrimethoxysilane was used to introduce a short perfluoroalkyl chain to the surface of BT nanofiber by silane coupling. The effects of content of modified BT nanofiber on the dielectric performance of the composites were investigated by broadband dielectric spectroscopy. The results in comparison with pure PVDF showed that the dielectric constant increased about 2 times (from 10 to 22) and dielectric loss tan δ reduced about 50% (from 0.12 to 0.06) when the loading of modified BT nanofiber was up to 20 v%. In the same loading fraction of BT nanofibers (10 v%), the dielectric loss of fluorosilane modified sample (tan δ = 0.08) was lower than that of unmodified one (tan δ = 0.1). In the range of 20-100 °C, the k showed almost no dependence on the temperature. However, the dielectric loss revealed a trend of decreasing at first and increased later with the increasing of temperature, and reached the lowest value (tanδ = 0.01) at about 60 °C.

  18. Residual stress evolution in multilayer ceramic capacitors corresponding to layer increase and its correlation to the dielectric constant

    NASA Astrophysics Data System (ADS)

    Park, Jong-Sung; Kim, Sujin; Shin, Hyunho; Jung, Hyun Suk; Hong, Kug Sun

    2005-05-01

    The residual thermal stress in multilayer ceramic capacitors (MLCCs) with varying number of layers was analyzed using finite element analysis, in order to find the links among the dielectric constant, the number of layers, and the stress state. In the active region of the MLCC, the in-plane stresses in a ceramic layer, σ11 and σ22, were compressive while the out-of-plane stress, σ33, was mostly tensile. Changes in the dielectric constant were related to the reinforcement of the compressive in-plane stress components for small numbers of layers, while out-of-plane tensile stress was attributed to the increased dielectric constant when the number of layers was large. In the intermediate regime, in-plane stress components and out-of-plane components both affected the dielectric constant.

  19. Imaging the static dielectric constant in vitro and in living cells by a bioconjugable GFP chromophore analog.

    PubMed

    Signore, Giovanni; Abbandonato, Gerardo; Storti, Barbara; Stöckl, Martin; Subramaniam, Vinod; Bizzarri, Ranieri

    2013-02-28

    A fluorescent probe structurally similar to the GFP chromophore is demonstrated to report the local static dielectric constant. This probe can be chemically functionalized for selective targeting at the intracellular level.

  20. Corrosion in low dielectric constant Si-O based thin films: Buffer concentration effects

    SciTech Connect

    Zeng, F. W.; Lane, M. W.; Gates, S. M.

    2014-05-15

    Organosilicate glass (OSG) is often used as an interlayer dielectric (ILD) in high performance integrated circuits. OSG is a brittle material and prone to stress-corrosion cracking reminiscent of that observed in bulk glasses. Of particular concern are chemical-mechanical planarization techniques and wet cleans involving solvents commonly encountered in microelectronics fabrication where the organosilicate film is exposed to aqueous environments. Previous work has focused on the effect of pH, surfactant, and peroxide concentration on the subcritical crack growth of these films. However, little or no attention has focused on the effect of the conjugate acid/base concentration in a buffer. Accordingly, this work examines the “strength” of the buffer solution in both acidic and basic environments. The concentration of the buffer components is varied keeping the ratio of acid/base and therefore pH constant. In addition, the pH was varied by altering the acid/base ratio to ascertain any additional effect of pH. Corrosion tests were conducted with double-cantilever beam fracture mechanics specimens and fracture paths were verified with ATR-FTIR. Shifts in the threshold fracture energy, the lowest energy required for bond rupture in the given environment, G{sub TH}, were found to shift to lower values as the concentration of the base in the buffer increased. This effect was found to be much larger than the effect of the hydroxide ion concentration in unbuffered solutions. The results are rationalized in terms of the salient chemical bond breaking process occurring at the crack tip and modeled in terms of the chemical potential of the reactive species.

  1. Corrosion in low dielectric constant Si-O based thin films: Buffer concentration effects

    NASA Astrophysics Data System (ADS)

    Zeng, F. W.; Gates, S. M.; Lane, M. W.

    2014-05-01

    Organosilicate glass (OSG) is often used as an interlayer dielectric (ILD) in high performance integrated circuits. OSG is a brittle material and prone to stress-corrosion cracking reminiscent of that observed in bulk glasses. Of particular concern are chemical-mechanical planarization techniques and wet cleans involving solvents commonly encountered in microelectronics fabrication where the organosilicate film is exposed to aqueous environments. Previous work has focused on the effect of pH, surfactant, and peroxide concentration on the subcritical crack growth of these films. However, little or no attention has focused on the effect of the conjugate acid/base concentration in a buffer. Accordingly, this work examines the "strength" of the buffer solution in both acidic and basic environments. The concentration of the buffer components is varied keeping the ratio of acid/base and therefore pH constant. In addition, the pH was varied by altering the acid/base ratio to ascertain any additional effect of pH. Corrosion tests were conducted with double-cantilever beam fracture mechanics specimens and fracture paths were verified with ATR-FTIR. Shifts in the threshold fracture energy, the lowest energy required for bond rupture in the given environment, GTH, were found to shift to lower values as the concentration of the base in the buffer increased. This effect was found to be much larger than the effect of the hydroxide ion concentration in unbuffered solutions. The results are rationalized in terms of the salient chemical bond breaking process occurring at the crack tip and modeled in terms of the chemical potential of the reactive species.

  2. Increased Accuracy in the Measurement of the Dielectric Constant of Seawater at 1.413 GHz

    NASA Technical Reports Server (NTRS)

    Zhou, Y.; Lang R.; Drego, C.; Utku, C.; LeVine, D.

    2012-01-01

    This paper describes the latest results for the measurements of the dielectric constant at 1.413 GHz by using a resonant cavity technique. The purpose of these measurements is to develop an accurate relationship for the dependence of the dielectric constant of sea water on temperature and salinity which is needed by the Aquarius inversion algorithm to retrieve salinity. Aquarius is the major instrument on the Aquarius/SAC-D observatory, a NASA/CONAE satellite mission launched in June of20ll with the primary mission of measuring global sea surface salinity to an accuracy of 0.2 psu. Aquarius measures salinity with a 1.413 GHz radiometer and uses a scatterometer to compensate for the effects of surface roughness. The core part of the seawater dielectric constant measurement system is a brass microwave cavity that is resonant at 1.413 GHz. The seawater is introduced into the cavity through a capillary glass tube having an inner diameter of 0.1 mm. The change of resonance frequency and the cavity Q value are used to determine the real and imaginary parts of the dielectric constant of seawater introduced into the thin tube. Measurements are automated with the help of software developed at the George Washington University. In this talk, new results from measurements made since September 2010 will be presented for salinities 30, 35 and 38 psu with a temperature range of O C to 350 C in intervals of 5 C. These measurements are more accurate than earlier measurements made in 2008 because of a new method for measuring the calibration constant using methanol. In addition, the variance of repeated seawater measurements has been reduced by letting the system stabilize overnight between temperature changes. The new results are compared to the Kline Swift and Meissner Wentz model functions. The importance of an accurate model function will be illustrated by using these model functions to invert the Aquarius brightness temperature to get the salinity values. The salinity values

  3. Testing the Tube Super-Dielectric Material Hypothesis: Increased Energy Density Using NaCl

    NASA Astrophysics Data System (ADS)

    Gandy, Jonathan; Cortes, Francisco Javier Quintero; Phillips, Jonathan

    2016-11-01

    The focus of the present work is the evaluation of the low-frequency dielectric performance of titanium dioxide nanotube arrays, created by anodization, filled with aqueous NaCl solutions. At low frequency (ca. <10-2 Hz), capacitors made up of this so-called tube super-dielectric material were found to have extreme dielectric constants, greater than 1 billion. The same capacitors also registered unprecedented energy densities, nearly 400 J/cm3, better than that observed (<250 J/cm3) for the same type of anodized titania filled with an aqueous solution of NaNO3, and about an order of magnitude better than commercial supercapacitors. Sufficient data were collected to propose a correlation relating dielectric thickness and salt concentration to overall energy density.

  4. Electrostatic analysis of the interactions between charged particles of dielectric materials.

    PubMed

    Bichoutskaia, Elena; Boatwright, Adrian L; Khachatourian, Armik; Stace, Anthony J

    2010-07-14

    An understanding of the electrostatic interactions that exist between charged particles of dielectric materials has applications that span much of chemistry, physics, biology, and engineering. Areas of interest include cloud formation, ink-jet printing, and the stability of emulsions. A general solution to the problem of calculating electrostatic interactions between charged dielectric particles is presented. The solution converges very rapidly for low values of the dielectric constant and is stable up to the point where particles touch. Through applications to unspecified particles with a range of size and charge ratios, the model shows that there exist distinct regions of dielectric space where particles with the same sign of charge are strongly attracted to one another.

  5. Giant dielectric constant in TiO{sub 2}/Al{sub 2}O{sub 3} nanolaminates grown on doped silicon substrate by pulsed laser deposition

    SciTech Connect

    Walke, P.; Bouregba, R.; Mercey, B.; Lüders, U.; Lefevre, A.; Parat, G.; Lallemand, F.; Voiron, F.

    2014-03-07

    High quality amorphous nanolaminates by means of alternate Al{sub 2}O{sub 3} and TiO{sub 2} oxide sublayers were grown with atomic scale thickness control by pulsed laser deposition. A giant dielectric constant (>10 000), strongly enhanced compared to the value of either Al{sub 2}O{sub 3} or TiO{sub 2} or their solid solution, was observed. The dependence of the dielectric constant and the dielectric loss on the individual layer thickness of each of the constituting materials was investigated between 0.3 nm and 1 nm, in order to understand the prevailing mechanisms and allow for an optimization of the performances. An impedance study confirmed as the key source of the giant dielectric constant a Maxwell–Wagner type dielectric relaxation, caused by space charge polarization in the nanolaminate structure. The current work provides better insight of nanolaminates and their sublayer thickness engineering for potential applications.

  6. Dielectric properties of doping-free NaMn{sub 7}O{sub 12}: Origin of the observed colossal dielectric constant

    SciTech Connect

    Cabassi, R.; Bolzoni, F.; Gauzzi, A.; Gilioli, E.; Prodi, A.; Licci, F.

    2006-07-15

    The semiconducting NaMn{sub 7}O{sub 12} is a doping-free compound with several coexistent properties such as orbital ordering, charge ordering, and magnetic orderings of different types. We investigated its dielectric response by means of frequency impedance measurements in the range from 20 Hz to 1 MHz. Standard measurements on metallized samples exhibit an apparent colossal dielectric constant (CDC) with an {epsilon}{sub R} value of several thousands at low frequencies, but a careful equivalent circuit analysis allows one to ascribe the observed CDC to the effect of a depletion layer on the metal-semiconductor junctions. We bypass this effect by means of a nonstandard technique employing mica linings: the resulting dielectric behavior exhibits the presence of the charge ordering transition at T{sub CO}=176 K and shows a net bulk dielectric constant value {epsilon}{sub R}{approx_equal}68 at room temperature.

  7. Nanostructure multilayer dielectric materials for capacitors and insulators

    DOEpatents

    Barbee, T.W. Jr.; Johnson, G.W.

    1998-04-21

    A capacitor is formed of at least two metal conductors having a multilayer dielectric and opposite dielectric-conductor interface layers in between. The multilayer dielectric includes many alternating layers of amorphous zirconium oxide (ZrO{sub 2}) and alumina (Al{sub 2}O{sub 3}). The dielectric-conductor interface layers are engineered for increased voltage breakdown and extended service life. The local interfacial work function is increased to reduce charge injection and thus increase breakdown voltage. Proper material choices can prevent electrochemical reactions and diffusion between the conductor and dielectric. Physical vapor deposition is used to deposit the zirconium oxide (ZrO{sub 2}) and alumina (Al{sub 2}O{sub 3}) in alternating layers to form a nano-laminate. 1 fig.

  8. Nanostructure multilayer dielectric materials for capacitors and insulators

    DOEpatents

    Barbee, Jr., Troy W.; Johnson, Gary W.

    1998-04-21

    A capacitor is formed of at least two metal conductors having a multilayer dielectric and opposite dielectric-conductor interface layers in between. The multilayer dielectric includes many alternating layers of amorphous zirconium oxide (ZrO.sub.2) and alumina (Al.sub.2 O.sub.3). The dielectric-conductor interface layers are engineered for increased voltage breakdown and extended service life. The local interfacial work function is increased to reduce charge injection and thus increase breakdown voltage. Proper material choices can prevent electrochemical reactions and diffusion between the conductor and dielectric. Physical vapor deposition is used to deposit the zirconium oxide (ZrO.sub.2) and alumina (Al.sub.2 O.sub.3) in alternating layers to form a nano-laminate.

  9. Quantum theory of the dielectric constant of a magnetized plasma and astrophysical applications. I.

    NASA Technical Reports Server (NTRS)

    Canuto, V.; Ventura, J.

    1972-01-01

    A quantum mechanical treatment of an electron plasma in a constant and homogeneous magnetic field is considered, with the aim of (1) defining the range of validity of the magnetoionic theory (2) studying the deviations from this theory, in applications involving high densities, and intense magnetic field. While treating the magnetic field exactly, a perturbation approach in the photon field is used to derive general expressions for the dielectric tensor. Numerical estimates on the range of applicability of the magnetoionic theory are given for the case of the 'one-dimensional' electron gas, where only the lowest Landau level is occupied.

  10. Influence of the gap size and dielectric constant of the packing on the plasma discharge in a packed bed dielectric barrier discharge reactor: a fluid modeling study

    NASA Astrophysics Data System (ADS)

    van Laer, Koen; Bogaerts, Annemie

    2016-09-01

    Packed bed dielectric barrier discharge (DBD) reactors have proven to be very useful sources of non-thermal plasma for a wide range of applications, of which the environmental applications have received most attention in recent years. Compared to an empty DBD reactor, a packing was introduced to either enhance the energy efficiency of the process, or, if the packing is catalytically active, steer the process towards a preferred end product. A wide range of geometries, bead sizes and bead materials have been tested experimentally in the past. However, since experimental diagnostics become more difficult with a packing present, a computational study is proposed to gain more insight. Using COMSOL's built in plasma module, a 2D axisymmetric fluid model is developed to study the influence of the gap size and the dielectric constant (ɛ) of the packing. Helium is used as discharge gas, at atmospheric pressure and room temperature. By decreasing the gas gap, the electric field strength is enhanced, resulting in a higher number of current peaks per half cycle of applied rf potential. Increasing ɛ also enhances the electric field strength. However, after a certain ɛ, its influence saturates. The electric field strength will no longer increase, leaving the discharge behavior unchanged.

  11. Quantitative property-structural relation modeling on polymeric dielectric materials

    NASA Astrophysics Data System (ADS)

    Wu, Ke

    Nowadays, polymeric materials have attracted more and more attention in dielectric applications. But searching for a material with desired properties is still largely based on trial and error. To facilitate the development of new polymeric materials, heuristic models built using the Quantitative Structure Property Relationships (QSPR) techniques can provide reliable "working solutions". In this thesis, the application of QSPR on polymeric materials is studied from two angles: descriptors and algorithms. A novel set of descriptors, called infinite chain descriptors (ICD), are developed to encode the chemical features of pure polymers. ICD is designed to eliminate the uncertainty of polymer conformations and inconsistency of molecular representation of polymers. Models for the dielectric constant, band gap, dielectric loss tangent and glass transition temperatures of organic polymers are built with high prediction accuracy. Two new algorithms, the physics-enlightened learning method (PELM) and multi-mechanism detection, are designed to deal with two typical challenges in material QSPR. PELM is a meta-algorithm that utilizes the classic physical theory as guidance to construct the candidate learning function. It shows better out-of-domain prediction accuracy compared to the classic machine learning algorithm (support vector machine). Multi-mechanism detection is built based on a cluster-weighted mixing model similar to a Gaussian mixture model. The idea is to separate the data into subsets where each subset can be modeled by a much simpler model. The case study on glass transition temperature shows that this method can provide better overall prediction accuracy even though less data is available for each subset model. In addition, the techniques developed in this work are also applied to polymer nanocomposites (PNC). PNC are new materials with outstanding dielectric properties. As a key factor in determining the dispersion state of nanoparticles in the polymer matrix

  12. Quantum chemistry study of dielectric materials deposition

    NASA Astrophysics Data System (ADS)

    Widjaja, Yuniarto

    The drive to continually decrease the device dimensions of integrated circuits in the microelectronics industry requires that deposited films approach subnanometer thicknesses. Hence, a fundamental understanding of the physics and chemistry of film deposition is important to obtain better control of the properties of the deposited film. We use ab initio quantum chemistry calculations to explore chemical reactions at the atomic level. Important thermodynamic and kinetic parameters are then obtained, which can then be used as inputs in constructing first-principles based reactor models. Studies of new systems for which data are not available can be conducted as well. In this dissertation, we use quantum chemistry simulations to study the deposition of gate dielectrics for metal-oxide-semiconductor (MOS) devices. The focus of this study is on heterogeneous reactions between gaseous precursors and solid surfaces. Adsorbate-surface interactions introduce additional degrees of complexity compared to the corresponding gas-phase or solid-state reactions. The applicability and accuracy of cluster approximations to represent solid surfaces are first investigated. The majority of our results are obtained using B3LYP density functional theory (DFT). The structures of reactants, products, and transition states are obtained, followed by calculations of thermochemical and kinetic properties. Whenever experimental data are available, qualitative and/or quantitative comparisons are drawn. Atomistic mechanisms and the energetics of several reactions leading to the deposition of SiO2, Si3N4, and potential new high-kappa materials such as ZrO2, HfO2, and Al 2O3 have been explored in this dissertation. Competing reaction pathways are explored for each of the deposition reactions studied. For example, the potential energy surface (PES) for ZrO2 ALD shows that the reactions proceed through a trapping-mediated mechanism, which results in a competition between desorption and decomposition

  13. Statistical mechanics approach to the electric polarization and dielectric constant of band insulators

    NASA Astrophysics Data System (ADS)

    Combes, Frédéric; Trescher, Maximilian; Piéchon, Frédéric; Fuchs, Jean-Noël

    2016-10-01

    We develop a theory for the analytic computation of the free energy of band insulators in the presence of a uniform and constant electric field. The two key ingredients are a perturbation-like expression of the Wannier-Stark energy spectrum of electrons and a modified statistical mechanics approach involving a local chemical potential in order to deal with the unbounded spectrum and impose the physically relevant electronic filling. At first order in the field, we recover the result of King-Smith, Vanderbilt, and Resta for the electric polarization in terms of a Zak phase—albeit at finite temperature—and, at second order, deduce a general formula for the electric susceptibility, or equivalently for the dielectric constant. Advantages of our method are the validity of the formalism both at zero and finite temperature and the easy computation of higher order derivatives of the free energy. We verify our findings on two different one-dimensional tight-binding models.

  14. Effective approach for calculations of absolute stability of proteins using focused dielectric constants.

    PubMed

    Vicatos, Spyridon; Roca, Maite; Warshel, Arieh

    2009-11-15

    The ability to predict the absolute stability of proteins based on their corresponding sequence and structure is a problem of great fundamental and practical importance. In this work, we report an extensive, refinement and validation of our recent approach (Roca et al., FEBS Lett 2007;581:2065-2071) for predicting absolute values of protein stability DeltaG(fold). This approach employs the semimacroscopic protein dipole Langevin dipole method in its linear response approximation version (PDLD/S-LRA) while using the best fitted values of the dielectric constants epsilon'(p) and epsilon'(eff) for the self energy and charge-charge interactions, respectively. The method is validated on a diverse set of 45 proteins. It is found that the best fitted values of both dielectric constants are around 40. However, the self energy of internal residues and the charge-charge interactions of Lys have to be treated with care, using a somewhat lower values of epsilon'(p) and epsilon'(eff). The predictions of DeltaG(fold) reported here, have an average error of only 1.8 kcal/mole compared to the observed values, making our method very promising for estimating protein stability. It also provides valuable insight into the complex electrostatic phenomena taking place in folded proteins.

  15. Supercritical carbon dioxide extraction of porogens for the preparation of ultralow-dielectric-constant films

    SciTech Connect

    Toney, Michael F

    2003-06-20

    Supercritical carbon dioxide (SCCO2) extraction of a CO{sub 2}-soluble poly(propylene glycol) (PPG) porogen from poly(methylsilsesquioxane) (PMSSQ) cured to temperatures adequate to initiate matrix condensation, but still below the decomposition temperature of the porogen is demonstrated to produce nanoporous, ultralow dielectric constant thin films. Both closed and open cell porous structures were prepared simply by varying the porogen load in the organic/inorganic hybrid films. The porogen loads investigated in the present work ranged from 25-55 wt.%. Structural characterization of the samples conducted using transmission electron microscope (TEM), small angle X-ray scattering (SAXS) and Fourier transform infrared spectroscopy (FTIR) confirms the successful extraction of the porogen from the PMSSQ matrix at relatively low temperatures ({le} 200 C). The standard thermal decomposition process is performed at much higher temperatures (typically in the range of 400 C-450 C). The values of dielectric constants and refractive indices measured are in good agreement with the structural properties of these samples.

  16. CMUTs with High-K Atomic Layer Deposition Dielectric Material Insulation Layer

    PubMed Central

    Xu, Toby; Tekes, Coskun; Degertekin, F. Levent

    2014-01-01

    Use of high-κ dielectric, atomic layer deposition (ALD) materials as an insulation layer material for capacitive micromachined ultrasonic transducers (CMUTs) is investigated. The effect of insulation layer material and thickness on CMUT performance is evaluated using a simple parallel plate model. The model shows that both high dielectric constant and the electrical breakdown strength are important for the dielectric material, and significant performance improvement can be achieved, especially as the vacuum gap thickness is reduced. In particular, ALD hafnium oxide (HfO2) is evaluated and used as an improvement over plasma-enhanced chemical vapor deposition (PECVD) silicon nitride (SixNy) for CMUTs fabricated by a low-temperature, complementary metal oxide semiconductor transistor-compatible, sacrificial release method. Relevant properties of ALD HfO2 such as dielectric constant and breakdown strength are characterized to further guide CMUT design. Experiments are performed on parallel fabricated test CMUTs with 50-nm gap and 16.5-MHz center frequency to measure and compare pressure output and receive sensitivity for 200-nm PECVD SixNy and 100-nm HfO2 insulation layers. Results for this particular design show a 6-dB improvement in receiver output with the collapse voltage reduced by one-half; while in transmit mode, half the input voltage is needed to achieve the same maximum output pressure. PMID:25474786

  17. CMUTs with high-K atomic layer deposition dielectric material insulation layer.

    PubMed

    Xu, Toby; Tekes, Coskun; Degertekin, F

    2014-12-01

    Use of high-κ dielectric, atomic layer deposition (ALD) materials as an insulation layer material for capacitive micromachined ultrasonic transducers (CMUTs) is investigated. The effect of insulation layer material and thickness on CMUT performance is evaluated using a simple parallel plate model. The model shows that both high dielectric constant and the electrical breakdown strength are important for the dielectric material, and significant performance improvement can be achieved, especially as the vacuum gap thickness is reduced. In particular, ALD hafnium oxide (HfO2) is evaluated and used as an improvement over plasma-enhanced chemical vapor deposition (PECVD) silicon nitride (Six)Ny)) for CMUTs fabricated by a low-temperature, complementary metal oxide semiconductor transistor-compatible, sacrificial release method. Relevant properties of ALD HfO2) such as dielectric constant and breakdown strength are characterized to further guide CMUT design. Experiments are performed on parallel fabricated test CMUTs with 50-nm gap and 16.5-MHz center frequency to measure and compare pressure output and receive sensitivity for 200-nm PECVD Six)Ny) and 100-nm HfO2) insulation layers. Results for this particular design show a 6-dB improvement in receiver output with the collapse voltage reduced by one-half; while in transmit mode, half the input voltage is needed to achieve the same maximum output pressure.

  18. Stiff, strong, yet tough free-standing dielectric films of graphene nanosheets-polyurethane nanocomposites with very high dielectric constant and loss

    NASA Astrophysics Data System (ADS)

    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.

  19. Rational design of inorganic dielectric materials with expected permittivity

    PubMed Central

    Xie, Congwei; Oganov, Artem R.; Dong, Dong; Liu, Ning; Li, Duan; Debela, Tekalign Terfa

    2015-01-01

    Techniques for rapid design of dielectric materials with appropriate permittivity for many important technological applications are urgently needed. It is found that functional structure blocks (FSBs) are helpful in rational design of inorganic dielectrics with expected permittivity. To achieve this, coordination polyhedra are parameterized as FSBs and a simple empirical model to evaluate permittivity based on these FSB parameters is proposed. Using this model, a wide range of examples including ferroelectric, high/low permittivity materials are discussed, resulting in several candidate materials for experimental follow-up. PMID:26617342

  20. Rational design of inorganic dielectric materials with expected permittivity.

    PubMed

    Xie, Congwei; Oganov, Artem R; Dong, Dong; Liu, Ning; Li, Duan; Debela, Tekalign Terfa

    2015-11-30

    Techniques for rapid design of dielectric materials with appropriate permittivity for many important technological applications are urgently needed. It is found that functional structure blocks (FSBs) are helpful in rational design of inorganic dielectrics with expected permittivity. To achieve this, coordination polyhedra are parameterized as FSBs and a simple empirical model to evaluate permittivity based on these FSB parameters is proposed. Using this model, a wide range of examples including ferroelectric, high/low permittivity materials are discussed, resulting in several candidate materials for experimental follow-up.

  1. Spatially resolved dielectric constant of confined water and its connection to the non-local nature of bulk water

    NASA Astrophysics Data System (ADS)

    Schaaf, Christian; Gekle, Stephan

    2016-08-01

    We use molecular dynamics simulations to compute the spatially resolved static dielectric constant of water in cylindrical and spherical nanopores as occurring, e.g., in protein water pockets or carbon nanotubes. For this, we derive a linear-response formalism which correctly takes into account the dielectric boundary conditions in the considered geometries. We find that in cylindrical confinement, the axial component behaves similar as the local density akin to what is known near planar interfaces. The radial dielectric constant shows some oscillatory features when approaching the surface if their radius is larger than about 2 nm. Most importantly, however, the radial component exhibits pronounced oscillations at the center of the cavity. These surprising features are traced back quantitatively to the non-local dielectric nature of bulk water.

  2. Crosslinked polyarylene ether nitrile film as flexible dielectric materials with ultrahigh thermal stability.

    PubMed

    Yang, Ruiqi; Wei, Renbo; Li, Kui; Tong, Lifen; Jia, Kun; Liu, Xiaobo

    2016-11-09

    Dielectric film with ultrahigh thermal stability based on crosslinked polyarylene ether nitrile is prepared and characterized. The film is obtained by solution-casting of polyarylene ether nitrile terminated phthalonitrile (PEN-Ph) combined with post self-crosslinking at high temperature. The film shows a 5% decomposition temperature over 520 °C and a glass transition temperature (Tg) around 386 °C. Stable dielectric constant and low dielectric loss are observed for this film in the frequency range of 100-200 kHz and in the temperature range of 25-300 °C. The temperature coefficient of dielectric constant is less than 0.001 °C(-1) even at 400 °C. By cycling heating and cooling up to ten times or heating at 300 °C for 12 h, the film shows good reversibility and robustness of the dielectric properties. This crosslinked PEN film will be a potential candidate as high performance film capacitor electronic devices materials used at high temperature.

  3. Crosslinked polyarylene ether nitrile film as flexible dielectric materials with ultrahigh thermal stability

    NASA Astrophysics Data System (ADS)

    Yang, Ruiqi; Wei, Renbo; Li, Kui; Tong, Lifen; Jia, Kun; Liu, Xiaobo

    2016-11-01

    Dielectric film with ultrahigh thermal stability based on crosslinked polyarylene ether nitrile is prepared and characterized. The film is obtained by solution-casting of polyarylene ether nitrile terminated phthalonitrile (PEN-Ph) combined with post self-crosslinking at high temperature. The film shows a 5% decomposition temperature over 520 °C and a glass transition temperature (Tg) around 386 °C. Stable dielectric constant and low dielectric loss are observed for this film in the frequency range of 100–200 kHz and in the temperature range of 25–300 °C. The temperature coefficient of dielectric constant is less than 0.001 °C‑1 even at 400 °C. By cycling heating and cooling up to ten times or heating at 300 °C for 12 h, the film shows good reversibility and robustness of the dielectric properties. This crosslinked PEN film will be a potential candidate as high performance film capacitor electronic devices materials used at high temperature.

  4. Crosslinked polyarylene ether nitrile film as flexible dielectric materials with ultrahigh thermal stability

    PubMed Central

    Yang, Ruiqi; Wei, Renbo; Li, Kui; Tong, Lifen; Jia, Kun; Liu, Xiaobo

    2016-01-01

    Dielectric film with ultrahigh thermal stability based on crosslinked polyarylene ether nitrile is prepared and characterized. The film is obtained by solution-casting of polyarylene ether nitrile terminated phthalonitrile (PEN-Ph) combined with post self-crosslinking at high temperature. The film shows a 5% decomposition temperature over 520 °C and a glass transition temperature (Tg) around 386 °C. Stable dielectric constant and low dielectric loss are observed for this film in the frequency range of 100–200 kHz and in the temperature range of 25–300 °C. The temperature coefficient of dielectric constant is less than 0.001 °C−1 even at 400 °C. By cycling heating and cooling up to ten times or heating at 300 °C for 12 h, the film shows good reversibility and robustness of the dielectric properties. This crosslinked PEN film will be a potential candidate as high performance film capacitor electronic devices materials used at high temperature. PMID:27827436

  5. The change in dielectric constant, AC conductivity and optical band gaps of polymer electrolyte film: Gamma irradiation

    SciTech Connect

    Raghu, S. Subramanya, K. Sharanappa, C. Mini, V. Archana, K. Sanjeev, Ganesh Devendrappa, H.

    2014-04-24

    The effects of gamma (γ) irradiation on dielectric and optical properties of polymer electrolyte film were investigated. The dielectric constant and ac conductivity increases with γ dose. Also optical band gap decreased from 4.23 to 3.78ev after irradiation. A large dependence of the polymer properties on the irradiation dose was noticed. This suggests that there is a possibility of improving polymer electrolyte properties on gamma irradiation.

  6. Chemical nature of colossal dielectric constant of CaCu3Ti4O12 thin film by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Deng, Guochu; Xanthopoulos, Nicolas; Muralt, Paul

    2008-04-01

    Epitaxial CaCu3Ti4O12 thin films grown by pulsed laser deposition were studied in the as-deposited and oxygen annealed state. The first one exhibited the usual transition from dielectric to colossal dielectric behavior upon increasing the temperature to above 100K. This transition disappeared after annealing at 900°C in air. The two states significantly differ in their x-ray photoelectron spectra. The state of colossal dielectric constant corresponds to a bulk material with considerable amounts of Cu + and Ti3+, combined with Cu species enrichment at the surface. The annealed state exhibited a nearly stoichiometric composition with no Cu+ and Ti3+. The previously observed p-type conduction in the as-deposited state is thus related to oxygen vacancies compensated by the point defects of Cu+ and Ti3+.

  7. Segmental Dynamics and Dielectric Constant of Polysiloxane Polar Copolymers as Plasticizers for Polymer Electrolytes.

    PubMed

    Choi, U Hyeok; Liang, Siwei; Chen, Quan; Runt, James; Colby, Ralph H

    2016-02-10

    Dielectric relaxation spectroscopy was used to investigate the segmental dynamics of a series of siloxane-based polar copolymers combining pendant cyclic carbonates and short poly(ethylene oxide) (PEO) chains. The homopolymer with cyclic carbonate as the only side chain exhibits higher glass transition temperature T(g) and dielectric constant ε(s) than the one with only PEO side chains. For their copolymers the observed T(g) (agreeing well with the predicted values from the Fox equation) and ε(s) decrease with increasing PEO side chain content. These polar polymers exhibit a glassy β relaxation with Arrhenius character, attributed to local chain motions of side groups attached to the main chain, and a segmental α relaxation, associated with the glass transition with a Vogel temperature dependence. As PEO side chain content increases, narrowing of the local glassy β relaxation was observed in the copolymers. The segmental α dynamics were observed to be faster, with an increase in breadth and decrease in strength with increasing PEO side chain content. Owing to the trade-off between T(g) and ε(s), copolymers of intermediate composition result in the highest ionic conductivity when these copolymers are used to plasticize Li single-ion conducting ionomers.

  8. Experimental study of the complex resistivity and dielectric constant of chrome-contaminated soil

    NASA Astrophysics Data System (ADS)

    Liu, Haorui; Yang, Heli; Yi, Fengyan

    2016-08-01

    Heavy metals such as arsenic and chromium often contaminate soils near industrialized areas. Soil samples, made with different water content and chromate pollutant concentrations, are often needed to test soil quality. Because complex resistivity and complex dielectric characteristics of these samples need to be measured, the relationship between these measurement results and chromium concentration as well as water content was studied. Based on soil sample observations, the amplitude of the sample complex resistivity decreased with an increase of contamination concentration and water content. The phase of complex resistivity takes on a tendency of initially decrease, and then increase with the increasing of contamination concentration and water content. For a soil sample with the same resistivity, the higher the amplitude of complex resistivity, the lower the water content and the higher the contamination concentration. The real and imaginary parts of the complex dielectric constant increase with an increase in contamination concentration and water content. Note that resistivity and complex resistivity methods are necessary to adequately evaluate pollution at various sites.

  9. Computer-controlled apparatus for measuring complex elastic, dielectric, and piezoelectric constants of polymer films

    NASA Astrophysics Data System (ADS)

    Furukawa, T.; Date, M.; Ishida, K.; Ikeda, Y.

    1986-02-01

    Principles and design details are described for a fully automatic system measuring frequency and temperature spectra of the complex elastic, dielectric, and piezoelectric constants of polymer films. A microcomputer is used to control all processes including wave generation, sampling, and calculations. A sinusoidal excitation wave is written onto a RAM, readout by an external clock, and applied to a sample via a D/A converter. The resulting signals related to force, deformation, charge, and voltage are simultaneously sampled using the same clock and are determined as complex quantities through Fourier transformation. Their ratios give corresponding complex response functions. A multifrequency signal consisting of eight sinusoidal waves with frequencies of common ratio 2 is used to obtain frequency spectra over two decades at a time. This system operates over a frequency range from 0.01 to 100 Hz for elastic and piezoelectric measurements and from 0.01 Hz to 10 kHz for dielectric measurements at temperatures from -160 to 250 °C with an accuracy of 0.1% in tan δ.

  10. Susceptibility constants of airborne bacteria to dielectric barrier discharge for antibacterial performance evaluation.

    PubMed

    Park, Chul Woo; Hwang, Jungho

    2013-01-15

    Dielectric barrier discharge (DBD) is a promising method to remove contaminant bioaerosols. The collection efficiency of a DBD reactor is an important factor for determining a reactor's removal efficiency. Without considering collection, simply defining the inactivation efficiency based on colony counting numbers for DBD as on and off may lead to overestimation of the inactivation efficiency of the DBD reactor. One-pass removal tests of bioaerosols were carried out to deduce the inactivation efficiency of the DBD reactor using both aerosol- and colony-counting methods. Our DBD reactor showed good performance for removing test bioaerosols for an applied voltage of 7.5 kV and a residence time of 0.24s, with η(CFU), η(Number), and η(Inactivation) values of 94%, 64%, and 83%, respectively. Additionally, we introduce the susceptibility constant of bioaerosols to DBD as a quantitative parameter for the performance evaluation of a DBD reactor. The modified susceptibility constant, which is the ratio of the susceptibility constant to the volume of the plasma reactor, has been successfully demonstrated for the performance evaluation of different sized DBD reactors under different DBD operating conditions. Our methodology will be used for design optimization, performance evaluation, and prediction of power consumption of DBD for industrial applications.

  11. Colossal dielectric constant and relaxation behaviors in Pr:SrTiO{sub 3} ceramics

    SciTech Connect

    Liu Cheng; Liu Peng; Zhou Jianping; Su Lina; Cao Lei; He Ying; Zhang Huaiwu

    2010-05-15

    Sr{sub 1-x}Pr{sub x}TiO{sub 3} ceramics (0.00{<=}x{<=}0.03) were prepared by a traditional solid-state reaction method. Two relaxation processes (marked as A and B) of the Sr{sub 0.09}Pr{sub 0.01}TiO{sub 3} ceramics were investigated by analyzing the E{sub a} values obtained from the Arrhenius law. Colossal dielectric constant (CDC) was first obtained in Sr{sub 0.09}Pr{sub 0.01}TiO{sub 3} ceramics, whose permittivity was up to 3000 (1 kHz, room temperature), greater than that of pure SrTiO{sub 3} ceramics and samples with more Pr addition (x=0.02 and 0.03). This CDC behavior was related to the internal barrier layer capacitance mechanism.

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

    NASA Astrophysics Data System (ADS)

    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 <0.23 and 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.

  13. Dielectric characterization of high-performance spaceflight materials

    NASA Astrophysics Data System (ADS)

    Kleppe, Nathan Alan

    As commercial space travel increases, the need for reliable structural health monitoring to predict possible weaknesses or failures of structural materials also increases. Monitoring of polymer-based materials may be achieved through the use of dielectric spectroscopy by comparing permittivity or conductivity measurements performed on a sample in use to that of a pristine sample. Changes in these measured values or of the relaxation frequencies, if present, can indicate chemical or physical changes occurring within the material and the possible need for maintenance/replacement. In this work, we established indicative trends that occur in the dielectric spectra during accelerated aging of various high-performance polymeric materials (EVOH, PEEK, PPS, and UHMWPE). Uses for these materials range from electrical insulation and protective coatings to windows and air- or space-craft parts that may be subject to environmental damage over long-term operation. Accelerated thermal aging and ultraviolet/water-spray cyclic aging were performed in order to investigate the degradation of the aforementioned material. The Havriliak-Negami model was used in the analysis of the measured dielectric spectra in order to obtain the characteristic fit parameters from which aging-related trends were identified. With reference to the literature and from measured FTIR spectra, observations were connected to the underlying mechanisms causing the dielectric relaxations.

  14. An ultra-wideband dielectric material characterization method using grounded coplanar waveguide and genetic algorithm optimization

    NASA Astrophysics Data System (ADS)

    Hadjloum, Massinissa; El Gibari, Mohammed; Li, Hongwu; Daryoush, Afshin S.

    2015-10-01

    An ultra-wideband complex permittivity extraction method is reported here using numerical fitting of scattering parameters to measured results. A grounded coplanar waveguide transmission line is realized on an unknown dielectric material, whose dielectric constant and loss tangent are extracted by the best fitting of the simulated magnitude, |S21|, and phase, ϕ21, of forward scattering parameter using an electromagnetic full-wave simulator (high frequency structure simulator) to the measured results. The genetic algorithm is employed for optimum rapid extraction, where errors between the numerically simulated and measured S21 (|S21| and ϕ21) are minimized in an iterative manner. As long as the convergence criterion is not satisfied, modifications to dielectric properties are made with this genetic algorithm implemented in Matlab. Feasibility of this extraction technique is validated on benzocyclobutane polymer from 10 MHz to 40 GHz.

  15. Damage by radicals and photons during plasma cleaning of porous low-k SiOCH. II. Water uptake and change in dielectric constant

    SciTech Connect

    Shoeb, Juline; Kushner, Mark J.

    2012-07-15

    Porous dielectric materials provide lower capacitances that reduce RC time delays in integrated circuits. Typical low-k materials include porous SiOCH-silicon dioxide with carbon groups, principally CH{sub 3}, lining the pores. With a high porosity, internally connected pores provide pathways for reactive species to enter into the material. Fluorocarbon plasmas are often used to etch SiOCH, a process that leaves a fluorocarbon polymer on the surface that must later be removed. During cleaning using Ar/O{sub 2} or He/H{sub 2} plasmas, reactions of radicals that diffuse into the SiOCH and photons that penetrate into the SiOCH can remove -CH{sub 3} groups. Due to its higher reactivity, cleaning with Ar/O{sub 2} plasmas removes more -CH{sub 3} groups than He/H{sub 2} plasmas, and so produce more free radical sites, such as -SiO{sub 2} Bullet (a -SiO{sub 2}-CH{sub 3} site with the -CH{sub 3} group removed).Upon exposure to humid air, these free radical sites can chemisorb H{sub 2}O to form hydrophilic Si-OH which can further physisorb H{sub 2}O through hydrogen bonding to form Si-OH(H{sub 2}O). With the high dielectric constant of water, even a small percentage of water uptake can significantly increase the effective dielectric constant of SiOCH. In this paper, we report on results from a computational investigation of the cleaning of SiOCH using Ar/O{sub 2} or He/H{sub 2} plasmas and subsequent exposure to humid air. The authors found that plasma cleaning with He/H{sub 2} mixtures produce less demethylation than cleaning with Ar/O{sub 2} plasmas, as so results in less water uptake, and a smaller increase in dielectric constant. The water that produces the increase in dielectric constant is roughly half chemisorbed and half physisorbed, the latter of which can be removed with mild heating. Sealing the pores with NH{sub 3} plasma treatment reduces water uptake and helps prevent the increase in dielectric constant.

  16. Flexible high-temperature dielectric materials from polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Li, Qi; Chen, Lei; Gadinski, Matthew R.; Zhang, Shihai; Zhang, Guangzu; Li, Haoyu; Haque, Aman; Chen, Long-Qing; Jackson, Tom; Wang, Qing

    2015-07-01

    Dielectric materials, which store energy electrostatically, are ubiquitous in advanced electronics and electric power systems. Compared to their ceramic counterparts, polymer dielectrics have higher breakdown strengths and greater reliability, are scalable, lightweight and can be shaped into intricate configurations, and are therefore an ideal choice for many power electronics, power conditioning, and pulsed power applications. However, polymer dielectrics are limited to relatively low working temperatures, and thus fail to meet the rising demand for electricity under the extreme conditions present in applications such as hybrid and electric vehicles, aerospace power electronics, and underground oil and gas exploration. Here we describe crosslinked polymer nanocomposites that contain boron nitride nanosheets, the dielectric properties of which are stable over a broad temperature and frequency range. The nanocomposites have outstanding high-voltage capacitive energy storage capabilities at record temperatures (a Weibull breakdown strength of 403 megavolts per metre and a discharged energy density of 1.8 joules per cubic centimetre at 250 degrees Celsius). Their electrical conduction is several orders of magnitude lower than that of existing polymers and their high operating temperatures are attributed to greatly improved thermal conductivity, owing to the presence of the boron nitride nanosheets, which improve heat dissipation compared to pristine polymers (which are inherently susceptible to thermal runaway). Moreover, the polymer nanocomposites are lightweight, photopatternable and mechanically flexible, and have been demonstrated to preserve excellent dielectric and capacitive performance after intensive bending cycles. These findings enable broader applications of organic materials in high-temperature electronics and energy storage devices.

