Effective Relative Permittivity Research Articles

Dielectric study of low-cost porous anodic aluminum oxide (AAO) template and AAO template-copper nanowires (Cu/AAO) nanocomposites as a capacitor for energy storage

In this work, we explore the effect of increasing electrodeposition time on the dielectric properties of Cu/AAO nanocomposites. Cu nanowires are electrodeposited within the AAO template pores fabricated using a two-step anodization process. The morphology, composition, and crystalline structure are characterized using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). The dielectric properties, including the real part and the imaginary part of the effective complex relative permittivity and the effective AC conductivity of the AAO template and Cu/AAO nanocomposites, are subsequently analyzed. The results demonstrate a clear improvement in effective permittivity and effective AC conductivity of Cu/AAO nanocomposites with increasing electrodeposition time, indicating the potential for tailoring the dielectric properties of AAO templates through the incorporation of metal nanowires for advanced capacitor applications.

Gas‐Phase Anion Photoelectron Spectroscopy of Alkanethiolate‐Protected PtAu12 Superatoms: Charging Energy in Vacuum vs Solution

AbstractThe charging behavior of molecular Au clusters protected by alkanethiolate (SCnH2n+1=SCn) is, under electrochemical conditions, significantly affected by the penetration of solvents and electrolytes into the SCn layer. In this study, we estimated the charging energy EC(n) associated with [PtAu24(SCn)18]−+e−→[PtAu24(SCn)18]2− (n=4, 8, 12, and 16) in vacuum using mass‐selected gas‐phase anion photoelectron spectroscopy of [PtAu24(SCn)18]z (z=−1 and −2). The EC(n) values of PtAu24(SCn)18 in vacuum are significantly larger than those in solution and decrease with n in contrast to the behavior reported for Au25(SCn)18 in solution. The effective relative permittivity (ϵm*) of the SCn layer in vacuum is estimated to be 2.3–2.0 based on the double‐concentric‐capacitor model. Much smaller ϵm* values in vacuum than those in solution are explained by the absence of solvent/electrolyte penetration into the monolayer. The gradual decrease of ϵm* with n is ascribed to the appearance of an exposed surface region due to the bundle formation of long alkyl chains.

Gas-Phase Anion Photoelectron Spectroscopy of Alkanethiolate-Protected PtAu12 Superatoms: Charging Energy in Vacuum vs Solution.

The charging behavior of molecular Au clusters protected by alkanethiolate (SCnH2n+1=SCn) is, under electrochemical conditions, significantly affected by the penetration of solvents and electrolytes into the SCn layer. In this study, we estimated the charging energy EC(n) associated with [PtAu24(SCn)18]-+e-→[PtAu24(SCn)18]2- (n=4, 8, 12, and 16) in vacuum using mass-selected gas-phase anion photoelectron spectroscopy of [PtAu24(SCn)18]z (z=-1 and -2). The EC(n) values of PtAu24(SCn)18 in vacuum are significantly larger than those in solution and decrease with n in contrast to the behavior reported for Au25(SCn)18 in solution. The effective relative permittivity (ϵm*) of the SCn layer in vacuum is estimated to be 2.3-2.0 based on the double-concentric-capacitor model. Much smaller ϵm* values in vacuum than those in solution are explained by the absence of solvent/electrolyte penetration into the monolayer. The gradual decrease of ϵm* with n is ascribed to the appearance of an exposed surface region due to the bundle formation of long alkyl chains.

An Improved Method to Compute the Mutual Capacitance between Interdigital Transducers in Radio Frequency Surface Acoustic Wave Filters

This paper proposes an improved method to calculate the mutual capacitance between interdigital transducer (IDT) electrodes to enhance the accuracy of the traditional coupling-of-modes (COM) model, which is commonly used to simulate surface acoustic wave (SAW) filters and duplexers. In this method, the boundary element method (BEM) is adopted to obtain the capacitance per unit length in a layered medium, while the partial capacitance (PC) method is used to derive the effective relative permittivity of the multi-layered IDT. Numerical results from commercially available software are provided for comparison with the results calculated using the proposed method. The consistent results verify the validity and accuracy of this method, which also demonstrates significantly faster calculation speed compared to commercially available software. Precise electrical response prediction of a dual-mode SAW (DMS) filter can be achieved by applying this method to the COM model, and this ultra-fast calculation method can also be included in filter design optimization.

