Showing papers on "Dielectric published in 1993"

Dielectric polarizabilities of ions in oxides and fluorides

Abstract: A set of 61 ion polarizabilities has been derived from the dielectric constants of 129 oxides and 25 fluorides using a least squares refinement technique in conjunction with the Clausius–Mosotti equation. These polarizabilities can be used to estimate mean dielectric constants of ‘‘well‐behaved’’ compounds. They should be particularly useful in calculation of mean dielectric constants of compounds whose dielectric constants have not been determined. They can also be used as a framework for distinguishing unusual dielectric behavior from normal dielectric behavior where deviations can frequently be attributed to piezo‐ or ferroelectricity, conductivity (ionic or electronic), ‘‘rattling’’ or ‘‘compressed’’ cations with correspondingly high or low polarizabilities, or the presence of dipolar impurities. Deviations observed from calculated dielectric constants can be used to search for unusual physical behavior.

Microscale Heat Conduction in Dielectric Thin Films

Abstract: Heat conduction in dielectric thin films is a critical issue in the design of electronic devices and packages. Depending on the material properties, there exists a range of film thickness where the Fourier law, used for macroscale heat conduction, cannot be applied. In this microscale regime, heat transport by lattice vibrations or phonons can be analyzed as a radiative transfer problem. Based on Boltzmann transport theory, an equation of phonon radiative transfer (EPRT) is developed. In the acoustically thick limit, ξ L >>1, or the macroscale regime, where the film thickness is much larger than the phonon-scattering mean free path, the EPRT reduces to the Fourier law

Double-slot antennas on extended hemispherical and elliptical silicon dielectric lenses

Abstract: Far-field patterns and Gaussian-beam coupling efficiencies are investigated for a double-slot antenna placed on hemispherical lenses with varying extension lengths. The radiation patterns of a double-slot antenna on a silicon dielectric lens are computed using ray-tracing inside the dielectric lens and electric and magnetic field integration on the spherical dielectric surface. The measured radiation patterns at 246 GHz and Gaussian-beam coupling efficiencies show good agreement with theory. The theoretical results are presented in terms of extension-length/radius and radius/ lambda , and therefore result in universal design curves for silicon lenses of different diameters and at different frequencies. The theoretical and experimental results indicate that for single units, there exists a wide range of extension lengths which result in high Gaussian-coupling efficiencies (50-60%) to moderately high f 's. These Gaussian-coupling efficiencies can be increased to 80-90 degrees % with the use of a lambda /sub m//4 matching-cap layer. For imaging array applications with high packing densities, an extension-length/radius of 0.38 to 0.39 (depending on frequency) will result in peak directivity and a corresponding Gaussian-coupling efficiency 15-20% lower than for single units. >

Macroscopic Models of Aqueous Solutions: Biological and Chemical Applications

Abstract: A theoretical approach to the treatment of solute-solvent interactions is described. The solute is described as a low dielectric cavity immersed in a dielectric continuum. However, the cavity is not assigned a simple geometric form but rather is determined from the van der Waals envelope of the molecule. Real and partial charges are placed on atomic nuclei as in any molecular mechanics force field. Dielectric and ionic strength effects are obtained through numerical solutions to the Poisson-Boltzmann equation, which has proved to be remarkably accurate for a wide range of applications

Appearance of stable glow discharge in air, argon, oxygen and nitrogen at atmospheric pressure using a 50 Hz source

Abstract: Unusual glow discharges in air, argon, oxygen and nitrogen at atmospheric pressure can be produced using a 50 Hz source. This technique is introduced on the basis of the idea of a lower dielectric breakdown voltage gas. The electrode system, which is composed of a fine metal wire mesh of specified radius and a dielectric substance, is very useful for plasma surface processes and for chemical reactions in the plasma bulk. The observations of the Lissajous figure of voltage-electric charges and of the current pulse shapes are proposed as a method of distinguishing between the atmospheric pressure glow plasma and the silent electric discharge.

