Effective Relative Dielectric Constant Research Articles

Thermodynamic property of one-dimensional hydrogenic impurity in Nitride semiconductor quantum well

ABSTRACT The thermodynamic properties of one-dimensional (1-D) hydrogenic impurity in Nitride semiconductor quantum well have been investigated. Firstly, using a combination of the linear variational approach and the effective mass approximation, we obtain the eigen-energy of hydrogenic impurity states in AlN, GaN and InN quantum wells. Subsequently, we explore the quantum size effect on the thermodynamic properties of these low-dimensional semiconductor structures, revealing some novel and intriguing phenomena. It is found as the width of the quantum well is increased, the energy of hydrogenic impurity gets decreased, however, the thermodynamic parameters, such as the average energy, entropy and heat capacity of the hydrogenic impurity become increased. The physical origins of these peculiar phenomena are attributed to the competitive mechanism between the quantum confinement effect and Coulombic interaction between the electron and impurity. Finally, by conducting a comprehensive comparison of the thermodynamic parameters among GaN, InN, and AlN quantum wells, we propose an innovative strategy for modulating the thermodynamic properties of these low-dimensional semiconductor structures. This manipulation can be achieved not only through external factors such as temperature and quantum well size, but also by altering internal variables like the effective mass and relative dielectric constant of the semiconductor material. This study not only advances our understanding of the thermodynamic properties of hydrogenic impurities in semiconductor quantum wells, but also provides some theoretical guidance for practical applications in fields such as semiconductor physics, condensed matter physics, chemical physics, etc.

Design, analysis and fabrication of the CPW resonator loaded by DGS and MEMS capacitors

In this paper, an analytical method of resonant frequency, tuning range, the effective relative dielectric constant, and characteristic impedance is proposed, which is for coplanar waveguide (CPW) resonator loaded by defected ground structure (DGS) and micro-electromechanical systems (MEMS) capacitors. The analytical solution is achieved by an employing equivalent method. The resonant frequency, tuning range, and effective relative dielectric constant are obtained by the analytical solution. For verifying the effectiveness of the proposed method, a CPW tunable bandstop filter (BSF) with DGS and MEMS capacitors is designed, simulated, and fabricated, results show good effectiveness of the proposed analysis method. By changing the height of the MEMS beam with the actuation voltage, the designed BSF can switch the center frequency among three states (i.e. 18.5 GHz, 18.2 GHz, 17.5 GHz, respectively), and fractional bandwidth is changed as well (i.e. 37.8%, 45.6%, 49.5%, respectively).

ADVANCED METHOD OF ANTENNA CALCULATION FOR RADIO MONITORING SYSTEMS OF ON-BOARD RADIO SOURCES

Analysis of the experience of modern armed struggle shows that timely detection of signals onboard radio sources by radio monitoring systems is an important task. One way to ensure its solution is the use of compact broadband antennas in the centimeter range. Therefore the development and improvement of methods for calculating broadband compact antennas in the centimeter wave range is an important and relevant scientific and practical task. An improved method for calculating a traveling wave antenna based on irregular symmetrical slit lines located arranged on a multilayer dielectric substrate (Vivaldi antennas) is proposed, by taking into account the thickness of the dielectric substrate, the relative effective dielectric constant of the substrate layers and two-way power supply to improve the directional properties of the antenna and its coordination in a given frequency band. In particular, the formulas of the phase multiplier of the system (for two radiating elements) and the resulting pattern of the antenna take into account the two-way power supply and the thickness and relative dielectric constant of the substrate. These advanced formulas for calculating and selecting these options antennas, lengths; maximum and minimum slot width; the coefficient of opening the gap; the width of the strip of symmetrical microstrip power line at the connection of the coaxial power line; the width of the strip at the intersection with the slit line; the width of the symmetrical slit line at the base of the opening; the length of a quarter-wave transformer based on a symmetrical microstrip line; the length of the symmetric microstrip power line; slit length; resonator diameter; the radius of the cover of the structural capacitor. The practical significance of the results obtained lies in the possibility of an approximate calculation of compact broadband antennas in the centimeter wavelength range. The results make it possible to model and manufacture these antennas for radio monitoring systems for onboard radio sources.