An Investigation of the Relationship between Effective Relative Permittivity and Infill Density in a 3D Printed Slab

An Investigation of the Relationship between Effective Relative Permittivity and Infill Density in a 3D Printed Slab

Measuring dielectric and electro-optic responses of thin films using plasmonic devices.

This paper introduces a simple method for the measurement of the relative permittivity and the Pockels coefficient of electro-optic (EO) materials in a waveguide up to sub-THz frequencies. By miniaturizing the device and making use of plasmonics, the complexities of traditional methods are mitigated. This work elaborates the fabrication tolerance and simplicity of the method, and highlights its applicability to various materials, substrates and configurations. The method is showcased using drop-casted perovskite barium titanate (BaTiO3, BTO) nano-particle thin-films and it has previously been used to measure epitaxial thin film BTO. In this work we show the effective relative permittivity of drop casted BTO to be εeff ∼ 30 at 200 MHz, dropping to ∼ 18 at 67 GHz and similarly, the effective Pockels coefficient was found to be reff ∼ 16 at 350 MHz and ∼ 8 at 70 GHz. These values are a factor > 50 below the values found for thin film BTO. Yet, the fact that the method can be applied to such different samples and Pockels strengths gives testimony to its versatility and sensitivity.

Wearable Capacitive Tactile Sensor Based on Porous Dielectric Composite of Polyurethane and Silver Nanowire.

In recent years, the implementation of wearable and biocompatible tactile sensing elements with sufficient response into healthcare, medical detection, and electronic skin/amputee prosthetics has been an intriguing but challenging quest. Here, we propose a flexible all-polyurethane capacitive tactile sensor that utilizes a salt crystal-templated porous elastomeric framework filling with silver nanowire as the composite dielectric material, sandwiched by a set of polyurethane films covering silver nanowire networks as electrodes. With the aids of these cubic air pores and conducting nanowires, the fabricated capacitive tactile sensor provides pronounced enhancement of both sensor compressibility and effective relative dielectric permittivity across a broad pressure regime (from a few Pa to tens of thousands of Pa). The fabricated silver nanowire-porous polyurethane sensor presents a sensitivity improvement of up to 4-60 times as compared to a flat polyurethane device. An ultrasmall external stimulus as light as 3 mg, equivalent to an applied pressure of ∼0.3 Pa, can also be clearly recognized. Our all-polyurethane capacitive tactile sensor based on a porous dielectric framework hybrid with conducting nanowire reveals versatile potential applications in physiological activity detection, arterial pulse monitoring, and spatial pressure distribution, paving the way for wearable electronics and artificial skin.

Modified Babinet Principle for Complementary Antennas in a Dielectric Half-Space

In this letter, the modified Babinet principle is applied to complementary antennas on the substrate interface. First, it is verified that the existing Babinet principle only holds for complementary metallic elements in the homogenized substrate. Then, the effective relative permittivity is introduced into the substrate interface through the zero-thickness effective substrate, which can keep the electromagnetic behavior (such as total electrical field and surface current density) of metallic element unchanged. Thereby, the modified Babinet principle can be established for arbitrary complementary metallic elements on the substrate interface. Finally, the proposed theory is applied to input impedances of complementary antennas on the substrate interface. The simulation strongly supports the proposed theory, regardless of the substrates and antenna sizes. The study not only establishes the modified Babinet principle for complementary metallic elements on the substrate interface, but also clarifies the electromagnetic influence of effective relative permittivity for the metallic element at the substrate interface.

Application of Localized Surface Plasmon Resonance of Conjugated Gold Nanoparticles in Spectral Diagnosis of SARS-CoV-2: A Numerical Study.

