Dielectric Layer Research Articles

Research on the Thermal Aging Characteristics of Crosslinked Polyethylene Cables Based on Polarization and Depolarization Current Measurement

Although XLPE cables are widely used in power transmission and distribution systems, their insulating properties are susceptible to degradation due to thermal aging. In order to clarify the influence law of the thermal aging process on the structural and dielectric properties of XLPE cables, this paper investigates the thermal aging characteristics of XLPE cables by using polarization and depolarization current measurement. Results show that when the XLPE cable is aged at 140 °C, the crystallinity of the insulation layer appears to increase and then decrease. With the increase in aging time, micron-sized microvoids appear on the surface of the XLPE. At the same time, the DC conductivity and 0.1 Hz dielectric loss factor of the insulating layer increase with the aging time. The average DC conductivity increased from 2.26 × 10−16 S/m for new cables to 4.47 × 10−16 S/m after aging for 432 h, while the dielectric loss increased from 0.11% to 0.42%. The polarization characteristics of thermal-aged cables were further analyzed using the extended Debye model. Results indicate that the time constant of the third branch of the model increased significantly with increasing aging time. A correspondence between this parameter and the thermal aging time of the cable was established. Thermal aging can damage the crystalline structure of XLPE, so that the number of interfaces between the crystalline and amorphous regions of the material increases, resulting in structural damages and a decline in the dielectric properties of the cable insulation.

A two-layer single shell magnetized target for lessening the Nernst effect

Fuel magnetization significantly lowers the required radial convergence, enabling cylindrical implosions to become a promising approach for inertial confinement fusion. The Nernst effect on the two-layer single shell magnetized target design applied to a Z-pinch benefits from a gold layer that decreases fuel demagnetization and serves as a magnetothermal insulation layer, preventing magnetothermal losses. The resistive diffusion and Nernst advection of the magnetic field are considered in the radiation magnetohydrodynamic model, which alter the evolution of magnetic flux in the magnetized target and result in plasma demagnetization. The results demonstrate that targets with a wide range of parameters can achieve ignition conditions under a 30 MA driven current. A two-layer single shell magnetized target for lessening the Nernst effect has the potential to achieve ignition conditions. The fusion yield of the optimal target increases by 168% from 0.71 MJ to 1.90 MJ, compared to a one-layer single shell target.

Solar thermal applications of graphene-based block-ring resonator solar absorber using TiC–W materials

Solar absorbers enable the use of solar energy, a renewable and plentiful resource, minimizing reliance on finite fossil fuels and contributing to sustainable energy practices. The solar absorber that is studied here has an average absorptance of 96.85 % with a simple design and inexpensive materials. This design has two layers of resonator and active layer Block Ring Base Solar Absorber (BRBSA) structure. This study employs tungsten (W) as a resonator and titanium carbide (TiC) as a dielectric layer. The absorption spans from 100 to 3200 nm, with an average absorption exceeding 94 % across the entire structure. Notably, over 97 % of absorption occurs within the range of 210–710 nm, and the highest absorption, reaching 99.9 %, is observed in the wavelength range of 1510–1650 nm. The structure demonstrates high absorption rates across various regions, including 95.85 % in the UV region, 97.89 % in the visible, 95.73 % in the near-infrared, 95.87 % in the mid-infrared, and 89.56 % in the far-infrared region. After analyzing various potential variations of the proposed structure, an optimal design was identified. The parametric study was conducted to determine the optimal physical properties. Additionally, the electric field intensity analysis confirmed the proposed structure's broadband and constant absorption response. This Block Ring Base Solar Absorber has various uses, including solar drying systems, cookers, vaporizers, and warmers.

Low-temperature preparation and characteristics of top-gate thin-film transistors with La-ZTO active layers and polymethylmethacrylate dielectric layers

A top-gate coplanar-structure thin-film transistor (TFT) combining the advantages of both a co-sputtered amorphous La-doped ZnSnO (a-La-ZTO) active layer and solution-based polymethylmethacrylate (PMMA) gate dielectric layer has been prepared under low temperature (100 °C) with low cost for the first time. The results indicate that the PMMA thin film demonstrates anti-reflection properties when it combines with a-La-ZTO layer to form a double-layer film, displaying high transparency to visible light of ∼90.3%. Moreover, it was found that the La target power during the deposition of a-La-ZTO film plays an important role in suppressing the formation of oxygen vacancies and adjusting the carrier concentration of a-La-ZTO active layer, thus impacting a-La-ZTO TFT performance. Overall, the optimum a-La-ZTO TFT with a La target power of 13.9 W, working in an n-channel enhancement mode, possesses a large saturated mobility (>10 cm2 (Vs)−1) and an on/off drain current ratio over 105.

Double Resonance Characteristic of Photonic Crystal Structure with Defect Metal Layer

The optical response of the photonic crystal structure has been analyzed using the Finite Difference Frequency Domain (FDFD) method. Simulation using this method aims to analyze the characteristics of light transmission when interacting with related structure. The results of the study of photonic crystal structures with two defects show that there are two transmittance bands called double resonances at two specific wavelengths. Changes in the resonance peak with respect to the variations of refractive index in the second defect layer resulted in a linear change with significant sensitivity. For photonic crystals with two defects, the first defect is a metal layer and the second defect is material sensing, which produces double resonance with a sensitivity of 7,825 and 3,2675, while for photonic crystals with the first defect, a dielectric layer, and the second defect is material sensing, produces single resonance with a sensitivity of 2,022. The choice of the first defect is that the metal layer is quite important, in addition to producing greater sensitivity, it also produces a field enhancement between the dielectric and the metal layer which is called surface plasmon resonance (SPR). The sensitivity value can also be set by determining the thickness of the second defect layer. These results can be used as a standard for fabrication and developed for sensor applications.

