Showing papers on "Dielectric published in 1988"

Industrial Microwave Heating

Abstract: This book offers a broad coverage of the theory and practice of industrial microwave heating.

The discrete-dipole approximation and its application to interstellar graphite grains

Abstract: The discrete dipole approximation (DDA), a flexible method for computing scattering of radiation by particles of arbitrary shape, is extended to incorporate the effects of radiative reaction and to allow for possible anisotropy of the dielectric tensor of the material. Formulas are given for the evaluation of extinction, absorption, scattering, and polarization cross sections. A simple numerical algorithm based on the method of conjugate gradients is found to provide an efficient and robust method for obtaining accurate solutions to the scattering problem. The method works well for absorptive, as well as dielectric, grain materials. Two validity criteria for the DDA are presented. The DDA is then used to compute extinction cross sections for spherical graphite grains and to calculate extinction cross sections for nonspherical graphite grains with three different geometries. It is concluded that the interstellar 2175 A extinction feature could be produced by small graphite grains which should have aspect ratios not far from unity. 35 references.

1/f noise and other slow, nonexponential kinetics in condensed matter.

Abstract: Fluctuations in resistivity with an approximately $\frac{1}{f}$ spectrum are found in most conducting materials. Some of the detailed mechanisms, which turn out to be quite diverse, are explored in this review. Several new techniques are explained. Various theories are critically examined. Some connections with other widespread phenomena, such as highly nonexponential dielectric relaxations, are briefly investigated.

High‐resolution capacitance measurement and potentiometry by force microscopy

Abstract: We demonstrate the usefulness and high sensitivity of the atomic force microscope (AFM) for imaging surface dielectric properties and for potentiometry through the detection of electrostatic forces Electric forces as small as 10−10 N have been measured, corresponding to a capacitance of 10−19 farad The sensitivity of our AFM should ultimately allow us to detect capacitances as low as 8×10−22 F The method enables us to detect the presence of dielectric material over Si, and to measure the voltage in a p‐n junction with submicron spatial resolution

Preparation of Pb(Zr,Ti)O3 thin films by sol gel processing: Electrical, optical, and electro‐optic properties

Abstract: Crack‐free transparent ferroelectric polycrystalline Pb(Zr,Ti)O3 thin films were prepared by spin‐coating solutions of complex alkoxides. The preparation of stock solution, firing, and annealing of films was described. The coating of the intermediate layer of Al2O3 increased the adhesion between Pb(Zr,Ti)O3 thin films and glass substrates. The crystalline phases of films with varying Zr/Ti ratios were investigated. The dielectric constants were about 260. The remanent polarization and coercive field were 6.6 μC/cm2 and 26.7 kV/cm, respectively. The refractive index of the perovskite Pb(Zr,Ti)O3 films was 2.6 at 6328 A, and the absorption edge was at 3400 A. The quadratic and linear electro‐optic effects were measured with respect to the Zr/Ti ratio from 40/60 to 60/40 for films grown on glass substrates. The quadratic and linear electro‐optic coefficients were about 1×10−18 m2 /V2 and 2.4×10−11 m/V at 6328 A, respectively.

Effective permittivity of dielectric mixtures

Abstract: General mixing formulas are derived for discrete scatterers immersed in a host medium. The inclusion particles are assumed to be ellipsoidal. The electric field inside the scatterers is determined by quasi-static analysis, assuming the diameter of the inclusion particles to be much smaller than one wavelength. The results are applicable to general multiphase mixtures, and the scattering ellipsoids of the different phases can have different sizes and arbitrary ellipticity distribution and axis orientation, i.e. the mixture may be isotropic or anisotropic. The resulting mixing formula is nonlinear and is suitable for iterative solutions. The formula contains a quantity called the apparent permittivity, and with different choices of this quantity, the result leads to the generalized Lorentz-Lorenz formula, the generalized Polder-van Santen formula, and the generalized coherent potential-quasicrystalline approximation formula. The results are applied to calculating the complex effective permittivity of dry and wet snow, and sea ice. >

Dielectric resonators

Abstract: Microwave passive and active devices containing dielectric resonators and the design procedures used to characterize these components are reviewed. The emphasis has been on low noise, small size, low cost and high temperature stability. Both filter and oscillator applications are described. The applications of dielectric resonators in the millimeter-wave frequency band are also discussed. >

