Capacitor Research Articles

Fabrication and characterization of low-loss Al/Si/Al parallel plate capacitors for superconducting quantum information applications

Increasing the density of superconducting circuits requires compact components, however, superconductor-based capacitors typically perform worse as dimensions are reduced due to loss at surfaces and interfaces. Here, parallel plate capacitors composed of aluminum-contacted, crystalline silicon fins are shown to be a promising technology for use in superconducting circuits by evaluating the performance of lumped element resonators and transmon qubits. High aspect ratio Si-fin capacitors having widths below 300 nm with an approximate total height of 3 μm are fabricated using anisotropic wet etching of Si(110) substrates followed by aluminum metallization. The single-crystal Si capacitors are incorporated in lumped element resonators and transmons by shunting them with lithographically patterned aluminum inductors and conventional Al/AlOx/Al Josephson junctions respectively. Microwave characterization of these devices suggests state-of-the-art performance for superconducting parallel plate capacitors with low power internal quality factor of lumped element resonators greater than 500 k and qubit T1 times greater than 25 μs. These results suggest that Si-Fins are a promising technology for applications that require low-loss, compact, superconductor-based capacitors with minimal stray capacitance.

The Effect of Metal Shielding Layer on Electrostatic Attraction Issue in Glass-Silicon Anodic Bonding.

Silicon-glass anode bonding is the key technology in the process of wafer-level packaging for MEMS sensors. During the anodic bonding process, the device may experience adhesion failure due to the influence of electric field forces. A common solution is to add a metal shielding layer between the glass substrate and the device. In order to solve the problem of device failure caused by the electrostatic attraction phenomenon, this paper designed a double-ended solidly supported cantilever beam parallel plate capacitor structure, focusing on the study of the critical size of the window opening in the metal layer for the electric field shielding effect. The metal shield consists of 400 Å of Cr and 3400 Å of Au. Based on theoretical calculations, simulation analysis, and experimental testing, it was determined that the critical size for an individual opening in the metal layer is 180 μm × 180 μm, with the movable part positioned 5 μm from the bottom, which does not lead to failure caused by stiction due to electrostatic pull-in of the detection structure. It was proven that the metal shielding layer is effective in avoiding suction problems in secondary anode bonding.

Synergistic Effect of a Ni/Al2O3+YSZ Nanocomposite for the Steam Reforming of Biogas in the Presence of Electric Fields

There is an increasing interest in using biogas as a renewable energy source to produce green hydrogen via steam reforming. The high‐energy consumption associated with this process has motivated the pursuit of alternative approaches to process raw biogas at lower operating temperatures and without the need for large amounts of steam to prevent catalyst deactivation. The present study discusses the results obtained for the steam reforming of raw biogas in the presence of electric fields, using a nanocomposite catalytic material prepared by physically mixing yttria‐stabilized zirconia and a Ni/Al2O3 catalyst. The experiments are conducted using a parallel plate capacitor reactor operated at 700 °C and 1 atm. The results indicate that by applying an external electric field (EEF) with a DC voltage of 1.9 kV and a current of 9 mA, a substantial increase in the rates of reaction can be attained. The conversions obtained for CH4 and CO2 are higher than the equilibrium values calculated in the absence of an EEF by 23% and 17%, respectively. This shift in the equilibrium is attributed to internal electric fields (IEFs) resulting from the interaction between YSZ and Ni/Al2O3, which leads to the creation of an interfacial nanopore structure that could increase the local IEF strength.

Non-destructive assessment of the internal defects of FRED® pear by a low radio-frequency capacitive technique

Postharvest pear fruit internal browning damages were assessed non-destructively using a capacitive instrumental chain in the super low (SLF) – low (LF) radiofrequency region combined with Image analysis. A rapid, inexpensive, and non-destructive instrumental chain was set up: an LCR meter interfaced with a PC receives and transmits signals through a parallel plate capacitor in the frequency range from 100 Hz to 10 kHz. The capacitance data were used to classify the FRED® pear fruit into two classes, “with defects” and “healthy”, using the unsupervised fuzzy C-means clustering analysis. The main results show good classification rates: 91 % of the samples are correctly classified as damaged. Further samples should be implemented to understand how the model performs with samples from different ripening stages. Despite this, the technique appears promising for non-destructive internal quality assessment in pear fruit.