Severe respiratory syndrome COVID-19 (SARS-CoV-2) outbreak has became the most important global health issue, and simultaneous efforts to fast and low-cost diagnosis of this virus were performed by researchers. One of the most usual tests was colorimetric methods based on the change of color of gold nanoparticles in the presence of viral antibodies, antigens, and other biological agents. This spectral change can be due to the aggregation of the particles or the shift of localized surface plasmon resonance due to the electrical interactions of surface agents. It is known that surface agents could easily shift the absorption peak of metallic nanocolloids which is attributed to the localized surface plasmon resonance. Experimental diagnosis assays for colorimetric detection of SARS-CoV-2 using Au NPs were reviewed, and the shift of absorption peak was studied from the viewpoint of numerical analysis. Using the numerical method, the refractive index and real and imaginary parts of the effective relative permittivity of the viral biological shell around Au NPs were obtained. This model gives a quantitative description of colorimetric assays of the detection of SARS-CoV-2 using Au NPs.

High-Performance Polyimide Aerogel Film-Based Triboelectric Nanogenerator for Trace Liquid Analyzing

Aerogels exhibit excellent sensing performance thanks to their high porosity, large specific surface area, and remarkable mechanical property. However, the prevalent aerogel-based analyzers fail to detect liquid in a way of low detection limit, fast response, and good robustness. Here, we have fabricated a polyimide aerogel (PIA) film with porosity up to 98.01% and thickness about 220 μm and built a liquid analyzer with this PIA film as a tribo-negative layer. The liquid analyzer can respond to different liquid droplets on the basis of liquid–solid interaction and the triboelectric effect. Benefitting from the mesoporous structure, high porosity, low thickness, and stable compression performance of the PIA film, the liquid analyzer shows fast response and good robustness for detecting different liquids down to 7 μL. The mechanisms of the analyzer for distinguishing liquids are discussed from the aspects of effective relative permittivity, the interaction between liquid and PIA film, and transfer charge quantity. The trace liquid analyzers based on high-performance PIA films provide support for the development of environmental protection and biochemical sensing and show huge application potential in sensing related areas.

Stress-Charge Nonlinear Physical Description and Tensor Symmetries for Piezoelectric Materials.

Nonlinear piezoelectric materials are raised as a great replacement for devices that require low power consumption, high sensitivity, and accurate transduction, fitting with the demanding requirements of new technologies such as the Fifth-Generation of telecommunications (5G), the Internet of Things (IoT), and modern radio frequency (RF) applications. In this work, the state equations that correctly predict the nonlinear piezoelectric phenomena observed experimentally are presented. Furthermore, we developed a fast methodology to implement the state equations in the main FEM simulation software, allowing an easy design and characterization of this type of device, as the symmetry structures for high-order tensors are shown and explained. The operation regime of each high-order tensor is discussed and connected with the main nonlinear phenomena reported in the literature. Finally, to demonstrate our theoretical deductions, we used the experimental measurements, which presented the nonlinear effects, which were reproduced through simulations, obtaining maximum percent errors for the effective elasticity constants, relative effective permittivity, and resonance frequencies of 0.79%, 2.9%, and 0.3%, respectively, giving a proof of the potential of the nonlinear state equations presented for the unifying of all nonlinear phenomena observed in the piezoelectric devices.

A Low-Profile Wideband Patch Antenna With Modified Parasitic Mushroom Structures on Nonperiodic AMC

In this letter, a low-profile wideband antenna working around 28 GHz based on the nonperiodic artificial magnetic conductor (AMC) is presented. Mushroom structures are loaded with central patch to broaden bandwidth. Four vias at edges are added to suppress cross polarization. A parasitically coupled structure is integrated with AMC. The nonperiodic AMC, central patch, and parasitic structures create five resonant modes together. Characteristic mode analysis and effective relative permittivity of AMC are calculated to explain the bandwidth broadening mechanism. A prototype is fabricated to verify the design concept. The measured result shows wide impedance bandwidth of 33% (24.05–33.52 GHz) and high peak gain of 10.24 dBi.