Electrophotography and Development Physics

Abstract: 1. Introduction.- 1.1 Technical History.- 1.2 Copier Market.- 1.3 Printer Market.- 1.4 Alternative Powder Marking Technologies.- 1.4.1 Magnetography.- 1.4.2 Ionography.- 2. The Electrophotographic Process.- 2.1 The Six Steps of Electrophotography.- 2.1.1 Charge.- 2.1.2 Expose.- 2.1.3 Develop.- 2.1.4 Transfer.- 2.1.5 Fuse.- 2.1.6 Clean.- 2.2 Implementation-Interactions.- 2.3 Subsystem Choices.- 2.3.1 Photoreceptor.- 2.3.2 Charge.- 2.3.3 Light Source.- 2.3.4 Develop.- 2.3.5 Transfer.- 2.3.6 Fuse.- 2.3.7 Clean.- 3. The Development Step.- 3.1 Challenges.- 3.2 Focus.- 3.3 Descriptions.- 4. Toner Charging for Two Component Development Systems.- 4.1 Metal-Metal Contact Charging.- 4.2 Metal-Insulator Contact Charging.- 4.2.1 Controversies.- 4.2.2 Experimental and Theoretical Difficulties.- 4.2.3 Other Metal-Insulator Experiments.- 4.2.4 Electron Transfer Theories.- 4.2.5 Ion Transfer Theories.- 4.3 Insulator-Insulator Contact Charging.- 4.4 Toner-Carrier Charging.- 4.4.1 Surface State Theory.- 4.4.2 Carbon Black.- 4.4.3 Charge Control Agents.- 4.4.4 Charge Measuring Tools.- 4.5 Summary.- 5. Cascade Development.- 5.1 Development Mechanisms.- 5.1.1 Airborne.- 5.1.2 Contact.- 5.1.3 Scavenging.- 5.1.4 Electrode Source.- 5.2 Experimental Work.- 5.2.1 Solid Area Development.- 5.2.2 Line Development.- 5.2.3 Background Development.- 5.3 Theory Ill.- 5.3.1 Airborne Development Ill.- 5.3.2 Contact Development.- 5.4 Summary.- 6. Insulative Magnetic Brush Development.- 6.1 Qualitative Comparison of Development Mechanisms.- 6.2 The Electric Field.- 6.2.1 Charges.- 6.2.2 Effective Dielectric Constant.- 6.3 Theories of Solid Area Development.- 6.3.1 Neutralization.- 6.3.2 Field Stripping.- 6.3.3 Powder Cloud.- 6.3.4 Equilibrium.- 6.3.5 Depletion.- 6.3.6 "Complete" Theory.- 6.4 Solid Area Development Experiments.- 6.5 Line Development.- 6.6 Background Development.- 6.7 Improvements.- 6.8 Summary.- 7. Conductive Magnetic Brush Development.- 7.1 Initial Theoretical Ideas.- 7.2 Experimental Data and Discussions.- 7.3 Infinitely Conductive Theory.- 7.4 Comparison with Experiment.- 7.5 Line Development.- 7.6 Background Development.- 7.7 Summary.- 8. Toner Charging for Monocomponent Development Systems.- 8.1 Induction Charging.- 8.2 Injection Charging.- 8.3 Contact Charging.- 8.4 Corona Charging.- 8.5 Charging Methods for Powder Coating.- 8.6 Other Charging Methods.- 8.7 Traveling Electric Fields.- 9. Monocomponent Development.- 9.1 Aerosol or Powder Cloud Development.- 9.2 Early Work.- 9.3 Theory of Monocomponent Development.- 9.4 Conductive Toner.- 9.5 Magnetic, Insulative Toner.- 9.6 Nonmagnetic, Insulative Toner.- 9.7 Summary.- 10. Liquid Development.- 10.1 Material Requirements.- 10.1.1 Toner Charging.- 10.1.2 Liquid Properties.- 10.2 Development Theories.- 10.2.1 First-Order Effects.- 10.2.2 Complexities.- 10.2.3 Better Development Theories.- 10.3 Toner Characteristics.- 10.3.1 Optimized Properties.- 10.3.2 Determination of Toner Properties.- 10.4 Recent Developments.- 10.5 Summary.- 11. Color Electrophotography.- 11.1 History.- 11.2 Image Quality.- 11.2.1 Grayscale.- 11.2.2 Other Challenges.- 11.3 Colored Toner Accumulation.- 11.4 New Development Systems.- 11.4.1 Image Quality.- 11.4.2 Compactness.- 11.4.3 Noncontact, Noninteracting Development System.- 11.5 Color Market.- 11.6 Current Copier Products.- 11.7 Current Printer Products.- 12. Update of Chapters 1-10.- 12-1.2 Copier Market.- 12-1.3 Printer Market.- 12-1.4 Alternative Powder Marking Technologies.- 12-1.4.1 Magnetography.- 12-1.4.2 Ionography.- 12-2.1.4 Transfer and Toner Adhesion.- 12-2.3.2 Charge.- 12-2.3.5 Transfer.- 12-2.3.7 Clean.- 12-4 Toner Charging for Two Component Development Systems.- 12-4.3 Insulator-Insulator Contact Charging.- 12-4.4 Toner-Carrier Charging.- 12-4.4.1 Surface State Theory.- 12-4.4.3 Charge Control Agents.- 12-4.4.4 Charge Measuring Tools.- 12-4.4.5 Life Characteristics.- 12-6.2.2 Effective Dielectric Constant.- 12-6.4 Solid Area Development Experiments.- 12-6.6 Background Development.- 12-7.3 Infinitely Conductive Theory.- 12-8.3 Contact Charging.- 12-9.3 Theory of Monocomponent Development.- 12-9.4 Conductive Toner.- 12-9.6 Nonmagnetic, Insulative Toner.- 12-10.1.1 Toner Charging.- 12-10.4 Recent Developments.- References.