A novel airgap formation scheme by GO nanosheet gap sealing process with extreme low effective dielectric constant

In order to reduce the parasitic capacitance between the interconnect metal line, low-k material was developed and integrated into CMOS BEOL process, and airgap is the ultimate low-k material with the lowest dielectric constant close to 1. In this work, a novel airgap formation scheme was proposed to form the airgap by low-cost coating process, in which Graphene Oxide (GO) nanosheet was used as gap-filling suppressor to seal the gap between two adjacent metal line and form the airgap. Traditional non-conformal CVD gap sealing process was firstly developed and compared with the proposed scheme. It was found that the non-conformal CVD sealing process cannot achieve high performance airgap, and there will always be some material deposited into the gap between the metal interconnect line even for very narrow gap. For the proposed scheme, volume ratio of GO sealed airgap to gap region before sealed can reach to about 85% with much wider gap, and calculated effective relative dielectric constant of this region is about 1.57. When increasing the gap CD to value larger than GO nanosheet size, conformal film deposition can be got, which indicate that GO nanosheet with the size larger than gap CD can seal the gap in the very beginning and prevent further material depositing into the gap to make the large ratio airgap formation.

Towards Accurate Dielectric Property Retrieval of Biological Tissues for Blood Glucose Monitoring

An analytical formulation for relative dielectric con- stant retrieval is reconstructed to establish a relationship between the response of a spiral microstrip resonator and effective relative dielectric constant of a lossy superstrate, such as biological tissue. To do so, an analytical equation is modified by constructing functions for the two unknowns, filling factor A and the effective length leff of the resonator. This is done by simulating the resonator with digital phantoms of varying permittivity .T he values of A and leff are determined for each phantom from the resulting S-parameter response, using Particle Swarm Op- timization. Multiple non-linear regression is applied to produce equations for A and leff, expressed as a function of frequency and the phantom's relative dielectric constant. These equations are combined to form a new non-linear analytical equation, which is then solved using the Newton-Raphson iterative method, for both simulations and measurements of physical phantoms. To verify the reconstructed dielectric constant, the dielectric properties of the physical phantoms are determined with a commercial high temperature open-ended coaxial probe. The dielectric properties are reconstructed by the described method, with less than 3.67% error with respect to the measurements.

Excitation of multi-modes of vibration using tangentially polarized thin walled cylinders

Tangentially polarized thin-walled striped-electroded piezoelectric cylindrical transducers are used in several electromechanical and electroacoustic applications. This study is an extension of the previous work [J. Acoust. Soc. Am. 133, 2661 (2013); J. Acoust. Soc. Am. 132, 3068 (2012)] and involves the study of electromechanical excitation of multi-modes of vibration using tangentially polarized cylinders. A numerical finite difference method (FDM) was used to analysis the nonuniform electric field in the tangentially polarized cylinder under the assumption that the piezoelectric element is fully polarized. The electromechanical properties including the effective electromechanical coupling coefficient, effective piezoelectric modulus, the effective compliance, and effective relative dielectric constant were calculated for a tangentially polarized cylinder for several modes of vibration and compared with results of cylinders using traditional transverse piezoelectric effect.

One method for electric field determination in the vicinity of infinitely thin electrode shells

One numerical method, the so-called equivalent electrodes method (EEM), has been applied to electric field calculation at planar and axially symmetric, extremely thin electrodes. The results obtained for characteristic impedance and effective relative dielectric constant of strip lines are presented, as well as electric field and potential distribution at geometrically modelled cable terminations. The accuracy of results of EEM depends on the number of used equivalent electrodes (EEs) and the error is inversely proportional to the selected number of EES. The method is very simple and exact and in limit process, with the number of the EES, gives exact results. However, in calculations certain problems may appear because of the increase EEs number, especially at very thin electrodes. The electric field being extremely high at the sharp electrode's ends, compared to other parts of the electrode, so it is possible to use smaller and denser EEs. The improvement proposed in this paper enables accurate calculation using a smaller number of EEs. Since the density of equivalent electrodes is higher, equivalent radii are smaller and EEs are not set at the same distances. The number of EEs in other regions is reduced. Some results obtained by the application of EEM have been compared with values obtained using the finite elements method (FEM) and very good matches have been identified.