  17. Flexible high-temperature dielectric materials from polymer nanocomposites.

    PubMed

    Li, Qi; Chen, Lei; Gadinski, Matthew R; Zhang, Shihai; Zhang, Guangzu; Li, Haoyu; Iagodkine, Elissei; Haque, Aman; Chen, Long-Qing; Jackson, Tom; Wang, Qing

    2015-07-30

    Dielectric materials, which store energy electrostatically, are ubiquitous in advanced electronics and electric power systems. Compared to their ceramic counterparts, polymer dielectrics have higher breakdown strengths and greater reliability, are scalable, lightweight and can be shaped into intricate configurations, and are therefore an ideal choice for many power electronics, power conditioning, and pulsed power applications. However, polymer dielectrics are limited to relatively low working temperatures, and thus fail to meet the rising demand for electricity under the extreme conditions present in applications such as hybrid and electric vehicles, aerospace power electronics, and underground oil and gas exploration. Here we describe crosslinked polymer nanocomposites that contain boron nitride nanosheets, the dielectric properties of which are stable over a broad temperature and frequency range. The nanocomposites have outstanding high-voltage capacitive energy storage capabilities at record temperatures (a Weibull breakdown strength of 403 megavolts per metre and a discharged energy density of 1.8 joules per cubic centimetre at 250 degrees Celsius). Their electrical conduction is several orders of magnitude lower than that of existing polymers and their high operating temperatures are attributed to greatly improved thermal conductivity, owing to the presence of the boron nitride nanosheets, which improve heat dissipation compared to pristine polymers (which are inherently susceptible to thermal runaway). Moreover, the polymer nanocomposites are lightweight, photopatternable and mechanically flexible, and have been demonstrated to preserve excellent dielectric and capacitive performance after intensive bending cycles. These findings enable broader applications of organic materials in high-temperature electronics and energy storage devices.

  18. Effect of dielectric material on bipolar nanosecond pulse diffuse dielectric barrier discharge in air at atmospheric pressure.

    PubMed

    Tang, Kai; Wang, Wenchun; Yang, Dezheng; Zhang, Shuai; Yang, Yang; Liu, Zhijie

    2013-08-01

    In this paper, dielectric plates made by ceramic, quartz and polytetrafluoroethylene (PTFE) respectively are employed to generate low gas temperature, diffuse dielectric barrier discharge plasma by using a needle-plate electrode configuration in air at atmospheric pressure. Both discharge images and the optical emission spectra are obtained while ceramic, quartz and PTFE are used as dielectric material. Plasma gas temperature is also calculated by comparing the experimental emission spectra with the best fitted spectra of N2 (C(3)Πu→B(3)Πg 1-3) and N2 (C(3)Πu→B(3)Πg 0-2). The effects of different pulse peak voltages and gas gap distances on the emission intensity of N2 (C(3)Πu→B(3)Πg, 0-0, 337.1 nm) and the plasma area on dielectric surface are investigated while ceramic, quartz and PTFE are used as dielectric material. It is found that the permittivity of dielectric material plays an important role in the discharge homogeneity, plasma gas temperature, emission spectra intensity of the discharge, etc. Dielectric with higher permittivity i.e., ceramic means brighter discharge luminosity and stronger emission spectra intensity of N2 (C(3)Πu→B(3)Πg, 0-0, 337.1 nm) among the three dielectric materials. However, more homogeneous, larger plasma area on dielectric surface and lower plasma gas temperature can be obtained under dielectric with lower permittivity i.e., PTFE. The emission spectra intensity and plasma gas temperature of the discharge while the dielectric plate is made by quartz are smaller than that while ceramic is used as dielectric material and bigger than that when PTFE is used as dielectric material.

  19. Microwave dielectric sensing of bulk density of granular materials

    NASA Astrophysics Data System (ADS)

    Trabelsi, Samir; Kraszewski, Andrzej W.; Nelson, Stuart O.

    2001-12-01

    A nondestructive dielectric method for sensing bulk density of granular materials is presented. The bulk density is determined from measurement of the dielectric properties of these materials at a single microwave frequency without knowledge of their moisture content and temperature. Bulk density calibration equations are generated from a complex-plane representation of the dielectric properties normalized with respect to bulk density. The effectiveness of the method is shown through measurement of the dielectric properties at 7 GHz for materials with significant compositional and structural differences, i.e. wheat, oats, corn and soybeans, over wide ranges of moisture content and temperature. The standard error of calibration and the relative error calculated for each material indicate that the method is as accurate as or better than commonly used methods for on-line density determination. Because the density is expressed in terms of the relative complex permittivity, the method can be applied regardless of the measurement technique (using transmission lines, a resonant cavity, admittance or impedance).

  20. Dielectric properties of solutions of oil materials solubilized by sodium dodecyl sulfate in aqueous solutions

    SciTech Connect

    Abe, M.; Shimizu, A.; Ogino, K.

    1982-08-01

    One of the most important properties of micellar systems is their ability to solubilize a variety of species. For aqueous micelles, solubilization is related closely to the hydrophobic and hydrophilic properties of the solubilizate. Different sites of solubilization and orientations may be involved, depending on the structure of the solubilizate. A number of studies on solubilization have been performed experimentally and theoretically. Dielectric constant measurement has proved to be a powerful tool for the investigation of permanent dipole moments of various molecules and of the behavior in solution of various substances, and has been applied in various fields. This technique has been used to determine the chemical structure of surfactants, but not to investigate the solubilization of oily materials in aqueous solution. The dielectric constants and ac electric conductivities observed when a solubilizate is added to an aqueous solution of an anionic surfactant and the differences in the solubilizing behavior due to different kinds of polar groups are discussed. 30 references.

  1. Microwave sintering studies on low loss (Zn, Mg)TiO3 dielectric resonator materials.

    PubMed

    Sirugudu, Roopas Kiran; Vemuri, Rama Krishna Murthy; Murty, B S

    2013-01-01

    Low dielectric loss Zn07Mg0.3TiO3 and MgTiO3 microwave dielectric resonators were prepared by the conventional solid state reaction method. The microwave interaction with these materials has been studied using both single-mode and multimode microwave furnaces operating at a frequency of 2.45 GHz. Microwave sintering could be achieved using a multimode microwave furnace only, whereas, interaction with a single-mode furnace showed plasma generation. Phase formation was observed by X-ray diffraction. Microwave dielectric characteristics such as dielectric constant (epsilon'), quality factor (Q x f) and temperature coefficient of resonant frequency (tauf) of microwave sintered samples were measured using a vector network analyzer and compared with conventional sintered ones. Microstructure of all the conventional and microwave sintered samples was observed using high resolution scanning electron microscope. Although epsilon' and tauf of the conventional and microwave sintered samples are found to be comparable, the quality factor (the vital characteristic of dielectric resonators) of microwave sintered samples are observed to be much lower than those obtained by conventional sintering. The difference in these values is discussed with respect to the grain size.

  2. Molecular Dynamics Evaluation of Dielectric-Constant Mixing Rules for H2O-CO2 at Geologic Conditions

    PubMed Central

    Mountain, Raymond D.; Harvey, Allan H.

    2015-01-01

    Modeling of mineral reaction equilibria and aqueous-phase speciation of C-O-H fluids requires the dielectric constant of the fluid mixture, which is not known from experiment and is typically estimated by some rule for mixing pure-component values. In order to evaluate different proposed mixing rules, we use molecular dynamics simulation to calculate the dielectric constant of a model H2O–CO2 mixture at temperatures of 700 K and 1000 K at pressures up to 3 GPa. We find that theoretically based mixing rules that depend on combining the molar polarizations of the pure fluids systematically overestimate the dielectric constant of the mixture, as would be expected for mixtures of nonpolar and strongly polar components. The commonly used semiempirical mixing rule due to Looyenga works well for this system at the lower pressures studied, but somewhat underestimates the dielectric constant at higher pressures and densities, especially at the water-rich end of the composition range. PMID:26664009

  3. Non-polarizable force field of water based on the dielectric constant: TIP4P/ε.

    PubMed

    Fuentes-Azcatl, Raúl; Alejandre, José

    2014-02-06

    The static dielectric constant at room temperature and the temperature of maximum density are used as target properties to develop, by molecular dynamics simulations, the TIP4P/ε force field of water. The TIP4P parameters are used as a starting point. The key step, to determine simultaneously both properties, is to perform simulations at 240 K where a molecular dipole moment of minimum density is found. The minimum is shifted to larger values of μ as the distance between the oxygen atom and site M, lOM, decreases. First, the parameters that define the dipole moment are adjusted to reproduce the experimental dielectric constant and then the Lennard-Jones parameters are varied to match the temperature of maximum density. The minimum on density at 240 K allows understanding why reported TIP4P models fail to reproduce the temperature of maximum density, the dielectric constant, or both properties. The new model reproduces some of the thermodynamic and transport anomalies of water. Additionally, the dielectric constant, thermodynamics, and dynamical and structural properties at different temperatures and pressures are in excellent agreement with experimental data. The computational cost of the new model is the same as that of the TIP4P.

  4. Vapor etching of nuclear tracks in dielectric materials

    DOEpatents

    Musket, Ronald G.; Porter, John D.; Yoshiyama, James M.; Contolini, Robert J.

    2000-01-01

    A process involving vapor etching of nuclear tracks in dielectric materials for creating high aspect ratio (i.e., length much greater than diameter), isolated cylindrical holes in dielectric materials that have been exposed to high-energy atomic particles. The process includes cleaning the surface of the tracked material and exposing the cleaned surface to a vapor of a suitable etchant. Independent control of the temperatures of the vapor and the tracked materials provide the means to vary separately the etch rates for the latent track region and the non-tracked material. As a rule, the tracked regions etch at a greater rate than the non-tracked regions. In addition, the vapor-etched holes can be enlarged and smoothed by subsequent dipping in a liquid etchant. The 20-1000 nm diameter holes resulting from the vapor etching process can be useful as molds for electroplating nanometer-sized filaments, etching gate cavities for deposition of nano-cones, developing high-aspect ratio holes in trackable resists, and as filters for a variety of molecular-sized particles in virtually any liquid or gas by selecting the dielectric material that is compatible with the liquid or gas of interest.

  5. Dielectric characterization of high-performance spaceflight materials

    NASA Astrophysics Data System (ADS)

    Kleppe, Nathan; Nurge, Mark A.; Bowler, Nicola

    2015-03-01

    As commercial space travel increases, the need for reliable structural health monitoring to predict possible weaknesses or failures of structural materials also increases. Monitoring of these materials can be done through the use of dielectric spectroscopy by comparing permittivity or conductivity measurements performed on a sample in use to that of a pristine sample from 100 μHz to 3 GHz. Fluctuations in these measured values or of the relaxation frequencies, if present, can indicate chemical or physical changes occurring within the material and the possible need for maintenance/replacement. In this work, we establish indicative trends that occur due to changes in dielectric spectra during accelerated aging of various high-performance polymeric materials: ethylene vinyl alcohol (EVOH), Poly (ether ether ketone) (PEEK), polyphenylene sulfide (PPS), and ultra-high molecular weight polyethylene (UHMWPE). Uses for these materials range from electrical insulation and protective coatings to windows and air- or space-craft parts that may be subject to environmental damage over long-term operation. Samples were prepared by thermal exposure and, separately, by ultraviolet/water-spray cyclic aging. The aged samples showed statistically-significant trends of either increasing or decreasing real or imaginary permittivity values, relaxation frequencies, conduction or the appearance of new relaxation modes. These results suggest that dielectric testing offers the possibility of nondestructive evaluation of the extent of age-related degradation in these materials.

  6. The effect of dielectric constant on binding energy and impurity self-polarization in a GaAs-Ga1- x Al x As spherical quantum dot

    NASA Astrophysics Data System (ADS)

    Mese, A. I.; Cicek, E.; Erdogan, I.; Akankan, O.; Akbas, H.

    2017-03-01

    The ground state, 1s, and the excited state, 2p, energies of a hydrogenic impurity in a GaAs-Ga1- x Al x As spherical quantum dot, are computed as a function of the donor positions. We study how the impurity self-polarization depends on the location of the impurity and the dielectric constant. The excited state anomalous impurity self-polarization in the quantum dot is found to be present in the absence of any external influence and strongly depends on the impurity position and the radius of the dot. Therefore, the excited state anomalous impurity self-polarization can give information about the impurity position in the system. Also, the variation of E_{b1s} and E_{b2p} with the dielectric constant can be utilized as a tool for finding out the correct dielectric constant of the dot material by measuring the 1s or 2p state binding energy for a fixed dot radius and a fixed impurity position.

  7. Ab initio study of high dielectric constant oxide-perovskites: perspective for miniaturization technology

    NASA Astrophysics Data System (ADS)

    Erum, Nazia; Azhar Iqbal, Muhammad

    2017-02-01

    A new potential approximation known as modified Becke–Johnson (mBJ) based on density functional theory method is applied to compute electronic and optical properties of BaPaO3 and BaUO3 compounds. Type of chemical bonding is analyzed with the help of variations in electron density difference distribution that is induced due to changes of second cation. Results reveal (Γ–Γ) direct bandgap semi-conductive nature. The band gap dependent optical properties such as complex dielectric function ε(ω), optical conductivity σ(ω), refractive index n(ω), reflectivity R(ω), and effective number of electrons (n eff) via sum rules are reported for the first time. Prominent variation of optical responses suggests that BaPaO3 and BaUO3 are applicant materials for micro as well as nano-electronic devices.

  8. A Time-Domain Reflectometry Method with Variable Needle Pulse Width for Measuring the Dielectric Properties of Materials

    PubMed Central

    Wilczek, Andrzej; Szypłowska, Agnieszka; Kafarski, Marcin; Skierucha, Wojciech

    2016-01-01

    Time-domain reflectometry (TDR) methods used for measuring the dielectric properties of materials mostly utilize step or needle electrical pulses of constant amplitudes and shapes. Our novel approach enables determining the dielectric relaxation time of a sample using the analysis of the amplitudes of reflected pulses of two widths, in addition to bulk dielectric permittivity and electrical conductivity commonly obtained by the TDR technique. The method was developed for various values of electrical conductivity and relaxation time using numerical simulations of a five-rod probe placed in a material with complex dielectric permittivity described by the Debye model with an added electrical conductivity term. The characterization of amplitudes of two pulses of selected widths was done with regard to the dielectric parameters of simulated materials. The required probe parameters were obtained solely from numerical simulations. Verification was performed for the probe placed in aqueous KCl solutions with 14 different electrical conductivity values. The determined relaxation time remained roughly constant and independent of electrical conductivity. The obtained electrical conductivity agreed with the reference values. Our results indicate that the relaxation time, dielectric permittivity and electrical conductivity of the tested solutions can be simultaneously determined using a simple analysis of the amplitude and reflection time of two needle pulses of different widths. PMID:26861318

  9. Optical constants, dispersion energy parameters and dielectric properties of ultra-smooth nanocrystalline BiVO4 thin films prepared by rf-magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Sarkar, S.; Das, N. S.; Chattopadhyay, K. K.

    2014-07-01

    BiVO4 thin films have been prepared through radio frequency (rf) magnetron sputtering of a pre-fabricated BiVO4 target on ITO coated glass (ITO-glass) substrate and bare glass substrates. BiVO4 target material was prepared through solid-state reaction method by heating Bi2O3 and V2O5 mixture at 800 °C for 8 h. The films were characterized by X-ray diffraction, UV-Vis spectroscopy, LCR meter, field emission scanning electron microscopy, transmission electron microscopy and atomic force microscopy. BiVO4 thin films deposited on the ITO-glass substrate are much smoother compared to the thin films prepared on bare glass substrate. The rms surface roughness calculated from the AFM images comes out to be 0.74 nm and 4.2 nm for the films deposited on the ITO-glass substrate and bare glass substrate for the deposition time 150 min respectively. Optical constants and energy dispersion parameters of these extra-smooth BiVO4 thin films have been investigated in detail. Dielectric properties of the BiVO4 thin films on ITO-glass substrate were also investigated. The frequency dependence of dielectric constant of the BiVO4 thin films has been measured in the frequency range from 20 Hz to 2 MHz. It was found that the dielectric constant increased from 145 to 343 at 20 Hz as the film thickness increased from 90 nm to 145 nm (deposition time increased from 60 min to 150 min). It shows higher dielectric constant compared to the literature value of BiVO4.

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

    NASA Astrophysics Data System (ADS)

    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

  11. Calculation of polarization and bound charge density inside a dielectric material in triboelectric nanogenerators: Analytical and numerical study

    NASA Astrophysics Data System (ADS)

    Kim, SeongMin; Ha, Jaewook; Kim, Jin-Baek

    2016-11-01

    We analytically calculated polarization and bound charge density inside the dielectric material in metal-to-dielectric-mode triboelectric nanogenerators (TENG) where the transferred charges are collected on the bottom metal via electrostatic induction from the triboelectric charges that are generated by frictional contact. This bound charge density is associated with the surface density of states (DOS), overline{Ns(E)}. Two cases are considered here: i) for overline{Ns(E)} ≫ 1, it is calculated that the bound charge density is proportional to the dielectric constant and the work function difference between the two materials, but inversely proportional to the thickness of the dielectric material (ɛ0(ɛ2-1) (E0-W)/e \\cdot d2); ii) for overline{Ns(E)} ≪ 1 with constant overline{Ns(E)}, the bound charge density is mostly proportional to the work function difference between the materials, and inversely proportional to the thickness of the dielectric material ((ɛ2-1)x/d_{2+\\varepsilon2\\cdot x} \\cdot Ns(E)\\cdot e\\cdot (E0-W)).

  12. Density fluctuations and dielectric constant of water in low and high density liquid states

    NASA Astrophysics Data System (ADS)

    Lascaris, Erik; Zhang, Cui; Galli, Giulia A.; Franzese, Giancarlo; Stanley, H. Eugene

    2012-02-01

    The hypothesis of a liquid-liquid critical point (LLCP) in the phase diagram of water, though first published many years ago, still remains the subject of a heated debate. According to this hypothesis there exists a critical point near T 244 K, and P 215 MPa, located at the end of a coexistence line between a high density liquid (HDL) and a low density liquid state (LDL). The LLCP lies below the homogenous nucleation temperature of water and it has so far remained inaccessible to experiments. We study a model of water exhibiting a liquid-liquid phase transition (that is a liquid interacting through the ST2 potential) and investigate the properties of dipolar fluctuations as a function of density, in the HDL and LDL. We find an interesting correlation between the macroscopic dielectric constants and the densities of the two liquids in the vicinity of the critical point, and we discuss possible implications for measurements close to the region where the LLCP may be located.

  13. Extraordinary high dielectric constant, electrical and magnetic properties of ferrite nanoparticles at room temperature

    NASA Astrophysics Data System (ADS)

    Batoo, Khalid Mujasam; Mir, Feroz Ahmed; Abd El-sadek, M.-S.; Shahabuddin, Md.; Ahmed, Niyaz

    2013-11-01

    Nanoparticles of spinel ferrites of basic composition Ni1- x Co x Fe2O4 (0.0 ≤ x ≤ 0.05) were synthesized through modified co-precipitation method, and were characterized for structural, transport electrical and magnetic properties using XRD, HRTEM, FTIR, LCR meter and VSM techniques, respectively. XRD analysis showed that all the samples are single-phase cubic spinel in structure. The average crystallite sizes of the nanoparticles were found between 30 nm to 45 nm. Real and imaginary parts of the impedance ( Z' and Z″) suggested coexistence of two relaxation regimes: one was introduced by electrode polarization, while the other was attributed to the coeffect of grain and grain boundary effects. The dielectric constant of the samples was found very high, which showed non-Debye relaxation phenomena, while conductivity of the samples exhibited a two-segment behavior with frequency. The room temperature M-H curves suggested that the samples exhibit supermagnetism, and the saturation magnetization increases with increasing Co2+ ion substitution.

  14. Giant dielectric constant and resistance-pressure sensitivity in carbon nanotubes/rubber nanocomposites with low percolation threshold

    NASA Astrophysics Data System (ADS)

    Jiang, Mei-Juan; Dang, Zhi-Min; Xu, Hai-Ping

    2007-01-01

    Nanocomposites consisting of methylvinyl silicone rubber (VMQ) with excellent elasticity as polymer matrix and multiwall carbon nanotube (MWNT) with large slenderness ratio and high conductivity as filler were fabricated by a solution method and subsequently hot pressing technology. Studies on dielectric property and resistance-pressure sensitivity of the MWNT/VMQ composites showed that there was a giant dielectric constant and significant resistance-pressure sensitivity as the concentration of MWNT was near a low percolation threshold, fc≈0.012. After the composite applied an enough pressure for long time, the resistance-pressure sensitivity still shows an excellent reproducibility due to the good dispersion and low loading of MWNT.

  15. Characterizing Dielectric Materials using Monostatic Transmission- and Reflection-Ellipsometry

    NASA Astrophysics Data System (ADS)

    Barowski, Jan; Rolfes, Ilona

    2017-03-01

    The characterization of dielectric materials at microwave frequencies can be done by various measurement principles. Free space methods are a commonly used approach if the material under test (MUT) has to be characterized in-situ or in a non-destructive manner. Since the transmission and reflection parameters of a finite sized dielectric slab typically depend on its thickness, accurate knowledge about this parameter is of high importance. The ellipsometric approach presented in this paper eliminates the thickness dependence and thus allows to reduce a major source of error. This is achieved by performing four measurements. These measure the transmission and reflection factors of the MUT in both polarizations at an incident angle of 45°. The high stability of the measurement allows a simple monostatic setup utilizing a single antenna. The measurements in this paper are performed using Polytetrafluoroethylene (PTFE) and Polyvinylchloride (PVC) blocks in the frequency range from 22 GHz to 26 GHz.

  16. Dielectric elastomer for stretchable sensors: influence of the design and material properties

    NASA Astrophysics Data System (ADS)

    Jean-Mistral, C.; Iglesias, S.; Pruvost, S.; Duchet-Rumeau, J.; Chesné, S.

    2016-04-01

    Dielectric elastomers exhibit extended capabilities as flexible sensors for the detection of load distributions, pressure or huge deformations. Tracking the human movements of the fingers or the arms could be useful for the reconstruction of sporting gesture, or to control a human-like robot. Proposing new measurements methods are addressed in a number of publications leading to improving the sensitivity and accuracy of the sensing method. Generally, the associated modelling remains simple (RC or RC transmission line). The material parameters are considered constant or having a negligible effect which can lead to serious reduction of accuracy. Comparisons between measurements and modelling require care and skill, and could be tricky. Thus, we propose here a comprehensive modelling, taking into account the influence of the material properties on the performances of the dielectric elastomer sensor (DES). Various parameters influencing the characteristics of the sensors have been identified: dielectric constant, hyper-elasticity. The variations of these parameters as a function of the strain impact the linearity and sensitivity of the sensor of few percent. The sensitivity of the DES is also evaluated changing geometrical parameters (initial thickness) and its design (rectangular and dog-bone shapes). We discuss the impact of the shape regarding stress. Finally, DES including a silicone elastomer sandwiched between two high conductive stretchable electrodes, were manufactured and investigated. Classic and reliable LCR measurements are detailed. Experimental results validate our numerical model of large strain sensor (>50%).

  17. Procedures for determining MATMOD-4V material constants

    SciTech Connect

    Lowe, T.C.

    1993-11-01

    The MATMOD-4V constitutive relations were developed from the original MATMOD model to extend the range of nonelastic deformation behaviors represented to include transient phenomena such as strain softening. Improvements in MATMOD-4V increased the number of independent material constants and the difficulty in determining their values. Though the constitutive relations are conceptually simple, their form and procedures for obtaining their constants can be complex. This paper reviews in detail the experiments, numerical procedures, and assumptions that have been used to determine a complete set of MATMOD-4V constants for high purity aluminum.

  18. Radiation induced conductivity in space dielectric materials

    SciTech Connect

    Hanna, R.; Paulmier, T. Belhaj, M.; Dirassen, B.; Molinie, P.; Payan, D.; Balcon, N.

    2014-01-21

    The radiation-induced conductivity of some polymers was described mainly in literature by a competition between ionization, trapping/detrapping, and recombination processes or by radiation assisted ageing mechanisms. Our aim is to revise the effect of the aforementioned mechanisms on the complex evolution of Teflon{sup ®} FEP under space representative ionizing radiation. Through the definition of a new experimental protocol, revealing the effect of radiation dose and relaxation time, we have been able to demonstrate that the trapping/recombination model devised in this study agrees correctly with the observed experimental phenomenology at qualitative level and allows describing very well the evolution of radiation induced conductivity with irradiation time (or received radiation dose). According to this model, the complex behavior observed on Teflon{sup ®} FEP may be basically ascribed to the competition between electron/hole pairs generation and recombination: electrons are deeply trapped and act as recombination centers for free holes. Relaxation effects have been characterized through successive irradiations steps and have been again well described with the defined model at qualitative level: recombination centers created by the irradiation induce long term alteration on the electric properties, especially the effective bulk conductivity. One-month relaxation does not allow a complete recovery of the material initial charging behavior.

  19. Experimental study on the dielectric properties of polyacrylate dielectric elastomer

    NASA Astrophysics Data System (ADS)

    Qiang, Junhua; Chen, Hualing; Li, Bo

    2012-02-01

    The dielectric constant of elastomeric dielectric material is an essential physical parameter, whose value may affect the electromechanical deformation of a dielectric elastomer actuator. Since the dielectric constant is influenced by several external factors as reported before, and no certain value has been confirmed to our knowledge, in the present paper, on the basis of systematical comparison of recent past literature, we conducted extensive works on the measurement of dielectric properties of VHB films, involving five influencing factors: prestretch (both equal and unequal biaxial), electrical frequency, electrode material, stress relaxation time and temperature. Experimental results directly show that the dielectric response changes according to these factors, based on which we investigate the significance of each factor, especially the interaction of two external conditions on the dielectric constant of deformable dielectric, by presenting a physical picture of the mechanism of polarization.

  20. Pulse Power Capability Of High Energy Density Capacitors Based on a New Dielectric Material

    NASA Technical Reports Server (NTRS)

    Winsor, Paul; Scholz, Tim; Hudis, Martin; Slenes, Kirk M.

    1999-01-01

    A new dielectric composite consisting of a polymer coated onto a high-density metallized Kraft has been developed for application in high energy density pulse power capacitors. The polymer coating is custom formulated for high dielectric constant and strength with minimum dielectric losses. The composite can be wound and processed using conventional wound film capacitor manufacturing equipment. This new system has the potential to achieve 2 to 3 J/cu cm whole capacitor energy density at voltage levels above 3.0 kV, and can maintain its mechanical properties to temperatures above 150 C. The technical and manufacturing development of the composite material and fabrication into capacitors are summarized in this paper. Energy discharge testing, including capacitance and charge-discharge efficiency at normal and elevated temperatures, as well as DC life testing were performed on capacitors manufactured using this material. TPL (Albuquerque, NM) has developed the material and Aerovox (New Bedford, MA) has used the material to build and test actual capacitors. The results of the testing will focus on pulse power applications specifically those found in electro-magnetic armor and guns, high power microwave sources and defibrillators.

  1. Characterization of Full Set Material Constants and Their Temperature Dependence for Piezoelectric Materials Using Resonant Ultrasound Spectroscopy

    PubMed Central

    Tang, Liguo; Cao, Wenwu

    2016-01-01

    During the operation of high power electromechanical devices, a temperature rise is unavoidable due to mechanical and electrical losses, causing the degradation of device performance. In order to evaluate such degradations using computer simulations, full matrix material properties at elevated temperatures are needed as inputs. It is extremely difficult to measure such data for ferroelectric materials due to their strong anisotropic nature and property variation among samples of different geometries. Because the degree of depolarization is boundary condition dependent, data obtained by the IEEE (Institute of Electrical and Electronics Engineers) impedance resonance technique, which requires several samples with drastically different geometries, usually lack self-consistency. The resonant ultrasound spectroscopy (RUS) technique allows the full set material constants to be measured using only one sample, which can eliminate errors caused by sample to sample variation. A detailed RUS procedure is demonstrated here using a lead zirconate titanate (PZT-4) piezoceramic sample. In the example, the complete set of material constants was measured from room temperature to 120 °C. Measured free dielectric constants ε11T and ε33T were compared with calculated ones based on the measured full set data, and piezoelectric constants d15 and d33 were also calculated using different formulas. Excellent agreement was found in the entire range of temperatures, which confirmed the self-consistency of the data set obtained by the RUS. PMID:27168336

  2. Electrochemical impedance spectroscopy as an alternative to determine dielectric constant of potatoes at various moisture contents.

    PubMed

    Chee, Grace; Rungraeng, Natthakan; Han, Jung H; Jun, Soojin

    2014-02-01

    The dielectric (DE) properties, specifically the DE constant (ε') and loss factor (ε''), were measured for vacuum-dried and freeze-dried potato samples at a microwave frequency of 2.45 GHz over a range of different moisture contents (MCs) using a DE probe and also a 2-probe electrochemical impedance spectroscopy (EIS). Third-order polynomial models (ε' = f₁(MC); and ε'' = f₂(MC)) at room temperature were developed for regression analysis. Additionally, at various temperatures (T), biphasic 3rd-order polynomial models (ε' = f₁(MC, T); and ε'' = f₂(MC, T)) were obtained to determine ε' and ε'' as a function of MC and T using measured data. The vacuum-dried potato sample showed a good fitness of ε' and ε'' (R² = 0.95 and 0.96, respectively) to the regression model with the range of MCs from 18% to 80% (w/w), while the freeze-dried potato sample showed a good fitness of ε' and ε'' to the 1st-phase regression model with MC < 50% w/w (R² = 0.95 and 0.96, respectively) and the 2nd-phase regression model with MC > 50% w/w (R² = 0.94 to 0.96). EIS measurements were also used to obtain correlation impedances for ε' and ε'' determined by the DE probe method. The resulted regression analysis meets the demands for simple, rapid, and accurate assessment for transient values of ε' and ε'' of food products during dehydration/drying processes. The EIS method was verified to be a successful alternative to direct measurements of ε' and ε''.

  3. The effective dielectric constant of plasmas - A mean field theory built from the electromagnetic ionic T-matrix

    SciTech Connect

    Niez, Jean-Jacques

    2010-08-15

    This work aims to obtain the effective dielectric constant tensor of a warm plasma in the spirit of the derivation of a mixing law. The medium is made of non point-like ions immersed in an electron gas with usual conditions relating the various lengths which define the problem. In this paper the ion dielectric constants are taken from their RPA responses as developed in a previous paper [1]. Furthermore the treatment of the screening effects is made through a mathematical redefinition of the initial problem as proposed in Ref. [1]. Here the complete calculation of the T-matrix describing the scattering of an electromagnetic wave on an isolated ion immersed in an 'effective medium' is given. It is used for building , in the spirit of a mixing law, a self-consistent effective medium theory for the plasma dielectric tensor. We then extend the results obtained in Ref. [1] to higher orders in ion or dielectric inclusion densities. The techniques presented are generic and can be used in areas such as elasticity, thermoelasticity, and piezoelectricity.

  4. Polarimetric scattering behavior of rough dielectric materials at terahertz frequencies

    NASA Astrophysics Data System (ADS)

    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.

  5. Electromagnetic field tapering using all-dielectric gradient index materials

    PubMed Central

    Yi, Jianjia; Piau, Gérard-Pascal; de Lustrac, André; Burokur, Shah Nawaz

    2016-01-01

    The concept of transformation optics (TO) is applied to control the flow of electromagnetic fields between two sections of different dimensions through a tapering device. The broadband performance of the field taper is numerically and experimentally validated. The taper device presents a graded permittivity profile and is fabricated through three-dimensional (3D) polyjet printing technology using low-cost all-dielectric materials. Calculated and measured near-field mappings are presented in order to validate the proposed taper. A good qualitative agreement is obtained between full-wave simulations and experimental tests. Such all-dielectric taper paves the way to novel types of microwave devices that can be easily fabricated through low-cost additive manufacturing processes. PMID:27464989

  6. Electromagnetic field tapering using all-dielectric gradient index materials

    NASA Astrophysics Data System (ADS)

    Yi, Jianjia; Piau, Gérard-Pascal; de Lustrac, André; Burokur, Shah Nawaz

    2016-07-01

    The concept of transformation optics (TO) is applied to control the flow of electromagnetic fields between two sections of different dimensions through a tapering device. The broadband performance of the field taper is numerically and experimentally validated. The taper device presents a graded permittivity profile and is fabricated through three-dimensional (3D) polyjet printing technology using low-cost all-dielectric materials. Calculated and measured near-field mappings are presented in order to validate the proposed taper. A good qualitative agreement is obtained between full-wave simulations and experimental tests. Such all-dielectric taper paves the way to novel types of microwave devices that can be easily fabricated through low-cost additive manufacturing processes.

  7. Electromagnetic field tapering using all-dielectric gradient index materials.

    PubMed

    Yi, Jianjia; Piau, Gérard-Pascal; de Lustrac, André; Burokur, Shah Nawaz

    2016-07-28

    The concept of transformation optics (TO) is applied to control the flow of electromagnetic fields between two sections of different dimensions through a tapering device. The broadband performance of the field taper is numerically and experimentally validated. The taper device presents a graded permittivity profile and is fabricated through three-dimensional (3D) polyjet printing technology using low-cost all-dielectric materials. Calculated and measured near-field mappings are presented in order to validate the proposed taper. A good qualitative agreement is obtained between full-wave simulations and experimental tests. Such all-dielectric taper paves the way to novel types of microwave devices that can be easily fabricated through low-cost additive manufacturing processes.

  8. Primary thermometry from 2.5 K to 140 K applying dielectric-constant gas thermometry

    NASA Astrophysics Data System (ADS)

    Gaiser, Christof; Fellmuth, Bernd; Haft, Norbert

    2017-02-01

    Recent thermodynamic temperature measurements at PTB with dielectric-constant gas thermometry were performed up to 140 K. Particular care was taken to check for possible systematic sources of errors by repeating experiments applying two new measuring capacitors and both helium and neon as working gases. The development of a new method for determining the effective compressibility of the new capacitors as a function of temperature has decreased the uncertainty significantly. The combination of the recently obtained results with former values of thermodynamic temperature, corrected using new thermodynamic input data, has yielded a consistent dataset in the range from 2.5 K to 38 K as well as at 84 K, 120 K, 130 K, and 140 K. This dataset is in good agreement with the newest results of acoustic gas thermometry, which has quite different sources of uncertainty compared with dielectric-constant gas thermometry.

  9. Millimeter-wave dielectric properties of single-crystal ferroelectric and dielectric materials.

    PubMed

    McCloy, John S; Korolev, Konstantin A; Li, Zijing; Afsar, Mohammed N; Sundaram, Shanmugavelayutham K

    2011-01-01

    Transmittance measurements on various single crystal ferroelectric and dielectric materials, BaTiO(3), SrTiO(3), LiNbO(3), LiTaO(3), (PbMg(1/3)Nb(2/3)O(3))0.73-(PbTiO(3))0.27, LaAlO(3), and Bi(4)Ge(3)O(12), over a broad millimeter-wave (MMW) frequency range have been performed. Frequency dependence of the complex dielectric permittivity has been measured in the MMW region using high-power sources for the first time, using a free-space, quasi-optical MMW spectrometer equipped with high-power backward wave oscillators (BWOs) as sources of coherent radiation, tunable in the range from 30 to 120 and 180 to 260 GHz. These results are compared with MMW permittivity of these materials obtained by other methods as well as to RF, microwave, and optical frequency permittivities for all the materials tested. The effects of both crystallographic orientation and quality of the surface polishing of the crystals have been examined. Uncertainties and possible sources of instrumentation and measurement errors related to the freespace MMW technique are discussed. This work demonstrates that precise MMW permittivity data can be obtained even on relatively small and thin crystals of different surface conditions and orientations using the high-power BWO-based quasioptical approach.

  10. A layered microchip conductance detector with through-layer access to detection fields and high sensitivity to dielectric constant

    NASA Astrophysics Data System (ADS)

    Suganuma, Y.; Dhirani, A.-A.

    2011-04-01

    The present study explores a novel apertured microchip conductance detector (AMCD) that is sensitive to dielectric constant. Fashioned on silicon oxide/silicon using optical microlithography, the detector has novel parallel-plate geometry with a top mesh electrode, a middle apertured insulator, and a bottom conducting electrode. This monolithic apertured architecture is planar and may be provided with a thin insulator layer enabling large capacitances, while the top mesh electrode and middle apertured-insulator enable access to regions of the capacitor where electric fields are strong. Hence, the detector is sensitive yet mechanically robust. To test its response, the AMCD was immersed in various solvents, namely water, methanol, acetonitrile, and hexanes. Its response was found to vary in proportion to the solvents' respective dielectric constants. The AMCD was also able to distinguish quantitatively the presence of various molecules in solution, including molecules with chromophores [such as acetylsalicylic acid (ASA)] in methanol and those without chrompohores [such as polyethylene glycol 200 Daltons (PEG200)] in methanol or water. The universal nature of dielectric constant and the microchip detector's sensitivity point to a wide range of potential applications.

  11. Dielectric constant and low-frequency infrared spectra for liquid water and ice Ih within the E3B model

    SciTech Connect

    Shi, L.; Ni, Y.; Drews, S. E. P.; Skinner, J. L.

    2014-08-28

    Two intrinsic difficulties in modeling condensed-phase water with conventional rigid non-polarizable water models are: reproducing the static dielectric constants for liquid water and ice Ih, and generating the peak at about 200 cm{sup −1} in the low-frequency infrared spectrum for liquid water. The primary physical reason for these failures is believed to be the missing polarization effect in these models, and consequently various sophisticated polarizable water models have been developed. However, in this work we pursue a different strategy and propose a simple empirical scheme to include the polarization effect only on the dipole surface (without modifying a model's intermolecular interaction potential). We implement this strategy for our explicit three-body (E3B) model. Our calculated static dielectric constants and low-frequency infrared spectra are in good agreement with experiment for both liquid water and ice Ih over wide temperature ranges, albeit with one fitting parameter for each phase. The success of our modeling also suggests that thermal fluctuations about local minima and the energy differences between different proton-disordered configurations play minor roles in the static dielectric constant of ice Ih. Our analysis shows that the polarization effect is important in resolving the two difficulties mentioned above and sheds some light on the origin of several features in the low-frequency infrared spectra for liquid water and ice Ih.

  12. Ionization States of Residues in OmpF and Mutants: Effects of Dielectric Constant and Interactions between Residues

    PubMed Central

    Varma, Sameer; Jakobsson, Eric

    2004-01-01

    To understand ion permeation, one must assign correct ionization states to titratable amino acid residues in protein channels. We report on the effects of physical and methodological assumptions in calculating the protonation states at neutral bulk pH of titratable residues lining the lumen of the native Escherichia coli OmpF channel, and five mutants. We systematically considered a wide range of assumed protein dielectric constants and all plausible combinations of protonation states for electrostatically interacting side chains, and three different levels of accounting for solute shielding: 1), full nonlinear Poisson-Boltzmann; 2), linearized Poisson-Boltzmann; and 3), neglect of solute shielding. For this system we found it acceptable to neglect solute shielding, a result we postulate to be generalizable to narrow lumens of other protein channels. For the large majority of residues, the protonation state at neutral bulk pH was found to be independent of the assumed dielectric constant of the protein, and unambiguously determined by the calculation; for native OmpF only Asp-127 has a protonation state that is sensitive to the assumed protein dielectric constant. Our results are significant for understanding two published experimental observations: the structure of the narrow part of the channel, and the ionic selectivity of OmpF mutants. PMID:14747308

  13. Recent Results on the Accurate Measurements of the Dielectric Constant of Seawater at 1.413GHZ

    NASA Technical Reports Server (NTRS)

    Lang, R.H.; Tarkocin, Y.; Utku, C.; Le Vine, D.M.

    2008-01-01

    Measurements of the complex. dielectric constant of seawater at 30.00 psu, 35.00 psu and 38.27 psu over the temperature range from 5 C to 3 5 at 1.413 GHz are given and compared with the Klein-Swift results. A resonant cavity technique is used. The calibration constant used in the cavity perturbation formulas is determined experimentally using methanol and ethanediol (ethylene glycol) as reference liquids. Analysis of the data shows that the measurements are accurate to better than 1.0% in almost all cases studied.

  14. Determination of plasma frequency, damping constant, and size distribution from the complex dielectric function of noble metal nanoparticles

    SciTech Connect

    Mendoza Herrera, Luis J.; Arboleda, David Muñetón; Schinca, Daniel C.; Scaffardi, Lucía B.

    2014-12-21

    This paper develops a novel method for simultaneously determining the plasma frequency ω{sub P}   and the damping constant γ{sub free} in the bulk damped oscillator Drude model, based on experimentally measured real and imaginary parts of the metal refractive index in the IR wavelength range, lifting the usual approximation that restricts frequency values to the UV-deep UV region. Our method was applied to gold, silver, and copper, improving the relative uncertainties in the final values for ω{sub p} (0.5%–1.6%) and for γ{sub free} (3%–8%), which are smaller than those reported in the literature. These small uncertainties in ω{sub p} and γ{sub free} determination yield a much better fit of the experimental complex dielectric function. For the case of nanoparticles (Nps), a series expansion of the Drude expression (which includes ω{sub p} and γ{sub free} determined using our method) enables size-dependent dielectric function to be written as the sum of three terms: the experimental bulk dielectric function plus two size corrective terms, one for free electron, and the other for bound-electron contributions. Finally, size distribution of nanometric and subnanometric gold Nps in colloidal suspension was determined through fitting its experimental optical extinction spectrum using Mie theory based on the previously determined dielectric function. Results are compared with size histogram obtained from Transmission Electron Microscopy (TEM)

  15. Optimisation of the electromagnetic matching of manganese dioxide/multi-wall carbon nanotube composites as dielectric microwave-absorbing materials

    NASA Astrophysics Data System (ADS)

    Ting, Tzu-Hao; Chiang, Chih-Chia; Lin, Po-Chuan; Lin, Chia-Huei

    2013-08-01

    An optimised composite sample was prepared using two dielectric materials manganese dioxide (MnO2) and multi-wall carbon nanotubes (MWNTs) in an epoxy-resin matrix. Structural characterisations of both the synthesised manganese dioxide (MnO2) and the multi-wall carbon nanotubes (MWNTs) were performed by using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The microwave absorption properties of dielectric composites with different weight fractions of MnO2 were investigated by measuring the complex permittivity, the complex permeability and the reflection loss in the 2-18 and 18-40 GHz microwave frequency ranges using the free space method. The complex permittivity varied with the MnO2 content, and the results show that a high concentration of fillers increased the dielectric constant. Therefore, the appropriate combination of components and experimental conditions can produce materials with specific characteristic for use as wide-band microwave absorbers.