Nonequilibrium theory of the optical Stark effect and spectral hole burning in semiconductors.

Abstract: We consider the influence of intense coherent laser fields on the electronic and optical properties of semiconductors. Using nonequilibrium Green's-function techniques and exploiting the analogies to superconducting and Bose-condensed systems, we discuss the nature of the renormalizations and the collective excitations in the collisionless regime. Experimentally, this situation can be realized (i) under nonresonant excitation of virtual electron-hole pairs and (ii) under resonant excitation with ultrashort pulses. We explain the recently observed optical Stark effect as well as spectral hole burning and derive from first principles the longitudinal and transverse dielectric functions including exciton correlations.

Low‐loss substrate for epitaxial growth of high‐temperature superconductor thin films

Abstract: A perovskite‐like single‐crystal substrate material has been investigated that simultaneously permits epitaxial growth of 1‐2‐3 superconductor films and possesses desirable rf properties of low dielectric constant and loss tangent. The lattice constant of 3.792 A provides a lattice match to within 1% of the a axis of 1‐2‐3. Sputtered films of erbium‐barium‐copper‐oxide have been produced on (100) LaAlO3 substrates that exhibit sharp resistive transitions at 90 K (ΔT=1K), bulk superconductivity as determined by ac susceptibility measurements, and nearly single‐crystal growth as evidenced by x‐ray diffraction and high‐resolution scanning electron microscopy. The high‐frequency dielectric properties of LaAlO3 were experimentally investigated at several temperatures. The low‐frequency dielectric constant was measured to be 15 and the microwave loss tangent ranged from 6×10−4 at room temperature to 5×10−6 at 4 K.

Electromagnetic scattering from a layer of finite length, randomly oriented, dielectric, circular cylinders over a rough interface with application to vegetation

Abstract: A scattering model for defoliated vegetation is developed by treating a layer of defoliated vegetation as a collection of randomly oriented dielectric cylinders of finite length over an irregular ground surface. Both polarized and depolarized backscattering are computed and their behavior versus the volume fraction, the incidence angle, the frequency, the angular distribution and the cylinder size are illustrated. It is found that both the angular distribution and the cylinder size have significant effects on the backscattered signal. The present theory is compared with measurements from defoliated vegetations.