A class of artificial materials isorefractive with free space

A new class of dispersion-free artificial material that is isorefractive with free space is presented. Materials can be fabricated by composing an array of conducting inclusions in a tenuous host medium that are symmetric with respect to the direction of propagation. Strategies are proposed for both longitudinal and radial propagation. In the presence of the transverse electromagnetic mode, the inclusions are transversely polarized and hence raise the effective relative dielectric constant of the material. The inclusions simultaneously constrict the magnetic field lines, lowering the effective permeability by the same factor. The net effect is to make an artificial material with the same speed of propagation as the host material, but with a lower effective impedance. Such a material can be used to improve aperture efficiency in impulse radiating antennas. Limitations of the materials including field enhancement due to the inclusions and skin losses due to finite conductivities are also discussed.

Comparison of all atom, continuum, and linear fitting empirical models for charge screening effect of aqueous medium surrounding a protein molecule

To investigate the role hydration plays in the electrostatic interactions of proteins, the time-averaged electrostatic potential of the B1 domain of protein G in an aqueous solution was calculated with full atomic molecular dynamics simulations that explicitly considers every atom (i.e., an all atom model). This all atom calculated potential was compared with the potential obtained from an electrostatic continuum model calculation. In both cases, the charge-screening effect was fairly well formulated with an effective relative dielectric constant which increased linearly with increasing charge–charge distance. This simulated linear dependence agrees with the experimentally determined linear relation proposed by Pickersgill. Cut-off approximations for Coulomb interactions failed to reproduce this linear relation. Correlation between the all atom model and the continuum models was found to be better than the respective correlation calculated for linear fitting to the two models. This confirms that the continuum model is better at treating the complicated shapes of protein conformations than the simple linear fitting empirical model. We have tried a sigmoid fitting empirical model in addition to the linear one. When weights of all data were treated equally, the sigmoid model, which requires two fitting parameters, fits results of both the all atom and the continuum models less accurately than the linear model which requires only one fitting parameter. When potential values are chosen as weighting factors, the fitting error of the sigmoid model became smaller, and the slope of both linear fitting curves became smaller. This suggests the screening effect of an aqueous medium within a short range, where potential values are relatively large, is smaller than that expected from the linear fitting curve whose slope is almost 4. To investigate the linear increase of the effective relative dielectric constant, the Poisson equation of a low-dielectric sphere in a high-dielectric medium was solved and charges distributed near the molecular surface were indicated as leading to the apparent linearity.

Structural properties and electrical characteristics of electron-beam gun evaporated erbium oxide films

We report properties of Er2O3 films deposited on silicon using electron-beam gun evaporation. We describe the evolution with thickness and annealing temperature of the morphology, structure, and electrical characteristics. An effective relative dielectric constant in the range of 6–14, a minimum leakage current density of 1–2×10−8 A/cm2 at an electric field of 106 V/cm and breakdown electric field of 0.8–1.7×107 V/cm are demonstrated. Breakdown electric field and leakage current densities are correlated with the surface morphology. The obtained characteristics make the Er2O3 films a promising substitute for SiO2 as an ultrathin gate dielectric.

Single and multilayer ferroelectric PbZr xTi 1− xO 3 (PZT) on BaTiO 3

Ferroelectric PbZr x Ti 1− x O 3 (PZT) thin films have been deposited on Pt-coated Si substrates by using r.f. magnetron sputtering. The optimized processing condition to obtain proper stoichiometric PZT, the desired ferroelectric perovskite phase, and better dielectric properties was demonstrated using a PZT target with Pb/(Zr + Ti) ratio of 1.2 and depositing at 350 °C, followed by thermal treatment at 620 °C for 30 min. The structural and electrical properties of the PZT layer were further improved by fabricating a novel multilayer structure which combined the PZT with the nanolayer BaTiO 3. The leakage current density was reduced from 2 × 10 −7 A cm −2 for the single layer structure to 2 × 10 −9 A cm −2 for the multilayer structure at a field of 4 × 10 5 V cm −1, while maintaining the high relative effective dielectric constant of 442. The relative dielectric constant of the PZT film in the multilayer structure was calculated to be about 880.