Accurate Closed Form expressions for Conductor Loss and Dielectric Loss in Thin Film Microstrip Line

Accurate Closed Form expressions for Conductor Loss and Dielectric Loss in Thin Film Microstrip Line

Composite Metamaterial: Ferrite Matrix with Ferroelectric Inclusions

A metamaterial based on periodic ferroelectric inhomogeneities in a magnetic ferrite matrix including a quantity of ferroelectric composite in a matrix, demonstrating relative low microwave losses and effective dielectric permittivity, was produced. Glass-ceramic composites, consisting of low-melting glass and barium-strontium titanate, were successfully synthesized and incorporated into the periodic holes of the ferrite matrix to build the meta-structure. Investigation of the structure showed dielectric permittivity, which increased with the volume of ferroelectric inclusions. The range of magnetically controlled interactions of the meta-structures with an electro-magnetic field was increased for the matrix with periodic holes filled by the ferroelectric composite in comparison with the basic ferrite matrix. The ferrite substrate completely determined the microwave losses of the sample and the ferroelectric inclusions increased the Q-factor of the meta-structure.

DTCO flow for air spacer generation and its impact on power and performance at N7

A novel DTCO flow is described with the principal aim to study the impact of air spacer fabrication on the power and performance of a 5-stage inverter ring oscillator at the 7 nm node. The flow incorporates physical and analytical process models from the in-house ViennaPS simulation tool together with device and circuit simulations from GTS Framework’s Cell Designer. The air spacer is usually filled by sequential conformal and non-conformal deposition steps. The impact of the thickness of the conformal layer and the sticking probability during non-conformal deposition on the ring oscillator performance is studied here. The air gap, which forms the core of the air spacer, is generated during the non-conformal deposition step. We extract the relative effective permittivity of the air spacer as a function of these two fabrication parameters by solving the Poisson equation to obtain the spacer capacitance. Finally, SPICE model cards are extracted automatically from the TCAD transistor characteristics and the parasitic network is calculated from the full 3D ring oscillator logic cell using a field solver. We apply our framework on two fabrication flows, when the air gap is created before and after the deposition of the first metal contacts layer. We observe that introducing the air gap inside the spacer results in an at-least 15% improvement in the ring oscillator’s performance, when the power is kept constant. Further improvements can be achieved by reducing the conformal layer thickness and increasing the sticking probability by increasing the chamber partial pressure or increasing the process temperature.

Effective Complex Permittivity of Random Composite Media: PVDF/(Na<sub>1/2</sub>Bi<sub>1/2</sub>)TiO<sub>3</sub>

The present study discusses the fabrication of non-lead ceramic/polymer composites employing (Na1/2Bi1/2)TiO3 (NBT) ceramic powder as a filler and poly(vinylidene fluoride); PVDF as a polymer matrix. The NBT (volume fraction, ϕ = 1) ceramics were synthesized using the conventional mixed-oxide method followed by the high-energy ball milling method whereas (1-ϕ)PVDF/ϕ(Na1/2Bi1/2)TiO3; 0 ≤ ϕ ≤ 0.3 composites were prepared from a melt-mixing process. It was observed that the real and imaginary parts of dielectric permittivity, ac conductivity, and longitudinal piezoelectric charge coefficient increase with the increase in NBT-content. Different dielectric mixing models were presented to determine the effective complex permittivity of the composites. Five dielectric mixture equations have been chosen to test the acceptability of experimental data. It was revealed that theoretical models as given by Bruggman, Rother-Lichtenecker, and modified Rother-Lichtenecker show good agreement with the experimental results of filler-concentration dependent alteration of effective relative permittivity and loss factor of the PVDF/NBT composite. A mathematical model of first-order exponential growth has also been proposed, which fitted excellently the experimental data (r2 > 0.998).