Dielectric Properties of Wood and Wood-Based Materials

Abstract: 1 Interaction between the Electromagnetic Field and Wood. Main Features of Dielectric Properties of Wood.- 1.1 Polarization of Wood.- 1.2 Dielectric Parameters of Wood.- 1.3 Some Principal Formulas Reflecting Interactions Between an Electromagnetic Field and a Material.- 2 Wood Composition and Dielectric Properties of Its Components..- 2.1 Physical Model of Wood as a Multicomponent Dielectric.- 2.2 Dielectric Parameters of the Cell Wall Substance and Its Elements.- 2.3 Dielectric Characteristics of Air, Free and Bound Water, and Ice.- 3 Measurement of the Dielectric Properties of Wood.- 3.1 Measurement of the Dielectric Constant and Loss Tangent at Low Frequencies.- 3.2 Measurements of the Dielectric Constant and Loss Tangent at High Frequencies.- 3.3 Measurement of the Dielectric Constant and Loss Tangent at Super High Frequencies.- 3.4 Preparation of Samples.- 4 Dielectric Properties of Oven-Dry Wood.- 4.1 Influence of Anisotropy, Density, and Frequency on the Dielectric Constant, Loss Tangent, and Loss Factor.- 4.2 Influence of Temperature on Dielectric Properties.- 5 Dielectric Properties of Moist Wood.- 5.1 The Dielectric Constant of Moist Wood.- 5.2 The Dielectric Loss Tangent of Moist Wood.- 5.3 The Dielectric Loss Factor of Moist Wood.- 5.4 Mechanism of the Influence of Moisture Content on the Dielectric Properties of Wood.- 6 Effect of Different Kinds of Treatment on the Dielectric Properties of Wood.- 6.1 Dielectric Properties of Compressed Wood.- 6.2 Dielectric Characteristics of Modified Wood.- 6.2.1 Wood Treated with Ammonia.- 6.2.2 Dielectric Properties of Wood Impregnated with Various Substances.- 6.3 Influence of Gamma-Radiation on the Dielectric Properties of Wood.- 7 Dielectric Properties of Bark.- 8 Dielectric Properties of Wood-Based Materials.- 8.1 Cellulose, Paper and Board.- 8.1.1 Influence of Density Value, Moisture Content, and Temperature on the Dielectric Properties of the Material.- 8.1.2 Influence of the Structure of Paper and Board on Their Dielectric Properties.- 8.1.3 Influence of Organic and Mineral Inclusions on the Dielectric Properties of Cellulose-Based Materials.- 8.2 Fiberboards.- 8.3 Particleboards.- 8.4 Materials Containing Wood, Cellulose, Paper (as a Filler), and Cellulose Derivatives.- 9 Recommendations for the Determination of the Dielectric Parameters of Wood and Wood-Based Materials and for Their Use in Calculations.- 9.1 Dielectric Parameters and Density of Oven-Dry Wood.- 9.2 Averaging the Dielectric Parameters Values.- 9.3 Choice of Frequency on Microwave Treatment of Wood.- Appendices.- References.

Dielectric constant for binary piezoelectric 0‐3 composites

Abstract: In this article an analytic expression is presented for the dielectric constant of a binary piezoelectric 0‐3 composite by modifying the well known Kerner expression [Proc Phys Soc London Sec B 69, 802 (1956)] to include interactions The developed expression is a function of the constituent dielectric constants and their volume fractions only and compares very favorably with available experimental data for piezoelectric ceramic inclusions in a dielectric continuum having widely differing dielectric constants

Materials constants of KNbO3 relevant for electro‐ and acousto‐optics

Abstract: The elastic, piezoelectric, dielectric, elasto‐optic, and electro‐optic tensors have been determined by numerically evaluating the measurements published until now and using the additional measurements presented in this work. The dependence of the speed of two elastic waves on the applied electric field is measured yielding one electroelastic constant g13133=(95±10)NV−1 m−1. The complete set of parameters consisting of the low‐frequency clamped dielectric constants eSij, refractive indices, elastic stiffness constants at constant electric field CEijkl, piezoelectric coefficients eijk, elasto‐optic tensor at constant electric field pEijkl, and clamped electro‐optic coefficients rSijk is used to calculate effective electro‐optic coefficients and effective dielectric constants that have to be used in photorefractive experiments where the elastic deformations associated with a periodic space‐charge field have to be considered.