Multilayer Lead Zirconate Titanate and Barium Titanate Ferroelectric Capacitors

AbstractFerroelectric PbZrxT1−xO3 (PZT) thin films have been deposited on Pt coated Si substrates by if magnetron sputtering. The optimized processing condition to obtain proper stoichiometric PZT, the desired ferroelectric perovskite phase, and better dielectric properties was demonstrated using a PZT target with Pb(Zr+Ti) ratio of 1.2 and depositing at 350°C, followed by thermal treatment at 620°C for 30 min. The structural and electrical properties of the PZT layer were further improved by fabricating a novel multilayer structure which combined the PZT with the nanolayer BaTiO3. The leakage current density was reduced from 2×10−7 A/cm2 for the single layer structure to 2×10−9 A/cm2 for the multilayer structure at a field of 4×105 V/cm, while maintaining a high relative effective dielectric constant of 442. The relative dielectric constant of the PZT film in the multilayer structure was calculated to be about 880.

Electron Cyclotron Resonance Plasma‐Enhanced Metalorganic Chemical Vapor Deposition of Tantalum Oxide Thin Films on Silicon near Room Temperature

Films of tantalum oxide, ranging in thickness from 25 to 2000 nm, were successfully deposited on silicon by the electron cyclotron resonance plasma‐enhanced metalorganic chemical vapor deposition (ECR‐MOCVD) process at deposition rates of up to 33 nm/min. The films were produced by decomposition of tantalum pentaethoxide into tantalum oxide in an oxygen ECR microwave plasma. The films were amorphous (but fully dense) since the temperature of the substrate, which was unheated, was estimated to be 76–120°C. The growth of the tantalum oxide films was accompanied by the formation of an interlayer of silicon dioxide at the silicon interface. The tantalum oxide films were oxygen rich (relative to Ta2O5). The effective relative dielectric constant of these dual‐layer dielectrics ranged from ɛef= 8.5 to 24; this range was explained in terms of a bilayer consisting of a 13‐nm‐thick silicon dioxide layer of ɛsx= 4, and a tantalum oxide overgrowth of varying thickness having ɛtx∼ 25. A maximum breakdown strength of the films was 6.9 MV/cm and the leakage current at a field of 1 MV/cm was 3.0 × 10‐8. The breakdown properties were related to the presence of stray particles on the substrate; these properties are expected to improve considerably if the processing is carried out in a clean‐room environment. The silicon dioxide layer is believed to have grown by the diffusion of oxygen through the tantalum oxide overlayer despite the low substrate temperature.

Resonant frequency of electrically-thick circular microstrip antennas

Abstract A very simple expression for the effective relative dielectric constant is presented for an electrically-thick circular microstrip antenna. The theoretical resonant frequency results obtained by using this new expression are in good agreement with the experimental results available in the literature. The expression proposed can also be used in the calculation of the resonant frequency of a circular microstrip antenna with an air gap.

Improved Calibration of Time Domain Reflectometry Soil Water Content Measurements

Time domain reflectometry (TDR) is becoming a widely used method to determine volumetric soil water content, θ, from measured effective relative dielectric constant (permittivity), ε, using the empirical θ(ε) Topp-Davis-Annan calibration equation. This equation is not adequate for all soils. The purpose of this study was to compare the Topp calibration equation with a theoretical (Maxwell-De Loor) and an empiricial (fitting exponent α) mixing model for the four components: solid phase (s), tightly bound water (bw), free water, and air. Water content permittivity were measured, gravimetrically and by TDR, on packed columns of 11 soils ranging from loess to pure bentonite. Measured specific surfaces were S = 25 to 665 m2 g−1 and bulk densities ρb = 0.55 to 1.65 g cm−3. Topp yielded accurate ε(θ) values only for the four soils with ρb > 1.30 g cm−3, including illite (S = 147 m2 g−1). Maxwell-De Loor gave similar accuracy for seven soils, including attapulgite (S = 270 m2 g−1, ρb = 0.55 g cm−3), assuming a monomolecular tightly bound water layer (thickness δ = 3 × 10−10 m; θbw = δ ρbS), εbw = 3.2, and εs = 5.0. The ε(θ) curve of these soils had the same shape as Topp. Two gibbsite soils with dissimilar curves required εbw = 3.2 and εs = 16 to 18, and two smectite soil materials required εbw = 30 to 50 and εs = 5.0, to obtain good fits. Deviations from Topp appear generally due more to the lower ρb and thus higher air volume fraction at the same θ associated with fine-textured soils than to tightly bound water with low ε. Both effects, as well as apparent anomalous behavior such as decreasing effective ε with increasing εs, can be accomodated by the Maxwell-De Loor equation. This makes it a better calibration equation than Topp. The empirical α model is sensitive to the unpredictable value of α and cannot accomodate anomalous behavior.