  16. Correlation between band gap, dielectric constant, Young’s modulus and melting temperature of GaN nanocrystals and their size and shape dependences

    PubMed Central

    Lu, Haiming; Meng, Xiangkang

    2015-01-01

    With structural miniaturization down to the nanoscale, the detectable parameters of materials no longer remain constant but become tunable. For GaN nanocrystals example, the band gap increases while the dielectric constant, Young’s modulus and melting temperature decrease with decreasing the solid size. Herein, we developed the models to describe the size and shape dependences of these seemingly uncorrelated parameters for GaN nanocrystals, based on our established thermodynamic model for cohesive energy of metallic nanocrystals. Consistency between our theoretical predictions and the corresponding experimental or simulated results confirms the accuracy of the developed models and indicates the essentiality of cohesive energy in describing the effects of size and shape on the physicochemical properties of different low-dimensional systems. PMID:26582533

  17. Investigation of temperature dependent dielectric constant of a sputtered TiN thin film by spectroscopic ellipsometry

    SciTech Connect

    Tripura Sundari, S. Ramaseshan, R.; Jose, Feby; Dash, S.; Tyagi, A. K.

    2014-01-21

    The temperature dependence of optical constants of titanium nitride thin film is investigated using Spectroscopic Ellipsometry (SE) between 1.4 and 5 eV in the temperature range of 300 K to 650 K in steps of 50 K. The real and imaginary parts of the dielectric functions ε{sub 1}(E) and ε{sub 2}(E) marginally increase with increase in temperature. A Drude Lorentz dielectric analysis based on free electron and oscillator model are carried out to describe the temperature behavior. With increase in temperature, the unscreened plasma frequency and broadening marginally decreased and increased, respectively. The parameters of the Lorentz oscillator model also showed that the relaxation time decreased with temperature while the oscillator energies increased. This study shows that owing to the marginal change in the refractive index with temperature, titanium nitride can be employed for surface plasmon sensor applications even in environments where rise in temperature is imminent.

  18. Numerical Estimation of the Dependence of Dielectric Constant of BaTiO3 Thick Films on Grain-Size Distribution

    NASA Astrophysics Data System (ADS)

    Yamashita, Kimihiro; Yamazaki, Shozo; Koumoto, Kunihito; Yanagida, Hiroaki

    1981-10-01

    An exponential function of the grain size was assumed in calculating the apparent (total) dielectric constant of BaTiO3 thick films with the average grain diameter known. The function was tested and estimated experimentally, for cases where the grain sizes were calculated using the following methods; the two-dimensional diameter analysis, the Schwartz-Saltykov method and Oel’s method for converting a two-dimensional grain distribution to a spacial grain sizedistribution. Using the present assumed function and the extended logarithmic mixing rule to combine the dielectric constants of individual grains, the grain-size distribution-dependence of the dielectric constant was successfully simulated. From the simulated results it was concluded that the dielectric constants of coarse grains of thick films increase with increase of grain size in the range from room temperature up to 135°C.

  19. Spiral configuration of electrodes and dielectric material for sensing an environmental property

    NASA Technical Reports Server (NTRS)

    Laue, Eric G. (Inventor); Stephens, James B. (Inventor)

    1989-01-01

    A reliable moisture-indicating capactive sensor is provided with wire electrodes at least one of which includes a coating of moisture-absorbing dielectric material by spirally twisting the wire electrodes about each other, thereby establishing a pair of electrodes in contact with opposite surfaces of a layer of dielectric material, and assuring consistent contact of each electrode with the dielectric material despite changes in environmental conditions.

  20. Pulsed picosecond and nanosecond discharge development in liquids with various dielectric permittivity constants

    NASA Astrophysics Data System (ADS)

    Starikovskiy, Andrey

    2016-09-01

    The dynamics of pulsed picosecond and nanosecond discharge development in liquid water, ethanol and hexane were investigated experimentally. It is shown that the dynamics of discharge formation fundamentally differ between liquids with low and high dielectric permittivity coefficients. The difference in the nanosecond discharge development in liquid dielectrics may be explained by the formation of micro-discontinuities in the media during the electrostriction compression/rarefaction stage in liquids with high dielectric permittivity. Three possible mechanisms for the propagation of discharge in liquids play a different role depending on the pulse duration. The first is the formation of low density channels in liquid. In the second case the electrostatic forces support the expansion of nanoscale voids behind the front of the ionization wave; in the wave front the extreme electric field provides a strong negative pressure in the dielectric fluid due to the presence of electrostriction forces, forming the initial micro-voids in the continuous medium. Finally, in the third case, when a picosecond electric pulse is utilized, the ionization in the liquid phase occurs as a result of direct electron impact without undergoing a phase transition.

  1. Effect of species structure and dielectric constant on C-band forest backscatter

    NASA Technical Reports Server (NTRS)

    Lang, R. H.; Landry, R.; Kilic, O.; Chauhan, N.; Khadr, N.; Leckie, D.

    1993-01-01

    A joint experiment between Canadian and USA research teams was conducted early in Oct. 1992 to determine the effect of species structure and dielectric variations on forest backscatter. Two stands, one red pine and one jack pine, in the Petawawa National Forestry Institute (PNFI) were utilized for the experiment. Extensive tree architecture measurements had been taken by the Canada Centre for Remote Sensing (CCRS) several months earlier by employing a Total Station surveying instrument which provides detailed information on branch structure. A second part of the experiment consisted of cutting down several trees and using dielectric probes to measure branch and needle permittivity values at both sites. The dielectric and the tree geometry data were used in the George Washington University (GWU) Vegetation Model to determine the C band backscattering coefficients of the individual stands for VV polarization. The model results show that backscatter at C band comes mainly from the needles and small branches and the upper portion of the trunks acts only as an attenuator. A discussion of variation of backscatter with specie structure and how dielectric variations in needles for both species may affect the total backscatter returns is provided.

  2. Millimeter-Wave Dielectric Properties of Single Crystal Ferroelectric and Dielectric Materials

    SciTech Connect

    McCloy, John S.; Korolev, Konstantin A.; Li, Zijing; Afsar, Mohammed N.; Sundaram, S. K.

    2011-01-03

    Transmittance measurements on various single crystal ferroelectric materials over a broad millimeter-wave frequency range have been performed. Frequency dependence of the complex dielectric permittivity has been determined in the millimeter wave region for the first time. The measurements have been employed using a free-space quasi-optical millimeter-wave spectrometer equipped with a set of high power backward wave oscillators (BWOs) as sources of coherent radiation, tunable in the range from 30 - 120 GHz. The uncertainties and possible sources of instrumentation and measurement errors related to the free-space millimeter-wave technique are discussed. This work has demonstrated that precise MMW permittivities can be obtained even on small thin crystals using the BWO quasi-optical approach.

  3. Tuning of colossal dielectric constant in gold-polypyrrole composite nanotubes using in-situ x-ray diffraction techniques

    SciTech Connect

    Sarma, Abhisakh; Sanyal, Milan K.

    2014-09-15

    In-situ x-ray diffraction technique has been used to study the growth process of gold incorporated polypyrrole nanotubes that exhibit colossal dielectric constant due to existence of quasi-one-dimensional charge density wave state. These composite nanotubes were formed within nanopores of a polycarbonate membrane by flowing pyrrole monomer from one side and mixture of ferric chloride and chloroauric acid from other side in a sample cell that allows collection of x-ray data during the reaction. The size of the gold nanoparticle embedded in the walls of the nanotubes was found to be dependent on chloroauric acid concentration for nanowires having diameter more than 100 nm. For lower diameter nanotubes the nanoparticle size become independent of chloroauric acid concentration and depends on the diameter of nanotubes only. The result of this study also shows that for 50 nm gold-polypyrrole composite nanotubes obtained with 5.3 mM chloroauric acid gives colossal dielectric constant of about 10{sup 7}. This value remain almost constant over a frequency range from 1Hz to 10{sup 6} Hz even at 80 K temperature.

  4. Analysis of Interface Charge Densities for High-k Dielectric Materials based Metal Oxide Semiconductor Devices

    NASA Astrophysics Data System (ADS)

    Maity, N. P.; Thakur, R. R.; Maity, Reshmi; Thapa, R. K.; Baishya, S.

    2016-10-01

    In this paper, the interface charge densities (Dit) are studied and analyzed for ultra thin dielectric metal oxide semiconductor (MOS) devices using different high-k dielectric materials such as Al2O3, ZrO2 and HfO2. The Dit have been calculated by a new approach using conductance method and it indicates that by reducing the thickness of the oxide, the Dit increases and similar increase is also found by replacing SiO2 with high-k. For the same oxide thickness, SiO2 has the lowest Dit and found to be the order of 1011cm-2eV-1. Linear increase in Dit has been observed as the dielectric constant of the oxide increases. The Dit is found to be in good agreement with published fabrication results at p-type doping level of 1×1017cm-3. Numerical calculations and solutions are performed by MATLAB and device simulation is done by ATLAS.

  5. The effect of concentration- and temperature-dependent dielectric constant on the activity coefficient of NaCl electrolyte solutions

    SciTech Connect

    Valiskó, Mónika; Boda, Dezső

    2014-06-21

    Our implicit-solvent model for the estimation of the excess chemical potential (or, equivalently, the activity coefficient) of electrolytes is based on using a dielectric constant that depends on the thermodynamic state, namely, the temperature and concentration of the electrolyte, ε(c, T). As a consequence, the excess chemical potential is split into two terms corresponding to ion-ion (II) and ion-water (IW) interactions. The II term is obtained from computer simulation using the Primitive Model of electrolytes, while the IW term is estimated from the Born treatment. In our previous work [J. Vincze, M. Valiskó, and D. Boda, “The nonmonotonic concentration dependence of the mean activity coefficient of electrolytes is a result of a balance between solvation and ion-ion correlations,” J. Chem. Phys. 133, 154507 (2010)], we showed that the nonmonotonic concentration dependence of the activity coefficient can be reproduced qualitatively with this II+IW model without using any adjustable parameter. The Pauling radii were used in the calculation of the II term, while experimental solvation free energies were used in the calculation of the IW term. In this work, we analyze the effect of the parameters (dielectric constant, ionic radii, solvation free energy) on the concentration and temperature dependence of the mean activity coefficient of NaCl. We conclude that the II+IW model can explain the experimental behavior using a concentration-dependent dielectric constant and that we do not need the artificial concept of “solvated ionic radius” assumed by earlier studies.

  6. Correction to the Clausius-Mosotti equation: The dielectric constant of nonpolar fluids from Monte Carlo simulations.

    PubMed

    Valiskó, Mónika; Boda, Dezso

    2009-10-28

    We examine the dielectric constant of nonpolar fluids by direct Monte Carlo simulations on the basis of the polarizable hard sphere (PHS) model, where the spheres carry molecular polarizabilities. Point dipoles are induced in the spheres partly by an external electric field and partly by other molecules. It has been known that the Clausius-Mosotti equation needs a correction due to mutual polarization between molecules. We reproduce the qualitative behavior found in experiments: the correction increases with increasing density, reaches a maximum, and decreases at high densities. We show that the classic theory of Kirkwood and Yvon is quantitatively correct for the PHS model.

  7. Dielectric Relaxation of Materials that Form Ultra-Stable Glasses

    NASA Astrophysics Data System (ADS)

    Richert, Ranko

    2015-03-01

    Physical vapor deposition of glass forming materials onto substrates at temperatures around 0.8 Tg produces glasses of high density and low enthalpy. Using interdigitated electrode cells as substrates, such stable glasses can be studied by dielectric spectroscopy in situ. This technique is applied to monitor the dynamics of stable films upon their conversion to the ordinary supercooled liquid state. The dielectric loss during transformation indicates that the softening proceeds by a growth front mechanism and generates the ordinary liquid state without forming intermediates. The same technique is also used to assess the residual dynamics of the stable glassy state. We observe that processes such as the Johari-Goldstein beta relaxation are strongly suppressed in this stable state, consistent with the relatively low fictive temperature of these glassy states. coauthors: Hai-Bin Yu, Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85278; Michael Tylinski, and Mark D. Ediger, Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706.

  8. Layered CU-based electrode for high-dielectric constant oxide thin film-based devices

    DOEpatents

    Auciello, Orlando

    2010-05-11

    A layered device including a substrate; an adhering layer thereon. An electrical conducting layer such as copper is deposited on the adhering layer and then a barrier layer of an amorphous oxide of TiAl followed by a high dielectric layer are deposited to form one or more of an electrical device such as a capacitor or a transistor or MEMS and/or a magnetic device.

  9. Effect of Solvent Dielectric Constant on the Formation of Large Flat Bilayer Stacks in a Lecithin/Hexadecanol Hydrogel.

    PubMed

    Nakagawa, Yasuharu; Nakazawa, Hiromitsu; Kato, Satoru

    2016-07-12

    We investigated the effect of dielectric properties of the aqueous medium on the novel type of hydrogel composed of a crude lecithin mixture (PC70) and hexadecanol (HD), in which charged sheet-like bilayers are kept far apart due to interbilayer repulsive interaction. We used dipropylene glycol (DPG) as a modifier of the dielectric properties and examined its effect on the hydrogel by synchrotron X-ray diffraction, differential scanning calorimetry (DSC), polarized optical microscopy, and freeze-fracture electron microscopy. We found that at a DPG weight fraction in the aqueous medium WDPG ≈ 0.4, the bilayer organization is transformed into unusually large flat bilayer stacks with a regular lamellar spacing of 6.25 nm and consequently disintegration of the hydrogel takes place. Semiquantitative calculation of the interbilayer interaction energy based on the Deyaguin-Landau-Verwey-Overbeek (DLVO) theory suggested that the reduction of the aqueous medium dielectric constant ε by DPG may lower the energy barrier preventing flat bilayers from coming closer together. We inferred that the size of the bilayer sheet increases because the reduction of ε promotes protonation of acidic lipids that work as edge-capping molecules.

  10. Discharge characteristics of dielectric materials examined in mono-, dual-, and spectral energy electron charging environments

    NASA Technical Reports Server (NTRS)

    Coakley, P.; Treadway, M.; Wild, N.; Kitterer, B.

    1985-01-01

    The effects of midenergy electrons on the charge and discharge characteristics of spacecraft dielectric materials and the data base from which basic discharge models can be formulated is expanded. Thin dielectric materials were exposed to low, mid combined low and mid, and spectral energy electron environments. Three important results are presented: (1) it determined electron environments that lead to dielectric discharges at potentials less negative than -5 kV; (2) two types of discharges were identified that dominate the kinds of discharges seen; and (3) it is shown that, for the thin dielectric materials tested, the worst-case discharges observed in the various environments are similar.

  11. An overview of laminate materials with enhanced dielectric properties

    NASA Astrophysics Data System (ADS)

    Mumby, Stephen J.

    1989-03-01

    This report focuses on laminate materials (resins and reinforcements) having potential applications in the manufacture of multi-layer printed wiring boards (PWBs) that are required to efficiently transmit high-speed digital pulses. It is intended to be a primer and a reference for selection of candidate materials for such high-performance PWBs. Included are dielectric and physical properties, and where available chemical composition and/or structure, commercial availability, compatibility with typical PWB processing schemes and approximate relative cost. Recommendations are made as to the most viable candidate materials for this type of PWB application, based on a comparison of electrical and physical properties together with processing and cost considerations. The cyanate ester resin system appears promising. Such a resin may be reinforced with regular E-glass, or the more newly available S-glass, to produce a laminate useful for intermediate performance applications. For more demanding applications the E-glass will have to be replaced by a material of much lower relative permittivity. The expanded-PTFE reinforced laminates from W. L. Gore appear to be a good choice for these applications. The processing of the Gore materials can be expected to deviate from that used with FR-4 type materials, but is likely to be less problematic than laminates comprised of a fluorinated resin. Processing is a key obstacle to the implementation of any of the new materials herein. If implementation is to be successful, programs must be established to develop and optimize processing procedures. Cost will remain an important issue. However, the higher cost of the new materials may be justified in high-end products by the performance they deliver.

  12. Dielectric Characterization of PCL-Based Thermoplastic Materials for Microwave Diagnostic and Therapeutic Applications

    PubMed Central

    Aguilar, Suzette M.; Shea, Jacob D.; Al-Joumayly, Mudar A.; Van Veen, Barry D.; Behdad, Nader; Hagness, Susan C.

    2011-01-01

    We propose the use of a polycaprolactone (PCL)-based thermoplastic mesh as a tissue-immobilization interface for microwave imaging and microwave hyperthermia treatment. An investigation of the dielectric properties of two PCL-based thermoplastic materials in the frequency range of 0.5 – 3.5 GHz is presented. The frequency-dependent dielectric constant and effective conductivity of the PCL-based thermoplastics are characterized using measurements of microstrip transmission lines fabricated on substrates comprised of the thermoplastic meshes. We also examine the impact of the presence of a PCL-based thermoplastic mesh on microwave breast imaging. We use a numerical test bed comprised of a previously reported three-dimensional anatomically realistic breast phantom and a multi-frequency microwave inverse scattering algorithm. We demonstrate that the PCL-based thermoplastic material and the assumed biocompatible medium of vegetable oil are sufficiently well matched such that the PCL layer may be neglected by the imaging solution without sacrificing imaging quality. Our results suggest that PCL-based thermoplastics are promising materials as tissue immobilization structures for microwave diagnostic and therapeutic applications. PMID:21622068

  13. Structure, Ferromagnetic, Dielectric and Electronic Features of the LaBiFe2O6 Material

    NASA Astrophysics Data System (ADS)

    Cuervo Farfán, J. A.; Aljure García, D. M.; Cardona, R.; Arbey Rodríguez, J.; Landínez Téllez, D. A.; Roa-Rojas, J.

    2017-03-01

    In this paper, the synthesis and study of the structural, morphological, electrical, magnetic and electronic properties of the LaBiFe2O6 novel material are reported. The material was produced using the standard ceramic method. The Rietveld analysis of experimental data of X-ray diffraction showed that it synthesizes in an orthorhombic perovskite structure ( Pnma space group, # 62). Two types of grain, micro and sub-micrometric, with the LaBiFe2O6 stoichiometry were identified by scanning electron microscopy and X-ray dispersive spectroscopy. Results of electrical polarization and dielectric constant reveal the occurrence of hysteretic loops of polarization with evidences of dielectric loss. At room temperature, the material is ferromagnetic and exhibits an anomaly at T = 258 K, which is attributed to anisotropy effects. Results of diffuse reflectance suggest a semiconductor feature with energy gap Eg=2.17 eV, which is in agreement with calculations of band structure and density of states for one spin orientation, while for the other spin configuration from the calculations a conductor behavior is expected.

  14. Dielectric characterization of PCL-based thermoplastic materials for microwave diagnostic and therapeutic applications.

    PubMed

    Aguilar, Suzette M; Shea, Jacob D; Al-Joumayly, Mudar A; Van Veen, Barry D; Behdad, Nader; Hagness, Susan C

    2012-03-01

    We propose the use of a polycaprolactone (PCL)-based thermoplastic mesh as a tissue-immobilization interface for microwave imaging and microwave hyperthermia treatment. An investigation of the dielectric properties of two PCL-based thermoplastic materials in the frequency range of 0.5-3.5 GHz is presented. The frequency-dependent dielectric constant and effective conductivity of the PCL-based thermoplastics are characterized using measurements of microstrip transmission lines fabricated on substrates comprised of the thermoplastic meshes. We also examine the impact of the presence of a PCL-based thermoplastic mesh on microwave breast imaging. We use a numerical test bed comprised of a previously reported 3-D anatomically realistic breast phantom and a multi-frequency microwave inverse scattering algorithm. We demonstrate that the PCL-based thermoplastic material and the assumed biocompatible medium of vegetable oil are sufficiently well matched such that the PCL layer may be neglected by the imaging solution without sacrificing imaging quality. Our results suggest that PCL-based thermoplastics are promising materials as tissue immobilization structures for microwave diagnostic and therapeutic applications.

  15. Pulsewidth-dependent damage measurements of dielectric materials

    SciTech Connect

    Stuart, B.C.; Herman, S.; Shore, B.W.; Perry, M.D.

    1994-06-01

    The application of chirped pulse amplification to short-pulse lasers has led to a dramatic increase in the number of high-power, sub-picosecond laser systems. Accordingly, knowledge of the short-pulse damage thresholds of optical components and the scaling of the damage thresholds with pulsewidth has become increasingly important. The development of high energy, (e.g, kilojoule class) short-pulse lasers is contingent on the ability to produce optical components capable of withstanding high fluence nanosecond and femtosecond pulses. In this paper, the authors report on their measurements of the front-surface damage threshold of many different dielectric materials including widows, multilayer mirrors, and diffraction gratings over the pulsewidth range of 0.1 to 3,000 ps.

  16. Measurement of pressures up to 7 MPa applying pressure balances for dielectric-constant gas thermometry

    NASA Astrophysics Data System (ADS)

    Zandt, Thorsten; Sabuga, Wladimir; Gaiser, Christof; Fellmuth, Bernd

    2015-10-01

    For the determination of the Boltzmann constant by dielectric-constant gas thermometry, the uncertainty of pressure measurements in helium up to 7 MPa has been decreased compared with previous achievements (Sabuga 2011 PTB-Mitt. 121 247-55). This was possible by performing comprehensive cross-float experiments with a system of six special pressure balances and the synchronization of their effective areas. It is now possible to measure a helium pressure of 7 MPa with a relative standard uncertainty of 1.0 ppm applying a 2 cm2 piston-cylinder unit, the calibration of which is traceable to the SI base units.

  17. Impact of reductive N2/H2 plasma on porous low-dielectric constant SiCOH thin films

    NASA Astrophysics Data System (ADS)

    Cui, Hao; Carter, Richard J.; Moore, Darren L.; Peng, Hua-Gen; Gidley, David W.; Burke, Peter A.

    2005-06-01

    Porous low-dielectric constant (low-κ) SiCOH thin films deposited using a plasma-enhanced chemical-vapor deposition have been comprehensively characterized before and after exposure to a reactive-ion-etch-type plasma of N2 and H2 chemistry. The low-κ film studied in this work is a carbon-doped silicon oxide film with a dielectric constant (κ) of 2.5. Studies show that a top dense layer is formed as a result of significant surface film densification after exposure to N2/H2 plasma while the underlying bulk layer remains largely unchanged. The top dense layer is found to seal the porous bulk SiCOH film. SiCOH films experienced significant thickness reduction, κ increase, and leakage current degradation after plasma exposure, accompanied by density increase, pore collapse, carbon depletion, and moisture content increase in the top dense layer. Both film densification and removal processes during N2/H2 plasma treatment were found to play important roles in the thickness reduction and κ increase of this porous low-κ SiCOH film. A model based upon mutually limiting film densification and removal processes is proposed for the continuous thickness reduction during plasma exposure. A combination of surface film densification, thickness ratio increase of top dense layer to bulk layer, and moisture content increase results in the increase in κ value of this SiCOH film.

  18. The microwave properties of the jovian clouds: A new model for the complex dielectric constant of aqueous ammonia

    NASA Astrophysics Data System (ADS)

    Duong, Danny; Steffes, Paul G.; Noorizadeh, Sahand

    2014-02-01

    A new model for the complex dielectric constant of aqueous ammonia (NH4OH) under conditions characteristic of the jovian clouds has been developed. The new model is based on laboratory measurements in the frequency range between 2 and 8.5 GHz for ammonia concentrations of 0-8.5% by volume and temperatures between 274 and 297 K. The new model is based on the Meissner and Wentz (Meissner, T., Wentz, F.J. [2004]. IEEE Trans. Geosci. Rem. Sens. 42, 1836-1849) model of the complex dielectric constant of pure water but contains corrections for dissolved ammonia. Assuming Raleigh scattering, these measurements are applied to a cloud attenuation model to calculate the range of opacity of the jovian aqueous ammonia clouds. These measurements will improve our understanding of the data collected by the Juno microwave radiometer (MWR) by better characterizing the absorption properties of the aqueous ammonia present in the jovian atmosphere. The new model has been validated for temperatures up to 313 K, and may be consistently used for the expected conditions for aqueous clouds in all of the outer planets. The model fits 60.26% of all laboratory measurements within 2-sigma uncertainty. Descriptions of the experimental setups, uncertainties associated with the laboratory measurements, the model fitting process, the new model, and its application to approximating jovian cloud opacity are provided.

  19. Integration of high-dielectric constant Ta{sub 2}O{sub 5} oxides on diamond for power devices

    SciTech Connect

    Cheng Shaoheng; Sang Liwen; Liao Meiyong; Imura, Masataka; Liu Jiangwei; Li Hongdong; Koide, Yasuo

    2012-12-03

    The authors report on the direct integration of high-dielectric constant (high-k) Ta{sub 2}O{sub 5} films on p-type single crystal diamond for high-power electronic devices. Crystallized hexagonal phase {delta}-Ta{sub 2}O{sub 5} film is achieved on diamond by annealing the amorphous Ta{sub 2}O{sub 5} film deposited by a sputter-deposition technique. The electrical properties of the Ta{sub 2}O{sub 5} thin films are investigated by fabricating metal-insulator-semiconductor (MIS) diodes. The leakage current of the MIS diode is as low as 10{sup -8} A/cm{sup 2} for the as-deposited amorphous Ta{sub 2}O{sub 5} film and 10{sup -2} A/cm{sup 2} for the crystallized film, which is 10{sup 8} and 10{sup 2} times lower than that of the Schottky diode at a forward bias of -3 V, respectively. The dielectric constant of the amorphous Ta{sub 2}O{sub 5} films is measured to be 16 and increases to 29 after annealing at 800 Degree-Sign C. Different current leakage mechanisms and charge trapping behaviors are proposed for the amorphous and crystallized Ta{sub 2}O{sub 5} thin films.

  20. Porous AlN with a Low Dielectric Constant Synthesized Based on the Physical Vapor Transport Principle

    NASA Astrophysics Data System (ADS)

    Wang, Hua-Jie; Liu, Xue-Chao; Kong, Hai-Kuan; Xin, Jun; Gao, Pan; Shi, Er-Wei

    2016-07-01

    Porous AlN with low dielectric constant has been synthesized by the sacrificial template method based on the physical vapor transport principle. It is quite different from the traditional method that mixes the matrix with a pore-forming agent and utilizes liquid-phase sintering. The method consists of two parts. Firstly, AlN powder is placed in a graphite crucible. C/AlN composite can be formed by mixing decomposed AlN vapor and volatile carbon originated from a crucible at high temperature. Secondly, pores are formed after removing carbon from the C/AlN composite by an annealing process. The structure, morphology, porosity and properties of porous AlN are characterized. It is shown the obtained porous AlN has a thermal conductivity of 37.3 W/(m K) and a reduced dielectric constant of 5.5-6.1 (at 1 MHz). The porosity measured by a mercury porosimeter is 24.09%. It has been experimentally proved that porous AlN with a sufficiently porous structure and properties can be synthesized based on the vapor-phase principle.

  1. Inter-Comparison of SMOS and Aquarius Sea Surface Salinity: Effects of the Dielectric Constant and Vicarious Calibration

    NASA Technical Reports Server (NTRS)

    Dinnat, Emmanuel P.; Boutin, Jacqueline; Yin, Xiaobin; Le Vine, David M.

    2014-01-01

    Two spaceborne instruments share the scientific objective of mapping the global Sea Surface Salinity (SSS). ESA's Soil Moisture and Ocean Salinity (SMOS) and NASA's Aquarius use L-band (1.4 GHz) radiometry to retrieve SSS. We find that SSS retrieved by SMOS is generally lower than SSS retrieved by Aquarius, except for very cold waters where SMOS SSS is higher overall. The spatial distribution of the differences in SSS is similar to the distribution of sea surface temperature. There are several differences in the retrieval algorithm that could explain the observed SSS differences. We assess the impact of the dielectric constant model and the ancillary sea surface salinity used by both missions for calibrating the radiometers and retrieving SSS. The differences in dielectric constant model produce differences in SSS of the order of 0.3 psu and exhibit a dependence on latitude and temperature. We use comparisons with the Argo in situ data to assess the performances of the model in various regions of the globe. Finally, the differences in the ancillary sea surface salinity products used to perform the vicarious calibration of both instruments are relatively small (0.1 psu), but not negligible considering the requirements for spaceborne remote sensing of SSS.

  2. Study of Fluorine Addition Influence in the Dielectric Constant of Diamond-Like Carbon Thin Film Deposited by Reactive Sputtering

    NASA Astrophysics Data System (ADS)

    Trippe, S. C.; Mansano, R. D.

    The hydrogenated amorphous carbon films (a-C:H) or DLC (Diamond-Like Carbon) films are well known for exhibiting high electrical resistivity, low dielectric constant, high mechanical hardness, low friction coefficient, low superficial roughness and also for being inert. In this paper, we produced fluorinated DLC films (a-C:F), and studied the effect of adding CF4 on the above-mentioned properties of DLC films. These films were produced by a reactive RF magnetron sputtering system using a target of pure carbon in stable graphite allotrope. We performed measurements of electrical characteristic curves of capacitance as a function of applied tension (C-V) and current as a function of the applied tension (I-V). We showed the dielectric constant (k) and the resistivity (ρ) as functions of the CF4 concentration. On films with 65% CF4, we found that k = 2.7, and on films with 70% CF4, ρ = 12.3 × 1011 Ω cm. The value of the electrical breakdown field to films with 70% CF4 is 5.3 × 106 V/cm.

  3. Temperature dependences of piezoelectric, elastic and dielectric constants of L-alanine crystal

    NASA Astrophysics Data System (ADS)

    Tylczyński, Z.; Sterczyńska, A.; Wiesner, M.

    2011-09-01

    Temperature changes in the components of piezoelectric, elastic and dielectric tensors were studied in L-alanine crystals in the range 100-300 K. A jumpwise increase in the c55 component of the elastic stiffness accompanied by maxima in damping of all face-shear modes observed at 199 K in L-alanine crystal were interpreted as a result of changes in the NH3+ vibrations occurring through electron-phonon coupling. All components of the piezoelectric tensor show small anomalies in this temperature range. The components of the electromechanical coupling coefficient determined indicate that L-alanine is a weak piezoelectric.

  4. Temperature dependences of piezoelectric, elastic and dielectric constants of L-alanine crystal.

    PubMed

    Tylczyński, Z; Sterczyńska, A; Wiesner, M

    2011-09-07

    Temperature changes in the components of piezoelectric, elastic and dielectric tensors were studied in L-alanine crystals in the range 100-300 K. A jumpwise increase in the c(55) component of the elastic stiffness accompanied by maxima in damping of all face-shear modes observed at 199 K in L-alanine crystal were interpreted as a result of changes in the NH(3)(+) vibrations occurring through electron-phonon coupling. All components of the piezoelectric tensor show small anomalies in this temperature range. The components of the electromechanical coupling coefficient determined indicate that L-alanine is a weak piezoelectric.

  5. Effect of Ca-Al-Si-O common glass on dielectric properties of low-temperature co-fired ceramic materials with different fillers.

    PubMed

    Park, Zee-Hoon; Yeo, Dong-Hun; Shin, Hyo-Soon

    2014-11-14

    High-density integration in single component used for mobile communication is highly demanded with the miniaturization trend in multi-functional light-weighted mobile communication devices. Embedding passive components into multi-layered ceramic chips is also increasingly needed for high integrity. The need for high strength materials to be used in handheld devices has also increased. To this end, many attempts to join different low-temperature co-fired ceramics (LTCC) materials with different dielectric constants have been made, but failed with de-laminations or internal cracks mainly due to difference of thermal expansion coefficients. It is thought that this difference could be minimized with the use of common glass in different LTCC materials. In this study, several candidates of common glass were mixed with various fillers of LTCC to have various dielectric constants in the radio-frequency, and to minimize the mismatch in joining. Ca-Al-Si-O glass was mixed with 1.3MgO-TiO2, cordierite and CaTiO3. Mixtures were tape-cast and sintered to be compared with their micro-structures, dielectric properties and thermo-mechanical characteristics. When 1.3MgO-TiO2 with volumetric ratio of 30% was mixed with Ca-Al-Si-O glass, the measured dielectric constant was 7.9, the quality factor was 3708. With 45 volumetric percent of cordierite, the dielectric constant was 5 and the quality factor was 1052.

  6. Method of using sacrificial materials for fabricating internal cavities in laminated dielectric structures

    DOEpatents

    Peterson, Kenneth A.

    2009-02-24

    A method of using sacrificial materials for fabricating internal cavities and channels in laminated dielectric structures, which can be used as dielectric substrates and package mounts for microelectronic and microfluidic devices. A sacrificial mandrel is placed in-between two or more sheets of a deformable dielectric material (e.g., unfired LTCC glass/ceramic dielectric), wherein the sacrificial mandrel is not inserted into a cutout made in any of the sheets. The stack of sheets is laminated together, which deforms the sheet or sheets around the sacrificial mandrel. After lamination, the mandrel is removed, (e.g., during LTCC burnout), thereby creating a hollow internal cavity in the monolithic ceramic structure.

  7. Low damage etching method of low-k material with a neutral beam for interlayer dielectric of semiconductor device

    SciTech Connect

    Kang, Seung Hyun; Kim, Jong Kyu; Lee, Sung Ho; Kim, Jin Woo; Yeom, Geun Young

    2015-03-15

    To reduce the cross-talk between nanoscale devices, low-k materials such as methyl silsesquioxane (MSQ), which is damaged easily during plasma etching, are introduced as an intermetallic dielectric material in addition to the use of copper as the conducting material for the reduction of parasitic resistance and capacitance. In this study, beam techniques such as neutral/ion beams were used in the etching of MSQ and the effect of these beam techniques on the reduction of the degradation of the MSQ were investigated. When MSQ was etched using the same CF{sub 4} etch gas at the similar etch rate as that used for conventional MSQ etching using inductively coupled plasmas (ICPs), the neutral/ion beam etching showed lower F contents and lower penetration depth of F, indicating decreased degradation by fluorination of MSQ during etching using the beam techniques. Especially, the neutral beam etching technique showed the lowest F contamination and the lower penetration depth of F among the etch methods. When the dielectric constant was measured after the etching of the same depth, the MSQ etched with the neutral beam showed the lowest change of the dielectric constant, while that etched using the ICP showed the highest change of dielectric constant. The lower degradation, that is, the lower chemical modification of MSQ material with the beam technique is believed to be related to the decreased concentration of radical species in the processing chamber reacting with the MSQ surface, while the lowest degradation using the neutral beam is believed to be due to the lower reaction rate of the reactive neutral compared to reactive ions.

  8. Properties of Atmospheric Pressure Ar Plasma Jet Depending on Treated Dielectric Material

    NASA Astrophysics Data System (ADS)

    Prysiazhnyi, Vadym; Ricci Castro, Alonso H.; Kostov, Konstantin G.

    2017-02-01

    Atmospheric pressure plasma jet operated in argon was utilized to modify surfaces of glass, acrylic, and PTFE dielectrics. This paper describes the influence of the dielectric substrate on operation and properties of plasma. Two modes of operation (each of those have two patterns) were described. The transition from one mode to another, values of the dissipated power, and spreading of plasma over the dielectric surfaces strongly depended on the substrate material. Additionally, three methods of plasma spreading estimation were presented and discussed.

  9. Structure and dielectric properties of amorphous LaAlO3 and LaAlOxNy films as alternative gate dielectric materials

    NASA Astrophysics Data System (ADS)

    Lu, Xu-bing; Liu, Zhi-guo; Wang, Yi-ping; Yang, Ying; Wang, Xiao-ping; Zhou, Hong-wei; Nguyen, Bich-yen

    2003-07-01

    Amorphous LaAlO3 (LAO) and LAOxNy (LAON) films have been prepared by pulsed laser deposition technique on Si (100) substrates and Pt coated silicon substrates. X-ray diffraction, transmission electron microscopy and differential thermal analysis investigations showed that both kinds of films remain amorphous up to a high temperature of 860 °C. Atomic force microscopy study indicated that the surface of the deposited films is very smooth with a root mean square roughness of 0.14 nm for 8 nm LAO. LAON films have a smoother surface than that of LAO films. High-resolution transmission electron microscope studies showed there often exists interfacial reaction between LAO and Si. One LAON/Si structure nearly without interfacial layer has been obtained. For LAO films, high bandgap of 6.55 eV and medium dielectric constant of 25-27 have been obtained. The LAON films showed small equivalent oxide thickness of 1.1 nm with a low leakage of 0.074 A/cm2@Vg=+1 V. It is proposed that amorphous LAON films are very promising dielectric materials for high k gate dielectric applications.

  10. Interactions of carbon nanotubes and gold nanoparticles: the effects of solvent dielectric constant and temperature on controlled assembly of superstructures.

    PubMed

    Rance, G A; Khlobystov, A N

    2014-05-28

    The effects of solvent dielectric constant and temperature on the non-covalent interactions between gold nanoparticles and carbon nanotubes have been explored. Our experiments have shown that fewer nanoparticles are adsorbed onto nanotubes in high dielectric assembly environments. This has been correlated with an increase in the differential capacitance of nanoparticles relative to the bulk solvent resulting in more local charge on nanoparticles and thus heightened repulsive electrostatic interactions in higher polarity organic solvents. Furthermore, our temperature-dependent measurements have demonstrated for the first time that (i) the apparent activation barrier to adsorption of nanoparticles on nanotubes of Ea = 9.6 kJ mol(-1) lies clearly within the range expected for non-covalent interactions and (ii) the adsorption of nanoparticles onto nanotubes is reversible and may represent an equilibrium process sensitive to temperature according to Le Chatelier's principle. Thus, we further demonstrate that modulation of non-covalent interactions can be harnessed for the precision derivatisation of nanocarbons with noble metals.

  11. Towards Automated Benchmarking of Atomistic Forcefields: Neat Liquid Densities and Static Dielectric Constants from the ThermoML Data Archive

    PubMed Central

    Beauchamp, Kyle A.; Behr, Julie M.; Rustenburg, Ariën S.; Bayly, Christopher I.; Kroenlein, Kenneth; Chodera, John D.

    2015-01-01

    Atomistic molecular simulations are a powerful way to make quantitative predictions, but the accuracy of these predictions depends entirely on the quality of the forcefield employed. While experimental measurements of fundamental physical properties offer a straightforward approach for evaluating forcefield quality, the bulk of this information has been tied up in formats that are not machine-readable. Compiling benchmark datasets of physical properties from non-machine-readable sources requires substantial human effort and is prone to the accumulation of human errors, hindering the development of reproducible benchmarks of forcefield accuracy. Here, we examine the feasibility of benchmarking atomistic forcefields against the NIST ThermoML data archive of physicochemical measurements, which aggregates thousands of experimental measurements in a portable, machine-readable, self-annotating IUPAC-standard format. As a proof of concept, we present a detailed benchmark of the generalized Amber small molecule forcefield (GAFF) using the AM1-BCC charge model against experimental measurements (specifically bulk liquid densities and static dielectric constants at ambient pressure) automatically extracted from the archive, and discuss the extent of data available for use in larger scale (or continuously performed) benchmarks. The results of even this limited initial benchmark highlight a general problem with fixed-charge forcefields in the representation low dielectric environments such as those seen in binding cavities or biological membranes. PMID:26339862

  12. Measurement of the Temperature Dependence of the Dielectric Constant of PMMA for the nEDM Experiment at Oak Ridge National Laboratory

    NASA Astrophysics Data System (ADS)

    Ochsendorf, Marcus

    2016-09-01

    The nEDM experiment at Oak Ridge National Laboratory aims to search for the electric dipole moment of the neutron at the 10-28 level. The experiment is currently in the research and development phase. In the experiment, ultra-cold neutrons stored inside a container made from PolyMethylMethAcrylate (PMMA) will be subjected to a strong electric field. In order to calculate the electric field within the box very precisely, the dielectric constant of PMMA must be known very well. The experiment will take place at 0.4K and it is not known if the dielectric constant of PMMA changes as a function of temperature. In order to test this, a ``Poor Man's Cryostat'' was constructed. PMMA was cooled down to 77K temperature, and the dielectric constant of PMMA was measured as a function temperature. Experimental details and results of the tests will be presented. Funded by the National Science Foundation.

  13. Effect of Solvent Dielectric Properties on the Spontaneous-Emission Rate Constant of Molecular Singlet Oxygen

    NASA Astrophysics Data System (ADS)

    Jarnikova, E. S.; Parkhats, M. V.; Stasheuski, A. S.; Dzhagarov, B. M.

    2017-01-01

    Quantum yields and luminescence lifetimes of singlet oxygen in 18 different solvents and binary mixtures were measured using laser fluorometry. The results allowed a direct effect of the refractive index on the radiative rate constant kr of the singlet-oxygen a 1 Δ g → X 3 Σ g - transition caused by a change of photon state density in addition to an indirect effect through a local-field factor to be determined. The experimentally observed rise of kr with increasing medium refractive index could not be explained by the influence of only these two factors. The discrepancy was overcome by taking into account changes of the singlet-oxygen transition dipole moment. Consideration of all three factors explained the influence of the medium on rate constant kr

  14. Laboratory measurements of dielectric properties of compact and granular materials, in relation with Rosetta mission.

    NASA Astrophysics Data System (ADS)

    Brouet, Y.; Levasseur-Regourd, A. C.; Encrenaz, P.; Gheudin, M.; Ciarletti, V.; Gulkis, S.; Jambon, A.; Ruffié, G.; Prigent, C.

    2012-04-01

    The European Rosetta spacecraft (s/c), launched in 2004, will be the first s/c to orbit a comet and place a lander module on its surface. In 2014, the s/c will rendezvous with the comet 67P/Churyumov-Gerasimenko and place the lander on its surface thereby allowing in situ and remote sensing of the comet nucleus. Two radio experiments, one passive (MIRO [1]) and one active (CONSERT [2]), are aboard the Rosetta s/c. MIRO, composed of two radiometers, with center band frequencies at 190 GHz and at 563 GHz to determine the brightness temperatures of the target surfaces and sub-surfaces, has already observed asteroids (2867) Steins [3] and (21) Lutetia [4]. CONSERT will investigate the deep interior of the nucleus using 90 MHz radio-waves transmitted from the orbiter through the nucleus and returned to the orbiter from the lander. To support interpretations of MIRO and CONSERT observations, a program of dielectric properties measurements is under development on a large range of frequencies encompassing those of the above-mentioned experiments. Several instruments for dielectric constant determination are available at IMS laboratory (Bordeaux, France): impedance analyzer, coaxial sensor, resonant cavities (measuring respectively at 100 MHz, 0.5-6 GHz, 1.2-13.4 GHz). Millimeter benches are available at both IMS and LERMA laboratories (measuring respectively at 30-110 GHz and 70-230 GHz). Taking into account the possible presence of regolith layers on the surface of asteroids or nuclei and the very low density of cometary nuclei [5], the dependence of the dielectric constant on the structure and porosity of given granular materials needs also to be investigated (while the thermal and hygrometric conditions are carefully monitored). We have already reported measurements obtained on various meteorites, possibly representative of some asteroid surfaces [6, 7]. We will also report systematic measurements obtained on a large sample of pyroclastic deposits from Etna, providing

  15. Crystalline perfection, optical and dielectric studies on L-histidine nitrate: A nonlinear optical material

    NASA Astrophysics Data System (ADS)

    Riscob, B.; Kushwaha, S. K.; Shakir, Mohd.; Nagarajan, K.; Maurya, K. K.; Haranath, D.; Roy, S. D. D.; Bhagavannarayana, G.