Optimized capacitive sensor for chemical analysis and measurement

Abstract: An apparatus for detecting the presence and/or measuring the concentration of an analyte (24) in the fluid medium (22) is disclosed. The apparatus relies on biospecific binding between a biochemical binding system (20) and the analyte (24) to change the dielectric properties of a capacitive affinity sensor. The biological affinity sensor is optimized by: adjusting the thickness and dielectric properties of a passivation layer (16) to generally match the impedance of the biological binding system (20, 21); and minimize the double layer capacitance so that bulk capacitance changes associated with the biological binding system (20, 21) are maximized.

Dielectric friction and the transition from adiabatic to nonadiabatic electron transfer. I. Solvation dynamics in Liouville space

Abstract: A microscopic theory for electron transfer rates in a polar medium, which interpolates continuously from the adiabatic to the nonadiabatic limits, is developed. Both static (polarity) interactions, which affect the reaction energetics and dynamic (friction) effects, are incorporated using a macroscopic solvation coordinate, whose dynamics and statistical properties are related to the entire frequency and wave vector dependent dielectric function of the solvent e(k,ω). The present approach is based on using an expansion of the density matrix in Liouville space and utilizing the analogy with the calculation of nonlinear optical line shapes. A new criterion for adiabaticity is derived, and the role of the solvent longitudinal dielectric relaxation in inducing the crossover from the nonadiabatic to the adiabatic regimes is clarified. The applicability of a Landau–Zener‐type resumation for the rate is critically analyzed. The origin of the fractional power dependence of the rate on the solvent time scale, observed in several electron transfer and isomerization reactions, is discussed.

Determination of electrical conductivity using time domain reflectometry: Soil and water experiments in coaxial lines

Abstract: The simultaneous measurement of water content and electrical conductivity of soils and KCl solutions was achieved using time domain reflectometry (TDR). Coaxial transmission lines varying in length from 90 to 300 mm contained either KCl solutions or soil of varied water and salt content. The water content of soil or dielectric constant of the water solutions was determined from the travel time. The measured dielectric constant of KCl solutions was unchanged from that of pure water (81) at those concentrations where there was sufficient reflected signal for measurement. Two analyses were used for determination of electrical conductivity, one based on signal attenuation after one “round-trip” and the second based on a thin sample approximation for the signal reflection and attenuation. Reference measurements of conductivity were made on the same samples using low-frequency conductance bridge measurements. These analyses of the TDR traces showed that for water solution both the thin sample analysis and the analysis after a signal had traversed one round-trip yielded conductivity in agreement with bridge conductivity values. This indicated that the imaginary part of the complex dielectric constant was negligible. For soils the thin sample analysis was in general agreement with the bridge measurements. From the analysis of signal after one round-trip in soils there was indication that the imaginary part of the dielectric constant should not be assumed negligible. Further investigation of the frequency dependence of the dielectric constant and attenuation will be required to identify the relative contributions of the real and imaginary parts of the dielectric constant to measurement by TDR. The effect of impedance-matching transformers on conductivity measurements in the field has yet to be ascertained.

Microstrip transmission line excitation of dielectric resonator antennas

Abstract: A systematic investigation of the excitation of a cylindrical dielectric resonator antenna was undertaken to illustrate the possibility of such a feed structure and to characterise the coupling behaviour and radiation patterns of the system.

Domain wall excitations and their contributions to the weak‐signal response of doped lead zirconate titanate ceramics

Abstract: The ac field dependence of the polarization and strain responses of three different compositions of doped lead zirconate titanate ceramics were measured for samples in both the poled and the depoled states. The results indicate that a reversible domain wall excitation exists which contributes to the weak‐signal response of these materials. Irreversible domain wall motion can be excited within the frequency range measured by applying a field above a threshold field, which is much smaller than the coercive field. Therefore, the weak‐signal linear dielectric, piezoelectric, and elastic coefficients of these materials may not provide a suitable description of their behavior when the external applied field exceeds this threshold field. All the observed phenomena can be explained by thermally activated domain wall fluctuations and nucleations.

High performance interconnect system for an integrated circuit

Abstract: A semiconductor integrated circuit device includes a high performance interconnect structure which comprises a plurality of interconnects, with each interconnect being structurally separated from the remaining interconnects except at electrical contact points. In one embodiment, each interconnect is substantially surrounded by a layer of dielectric material, there being gaps between each adjacent layer of surrounding dielectric material. Another embodiment, a layer of electrically conductive material is formed over the surrounding dielectric layer preferably filling in the gaps between adjacent layers of surrounding dielectric material. The layer of electrically conductive material acts as a ground plane and heat sink.