Utilizing ferrorestorable polarization in energy-storage ceramic capacitors

A self-powered system with a long lifetime would represent an opportunity in the development of a next-generation, standalone Internet of Things. Ceramic capacitors are promising candidates for energy storage components because of their stability and fast charge/discharge capabilities. However, even the energy density of state-of-the-art capacitors needs to be increased markedly for this application. Improving the breakdown electric field represents a potential solution, but operations at such high fields relying on unchanged dielectric permittivity sacrifice the lifetime of the capacitor to some degree. Here, we report ferrorestorable polarization engineering capable of more than doubling the effective permittivity. Our experiments and ab initio calculations demonstrate that a defect dipole composed of Cu3+ and oxygen vacancy in a prototypical ferroelectric BaTiO3 ceramic is coupled with spontaneous polarization. The resultant ferrorestorable polarization delivers an extraordinarily large effective relative permittivity, beyond 7000, with a high energy efficiency up to 89%. Our work paves the way to realizing efficient ceramic capacitors for self-powered applications.

Extension of Babinet Principle to Complementary Metallic Elements on the Interface of Different Substrates

In this letter, the existing Babinet principle is extended to two-dimensional complementary metallic elements on the interface of different substrates. Specifically, the existing Babinet principle requests homogenized substrate to cover complementary metallic elements. In order to break this restriction, the concept of effective relative permittivity is introduced to keep the original boundary condition unchanged. Further, the extended Babinet principle is expressed as a mathematical equation including vector fields of complementary metallic elements on the substrate interface. Especially, the proposed theory is related to the accuracy of the effective permittivity. In order to verify the proposed theory, the extended Babinet principle is applied to complementary metasurfaces with the approximate effective permittivity. Great consistence exists between theoretical and simulated results. Thus, the extended Babinet principle not only provides a theoretical approach to analyze complementary metallic elements on the substrate interface but also greatly enriches the physical connotation of existing Babinet principle.

Bandstop filtering for integrated substrate gap waveguide high‐gain and wideband slot antenna for 5G

Slot antenna based on microstrip line and waveguide is a popular design for future 5G antennas. To improve performance of slot antenna, a high-gain wideband slot antenna based on integrated substrate gap waveguide (ISGW) is presented, in which a stepped impedance feeding line is adopted to broaden bandwidth, and ISGW is used to increase gain. First, the transmission characteristics and the effective relative permittivity of ISGW is discussed and calculated, with operation band from 25 to 45 GHz. The antenna has a passband of 24.9–38.1 GHz, that is, almost Ka band, and an average gain of ~9 dB. Further, bandstop filtering (BSF) characteristic is introduced in the above wideband antenna to achieve filtering antennas for 5G millimeter-wave (mm-wave) bands of 24.75–27.5 GHz for China, and 26.5–29.5, 27.5–28.5, and 37–40 GHz for n257, n258, and n260 of 5G new-radio (NR). The BSF is obtained by etching U-shaped CSRR on feeding patch of the antenna. First- and second-order BSF are achieved by etching first and second U-shaped CSRR on the antenna feeding patch, respectively, thus correspondingly one bandstop resonance at 34.6 GHz, and two bandstop resonances at both 32.5 and 34 GHz are obtained. It is found that the passband performance is unchanged, but the stopband radiation drops sharply at the boresight direction. The three antennas (wideband, and first- and second-order BSF antennas) proposed are all fabricated and verified.

Experimental Evaluation of Dielectric Losses of PPLP for Single Phase HTS Cable at Subcooled LN2 Temperatures

For the operation of high-temperature superconducting (HTS) power cables in liquid nitrogen (LN2 ) at high voltage levels, there is a need for reliable and cost-effective insulating materials. This article investigates the dielectric losses in poly-propylene laminated paper (PPLP- Sumitomo) which is used as a cold dielectric for HTS cables. To calculate the dielectric losses, an experimental setup was developed to measure the relative permittivity of PPLP at different temperatures from 65 to 300 K at various frequencies. Using an in-house developed experimental setup, the dielectric loss for different layers of PPLP, at various temperatures and operating frequencies was estimated to evaluate one of the criteria of cold dielectric material and the same was compared with the data at room temperature. The temperature was reduced to 65 K using a vacuum pump-assisted sub-cooling system. The effective relative permittivity increases marginally for subcooled LN2 impregnated PPLP, however there is reduction in tan delta loss which in turn reduces the dielectric loss and is useful for high voltage HTS based AC cables. This paper provides a comparative study on PPLP performance variation with respect to operating temperature and frequency.