ЛОГАРИФМІЧНІ АНАЛОГО-ЦИФРОВІ ПЕРЕТВОРЮВАЧІ. ОГЛЯД

In this work, a review of logarithmic analog-to-digital converters (LADCs) was carried out and an analysis of their properties in the dynamic range of input signals of 80 dB was carried out. It is shown that the highest metrological characteristics are obtained by LADCs on switched capacitors (CC) using high-quality analog switches from Maxima and Analog Devices companies, in which parasitic interelectrode capacitances do not exceed 1 pF. LADC of different classes were considered. Serial LADCs on CC have the lowest speed, they are performed with redistribution or accumulation of charge (RC or AC) in capacitor cells, in which switching is carried out with analog switches; in such LADCs, the conversion error can be reduced to 0.25% (taking into account the quantization error of 0.1%) with a conversion time of no more than 20 ms. The same speed has LADC with pulse feedback, the conversion error of which is almost completely determined by the value of the quantization error for values ​​of the last 0.1% and more. Interpolation LADCs make it possible to reduce the conversion error below 0.1% with a conversion time of the order of hundreds of microseconds. Medium-speed LADCs with a conversion time of 100 μs or less include subband, recurrent, and bit-by-bit, which achieve a conversion error of 0.005%, 0.0015%, and 0.0015%, respectively. High-speed LADCs are parallel, their conversion error does not exceed 0.4% with a conversion time of less than 10 ns. Key words: logarithmic ADCs, construction, characteristics, parameters

ЛОГАРИФМІЧНІ АНАЛОГО-ЦИФРОВІ ПЕРЕТВОРЮВАЧІ. ОГЛЯД

In this work, a review of logarithmic analog-to-digital converters (LADCs) was carried out and an analysis of their properties in the dynamic range of input signals of 80 dB was carried out. It is shown that the highest metrological characteristics are obtained by LADCs on switched capacitors (CC) using high-quality analog switches from Maxima and Analog Devices companies, in which parasitic interelectrode capacitances do not exceed 1 pF. LADC of different classes were considered. Serial LADCs on CC have the lowest speed, they are performed with redistribution or accumulation of charge (RC or AC) in capacitor cells, in which switching is carried out with analog switches; in such LADCs, the conversion error can be reduced to 0.25% (taking into account the quantization error of 0.1%) with a conversion time of no more than 20 ms. The same speed has LADC with pulse feedback, the conversion error of which is almost completely determined by the value of the quantization error for values ​​of the last 0.1% and more. Interpolation LADCs make it possible to reduce the conversion error below 0.1% with a conversion time of the order of hundreds of microseconds. Medium-speed LADCs with a conversion time of 100 μs or less include subband, recurrent, and bit-by-bit, which achieve a conversion error of 0.005%, 0.0015%, and 0.0015%, respectively. High-speed LADCs are parallel, their conversion error does not exceed 0.4% with a conversion time of less than 10 ns. Key words: logarithmic ADCs, construction, characteristics, parameters

The intrinsic dielectric properties of Mediterranean bio-composites

Abstract The environment is seriously threatened by the growing use and disposal of technological products since most of them include non-biodegradable components. One approach to reduce environmental impact of electronic devices is to use biodegradable electronic components derived from natural fibers like protein and cellulose. Actually, a lot of research has been done on the viability of producing electronic components out of materials obtained from natural fibers. Their inclusion of several changeable functional categories is another benefit. Dielectric materials are one of the several necessary and commonplace parts of technical devices. A thorough study on the varieties of natural fibers used to make dielectric materials and their electrical properties would be beneficial in selecting the appropriate fibers and conditions for certain applications. To make full use of new natural composite materials in growing sectors, their electric properties have to be examined. However, along with polypropylene, four different kinds of natural lignocellulosic fibers will be discussed in this work: black pepper, sumac, pomegranate, and lemon – as case studies. In specific, over a frequency range of 1 KHz to 4 MH, the AC conductivity and dielectric constant of the produced samples were measured using the method of parallel plate capacitors. After that, given the performance of sisal fibers, a comparison between them and a sisal natural fiber (a non-Mediterranean variety) will be made.