    2011-12-01

    Single crystals of L-histidine nitrate (LHN), a recently investigated nonlinear optical material, were grown by conventional solution technique. Crystal structure and vibrational modes of the grown crystals were confirmed by powder X-ray diffractometry and FT-Raman spectrometry, respectively. Crystalline perfection of the grown crystals was evaluated by employing an in-house developed high-resolution X-ray diffractometer (HRXRD) and it was found that the grown crystals were free from structural grain boundaries and the perfection was reasonably good. However, HRXRD could reveal the fact that the crystals contain predominantly the interstitial point defects. The birefringence was measured over a range of wavelength between 5480 and 5630 Å and it was found that its value is nearly constant and 10 times higher than that of KDP. The optical band gap was found to be ∼3.73 eV. The photoluminescence excitation and emission spectra for single crystals were recorded. The SHG efficiencies of LHN samples of different particle sizes were measured by the Kurtz and Perry technique and they removed the ambiguity in the values reported differently in the literature. Dielectric properties were studied as a function of temperature over a wide range of frequency. The optical and dielectric studies along with the crystalline perfection reveal that the LHN crystal could be a good candidate for nonlinear optical devices.

  16. Transport and dielectric studies of metallic, semiconducting, and magnetic materials and devices

    NASA Astrophysics Data System (ADS)

    Vasic, Relja

    Several organic and inorganic systems of importance for fundamental physics and applications have been studied by magnetotransport, dielectric constant, and Raman spectroscopy techniques. At the beginning of my thesis work, I investigated three carbon based organic systems: carbon fibers, pentacene derivatives, and a nanomagnetic material ("V15"). In the latter stages of my dissertation, I used the techniques I had developed to explore the properties of two inorganic systems: NiFe nanopillars in a silicon matrix, and spin systems in multiferroic rare earth-transition metal oxides. The main activities and achievements of my thesis work are as follows: The carbon fibers were characterized by magnetotransport and Raman spectroscopy studies. I found that carbon fibers are promising as wires in molecular electronics and compatible with organic films. Preliminary results on simple films of melted pentacene derivatives connected with carbon fiber wires were a first step in the fabrication and characterization of pentacene field effect transistors (FET's). The work on the pentacene system resulted in a series of successful logic circuits based on field-effect transistors such as NOT (inverter), NOR, and NAND. The temperature-dependent mobility was described as thermally activated at low gate voltages, but at high gate voltages the mobility was enhanced due to shallow traps. The second system investigated was the organic nanomagnetic material, polyoxovanadate, K6[V15As6O42(H 2O)]˙8H2O (i.e. V15). The conductivity and the dielectric measurements at high and low temperatures respectively were used to determine electrical properties of this single magnet molecule system. The main accomplishments were the determination of the energy gap (0.2eV) and the identification of multiple dipole relaxation modes. Raman vibrational spectroscopy was used to correlate dielectric relaxation with the Raman intramolecular vibrations. An investigation was then carried out on NiFe nanopillars

  17. Hydrogen bond network in the hydration layer of the water confined in nanotubes increasing the dielectric constant parallel along the nanotube axis.

    PubMed

    Qi, Wenpeng; Zhao, Hongwei

    2015-09-21

    The water confined in nanotubes has been extensively studied, because of the potential usages in drug delivery and desalination. The radial distribution of the dielectric constant parallel along the nanotube axis was obtained by molecular dynamics simulations in a carbon nanotube and a nanotube with a very small van der Waals potential. The confined water was divided into two parts, the middle part water and the hydration water. In both cases, the hydrogen bond orientation of the middle water is isotropic, while the hydrogen bonds in hydration layers are apt to parallel along the nanotube axis. Therefore, the hydration water has higher dipole correlations increasing the dielectric constant along the nanotube axis.

  18. Microclimate, Water Potential, Transpiration, and Bole Dielectric Constant of Coniferous and Deciduous Tree Species in the Continental Boreal Ecotone of Central Alaska

    NASA Technical Reports Server (NTRS)

    Zimmermann, R.; McDonald, K.; Way, J.; Oren, R.

    1994-01-01

    Tree canopy microclimate, xylem water flux and xylem dielectric constant have been monitored in situ since June 1993 in two adjacent natural forest stands in central Alaska. The deciduous stand represents a mature balsam poplar site on the Tanana River floodplain, while the coniferous stand consists of mature white spruce with some black spruce mixed in. During solstice in June and later in summer, diurnal changes of xylem water potential were measured to investigate the occurrence and magnitude of tree transpiration and dielectric constant changes in stems.

  19. Hydrogen bond network in the hydration layer of the water confined in nanotubes increasing the dielectric constant parallel along the nanotube axis

    NASA Astrophysics Data System (ADS)

    Qi, Wenpeng; Zhao, Hongwei

    2015-09-01

    The water confined in nanotubes has been extensively studied, because of the potential usages in drug delivery and desalination. The radial distribution of the dielectric constant parallel along the nanotube axis was obtained by molecular dynamics simulations in a carbon nanotube and a nanotube with a very small van der Waals potential. The confined water was divided into two parts, the middle part water and the hydration water. In both cases, the hydrogen bond orientation of the middle water is isotropic, while the hydrogen bonds in hydration layers are apt to parallel along the nanotube axis. Therefore, the hydration water has higher dipole correlations increasing the dielectric constant along the nanotube axis.

  20. Measurement of the complex dielectric constant down to helium temperatures. I. Reflection method from 1 MHz to 20 GHz using an open ended coaxial line

    NASA Astrophysics Data System (ADS)

    Martens, H. C. F.; Reedijk, J. A.; Brom, H. B.

    2000-02-01

    The reflection off an open ended coaxial probe pressed against a material under test is used to determine the complex microwave (1 MHz-20 GHz) dielectric response of the material. A full-wave analysis of the aperture admittance of the probe, in terms of the dielectric properties of the backing material and the dimensions of the experimental geometry, is given. We discuss the calibration procedure of the setup and present the complex dielectric response of several materials determined from the measured reflection coefficient. The results obtained with the open ended coax interpolate well between data taken at lower and higher frequency bands using different experimental methods. We demonstrate that this method can be applied to perform dielectric measurements at cryogenic temperatures.

  1. Numerical study of the interaction of a helium atmospheric pressure plasma jet with a dielectric material

    NASA Astrophysics Data System (ADS)

    Wang, Lijun; Zheng, Yashuang; Jia, Shenli

    2016-10-01

    This is a computational modeling study of a cold atmospheric pressure helium plasma jet impinging on a dielectric surface placed normal to the jet axis. This study provides insights into the propagation mechanism of the plasma jet, the electrical properties, and the total accumulated charge density at the dielectric surface. For the radial streamer propagation along the dielectric surface, Penning ionization and the electron impact ionization of helium atoms are the major ionization reactions in the streamer head, while Penning ionization is the only dominant contributor along the streamer body. In addition, the plasma bullet velocity along the dielectric surface is 10-100 times lower than that in the plasma column. Increasing tube radius or helium flow rate lowers air entrainment in the plasma jet, leading to a decrease of the radial electric field and the accumulated charge density at the dielectric surface. Furthermore, the tube radius has weaker influence on the plasma properties as tube radius increases. For a target dielectric with lower relative permittivity, a higher radial electric field penetrates into the material, and the surface ionization wave along the dielectric surface extends farther. Higher relative permittivity of the treated dielectric results in more charging at the dielectric surface and more electron density in the plasma column.

  2. Highly Scaled High Dielectric Constant Oxides on III-V CMOS with Low Interface Trap and Low Leakage Densities

    NASA Astrophysics Data System (ADS)

    Chobpattana, Varistha

    Complementary metal-oxide-semiconductor (CMOS) transistors are being aggressively scaled, reaching the fundamental limits of silicon. Due to their much higher electron mobilities, III-V semiconductors are being considered as alternative channel materials to potentially replace Si. This requires the integration of high dielectric constant (high-k) oxides with III-V semiconductor layers, which is the most significant challenge to achieve high performance of III-V metal-oxide-semiconductor field-effect transistors (MOSFETs). Large interface trap densities, inherent to these interfaces, degrade the transistor performance. In this dissertation, we utilize in-situ atomic layer deposition (ALD) combined with surface passivation techniques to reduce the interface traps densities between high-k oxides and III-V semiconductors to obtain highly scaled, low defect density interfaces. Cycles of hydrogen and/or nitrogen plasmas and metal-organic precursors were applied directly onto n- and p type In0.53 Ga0.47As surfaces before high-k oxide ALD. The high-k oxides investigated include Al2O 3, HfO2, ZrO2, and TiO2. We examined the electrical characteristics of MOS capacitors (MOSCAPs), surface morphology of the surface, and chemical components of the interface. High quality interfaces of high-k oxide and n-type In0.53Ga0.47As with low interface trap densities (Dit) of 1012 eV-1 cm-2, low leakage current density, and high capacitance densities gate stacks (>5 muF/cm 2) were achieved by the optimized cycles of nitrogen plasma+tetrakis(dimethylamido)titanium (TDMAT) ALD surface cleaning. Using x-ray photoelectron spectroscopy, the interface region indicates that the removing As-oxides, sub-oxides, and As-As bonding are responsible for decreasing frequency dispersion in the midgap region of the n-type In0:53Ga0:47As, reducing midgap Dit, and unpinning Fermi level. The modified interface chemistry from Al2O3 to TiO2 leads to lower frequency dispersion in accumulation. The highly

  3. Metal–organic frameworks for electronics: emerging second order nonlinear optical and dielectric materials

    PubMed Central

    Mendiratta, Shruti; Lee, Cheng-Hua; Usman, Muhammad; Lu, Kuang-Lieh

    2015-01-01

    Metal–organic frameworks (MOFs) have been intensively studied over the past decade because they represent a new category of hybrid inorganic–organic materials with extensive surface areas, ultrahigh porosity, along with the extraordinary tailorability of structure, shape and dimensions. In this highlight, we summarize the current state of MOF research and report on structure–property relationships for nonlinear optical (NLO) and dielectric applications. We focus on the design principles and structural elements needed to develop potential NLO and low dielectric (low-κ) MOFs with an emphasis on enhancing material performance. In addition, we highlight experimental evidence for the design of devices for low-dielectric applications. These results motivate us to develop better low-dielectric and NLO materials and to perform in-depth studies related to deposition techniques, patterning and the mechanical performance of these materials in the future. PMID:27877833

  4. Measuring sap flow, and other plant physiological conditions across a soil salinity gradient in the lower Colorado River at Cibola National Wildlife Refuge: Vegetation and soil physiology linkages with microwave dielectric constant

    NASA Astrophysics Data System (ADS)

    McDonald, K. C.; Lasne, Y.; Schroeder, R.; Morino, K.; Hultine, K. R.; Nagler, P. L.

    2009-12-01

    We used ground measurements to examine stand structure and evapotranspiration of Tamarix in the Cibola National Wildlife Refuge (CNWR) on the Lower Colorado River. Three Tamarix study sites were established at different distances from the Colorado River on a river terrace in the CNWR. The sites were chosen from aerial photographs to represent typical dense stands of Tamarix within the CNWR. The sites were representative of differing saline environments, with each having ground water with distinct salt concentration levels. Wells were established at the site to establish depth to water and the salinity concentration within the ground water. We monitored xylem sap flow within each of the three stands. In addition we measured leaf area index to characterize canopy structure. We compared ET, foliage density, depth to water, and salinity among the Tamarix sites to examine stand-level variability driven by the variations in salinity. We supplemented these collections with measurements to characterize soil and vegetation microwave dielectric properties and their relationship to physiologic parameters. The dielectric properties of a material describe the interaction of an electric field with the material. Previous field experiments have demonstrated that varying degrees of correlation exist between vegetation dielectric properties and tree canopy water status. Temporal variation of the dielectric constant of woody plant tissue may result from changes in water status (e.g., water content) and chemical composition, albeit to varying degrees of sensitivity. The varying amount of ground water salinity at CNWR offers a unique opportunity to examine the relationship between vegetation and soil dielectric constant as related to vegetation ecophysiology. A field portable vector network analyzer is used to measure the microwave dielectric spectrum of the soil and vegetation Combined with measurements of vegetation xylem sap flux and soil chemistry, these measurements allow

  5. Identification of material constants for a composite shell structure

    SciTech Connect

    Carne, T.G.; Martinez, D.R.

    1987-01-01

    A finite element model of a composite shell was created. The model includes uncertain orthotropic elastic constants. To identify these constants, a modal survey was performed on an actual shell. The resulting modal data along with the finite element model of the shell were used in a Bayes estimation algorithm. Values of the elastic constants were estimated which minimized the differences between the test results and the finite element predictions. The estimation procedure employed the concept of successive linearization to obtain an approximate solution to the original nonlinear estimation problem.

  6. Dielectric constant dispersion of yttrium-doped (Ba,Sr)TiO3 films in the high-frequency (10 kHz-67 GHz) domain

    NASA Astrophysics Data System (ADS)

    Jeong, Doo Seok; Hwang, Cheol Seong; Baniecki, J. D.; Shioga, T.; Kurihara, K.; Kamehara, N.; Ishii, M.

    2005-12-01

    The frequency dispersion of the dielectric constant of yttrium (Y)-doped (Ba,Sr)TiO3 thin films (Y-BST) in the high-frequency domain (10kHz-67GHz) was investigated. In order to remove the substantial parasitic capacitances, inductances, and resistances from the measured impedance data, test samples, short-circuit standard, and open-circuit standard structures were fabricated and their frequency response was measured. Before removing parasitic components, the measured dielectric response showed a rolloff at approximately 4GHz. However, after circuit calibration, the dielectric constant was almost constant up to 40GHz where another rolloff was observed. However, this rolloff was due to the uncompensated small parasitic components. Therefore, the dielectric constant of the Y-BST films (170 with a film thickness of 30nm) showed small frequency dispersion corresponding to the Curie-von Schweidler dispersion, of which the exponent is -0.0131, up to 40GHz. Furthermore, the decrease of the capacitance was 17% in the frequency range from 10kHzto40GHz.

  7. Binary metal and semiconductor quantum dot metamaterials with negative optical dielectric constant and compensated loss for small volume waveguides, modulators and switches

    NASA Astrophysics Data System (ADS)

    Ponizovskaya, Ekaterina; Thylen, Lars; Bratkovsky, Alexander; Fu, Ying

    2009-06-01

    We study numerically and analytically a binary mixture of quantum dots exhibiting gain and loss. For a mixture of gain quantum dots and silver nanoparticles, we find conditions when the composite shows negative dielectric constant operation and lossless operation. The composites of this kind may be used for dense integration of photonic components as well as modulation and switching in optical interconnect systems

  8. Some characteristics of dielectric materials at cryogenic temperatures for HVDC systems

    SciTech Connect

    Chowdhuri, P.

    1981-02-01

    This dielectric study was performed as part of the dc Superconducting Power Transmission Line Program. During a screening test program, the dc breakdown strength of 12 dielectric materials, in sheet form, was determined at 12 K under 1.38 MPa of helium pressure, the operating conditions of the cable design. Tests were also made with four of these materials impregnated with mineral oil. Further dc breakdown tests were performed on five of these dielectric materials at various temperatures (12 to 298 K) and pressures (0.69 and 1.38 MPa) of helium. Two sets of experiments were performed on cellulose paper impregnated with distilled water at 83 K and 1.38 MPa of helium pressure. Five dielectric materials were then selected for tests as cable samples with dc and impulse voltages at 12 K and 1.38 MPa of helium. Data are presented on these tests, as well as on those of the electrical conductivity of four dielectric materials at cryogenic temperatures, and of the surface flashover strength of an epoxy bushing at 12 K and 298 K under 0.69 MPa and 1.38 MPa of helium pressures. The characteristics of the dielectric behavior at cryogenic temperatures are discussed.

  9. Measurement of the microwave dielectric constant for low-loss samples with finite thickness using open-ended coaxial-line probes

    NASA Astrophysics Data System (ADS)

    Jiang, G. Q.; Wong, W. H.; Raskovich, E. Y.; Clark, W. G.; Hines, W. A.; Sanny, J.

    1993-06-01

    This work addresses the effect of finite sample thickness on microwave dielectric constant measurements for thin, planar, low-loss samples using the open-ended coaxial-line probe method. Detailed measurements of the dielectric constant were carried out on a wide range of thicknesses of air samples which were backed by infinitely thick teflon and alumina dielectric media. The measurements were made at room temperature for various (50 Ω) coaxial-line dimensions, microwave frequencies 4-8 GHz, and power levels near a fraction of a mW. The results provide strong support for previously published theoretical calculations based on a boundary value problem which uses a spectral domain formulation for the aperture fields. From thin, planar samples, values of 10.4±0.5 and 25.9±1.3 were obtained at 5 GHz and 300 K for the bulk dielectric constant of MgO and LaAl2O3, respectively. The applicability of a simple empirical model based on an exponential fit is discussed.

  10. Identification of material constants for a composite shell structure

    SciTech Connect

    Carne, T.G.; Martinez, D.R.

    1987-03-01

    One of the basic requirements of an engineering analysis is the development of an adequate mathematical model describing the system. Frequently, comparisons with test data are used as a measure of the model's adequacy, or the test data are directly used to update or modify the model. For nonmetallic structures, the modeling task is often more difficult due to uncertainties in the elastic constants. System identification provides a methodology for systematically updating the mathematical model for improved correlation with test data. In this work a finite element model of a composite shell was created. The model includes uncertain orthotropic elastic constants. To identify these constants, a modal survey was performed on an actual shell. The resulting modal data along with the finite element model of the shell were used in a Bayes estimation algorithm. Values of the elastic constants were estimated which minimized the differences between the test results and the finite element predictions. The estimation procedure employed the concept of successive linearization to obtain an approximate solution to the original nonlinear estimation problem.

  11. Mesostructured materials for optical applications: from low-k dielectrics to sensors and lasers

    NASA Astrophysics Data System (ADS)

    Wirnsberger, Gernot; Yang, Peidong; Scott, Brian J.; Chmelka, Bradley F.; Stucky, Galen D.

    2001-09-01

    Recent advances on the use of mesoporous and mesostructured materials for electronic and optical applications are reported. The focus is on materials which are processed by block-copolymer templating of silica under weakly acidic conditions and by employing dip- and spin-coating as well as soft lithographic methods to bring them into a well-defined macroscopic shape. Several chemical strategies allow the mesostructure architecture to be used for electronic/optical applications: Removal of the block-copolymers results in highly porous, mechanically and thermally robust materials which are promising candidates for low dielectric constant materials. Since the pores are easily accessible, these structures are also ideal hosts for optical sensors, when suitable are incorporated during synthesis. For example, a fast response optical pH sensor was implemented on this principle. As-synthesized mesostructured silica/block-copolymer composites, on the other hand, are excellently suited as host systems for laser dyes and photochromic molecules. Laser dyes like rhodamine 6G can be incorporated during synthesis in high concentrations with reduced dimerization. This leads to very-low-threshold laser materials which also show a good photostability of the occluded dye. In the case of photochromic molecules, the inorganic-organic nanoseparation enables a fast switching between the colorless and colored form of a spirooxazine molecule, attributed to a partitioning of the dye between the block-copolymer chains. The spectroscopic properties of these dye-doped nanocomposite materials suggest a silica/block-copolymer/dye co-assembly process, whereby the block-copolymers help to highly disperse the organic dye molecules.

  12. Development of dielectric barrier discharge-type ozone generator constructed with piezoelectric transformers: effect of dielectric electrode materials on ozone generation

    NASA Astrophysics Data System (ADS)

    Teranishi, Kenji; Shimomura, Naoyuki; Suzuki, Susumu; Itoh, Haruo

    2009-11-01

    The dependence of ozone generation on the types of dielectric electrode material has been investigated using an ozone generator constructed with the piezoelectric transformer developed in our laboratory. The ozone generator is based on the excitation of the dielectric barrier discharge (DBD), which has the advantage of a compact configuration for generating ozone. Four kinds of dielectric materials are prepared for dielectric barrier electrodes. Electrical properties of the DBD and the ozone generation characteristics are investigated for the different dielectric materials. Differences in the discharge mode among the barrier electrode materials are recognized and discussed on the basis of the results of the Lissajous figures and voltage-current waveforms. During the continuous running of the generator, a temporal decrease in ozone concentration is observed owing to the temperature increase inside the reactor. Although the ozone generation characteristics are influenced by many properties of dielectrics, two important factors for achieving high-efficiency ozone generation are identified in this study. One is the use of a high-thermal conductivity material for the dielectric electrode, which functions well as a heat sink for transferring the generated heat to the outside through the material. The other factor is the control of the discharge mode. Our results show that the discharge mode that is considered as Townsend-like DBD is suitable for high-efficiency ozone generation.

  13. Simulation of the frequency dispersion of effective dielectric characteristics of composite materials

    SciTech Connect

    Yakovlev, V. B.; Bardushkin, V. V.; Lavrov, I. V. Yakovleva, E. N.

    2014-12-15

    The problems of calculating the effective dielectric characteristics of polycrystalline materials are considered taking into account the frequency dependence of the characteristics of individual components. The effective characteristics of ceramics such as lead zirconate-titanate with titanium and zirconium oxide, metal lead, and water inclusions are calculated in the Maxwell-Garnett and Bruggeman approximations. The dependences of the effective dielectric characteristics on the inclusion concentration and applied electromagnetic-field frequency are obtained.

  14. Experimental determination of material constants of a hybrid composite laminate

    SciTech Connect

    Ihekweazu, S.N.; Lari, S.B.; Unanwa, C.O.

    1999-07-01

    This paper discusses the results of the experimental study that was conducted in order to determine the material properties of a hybrid composite laminate made from Fiberite material MXM-7714/120 (a fabric prepreg consisting of woven Kevlar{reg_sign} 49 reinforcement impregnated with Fiberite 250 F (121 C) curing 7714 epoxy resin) and HYE-2448AIE (a 250 F (121 C) curing epoxy resin impregnated unidirectional graphite tape). First, each of the materials that comprise the hybrid laminate was fabricated separately according to ASTM-D-3039 specification in order to determine their material properties. The materials were then hybridized and the properties were determined. Data from this experiment reveal that a new class of material that can meet desired specifications can be created through hybridization. The data also revealed that the properties of the materials bonded together as a hybrid complement the properties of the constituent members of the hybrid.

  15. Optical bistability in photonic crystal microrings with nonlinear dielectric materials.

    PubMed

    Ogusu, Kazuhiko; Takayama, Kosuke

    2008-05-12

    We study the linear resonance properties of several types of microrings in a two-dimensional photonic crystal (PC) consisting of a square lattice with air holes in dielectric using the plane-wave expansion method and the FDTD method. Moreover we investigate the nonlinear responses, especially optical bistability when an intense optical pulse is incident into the microrings. In this paper, Ag-As-Se chalcogenide glass is assumed as nonlinear dielectric, which has a high third-order nonlinearity. Although line-defect waveguides in an air-hole-type PC are usually multimoded, we can obtain interesting unique properties such as counter rotation of intracavity fields, transmission to all output ports, and unstable nonlinear oscillations in the multimoded PC microring. We can improve the resonance characteristics by partly introducing single-mode waveguides into microrings and can obtain stable optical bistability.

  16. Parameter identification of material constants in a composite shell structure

    SciTech Connect

    Martinez, D.R.; Carne, T.G.

    1988-01-01

    One of the basic requirements in engineering analysis is the development of a mathematical model describing the system. Frequently, comparisons with test data are used as a measurement of the adequacy of the model. An attempt is typically made to update or improve the model to provide a test-verified analysis tool. System identification provides a systematic procedure for accomplishing this task. The terms system identification, parameter estimation, and model correlation all refer to techniques that use test information to update or verify mathematical models. The goal of system identification is to improve the correlation of model predictions with measured test data, and produce accurate, predictive models. For nonmetallic structures the modeling task is often difficult due to uncertainties in the elastic constants. In this work a parameter identification procedure was used to determine the elastic constants of a cylindrical, graphite epoxy composite shell. A finite element model of the shell was created, which included uncertain orthotropic elastic constants. A modal survey test was then performed on the shell. The resulting modal data, along with the finite element model of the shell, were used in a Bayes estimation algorithm. This permitted the use of covariance matrices to weight the confidence in the initial parameter values as well as confidence in the measured test data. The estimation procedure also employed the concept of successive linearization to obtain an approximate solution to the original nonlinear estimation problem. 17 refs., 7 figs.

  17. Apparatus and method for constant flow oxidizing of organic materials

    DOEpatents

    Surma, Jeffrey E.; Nelson, Norvell; Steward, G. Anthony; Bryan, Garry H.

    1999-01-01

    The invention is a method and apparatus using high cerium concentration in the anolyte of an electrochemical cell to oxidize organic materials. The method and apparatus further use an ultrasonic mixer to enhance the oxidation rate of the organic material in the electrochemical cell. A reaction vessel provides an advantage of independent reaction temperature control and electrochemical cell temperature control. A separate or independent reaction vessel may be used without an ultrasonic mixer to oxidize gaseous phase organic materials.

  18. Preliminary investigation of polystyrene/MoS{sub 2}-Oleylamine polymer composite for potential application as low-dielectric material in microelectronics

    SciTech Connect

    Landi, Giovanni; Altavilla, Claudia; Iannace, Salvatore; Sorrentino, Andrea; Ciambelli, Paolo; Neitzert, Heinrich C.

    2015-12-17

    Insulating materials play a vital role in the design and performance of electrical systems for both steady and transient state conditions. Among the other properties, also in this field, polymer nanocomposites promise to offer exciting improvements. Many studies in the last decade has witnessed significant developments in the area of nano-dielectric materials and significant effects of nano-scale fillers on electric, thermal and mechanical properties of polymeric materials have been observed. However, the developments of new and advanced materials to be used the miniaturization of electronic devices fabrication require extensive studies on electrical insulation characteristics of these materials before they can be used in commercial systems. In this work, Polystyrene (PS) composites were prepared by the blend solution method using MoS{sub 2}@Oleylamine nanosheets as filler. The dielectric properties of the resulting comoposite have been investigated at 300K and in the frequency range between 1000 Hz and 1 MHz. The addition of the MoS{sub 2}@Oleylamine nanosheets leads to a decreasing of the relative dielectric constant and of the electrical conductivity measured in the voltage range between ±500V. Thanks to a possibility to tune the electrical permittivity with the control of MoS{sub 2} concentration, these materials could be used as a low-dielectric material in the microelectronics applications.

  19. Simultaneous Noncontact Precision Imaging of Microstructural and Thickness Variation in Dielectric Materials Using Terahertz Energy

    NASA Technical Reports Server (NTRS)

    Roth, Donald J (Inventor)

    2011-01-01

    A process for simultaneously measuring the velocity of terahertz electromagnetic radiation in a dielectric material sample without prior knowledge of the thickness of the sample and for measuring the thickness of a material sample using terahertz electromagnetic radiation in a material sample without prior knowledge of the velocity of the terahertz electromagnetic radiation in the sample is disclosed and claimed. The process evaluates, in a plurality of locations, the sample for microstructural variations and for thickness variations and maps the microstructural and thickness variations by location. A thin sheet of dielectric material may be used on top of the sample to create a dielectric mismatch. The approximate focal point of the radiation source (transceiver) is initially determined for good measurements.

  20. 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

    NASA Astrophysics Data System (ADS)

    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.

  1. The effect of PECVD plasma decomposition on the wettability and dielectric constant changes in silicon modified DLC films for potential MEMS and low stiction applications

    SciTech Connect

    Ogwu, A. A.; Okpalugo, T. I. T.; McLaughlin, J. A. D.

    2012-09-15

    We have carried out investigations aimed at understanding the mechanism responsible for a water contact angle increase of up to ten degrees and a decrease in dielectric constant in silicon modified hydrogenated amorphous carbon films compared to unmodified hydrogenated amorphous carbon films. Our investigations based on surface chemical constituent analysis using Raman spectroscopy, x-ray photoelectron spectroscopy (XPS), SIMS, FTIR, contact angle / surface energy measurements and spectroscopic ellipsometry suggests the presence of hydrophobic chemical entities on the surface of the films. This observation is consistent with earlier theoretical plasma chemistry predictions and observed Raman peak shifts in the films. These surface hydrophobic entities also have a lower polarizability than the bonds in the un-modified films thereby reducing the dielectric constant of the silicon modified films measured by spectroscopic ellipsometry. Ellipsometric dielectric constant measurement is directly related to the surface energy through Hamaker's constant. Our current finding is expected to be of benefit to understanding stiction, friction and lubrication in areas that range from nano-tribology to microfluidics.

  2. Theoretical study on the dimerization of Si(OH) 4 in aqueous solution and its dependence on temperature and dielectric constant

    NASA Astrophysics Data System (ADS)

    Tossell, J. A.

    2005-01-01

    Energetics for the condensation dimerization reaction of monosilicic acid: 2Si(⇒SiOH+HO have been calculated quantum mechanically, in gas-phase and aqueous solution, over a range of temperatures and dielectric constants. The calculated gas phase energy, E g, for this reaction is -6.6 kcal/mol at the very accurate composite G2 level, but the vibrational, rotational and translational contributions to the free energy in the gas-phase, ΔG VRT, sum to + 2.5 kcal/mol and the hydration free energy contribution calculated with a polarizable continuum model, ΔΔG COSMO, for a dielectric constant of 78.5, is about + 6.2 kcal/mol. Thus, the free energy change for the reaction in aqueous solution at ambient conditions is about + 2.1 kcal/mol and the equilibrium constant is ˜10 -1.5, in reasonable agreement with experiment. As T increases, ΔG VRT increases slowly. As the dielectric constant decreases (for example, under high T and P conditions in the supercritical region), ΔΔG COSMO decreases substantially. Thus, at elevated T and P, if the effective dielectric constant of the aqueous fluid is 10 or less, the reaction becomes much more favorable, consistent with recent experimental observations. The PΔV contribution to the enthalpy is also considered, but cannot be accurately determined. We have also calculated 29Si-NMR shieldings and Raman frequencies for Si(OH) 4, Si 2O 7H 6 and some other oligomeric silicates. We correctly reproduce the separation of monomer and dimer peaks observed in the 29Si-NMR spectrra at ambient T and P. The Raman spectral data are somewhat ambiguous, and the new peaks seen at high T and P could arise either from the dimer or from a 3-ring trimer, which is calculated to be highly stabilized entropically at high T.

  3. Simultaneous Noncontact Precision Imaging of Microstructural and Thickness Variation in Dielectric Materials Using Terahertz Energy

    NASA Technical Reports Server (NTRS)

    Roth, Don J.; Seebo, Jeffrey P.; Winfree, William P.

    2008-01-01

    This article describes a noncontact single-sided terahertz electromagnetic measurement and imaging method that simultaneously characterizes microstructural (egs. spatially-lateral density) and thickness variation in dielectric (insulating) materials. The method was demonstrated for two materials-Space Shuttle External Tank sprayed-on foam insulation and a silicon nitride ceramic. It is believed that this method can be used as an inspection method for current and future NASA thermal protection system and other dielectric material inspection applications, where microstructural and thickness variation require precision mapping. Scale-up to more complex shapes such as cylindrical structures and structures with beveled regions would appear to be feasible.

  4. Fabrication of CuAl1-xMxO2 (M = Fe, Cr)/Ni film delafossite compounds using spin coating and their microstructure and dielectric constant

    NASA Astrophysics Data System (ADS)

    Diantoro, Markus; Yuwita, Pelangi Eka; Olenka, Desyana; Nasikhudin

    2014-09-01

    The discovery of delafossite compound has encouraged more rapid technological developments particularly in transparent electronic devices. Copper oxide-based transparent thin films delafossite semiconductor recently give much attention in the field of optoelectronic technology, after the discovery of p-type CuAlO2. The potential applications of a p-type semiconductor transparent conductive oxides (TCO) have been applied in broad field of optoelectronics. To explore a broad physical properties interms of magnetic conducting subtitution is understudied. In this work we report the fabrication of delafossite film on Ni substrate and their characterization of CuAl1-xMxO2 delafossite compounds doped with Cr3+ and Fe3+ from the raw material of Cu(NO3)2˙3H2O, Al(NO3)3˙9H2O, Fe(NO3)3˙9H2O and Cr(NO3)3˙9H2O. The films were prepared using spin coating through a sol-gel technique at various concentrations of x = 0, 0.03, 0.04, and 0.05 for chromium and x = 0, 0.02, 0.04, 0.06, and 0.08 for iron doped. Crystal and microstructure were characterized by means of Cu-Kα Bragg-Brentano X-RD followed by High Score Plus and SEM-EDAX. The dielectric constants of the films were characterized using LCR meter. It was found that the CuAl1-xMxO2/Ni delafossite films were successfully fabricated. The CuAl1-xFexO2 compound crystallized with lattice parameters of a = b ranged from 2.8603 Å to 2.8675 Å and c ranged from 16.9576 to 17.0763 Å. The increase of the dopant give rise to the increase of the lattice parameters. Since iron has bigger ionic radius (69 pm) than original site of Al3+ with radius of 53 pm the crystal volume lattice also increase. Further analyses of increasing volume of the crystal, as expected, affected to the decreasing of its dielectric constant. The similar trends also shown by Cr3+ doped of CuAl1-xCrxO2 films with smaller effects.

  5. Age-related changes in male forearm skin-to-fat tissue dielectric constant at 300 MHz.

    PubMed

    Mayrovitz, Harvey N; Grammenos, Alexandra; Corbitt, Kelly; Bartos, Simona

    2017-03-01

    Prior research suggests that tissue dielectric constant (TDC) values are useful to assess localized skin water in females for early diagnosing breast cancer treatment-related lymphoedema and TDC values in young adults have shown gender differences. However, no TDC data are available for older males nor have ageing effects been studied despite known shifts in water state and other skin age-related changes. Thus our goals were to (i) characterize TDC values at various skin depths in young and older males, (ii) determine the dependence of these values on body composition parameters and (iii) establish inter-arm TDC ratios for use as normal male reference values. TDC measurements were made to depths of 0·5, 1·5, 2·5 and 5·0 mm bilaterally on volar forearm skin in 60 males in three groups of 20 that had mean ages ± SD of 24·0 ± 0·9, 40·0 ± 12·9 and 71·0 ± 8·0 years. Total body fat and water percentages were determined via bioimpedance at 50 KHz. Results showed that (i) for all age groups TDC values decreased with increasing depth, (ii) TDC values were not statistically different among age groups except at a depth of 0·5 mm, (iii) TDC values were highly negatively correlated with total body fat and (iv) inter-arm ratios varied little among age groups and depths. It is concluded that (i) age-related larger TDC values at only the shallowest depth is consistent with skin water shifting state from bound to more mobile in the oldest group and (ii) inter-arm ratios at any depth provide a basis to test for unilateral oedema.

  6. Forearm skin tissue dielectric constant measured at 300 MHz: effect of changes in skin vascular volume and blood flow.

    PubMed

    Mayrovitz, Harvey N; Guo, Xiaoran; Salmon, Mark; Uhde, Matt

    2013-01-01

    Skin tissue dielectric constant (TDC) values measured via the open-ended coaxial probe method are useful non-invasive indices of local skin tissue water. However, the effect of skin blood flow (SBF) or skin blood volume (SBV) on TDC values is unknown. To determine the magnitude of such effects, we decreased forearm SBV via vertical arm raising for 5 min (test 1) and increased SBV by bicep cuff compression to 50 mmHg for 5 min (test 2) in 20 healthy supine subjects (10 men). TDC values were measured to a depth of 1·5 mm on anterior forearm, and SBF was measured with laser-Doppler system simultaneously on forearm and finger. Results indicate that decreasing vascular volume (test 1) was associated with a small but statistically significant reduction in TDC (3·0 ± 4·3%, P = 0·003) and increasing vascular volume (test 2) was associated with a slight but statistically significant increase in TDC (3·5 ± 3·0%, P<0·001). SBF changes depended on test and measurement site. For forearm, test 1 significantly increased SBF (102·6 ± 156·2%, P<0·001) and test 2 significantly decreased it (39·5 ± 13·1%, P<0·001). In finger, SBF was significantly reduced by both tests: in test 1 by 55·3 ± 32·1%, P<0·001 and in test 2 by 53·3 ± 27·6%, P<0·001. We conclude that the small percentage changes in TDC values (3·0-3·5%) over the wide range of induced SBV and SBF changes suggest a minor effect on clinically determined TDC values because of SBV or SBF changes or differences when comparing TDC longitudinally over time or among individuals of different groups in a research setting.

  7. Effect of Dielectric Materials on the Topological Insulator Bi2 Se 3 Surface States

    NASA Astrophysics Data System (ADS)

    Chang, Jiwon; Register, Leonard; Banerjee, Sanjay; Sahu, Bhagawan

    2011-03-01

    We study the effects of crystalline dielectric materials on the electronic surface states of a strong topological band insulator (TI) Bi 2 Se 3 using a density functional based electronic structure method [1]. We will discuss the sensitivity of Dirac point degeneracy and linear band dispersion of the TI with respect to different dielectric surface terminations as well as different relative atom positions of the dielectric and the TI. Both passivated and non-passivated substrate surfaces will be considered. Two representative dielectrics Si O2 and boron nitride will be chosen to understand the physics of interplay of interface potential, linear band dispersion and the chemical environments of the TI surface states. Our findings have implications in interpreting experiments and designing novel nanoelectronics device concepts based on TIs. ``Intrinsic and extrinsic perturbations on the surface states of topological insulator Bi 2 Se 3 ,'' J. Chang, P. Jadaun, L. F. Register, S. K. Banerjee and B. Sahu (In preparation)

  8. Characterization of full set material constants of piezoelectric materials based on ultrasonic method and inverse impedance spectroscopy using only one sample

    NASA Astrophysics Data System (ADS)

    Li, Shiyang; Zheng, Limei; Jiang, Wenhua; Sahul, Raffi; Gopalan, Venkatraman; Cao, Wenwu

    2013-09-01

    The most difficult task in the characterization of complete set material properties for piezoelectric materials is self-consistency. Because there are many independent elastic, dielectric, and piezoelectric constants, several samples are needed to obtain the full set constants. Property variation from sample to sample often makes the obtained data set lack of self-consistency. Here, we present a method, based on pulse-echo ultrasound and inverse impedance spectroscopy, to precisely determine the full set physical properties of piezoelectric materials using only one small sample, which eliminated the sample to sample variation problem to guarantee self-consistency. The method has been applied to characterize the [001]C poled Mn modified 0.27Pb(In1/2Nb1/2)O3-0.46Pb(Mg1/3Nb2/3)O3-0.27PbTiO3 single crystal and the validity of the measured data is confirmed by a previously established method. For the inverse calculations using impedance spectrum, the stability of reconstructed results is analyzed by fluctuation analysis of input data. In contrast to conventional regression methods, our method here takes the full advantage of both ultrasonic and inverse impedance spectroscopy methods to extract all constants from only one small sample. The method provides a powerful tool for assisting novel piezoelectric materials of small size and for generating needed input data sets for device designs using finite element simulations.

  9. Characterization of full set material constants of piezoelectric materials based on ultrasonic method and inverse impedance spectroscopy using only one sample.

    PubMed

    Li, Shiyang; Zheng, Limei; Jiang, Wenhua; Sahul, Raffi; Gopalan, Venkatraman; Cao, Wenwu

    2013-09-14

    The most difficult task in the characterization of complete set material properties for piezoelectric materials is self-consistency. Because there are many independent elastic, dielectric, and piezoelectric constants, several samples are needed to obtain the full set constants. Property variation from sample to sample often makes the obtained data set lack of self-consistency. Here, we present a method, based on pulse-echo ultrasound and inverse impedance spectroscopy, to precisely determine the full set physical properties of piezoelectric materials using only one small sample, which eliminated the sample to sample variation problem to guarantee self-consistency. The method has been applied to characterize the [001]C poled Mn modified 0.27Pb(In1/2Nb1/2)O3-0.46Pb(Mg1/3Nb2/3)O3-0.27PbTiO3 single crystal and the validity of the measured data is confirmed by a previously established method. For the inverse calculations using impedance spectrum, the stability of reconstructed results is analyzed by fluctuation analysis of input data. In contrast to conventional regression methods, our method here takes the full advantage of both ultrasonic and inverse impedance spectroscopy methods to extract all constants from only one small sample. The method provides a powerful tool for assisting novel piezoelectric materials of small size and for generating needed input data sets for device designs using finite element simulations.

  10. Parameter identification of material constants in a composite shell structure

    NASA Technical Reports Server (NTRS)

    Martinez, David R.; Carne, Thomas G.

    1988-01-01

    One of the basic requirements in engineering analysis is the development of a mathematical model describing the system. Frequently comparisons with test data are used as a measurement of the adequacy of the model. An attempt is typically made to update or improve the model to provide a test verified analysis tool. System identification provides a systematic procedure for accomplishing this task. The terms system identification, parameter estimation, and model correlation all refer to techniques that use test information to update or verify mathematical models. The goal of system identification is to improve the correlation of model predictions with measured test data, and produce accurate, predictive models. For nonmetallic structures the modeling task is often difficult due to uncertainties in the elastic constants. A finite element model of the shell was created, which included uncertain orthotropic elastic constants. A modal survey test was then performed on the shell. The resulting modal data, along with the finite element model of the shell, were used in a Bayes estimation algorithm. This permitted the use of covariance matrices to weight the confidence in the initial parameter values as well as confidence in the measured test data. The estimation procedure also employed the concept of successive linearization to obtain an approximate solution to the original nonlinear estimation problem.

  11. Agricultural wastes as a resource of raw materials for developing low-dielectric glass-ceramics

    NASA Astrophysics Data System (ADS)

    Danewalia, Satwinder Singh; Sharma, Gaurav; Thakur, Samita; Singh, K.