The Spontaneous Relaxor-Ferroelectric Transition of Pb(Sc0.5ta0.5)O3

Abstract: A zero-field spontaneous relaxor-ferroelectric transition is reported in Pb(Sc0.5Ta0.5)O3 (PST). This behavior is different from that of other relaxors, where such transitions occur only under the field. A highly disordered PST that has the wide relaxation spectrum typical of relaxors is shown to transform spontaneously into a macroscopic ferroelectric state. Introduction of defects (lead vacancies) into the material impedes the transition resulting in the usual relaxor behavior. Dielectric properties of PST, with and without defects, are analyzed. For the interpretation of the observed properties, a model invoking an additional nonpolar phase is proposed. This model does not imply a freezing in the system. At the low-frequency limit, it is possible to account for the Vogel-Fulcher (VF) law for the temperature of the maximum of the dielectric constant, using only the commonly accepted assumption of an exponentially wide relaxation time spectrum that shrinks on heating. The presented approach interprets the observed proximity between the ferroelectric phase transition temperature and that of the freezing temperature obtained from the VF relation.

Method of manufacturing silicon oxide film containing fluorine

Abstract: Disclosed is a method of manufacturing a semiconductor device, in which a silicon oxide film containing fluorine, said film exhibiting a low dielectric constant and a low hygroscopicity and acting as an insulating film for electrically isolating wirings included in a semiconductor device, is formed by a plasma CVD method using a source gas containing at least silicon, oxygen and fluorine, under the conditions that the relationship between the gas pressure P (Torr) and the ion energy E (eV) satisfies formula A given below: P≧5×10.sup.-4,P≦10.sup.-1 ×10.sup.-E/45(A) and the relationship between the ion energy E (ev) and the plasma density D (/cm 3 ) satisfies the formula B given below: D≧2×10.sup.11 ×10.sup.-E/45, 10≦E(B)

Light scattering and dielectric studies on glass forming liquids

Abstract: The α-relaxation behaviour of polymers and glass forming viscous liquids is well described by the Vogel-Fulcher-Tammann equation, introducing a Vogel temperature T0 at which the relaxation time τα diverges (T0 ≈ Tg - 50 K). With the recent development of the mode coupling theory a new critical temperature Tc is introduced located about 50 to 80 K above Tg. The relevance of the various temperatures is discussed on the basis of dynamic light scattering studies and dielectric relaxation data. The dynamic and static light scattering experiments revealed some unexpected features, which cannot be explained on the basis of conventional liquid state theories: (1) In static light scattering the intensity I(q→0) is no longer proportional to the isothermal compressibility. (2) This excess scattering Iexc shows a strong q-dependence (q = (4πn/λ)sin(θ/2)) corresponding to a correlation length ξ in the range of 20–200 nm. (3) The Landau-Placzek ratio IRayleigh/2IBrillouin is much too high, compared with the results of light scattering theories. (4) In photon correlation spectroscopy a new ultraslow hydrodynamic mode (Γ∼q2) is detected with relaxation rates Γ about 10-4 to 10-7 lower than those of the α-process at a given temperature. These effects are caused by long density fluctuations indicating a nonhomogeneous distribution of free volume. The redistribution of free volume in space causes the new ultraslow mode. A tentative model is proposed which describes the long range density fluctuations as a result of the coexistence of molecules with two different dynamic states, which show up in the Fabry-Perot and Raman spectroscopy.

High dielectric constant capacitor and method of manufacture

Abstract: A high storage capacity capacitor for a semiconductor structure includes a barrier layer formed on a polysilicon electrode, a lower electrode, a dielectric layer, and an upper electrode. The dielectric material is formed of a high dielectric constant material such as BaSrTiO 3 . In order to protect the barrier layer from oxidation during deposition of the dielectric layer and to provide a smooth surface geometry for depositing the dielectric layer, conducting or insulating spacers are formed on the sidewalls of the barrier layer and lower electrode. A smooth dielectric layer can thus be formed that is less susceptible to current leakage. In addition, the insulating spacers can be formed to completely fill a space between adjacent capacitors and to provide a completely planar surface.