Preparation of Freestanding Films Using Barium Titanate Nanoparticles and Their Electrical and Optical Properties

BaTiO3 ferroelectric perovskites have been applied to a variety of applications, including multilayer ceramic capacitors (MLCC), piezoelectric transducers, actuators, thermistors with positive temperature coefficient, and ultrasonic devices. In the development of MLCC manufacturing processes, understanding the relationship between the particle size and structure of barium titanate material particles, the phase transition temperature to the ferroelectric phase, and dielectric properties is very important for understanding the design and transformation of the material particles. We have studied the evaluation of phase transition temperatures using X-ray diffraction and SHG analysis.In this study, barium titanate nanoparticles with a diameter of approximately 50 nm were used to formulate a paste by mixing with solvents and resins. The production method was modeled on the already commercialized Ag paste method. After screen printing, the paste was heat-treated at 110°C to solidify to form a freestanding film. The creation of freestanding films allows for easy control of film thickness without the influence of the substrate, which is expected to expand the range of applications. After further heat treatment at over 1000°C, Pt electrodes were formed on both sides of the film by sputtering, and the dielectric constant and its temperature change were evaluated as a parallel plate capacitor. Typical film thickness is 200 μm. As a result, it was found that the dielectric constant was higher than that of the bulk material, with a maximum value around 120°C. The loss was found to be very small, less than 0.05. These results indicate that the material is highly practical. XRD results also confirmed the existence of a phase transition temperature around 120°C. Furthermore, SHG results also corroborate the XRD results. Details of the paste preparation method, freestanding films, evaluation by cross-sectional SEM after heat treatment, temperature dependence of dielectric properties, and evaluated nanoparticle properties will be discussed.

The electromagnetic field of a circular parallel plate capacitor excited by an AC current and AC voltage supply

Abstract This study investigates the electromagnetic field (EMF) distribution of an ideal circular parallel plate capacitor excited by a time-harmonic power source. Considering the lead wire and capacitor as a charged whole, we formulate the boundary value problems of the Helmholtz equation for the EMF in the lead wire space and capacitor space, respectively. First, we solve for the EMF generated by the total current in the lead wire space of an AC current. Following this, we solve for the EMF boundary value problem of a capacitor filled with linear, uniform, isotropic, and non-magnetic lossy dielectric under an AC current excitation, using the continuity of the total current as a basis. Second, the EMF distributions in the capacitor space and the lead wire space under an AC voltage excitation are provided, following the principles of the generalized Helmholtz theorem. Third, the EMF distribution is discussed when the electromagnetic ‘standing-wave phenomenon’ occurs in the ideal dielectric capacitor, and identify the ‘resonance phenomenon’ and the ‘current-stopping phenomenon’ of the capacitor's EMF when excited by an AC current and AC voltage, respectively. We also present the corresponding ‘resonance frequency’ and ‘current-stopping frequency’. Finally, we explore the quasi-stable solution of the capacitor's EMF under low-frequency condition and the static solutions of the electric and magnetic fields under DC excitation and static voltage excitation. Our findings suggest that the existing formula for the capacitor's EMF approximates our analytical solution under quasi-stable condition.