Radiation and lifetimes of atoms inside dielectric particles.

Abstract: The transition rates of atoms inside spherical dielectric particles are computed and studied as functions of the transition frequency and of the physical properties of the host particle. The rates are found to range from about 0.2 to more than 1500 times the free-space value, depending on the location of the atom and other relevant physical parameters. The radiation from distributions of atoms inside liquid drops is also studied. Analytic and numerical results are given for the case of a uniform distribution of excited atoms. Large enhancements of the power output (some 100 times the value for the same distribution in bulk material) are found to occur under resonant conditions.

On the molecular theory of aqueous electrolyte solutions. I. The solution of the RHNC approximation for models at finite concentration

Abstract: This paper describes a theoretical study of the thermodynamic, dielectric, and structural properties of model aqueous electrolyte solutions. The model considered consists of hard sphere ions immersed in a hard polarizable dipole tetrahedral–quadrupole solvent with water‐like parameters. The calculations involve the solution of the reference hypernetted‐chain (RHNC) approximation for ion–solvent mixtures at finite concentration and some details of the general method are discussed. The influence of the molecular polarizability of the solvent particles is treated at the self‐consistent mean field (SCMF) level and, surprisingly, the mean dipole moment of the solvent is found to be nearly independent of the salt concentration. Numerical results are reported for model alkali halide solutions and other 1:1 electrolytes, and comparisons are made with experimental results at 25 °C. The agreement obtained between theory and experiment is variable depending upon the particular property and solution considered. In ad...

Lanthanum gallate substrates for epitaxial high-temperature superconducting thin films

Abstract: We demonstrate that lanthanum gallate (LaGaO3) has considerable potential as an electronic substrate material for high‐temperature superconducting films. It provides a good lattice and thermal expansion match to YBa2Cu3O7−x, can be grown in large crystal sizes, is compatible with high‐temperature film processing, and has a reasonably low dielectric constant (e≂25) and low dielectric losses. Epitaxial YBa2Cu3O7−x films grown on LaGaO3 single‐crystal substrates by three techniques have zero resistance between 87 and 91 K.

The rigorous computation of the molecular electric potential

Abstract: A method is presented for the rigorous computation of the electric potential of molecules of arbitrary shape, under the assumption of continuous linear dielectric media. The computational technique involves finding the distribution of induced polarization charge on the molecular surface, and proceeds by an application of the method of boundary elements. The surface, which separates the molecular interior (of low dielectric constant) from the highly polar solvent, is given a piece-wise analytic representation as a collection of curvilinear elements. Given a set of internal fixed charges, the distribution of polarization-charge is found as a continuous function over the surface elements, and the electric potential (including all polarization effects) is then easily computed at any point. The method is applied to a spherical interface, and to several small molecules of biological interest, including a hexapeptide. The resulting potentials show good convergence in all cases. The future application of the method to macromolecules is discussed.

Characterization of Pb(Zr,Ti)O3 thin films deposited from multielement metal targets

Abstract: Lead zirconate titanate [Pb(Zr,Ti)O3 or PZT] thin films have been grown by sputtering a multi‐element metal target in oxygen using dc planar magnetron sputtering. Growth parameters and annealing conditions have been optimized. The kinetics of reactive sputtering and the implications of sputtering parameters on film composition have been studied. The studies reveal the requirement for operation at low substrate temperatures (200 °C), high sputtering pressures (4–5 Pa), and a large substrate‐to‐target distance (10 cm) for obtaining good control over composition. The structural and electrical properties of films were found to depend on the compositional ratio of Zr/Ti, similar to that observed in bulk PZT ceramics. Films having a resistivity of 1010 Ω cm and a dielectric constant e’∼820 at room temperature (300 K) have been achieved. Ferroelectric hysteresis loop measurements indicated a remanent polarization of 30.0 μC/cm2 and coercive field of 25 kV/cm for the rhombohedral phase composition (Zr/Ti=58/42). ...