Dielectric Properties of (Ba, Sr)TiO3 Thin Films Deposited by RF Sputtering

Abstract: Thin films of (Ba0.65Sr0.35)TiO3 (BST) have been prepared by an rf-sputtering method at substrate temperatures of 500 to 700°C. The dielectric constant of these films ranges from 190 to 700 at room temperature. This value changes with the grain size rather than the film thickness. The dielectric constant of about 300 and leakage current density of about 1×10-8 A/cm2 are obtained in the 65-nm-thick film deposited at a substrate temperature of 600°C. This shows the BST film can be applied to dielectrics of dynamic random access memory (DRAM) capacitors.

Generation of shock waves by laser‐induced plasma in confined geometry

Abstract: Confined plasmas induced by neodynium glass laser at 1.06 μm and pulse width of 3 and 30 ns are studied. The metallic target is covered with a dielectric layer, glass or water, transparent to the laser radiation. Experimental measurements of the pressure induced by the plasma have been performed. For a certain range of laser power density these measurements agree particularly well with an analytical model. At high power densities (10 GW/cm2), the dielectric breakdown appears to be the main limiting process of the confining method. It is observed that this breakdown induces a saturation of the pressure. It is shown that the use of a short‐rise‐time laser pulse is the only way to reduce the effects of the breakdown and to obtain much higher‐pressure shock waves. This is due to the dependence of the dielectric breakdown threshold on the laser pulse rise time.

Optical, dielectric and polarization studies of the electric field-induced phase transition in Pb(Mg1/3Nb2/3)O3 [PMN]

Abstract: Single crystals of PMN have been studied between 10 and 300 K by means of dielectric, polarization and poling/depoling current measurements, associated with optical domain observations under bias field. Evidence for a first order electric field-induced phase transition, from the mean cubic phase to a macroscopically polar phase, has been disclosed by studying, as a function of temperature, the dielectric anomalies, the establishment of induced polarization, the onset of poling current and the appearance of the birefringence and phase boundary. By means of combined optical and domain switching analysis, the symmetry of the induced phase has been deduced to be trigonal 3m. The induced macropolarization Pind can be switched by a field of opposite polarity. The thermal depoling under a bias field takes place at a temperature depending on the field strength, whereas the zero-field depoling of an induced state occurs always at T do = 213 K, independently of the initial poling field. An electric field/t...

Acrylate coating material

Abstract: Material for winding high voltage capacitors is prepared by evaporating polyfunctional acrylate monomer having a molecular rate in the range of from 150 to 600 and condensing the acrylate as a monomer film on a dielectric substrate. The acrylate is polymerized by irradiation by ultraviolet or electrons. Sometimes both faces of the dielectric are coated to protect the thermoplastic dielectric from swelling when exposed to dielectric liquid. The metallized layer provides an electrode of the capacitor. A polymerized acrylate layer may be applied over the metal layer. Electrical contact can be made to the metal layer by Schooping even though the metallized layer is covered by a layer of acrylate. Low oxygen permeability polypropylene, polyester or nylon sheet has a layer of crosslinked acrylate and an oxygen barrier layer formed of silicon oxide, aluminum oxide or metal. Adhesion is enhanced by plasma or corona treatment of a surface immediately before deposition. Condensation efficiency is also enhanced by chilling the substrate on which the acrylate is condensed.

Models for breakdown-resistant dielectric and ferroelectric ceramics

Abstract: Models for dielectric breakdown are proposed and analysed, with emphasis on concepts leading to breakdown-resistant materials. The Griffith energy balance is extended to cracks under combined electrical and mechanical loading, and to conductive tubular channels. Breakdown strength for a perfect crystal is estimated by an analogue of the Frenkel model. In a crystal subjected to an electric field the equilibrium displacement of the electron clouds is described by a curve with periodicity of the lattice constant. A theory of breakdown-resistant laminates is proposed on the basis of charge relocation, facilitated by breakdown of the weak layers and the interfaces. A process by which a conducting path grows like a crack in ferroelectric ceramics is discussed, followed by an outline of fields around conducting cracks in piezoelectric ceramics.