The Influence of Radiofrequency Heating on the Quality and Shelf of Life of Pepper

Pepper is one of the common vegetable food items that constitute most African dishes with beneficial health properties. This study investigates the influence of radiofrequency (RF) heating on the quality and shelf life of pepper. Utilising the measured dielectric properties of pepper, the research evaluates how microwave exposure at varying frequencies affects pepper's nutritional content and preservation duration. Fresh samples of pepper were subjected to radio waves ranging from 5 MHz to 25 MHz, and their dielectric properties, proximate composition, and shelf life were analysed. The dielectric properties were measured using a parallel plate capacitance method, revealing significant variations in conductivity, dielectric constant, and loss factor across different frequencies. Results demonstrated that RF treatment effectively extended the shelf life of pepper, with the highest frequency (25 MHz) achieving a shelf life of 36 days, compared to 20 days for the control. Moreover, the study observed minimal changes in the proximate composition of pepper, ensuring the retention of its nutritional quality. This research provides valuable insights into the use of RF heating as a viable technique for extending the shelf life of pepper while maintaining its nutritional integrity.

2D heterostructures of graphene oxide and MoS2 to improve sensitivity performance of flexible pressure sensor with shell biological structure

Inspired by the multilayer structure of the shellfish, a novel two-dimensional (2D) composite structure consisting of graphene oxide, MoS2 and graphene oxide (G/M/G) was integrated to the flexible pressure sensing. The composite structure was prepared by the vacuum suction filtration in order to imitate the high toughness of shellfish. Based on the strategy of strain engineering, a comprehensive experimental bench capable of meeting different strain conditions was connected to a push–pull meter and an LCR digital bridge, and then a computer was used to record the changes in transducer capacitance when an external load was applied to the meter. Graphene oxide (GO) and G/M/G supercells were constructed, and density functional theory (DFT) simulations of the initial energy band structure under strain-free conditions were carried out to determine the relationship between the band gap, conductivity, capacitance, and sensitivity of the G/M/G structure based on band gap theory, and to easily understand the mechanism of the shellfish heterostructure leading to enhanced sensitivity of the sensors. Using two-point bending and axial tensile tests, a flexible pressure sensing device was designed to realize positive strains in the ranges of 0%–5 % and 5%–50 %. The results show that the sensitivity of both GO and G/M/G capacitive pressure sensors decreased with increased strain, and the sensitivity of the G/M/G sensors was significantly improved by 75%–102 % compared to the GO sensors at the same strain. The parallel-plate capacitor model and crack growth theory well explain the experimental results at small and large strains. Our results provide new concepts for the design of novel flexible sonar with high sensitivity and large strain operating range by a simple vacuum filtration method, which can be extended to the design of other high-performance 2D flexible electronic devices.

Miniaturized FSS With Ultrawide Out-of-Band Suppression Based on Parallel-Plate Capacitor

Miniaturized FSS With Ultrawide Out-of-Band Suppression Based on Parallel-Plate Capacitor

Dielectric characteristics of Mediterranean lignocellulosic fibers for functional biocomposite materials

Abstract The primary aim of this study is to investigate the dielectric properties of lignocellulosic fibers, a unique kind of natural fiber prevalent in the Mediterranean area. Comprehensive investigations were undertaken to determine the suitability of these fibers for functional biomaterials and to reveal their potential capabilities comparable to those commonly used in other parts of the world. More exploration of the electrical characteristics of agricultural waste fibers may lead to the development and improvement of a more comprehensive knowledge on their use in the production of practical eco-products. This will provide novel opportunities for ecologically conscious design. Based on the introduction of natural fibers and their advantages in biomaterials, this study will examine the parallel plate capacitor approach to assess the dielectric properties of biological fibers. Subsequently, the impact of maleic anhydride on the dielectric properties of natural fiber composites was demonstrated as a focused case study. Therefore, it is possible to develop a suitable database for the selection of visually appealing materials in order to enhance comprehensive knowledge of the intrinsic electrical properties and attributes of these materials. Consequently, this would result in the development of more practical strategies for designing environmentally friendly products in bio-electronics and the identification of novel biomaterials with potential applications in electronics.