Novel Niobium‐Doped Titania Varistor with Added Barium and Bismuth

Characteristics of the sintered compacts and the microstructures and electrical properties of Nb‐doped TiO2 varistors with added Ba and Bi were studied at various sintering temperatures ranging from 1250° to 1400°C. Adding both Ba and Bi to Nb‐doped TiO2 ceramics resulted in a maximum intergranular phase and a minimum weight loss at 1350°C. In contrast, adding either Ba or Bi alone produced no such maxima and minima. The intergranular phases included mainly a Bi2Ti2O7 crystal phase, apt to occur at a triple junction, and a Ba‐rich amorphous phase that surrounded the grains, but discontinuously. The intergranular phases varied consistently with variation in electrical properties. The optimum conditions for the most efficient boundary barrier layer, with the lowest weight loss and the highest resistivity at low frequencies, were 1350°C with both Ba and Bi addition. The highest values for α (∼9.5), Vgb10 (∼0.8 V), and EB (∼0.42 e V) support that finding. The effective relative dielectric constant, Keff∼ 20 000, also was obtained under optimum conditions. The single addition of either Ba or Bi, however, produced nearly the opposite results, as discussed in this paper.

18-42 GHz experimental verification of microstrip coupler and open end capacitance models

A cavity resonance technique is used to experimentally verify microstrip coupler and open end capacitance models over the frequency range of 18-42 GHz. In addition, these results are confirmed using an alternate version of the technique which directly determines open end discontinuity capacitance. In the second case, knowledge of substrate dielectric constant is not required, and the method also yields the microstrip relative effective dielectric constant. >

Tests of microstrip dispersion formulas

A set of published formulas for the frequency dependence of the microstrip effective relative dielectric constant epsilon /sub re/(f) is tested relative to an assemblage of measured data values for this quantity chosen from the literature. The RMS deviation of the predicted data obtained from the measured values ranged from 2.3% to 4.1% of the seven formulas for epsilon /sub re/(f) tested. A formula due to M. Kirschning and R.H. Jansen (see Electron. Lett., vol.18, p.272-73, 1982) showed the lowest average deviation from measured values, although the differences between the predictions of their formula and others tested are of the order of the error limits of the comparison process. It is concluded that the results indicate the suitability of relatively simple analytical expressions for the computation for microstrip dispersion. >

Theoretical and Experimental Investigation of Asymmetric Coplanar Waveguides (Short Papers)

Conformal mapping techniques are used to obtain analytic closed-form expressions for the characteristic impedance and the relative effective dielectric constant of asymmetric coplanar waveguide with infinite or finite dielectric thickness. The line asymmetry leads to a decrease of its characteristic impedance and to an increase of its relative effective dielectric constant. Six asymmetric coplanar waveguides are realized and their characteristic impedances are measured using time-domain reflectometry techniques. The experimental results show very good agreement with the theoretical ones.

Theoretical and experimental TWT helix loss determination

As efficiency and power requirements for broad-band traveling-wave tubes (TWT) increase, the necessity to reduce losses becomes more and more important. It is particularly important to reduce circuit losses because, when efficient multistage depressed collectors are used, each 2-percent increase in circuit efficiency yields a 1-percent increase in overall efficiency! Attempts to predict losses in helix structures have produced answers that were a factor of at least three below the measured loss. Historically, loss measurements have been very difficult to make, primarily, because of the small values of the quantities being measured. This paper presents an accurate theoretical analysis of the loss of a helix structure. The effect on loss of the dielectric support rods for the helix is taken into account. In addition, helix losses are separated from barrel losses. Functional variations are given of loss with frequency, helix pitch, helix radius, barrel-to-helix diameter ratio, helix and barrel resistivity, and the effective relative dielectric constant of the helix support rods. Measurements of loss, made with a Hewlett-Packard automatic network analyzer and a new automated measurement procedure, are presented. It is shown that excellent agreement between the predicted loss and the measured loss is obtained when helix surface roughness effects on resistivity are taken into account. Also, a correction is made for the increase in measured loss resulting from impedance mismatches between the helix and the measurement circuit and from loss in the sliding short.