Dielectric properties of tetragonal lanthanum modified lead zirconate titanate ceramics

Abstract: Tetragonal La‐modified lead zirconate titanate ceramics with a Zr/Ti ratio of 40/60 (x/40/60) with La contents (x) between 0 and 21 at. % were prepared by the mixed oxide method and were subsequently characterized using dielectric spectroscopy. Small La contents tended to diffuse the dielectric response in the temperature region around the phase transition, however, no distinct changes were observed in the paraelectric region. Compositions with intermediate La contents showed a thermally driven (spontaneous) transformation from a relaxor to a normal ferroelectric, i.e., micro‐macro domain switching. Materials with a high La content exhibited typical relaxor ferroelectric behavior. The relative thermodynamic stability of the ensemble of micropolar regions is then discussed in reference to that of the long‐range ferroelectric state.

Method to slope conductor profile prior to dielectric deposition to improve dielectric step-coverage

Abstract: A process for semiconductor manufacture in which the top corners of conductive features are preferentially etched compared to the etch rate of the vertical and horizontal surfaces, thereby creating a sloped (prograde) profile, i.e., facets. The material removed through the sputter etch process is oxidized and redeposited along the sides of the feature and along the surface of the substrate, thereby improving step coverage when a subsequent dielectric layer is deposited thereon.

Theory and experiment of a coaxial probe fed hemispherical dielectric resonator antenna

Abstract: A hemispherical dielectric resonator antenna fed by a coaxial probe is studied both theoretically and experimentally. The Green's function for the evaluation of the input impedance is derived rigorously and expressed in a form convenient for numerical computations. The method of moments is used to obtain the probe current from which the input impedance of the DR antenna is calculated. Both delta gap and magnetic frill source models are considered. Moreover, the results using a reduced kernel as well as the exact kernel are presented. Both entire basis (EB) and piecewise sinusoidal (PWS) expansion modes are used and the results are compared. The effects of the probe length, feed position, and dielectric constant on the input impedance are discussed. Finally, the theoretical radiation patterns for the first three resonant modes (TE/sub 111/, TM/sub 101/, and TE/sub 221/) of the DR antenna are presented. >

Structural and electrical characteristics of SrTiO3 thin films for dynamic random access memory applications

Abstract: Polycrystalline SrTiO3 thin films having perovskite structure were prepared by the metallo‐organic solution deposition technique on platinum coated silicon and bare silicon substrates. Crack free and crystalline films with uniform composition and thickness were fabricated by spinning and post deposition rapid thermal annealing at a low temperature of 550 °C for 60 s. The films exhibited good structural, dielectric, and insulating properties. The dielectric constant was found to depend on film thickness and annealing temperature. The small signal dielectric constant and dissipation factor at a frequency of 100 kHz were 225 and 0.008, respectively, for a 0.8‐μm‐thick film annealed at 700 °C for 60 s. The frequency dependence of the dielectric constant and the dielectric loss was also studied. The measurement of the current‐voltage (I‐V) characteristics on films in metal‐insulator‐metal configuration indicated the conduction process to be bulk limited. The I‐V characteristics were ohmic at low fields and spa...

Dielectric properties of aerogels

Abstract: We have measured the real (dielectric constant) and imaginary (loss factor) components of the complex relative permittivity at 298 K using microwave frequencies (2, 10, and 18–40 GHz) for bulk SiO2-aerogels and for two types of organic aerogels, resorcinol-formaldehyde (RF) and melamine-formaldehyde (MF). Measured dielectric constants are found to vary linearly between values of 1.0 and 2.0 for aerogel densities from 10 to 500 kg/m3. For the same range of densities, the measured loss tangents vary linearly between values of 2 × 10−4 and 7 × 10−2. The observed linearity of the dielectric properties with density in aerogels at microwave frequencies shows that their dielectric behavior is more gas-like than solid-like. The dielectric properties of aerogels are shown to be significantly affected by the adsorbed water internal to the bulk material. For example, water accounts for 70% of the dielectric constant and 70% of the loss at microwave frequencies for silica aerogels. Because of their very high porosity, even with the water content, the aerogels are among the few materials exhibiting such low dielectric properties. Our measurements show that aerogels with greater than 99% porosity have dielectric constants less than 1.03; these are the lowest values ever reported for a bulk solid material.

Anomalies in the scaling of the dielectric alpha -relaxation.