Lumped-element SNAIL parametric amplifier with two-pole matching network

Broadband impedance-matched Josephson parametric amplifiers are key components for high-fidelity single-shot multi-qubit readout. Nowadays, several types of impedance matched parametric amplifiers have been proposed: the first is an impedance-matched parametric amplifier based on a Klopfenstein taper, and the second is the impedance-matched parametric amplifier based on auxiliary resonators. Here, we present the quantum-limited 3-wave-mixing lumped-element SNAIL parametric amplifier with two-pole impedance matching transformer. A two-pole Chebyshev matching network with shunted resonators is based on parallel-plate capacitors and superconducting planar coil. Operating in a flux-pumped mode, we experimentally demonstrate an average gain of 15 dB across a 600 MHz bandwidth, along with an average saturation power of −107 dBm and quantum-limited noise temperature.

Ultrathin nanocapacitor assembled via atomic layer deposition

We fabricated ultrathin metal - oxide - semiconductor (MOS) nanocapacitors using atomic layer deposition. The capacitors consist of a bilayer of Al2O3 and Y2O3 with a total thickness of ~10 nm, deposited on silicon substrate. The presence of the two materials, each slab being ~5 nm thick and uniform over a large area, was confirmed with Transmission Electron Microscopy and X-ray photoelectron spectroscopy (XPS). The capacitance in accumulation varied from 1.6 nF (at 1MHz) to ~2.8 nF (at 10 kHz), which is one to two orders of magnitude higher than other nanocapacitors. This high capacitance is attributed to the synergy between the dielectric properties of ultrathin Al2O3 and Y2O3 layers. The electrical properties of the nanocapacitor are stable within a wide range of temperatures, from 25 °C to 150 °C, as indicated by capacitance-voltage (C - V). Since the thickness-to-area ratio is negligible, the nanocapacitor could be simulated as a single parallel plate capacitor in COMSOL Multiphysics, with good agreement between experimental and simulation data. As a proof-of-concept we simulated a MOSFET device with the nanocapacitor gate dielectric, whose drain current is sufficiently high for micro and nanoelectronics integrated circuits, including for applications in sensing.

Flow-through microfluidic relative permittivity sensor using highly-doped silicon sidewall electrodes

Abstract This paper reports a flow-through sensor for the real-time measurement of the relative permittivity of a flowing fluid. The proposed sensor contains multiple parallel microchannels. Each channel acts as a parallel plate capacitor in which the electrodes are isolated from the fluid. This approach results in a low pressure drop and high sensitivity while the internal volume is only 50 nl. The fabrication technology allows for controllable scaling of the channel geometry. Equally deep microchannels with widths varying between 5 µm and 50 μ m are fabricated. The fabrication technology is compatible with other flow-through sensors, enabling further on-chip integration. The sensor has been characterised using 10 different fluids with relative permittivity values ranging from 1 to 80—including water and water-containing mixtures—at a measurement frequency of 300 kHz. The results show an accuracy within 3% of full scale and the repeated measurements with nitrogen and water show standard deviations of 1.20 and 1.03, respectively.

In situ assembly enabling adhesive-free bonding of large area electronic sensors to concrete for structural health monitoring