Surface stabilized ferroelectric liquid crystal devices

Abstract: A liquid crystal device including a ferroelectric liquid crystal disposed between plates treated to enforce a particular ferroelectric molecular orientation to the plates. The devices employ alone or in combination non-planar boundary conditions, polar boundary conditions, boundaries with multiple physical states, intrinsic spontaneous splay distortion of the polarization orientation field, combined ferroelectric and dielectric torques, layers tilted with respect to the plates. The plates are spaced by a distance sufficiently small to ensure unwinding of the helix typical in a bulk of the material to form either monostable, bistable or multistable states which exhibit novel electro-optic properties. The liquid crystal is responsive to an externally applied electric field, temperature or the like to make a light valve or other electro-optical device.

Attenuation measurement of very low loss dielectric waveguides by the cavity resonator method applicable in the millimeter/submillimeter wavelength range

Abstract: A dielectric waveguide shorted at both ends was constructed as a cavity resonator. By measuring the Q of this cavity, one can determine the attenuation constant of this guided mode on this dielectric structure. The complex permittivity of the dielectric waveguide material can also be derived from the measurements. Measurements were made at Ka-band for dielectric waveguides constructed of nonpolar, low-loss polymers, such as Teflon, polypropylene, polyethylene, polystyrene, and rexolite. >

Planar dual polarization antenna

Abstract: A microwave-frequency microstrip antenna (10) simultaneously usable for both transmitting and receiving microwave-frequency signals that have dual orthogonally polarized components. The components may be either linearly or circularly polarized. A radiating patch (26) is mounted on a first dielectric (12). A ground plane (20) abuts the first dielectric (12) and has two elongated coupling apertures (32,31) at right angles to each other. A second dielectric (22) abuts the ground plane (20) and has embedded thereon two substantially identical conductive planar feed networks (52,51) that are disposed at right angles to each other. At least one additional optional dielectric layer (16,18) having a conductive patch (36,34) may be interposed between the first dielectric (12) and the ground plane (20) for purposes of broadening the bandwidth of the antenna (10). A meanderline polarizer (45) or a 3 dB 90° hybrid coupler (40) may be used for converting from linear polarization to circular polarization.

Dielectric or magnetic medium loaded antenna

Abstract: A loaded antenna (11) comprises a wave source (12) of an arbitrary polarized wave, a reflector (13) disposed near the wave source (12), with the surface opposite to the wave source (12) limited in area, and a dielectric (14) disposed on the opposite side of the reflector across the wave source (12), at least with the surface opposite to the reflector (13) formed parallel to the reflector (13). By properly selecting the mutual interval among the dielectric (14), wave source (12) and reflector(13), the dimension and the dielectric constant of the dielectric (14), the vibration component in the running direction of the wave within the dielectric (14), the vibration component in the direction vertical to the running direction, and the vibration component between the reflector and dielectric are superposed, so that the electromagnetic field distribution in the vicinity of the dielectric (14) is made uniform. Thereby, high gain and high efficiency are realized, and the structure may be notably reduced in size.

Review of literature on aging of dielectrics

Abstract: This paper is a review of dielectric aging and a discussion of the possible mechanisms that may be responsible for the time dependent decrease in complex dielectric constant. The discussion is divided into three material systems: barium titanate, PZT and relaxors. Aging is considered as it affects the real portion of the dielectric constant, tanδ and P-E hysteresis loops.

Dielectric resonator apparatus

Abstract: The dielectric resonator apparatus is characterized in that electric walls exist on one plane or two including the central axis of the electromagnetic field distribution in the using mode of a dielectric resonator, a dielectric resonator with either of dielectrics between the electric wall being removed in shape is provided by plurality, an equivalent axis is common to the central axis of each of the dielectric resonators, with the dielectric resonators being inductively coupled in the axial direction. A dielectric resonator which prevents the current from being concentrated on the central axis of the electromagnetic field distribution, is collectively smaller in the Joule loss and is higher in Q. The dielectric resonator of the present invention is characterized in that the dielectric close to the central axis is removed, wherein electric walls exist on one plane or two including the central axis of the electromagnetic field distribution in a dielectric resonator using, for instance, a TE01δ mode, with either of dielectrics between the electric wall being removed in shape.