Abstract: By measuring the complex dielectric function over 15 decades in frequency we evaluate the scaling of the α-relaxation for several glass-forming liquids including propylene carbonate. The temperature dependence of the mean relaxation time and of the relaxation strength of the relaxation function displays two dynamical regions being separated by a crossover temperature. The observed findings are essentially not in 'accordance with predictions of the mode-coupling theory and light scattering results for propylene carbonate [M. Elmroth et al., Phys. Rev. Lett. 68, 79 (1992)]

Leaky-wave propagation and radiation for a narrow-beam multiple-layer dielectric structure

Abstract: Previous work has demonstrated that very narrow beam radiation patterns can be obtained from a simple source embedded within multiple dielectric layers of appropriate thicknesses above a ground plane. The configuration consists of dielectric layers having permittivities epsilon /sub 1/ and epsilon /sub 2/ stacked in an alternating arrangement, with epsilon /sub 2/> epsilon /sub 1/. This narrow-beam effect can be attributed to weakly attenuated leaky waves that exist on the structure. Simple asymptotic formulas for the propagation and attenuation constants are derived. The formulas show how the beamwidth varies with the number of layers and the material constants. The exact radiation pattern is compared with the leaky-wave pattern for a specific case to demonstrate the role of the leaky waves in determining the total pattern. >

Through hole interconnect substrate fabrication process

Abstract: A high density through-hole interconnect with high aspect ratio vias is formed by sequentially forming layers of dielectric material on a previous dielectric layer. After each layer is formed, a plurality of through holes are etched through each layer and filled or metalized with an electrically conductive material having a coefficient of thermal expansion matching that of the dielectric layers and the integrated circuit that it will connect with. Preferably, the process of forming dielectric layers, forming through holes, and metalizing the through holes is repeated until the metalized through holes have an aspect ratio in the range of from 6 to 10. A support structure is constructed to interconnect with and support the metalized vias while the dielectric material is removed. A second dielectric material having the desired mechanical and electrical properties is poured into the support structure to fill the space between the metalized vias and allowed to solidify. The support structure is removed and the through-hole interconnector, comprising the metalized vias and the second dielectric material, is lapped and polished to predetermined manufacturing dimensions and tolerances.

Dielectric properties of trypsin inhibitor and lysozyme calculated from molecular dynamics simulations

Abstract: The static and frequency dependent dielectric properties of trypsin inhibitor and hen egg white lysozyme have been calculated from the fluctuations in the total dipole moment of the two proteins. Total dipole moment fluctuations were obtained from long molecular dynamics simulations of both proteins in an explicit solvent environment. Despite differences in the total charge, volume, shape and secondary structure composition of the two proteins, consistent values for the dielectric constant were obtained. The static dielectric constant of trypsin inhibitor was calculated to be 36, compared with a value of 30 for hen egg white lysozyme. Convergence in the calculations required 1 ns of simulation. The calculated frequency dependent dielectric constant was also consistent with known experimental dielectric dispersion curves for proteins in aqueous solution. The implications for free energy calculations involving significant charge redistribution are also discussed.

Fabry-perot with device mirrors including a dielectric coating outside the resonant cavity

Abstract: In a Fabry-Perot etalon or interferometer the metal mirrors are each provided with a dielectric coating on the side facing away from the enclosed gap. The dielectric coating leads to the advantage of peak transmittance being improved without the finesse being adversely affected. The dielectric coating is transparent for the wavelength (λ) used and, preferably, has a thickness of about 0.25λ/n, n being the refractive index of the dielectric coating material. The coating, preferably, is of a material having a high index of refraction, examples thereof including zirconium dioxide, titanium dioxide, zinc sulfide, or zinc selenide.

Low dielectric constant insulation layer for integrated circuit structure and method of making same

Abstract: A low dielectric insulation layer for an integrated circuit structure material, and a method of making same, are disclosed. The low dielectric constant insulation layer comprises a porous insulation layer, preferably sandwiched between non-porous upper and lower insulation layers. The presence of some gases such as air or an inert gas, or a vacuum, in the porous insulation material reduces the overall dielectric constant of the insulation material, thereby effectively reducing the capacitance of the structure. The porous insulation layer is formed by a chemical vapor deposition of a mixture of the insulation material and a second extractable material; and then subsequently selectively removing the second extractable material, thereby leaving behind a porous matrix of the insulation material, comprising the low dielectric constant insulation layer.