Abstract Cracks developed in concrete infrastructure are one of the primary mechanisms that degrade their structural integrity, which may result in structural failures. Previous research on soft elastomeric capacitors (SEC) has shown their viability for structural health monitoring of structural materials, including concrete, steel, and fiberglass composites. The SEC, or its derivative version with a corrugated geometry termed corrugated SEC or cSEC, is a parallel plate capacitor. Prior work demonstrated that it was possible to directly paint the electrode interfacing with the structural material onto the structure and adhere the rest of the pre-fabricated sensor onto the wet interface, thereby eliminating the need for a joining epoxy. This demonstration was conducted on steel and fiberglass. The study on concrete was left to future work as concrete exhibits a much rougher surface and structure/sensor capacitive coupling, causing a significant amplification in signal noise. This study advances structural health monitoring in concrete applications by investigating the in situ assembly of the SEC on concrete where the carbon black (CB)-based electrode plate of the cSEC is directly painted onto the concrete surface and serves as both the adhesive and electrode for the sensor. A series of free-vibration and compression tests were designed and conducted to evaluate the sensing performance of in situ assembled cSEC compared to that of an epoxy-bonded cSEC. Additionally, the bonding strength of the in situ assembled and epoxy-bonded cSEC is evaluated through a peel test. Results show good strain sensing capabilities of the in situ assembled SEC with an R 2 value of 0.986 and a resolution of 45 ± μ ε . Even though the epoxied cSEC demonstrated a higher bonding strength than the in situ assembled cSEC, the in situ assembled cSEC demonstrated adequate bonding strength for the application. This research contributes to the scientific understanding of sensor adhesion and opens avenues for practical applications in infrastructure monitoring, potentially leading to more resilient and sustainable urban environments.

TLS noise reduction in microwave kinetic inductance detectors using a parallel plate capacitor with a three-layer dielectric

<p>Over the past two decades, microwave kinetic inductance detectors (MKIDs) have gained exceptional importance in millimeter and sub-millimeter astronomy. MKIDs consist of thin strip resonators capable of detecting changes in the surface impedance of superconductor strips, which result from variations in resonance circuit properties. The principal noise in MKIDs comprises excess frequency noise and two-level system noise. In this paper, we propose a technique to mitigate the effect of two-level system (TLS) noise in MKIDs using a parallel plate capacitor with three layers of high ε dielectrics. To achieve this, we employ three layers of Al<sub>2</sub>O<sub>3</sub>, HfO<sub>2</sub>, and TiO<sub>2</sub> with equal thickness between the capacitor plates. The experimental results demonstrate a nearly 30% reduction in TLS power spectral density.<strong></strong></p>

Mimicking Antiferroelectrics with Ferroelectric Superlattices.

Antiferroelectric oxides are promising materials for applications in high-density energy storage, solid-state cooling, and negative capacitance devices. However, the range of oxide antiferroelectrics available today is rather limited. In this work, it is demonstrated that antiferroelectric properties can be electrostatically engineered in artificially layered ferroelectric superlattices. Using a combination of synchrotron X-ray nanodiffraction, scanning transmission electron microscopy, macroscopic electrical measurements, and lateral and vertical piezoresponse force microscopy in parallel-plate capacitor geometry, a highly reversible field-induced transition is observed from a stable in-plane polarized state to a state with in-plane and out-of-plane polarized nanodomains that mimics, at the domain level, the nonpolar to polar transition of traditional antiferroelectrics, with corresponding polarization-voltage double hysteresis and comparable energy storage capacity. Furthermore, it is found that such superlattices exhibit large out-of-plane dielectric responses without involving flux-closure domain dynamics. These results demonstrate that electrostatic and strain engineering in artificially layered materials offers a promising route for the creation of synthetic antiferroelectrics.

Fast-response and high figure of merit phase shifter based on polymer- stabilised liquid crystals

ABSTRACT This article presents a novel fast-response and high figure of merit (FoM) phase shifter based on polymer-stabilised liquid crystal (LC) for Ka-band. The developed LC phase shifter (LCPS), utilising a coplanar differential line loading 19 parallel-plate variable capacitors with 4.6 μm LC-cell, adopts polymer-stabilised LC technology in which the parallelly orientated polymer networks facilitate the LC molecules’ return to their initial state upon removal of the bias voltage, thus accelerating response time. The proposed LCPS has been fabricated to evaluate its superior capabilities. The experimental results closely match the simulation results, confirming its good congruity. This design has measured S 11 < −10 dB in 29–31 GHz. LCs with different HCM002 concentrations are injected to LCPS, and the experimental outcomes showed that LCs with 9 wt% HCM002 concentration significantly improve the response time of LCPS to 2.8 ms with a high FoM of 91.2°/dB at 30 GHz.