    2016-04-01

    Agricultural waste ashes are used as resource materials to synthesize new glass and glass-ceramics. The as-prepared materials are characterized using various techniques for their structural and dielectric properties to check their suitability in microelectronic applications. Sugarcane leaves ash exhibits higher content of alkali metal oxides than rice husk ash, which reduces the melting point of the components due to eutectic reactions. The addition of sugarcane leaves ash in rice husk ash promotes the glass formation. Additionally, it prevents the cristobalite phase formation. These materials are inherently porous, which is responsible for low dielectric permittivity i.e. 9 to 40. The presence of less ordered augite phase enhances the dielectric permittivity as compared to cristobalite and tridymite phases. The present glass-ceramics exhibit lower losses than similar materials synthesized using conventional minerals. The dielectric permittivity is independent to a wide range of temperature and frequency. The glass-ceramics developed with adequately devitrified phases can be used in microelectronic devices and other dielectric applications.

  12. Agricultural wastes as a resource of raw materials for developing low-dielectric glass-ceramics

    PubMed Central

    Danewalia, Satwinder Singh; Sharma, Gaurav; Thakur, Samita; Singh, K.

    2016-01-01

    Agricultural waste ashes are used as resource materials to synthesize new glass and glass-ceramics. The as-prepared materials are characterized using various techniques for their structural and dielectric properties to check their suitability in microelectronic applications. Sugarcane leaves ash exhibits higher content of alkali metal oxides than rice husk ash, which reduces the melting point of the components due to eutectic reactions. The addition of sugarcane leaves ash in rice husk ash promotes the glass formation. Additionally, it prevents the cristobalite phase formation. These materials are inherently porous, which is responsible for low dielectric permittivity i.e. 9 to 40. The presence of less ordered augite phase enhances the dielectric permittivity as compared to cristobalite and tridymite phases. The present glass-ceramics exhibit lower losses than similar materials synthesized using conventional minerals. The dielectric permittivity is independent to a wide range of temperature and frequency. The glass-ceramics developed with adequately devitrified phases can be used in microelectronic devices and other dielectric applications. PMID:27087123

  13. Agricultural wastes as a resource of raw materials for developing low-dielectric glass-ceramics.

    PubMed

    Danewalia, Satwinder Singh; Sharma, Gaurav; Thakur, Samita; Singh, K

    2016-04-18

    Agricultural waste ashes are used as resource materials to synthesize new glass and glass-ceramics. The as-prepared materials are characterized using various techniques for their structural and dielectric properties to check their suitability in microelectronic applications. Sugarcane leaves ash exhibits higher content of alkali metal oxides than rice husk ash, which reduces the melting point of the components due to eutectic reactions. The addition of sugarcane leaves ash in rice husk ash promotes the glass formation. Additionally, it prevents the cristobalite phase formation. These materials are inherently porous, which is responsible for low dielectric permittivity i.e. 9 to 40. The presence of less ordered augite phase enhances the dielectric permittivity as compared to cristobalite and tridymite phases. The present glass-ceramics exhibit lower losses than similar materials synthesized using conventional minerals. The dielectric permittivity is independent to a wide range of temperature and frequency. The glass-ceramics developed with adequately devitrified phases can be used in microelectronic devices and other dielectric applications.

  14. High dielectric constant associated with the strain-induced phase transition of an ordered assembly of BaTiO3 nanocubes under three-dimensional clamping

    NASA Astrophysics Data System (ADS)

    Yasui, Kyuichi; Mimura, Ken-ichi; Izu, Noriya; Kato, Kazumi

    2017-02-01

    Numerical calculations of the Gibbs function for an ordered assembly of BaTiO3 nanocubes (nanocrystals) under three-dimensional clamping have revealed that the phase transition from a tetragonal to cubic crystal structure can take place at room temperature at some misfit strain associated with a tilt angle of the attached nanocubes. The phase transition is second-order due to the three-dimensional clamping. Near and at the phase transition, the dielectric constant becomes extremely high owing to the second-order transition. This is considered to be the reason for the high dielectric constant of an assembly at room temperature, which has been experimentally observed. An ordered assembly of BaTiO3 nanocubes under rigid three-dimensional clamping is a completely different system from the normal nanocrystalline (polycrystalline) BaTiO3 ceramics under elastic clamping and from a BaTiO3 epitaxial thin film under two-dimensional clamping.

  15. Influence of the local structure in phase-change materials on their dielectric permittivity.

    PubMed

    Shportko, Kostiantyn V; Venger, Eugen F

    2015-01-01

    Ge-Sb-Te alloys, which belong to the phase-change materials, are promising materials for data storage and display and data visualization applications due to their unique properties. This includes a remarkable difference of their electrical and optical properties in the amorphous and crystalline state. Pronounced change of optical properties for Ge-Sb-Te alloys is linked to the different bonding types and different atomic arrangements in amorphous and crystalline states. The dielectric function of phase-change materials has been investigated in the far infrared (FIR) range. Phonons have been detected by FTIR spectroscopy. Difference of the dispersion of the dielectric permittivity of amorphous and crystalline samples is caused by different structures in different states which contribute to the dielectric permittivity.

  16. Role of anisotropy, spatially-varying effective mass, and dielectric constant on self-polarization effect of doped quantum dots in presence of noise

    NASA Astrophysics Data System (ADS)

    Ghosh, Anuja; Ghosh, Manas

    2017-04-01

    The profiles of self-polarization effect (SPE) of impurity doped GaAs quantum dot (QD) have been investigated under the governance of variable effective mass, variable dielectric constant and anisotropy of the system. Presence of noise has also been considered to inspect how it interplays with above parameters in modulating SPE. Noise term possesses a Gaussian white character and it has been introduced to the system via two different pathways; additive and multiplicative. The spatially-varying effective mass and spatially-varying dielectric constant mainly affect SPE quantitatively in comparison with the fixed ones. A changing anisotropy of the system also affects SPE. However, the extent to which SPE is being affected evidently depends on presence/absence of noise and also on the pathway through which noise has been applied. The findings of the study reveal authentic routes to tailor the SPE of doped QD system through the interplay between noise, anisotropy and spatially-varying effective mass and dielectric constant of the system.

  17. The stabilization effect of dielectric constant and acidic amino acids on arginine-arginine (Arg-Arg) pairings: database survey and computational studies.

    PubMed

    Zhang, Zhengyan; Xu, Zhijian; Yang, Zhuo; Liu, Yingtao; Wang, Jin'an; Shao, Qiang; Li, Shujin; Lu, Yunxiang; Zhu, Weiliang

    2013-05-02

    Database survey in this study revealed that about one-third of the protein structures deposited in the Protein Data Bank (PDB) contain arginine-arginine (Arg-Arg) pairing with a carbon···carbon (CZ···CZ) interaction distance less than 5 Å. All the Arg-Arg pairings were found to bury in a polar environment composed of acidic residues, water molecules, and strong polarizable or negatively charged moieties from binding site or bound ligand. Most of the Arg-Arg pairings are solvent exposed and 68.3% Arg-Arg pairings are stabilized by acidic residues, forming Arg-Arg-Asp/Glu clusters. Density functional theory (DFT) was then employed to study the effect of environment on the pairing structures. It was revealed that Arg-Arg pairings become thermodynamically stable (about -1 kcal/mol) as the dielectric constant increases to 46.8 (DMSO), in good agreement with the results of the PDB survey. DFT calculations also demonstrated that perpendicular Arg-Arg pairing structures are favorable in low dielectric constant environment, while in high dielectric constant environment parallel structures are favorable. Additionally, the acidic residues can stabilize the Arg-Arg pairing structures to a large degree. Energy decomposition analysis of Arg-Arg pairings and Arg-Arg-Asp/Glu clusters showed that both solvation and electrostatic energies contribute significantly to their stability. The results reported herein should be very helpful for understanding Arg-Arg pairing and its application in drug design.

  18. Non-Contact Measurement of Density and Thickness Variation in Dielectric Materials

    NASA Technical Reports Server (NTRS)

    Roth, Ron

    2009-01-01

    This non-contact, single-sided terahertz electromagnetic measurement and imaging method characterizes micro structural (e.g., spatially-lateral density) and thickness variation in dielectric (insulating) materials. This method was demonstrated for space shuttle external tank sprayed-on foam insulation and has been designed for use as an inspection method for current and future NASA thermal protection systems and other dielectric material inspection applications where no contact can be made with the sample due to fragility and it is impractical to use ultrasonic methods

  19. Thin-film composite materials as a dielectric layer for flexible metal-insulator-metal capacitors.

    PubMed

    Tiwari, Jitendra N; Meena, Jagan Singh; Wu, Chung-Shu; Tiwari, Rajanish N; Chu, Min-Ching; Chang, Feng-Chih; Ko, Fu-Hsiang

    2010-09-24

    A new organic-organic nanoscale composite thin-film (NCTF) dielectric has been synthesized by solution deposition of 1-bromoadamantane and triblock copolymer (Pluronic P123, BASF, EO20-PO70-EO20), in which the precursor solution has been achieved with organic additives. We have used a sol-gel process to make a metal-insulator-metal capacitor (MIM) comprising a nanoscale (10 nm-thick) thin-film on a flexible polyimide (PI) substrate at room temperature. Scanning electron microscope and atomic force microscope revealed that the deposited NCTFs were crack-free, uniform, highly resistant to moisture absorption, and well adhered on the Au-Cr/PI. The electrical properties of 1-bromoadamantane-P123 NCTF were characterized by dielectric constant, capacitance, and leakage current measurements. The 1-bromoadamantane-P123 NCTF on the PI substrate showed a low leakage current density of 5.5 x 10(-11) A cm(-2) and good capacitance of 2.4 fF at 1 MHz. In addition, the calculated dielectric constant of 1-bromoadamantane-P123 NCTF was 1.9, making them suitable candidates for use in future flexible electronic devices as a stable intermetal dielectric. The electrical insulating properties of 1-bromoadamantane-P123 NCTF have been improved due to the optimized dipole moments of the van der Waals interactions.

  20. Method for distributing chemicals through a fibrous material using low-headspace dielectric heating

    DOEpatents

    Banerjee, Sujit; Malcolm, Earl

    2002-01-01

    System and method for diffusing chemicals rapidly and evenly into and through fibrous material, such as wood. Chemicals are introduced into the fibrous material by applying the chemicals to the fibrous material. After treating the fibrous material with the chemicals, the fibrous material is maintained under low-headspace conditions. Thermal energy or dielectric heating, such as microwave or radio frequency energy, is applied to the fibrous material. As a result, the chemicals are able to distribute evenly and quickly throughout the fibrous material.

  1. Analysis of high voltage dielectric insulation materials of XLPE by THz-TDS system

    NASA Astrophysics Data System (ADS)

    Shi, Wei; Yan, Zhijin; Yang, Lei; Dai, Yang; Zhang, Like; Bian, Kangkang; Hou, Lei

    2015-11-01

    In this paper, cross-linked polyethylene (XLPE) was analyzed by THz time domain spectroscopy (TDS) system at room temperature. By recording time domain signal of terahertz radiation field, frequency spectrum can be obtained by Fourier transform. Then the refractive index and dielectric constant in THz band are calculated. This proves that the THz-TDS system has a potential application for detecting the aging characteristic of XLPE.

  2. Calculation of Dielectric Response in Molecular Solids for High Capacitance Organic Dielectrics

    NASA Astrophysics Data System (ADS)

    Heitzer, Henry Matthew

    with experiment. This method is then used to help design new high-capacitance molecular dielectrics by determining what materials and chemical properties are important in maximizing dielectric response in Self-Assembled Monolayers (SAMs). Highly (hyper)polarizable Donor-Bridge-Acceptor (DBA) molecular materials are shown to have remarkable dielectric responses. Lastly, the interplay between charge conduction and dielectric constant is examined and it is demonstrated that high dielectric constant materials with low conductance are achievable through molecular design. This technique is a powerful tool for understanding and designing molecular dielectric systems, whose properties are fundamental in many scientific pursuits.

  3. Dielectric Characteristics of Microstructural Changes and Property Evolution in Engineered Materials

    NASA Astrophysics Data System (ADS)

    Clifford, Jallisa Janet

    Heterogeneous materials are increasingly used in a wide range of applications such as aerospace, civil infrastructure, fuel cells and many others. The ability to take properties from two or more materials to create a material with properties engineered to needs is always very attractive. Hence heterogeneous materials are evolving into more complex formulations in multiple disciplines. Design of microstructure at multiple scales control the global functional properties of these materials and their structures. However, local microstructural changes do not directly cause a proportional change to the global properties (such as strength and stiffness). Instead, local changes follow an evolution process including significant interactions. Therefore, in order to understand property evolution of engineered materials, microstructural changes need to be effectively captured. Characterizing these changes and representing them by material variables will enable us to further improve our material level understanding. In this work, we will demonstrate how microstructural features of heterogeneous materials can be described quantitatively using broadband dielectric spectroscopy (BbDS). The frequency dependent dielectric properties can capture the change in material microstructure and represent these changes in terms of material variables, such as complex permittivity. These changes in terms of material properties can then be linked to a number of different conditions, such as increasing damage due to impact or fatigue. Two different broadband dielectric spectroscopy scanning modes are presented: bulk measurements and continuous scanning to measure dielectric property change as a function of position across the specimen. In this study, we will focus on ceramic materials and fiber reinforced polymer matrix composites as test bed material systems. In the first part of the thesis, we will present how different micro-structural design of porous ceramic materials can be captured

  4. Enhanced dielectric constant and relaxor behavior realized by dual stage sintering of Sr0.5Ba0.5Nb2O6

    NASA Astrophysics Data System (ADS)

    Rathore, Satyapal S.; Vitta, Satish

    2014-04-01

    The relaxor ferroelectric compound, Sr0.5Ba0.5Nb2O6 (SBN50) was synthesized by solid state reaction followed by sintering under two different conditions: single and dual stage sintering. The impact of sintering process on structural and dielectric properties has been studied in detail using X-ray diffraction, scanning electron microscopy and broadband dielectric spectroscopy. The crystal structure determined by performing Rietveld refinement of X-ray diffractogram was found to be identical in both cases. SBN50 crystallizes in the ferroelectric tetragonal tungsten bronze, P4bm structure. It was observed that uniform grain growth can be controlled by dual stage sintering and relatively narrow distribution of grains can be achieved with an average grain size of ˜15 μm. The dielectric studies show that SBN50 exhibits a relaxor ferroelectric behavior with the transformation taking place at ˜ 380 K due to formation of polar nano regions. Although both single and dual stage sintered SBN50 exhibits relaxor behaviour, the maximum dielectric constant of dual stage sintered SBN50 is found to be 1550 compare to 1440 for single stage sintering.

  5. [111]-oriented PIN-PMN-PT crystals with ultrahigh dielectric permittivity and high frequency constant for high-frequency transducer applications

    NASA Astrophysics Data System (ADS)

    Li, Fei; Zhang, Shujun; Luo, Jun; Geng, Xuecang; Xu, Zhuo; Shrout, Thomas R.

    2016-08-01

    The electromechanical properties of [111]-oriented tetragonal Pb(In1/2Nb1/2O3)-Pb(Mg1/3Nb2/3O3)-PbTiO3 (PIN-PMN-PT) crystals were investigated for potential high frequency ultrasonic transducers. The domain-engineered tetragonal crystals exhibit an ultrahigh free dielectric permittivity ɛ33T > 10 000 with a moderate electromechanical coupling factor k33 ˜ 0.79, leading to a high clamped dielectric permittivity ɛ33S of 2800, significantly higher than those of the rhombohedral relaxor-PT crystals and high-K (dielectric permittivity) piezoelectric ceramics. Of particular significance is that the [111]-oriented tetragonal crystals were found to possess high elastic stiffness, with frequency constant N33 of ˜2400 Hz m, allowing relatively easy fabrication of high-frequency transducers. In addition, no scaling effect of piezoelectric and dielectric properties was observed down to thickness of 0.1 mm, corresponding to an operational frequency of ˜24 MHz. These advantages of [111]-oriented tetragonal PIN-PMN-PT crystals will benefit high-frequency ultrasonic array transducers, allowing for high sensitivity, broad bandwidth, and reduced noise/crosstalk.

  6. Initial Estimates of Optical Constants of Mars Candidate Materials

    NASA Technical Reports Server (NTRS)

    Rousch, Ted L.; Brown, Adrian Jon; Bishop, Janice L.; Blake, David F.; Bristow, Thomas F.

    2013-01-01

    Data obtained at visible and near-infrared wavelengths by OMEGA on Mars Express and CRISM on MRO provide definitive evidence for the presence of phyllosilicates and other hydrated phases on Mars. A diverse range of both Fe/Mg-OH and Al- OH-bearing phyllosilicates were identified including the smectites, nontronite, saponite, and montmorillonite. To constrain the abundances of these phyllosilicates, spectral analyses of mixtures are needed. We report on our effort to enable the quantitative evaluation of the abundance of hydrated-hydroxylated silicates when they are contained in mixtures. We include two component mixtures of hydrated/ hydroxylated silicates with each other and with two analogs for other Martian materials; pyroxene (enstatite) and palagonitic soil (an alteration product of basaltic glass, hereafter referred to as palagonite). For the hydrated-hydroxylated silicates we include saponite and montmorillonite (Mg- and Al-rich smectites). We prepared three size separates of each end-member for study: 20-45, 63-90, and 125-150 micron.

  7. Thin-ribbon tapered coupler for dielectric waveguides

    NASA Technical Reports Server (NTRS)

    Yeh, C.; Otoshi, T. Y.; Shimabukuro, F. I.

    1994-01-01

    A recent discovery shows that a high-dielectric constant, low-loss, solid material can be made into a ribbon-like waveguide structure to yield an attenuation constant of less than 0.02 dB/m for single-mode guidance of millimeter/submillimeter waves. One of the crucial components that must be invented in order to guarantee the low-loss utilization of this dielectric-waveguide guiding system is the excitation coupler. The traditional tapered-to-a-point coupler for a dielectric rod waveguide fails when the dielectric constant of the dielectric waveguide is large. This article presents a new way to design a low-loss coupler for a high- or low-dielectric constant dielectric waveguide for millimeter or submillimeter waves.

  8. Control of spontaneous emission of quantum dots using correlated effects of metal oxides and dielectric materials.

    PubMed

    Sadeghi, S M; Wing, W J; Gutha, R R; Capps, L

    2017-03-03

    We study the emission dynamics of semiconductor quantum dots in the presence of the correlated impact of metal oxides and dielectric materials. For this we used layered material structures consisting of a base substrate, a dielectric layer, and an ultrathin layer of a metal oxide. After depositing colloidal CdSe/ZnS quantum dots on the top of the metal oxide, we used spectral and time-resolved techniques to show that, depending on the type and thickness of the dielectric material, the metal oxide can characteristically change the interplay between intrinsic excitons, defect states, and the environment, offering new material properties. Our results show that aluminum oxide, in particular, can strongly change the impact of amorphous silicon on the emission dynamics of quantum dots by balancing the intrinsic near band emission and fast trapping of carriers. In such a system the silicon/aluminum oxide charge barrier can lead to large variation of the radiative lifetime of quantum dots and control of the photo-ejection rate of electrons in quantum dots. The results provide unique techniques to investigate and modify physical properties of dielectrics and manage optical and electrical properties of quantum dots.

  9. Method for imaging liquid and dielectric materials with scanning polarization force microscopy

    DOEpatents

    Hu, J.; Ogletree, D.F.; Salmeron, M.; Xiao, X.

    1999-03-09

    The invention images dielectric polarization forces on surfaces induced by a charged scanning force microscope (SFM) probe tip. On insulators, the major contribution to the surface polarizability at low frequencies is from surface ions. The mobility of these ions depends strongly on the humidity. Using the inventive SFM, liquid films, droplets, and other weakly adsorbed materials have been imaged. 9 figs.

  10. Apparatus for imaging liquid and dielectric materials with scanning polarization force microscopy

    DOEpatents

    Hu, J.; Ogletree, D.F.; Salmeron, M.; Xiao, X.

    1998-04-28

    The invention images dielectric polarization forces on surfaces induced by a charged scanning force microscope (SFM) probe tip. On insulators, the major contribution to the surface polarizability at low frequencies is from surface ions. The mobility of these ions depends strongly on the humidity. Using the inventive SFM, liquid films, droplets, and other weakly adsorbed materials have been imaged. 9 figs.

  11. Apparatus for imaging liquid and dielectric materials with scanning polarization force microscopy

    DOEpatents

    Hu, Jun; Ogletree, D. Frank; Salmeron, Miguel; Xiao, Xudong

    1998-01-01

    The invention images dielectric polarization forces on surfaces induced by a charged scanning force microscope (SFM) probe tip. On insulators, the major contribution to the surface polarizability at low frequencies is from surface ions. The mobility of these ions depends strongly on the humidity. Using the inventive SFM, liquid films, droplets, and other weakly adsorbed materials have been imaged.

  12. Method for imaging liquid and dielectric materials with scanning polarization force microscopy

    DOEpatents

    Hu, Jun; Ogletree, D. Frank; Salmeron, Miguel; Xiao, Xudong

    1999-01-01

    The invention images dielectric polarization forces on surfaces induced by a charged scanning force microscope (SFM) probe tip. On insulators, the major contribution to the surface polarizability at low frequencies is from surface ions. The mobility of these ions depends strongly on the humidity. Using the inventive SFM, liquid films, droplets, and other weakly adsorbed materials have been imaged.

  13. Control of spontaneous emission of quantum dots using correlated effects of metal oxides and dielectric materials

    NASA Astrophysics Data System (ADS)

    Sadeghi, S. M.; Wing, W. J.; Gutha, R. R.; Capps, L.

    2017-03-01

    We study the emission dynamics of semiconductor quantum dots in the presence of the correlated impact of metal oxides and dielectric materials. For this we used layered material structures consisting of a base substrate, a dielectric layer, and an ultrathin layer of a metal oxide. After depositing colloidal CdSe/ZnS quantum dots on the top of the metal oxide, we used spectral and time-resolved techniques to show that, depending on the type and thickness of the dielectric material, the metal oxide can characteristically change the interplay between intrinsic excitons, defect states, and the environment, offering new material properties. Our results show that aluminum oxide, in particular, can strongly change the impact of amorphous silicon on the emission dynamics of quantum dots by balancing the intrinsic near band emission and fast trapping of carriers. In such a system the silicon/aluminum oxide charge barrier can lead to large variation of the radiative lifetime of quantum dots and control of the photo-ejection rate of electrons in quantum dots. The results provide unique techniques to investigate and modify physical properties of dielectrics and manage optical and electrical properties of quantum dots.

  14. Polymer dielectric materials for organic thin-film transistors: Interfacial control and development for printable electronics

    NASA Astrophysics Data System (ADS)

    Kim, Choongik

    Organic thin-film transistors (OTFTs) have been extensively studied for organic electronics. In these devices, organic semiconductor-dielectric interface characteristics play a critical role in influencing OTFT operation and performance. This study begins with exploring how the physicochemical characteristics of the polymer gate dielectric affects the thin-film growth mode, microstructure, and OTFT performance parameters of pentacene films deposited on bilayer polymer (top)-SiO2 (bottom) dielectrics. Pentacene growth mode varies considerably with dielectric substrate, and correlations are established between pentacene film deposition temperature, the thin-film to bulk microstructural phase transition, and OTFT device performance. Furthermore, the primary influence of the polymer dielectric layer glass transition temperature on pentacene film microstructure and OTFT response is shown for the first time. Following the first study, the influence of the polymer gate dielectric viscoelastic properties on overlying organic semiconductor film growth, film microstructure, and TFT response are investigated in detail. From the knowledge that nanoscopically-confined thin polymer films exhibit glass transition temperatures that deviate substantially from those of the corresponding bulk materials, pentacene (p-channel) and cyanoperylene (n-channel) films grown on polymer gate dielectrics at temperatures well-below their bulk glass transition temperatures (Tg(b)) have been shown to exhibit morphological/microstructural transitions and dramatic OTFT performance discontinuities at well-defined temperatures (defined as the polymer "surface glass transition temperature," or Tg(s)). These transitions are characteristic of the particular polymer architecture and independent of film thickness or overall film cooperative chain dynamics. Furthermore, by analyzing the pentacene films grown on UV-curable polymer dielectrics with different curing times (hence, different degrees of

  15. Evolution of surface-plasmon-polariton and Dyakonov-Tamm waves with the ambichirality of a partnering dielectric material

    NASA Astrophysics Data System (ADS)

    Faryad, Muhammad; Lakhtakia, Akhlesh

    2014-01-01

    The planar interface of an isotropic homogeneous metal and an ambichiral dielectric material can guide surface-plasmon-polariton (SPP) waves. The planar interface of an isotropic, homogeneous dielectric material and an ambichiral dielectric material can guide Dyakonov-Tamm waves. In either instance, we found that, as the ambichiral partnering material evolves into a finely chiral material, the solutions of the dispersion equation for surface-wave propagation evince convergence. The convergence is faster for Dyakonov-Tamm waves than for SPP waves.

  16. Dielectric engineered symmetric underlap double gate tunnel FET (DGTFET): An investigation towards variation of dielectric materials

    NASA Astrophysics Data System (ADS)

    Mallikarjunarao; Ranjan, Rajeev; Pradhan, K. P.; Sahu, P. K.

    2016-08-01

    In this article, an underlap silicon n-channel Tunnel Field Effect Transistor (n-TFET) i.e., symmetric single-k spacer (SSS) Double Gate N-TFET (DGTFET) is proposed to improve the performance of the device by using different spacer materials. A detailed investigation has been made on the proposed device characteristics with the help of extensive 2-D TCAD simulations. It is demonstrated that an optimized underlap length is chosen for a significant on-state current (Ion) without deteriorating the off-state current (Ioff) and sub-threshold swing (SS). The proposed model with different spacer materials has been extensively analyzed by using transfer characteristics, output characteristics, and analog/RF characteristics. The structure is optimized based on the comparison among various performance metrics like Ion, Ioff, SS, on-off ratio (Ion/Ioff), threshold (or) cut-off frequency (fT), and intrinsic delay with considering different spacer materials like SiO2 (k = 3.9), Si3N4 (k = 7.5), and HfO2 (k = 25).

  17. Integration of polytetrafluoroethylene low-k dielectric material in a chemical vapor deposited aluminum metallization scheme

    NASA Astrophysics Data System (ADS)

    Wickland, Heidi Lee

    In order to increase speed and functionality, computer chip technology continues its evolution towards higher device density and reduced feature size. As interconnect signal delay has become prohibitively high for traditional Al/SiO2 architectures, there is a pressing need to pursue integration of low-k materials into back-end-of-the-line interconnect architectures. To this end, polytetrafluoroethylene (PTFE) was integrated with aluminum, implementing titanium nitride as a barrier layer. SPEEDFILM, a version of PTFE, has a low dielectric constant of 1.9--2.0. With the use of an adhesion promoter, SPEEDFILM can be easily spun-cast onto patterned aluminum substrates, allowing for implementation into existing interconnect process flows. CVD aluminum/PVD TiN binary stacks have been successfully grown on spin-cast films of PTFE. Elemental analysis revealed compositionally pure aluminum, showing virtually no fluorine contamination in as-deposited and annealed binary stacks, and resistivity as low as 3.2 muO-cm have been obtained. Thermal annealing studies indicate titanium nitride is an effective barrier against thermally-driven fluorine diffusion from PTFE. A fabrication flow for a two-level Al/PTFE test structure was identified in order to examine key integration issues and produce an electrically testable demonstration vehicle. Many integration milestones have been met. In particular, XPS studies of plasma-treated PTFE surfaces demonstrated that an NH3 plasma can defluorinate the PTFE surface, allowing sufficient adhesion of a subsequently-deposited SiO2 cap to survive chemical-mechanical polishing. First pass work also indicated promising etching and photoresist stripping results of SiO2/PTFE stacks, which are designed for use at the via level of this two-level structure. This is a particularly useful result since low-k dielectrics are often difficult to pattern due to their degradation upon exposure to traditional photoresist stripping chemistries. Finally, in

  18. Derivation of extracellular fluid volume fraction and equivalent dielectric constant of the cell membrane from dielectric properties of the human body. Part 2: A preliminary study for tracking the progression of surgical tissue injury.

    PubMed

    Tatara, T; Tsuzaki, K

    2000-07-01

    A study is conducted to determine whether the extracellular fluid (ECF) volume fraction and equivalent dielectric constant of the cell membrane epsilon m, derived from the dielectric properties of the human body can track the progression of surgical tissue injury. Frequency-dependent dielectric constants and electrical conductivities of body segments are obtained at surgical (trunk) and non-surgical sites (arm and leg) from five patients who have undergone oesophageal resections, before and at the end of surgery and on the day after the operation. The ECF volume fraction and the equivalent epsilon m of body segments are estimated by fitting the dielectric data for body segments to the cell suspension model incorporating fat tissue, and their time-course changes are compared between body segments. By the day after the operation, the estimated ECF volume fraction has increased in all body segments compared with that before surgery, by 0.13 in the arm, 0.16 in the trunk and 0.14 in the leg (p < 0.05), indicating postoperative fluid accumulation in the extracellular space. In contrast, the estimated equivalent epsilon m shows a different time course between body segments on the day after the operation, characterised by a higher change ratio of epsilon m of the trunk (1.34 +/- 0.66, p < 0.05), from that of the arm (0.66 +/- 0.34) and leg (0.61 +/- 0.11). The results suggest that the equivalent epsilon m of a body segment at a surgical site can track pathophysiological cell changes following surgical tissue injury.

  19. High-index dielectric meta-materials for near-perfect broadband reflectors

    NASA Astrophysics Data System (ADS)

    Liu, Zhengqi; Liu, Xiaoshan; Wang, Yan; Pan, Pingping

    2016-05-01

    All-dielectric meta-materials offer a potential alternative to plasmonic meta-materials at optical frequencies. Herein, we take advantage of loss-less as well as simple unit cell geometry to demonstrate near-perfect broadband reflectors made from all-dielectric materials. These near-perfect reflectors, consisting of high-index cross-shaped resonators (n  =  3.5, Si), operating in the telecommunications bands, exhibit novel optical properties including polarization-independent, wide-angle near-unity reflection. The average reflectance is exceeding 98% at the wavelength range from 1.261 μm to 1.533 μm. At 1.310 μm, the average reflectance (R) reaches 99.7%, surpassing the reflectance of metallic mirrors. A near-perfect super-broadband reflection spectrum with bandwidth of 0.330 μm (R  >  98%) is achieved for a system with a higher index dielectric resonator array (n  =  4.0, Ge). Moreover, the optical properties of the reflector provide high scalability across the wavelength range via tuning of dielectric resonators. The whole structure, with common triple-layer features, can be mass-produced using standard lithography methods and deposition techniques. These optical and structural features make the proposed near-perfect broadband reflectors feasible avenues for manipulating light in important applications in spectroscopy, photovoltaics and light emission.

  20. Development of Dielectric Elastomer Nanocomposites as Stretchable and Flexible Actuating Materials

    NASA Astrophysics Data System (ADS)

    Wang, Yu

    Dielectric elastomers (DEs) are a new type of smart materials showing promising functionalities as energy harvesting materials as well as actuating materials for potential applications such as artificial muscles, implanted medical devices, robotics, loud speakers, micro-electro-mechanical systems (MEMS), tunable optics, transducers, sensors, and even generators due to their high electromechanical efficiency, stability, lightweight, low cost, and easy processing. Despite the advantages of DEs, technical challenges must be resolved for wider applications. A high electric field of at least 10-30 V/um is required for the actuation of DEs, which limits the practical applications especially in biomedical fields. We tackle this problem by introducing the multiwalled carbon nanotubes (MWNTs) in DEs to enhance their relative permittivity and to generate their high electromechanical responses with lower applied field level. This work presents the dielectric, mechanical and electromechanical properties of DEs filled with MWNTs. The micromechanics-based finite element models are employed to describe the dielectric, and mechanical behavior of the MWNT-filled DE nanocomposites. A sufficient number of models are computed to reach the acceptable prediction of the dielectric and mechanical responses. In addition, experimental results are analyzed along with simulation results. Finally, laser Doppler vibrometer is utilized to directly detect the enhancement of the actuation strains of DE nanocomposites filled with MWNTs. All the results demonstrate the effective improvement in the electromechanical properties of DE nanocomposites filled with MWNTs under the applied electric fields.

  1. Comparison of dielectric materials for the activation of a macro-scale hinge configuration

    NASA Astrophysics Data System (ADS)

    Jordi, C.; Schmidt, A.; Kovacs, G.; Ermanni, Paolo

    2011-04-01

    While much of the research on dielectric elastomer actuators used to concentrate on VHB 4910 as dielectric material, lately many new, specifically developed materials have come into focus. The acrylic VHB has been thoroughly characterized in a macro-scale agonist-antagonist configuration on an active hinge. This was carried out with the aim of using it on an airship, which was activated, undulating body and a fin and thus propelled in a fish-like manner. The concept was proved in flight, but still lifetime and viscosity of the actuators and the time-costing fabrication due to the necessary large pre-stretches of the dielectric membrane caused severe inconveniences. In order to evaluate the usability of other materials for this specific purpose, two other materials, a corrugated silicone with silver electrodes (by PolyPower) and an acrylic with interpenetrating network (IPN) developed by Pei et al. were characterized under similar conditions. The influence of the material on performance and design of the actuators and the conclusions for the use of the materials on the airship (and on applications with similar performance requirements) are presented.

  2. Environmental effects on electron transfer from chlorophyll triplet to quinone: role of dielectric constant, viscosity and quinone structure in cellulose acetate films

    SciTech Connect

    Cheddar, G.; Tollin, G.

    1981-01-01

    The effects of environmental parameters on chlorophyll triplet quenching and electron transfer to quinones have been investigated in a system consisting of donor and acceptor incorporated into a cellulose acetate film which was subsequently exposed to solvent. Triplet quenching by a diffusional mechanism was found to occur in the dry film, with steric effects being a major determinant of quencher effectiveness. No formation of separated radicals was found under these conditions, probably because the high viscosity prevented separation of the initially formed radical-ion pair. When the film was subsequently exposed to water, triplet quenching became more effective and separated radical production occurred. This is attributed to effects of decreased microviscosity and increased dielectric constant. Both steric effects and quinone redox potential were found to influence radical yields. Rate constants for reverse electron transfer were independent of quinone redox potential. When solvents other than pure water were used, radical yields were observed to increase with the dielectric constant. This is ascribed to an increase in the ease of separation of the radical-ion pair.

  3. A concept for the intrinsic dielectric strength of electrical insulation materials

    NASA Astrophysics Data System (ADS)

    Cuddihy, E. F.

    1985-04-01

    A concept is described for a possible definition of the intrinsic dielectric strength of insulating materials, which can be considered as a fundamental material property similar to other material properties, such as Young's modulus, index of refraction, and expansion coefficients. The events leading to the recognition of this property are reported, and the property is defined. This intrinsic dielectric strength concept should facilitate interpretation of results from accelerated and/or natural aging programs intended to predict electrical insulation service life of encapsulants in photovoltaic modules. As a practical application, this new concept enabled a possible explanation of the cause of failures in buried high-voltage cable with polyethylene insulation, and a possible explanation of the causes of electrical trees in polyethylene; these also are described.

  4. One-Dimensional Dielectric/Metallic Hybrid Materials for Photonic Applications.

    PubMed

    Li, Yong Jun; Xiong, Xiao; Zou, Chang-Ling; Ren, Xi Feng; Zhao, Yong Sheng

    2015-08-01

    Explorations of 1D nanostructures have led to great progress in the area of nanophotonics in the past decades. Based on either dielectric or metallic materials, a variety of 1D photonic devices have been developed, such as nanolasers, waveguides, optical switches, and routers. What's interesting is that these dielectric systems enjoy low propagation losses and usually possess active optical performance, but they have a diffraction-limited field confinement. Alternatively, metallic systems can guide light on deep subwavelength scales, but they suffer from high metallic absorption and can work as passive devices only. Thus, the idea to construct a hybrid system that combines the merits of both dielectric and metallic materials was proposed. To date, unprecedented optical properties have been achieved in various 1D hybrid systems, which manifest great potential for functional nanophotonic devices. Here, the focus is on recent advances in 1D dielectric/metallic hybrid systems, with a special emphasis on novel structure design, rational fabrication techniques, unique performance, as well as their wide application in photonic components. Gaining a better understanding of hybrid systems would benefit the design of nanophotonic components aimed at optical information processing.

  5. Anomalous change in dielectric constant of CaCu{sub 3}Ti{sub 4}O{sub 12} under violet-to-ultraviolet irradiation

    SciTech Connect

    Masingboon, C.; Eknapakul, T.; Suwanwong, S.; Buaphet, P.; Nakajima, H.; Mo, S.-K.; Thongbai, P.; King, P. D. C.; Maensiri, S.; Meevasana, W.

    2013-05-20

    The influence of light illumination on the dielectric constant of CaCu{sub 3}Ti{sub 4}O{sub 12} (CCTO) polycrystals is studied in this work. When exposed to 405-nm laser light, a reversible enhancement in the room temperature capacitance as high as 22% was observed, suggesting application of light-sensitive capacitance devices. To uncover the microscopic mechanisms mediating this change, we performed electronic structure measurements, using photoemission spectroscopy, and measured the electrical conductivity of the CCTO samples under different conditions of light exposure and oxygen partial pressure. Together, these results suggest that the large capacitance enhancement is driven by oxygen vacancies induced by the irradiation.

  6. A pseudoreceptor docking study of 4,5-α-epoxymorphinans with a range of dielectric constants

    NASA Astrophysics Data System (ADS)

    Gussio, Rick; Pou, Sovitj; Chen, Jih-Hsiang; Smythers, Gary W.

    1992-04-01

    Thirteen 4,5-epoxymorphinan μ agonists with established analgesic action were docked into an Asp-Lys-His-Phe pseudoreceptor complex under a range of distance-dependent dielectric conditions. The number of compounds with potential energies of the docked complexes that agreed in rank order with corresponding analgesic potencies was determined for each condition. Two dielectric conditions, n-decane (1.991) and ethanol (24.3), enabled the greatest number of compounds to relate to their pseudoreceptors with each having 9 and 8 successes respectively. Both of these conditions demonstrated unique influences on the types of structures that were successfully docked. For example, the morphine stereoisomer α-isomorphine, the geometric isomer B/C trans-morphine, and the 8-position-substituted γ-isomorphine were successes in the n-decane condition, whereas the ethanol condition produced the substituted codeine derivatives dihydroco-deinone and dihydroxycodeinone. These findings emphasize the importance of dielectric influence when developing force-field modeled quantitative structure-activity relationships for a closely related homologous series.

  7. Microwave-Assisted Synthesis of High Dielectric Constant CaCu3Ti4O12 from Sol-Gel Precursor

    NASA Astrophysics Data System (ADS)

    Ouyang, Xin; Cao, Peng; Huang, Saifang; Zhang, Weijun; Huang, Zhaohui; Gao, Wei

    2015-07-01

    CaCu3Ti4O12 (CCTO) powders derived from sol-gel precursors were calcined and sintered via microwave radiation. The obtained CCTO powders were compared with that obtained via a conventional heating method. For microwave heating, 89.1 wt.% CCTO was achieved from the sol-gel precursor, after only 17 min at 950°C. In contrast, the conventional calcination method required 3 h to generate 87.6 wt.% CCTO content at 1100°C. In addition, the CCTO powders prepared through 17 min of microwave calcination exhibited a small particle size distribution of D50 = 3.826 μm. It was found that a lengthy hold time of 1 h by microwave sintering is required to obtain a high dielectric constant (3.14 × 103 at 102 Hz) and a reasonably low dielectric loss (0.161) in the sintered CCTO ceramic. Based upon the distinct microstructures, the dielectric responses of the CCTO samples sintered by different methods are attributed to space charge polarization and internal barrier layer capacitor mechanism.

  8. Dielectric and magnetic studies of BaTi0.5Fe0.5O3 ceramic materials, synthesized by solid state sintering

    NASA Astrophysics Data System (ADS)

    Samuvel, K.; Ramachandran, K.

    2015-02-01

    A comparative study of the surface morphology, dielectric and magnetic properties of the BaTi0.5Fe0.5O3 (BTFO) ceramics materials. This has been carried out by synthesizing the samples in different routes. BTFO samples have shown single phased 12R type hexagonal structure with R 3m ‾ , P4mm space group. Interfacial effects on the dielectric properties of the samples have been understood by Cole-Cole plots in complex impedance and modulus formalism. It has been identified that huge dielectric constant (103-106) at lower frequencies is largely contributed by the heterogeneous electronic microstructure at the interfaces of grains. Modulus formalism has identified the effects of both grain and grain boundary microstructure on the dielectric properties, particularly in chemical routed samples. The order of grain boundary resistivity suggests the semiconductor/insulator class of the material. The grain boundary resistivity of the mechanical alloyed samples is remarkably lower than the solid state and chemical routed samples. Few samples have of the samples have exhibited signature of ferromagnetism at the room temperature.

  9. Dielectric and magnetic studies of BaTi0.5Fe0.5O3 ceramic materials, synthesized by solid state sintering.

    PubMed

    Samuvel, K; Ramachandran, K

    2015-02-05

    A comparative study of the surface morphology, dielectric and magnetic properties of the BaTi0.5Fe0.5O3 (BTFO) ceramics materials. This has been carried out by synthesizing the samples in different routes. BTFO samples have shown single phased 12R type hexagonal structure with R3m, P4mm space group. Interfacial effects on the dielectric properties of the samples have been understood by Cole-Cole plots in complex impedance and modulus formalism. It has been identified that huge dielectric constant (10(3)-10(6)) at lower frequencies is largely contributed by the heterogeneous electronic microstructure at the interfaces of grains. Modulus formalism has identified the effects of both grain and grain boundary microstructure on the dielectric properties, particularly in chemical routed samples. The order of grain boundary resistivity suggests the semiconductor/insulator class of the material. The grain boundary resistivity of the mechanical alloyed samples is remarkably lower than the solid state and chemical routed samples. Few samples have of the samples have exhibited signature of ferromagnetism at the room temperature.

  10. Thermal aspects of laser-based measurement and ultrafast laser processing of dielectric materials

    NASA Astrophysics Data System (ADS)

    Fan, Ching-Hua

    Two extreme regimes for laser applications on dielectric materials are presented in this dissertation. First, two independent novel techniques that use low power laser light to make precision non-contact measurement of liquids are introduced: (1) real-time concentration measurement of NaCl-H2O and MgCl2-H2O aqueous mixtures in a flowing system, and (2) temperature or concentration measurements of liquids, including water, ethanol, methanol, 1-proponal, and their mixtures, at a free surface as well as a solid-liquid interface. These measurement techniques exhibit very high spatial and temporal resolutions, making them good candidates for use in microscale and MEMS-based measurement technologies. Another extreme of laser applications is materials processing using high power ultrashort laser pulses, which exhibits exciting new opportunities for non-contact materials modification with high precision and high feature quality. The second part of this dissertation focuses on modeling the interactions between ultrashort laser pulses and dielectrics. Present models effectively characterize several dominant parameters during ultrafast laser processing of dielectrics. Good agreement has been found between the model predictions and the experimental results. Future research will be directed towards the utilization of these model predictions to enhance energy deposition and material removal rate during ultrafast laser processing, improve machined features, and optimize technologies that involve laser-microstructures fabrication.

  11. THz - ToF Optical Layer Analysis (OLA) to determine optical properties of dielectric materials

    NASA Astrophysics Data System (ADS)

    Spranger, Holger; Beckmann, Jörg

    2017-02-01

    Electromagnetic waves with frequencies between 0.1 and 10 THz are described as THz-radiation (T-ray). The ability to penetrate dielectric materials makes T-rays attractive to reveal discontinuities in polymer and ceramic materials. THz-Time Domain Spectroscopy Systems (THz-TDS) are available on the market today which operates with THz-pulses transmitted and received by optically pumped semiconductor antennas. In THz-TDS the travelling time (ToF) and shape of the pulse is changed if it interacts with the dielectric material and its inherent discontinuities. A tomogram of the object under the test can be reconstructed from time of flight diffraction (ToFD) scans if a synthetic focusing aperture (SAFT) algorithm is applied. The knowledge of the base materials shape and optical properties is essential for a proper reconstruction result. To obtain these properties a model is assumed which describes the device under the test as multilayer structure composed of thin layers with different dielectric characteristics. The Optical Layer Analysis (OLA) is able to fulfill these requirements. A short description why the optical properties are crucial for meaningful SAFT reconstruction results will be given first. Afterwards the OLA will be derived and applied on representative samples to discuss and evaluate its benefits and limits.

  12. Influence of the dielectric property on microwave oven heating patterns: application to food materials.

    PubMed

    Peyre, F; Datta, A; Seyler, C

    1997-01-01

    Patterns of power absorption in a microwave oven for a range of dielectric properties of relevance to food processing were investigated. The governing Maxwell's equations with boundary conditions and a TE10 excitation were solved using a finite element method. Food properties were varied from values at their frozen state to values at high temperatures, as would be typical in a thawing process. For low-loss materials such as frozen foods, the high quality factor makes the heating significantly higher only when the size and shape of the load permit a dielectric cavity resonance in the load. Otherwise, the heating pattern will follow the modal electric field pattern of the oven. For moderate loss materials, the patterns will come from the modes of the dielectric cavity. The bandwidths of these modes are larger than the low-loss situation and their overlap results in a heating pattern that is somewhat more uniform. For high-loss materials, the concept of modes is no longer useful as the very large number of modes strongly overlap. The rapidly decaying field and power loss in the high-loss material can probably be characterized as an exponential decay.

  13. Femtosecond laser micromachining of dielectric materials for biomedical applications

    NASA Astrophysics Data System (ADS)

    Farson, Dave F.; Choi, Hae Woon; Zimmerman, Burr; Steach, Jeremy K.; Chalmers, Jeffery J.; Olesik, Susan V.; Lee, L. James

    2008-03-01

    Techniques for microfluidic channel fabrication in soda-lime glass and fused quartz using femtosecond laser ablation and ablation in conjunction with polymer coating for surface roughness improvement were tested. Systematic experiments were done to characterize how process variables (laser fluence, scanning speed and focus spot overlap, and material properties) affect the machining feature size and quality. Laser fluence and focus spot overlap showed the strongest influence on channel depth and roughness. At high fluence, the surface roughness was measured to be between 395 nm and 731 nm RMS. At low fluence, roughness decreased to 100 nm-350 nm RMS and showed a greater dependence on overlap. The surface roughness of laser ablation was also dependent on the material properties. For the same laser ablation parameters, soda-lime glass surfaces were smoother than fused quartz. For some applications, especially those using quartz, smoother channels are desired. A hydroxyethyl methacrylate (HEMA) polymer coating was applied and the roughness of the coated channels was improved to 10-50 nm RMS.

  14. Force Field Benchmark of Organic Liquids: Density, Enthalpy of Vaporization, Heat Capacities, Surface Tension, Isothermal Compressibility, Volumetric Expansion Coefficient, and Dielectric Constant.

    PubMed

    Caleman, Carl; van Maaren, Paul J; Hong, Minyan; Hub, Jochen S; Costa, Luciano T; van der Spoel, David

    2012-01-10

    The chemical composition of small organic molecules is often very similar to amino acid side chains or the bases in nucleic acids, and hence there is no a priori reason why a molecular mechanics force field could not describe both organic liquids and biomolecules with a single parameter set. Here, we devise a benchmark for force fields in order to test the ability of existing force fields to reproduce some key properties of organic liquids, namely, the density, enthalpy of vaporization, the surface tension, the heat capacity at constant volume and pressure, the isothermal compressibility, the volumetric expansion coefficient, and the static dielectric constant. Well over 1200 experimental measurements were used for comparison to the simulations of 146 organic liquids. Novel polynomial interpolations of the dielectric constant (32 molecules), heat capacity at constant pressure (three molecules), and the isothermal compressibility (53 molecules) as a function of the temperature have been made, based on experimental data, in order to be able to compare simulation results to them. To compute the heat capacities, we applied the two phase thermodynamics method (Lin et al. J. Chem. Phys.2003, 119, 11792), which allows one to compute thermodynamic properties on the basis of the density of states as derived from the velocity autocorrelation function. The method is implemented in a new utility within the GROMACS molecular simulation package, named g_dos, and a detailed exposé of the underlying equations is presented. The purpose of this work is to establish the state of the art of two popular force fields, OPLS/AA (all-atom optimized potential for liquid simulation) and GAFF (generalized Amber force field), to find common bottlenecks, i.e., particularly difficult molecules, and to serve as a reference point for future force field development. To make for a fair playing field, all molecules were evaluated with the same parameter settings, such as thermostats and barostats

  15. Microwave Nondestructive Evaluation of Dielectric Materials with a Metamaterial Lens

    NASA Technical Reports Server (NTRS)

    Shreiber, Daniel; Gupta, Mool; Cravey, Robin L.

    2008-01-01

    A novel microwave Nondestructive Evaluation (NDE) sensor was developed in an attempt to increase the sensitivity of the microwave NDE method for detection of defects small relative to a wavelength. The sensor was designed on the basis of a negative index material (NIM) lens. Characterization of the lens was performed to determine its resonant frequency, index of refraction, focus spot size, and optimal focusing length (for proper sample location). A sub-wavelength spot size (3 dB) of 0.48 lambda was obtained. The proof of concept for the sensor was achieved when a fiberglass sample with a 3 mm diameter through hole (perpendicular to the propagation direction of the wave) was tested. The hole was successfully detected with an 8.2 cm wavelength electromagnetic wave. This method is able to detect a defect that is 0.037 lambda. This method has certain advantages over other far field and near field microwave NDE methods currently in use.

  16. Improved Dielectric Films For Capacitors

    NASA Technical Reports Server (NTRS)

    Yen, Shiao-Ping S.; Lewis, Carol R.; Cygan, Peter J.; Jow, T. Richard

    1994-01-01

    Dielectric films made from blends of some commercially available high-dielectric-constant cyanoresins with each other and with cellulose triacetate (CTA) have both high dielectric constants and high breakdown strengths. Dielectric constants as high as 16.2. Films used to produce high-energy-density capacitors.

  17. Optical and electrical properties of titanium dioxide films with a high magnitude dielectric constant grown on p-Si by metalorganic chemical vapor deposition at low temperature

    NASA Astrophysics Data System (ADS)

    Kim, T. W.; Jung, M.; Kim, H. J.; Park, T. H.; Yoon, Y. S.; Kang, W. N.; Yom, S. S.; Na, H. K.

    1994-03-01

    Metalorganic chemical vapor deposition of titanium dioxide (TiO2) on p-Si(100) using titanium isopropoxide and nitrous oxide via pyrolysis at relatively low (˜500 °C) temperature was performed to produce high quality TiO2/p-Si interfaces and to fabricate TiO2 insulator gates with a dielectric constant of high magnitude. Scanning electron microscopy shows that the surfaces of the TiO2 films have very smooth morphologies. From the x-ray diffraction analysis, the grown layer was found to be a polycrystalline film. Raman spectroscopy showed the optical phonon modes of a TiO2 thin film. The stoichiometry of the TiO2 film was investigated by Auger electron spectroscopy. Room-temperature current-voltage and capacitance-voltage measurements clearly revealed metal-insulator-semiconductor behavior for the samples of the Ag/TiO2/p-Si. The interface state density at the TiO2/p-Si interface was approximately high 1011 eV-1 cm-2 at the middle of the Si energy gap, and the dielectric constant determined from the capacitance-voltage measurements was as large as 73. These results indicate the TiO2 layers grown at relatively low temperature can be used for high density dynamic memory.

  18. (abstract) Characterization of Tree Water Status and Dielectric Constant Changes of North American Boreal Forests in Combination with Synthetic Aperture Radar Remote Sensing

    NASA Technical Reports Server (NTRS)

    McDonald, K. C.; Zimmerman, R.; Way, J. B.

    1994-01-01

    The occurrence and magnitude of temporal and spatial tree water status changes in the boreal environment were studied in a floodplain forest in Alaska and in four forest types of Central Canada. Under limited water supply conditions from the rooted soil zone in early spring (freeze/thaw transition) and during summer, trees show declining water potentials. Coincidental change in tree water potential, tree transpiration and tree dielectric constant had been observed in previous studies performed in Mediterranean ecotones. If radar is sensitive to chances in tree water status as reflected through changes in dielectric constant, then radar remote sensing could be used to monitor the water status of forests. The SAR imagery is examined to determine the response of the radar backscatter to the ground based observations of the water status of forest canopies. Comparisons are made between stands and also along the large North-South gradient between sites. Data from SAR are used to examine the radar response to canopy physiological state as related to vegetation freeze/thaw and growing season length.

  19. Dielectric measurement method for real-time monitoring of initial hardening of backfill materials used for underground construction

    NASA Astrophysics Data System (ADS)

    Karlovšek, Jurij; Schwing, Moritz; Chen, Zhen; Wagner, Norman; Williams, David J.; Scheuermann, Alexander

    2016-04-01

    The broadband dielectric measurement method based on the vector network analysis technique, in combination with an open-ended coaxial probe, was applied to the determination of the dielectric relaxation behaviour of one- and two-component backfilling grout materials in the frequency range from 40 MHz to 2 GHz. The cement hydration process and the gelling of commercial grouts was monitored in real-time to investigate the application of non-destructive testing methods in the tunnelling industry. It was found that the time-dependent dielectric relaxation behaviour can accurately reveal the different stages of the hydration process and delineate the start of gel hardening. These measurement results demonstrate the practicability of the real-time dielectric measurement method to determine the broadband dielectric parameters of conventional backfill materials used in underground construction to determine construction integrity using non-destructive testing methods.

  20. Silver Nanowire/MnO2 Nanowire Hybrid Polymer Nanocomposites: Materials with High Dielectric Permittivity and Low Dielectric Loss.

    PubMed

    Zeraati, Ali Shayesteh; Arjmand, Mohammad; Sundararaj, Uttandaraman

    2017-04-13

    This study reports the fabrication of hybrid nanocomposites based on silver nanowire/manganese dioxide nanowire/poly(methyl methacrylate) (AgNW/MnO2NW/PMMA), using a solution casting technique, with outstanding dielectric permittivity and low dielectric loss. AgNW was synthesized using the hard-template technique, and MnO2NW was synthesized employing a hydrothermal method. The prepared AgNW:MnO2NW (2.0:1.0 vol %) hybrid nanocomposite showed a high dielectric permittivity (64 at 8.2 GHz) and low dielectric loss (0.31 at 8.2 GHz), which are among the best reported values in the literature in the X-band frequency range (8.2-12.4 GHz). The superior dielectric properties of the hybrid nanocomposites were attributed to (i) dimensionality match between the nanofillers, which increased their synergy, (ii) better dispersion state of AgNW in the presence of MnO2NW, (iii) positioning of ferroelectric MnO2NW in between AgNWs, which increased the dielectric permittivity of nanodielectrics, thereby increasing dielectric permittivity of the hybrid nanocomposites, (iv) barrier role of MnO2NW, i.e., cutting off the contact spots of AgNWs and leading to lower dielectric loss, and (v) AgNW aligned structure, which increased the effective surface area of AgNWs, as nanoelectrodes. Comparison of the dielectric properties of the developed hybrid nanocomposites with the literature highlights their great potential for flexible capacitors.

  1. The origin dependence of the material constants: the permittivity and the inverse permeability

    NASA Astrophysics Data System (ADS)

    Anelli, Marco; Jonsson, Dan; Fliegl, Heike; Ruud, Kenneth

    2015-07-01

    New derivations of origin-independent expressions for the electric permittivity are presented, starting either from the response function of the current density that defines the absorption coefficient, or from the off-resonance single-photon scattering amplitude that leads to the Kramers-Heisenberg dispersion formula. The resulting expression for the permittivity is compared with earlier work on the origin dependence of the material constants. Different origin-independent expressions for the permittivity, the inverse permeability and the magnetisability are calculated and discussed. By considering electromagnetic plane waves in the absence of external sources, the macroscopic Maxwell equations are used to describe the response of matter to external fields. In combination with the constitutive relations, a wave equation expressed in terms of the material constants is derived. It is shown that the different definitions of the material constants lead to the same wave equation. The non-uniqueness of the definitions of the material constants is discussed in this context. Finally, based on the discussions, we propose a possible unique, origin-independent definition of the material constants.

  2. Application review of dielectric electroactive polymers (DEAPs) and piezoelectric materials for vibration energy harvesting

    NASA Astrophysics Data System (ADS)

    Yuan, Xuan; Changgeng, Shuai; Yan, Gao; Zhenghong, Zhao

    2016-09-01

    This paper reviews recent advances in vibration energy harvesting with particular emphasis on the solutions by using dielectric electroactive polymers (DEAPs) and piezoelectric materials. These smart materials are in essence capable of converting wasted vibration energy in the environment to usable electrical energy. Much previous researches have been devoted to studying the technology of harvesting mechanical energy using piezoelectric materials. The recent introduction of the DEAPs that exhibits large displacements under electric activation has led to their consideration as promising replacement for conventional piezoelectric materials. The properties of the two materials are described in this paper together with a comparison of their performance in relation with energy harvesting. Finally comparisons are made in the applications of vibration energy harvesting using these two materials. This paper has been written with reference to a large number of published papers listed in the reference section.

  3. Coplanar induction enabled by asymmetric permittivity of dielectric materials for mechanical energy conversion.

    PubMed

    Zhao, Xue Jiao; Zhu, Guang; Wang, Zhong Lin

    2015-03-25

    Triboelectric nanogenerator (TENG) is a newly emerged technology for harvesting mechanical energy, which has the promise for various practical applications. Here, we introduce a new principle of TENG in which induced current is generated between two coplanar electrodes because of different dielectric fillers of distinct permittivities. The manipulation of permittivity of dielectric materials for TENG is first reported, demonstrating a novel route in designing high-performance TENGs. When repeatedly contacting with an object, a TENG having lateral dimensions of 21 mm × 10 mm can produce an open-circuit voltage of 58.5 V and a short-circuit current of 44.7 μA. The instantaneous output power density can reach up to 708 μW. Besides, the new design incorporates all electrodes into a single plane, greatly simplifying the structure, promoting robustness, and providing a viable solution for device miniaturization.

  4. Laboratory studies of electrical properties of insulating materials. [thermal insulation of spacecraft dielectrics

    NASA Technical Reports Server (NTRS)

    Nanevicz, J. E.; Adamo, R. C.; Grier, N.

    1978-01-01

    The characteristics of satellites are influenced by the electrical properties of the dielectric exterior. It was found in simulated space environment tests that the electrical conductivities of dielectrics are affected as the result of interactions with various components of the environment. The degree to which the conductivity was affected varied with material. In some instances the changes found to occur could be used to advantage, particularly if they could be enhanced. For example, the increased electrical conductivity of Kapton resulting from solar illumination could be used to advantage to eliminate the charge storage leading to electrical breakdown during magnetic substorms. Similarly the relative immunity of FEP Teflon to change from response to the space environment makes it a logical choice as a solar cell cover in a high-voltage solar array.

  5. Dielectric relaxation of high-k oxides

    PubMed Central

    2013-01-01

    Frequency dispersion of high-k dielectrics was observed and classified into two parts: extrinsic cause and intrinsic cause. Frequency dependence of dielectric constant (dielectric relaxation), that is the intrinsic frequency dispersion, could not be characterized before considering the effects of extrinsic frequency dispersion. Several mathematical models were discussed to describe the dielectric relaxation of high-k dielectrics. For the physical mechanism, dielectric relaxation was found to be related to the degree of polarization, which depended on the structure of the high-k material. It was attributed to the enhancement of the correlations among polar nanodomain. The effect of grain size for the high-k materials' structure mainly originated from higher surface stress in smaller grain due to its higher concentration of grain boundary. PMID:24180696

  6. Analysis of the Dielectric constant of saline-alkali soils and the effect on radar backscattering coefficient: a case study of soda alkaline saline soils in Western Jilin Province using RADARSAT-2 data.

    PubMed

    Li, Yang-yang; Zhao, Kai; Ren, Jian-hua; Ding, Yan-ling; Wu, Li-li

    2014-01-01

    Soil salinity is a global problem, especially in developing countries, which affects the environment and productivity of agriculture areas. Salt has a significant effect on the complex dielectric constant of wet soil. However, there is no suitable model to describe the variation in the backscattering coefficient due to changes in soil salinity content. The purpose of this paper is to use backscattering models to understand behaviors of the backscattering coefficient in saline soils based on the analysis of its dielectric constant. The effects of moisture and salinity on the dielectric constant by combined Dobson mixing model and seawater dielectric constant model are analyzed, and the backscattering coefficient is then simulated using the AIEM. Simultaneously, laboratory measurements were performed on ground samples. The frequency effect of the laboratory results was not the same as the simulated results. The frequency dependence of the ionic conductivity of an electrolyte solution is influenced by the ion's components. Finally, the simulated backscattering coefficients measured from the dielectric constant with the AIEM were analyzed using the extracted backscattering coefficient from the RADARSAT-2 image. The results show that RADARSAT-2 is potentially able to measure soil salinity; however, the mixed pixel problem needs to be more thoroughly considered.

  7. Analysis of the Dielectric Constant of Saline-Alkali Soils and the Effect on Radar Backscattering Coefficient: A Case Study of Soda Alkaline Saline Soils in Western Jilin Province Using RADARSAT-2 Data

    PubMed Central

    Li, Yang-yang; Zhao, Kai; Ren, Jian-hua; Ding, Yan-ling; Wu, Li-li

    2014-01-01

    Soil salinity is a global problem, especially in developing countries, which affects the environment and productivity of agriculture areas. Salt has a significant effect on the complex dielectric constant of wet soil. However, there is no suitable model to describe the variation in the backscattering coefficient due to changes in soil salinity content. The purpose of this paper is to use backscattering models to understand behaviors of the backscattering coefficient in saline soils based on the analysis of its dielectric constant. The effects of moisture and salinity on the dielectric constant by combined Dobson mixing model and seawater dielectric constant model are analyzed, and the backscattering coefficient is then simulated using the AIEM. Simultaneously, laboratory measurements were performed on ground samples. The frequency effect of the laboratory results was not the same as the simulated results. The frequency dependence of the ionic conductivity of an electrolyte solution is influenced by the ion's components. Finally, the simulated backscattering coefficients measured from the dielectric constant with the AIEM were analyzed using the extracted backscattering coefficient from the RADARSAT-2 image. The results show that RADARSAT-2 is potentially able to measure soil salinity; however, the mixed pixel problem needs to be more thoroughly considered. PMID:25101317

  8. Measurement of the dielectric properties of dispersive materials over a wide frequency range.

    SciTech Connect

    Molina, Luis Leroy; Salazar, Robert Austin; Bacon, Larry Donald; Lehr, Jane Marie

    2003-06-01

    The propagation of electromagnetic waves through dispersive media forms the basis for a wide variety of applications. Rapid advances in materials have produced new products with tailored responses across frequency bands. Many of these new materials, such as radar absorbing material and photonic crystals, are dispersive in nature. This, in turn, has opened up the possibility for the exploitation of these dispersive dielectric properties for a variety of applications. Thus, it is desirable to know the electromagnetic properties of both man-made and natural materials across a wide frequency range. With the advent of transient pulsers with sub-nanosecond risetimes and rates of voltage rise approaching 10**16 V/s, the frequencies of interest in the transient response extend to approximately the 2 GHz range. Although a network analyzer can provide either frequency- or time-domain data (by inverse transform), common TEM cells are only rated to 0.5 to 1.5 GHz--significantly below the maximum frequency of interest. To extend the frequency range to include 2 GHz, a TEM cell was characterized and a deembedding algorithm was applied to account, in part, for the limitations of the cell. The de-embedding technique is described along with such measurement issues such as clear time and sneak around. Measurements of complex permittivity of common drinking water are shown. This frequency extension will lead to more expansive testing of dielectric materials of interest.

  9. Piezoelectric and Dielectric Properties of Fe2O3-Doped 0.57Pb(Sc1/2Nb1/2)O3 0.43PbTiO3 Ceramic Materials

    NASA Astrophysics Data System (ADS)

    Kim, Jin-Soo; Kim, So-Jung; Kim, Ho-Gi; Lee, Duck-Chool; Uchino, Kenji

    1999-03-01

    High-power piezoelectric materials are presently being extensively developed for applications such as ultrasonic motors and piezoelectric transformers. In this study, the piezoelectric and dielectric properties of Fe2O3-doped 0.57Pb(Sc1/2Nb1/2)O3 0.43PbTiO3 (hereafter 0.57PSN 0.43PT), which is the morphotropic phase boundary composition of the PSN PT system, were investigated. The maximum dielectric constant (ɛ33/ɛ0=2551) and the minimum dielectric loss (tanδ=0.51%) at room temperature were obtained at Fe2O3 additions of 0.1 wt% and 0.3 wt%, respectively. The temperature dependence of the dielectric constant and the dielectric loss was measured between room temperature and 350°C. With the addition of Fe2O3, the piezoelectric constant d33 and electromechanical coupling factor kp were slightly decreased, but the mechanical quality factor Qm was significantly increased. The highest mechanical quality factor (Qm=297) was obtained at 0.3 wt% Fe2O3, which is 4.4 times higher than that of nondoped 0.57PSN 0.43PT ceramics. The P E and S E loops of the samples at room temperature and at 1.0 Hz were measured at the same time using an automated polarization measuring system.

  10. Surface chemical bonds, surface-enhanced Raman scattering, and dielectric constant of SiO2 nanospheres in-situ decorated with Ag-nanoparticles by electron-irradiation

    NASA Astrophysics Data System (ADS)

    Phatangare, A. B.; Dhole, S. D.; Dahiwale, S. S.; Mathe, V. L.; Bhoraskar, S. V.; Late, D. J.; Bhoraskar, V. N.

    2016-12-01

    Nanostructures of dielectric materials decorated with metal nanoparticles are of great scientific interest; however, the involved synthesis methods are complicated and require multistep chemical processing, including functionalization of the dielectric surfaces. In the present work, without chemical processes, silver nanoparticles of average sizes in the range of 11 to 15 nm were in-situ synthesized and decorated on SiO2 nanospheres in a single step process by irradiating a solution (AgNO3-polyvinylpyrrolidone (PVP)-SiO2 nanospheres) with 6 MeV electrons at 1.5 × 1015 e-/cm2, 3.0 × 1015 e-/cm2, and 4.5 × 1015 e-/cm2 fluences. The electron irradiated solutions were characterized with different surface and other techniques. The results revealed that the SiO2 nanospheres were uniformly decorated with Ag nanoparticles, and the prominent chemical bonds involved were Ag-O, Si-O-Ag, and Si-Ag. Moreover, the sizes and the decoration density of Ag nanoparticles could be tailored by varying electron fluence. The Surface-enhanced Raman scattering (SERS) of 4-aminothiophenol (4-ATP) solutions was studied using substrates in the form of thin coatings of the solutions of Ag-decorated SiO2 nanospheres. The appearance of the characteristic SERS peaks of both 4-ATP and 4, 4'-dimercaptoazobenzene (4, 4'-DMAB) in Raman spectra confirmed the conversion of a fraction of 4-ATP into 4, 4'-DMAB in the presence of Ag nanoparticles. Composites in the form of thin films were synthesized from the mixture solutions of PVP and Ag-decorated SiO2 nanospheres. The dielectric constant of each thin film was higher as compared to polymers, and could be tailored by varying electron fluence used for decorating Ag nanoparticles.

  11. Influence of dielectric materials on uniformity of large-area capacitively coupled plasmas for N2/Ar discharges

    NASA Astrophysics Data System (ADS)

    Liang, Ying-Shuang; Zhang, Yu-Ru; Wang, You-Nian

    2016-10-01

    The effect of the dielectric ring on the plasma radial uniformity is numerically investigated in the practical 450-mm capacitively coupled plasma reactor by a two-dimensional self-consistent fluid model. The simulations were performed for N2/Ar discharges at the pressure of 300 Pa, and the frequency of 13.56 MHz. In the practical plasma treatment process, the wafer is always surrounded by a dielectric ring, which is less studied. In this paper, the plasma characteristics are systematically investigated by changing the properties of the dielectric ring, i.e., the relative permittivity, the thickness and the length. The results indicate that the plasma parameters strongly depend on the properties of the dielectric ring. As the ratio of the thickness to the relative permittivity of the dielectric ring increases, the electric field at the wafer edge becomes weaker due to the stronger surface charging effect. This gives rise to the lower ion density, flux and N atom density at the wafer edge. Thus the homogeneous plasma density is obtained by selecting optimal dielectric ring relative permittivity and thickness. In addition, we also find that the length of the dielectric ring should be as short as possible to avoid the discontinuity of the dielectric materials, and thus obtain the large area uniform plasma. Project supported by the National Natural Science Foundation of China (Grant Nos. 11335004 and 11405019) and the Important National Science and Technology Specific Project of China (Grant No. 2011ZX02403-001).

  12. High Dielectric Constants of Composites of Fiber-Like Copper Phthalocyanine-Coated Graphene Oxide Embedded in Poly(arylene Ether Nitriles)

    NASA Astrophysics Data System (ADS)

    Li, Jingwei; Pu, Zejun; Wang, Zicheng; Long, Ya; Jia, Kun; Liu, Xiaobo

    2015-07-01

    The surfaces of graphene oxide (GO) sheets were coated with fiber-like copper phthalocyanine (CuPc) by use of a solvothermal process. The product, GO@ CuPc, was used as a filler in high-performance poly(arylene ether nitrile) (PEN) composites. Films of the composites had high thermal stability, and glass-transition temperatures in the range 170-182°C. Thermogravimetric analysis revealed their initial decomposition temperatures were in the range 470-483°C. Scanning electron microscopy showed that dispersion of GO@ CuPc in PEN was much better than that of unmodified GO; this can be attributed to relatively strong interaction between GO@CuPc and the PEN matrix. All the composite films were highly flexible and had enhanced mechanical properties. Tensile strengths of the composites were as high as 89 MPa in the presence of 1 wt.% GO@CuPc, an increase of 20% compared with pure PEN film. Dielectric constants of the composite films were as high as 52 at 100 Hz when the GO@CuPc content was 5%. Because of these excellent mechanical and dielectric properties, PEN/GO@CuPc composites have much potential for use as film capacitors.

  13. Achieving high dielectric constant and low loss property in a dipolar glass polymer containing strongly dipolar and small-sized sulfone groups.

    PubMed

    Wei, Junji; Zhang, Zhongbo; Tseng, Jung-Kai; Treufeld, Imre; Liu, Xiaobo; Litt, Morton H; Zhu, Lei

    2015-03-11

    In this report, a dipolar glass polymer, poly(2-(methylsulfonyl)ethyl methacrylate) (PMSEMA), was synthesized by free radical polymerization of the corresponding methacrylate monomer. Due to the large dipole moment (4.25 D) and small size of the side-chain sulfone groups, PMSEMA exhibited a strong γ transition at a temperature as low as -110 °C at 1 Hz, about 220 °C below its glass transition temperature around 109 °C. Because of this strong γ dipole relaxation, the glassy PMSEMA sample exhibited a high dielectric constant of 11.4 and a low dissipation factor (tan δ) of 0.02 at 25 °C and 1 Hz. From an electric displacement-electric field (D-E) loop study, PMSEMA demonstrated a high discharge energy density of 4.54 J/cm(3) at 283 MV/m, nearly 3 times that of an analogue polymer, poly(methyl methacrylate) (PMMA). However, the hysteresis loss was only 1/3-1/2 of that for PMMA. This study suggests that dipolar glass polymers with large dipole moments and small-sized dipolar side groups are promising candidates for high energy density and low loss dielectric applications.

  14. Micropolarities of lipid bilayers and micelles. 3. Effect of monovalent ions on the dielectric constant of the water-membrane interface of unilamellar phosphatidylcholine vesicles

    SciTech Connect

    Lessard, J.G.; Fragata, M.

    1986-02-27

    A study was undertaken of the effect of monovalent cations (Li/sup +/, Na/sup +/, K/sup +/) on the dielectric constant (epsilon) of the water-lipid interface of unilamellar phosphatidylcholine (PC) vesicles, i.e., the ester carbonyl oxygen region of the PC molecules or the neighborhood of the oxygen atoms of the phosphorylcholine moiety. epsilon was determined by reacting the free radical 1,1-diphenyl-2-picrylhydrazyl with ..cap alpha..-tocopherol incorporated in the lipid vesicles. The results are consistent with a decrease of epsilon (LiCl: 35.5 to 29.5; NaCl: 34 to 29; KCl: 33 to 29) as the concentration of the salts in the solvent media increases from 0.025 to 0.5 M. These effects can be rationalized in terms of dielectric saturation at the water-lipid interface brought about by ion-induced local electric fields. In the unilamellar PC vesicles the effect of the ions on epsilon follows the sequence K/sup +/ > Na/sup +/ > Li/sup +/ which contrasts strikingly with what happens in the liquid state where this is Li/sup +/ > Na/sup +/ > K/sup +/. These effects are related to the degree of hydration of the dissociated ions at the water-lipid interface which must differ in a considerable way from that in the liquid state. 43 references, 5 figures, 2 tables.

  15. Toward Automated Benchmarking of Atomistic Force Fields: Neat Liquid Densities and Static Dielectric Constants from the ThermoML Data Archive.

    PubMed

    Beauchamp, Kyle A; Behr, Julie M; Rustenburg, Ariën S; Bayly, Christopher I; Kroenlein, Kenneth; Chodera, John D

    2015-10-08

    Atomistic molecular simulations are a powerful way to make quantitative predictions, but the accuracy of these predictions depends entirely on the quality of the force field employed. Although experimental measurements of fundamental physical properties offer a straightforward approach for evaluating force field quality, the bulk of this information has been tied up in formats that are not machine-readable. Compiling benchmark data sets of physical properties from non-machine-readable sources requires substantial human effort and is prone to the accumulation of human errors, hindering the development of reproducible benchmarks of force-field accuracy. Here, we examine the feasibility of benchmarking atomistic force fields against the NIST ThermoML data archive of physicochemical measurements, which aggregates thousands of experimental measurements in a portable, machine-readable, self-annotating IUPAC-standard format. As a proof of concept, we present a detailed benchmark of the generalized Amber small-molecule force field (GAFF) using the AM1-BCC charge model against experimental measurements (specifically, bulk liquid densities and static dielectric constants at ambient pressure) automatically extracted from the archive and discuss the extent of data available for use in larger scale (or continuously performed) benchmarks. The results of even this limited initial benchmark highlight a general problem with fixed-charge force fields in the representation low-dielectric environments, such as those seen in binding cavities or biological membranes.

  16. Dielectric study on hierarchical water structures restricted in cement and wood materials

    NASA Astrophysics Data System (ADS)

    Abe, Fumiya; Nishi, Akihiro; Saito, Hironobu; Asano, Megumi; Watanabe, Seiei; Kita, Rio; Shinyashiki, Naoki; Yagihara, Shin; Fukuzaki, Minoru; Sudo, Seiichi; Suzuki, Youki

    2017-04-01

    Dielectric relaxation processes for mortar observed by broadband dielectric spectroscopy were analyzed in the drying and hydration processes for an aging sample in the frequency region from 1 MHz up to 2 MHz. At least two processes for structured water in the kHz frequency region and another mHz relaxation process affected by ionic behaviors were observed. Comparison of the relaxation parameters obtained for the drying and hydration processes suggests an existence of hierarchical water structures in the exchange of water molecules, which are originally exchanged from free water observed at around 20 GHz. The water molecules reflected in the lower frequency process of the two kHz relaxation processes are more restricted and take more homogeneous structures than the higher kHz relaxation process. These structured water usually hidden in large ionic behaviors for wood samples was observed by electrodes covered by a thin Teflon film, and hierarchical water structures were also suggested for wood samples. Dielectric spectroscopy technique is an effective tool to analyze the new concept of hierarchical water structures in complex materials.

  17. Overview of high voltage dielectric material for traveling wave kicker magnet application

    NASA Astrophysics Data System (ADS)

    Zhang,; Sandberg,; Tuozzolo,; Cassel,

    2002-06-01

    Pulsed high power fast kickers are being used to change beam trajectories in particle accelerators. The fast rise and fall time of pulse waveform demands a transmission line structure for the kicker deflector design. The ideal design will be parallel metal plates. However, it uses very long straight sections to achieve the required deflection. In accelerators with constrained straight sections, high permeability materials such as ferrite have to be used to gain deflection efficiency. The transmission line kicker magnet is also referred as traveling wave kicker magnet. Its construction is based on distributed 1-C cells along the longitudinal direction. The magnetic cells and capacitive cells are interleaved to simulate the characteristic impedance of a transmission line to minimize pulse reflection, and provide adequate frequency bandwidth to transmit the kicker pulse with fast rise and fall time. The magnetic cells are usually made of ferrite ceramics, but the capacitive cells have been made with different materials. For traveling wave kickers with higher impedance, the parallel plate vacuum capacitor has been used in CERN and KEK design. Others have used ceramic capacitors, printed circuit boards, and high permittivity ceramics as the capacitive cell. The high dielectric material has the advantage of compactness for low impedance kicker magnet construction. It continues to be very attractive for future kicker magnet applications. The high voltage phenomena associated with high dielectric ceramic materials have been widely reported in many industrial application areas.

  18. Chemical modeling of boron adsorption by humic materials using the constant capacitance model

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The constant capacitance surface complexation model was used to describe B adsorption behavior on reference Aldrich humic acid, humic acids from various soil environments, and dissolved organic matter extracted from sewage effluents. The reactive surface functional groups on the humic materials wer...

  19. Validity evaluation of Sc x Al1-x N material constants based on SAW characteristics

    NASA Astrophysics Data System (ADS)

    Tang, Gongbin; Han, Tao; Zhang, Qiaozhen; Yamazaki, Kenta; Omori, Tatsuya; Hashimoto, Ken-ya

    2016-11-01

    This paper is aimed at examining the validity of material constants reported for use in surface acoustic wave (SAW) device simulations. First, based on the full set of material constants calculated by first principle, bulk acoustic wave velocities are calculated for Sc x Al1-x N and compared with published experimental results. Then, the effects of the Sc x Al1-x N material constants with different Sc content on acoustic characteristics are calculated and the influence of shear vibrations on SAW characteristics are recognized. Then, a series of SAW devices are fabricated on Sc x Al1-x N film/Si substrate structure with various Cu and ScAlN thicknesses h Cu and h ScAlN, respectively, and measured variations of phase velocity V and effective electromechanical coupling factor K\\text{e}2 with these parameters are compared with the calculation. The fairly well-agreed results indicate a reliable set of Sc x Al1-x N material constants for SAW device simulations.

  20. Estimating Energy Conversion Efficiency of Thermoelectric Materials: Constant Property Versus Average Property Models

    NASA Astrophysics Data System (ADS)

    Armstrong, Hannah; Boese, Matthew; Carmichael, Cody; Dimich, Hannah; Seay, Dylan; Sheppard, Nathan; Beekman, Matt

    2017-01-01

    Maximum thermoelectric energy conversion efficiencies are calculated using the conventional "constant property" model and the recently proposed "cumulative/average property" model (Kim et al. in Proc Natl Acad Sci USA 112:8205, 2015) for 18 high-performance thermoelectric materials. We find that the constant property model generally predicts higher energy conversion efficiency for nearly all materials and temperature differences studied. Although significant deviations are observed in some cases, on average the constant property model predicts an efficiency that is a factor of 1.16 larger than that predicted by the average property model, with even lower deviations for temperature differences typical of energy harvesting applications. Based on our analysis, we conclude that the conventional dimensionless figure of merit ZT obtained from the constant property model, while not applicable for some materials with strongly temperature-dependent thermoelectric properties, remains a simple yet useful metric for initial evaluation and/or comparison of thermoelectric materials, provided the ZT at the average temperature of projected operation, not the peak ZT, is used.

  1. The Interaction of Radio-Frequency Fields With Dielectric Materials at Macroscopic to Mesoscopic Scales

    PubMed Central

    Baker-Jarvis, James; Kim, Sung

    2012-01-01

    The goal of this paper is to overview radio-frequency (RF) electromagnetic interactions with solid and liquid materials from the macroscale to the nanoscale. The overview is geared toward the general researcher. Because this area of research is vast, this paper concentrates on currently active research areas in the megahertz (MHz) through gigahertz (GHz) frequencies, and concentrates on dielectric response. The paper studies interaction mechanisms both from phenomenological and fundamental viewpoints. Relaxation, resonance, interface phenomena, plasmons, the concepts of permittivity and permeability, and relaxation times are summarized. Topics of current research interest, such as negative-index behavior, noise, plasmonic behavior, RF heating, nanoscale materials, wave cloaking, polaritonic surface waves, biomaterials, and other topics are overviewed. Relaxation, resonance, and related relaxation times are overviewed. The wavelength and material length scales required to define permittivity in materials is discussed. PMID:26900513

  2. The Interaction of Radio-Frequency Fields With Dielectric Materials at Macroscopic to Mesoscopic Scales.

    PubMed

    Baker-Jarvis, James; Kim, Sung

    2012-01-01

    The goal of this paper is to overview radio-frequency (RF) electromagnetic interactions with solid and liquid materials from the macroscale to the nanoscale. The overview is geared toward the general researcher. Because this area of research is vast, this paper concentrates on currently active research areas in the megahertz (MHz) through gigahertz (GHz) frequencies, and concentrates on dielectric response. The paper studies interaction mechanisms both from phenomenological and fundamental viewpoints. Relaxation, resonance, interface phenomena, plasmons, the concepts of permittivity and permeability, and relaxation times are summarized. Topics of current research interest, such as negative-index behavior, noise, plasmonic behavior, RF heating, nanoscale materials, wave cloaking, polaritonic surface waves, biomaterials, and other topics are overviewed. Relaxation, resonance, and related relaxation times are overviewed. The wavelength and material length scales required to define permittivity in materials is discussed.

  3. Role of copper in time dependent dielectric breakdown of porous organo-silicate glass low-k materials

    NASA Astrophysics Data System (ADS)

    Zhao, Larry; Pantouvaki, Marianna; Croes, Kristof; Tőkei, Zsolt; Barbarin, Yohan; Wilson, Christopher J.; Baklanov, Mikhail R.; Beyer, Gerald P.; Claeys, Cor

    2011-11-01

    The role of copper in time dependent dielectric breakdown (TDDB) of a porous low-k dielectric with TaN/Ta barrier was investigated on a metal-insulator-metal capacitor configuration where Cu ions can drift into the low-k film by applying a positive potential on the top while they are not permitted to enter the low-k dielectric if a negative potential is applied on the top. No difference in TDDB performance was observed between the positive and negative bias conditions, suggesting that Cu cannot penetrate TaN/Ta barrier to play a critical role in the TDDB of porous low-k material.

  4. Investigation of dielectric properties of different cake formulations during microwave and infrared-microwave combination baking.

    PubMed

    Sakiyan, Ozge; Sumnu, Gulum; Sahin, Serpil; Meda, Venkatesh

    2007-05-01

    Dielectric properties can be used to understand the behavior of food materials during microwave processing. Dielectric properties influence the level of interaction between food and high frequency electromagnetic energy. Dielectric properties are, therefore, important in the design of foods intended for microwave preparation. In this study, it was aimed to determine the variation of dielectric properties of different cake formulations during baking in microwave and infrared-microwave combination oven. In addition, the effects of formulation and temperature on dielectric properties of cake batter were examined. Dielectric constant and loss factor of cake samples were shown to be dependent on formulation, baking time, and temperature. The increase in baking time and temperature decreased dielectric constant and loss factor of all formulations. Fat content was shown to increase dielectric constant and loss factor of cakes.

  5. Effect of Solvent Dielectric Constant and Acidity on the OH Vibration Frequency in Hydrogen-Bonded Complexes of Fluorinated Ethanols.

    PubMed

    Pines, Dina; Keinan, Sharon; Kiefer, Philip M; Hynes, James T; Pines, Ehud

    2015-07-23

    Infrared spectroscopy measurements were used to characterize the OH stretching vibrations in a series of similarly structured fluoroethanols, RCH2OH (R = CH3, CH2F, CHF2, CF3), a series which exhibits a systematic increase in the molecule acidity with increasing number of F atoms. This study, which expands our earlier efforts, was carried out in non-hydrogen-bonding solvents comprising molecules with and without a permanent dipole moment, with the former solvents being classified as polar solvents and the latter designated as nonpolar. The hydrogen bond interaction in donor-acceptor complexes formed in solution between the fluorinated ethanol H-donors and the H-acceptor base DMSO was investigated in relation to the solvent dielectric and to the differences ΔPA of the gas phase proton affinities (PAs) of the conjugate base of the fluorinated alcohols and DMSO. We have observed that νOH decreases as the acidity of the alcohol increases (ΔPA decreases) and that νOH varies inversely with ε, exhibiting different slopes for nonpolar and polar solvents. These 1/ε slopes tend to vary linearly with ΔPA, increasing with increasing acidity. These experimental findings, including the ΔPA trends, are described with our recently published two-state Valence Bond-based theory for acid-base H-bonded complexes. Lastly, the correlation of the alcohol's conjugate base PAs with Taft σ* values of the fluorinated ethyl groups CH(n)F(3-n)CH2- provides a connection of the inductive effects for these groups with the acidity parameter ΔPA associated with the H-bonded complexes.

  6. Exhibition of circular Bragg phenomenon by hyperbolic, dielectric, structurally chiral materials

    NASA Astrophysics Data System (ADS)

    Lakhtakia, Akhlesh

    2014-01-01

    The relative permittivity dyadic of a dielectric structurally chiral material (SCM) varies helicoidally along a fixed direction; in consequence, the SCM exhibits the circular Bragg phenomenon, which is the circular-polarization-selective reflection of light. The introduction of hyperbolicity in an SCM-by making either one or two but not all three eigenvalues of the relative permittivity dyadic acquire negative real parts-does not eliminate the circular Bragg phenomenon, but significantly alters the regime for its exhibition. Significantly wider circular-polarization-sensitive stopbands may be exhibited by hyperbolic SCMs in comparison to nonhyperbolic SCMs. Physical vapor deposition techniques appear to be suitable to fabricate hyperbolic SCMs.

  7. Influence of dielectric materials on radial uniformity in non-equilibrium atmospheric pressure helium plasma

    NASA Astrophysics Data System (ADS)

    Oda, Akinori; Komori, Kyohei

    2015-09-01

    Non-equilibrium atmospheric pressure plasma has been utilized for various technological applications such as surface treatment, materials processing, bio-medical and bio-logical applications. For optimum control of the plasma for the above applications, numerous experimental and theoretical investigations on the plasma have been reported. Especially, controlling radial uniformity of the plasma are very important for utilizing materials processing. In this paper, an axially-symmetric three-dimensional fluid model, which is composed of the continuity equation for charged and neutral species, the Poisson equation, and the energy conservation equation for electrons, of non-equilibrium atmospheric pressure helium plasma has been developed. Then, influence of dielectric properties (e.g. relative permittivity, secondary electron emission coefficient, etc.) of dielectric materials on radial plasma uniformity (i.e. radial distributions of electron density, ion density, electric field in the plasma) was examined. This work was partly supported by KAKENHI (No. 26420247), and a ``Grant for Advanced Industrial Technology Development (No. 11B06004d)'' in 2011 from the New Energy and Industrial Technology Development Organization (NEDO) of Japan.

  8. Classification of dispersion equations for homogeneous, dielectric-magnetic, uniaxial materials.

    PubMed

    Depine, Ricardo A; Inchaussandague, Marina E; Lakhtakia, Akhlesh

    2006-04-01

    The geometric representation at a fixed frequency of the wave vector (or dispersion) surface omega(k) for lossless, homogeneous, dielectric-magnetic uniaxial materials is explored for the case when the elements of the relative permittivity and permeability tensors of the material can have any sign. Electromagnetic plane waves propagating inside the material can exhibit dispersion surfaces in the form of ellipsoids of revolution, hyperboloids of one sheet, or hyperboloids of two sheets. Furthermore, depending on the relative orientation of the optic axis, the intersections of these surfaces with fixed planes of propagation can be circles, ellipses, hyperbolas, or straight lines. The understanding obtained is used to study the reflection and refraction of electromagnetic plane waves due to a planar interface with an isotropic medium.

  9. Metal Decorated Multi-Walled Carbon Nanotube/Polyimide Composites with High Dielectric Constants and Low Loss Factors

    NASA Technical Reports Server (NTRS)

    Ghose, Sayata; Watson, Kent A.; Dudley, Kenneth L.; Elliott, Holly A.; Smith, Joseph G.; Connell, John W.

    2009-01-01

    The measurement of observable electromagnetic phenomena in materials and their derived intrinsic electric material properties are of prime importance in the discovery and development of material systems for electronic and aerospace applications. Nanocomposite materials comprised of metal decorated multi-walled carbon nanotubes (MWCNTs) were prepared by a facile method and characterized. Metal particles such as silver, platinum and palladium with diameters ranging from less than 5 to over 50 nanometers were distributed randomly on the MWCNTs. The metal-containing MWCNTs were then melt mixed into a polymer matrix and the mixture extruded as ribbons. These extruded ribbons exhibited a moderate to high degree of MWCNT alignment as determined by HRSEM. These ribbons were then fabricated into test specimens while maintaining MWCNT alignment and subsequently characterized for electromagnetic properties at 8-12 GHz. The present study is focused on silver decorated MWCNTs dispersed in an Ultem polyimide matrix. The results of the electromagnetic characterization showed that certain sample configurations exhibited a decoupling of the permittivity and loss factor (?? and ??) indicating that these properties could be tailored within certain limits. The decoupling and independent control of these fundamental electrical material parameters offer a new class of materials with potential applications in electronics, microwave engineering and optics.

  10. Metal Decorated Multi-Walled Carbon Nanotube/Polyimide Composites with High Dielectric Constants and Low Loss Factors

    NASA Technical Reports Server (NTRS)

    Elliott, Holly A.; Dudley, Kenneth L.; Smith, Joseph G.; Connell, John W.; Ghose, Sayata; Watson, Kent A.; Sun, Keun J.

    2009-01-01

    The measurement of observable electromagnetic phenomena in materials and their derived intrinsic electrical material properties are of prime importance in the discovery and development of material systems for electronic and aerospace applications. Nanocomposite materials comprised of metal decorated multi-walled carbon nanotubes (MWCNTs) were prepared by a facile method and characterized. Metal particles such as silver(Ag), platinum(Pt) and palladium(Pd) with diameters ranging from less than 5 to over 50 nanometers were distributed randomly on the MWCNTs. The present study is focused on silver decorated MWCNTs dispersed in a polyimide matrix. The Ag-containing MWCNTs were melt mixed into Ultem(TradeMark) and the mixture extruded as ribbons. The extruded ribbons exhibited a moderate to high degree of MWCNT alignment as determined by HRSEM. These ribbons were then fabricated into test specimens while maintaining MWCNT alignment and subsequently characterized for electrical and electromagnetic properties at 8-12 GHz. The results of the electromagnetic characterization showed that certain sample configurations exhibited a decoupling of the permittivity (epsilon ) and loss factor (epsilon") indicating that these properties could be tailored within certain limits. The decoupling and independent control of these fundamental electrical material parameters offers a new class of materials with potential applications in electronics, microwave engineering and optics.

  11. A test method for determining adhesion forces and Hamaker constants of cementitious materials using atomic force microscopy

    SciTech Connect

    Lomboy, Gilson; Sundararajan, Sriram; Wang Kejin; Subramaniam, Shankar

    2011-11-15

    A method for determining Hamaker constant of cementitious materials is presented. The method involved sample preparation, measurement of adhesion force between the tested material and a silicon nitride probe using atomic force microscopy in dry air and in water, and calculating the Hamaker constant using appropriate contact mechanics models. The work of adhesion and Hamaker constant were computed from the pull-off forces using the Johnson-Kendall-Roberts and Derjagin-Muller-Toropov models. Reference materials with known Hamaker constants (mica, silica, calcite) and commercially available cementitious materials (Portland cement (PC), ground granulated blast furnace slag (GGBFS)) were studied. The Hamaker constants of the reference materials obtained are consistent with those published by previous researchers. The results indicate that PC has a higher Hamaker constant than GGBFS. The Hamaker constant of PC in water is close to the previously predicted value C{sub 3}S, which is attributed to short hydration time ({<=} 45 min) used in this study.

  12. A New Dielectric Resonator Antenna Operating with Magneto-Dielectric Materials Based in Y3FE5-2xBIxBx Garnets

    DTIC Science & Technology

    2010-02-28

    80 (2009) 055706-055710 (IOP) 11 - Study of a microwave ferrite resonator antenna , based in a ferrimagnetic composite (Gd3Fe5012)GdIGX-( Y3Fe5012...fernte composite, a bulk cylindrical geometry was also investigated 15. SUBJECT TERMS DIELECTRIC RESONATOR ANTENNA . RADAR. FERRITES 16. SECURITY...cylindrical ceramic bulk ferrite resonator antennas . In the RF range, we observed that the material is rather stable because of its small changes as a

  13. Fine grains ceramics of PIN-PT, PIN-PMN-PT and PMN-PT systems: drift of the dielectric constant under high electric field.

    PubMed

    Pham-Thi, M; Augier, C; Dammak, H; Gaucher, P

    2006-12-22

    Lead-based ferroelectric ceramics with (1-x)Pb(B1 B2)O3-xPbTiO3 formula have emerged as a group of promising materials for various applications like ultrasonic sonars or medical imaging transducers. (1-x)PMN-xPT, (1-x)PIN-xPT and ternary solutions xPIN-yPMN-zPT ceramics are synthesised using the solid state reaction method. Our objective is to achieve higher structural transition temperatures than those of PMN-PT ceramics with as good dielectric, piezoelectric and electromechanical properties. Ceramics capacitance and loss tangent are measured when the ac field of measurement increases up to E=500 V/mm. Behaviours of these materials under ac field are related to their coercive field and Curie temperature.

  14. Dielectric and Elastic Properties of Mixed Ferroelectric Material Potassium TANTALUM(1-X) Niobium(x) Oxide

    NASA Astrophysics Data System (ADS)

    Wang, Xiaomei

    Ferroelectricity is one of the important fields in solid state physics because of its scientific and technological significance. This dissertation describes dielectric and elastic properties of the ferroelectric system KTa_{1-x}Nb_{x}O _3 (KTN) with niobium in the concentration range 1.2% ~ 16%. The occurrence and the nature of the phase transition in mixed ferroelectric systems is an intriguing topic due to the introduction of configurational disorder. Experimental results have shown that the critical temperature T _{c} in the KTN system strongly depends on the concentration of Nb and that the transverse optic soft mode frequency decreases as the concentration of Nb increases. However, the origin of the phase transition in this system is not clearly known. In particular, it is not yet clear whether or not the transition is driven by a soft mode and how the nature of the transition evolves as the Nb concentration is changed. This dissertation describes experimental work on the dielectric and elastic behaviors of the KTN system. The results on the linear and the nonlinear dielectric constants and on the electric polarization of KTN reveal (a) the occurrence of a structural transition with the appearance of ferroelectric macroregions at T_{c }, even for relatively low impurity concentrations (b) the presence of polar microregions significantly above T_{c}. The phase transition in KTN is driven by the interaction between effective dipolar moments d* rather than a soft mode. Our experimental results also reveal the coexistence of both dipolar glass like and ferroelectric behaviors in KTN with low Nb concentrations. Elastic results obtained on KTN provide direct evidence of the two distinct stages which the transition go through when approaching the critical temperature T _{c}. The ultrasonic measurements of the longitudinal elastic constant C_ {11} shows the softening of C _{11} with a (T-T_ {c})^{-mu} dependence at intermediate temperature in the first stage. In the

  15. Nano-composite polymer gel electrolytes containing ortho-nitro benzoic acid: role of dielectric constant of solvent and fumed silica

    NASA Astrophysics Data System (ADS)

    Kumar, R.

    2015-03-01

    In this paper, nano-composite polymer gel electrolytes containing polymethylmethacrylate, dimethylacetamide, diethyl carbonate, fumed silica and ortho-nitro benzoic acid have been synthesized. Electrical conductivity, viscosity, pH and thermal behavior of these electrolytes have been studied. The effect of acid, polymer, fumed silica concentration on conductivity, pH and viscosity has been discussed. The effect of dielectric constant of solvent on conductivity behavior of composite polymer gel electrolytes has also been studied. Two maxima in conductivity behavior have been observed with fumed silica concentration for composite polymer gel electrolytes, which have been explained on the basis of double percolation threshold model. Maximum conductivity of 3.20 × 10-4 and 2.46 × 10-6 S/cm at room temperature has been observed for nano-composite polymer gel electrolytes containing 10 wt% polymethylmethacrylate in 1 M solution of o-nitro benzoic acid in dimethylacetamide and diethyl carbonate respectively. The intensity of first maximum observed in conductivity at low concentration of fumed silica has been found to decrease with the decrease in acid concentration for composite polymer gel electrolytes, while the intensity of second maximum at higher fumed silica concentration remains unaffected. The conductivity of composite gels does not show much change in the temperature range of 20-100 °C and also remains constant with time, making them suitable for use as electrolytes in various devices like fuel cells, proton batteries, electrochromic window applications etc.

  16. Optical properties of dielectric films dispersed with metal nanoparticles and applications to optically functional materials

    NASA Astrophysics Data System (ADS)

    Wakaki, Moriaki; Yokoyama, Eisuke

    2010-12-01

    Nanoparticles of noble metals exhibit variety of colors in the visible light region due to a surface plasmon resonance. The size-induced properties of nanoparticles enable addition of flexibility to existing systems in many areas. To design a material with desired electrical and optical properties is the aim in many composite materials. In this paper, we report the preparation and characterization of silver nanoparticles in SiO2, TiO2 and ZrO2 films and gold nanoparticles in TiO2 and ZrO2 films. To analyze the dielectric characteristic of the metal-dielectric nanocomposite film, three kinds of matrices with a different refractive index were compared. Titanium dioxide (TiO2) is one of the most promising photocatalysts and actively used in various practical applications. However, only a narrow band in the ultraviolet region of solar light, about 3-4%, is available for photocatalytic reaction. Therefore, the development of TiO2 photocatalysts with higher photoelectric conversion efficiency for visible light is required. Plasmon-induced photocatalytic activity in the ultraviolet and visible light region was studied for the TiO2 thin film dispersed with gold nanoparticles. Photocatalytic activity of Au/TiO2 film was analyzed by degradation of stearic acid, and compared with non-doped TiO2film.

  17. Optical properties of dielectric films dispersed with metal nanoparticles and applications to optically functional materials

    NASA Astrophysics Data System (ADS)

    Wakaki, Moriaki; Yokoyama, Eisuke

    2011-08-01

    Nanoparticles of noble metals exhibit variety of colors in the visible light region due to a surface plasmon resonance. The size-induced properties of nanoparticles enable addition of flexibility to existing systems in many areas. To design a material with desired electrical and optical properties is the aim in many composite materials. In this paper, we report the preparation and characterization of silver nanoparticles in SiO2, TiO2 and ZrO2 films and gold nanoparticles in TiO2 and ZrO2 films. To analyze the dielectric characteristic of the metal-dielectric nanocomposite film, three kinds of matrices with a different refractive index were compared. Titanium dioxide (TiO2) is one of the most promising photocatalysts and actively used in various practical applications. However, only a narrow band in the ultraviolet region of solar light, about 3-4%, is available for photocatalytic reaction. Therefore, the development of TiO2 photocatalysts with higher photoelectric conversion efficiency for visible light is required. Plasmon-induced photocatalytic activity in the ultraviolet and visible light region was studied for the TiO2 thin film dispersed with gold nanoparticles. Photocatalytic activity of Au/TiO2 film was analyzed by degradation of stearic acid, and compared with non-doped TiO2film.

  18. Influence of non-collisional laser heating on the electron dynamics in dielectric materials

    NASA Astrophysics Data System (ADS)

    Barilleau, L.; Duchateau, G.; Chimier, B.; Geoffroy, G.; Tikhonchuk, V.

    2016-12-01

    The electron dynamics in dielectric materials induced by intense femtosecond laser pulses is theoretically addressed. The laser driven temporal evolution of the energy distribution of electrons in the conduction band is described by a kinetic Boltzmann equation. In addition to the collisional processes for energy transfer such as electron-phonon-photon and electron-electron interactions, a non-collisional process for photon absorption in the conduction band is included. It relies on direct transitions between sub-bands of the conduction band through multiphoton absorption. This mechanism is shown to significantly contribute to the laser heating of conduction electrons for large enough laser intensities. It also increases the time required for the electron distribution to reach the equilibrium state as described by the Fermi-Dirac statistics. Quantitative results are provided for quartz irradiated by a femtosecond laser pulse with a wavelength of 800 nm and for intensities in the range of tens of TW cm-2, lower than the ablation threshold. The change in the energy deposition induced by this non-collisional heating process is expected to have a significant influence on the laser processing of dielectric materials.

  19. A Coplanar Waveguide Resonator Based In-Line Material Characterization Sensor for Bulk and Metallized Dielectrics

    NASA Astrophysics Data System (ADS)

    Talai, Armin; Gold, Gerald; Frank, Martin; Mann, Sebastian; Weigel, Robert; Koelpin, Alexander

    2017-03-01

    Microwave Materials such as Rogers RO3003 are subject to process-related fluctuations in terms of the relative permittivity and dielectric loss. The behavior of high frequency circuits like patch-antenna arrays and their distribution networks is dependent on the effective wavelength. Therefore, fluctuations of the complex permittivity will influence the resonance frequency and beam direction of the antennas. This paper presents a grounded coplanar waveguide based sensor, which can measure the complex permittivity at 77 GHz, as well as at other resonance frequencies, by applying it on top of the manufactured depaneling. The relative permittivity of the material under test (MUT) is a function of the resonance frequency shift and the dielectric loss of the MUT can be determined by transmission amplitude variations at the resonances. In addition, the sensor is robust against floating ground metallizations on inner printed circuit board layers, which are typically distributed over the entire surface below antennas. Furthermore, the impact from conductor surface roughness on the measured permittivity values is determined using the Gradient Model.

  20. Chemically prepared lead magnesium niobate dielectrics

    SciTech Connect

    Tuttle, B.A.; Voigt, J.A.; Sipola, D.L.; Olson, W.R.; Goy, D.M.

    1998-11-01

    A chemical solution powder synthesis technique has been developed that produces first, uniform powders of lead magnesium niobate (PMN) with 60 to 80 nm crystallite size. The synthesis technique was based on the dissolution of lead acetate and alkoxide precursors in acetic acid followed by precipitation with oxalic acid/propanol solutions. Lead magnesium niobate ceramics fabricated from these chemically derived powders had smaller, more uniform grain size and higher dielectric constants than ceramics fabricated from mixed oxide powders that were processed under similar thermal conditions. Chem-prep PMN dielectrics with peak dielectric constants greater than 22,000 and polarizations in excess of 29 {micro}C/cm{sup 2} were obtained for 1,100 C firing treatments. Substantial decreases in dielectric constant and polarization were measured for chemically prepared PMN ceramics fired at lower temperatures, consistent with previous work on mixed oxide materials.

  1. Modelling dielectric-constant values of concrete: an aid to shielding effectiveness prediction and ground-penetrating radar wave technique interpretation

    NASA Astrophysics Data System (ADS)

    Bourdi, Taoufik; Eddine Rhazi, Jamal; Boone, François; Ballivy, Gérard

    2012-10-01

    A number of efficient and diverse mathematical methods have been used to model electromagnetic wave propagation. Each of these methods possesses a set of key elements which eases its understanding. However, the modelling of the propagation in concrete becomes impossible without modelling its electrical properties. In addition to experimental measurements; material theoretical and empirical models can be useful to investigate the behaviour of concrete's electrical properties with respect to frequency, moisture content (MC) or other factors. These models can be used in different fields of civil engineering such as (1) electromagnetic compatibility which predicts the shielding effectiveness (SE) of a concrete structure against external electromagnetic waves and (2) in non-destructive testing to predict the radar wave reflected on a concrete slab. This paper presents a comparison between the Jonscher model and the Debye models which is suitable to represent the dielectric properties of concrete, although dielectric and conduction losses are taken into consideration in these models. The Jonscher model gives values of permittivity, SE and radar wave reflected in a very good agreement with those given by experimental measurements and this for different MCs. Compared with other models, the Jonscher model is very effective and is the most appropriate to represent the electric properties of concrete.

  2. Inorganic optical dielectric films

    NASA Astrophysics Data System (ADS)

    Woollam, John A.

    1996-07-01

    Dielectric coatings have been in use for a very long time, yet today they represent a steadily growing wold-wide industry. A wide range of materials, and applications from the near ultraviolet into the infrared are in use, or under development. This paper is a brief survey, including references to the literature, and a discussion of materials diagnostics. Discussed is the microstructure, optical constants and their relationship as determined especially by optical measurements. This paper emphasizes the materials science aspects rather than applications.

  3. Effect of incorporating aromatic and chiral groups on the dielectric properties of poly(dimethyltin esters).

    PubMed

    Baldwin, Aaron F; Ma, Rui; Huan, Tran Doan; Cao, Yang; Ramprasad, Ramamurthy; Sotzing, Gregory A

    2014-12-01

    High-dielectric constant materials are critical for numerous applications such as photovoltaics, photonics, transistors, and capacitors. There are numerous polymers used as dielectric layers in these applications but can suffer from having a low dielectric constant, small band gap, or ferroelectricity. Here, the structure-property relationship of various poly(dimethyltin esters) is described that look to enhance the dipolar and atomic polarization component of the dielectric constant. These polymers are also modeled using first principles calculations based on density functional theory (DFT) to predict such values as the total, electronic, and ionic dielectric constant as well as structure. A strong correlation is achieved between the theoretical and experimental values with the polymers exhibiting dielectric constants >4.5 with dissipation on the order of 10(-3) -10(-2) .

  4. Meta-lens design with low permittivity dielectric materials through smart transformation optics

    NASA Astrophysics Data System (ADS)

    Kim, Junhyun; Shin, Dongheok; Choi, Seungjae; Yoo, Do-Sik; Seo, Ilsung; Kim, Kyoungsik

    2015-09-01

    We report here a design method based on smart transformation optics (STO) to control the range of the permittivity values of the materials required to manufacture transformation optics devices. In particular, we show that it is possible to reduce the maximum electric permittivity value required to realize a STO device with certain functionality by means of a simple conceptual elastic stretching process. We illustrate the design procedure with two types of collimator meta-lens designs, which we call warping space collimator meta-lens and half fisheye collimator meta-lens, respectively. We provide design examples of these two types of lenses with the help of COMSOL Multiphysics software. These two design examples are fabricated with commonly available dielectric materials by means of 3D printing technology. For the functional verification of these two collimator lenses, we provide measurement results obtained with transverse electric waves of frequency range 7-13GHz.

  5. Polymer/inorganic nanocomposites with tailored hierarchical structure as advanced dielectric materials

    SciTech Connect

    Manias, Evangelos; Randall, Clive; Tomer, Vivek; Polyzos, Georgios

    2012-01-01

    Most advances and commercial successes of polymer/inorganic nanocomposites rely only on the dispersion of nanoparticles in a polymer matrix. Such approaches leave untapped opportunities where performance can be improved by controlling the larger length-scale structures. Here, we review selected examples where the hierarchical structure (from millimeter to nanometer) is tailored to control the transport properties of the materials, giving rise to marked property enhancements, relevant to dielectric materials for power capacitors. These examples address composite structures that are self-assembled, both at the nm and the micron scales, and, thus, can be produced using standard industrial practices. Specifically, polyethylene (PE) blends or poly(vinylidene fluoride) (PVDF) copolymers are reinforced with nanofillers; these composites are designed with high filler orientation, which yielded marked improvements in electric-field breakdown strength and, consequently, large improvements in their recoverable energy densities.

  6. The effects of plasma exposure and vacuum ultraviolet irradiation on photopatternable low-k dielectric materials

    SciTech Connect

    Nichols, M. T.; Mavrakakis, K.; Shohet, J. L.; Lin, Q.

    2013-09-14

    The effects of plasma exposure and vacuum-ultraviolet (VUV) irradiation on photopatternable low-k (PPLK) dielectric materials are investigated. In order to examine these effects, current-voltage measurements were made on PPLK materials before and after exposure to a variety of inert plasma-exposure conditions. In order to examine the effects of photon irradiation alone, PPLK samples were also exposed to monochromatic synchrotron radiation with 10 eV photon energy. It was found that plasma exposure causes significant degradation in electrical characteristics, resulting in increased leakage-currents and decreased breakdown voltage. X-ray photoelectron spectroscopy measurements also show appreciable carbon loss near the sample surface after plasma exposure. Conversely, VUV exposure was found to increase breakdown voltage and reduce leakage-current magnitudes.

  7. OPTIMIZING A PORTABLE MICROWAVE INTERFERENCE SCANNING SYSTEM FOR NONDESTRUCTIVE TESTING OF MULTI-LAYERED DIELECTRIC MATERIALS

    SciTech Connect

    Schmidt, K. F. Jr.; Little, J. R. Jr.; Ellingson, W. A.; Green, W.

    2010-02-22

    The projected microwave energy pattern, wave guide geometry, positioning methods and process variables have been optimized for use of a portable, non-contact, lap-top computer-controlled microwave interference scanning system on multi-layered dielectric materials. The system can be used in situ with one-sided access and has demonstrated capability of damage detection on composite ceramic armor. Specimens used for validation included specially fabricated surrogates, and ballistic impact-damaged specimens. Microwave data results were corroborated with high resolution direct-digital x-ray imaging. Microwave interference scanning detects cracks, laminar features and material properties variations. This paper presents the details of the system, the optimization steps and discusses results obtained.

  8. Secondary Electron Emission from Dielectric Materials of a Hall Thruster with Segmented Electrodes

    SciTech Connect

    A. Dunaevsky; Y. Raitses; N.J. Fisch

    2003-02-12

    The discharge parameters in Hall thrusters depend strongly on the yield of secondary electron emission from channel walls. Comparative measurements of the yield of secondary electron emission at low energies of primary electrons were performed for several dielectric materials used in Hall thrusters with segmented electrodes. The measurements showed that at low energies of primary electrons the actual energetic dependencies of the total yield of secondary electron emission could differ from fits, which are usually used in theoretical models. The observed differences might be caused by electron backscattering, which is dominant at lower energies and depends strongly on surface properties. Fits based on power or linear laws are relevant at higher energies of primary electrons, where the bulk material properties play a decisive role.

  9. Advanced Spin Coating Film Transfer and Hot-Pressing Process for Global Planarization with Dielectric-Material-Viscosity Control

    NASA Astrophysics Data System (ADS)

    Sato, Norio; Machida, Katsuyuki; Yano, Masaki; Kudou, Kazuhisa; Kyuragi, Hakaru

    2002-04-01

    A novel method of controlling the viscosity of dielectric material was developed for global planarization by the spin coating film transfer and hot-pressing (STP) technique. In the STP technique, a base film is spin-coated with a dielectric, the dielectric is hot-pressed to a wafer in vacuum, and the base film is then peeled off from the dielectric. For global planarization in the above steps, the viscosity of the dielectric material is one of the most important factors. We propose controlling the viscosity by vacuum drying in the process chamber. The relationship between viscosity and vacuum drying was investigated experimentally, and the effect of viscosity on gap-filling was clarified by analytical modeling. We applied the control method to STP experiments using patterned wafers and a low-k organic material, and found that it achieves complete gap-filling and good uniformity in film thickness. STP planarized line-and-spaces as large as 100 μm wide achieving a small variation in planarity of ± 0.43%. With this viscosity-control method, the STP technique is applicable to low-k materials.

  10. Temperature dependence of self-consistent full matrix material constants of lead zirconate titanate ceramics

    PubMed Central

    Cao, Wenwu

    2015-01-01

    Up to date, there are no self-consistent data in the literature on the temperature dependence of full matrix material properties for piezoelectric materials because they are extremely difficult to determine. Using only one sample, we have measured the temperature dependence of full matrix constants of lead zirconate titanate (PZT-4) from room temperature to 120 °C by resonant ultrasound spectroscopy. Self-consistency is guaranteed here because all data at different temperatures come from one sample. Such temperature dependence data would make it a reality to accurately predict device performance at high temperatures using computer simulations. PMID:25713470

  11. An overview of high voltage dielectric material for traveling wave kicker magnet application

    SciTech Connect

    Wu Zhang et al.

    2002-08-19

    Pulsed high power fast kickers are being used to change beam trajectories in particle accelerators. The fast rise and fall time of pulse waveform demands a transmission line structure for the kicker deflector design. The ideal design will be parallel metal plates. However, it uses very long straight sections to achieve the required deflection. In accelerators with constrained straight sections, high permeability materials such as ferrite have to be used to gain deflection efficiency. The transmission line kicker magnet is also referred as traveling wave kicker magnet. Its construction is based on distributed L-C cells along the longitudinal direction. The magnetic cells and capacitive cells are interleaved to simulate the characteristic impedance of a transmission line to minimize pulse reflection, and provide adequate frequency bandwidth to transmit the kicker pulse with fast rise and fall time. The magnetic cells are usually made of ferrite ceramics, but the capacitive cells have been made with different materials. For traveling wave kickers with higher impedance, the parallel plate vacuum capacitor has been used in CERN and KEK design. Others have used ceramic capacitors, printed circuit boards, and high permittivity ceramics as the capacitive cell. The high dielectric material has the advantage of compactness for low impedance kicker magnet construction. It continues to be very attractive for future kicker magnet applications. The high voltage phenomena associated with high dielectric ceramic materials have been widely reported in many industrial application areas. Their implication in the traveling wave magnet application has to be well understood. In this presentation, the areas requiring further quantitative study will be outlined.

  12. AN OVERVIEW OF HIGH VOLTAGE DIELECTRIC MATERIAL FOR TRAVELING WAVE KICKER MAGNET APPLICATION.

    SciTech Connect

    ZHANG,W.; SANDBERG,J.; TUOZZOLO,J.; CASSEL,R.; DUCIMETIERE,L.; JENSEN,C.; BARNES,M.; WAIT,G.; WANG,J.

    2002-06-30

    Pulsed high power fast kickers are being used to change beam trajectories in particle accelerators. The fast rise and fall time of pulse waveform demands a transmission line structure for the kicker deflector design. The ideal design will be parallel metal plates. However, it uses very long straight sections to achieve the required deflection. In accelerators with constrained straight sections, high permeability materials such as ferrite have to be used to gain deflection efficiency. The transmission line kicker magnet is also referred as traveling wave kicker magnet. Its construction is based on distributed 1-C cells along the longitudinal direction. The magnetic cells and capacitive cells are interleaved to simulate the characteristic impedance of a transmission line to minimize pulse reflection, and provide adequate frequency bandwidth to transmit the kicker pulse with fast rise and fall time. The magnetic cells are usually made of ferrite ceramics, but the capacitive cells have been made with different materials. For traveling wave kickers with higher impedance, the parallel plate vacuum capacitor has been used in CERN and KEK design. Others have used ceramic capacitors, printed circuit boards, and high permittivity ceramics as the capacitive cell. The high dielectric material has the advantage of compactness for low impedance kicker magnet construction. It continues to be very attractive for future kicker magnet applications. The high voltage phenomena associated with high dielectric ceramic materials have been widely reported in many industrial application areas. Their implication in the traveling wave magnet application has to be well understood. In this presentation, the areas requiring further quantitative study will be outlined.

  13. Polyacrylonitrile-derived polyconjugated ladder structures for high performance all-organic dielectric materials.

    PubMed

    Liao, Xiaojian; Ding, Yichun; Chen, Linlin; Ye, Wan; Zhu, Jian; Fang, Hong; Hou, Haoqing

    2015-06-25

    A novel all-organic polyconjugated ladder structures-polyimide (PcLS-PI) composite was successfully synthesized, in which PcLS were derived from polyacrylonitrile (PAN). The PcLS-PI composite not only presents high dielectric performances of high dielectric permittivity, low dielectric loss, high electrical breakdown strength and high energy density, but also has excellent mechanical and thermal properties.

  14. Simultaneous Non-Contact Precision Imaging of Microstructual and Thickness Variation in Dielectric Materials Using Terahertz Energy

    NASA Astrophysics Data System (ADS)

    Roth, D. J.; Seebo, J. P.; Winfree, William P.

    2008-02-01

    This article describes a non-contact single-sided terahertz electromagnetic measurement and imaging method that simultaneously characterizes microstructural (e.g. spatially-lateral density) and thickness variation in dielectric (insulating) materials. The method was demonstrated for Space Shuttle External Tank sprayed-on foam insulation. It is believed that this method can be used for applications where microstructural and/or thickness variation in dielectric materials require precision mapping. Scale-up to more complex shapes such as cylindrical structures and structures with beveled regions would appear to be feasible.

  15. Near-field light focusing by a slit array in a planar metal film with nonuniform slit dielectric material

    NASA Astrophysics Data System (ADS)

    David Wellems, L.; Huang, Danhong

    2012-02-01

    We study the interference of evanescent electromagnetic waves generated from multi-slits in a metal film and demonstrate the anomalous bending of light at infrared frequencies due to negative refraction. We also calculate the diffraction of an incident plane electromagnetic waves by a metallic film with an arbitrary linear array of slits, slit separation, and slit dielectric material. In contrast to a double-convex shaped quartz lens, we show that a planar metallic film with a one-dimensional slit array can also focus polarized light in the near-field region when either the slit width or the slit dielectric material becomes spatially nonuniform.

  16. Paramagnetic relaxation in anisotropic materials in zero and weak constant fields

    SciTech Connect

    Fokina, N. P.; Khalvashi, E. Kh.; Khutsishvili, K. O.

    2014-12-21

    Paramagnetic relaxation in strongly anisotropic materials is analytically investigated in zero and weak constant magnetic fields. The objectives of the microscopic analytical investigation are (i) the weak-field electron paramagnetic resonance (EPR) linewidth and (ii) the electron spin relaxation rates given by a calorimetric Gorter type experiment in the zero constant field at the arbitrary low-frequency field directions, respectively, to the sample crystallographic axes. The EPR linewidth is calculated under the suggestion of its spin-phonon nature at the one-phonon mechanism of the spin-lattice relaxation in the case of the strong isotropic exchange interaction for the arbitrary direction Z of the constant magnetic field. The EPR linewidth is presented as the half sum of the zero-field relaxation rates, measured by the Gorter experiment with the low-frequency field oriented along the X, Y axes. With the help of the macroscopic consideration, it is shown that the zero-field relaxation rates describe the relaxation of the X and Y magnetization components in a zero or weak constant magnetic field. The relaxation rates of the magnetizations created along a,b,c crystallographic axes by a low-frequency field in a Gorter type experiment follow the obtained expressions in the particular cases and are in the experimentally confirmed relations with the EPR linewidth.

  17. Magneto-dielectric effects induced by optically-generated intermolecular charge-transfer states in organic semiconducting materials.

    PubMed

    Zang, Huidong; Yan, Liang; Li, Mingxing; He, Lei; Gai, Zheng; Ivanov, Ilia; Wang, Min; Chiang, Long; Urbas, Augustine; Hu, Bin

    2013-10-02

    Traditionally, magneto-dielectric effects have been developed by combining ferroelectric and magnetic materials. Here, we show a magneto-dielectric effect from optically-generated intermolecular charge-transfer states in an organic semiconducting donor:acceptor (PVK:TCNB) system. We observe in magnetic field effects of photoluminescence that a magnetic field can change singlet/triplet population ratio in intermolecular charge-transfer states. Furthermore, our theoretical analysis and experimental evidence indicate that the singlets and triplets in charge-transfer states have stronger and weaker electrical polarizations, respectively. Therefore, the observed magneto-dielectric effect can be attributed to magnetically-dependent singlet/triplet ratio in intermolecular charge-transfer states. In principle, a magneto-dielectric effect can be generated through two different channels based on magneto-polarization and magneto-current effects when the singlet/triplet ratio in intermolecular charge-transfer states is changed by a magnetic field. We find, from the simulation of dielectric effects, that magneto-polarization and magneto-current effects play primary and secondary roles in the generation of magneto-dielectric effect.

  18. A single dielectric nanolaser

    NASA Astrophysics Data System (ADS)

    Huang, Tsung-Yu; Yen, Ta-Jen

    2016-09-01

    To conquer Ohmic losses from metal and enhance pump absorption efficiency of a nanolaser based on surface plasmon polariton, we theoretically calculate the first magnetic and electric scattering coefficient of a dielectric sphere under a plane wave excitation with a dielectric constant of around 12. From this calculation, we could retrieve both negative effective permittivity and permeability of the sphere simultaneously at frequencies around 153 THz in the aids of Lewin's theory and the power distribution clearly demonstrate the expected negative Goos-Hänchen effect, which usually occurred in a negative refractive waveguide, thus creating two energy vortices to trap incident energy and then promoting the pump absorption efficiency. Meanwhile, a magnetic lasing mode at 167.3 THz is demonstrated and reveals a magnetic dipole resonance mode and a circulating energy flow within the dielectric sphere, providing a possible stopped light feedback mechanism to enable the all-dielectric nanolaser. More importantly, the corresponding mode volume is reduced to 0.01λ3 and a gain threshold of 5.1×103 is obtained. To validate our design of all-dielectric nanolaser, we employ finite-difference-time-domain simulation software to examine the behavior of the nanolaser. From simulation, we could obtain a pinned-down population inversion of 0.001 and a lasing peak at around 166.5 THz, which is very consistent with the prediction of Mie theory. Finally, according to Mie theory, we can regard the all-dielectric nanolaser as the excitation of material polariton and thus could make an analogue between lasing modes of the dielectric and metallic nanoparticles.

  19. Electrical conductivity of highly concentrated electrolytes near the critical consolute point: A study of tetra-n-butylammonium picrate in alcohols of moderate dielectric constant

    NASA Astrophysics Data System (ADS)

    Oleinikova, A.; Bonetti, M.

    2001-12-01

    The electrical conductivity of highly concentrated solutions of tetra-n-butylammonium picrate (TBAP) in 1-dodecanol (dielectric constant ɛ=4.6) and 1,4-butanediol (ɛ=25.9), and in mixtures of both alcohols, is measured in an extended temperature range ≈10-5<τ<≈10-1, where τ=(T-Tc)/Tc is the reduced temperature with Tc, the critical temperature. The electrical conductivity Λ(T) obeys the Vogel-Fulcher-Tammann (VFT) law for the temperatures far from the critical one. In the temperature range τ<10-2 a systematic deviation of the electrical conductivity from the regular VFT behavior is observed. This deviation is attributed to a critical anomaly. At the critical point the amplitude of the critical anomaly is finite with a value which varies between ≈0.4 and ≈2.7% of Λ(Tc), depending on the solvent. The (1-α) critical exponent describes well the conductivity anomaly, α being the exponent of the specific heat anomaly at constant pressure. The value of the Walden product (Λeqvη), with Λeqv, the equivalent conductivity and η, the shear viscosity, allows the degree of dissociation αdiss of TBAP to be determined at the critical point. αdiss becomes larger for increasing values of ɛ: for TBAP in 1-dodecanol αdiss≈0.25 and in 1,4-butanediol αdiss≈0.73. When the degree of dissociation of the salt is accounted for the Debye screening length is found almost independent on ɛ.

  20. Effects of pressure and temperature on the dielectric constant of GaS, GaSe, and InSe: Role of the electronic contribution

    NASA Astrophysics Data System (ADS)

    Errandonea, D.; Segura, A.; Muñoz, V.; Chevy, A.

    1999-12-01

    In this work we report on direct measurements of the temperature and pressure dependences of the low-frequency dielectric constant along c axis (ɛ∥) of GaS, GaSe, and InSe. The temperature dependence of both the ordinary and extraordinary refractive indexes is also presented. A large increase of ɛ∥ under pressure has been observed. In the framework of a rigid ion model, the lattice contribution to ɛ∥ is shown to increase slightly under pressure, due to the change of the angle between the anion-cation bond and the layer plane. Consequently, the pressure behavior of ɛ∥ is proposed to arise from a large increase of the electronic contribution to ɛ∥. This fact is explained through a decrease of the Penn gap for polarization parallel to the c axis, whose energy and pressure coefficient are shown to scale with those of the indirect band gap in these compounds. A supplementary and reversible step increase of ɛ∥ is observed at 1.6 GPa in GaS, which is associated with a phase transition that has been already observed by other authors.

  1. The effect of dielectric constants on noble metal/semiconductor SERS enhancement: FDTD simulation and experiment validation of Ag/Ge and Ag/Si substrates.

    PubMed

    Wang, Tao; Zhang, Zhaoshun; Liao, Fan; Cai, Qian; Li, Yanqing; Lee, Shuit-Tong; Shao, Mingwang

    2014-02-11

    The finite-difference time-domain (FDTD) method was employed to simulate the electric field distribution for noble metal (Au or Ag)/semiconductor (Ge or Si) substrates. The simulation showed that noble metal/Ge had stronger SERS enhancement than noble metal/Si, which was mainly attributed to the different dielectric constants of semiconductors. In order to verify the simulation, Ag nanoparticles with the diameter of ca. 40 nm were grown on Ge or Si wafer (Ag/Ge or Ag/Si) and employed as surface-enhanced Raman scattering substrates to detect analytes in solution. The experiment demonstrated that both the two substrates exhibited excellent performance in the low concentration detection of Rhodamine 6G. Besides, the enhancement factor (1.3 × 10(9)) and relative standard deviation values (less than 11%) of Ag/Ge substrate were both better than those of Ag/Si (2.9 × 10(7) and less than 15%, respectively), which was consistent with the FDTD simulation. Moreover, Ag nanoparticles were grown in-situ on Ge substrate, which kept the nanoparticles from aggregation in the detection. To data, Ag/Ge substrates showed the best performance for their sensitivity and uniformity among the noble metal/semiconductor ones.

  2. Revisiting the Dielectric Constant Effect on the Nucleophile and Leaving Group of Prototypical Backside Sn2 Reactions: a Reaction Force and Atomic Contribution Analysis.

    PubMed

    Pedraza-González, Laura Milena; Galindo, Johan Fabian; Gonzalez, Ronald; Reyes, Andrés

    2016-10-09

    The solvent effect on the nucleophile and leaving group atoms of the prototypical F(-) + CH3Cl → CH3F + Cl(-) backside bimolecular nucleophilic substitution reaction (SN2) is analyzed employing the reaction force and the atomic contributions methods on the intrinsic reaction coordinate (IRC). Solvent effects were accounted for using the polarizable continuum solvent model. Calculations were performed employing eleven dielectric constants, ε, ranging from 1.0 to 78.5, to cover a wide spectrum of solvents. The reaction force data reveals that the solvent mainly influences the region of the IRC preceding the energy barrier, where the structural rearrangement to reach the transition state occurs. A detailed analysis of the atomic role in the reaction as a function of ε reveals that the nucleophile and the carbon atom are the ones that contribute the most to the energy barrier. In addition, we investigated the effect of the choice of nucleophile and leaving group on the ΔE0 and ΔE(↕) of Y(-) + CH3X → YCH3 + X(-) (X,Y= F, Cl, Br, I) in aqueous solution. Our analysis allowed us to find relationships between the atomic contributions to the activation energy and leaving group ability and nucleophilicity.

  3. Coupled perturbed HF/KS calculation of the dielectric constant of crystalline systems. The case of six members of the garnet family

    NASA Astrophysics Data System (ADS)

    Meyer, A.; Ferrero, M.; Valenzano, L.; Zicovich-Wilson, C. M.; Orlando, R.; Dovesi, R.

    2012-12-01

    The dielectric constant ɛ of pyrope (Mg3Al2(SiO4)3), grossular (Ca3Al2(SiO4)3), andradite (Ca3Fe2(SiO4)3), almandine (Fe3Al2(SiO4)3), spessartine (Mn3Al2(SiO4)3), and uvarovite (Ca3Cr2(SiO4)3) garnets has been calculated by using for the first time the CPHF/KS computational scheme recently implemented in the CRYSTAL code. Garnets are large unit cell (80 atoms in the primitive cell) highly symmetric (Ia3¯d space group) compounds of relevant importance in geology and mineralogy. An all electron Gaussian type Basis Set has been adopted for all atoms. For the four compound containing transition metal atoms the unrestricted formulation of the HF or KS equations has been used. The Basis Set effect has been explored, as well as the influence of the adopted functional, that ranges from LDA to HF through GGA (PBE) and hybrids PBE0 and B3LYP.

  4. Modulation of the adsorption properties at air-water interfaces of complexes of egg white ovalbumin with pectin by the dielectric constant.

    PubMed

    Kudryashova, Elena V; de Jongh, Harmen H J

    2008-02-15

    The possibility of modulating the mesoscopic properties of food colloidal systems by the dielectric constant is studied by determining the impact of small amounts of ethanol (10%) on the adsorption of egg white ovalbumin onto the air-water interface in the absence and presence of pectin. The adsorption kinetics was monitored using tensiometry. The addition of ethanol resulted in considerably slower adsorption of the protein onto the interface, and this effect was enhanced when the protein was in complex with the pectin. Time-resolved fluorescence measurements demonstrated that in the case of noncomplexed ovalbumin the addition of ethanol resulted in a more condensed protein surface layer where ovalbumin adopted a preferred orientation at the interface. In contrast, the effect of ethanol on the ovalbumin-pectin complex suggested a pronounced multipoint electrostatic interaction between protein and polyelectrolyte and the formation of a more rigid spatial arrangement within the complex, thereby leading to suppressed protein-protein interactions. From this work it is concluded that by the enhanced binding affinity between ovalbumin and pectin a strong effect on the adsorption properties of the protein can be accomplished. This work does therefore illustrate how solvent quality can be exploited effectively to enhance or suppress protein functional behavior in complex applications containing air-water interfaces.

  5. Static dielectric constants and molecular dipole distributions of liquid water and ice-Ih investigated by the PAW-PBE exchange-correlation functional.

    PubMed

    Rusnak, Andrew J; Pinnick, Eric R; Calderon, Camilo E; Wang, Feng

    2012-07-21

    The static dielectric constants, ε(s), of ice-Ih and liquid water were calculated using density functional theory with the Perdew-Burke-Ernzerhof (PBE) exchange-correlation functional and the projector-augmented-wave (PAW) approach. Proton disordered ice configurations and uncorrelated liquid configurations were sampled with the electrostatic switching method using force fields specially designed to facilitate the ab initio free energy perturbation calculations. Our results indicate that PAW-PBE underestimates the ε(s) of both ice-Ih and liquid water but predicts the ratio of ice and water ε(s) in good agreement with experimental measurements. PAW-PBE gives average water dipole moments of 2.50 D in ice-Ih and 2.48 D in the liquid. Our results show that the fixed-charge water models developed by adaptive force matching can reproduce the PAW-PBE dipole moments with an error of approximately 5%. The ice and liquid models created in this work have polarizabilities of 1.32 Å(3) and 1.30 Å(3), respectively, along the HOH bisector direction.

  6. Dielectric properties of hybrid perovskites and drift-diffusion modeling of perovskite cells

    NASA Astrophysics Data System (ADS)

    Pedesseau, L.; Kepenekian, M.; Sapori, D.; Huang, Y.; Rolland, A.; Beck, A.; Cornet, C.; Durand, O.; Wang, S.; Katan, C.; Even, J.

    2016-03-01

    A method based on DFT is used to obtained dielectric profiles. The high frequency Ɛ∞(z) and the static Ɛs(z) dielectric profiles are compared for 3D, 2D-3D and 2D Hybrid Organic Perovskites (HOP). A dielectric confinement is observed for the 2D materials between the high dielectric constant of the inorganic part and the low dielectric constant of the organic part. The effect of the ionic contribution on the dielectric constant is also shown. The quantum and dielectric confinements of 3D HOP nanoplatelets are then reported. Finally, a numerical simulation based on the SILVACO code of a HOP based solar cell is proposed for various permittivity of MAPbI3.

  7. Dielectric properties of polyacrylate thick films used in sensors and actuators

    NASA Astrophysics Data System (ADS)

    Jean-Mistral, C.; Sylvestre, A.; Basrour, S.; Chaillout, J.-J.

    2010-07-01

    Dielectric polymers are emerging electro-active materials used in high performance applications such as micropumps, robots and artificial muscles. The development of such applications requires the use of models taking into account the electrical parameters of the material. However, there is still some controversy over the dielectric constant of the most widely used dielectric polymer (VHB 4910, 3M, USA). In this paper, we present an exhaustive study relating to changes in the dielectric constant of VHB 4910 over wide frequency and temperature ranges. We found that the permittivity was a function of: frequency, temperature, the nature of the electrodes and the pre-stress applied to material. Mechanisms of dielectric polarization (β-relaxation) explain the behaviour in temperature and frequency of this parameter. The use of silver grease-compliant electrodes induces an increase in the dielectric constant which moves to a value of 5.4 (against 4.7 with gold electrodes). A pre-strain applied to the material shows a reduction up to 15% in the value of the dielectric constant. Short-range dipolar relaxation, local mechanical constraints in the material and a possible crystallization of material induced by the stretching are suggested to explain these behaviours. Analytic equations of the dielectric constant according to the temperature and pre-strain are then proposed and used to validate the behaviour of these materials for actuator and scavenger devices.

  8. Femtosecond laser ablation of dielectric materials in the optical breakdown regime: Expansion of a transparent shell

    NASA Astrophysics Data System (ADS)

    Garcia-Lechuga, M.; Siegel, J.; Hernandez-Rueda, J.; Solis, J.

    2014-09-01

    Phase transition pathways of matter upon ablation with ultrashort laser pulses have been considered to be understood long-since for metals and semiconductors. We provide evidence that also certain dielectrics follow the same pathway, even at high pulse energies triggering optical breakdown. Employing femtosecond microscopy, we observe a characteristic ring pattern within the ablating region that dynamically changes for increasing time delays between pump and probe pulse. These transient Newton rings are related to optical interference of the probe beam reflected at the front surface of the ablating layer with the reflection at the interface of the non-ablating substrate. Analysis of the ring structure shows that the ablation mechanism is initiated by a rarefaction wave leading within a few tens of picoseconds to the formation of a transparent thin shell of reduced density and refractive index, featuring optically sharp interfaces. The shell expands and eventually detaches from the solid material at delays of the order of 100 ps.

  9. Femtosecond laser ablation of dielectric materials in the optical breakdown regime: Expansion of a transparent shell

    SciTech Connect

    Garcia-Lechuga, M.; Siegel, J. Hernandez-Rueda, J.; Solis, J.

    2014-09-15

    Phase transition pathways of matter upon ablation with ultrashort laser pulses have been considered to be understood long-since for metals and semiconductors. We provide evidence that also certain dielectrics follow the same pathway, even at high pulse energies triggering optical breakdown. Employing femtosecond microscopy, we observe a characteristic ring pattern within the ablating region that dynamically changes for increasing time delays between pump and probe pulse. These transient Newton rings are related to optical interference of the probe beam reflected at the front surface of the ablating layer with the reflection at the interface of the non-ablating substrate. Analysis of the ring structure shows that the ablation mechanism is initiated by a rarefaction wave leading within a few tens of picoseconds to the formation of a transparent thin shell of reduced density and refractive index, featuring optically sharp interfaces. The shell expands and eventually detaches from the solid material at delays of the order of 100 ps.

  10. A compact square loop patch antenna on high dielectric ceramic-PTFE composite material

    NASA Astrophysics Data System (ADS)

    Ullah, M. Habib; Islam, M. T.

    2013-10-01

    Design and prototyping of a low profile, compact square loop microstrip line fed miniature patch antenna on 1.9 mm thick ceramic-polytetrafluoroethylene (PTFE) high dielectric composite material substrate is presented in this paper. The measured -10 dB return loss bandwidths of the antenna are 300 MHz (0.75-1.05 GHz) and 800 MHz (2.4-3.2 GHz) with 3.4 dBi, 8.86 dBi and 7.42 dBi at 900 MHz, 2.5 GHz and 3.0 GHz, respectively. The measured symmetric and almost stable radiation pattern makes the proposed antenna suitable for RFID, GSM, ZIGBEE, WBAN, LR-WPAN etc. integrated mobile devices.

  11. Scheme for Achieving a Topological Photonic Crystal by Using Dielectric Material.

    PubMed

    Wu, Long-Hua; Hu, Xiao

    2015-06-05

    We derive in the present work topological photonic states purely based on conventional dielectric material by deforming a honeycomb lattice of cylinders into a triangular lattice of cylinder hexagons. The photonic topology is associated with a pseudo-time-reversal (TR) symmetry constituted by the TR symmetry supported in general by Maxwell equations and the C_{6} crystal symmetry upon design, which renders the Kramers doubling in the present photonic system. It is shown explicitly for the transverse magnetic mode that the role of pseudospin is played by the angular momentum of the wave function of the out-of-plane electric field. We solve Maxwell equations and demonstrate the new photonic topology by revealing pseudospin-resolved Berry curvatures of photonic bands and helical edge states characterized by Poynting vectors.

  12. Plasmonic data storage medium with metallic nano-aperture array embedded in dielectric material.

    PubMed

    Park, Sinjeung; Won Hahn, Jae

    2009-10-26

    We propose a plasmonic data storage medium with a high-transmission metal aperture array embedded in a dielectric material. Bowtie apertures, having an outline of 80 nm and a ridge gap of 30 nm, are arranged in a two dimensional array with a bit pitch of 100 nm and a track pitch of 280 nm. Using the finite differential time domain (FDTD) method, we calculate the exposure power needed to record optical data, the contrast for readability of recorded data, and cross talk between the main track and adjacent tracks. Compared to a conventional blu-ray disc, the exposure power needed to record optical data in the proposed plasmonic data storage medium is less than a quarter of the conventional threshold power, and the density of the data storage is about 1.8 times larger.

  13. Compound surface-plasmon-polariton waves guided by a thin metal layer sandwiched between a homogeneous isotropic dielectric material and a structurally chiral material

    NASA Astrophysics Data System (ADS)

    Chiadini, Francesco; Fiumara, Vincenzo; Scaglione, Antonio; Lakhtakia, Akhlesh

    2016-03-01

    Multiple compound surface plasmon-polariton (SPP) waves can be guided by a structure consisting of a sufficiently thick layer of metal sandwiched between a homogeneous isotropic dielectric (HID) material and a dielectric structurally chiral material (SCM). The compound SPP waves are strongly bound to both metal/dielectric interfaces when the thickness of the metal layer is comparable to the skin depth but just to one of the two interfaces when the thickness is much larger. The compound SPP waves differ in phase speed, attenuation rate, and field profile, even though all are excitable at the same frequency. Some compound SPP waves are not greatly affected by the choice of the direction of propagation in the transverse plane but others are, depending on metal thickness. For fixed metal thickness, the number of compound SPP waves depends on the relative permittivity of the HID material, which can be useful for sensing applications.

  14. Silicone dielectric elastomers filled with carbon nanotubes and actuator

    NASA Astrophysics Data System (ADS)

    Zhang, Zhen; Liu, Liwu; Deng, Gang; Sun, Shouhua; Liu, Yanju; Leng, Jinsong

    2009-03-01

    Dielectric elastomers (DEs) are one particular type of electroactive polymers. The excellent features of merit possessed by dielectric elastomers make them the most performing materials which can be applied in many domains: biomimetics, aerospace, mechanics, medicals, etc. In order to maximize actuator performance, the dielectric elastomer actuators should have a high dielectric constant and high dielectric breakdown strength. In this paper, multi-walled carbon nanotube (MWNT) is used to develop a particulate composite based on silicone elastomer matrix, with dielectric permittivity improved. And the composite is designed to a new configuration of dielectric elastomer actuator to show electrically activated linear contractions. Prototype samples of this folded actuator, along with the fabrication and analysis is discussed here.

  15. Tunable band alignment and dielectric constant of solution route fabricated Al/HfO2/Si gate stack for CMOS applications

    NASA Astrophysics Data System (ADS)

    Kumar, Arvind; Mondal, Sandip; Koteswara Rao, K. S. R.

    2017-02-01

    The solution route deposition method will reduce the fabrication cost, and it is compatible with existing Si technology. Here, we systematically investigate the impact of annealing temperature on the electrical and dielectric properties along with the band alignment of HfO2 thin films with silicon. The films were fabricated using the hafnium isopropoxide adduct precursor, which is environment friendly and non-toxic in ambient conditions. We have analyzed the band alignment of HfO2/Si stack by using ultra-violet photoelectron spectroscopic and current-voltage (J-V) plot to understand its impact on electrical transport. The bandgap of HfO2 films estimated from Plasmon energy loss spectra is 5.9 eV. The composition analysis is done with X-ray photoelectron spectroscopy that suggests a good stoichiometric ratio of 1:1.96. The atomic force microscopy studies display a smooth surface with the roughness of 1.4 Å without any cracks in the films. It is found that the current conduction mechanisms and barrier heights at both the interfaces are influenced by the annealing temperature; a temperature of 450 °C results in an optimum performance. Interestingly, the high value of dielectric constant (23) in the amorphous phase is attributed to the existence of cubic like short range order in HfO2 films. Moreover, a low leakage current density of 1.4 × 10-9 A/cm2 at -1 V and 1.48 × 10-8 A/cm2 at +1 V in gate and substrate injection modes is achieved. The obtained defect activation energies of 0.91 eV, 0.87 eV, and 0.93 eV for the films annealed at 350 °C, 450 °C, and 550 °C lay below the conduction band edge of HfO2. These energy levels are ascribed to three and four fold oxygen vacancy related traps. The formation of dipoles at the interface, change in the microstructure, and oxygen migration at the interfacial layer are the possible causes for the observed parametric variations in the metal-insulator-semiconductor structure. The electrical properties can be tuned by

  16. Effect of Surface Impulsive Thermal Loads on Fatigue Behavior of Constant Volume Propulsion Engine Combustor Materials

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Fox, Dennis S.; Miller, Robert A.; Ghosn, Louis J.; Kalluri, Sreeramesh

    2004-01-01

    The development of advanced high performance constant-volume-combustion-cycle engines (CVCCE) requires robust design of the engine components that are capable of enduring harsh combustion environments under high frequency thermal and mechanical fatigue conditions. In this study, a simulated engine test rig has been established to evaluate thermal fatigue behavior of a candidate engine combustor material, Haynes 188, under superimposed CO2 laser surface impulsive thermal loads (30 to 100 Hz) in conjunction with the mechanical fatigue loads (10 Hz). The mechanical high cycle fatigue (HCF) testing of some laser pre-exposed specimens has also been conducted under a frequency of 100 Hz to determine the laser surface damage effect. The test results have indicated that material surface oxidation and creep-enhanced fatigue is an important mechanism for the surface crack initiation and propagation under the simulated CVCCE engine conditions.

  17. Purity of (28)Si-Enriched Silicon Material Used for the Determination of the Avogadro Constant.

    PubMed

    D'Agostino, Giancarlo; Di Luzio, Marco; Mana, Giovanni; Oddone, Massimo; Bennett, John W; Stopic, Attila

    2016-07-05

    At present, counting atoms in a one-kilogram sphere made of (28)Si-enriched silicon allows the determination of the Avogadro constant with the 2.0 × 10(-8) relative standard uncertainty required for the realization of the definition of the new kilogram. With the exception of carbon, oxygen, boron, nitrogen, and hydrogen, the claimed uncertainty is based on the postulation that the silicon material used to manufacture the sphere was above a particular level of purity. Two samples of the silicon were measured using instrumental neutron activation analysis to collect experimental data to test the purity assumption. The results obtained in two experiments carried out using different research reactor neutron sources are reported. The analysis confirmed that the silicon material was of sufficient purity by quantifying the ultratrace concentration of 12 elements and determining the detection limits of another 54 elements.

  18. Research on the Crystal Growth and Dielectric Properties of High Permittivity Ferroelectric Materials.

    DTIC Science & Technology

    1984-05-01

    allow many of the underlying mechanisms controlling the microwave dielectric response to be identified. 2 C5988A/Jbs 0D Rockwell International Science...compared to infrared and optical sensors, and re- duced weight and size when compared to conventional microwave radars, have led to increased emphasis... method . Dielectric values along the a- axis are much lower, typically 470 at room temperature and unaffected by poling. Dielectric losses (tan 6) are

  19. Fabrication of CuAl{sub 1−x}M{sub x}O{sub 2} (M = Fe, Cr)/Ni film delafossite compounds using spin coating and their microstructure and dielectric constant

    SciTech Connect

    Diantoro, Markus Yuwita, Pelangi Eka Olenka, Desyana Nasikhudin

    2014-09-25

    The discovery of delafossite compound has encouraged more rapid technological developments particularly in transparent electronic devices. Copper oxide-based transparent thin films delafossite semiconductor recently give much attention in the field of optoelectronic technology, after the discovery of p-type CuAlO{sub 2}. The potential applications of a p-type semiconductor transparent conductive oxides (TCO) have been applied in broad field of optoelectronics. To explore a broad physical properties interms of magnetic conducting subtitution is understudied. In this work we report the fabrication of delafossite film on Ni substrate and their characterization of CuAl{sub 1−x}M{sub x}O{sub 2} delafossite compounds doped with Cr{sup 3+} and Fe{sup 3+} from the raw material of Cu(NO{sub 3}){sub 2}@@‡3H{sub 2}O, Al(NO{sub 3}){sub 3}@@‡9H{sub 2}O, Fe(NO{sub 3}){sub 3}@@‡9H{sub 2}O and Cr(NO{sub 3}){sub 3}@@‡9H{sub 2}O. The films were prepared using spin coating through a sol-gel technique at various concentrations of x = 0, 0.03, 0.04, and 0.05 for chromium and x = 0, 0.02, 0.04, 0.06, and 0.08 for iron doped. Crystal and microstructure were characterized by means of Cu-Kα Bragg-Brentano X-RD followed by High Score Plus and SEM-EDAX. The dielectric constants of the films were characterized using LCR meter. It was found that the CuAl{sub 1−x}M{sub x}O{sub 2}/Ni delafossite films were successfully fabricated. The CuAl{sub 1−x}Fe{sub x}O{sub 2} compound crystallized with lattice parameters of a = b ranged from 2.8603 Å to 2.8675 Å and c ranged from 16.9576 to 17.0763 Å. The increase of the dopant give rise to the increase of the lattice parameters. Since iron has bigger ionic radius (69 pm) than original site of Al{sup 3+} with radius of 53 pm the crystal volume lattice also increase. Further analyses of increasing volume of the crystal, as expected, affected to the decreasing of its dielectric constant. The similar trends also shown by Cr{sup 3+} doped of

  20. W-Band Transmission MeasurementS and X-Band Dielectric Properties Measurements for a Radome Material Sample

    NASA Technical Reports Server (NTRS)

    Cravey, Robin L.; Tiemsin, Pacita I.

    1997-01-01

    This paper describes measurements which were performed on a sample of radome material in the Electromagnetic Properties Measurements Laboratory (EPML). The purpose of the measurements described in this paper was to determine the one-way transmission loss through the flat panel of radome material for a frequency range of 84 to 94 GHz, for varying incidence angles. The panel, which was manufactured by Norton Performance Plastics Corporation, was provided to the EPML by TRW. The size of the panel is 40 in x 36 in x 0.422 in and consists of a foam material with one side coated with a smooth white coating (this side will be referred to as the front side). The dielectric properties of the foam material from the inside of the panel were also determined at X-band (8.2-12.4 GHz). The W-band free space measurements are presented first, followed by the X-band dielectric properties measurements.

  1. Electrode polarization vs. Maxwell-Wagner-Sillars interfacial polarization in dielectric spectra of materials: Characteristic frequencies and scaling laws.

    PubMed

    Samet, M; Levchenko, V; Boiteux, G; Seytre, G; Kallel, A; Serghei, A

    2015-05-21

    The characteristic frequencies of electrode polarization and of interfacial polarization effects in dielectric spectra of ionic liquids and of polymer bi-layers are determined and systematically analyzed, based on dielectric measurements by means of broadband dielectric spectroscopy, numerical simulations, and analytical calculations. It is shown that, to a large extent, identical scaling laws can be derived for these two dielectric phenomena taking place at external and internal interfaces. Surprisingly, a fundamentally different behavior concerning the interrelation between the characteristic frequencies is found. This brings direct evidence that different manifestations of the phenomenon of electrical polarization can be discriminated by examining the inter-relation governing their characteristic frequencies, which can be of significant importance in disseminating the nature of different contributions appearing in the dielectric spectra of complex materials. Based on our analysis, we derive a new formula, valid for both electrode polarization and interfacial polarization effects, that allows one to determine the conductivity value from the frequency position of the Maxwell-Wagner-Sillars peak. An excellent agreement between experiment and calculations is obtained. The formula can be used, furthermore, to estimate the thickness of the interfacial layers formed due to electrode polarization effects. Values in the order of several nanometers, increasing with decreasing temperature, are reported.

  2. Universal solvation model based on solute electron density and on a continuum model of the solvent defined by the bulk dielectric constant and atomic surface tensions.

    PubMed

    Marenich, Aleksandr V; Cramer, Christopher J; Truhlar, Donald G

    2009-05-07

    We present a new continuum solvation model based on the quantum mechanical charge density of a solute molecule interacting with a continuum description of the solvent. The model is called SMD, where the "D" stands for "density" to denote that the full solute electron density is used without defining partial atomic charges. "Continuum" denotes that the solvent is not represented explicitly but rather as a dielectric medium with surface tension at the solute-solvent boundary. SMD is a universal solvation model, where "universal" denotes its applicability to any charged or uncharged solute in any solvent or liquid medium for which a few key descriptors are known (in particular, dielectric constant, refractive index, bulk surface tension, and acidity and basicity parameters). The model separates the observable solvation free energy into two main components. The first component is the bulk electrostatic contribution arising from a self-consistent reaction field treatment that involves the solution of the nonhomogeneous Poisson equation for electrostatics in terms of the integral-equation-formalism polarizable continuum model (IEF-PCM). The cavities for the bulk electrostatic calculation are defined by superpositions of nuclear-centered spheres. The second component is called the cavity-dispersion-solvent-structure term and is the contribution arising from short-range interactions between the solute and solvent molecules in the first solvation shell. This contribution is a sum of terms that are proportional (with geometry-dependent proportionality constants called atomic surface tensions) to the solvent-accessible surface areas of the individual atoms of the solute. The SMD model has been parametrized with a training set of 2821 solvation data including 112 aqueous ionic solvation free energies, 220 solvation free energies for 166 ions in acetonitrile, methanol, and dimethyl sulfoxide, 2346 solvation free energies for 318 neutral solutes in 91 solvents (90 nonaqueous

  3. How do the barrier thickness and dielectric material influence the filamentary mode and CO2 conversion in a flowing DBD?

    NASA Astrophysics Data System (ADS)

    Ozkan, A.; Dufour, T.; Bogaerts, A.; Reniers, F.

    2016-08-01

    Dielectric barrier discharges (DBDs) are commonly used to generate cold plasmas at atmospheric pressure. Whatever their configuration (tubular or planar), the presence of a dielectric barrier is mandatory to prevent too much charge build up in the plasma and the formation of a thermal arc. In this article, the role of the barrier thickness (2.0, 2.4 and 2.8 mm) and of the kind of dielectric material (alumina, mullite, pyrex, quartz) is investigated on the filamentary behavior in the plasma and on the CO2 conversion in a tubular flowing DBD, by means of mass spectrometry measurements correlated with electrical characterization and IR imaging. Increasing the barrier thickness decreases the capacitance, while preserving the electrical charge. As a result, the voltage over the dielectric increases and a larger number of microdischarges is generated, which enhances the CO2 conversion. Furthermore, changing the dielectric material of the barrier, while keeping the same geometry and dimensions, also affects the CO2 conversion. The highest CO2 conversion and energy efficiency are obtained for quartz and alumina, thus not following the trend of the relative permittivity. From the electrical characterization, we clearly demonstrate that the most important parameters are the somewhat higher effective plasma voltage (yielding a somewhat higher electric field and electron energy in the plasma) for quartz, as well as the higher plasma current (and thus larger electron density) and the larger number of microdischarge filaments (mainly for alumina, but also for quartz). The latter could be correlated to the higher surface roughness for alumina and to the higher voltage over the dielectric for quartz.

  4. Grain size effect on the giant dielectric constant of CaCu{sub 3}Ti{sub 4}O{sub 12} nanoceramics prepared by mechanosynthesis and spark plasma sintering

    SciTech Connect

    Ahmad, Mohamad M.; Yamada, Koji

    2014-04-21

    In the present work, CaCu{sub 3}Ti{sub 4}O{sub 12} (CCTO) nanoceramics with different grain sizes were prepared by spark plasma sintering (SPS) at different temperatures (SPS-800, SPS-900, SPS-975, and SPS-1050) of the mechanosynthesized nano-powder. Structural and microstructural properties were studied by XRD and field-emission scanning electron microscope measurements. The grain size of CCTO nanoceramics increases from 80 nm to ∼200 nm for the ceramics sintered at 800 °C and 975 °C, respectively. Further increase of SPS temperature to 1050 °C leads to micro-sized ceramics of 2–3 μm. The electrical and dielectric properties of the investigated ceramics were studied by impedance spectroscopy. Giant dielectric constant was observed in CCTO nanoceramics. The dielectric constant increases with increasing the grain size of the nanoceramics with values of 8.3 × 10{sup 3}, 2.4 × 10{sup 4}, and 3.2 × 10{sup 4} for SPS-800, SPS-900, and SPS-975, respectively. For the micro-sized SPS-1050 ceramics, the dielectric constant dropped to 2.14 × 10{sup 4}. The dielectric behavior is interpreted within the internal barrier layer capacitance picture due to the electrical inhomogeneity of the ceramics. Besides the resistive grain boundaries that are usually observed in CCTO ceramics, domain boundaries appear as a second source of internal layers in the current nanoceramics.

  5. Large dielectric constant ({epsilon}/{epsilon}{sub 0}>6000) Ba{sub 0.4}Sr{sub 0.6}TiO{sub 3} thin films for high-performance microwave phase shifters

    SciTech Connect

    Carlson, C. M.; Rivkin, T. V.; Parilla, P. A.; Perkins, J. D.; Ginley, D. S.; Kozyrev, A. B.; Oshadchy, V. N.; Pavlov, A. S.

    2000-04-03

    We deposited epitaxial Ba{sub 0.4}Sr{sub 0.6}TiO{sub 3} (BST) films via laser ablation on MgO and LaAlO{sub 3} (LAO) substrates for tunable microwave devices. Postdeposition anneals ({approx}1100 degree sign C in O{sub 2}) improved the morphology and overall dielectric properties of films on both substrates, but shifted the temperature of maximum dielectric constant (T{sub max}) up for BST/LAO and down for BST/MgO. These substrate-dependent T{sub max} shifts had opposite effects on the room-temperature dielectric properties. Overall, BST films on MgO had the larger maximum dielectric constant ({epsilon}/{epsilon}{sub 0}{>=}6000) and tunability ({delta}{epsilon}/{epsilon}{>=}65%), but these maxima occurred at 227 K. 30 GHz phase shifters made from similar films had figures of merit (ratio of maximum phase shift to insertion loss) of {approx}45 degree sign /dB and phase shifts of {approx}400 degree sign under 500 V ({approx}13 V/{mu}m) bias, illustrating their utility for many frequency-agile microwave devices. (c) 2000 American Institute of Physics.

  6. Leaf-like nanotips synthesized on femtosecond laser-irradiated dielectric material

    SciTech Connect

    Kiani, Amirkianoosh; Patel, Nikunj B.; Tan, Bo; Venkatakrishnan, Krishnan

    2015-02-21

    Nanotips are the key nanostructures for the improvement of field emission, flat panel displays, force microscopy, and biosensor applications. We propose a single-step, rapid synthesis method to generate nanotips using femtosecond laser irradiation at megahertz frequency with a background flow of nitrogen gas at ambient conditions. Two different types of leaf-like nanotips can be grown on the target surface: randomly oriented multiple tips growing from a single large droplet and single tips growing from small droplets. In this report, we explain the mechanism accountable for the formation of such nanotips using known concepts of laser breakdown of dielectric materials, plasma plume generation, plasma interactions with incoming laser pulses and surrounding gas, as well as known thermal properties of target material. Nitrogen gas plays an interesting role for the resultant structural changes on the target surface and thus it is given special attention in our discussion. Our unique fabrication technique has enabled us to produce tips with nanoscale apexes with a stem and length ranging from few hundred nanometers to few micrometers.

  7. Moisture content prediction of Iranian wheat using dielectric technique.

    PubMed

    Soltani, Mahmoud; Alimardani, Fatemeh

    2014-11-01

    The moisture measurement is the most important criteria in harvesting and post harvesting processing of wheat. This paper investigates the moisture dependent dielectric constant and calibration equation of three most cultivated wheat varieties in Iran. An instrument with a cylindrical capacitive sensor was used to measure the dielectric constant of grain at different moisture contents. Samples were prepared at five levels of moisture content. To validate the proposed equations, the dried material dielectric constant was estimated and compared with the measured ones. Homographic regression models showed an acceptable prediction of dried wheat dielectric constant. Results showed that the calibration equation obtained for Shahriar variety was able to predict the moisture content of other varieties confidently. The lowest value of R (2) = 0.985 between predicted and reference moisture content for Tajan variety is still a good result.

  8. A new numerical technique of electric field determination within dielectric materials plate and cable using the TSM method

    NASA Astrophysics Data System (ADS)

    Belgaroui, E.; Guermazi, H.; Agnel, S.; Mlik, Y.; Toureille, A.

    2003-07-01

    In the frame of the thermal step method (TSM) used to characterize the space charge in dielectric materials, we present an original numerical technique for determining the electric field distribution in the bulk of a dielectric plate or cable. The first stage of our technique is the application of the finite element method (FEM) in order to find instantaneous distributions of temperature profiles. The calculation of the electric field distribution is based on these obtained profiles. During the stage of the determination, our mathematical treatment is based on the TSM charge q(t) in order to avoid numerical instabilities on the temperature derivatives. Therefore, we have transformed the integral equation for the TSM current I(t) used in previous works to an integral equation for the TSM charge q(t). The control of the instantaneous propagation of the thermal wave front, produced by submitting one face of the dielectric to a thermal step, and the application of Simpson's method to the integral equation of the TSM charge q(t), allow to determine the electric field distribution. The results of the electric field distribution are validated with those obtained in previous works. A good agreement and an improvement near the dielectric thickness boundaries are observed on these results. The numerical space charge density within the material is obtained by numerical derivation of the field according to Poisson's equation.

  9. Mechanical property changes in porous low-k dielectric thin films during processing

    NASA Astrophysics Data System (ADS)

    Stan, G.; Gates, R. S.; Kavuri, P.; Torres, J.; Michalak, D.; Ege, C.; Bielefeld, J.; King, S. W.

    2014-10-01

    The design of future generations of Cu-low-k dielectric interconnects with reduced electronic crosstalk often requires engineering materials with an optimal trade off between their dielectric constant and elastic modulus. This is because the benefits associated with the reduction of the dielectric constant by increasing the porosity of materials, for example, can adversely affect their mechanical integrity during processing. By using load-dependent contact-resonance atomic force microscopy, the changes in the elastic modulus of low-k dielectric materials due to processing were accurately measured. These changes were linked to alterations sustained by the structure of low-k dielectric films during processing. A two-phase model was used for quantitative assessments of the elastic modulus changes undergone by the organosilicate skeleton of the structure of porous and pore-filled dielectrics.

  10. Mechanical property changes in porous low-k dielectric thin films during processing

    SciTech Connect

    Stan, G. Gates, R. S.; Kavuri, P.; Torres, J.; Michalak, D.; Ege, C.; Bielefeld, J.; King, S. W.

    2014-10-13

    The design of future generations of Cu-low-k dielectric interconnects with reduced electronic crosstalk often requires engineering materials with an optimal trade off between their dielectric constant and elastic modulus. This is because the benefits associated with the reduction of the dielectric constant by increasing the porosity of materials, for example, can adversely affect their mechanical integrity during processing. By using load-dependent contact-resonance atomic force microscopy, the changes in the elastic modulus of low-k dielectric materials due to processing were accurately measured. These changes were linked to alterations sustained by the structure of low-k dielectric films during processing. A two-phase model was used for quantitative assessments of the elastic modulus changes undergone by the organosilicate skeleton of the structure of porous and pore-filled dielectrics.

  11. Silicon as a virtual plasmonic material: Acquisition of its transient optical constants and the ultrafast surface plasmon-polariton excitation

    SciTech Connect

    Danilov, P. A.; Ionin, A. A.; Kudryashov, S. I. Makarov, S. V.; Rudenko, A. A.; Saltuganov, P. N.; Seleznev, L. V.; Yurovskikh, V. I.; Zayarny, D. A.; Apostolova, T.

    2015-06-15

    Ultrafast intense photoexcitation of a silicon surface is complementarily studied experimentally and theoretically, with its prompt optical dielectric function obtained by means of time-resolved optical reflection microscopy and the underlying electron-hole plasma dynamics modeled numerically, using a quantum kinetic approach. The corresponding transient surface plasmon-polariton (SPP) dispersion curves of the photo-excited material were simulated as a function of the electron-hole plasma density, using the derived optical dielectric function model, and directly mapped at several laser photon energies, measuring spatial periods of the corresponding SPP-mediated surface relief nanogratings. The unusual spectral dynamics of the surface plasmon resonance, initially increasing with the increase in the electron-hole plasma density but damped at high interband absorption losses induced by the high-density electron-hole plasma through instantaneous bandgap renormalization, was envisioned through the multi-color mapping.

  12. Solid state dielectric screening versus band gap trends and implications

    NASA Astrophysics Data System (ADS)

    Ravichandran, Ram; Wang, Alan X.; Wager, John F.

    2016-10-01

    High-frequency (optical) and low-frequency (static) dielectric constant versus band gap trends, as well as index of refraction versus band gap trends are plotted for 107 inorganic semiconductors and insulators. These plots are describable via power-law fitting. Dielectric screening trends that emerge from this analysis have important optical and electronic implications. For example, barrier lowering during Schottky emission, phonon-assisted or Fowler-Nordheim tunneling, or Frenkel-Poole emission from a trap is found to be significantly more pronounced with increasing band gap due to a reduction in the optical dielectric constant with increasing band gap. The decrease in the interface state density with increasing band gap is another optical dielectric constant trend. The tendency for a material with a wider band gap to be more difficult to dope is attributed to an increase in the ionization energy of the donor or acceptor dopant, which in turn, depends on the optical dielectric constant and the effective mass. Since the effective mass for holes is almost always larger than that for electrons, p-type doping is more challenging than n-type doping in a wide band gap material. Finally, the polar optical phonon-limited mobility depends critically upon the reciprocal difference of the optical and the static dielectric constant. Consequently, electron and hole mobility tend to decrease with increasing band gap in a polar material.

  13. Investigation of the Crystal Growth of Dielectric Materials by the Bridgman Technique Using Vibrational Control

    NASA Technical Reports Server (NTRS)

    Feigelson, Robert S.; Zharikov, Evgenii

    2002-01-01

    The principal goal of this ground-based program, which started on February 1, 1998 and concluded on April 30, 2002, was to investigate the influence of low frequency vibrations on the fluid flow and quality of dielectric oxide crystals grown by the vertical Bridgman method. This experimental program was a collaborative effort between Stanford University and the General Physics Institute of the Russian Academy of Sciences in Moscow, and included a strong emphasis on both physical modeling and the growth of some technologically important materials. Additionally it was carried out initially in collaboration with the theoretical and numerical investigations of A.Fedoseyev and I.Alexander (ongoing in another NASA sponsored program). This latter program involved a study of vibro-convective buoyancy-driven flows in cylindrical configurations with the expectation of being able to use vibrational flows to control buoyancy driven fluid transport to off-set the effect of "g-jitter" during microgravity Bridgman crystal growth. These two programs taken together, were designed to lead to a new parametric control variable which can be used to either suppress or control convection, and thereby heat and mass transport during Bridgman crystal growth. It was expected to be effective in either a terrestrial or space environment.

  14. Strong nonlinear electron multiplication without impact ionization in dielectric nanoparticles embedded in optical materials

    SciTech Connect

    Duchateau, Guillaume

    2013-02-15

    The interaction of a dielectric nano-particle or nano-defect, embedded in the bulk of an optical material, with an intense and short laser pulse is addressed. Due to the finite size of the target and the possible large production of electrons in the conduction band, large electric field enhancement or surintensity may be induced inside the particle. Since ionization rates also depend on the instantaneous electric field, a strong time-dependent connection between electron production and surintensity may take place. Such a connection is shown to possibly lead to a nonlinear temporal increase in the free electron density relevant from an avalanche process, called optical avalanche, similar to the one induced by electron impact ionization. However, the present build-up in the electron density clearly exhibits more nonlinear features than traditional collisional avalanche, which is shown to induce an exponential growth of the density: when the optical avalanche is engaged, the temporal electron evolution exhibits an explosive behavior. That leads to a nanometric plasma at solid density whose subsequent laser heating may lead locally to matter under extreme conditions. Furthermore, we show that the defect induces a change in the ionization mechanism in the course of interaction: a transition from multiphoton to tunnel ionization may take place.

  15. Fluorinated and Thermo-Cross-Linked Polyhedral Oligomeric Silsesquioxanes: New Organic-Inorganic Hybrid Materials for High-Performance Dielectric Application.

    PubMed

    Wang, Jiajia; Sun, Jing; Zhou, Junfeng; Jin, Kaikai; Fang, Qiang

    2017-04-12

    A fluorinated and thermo-cross-linked polyhedral oligomeric silsesquioxane (POSS) has been successfully synthesized by thermal polymerization of a fluorinated POSS monomer having an inorganic silsesquioxane core and organic side chains bearing thermo-cross-linkable trifluorovinyl ether groups. This new inorganic-organic hybrid polymer shows high thermostability with a 5 wt % loss temperature of 436 °C, as well as good transparency (a sheet with an average thickness of 1.5 mm shows high transmittance of 92% varying from 400 to 1100 nm). Moreover, the polymer exhibits both low dielectric constant (<2.56) and low dissipation factor (<3.1 × 10(-3)) in a wide range of frequencies from 40 Hz to 30 MHz even at a high frequency of 5 GHz. The polymer also shows low water uptake (<0.04%) and low Dk (near 2.63) after immersing it in water at room temperature for 3 days. These data imply that this polymer is very suitable to be utilized as a high-performance dielectric material for fabrication of high-frequency printed circuit boards or encapsulation resins for integrated circuit dies in the microelectronic industry. Furthermore, this work also provides a route for the preparation of fluorinated POSS-based polymers.

  16. Measurement of Space Charges in Dielectric Materials by Pulse Electro-acoustic Method after Irradiation by High-energy Electron Beam

    NASA Astrophysics Data System (ADS)

    Xiaogang, Qin; Kai, Li; Mayali; Xiaoquan, Zheng; Xiaodong, Liu

    2009-01-01

    Dielectric materials are widely used in space environment. When they are irradiated, charges will accumulate in the bulk and on the surface of the material, leading to pulse discharge events that can cause permanent changes in their physical and chemical structure. In this paper, a special method called PEA (pulse electro-acoustic) was used to measure and analyze the space charging of several dielectric materials after they have been irradiated by different high-energy electron beams.

  17. Debye-temperature-elastic-constants relationship for materials with hexagonal and tetragonal symmetry

    NASA Astrophysics Data System (ADS)

    Siethoff, Hans; Ahlborn, Karl

    1996-03-01

    In the literature a relation is often used that correlates Debye temperature and bulk modulus by a square-root law. It was recently shown that, for different cubic crystal structures, such a law is only fulfilled within relatively large error limits. If one takes, however, the average of the elastic constants of the transversal acoustic phonon modes as elastic modulus instead of the bulk modulus, the square-root law is established with high precision. It is demonstrated that the same procedure may also be applied successfully to materials with hexagonal crystal symmetry such as hexagonal close-packed metals and semiconducting compounds with the wurtzite structure, and to different structures of the tetragonal system. The adequate moduli are Gh={c44[c44(c11-c12)/2]1/2} 1/2 and Gt=[c44c66(c11-c12)/2]1/3 for materials with hexagonal and tetragonal symmetry, respectively. The difference between the various structures of a crystal system is quantitatively described by the different number of atoms in the crystallographic unit cell.

  18. Design rules for the optimization of the sensitivity of open-ended coaxial microwave sensors for monitoring changes in dielectric materials

    NASA Astrophysics Data System (ADS)

    García-Baños, Beatriz; Catalá-Civera, José M.; Canós, Antoni J.; Peñaranda-Foix, Felipe

    2005-05-01

    Open-ended coaxial probes are widely used for non-destructive measurement of dielectric properties of materials, and also as microwave sensors for industrial processes and quality control applications. The main design parameters of these sensors are the coaxial radii and working frequency. In this paper, the influence of these variables on the final sensitivity of the coaxial sensor when monitoring dielectric materials is analysed, and a novel expression for this parameter selection is proposed. Moreover, a method to select the optimum parameters of experimental configurations is provided. Measurements demonstrate that high discrimination can be achieved with this method when monitoring changes in the dielectric properties of materials.

  19. Cast dielectric composite linear accelerator

    DOEpatents

    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.

  20. Dipole analysis of the dielectric function of color dispersive materials: Application to monoclinic Ga2O3

    NASA Astrophysics Data System (ADS)

    Sturm, C.; Schmidt-Grund, R.; Kranert, C.; Furthmüller, J.; Bechstedt, F.; Grundmann, M.

    2016-07-01

    We apply a generalized model for the determination and analysis of the dielectric function of optically anisotropic materials with color dispersion to phonon modes and show that it can also be generalized to excitonic polarizabilities and electronic band-band transitions. We take into account that the tensor components of the dielectric function within the Cartesian coordinate system are not independent of each other but are rather projections of the polarization of dipoles oscillating along directions defined by the, non-Cartesian, crystal symmetry and polarizability. The dielectric function is then composed of a series of oscillators pointing in different directions. The application of this model is exemplarily demonstrated for monoclinic (β -phase) Ga2O3 bulk single crystals. Using this model we are able to relate electronic transitions observed in the dielectric function to atomic bond directions and orbitals in the real space crystal structure. For a thin film revealing rotational domains we show that the optical biaxiality is reduced to uniaxial optical response.