Significant enhancement of optical absorption of graphene inside a metallic optical microcavity

The increase in the optical absorption of the graphene layers above the value of 2.3% of the bare layer in vacuum is of great interest for application in opto-electronics. A monolayer graphene sheet embedded in a stacked dielectric layers has been shown to reach an absorption up to 50%. Here, we theoretically show that the absorption could be significantly enhanced to greater than 50% via boosting the environmental permeability by using an empty optical cavity. This enhancement is nearly independent on the structure of the environment around the graphene sheet, except for the dimensional parameters of the cavity. The obtained results are crucial for motional control of graphene sheets by an all-optical method.

Investigating the inhibition of short channel effects using different materials of gate insulator layers in FinFET

As the evolution of FinFET technology continues, traditional gate insulator materials, such as SiO2, face challenges in meeting the demands of modern applications, especially when it comes to gate leakage current control. Emerging as promising contenders to replace SiO2, materials with higher dielectric constants, notably HfO2 and Si3N4, are drawing significant attention in the semiconductor community. Leveraging the advanced capabilities of tools like Silvaco TCAD, an in-depth analysis was conducted to compare the performance and gate leakage current control abilities of SiO2, HfO2, and Si3N4, utilizing the Quantum examples 3D FinFET model. The findings not only highlight the potential of HfO2 and Si3N4 as worthy replacements for SiO2 but also accentuate the distinct advantages of SiO2, making it particularly well-suited as a substitute. This exploration goes beyond a mere comparison of materials. It dives deep into understanding their behaviors under various operational conditions, laying a foundation for potential breakthroughs and fostering the next wave of innovations in semiconductor technology.

Optimizing molybdenum oxide based RRAM with vacuum rapid thermal annealing and carbon quantum dots

The performance of resistive random access memory (RRAM) is significantly influenced by the dielectric layer and interface. In this study, the vacuum rapid thermal annealing (VacRTA) process and the incorporation of carbon quantum dots (CQDs) were employed to enhance the device performance. The VacRTA process induced extra oxygen vacancies in the MoOx film, reducing the energy required for the formation of Ag conductive filaments (CFs). In addition, CQDs were spin-coated on the bottom electrode (BE) interface to effectively fix the position of Ag CFs formation and rupture. The improved device exhibits remarkable performance enhancements compared to the pristine device, including a centralized distribution of resistance states and operating voltages, extended endurance cycles (1 × 107), enhanced cell-to-cell coherence, and favorable neural synaptic properties. These results demonstrate the potential of CQDs incorporated MoOx based RRAM for next generation non-volatile memory and neural synapse simulation.

Gait Pattern Analysis: Integration of a Highly Sensitive Flexible Pressure Sensor on a Wireless Instrumented Insole.

Gait phase monitoring wearable sensors play a crucial role in assessing both health and athletic performance, offering valuable insights into an individual's gait pattern. In this study, we introduced a simple and cost-effective capacitive gait sensor manufacturing approach, utilizing a micropatterned polydimethylsiloxane dielectric layer placed between screen-printed silver electrodes. The sensor demonstrated inherent stretchability and durability, even when the electrode was bent at a 45-degree angle, it maintained an electrode resistance of approximately 3 Ω. This feature is particularly advantageous for gait monitoring applications. Furthermore, the fabricated flexible capacitive pressure sensor exhibited higher sensitivity and linearity at both low and high pressure and displayed very good stability. Notably, the sensors demonstrated rapid response and recovery times for both under low and high pressure. To further explore the capabilities of these new sensors, they were successfully tested as insole-type pressure sensors for real-time gait signal monitoring. The sensors displayed a well-balanced combination of sensitivity and response time, making them well-suited for gait analysis. Beyond gait analysis, the proposed sensor holds the potential for a wide range of applications within biomedical, sports, and commercial systems where soft and conformable sensors are preferred.

Theoretical Insight into the Band Alignment at High-κ Oxide XO2/Diamond (X = Hf and Zr) Interfaces with a SiO2 Interlayer for MOS Devices.

Diamond has become a promising candidate for high-power devices based on its ultrawide bandgap and excellent thermoelectric properties, where an appropriate gate dielectric has been a bottleneck hindering the development of diamond devices. Herein, we have systematically investigated the structural arrangement and electronic properties of diamond/high-κ oxide (HfO2, ZrO2) heterojunctions by first-principles calculations with a SiO2 interlayer. Charge analysis reveals that the C-Si bonding interface attracts a large amount of charge concentrated at the diamond interface, indicating the potential for the formation of a 2D hole gas (2DHG). The diamond/HfO2 and diamond/ZrO2 heterostructures exhibit similar "Type II" band alignments with VBOs of 2.47 and 2.21 eV, respectively, which is consistent with experimental predictions. The introduction of a SiO2 dielectric layer into the diamond/SiO2/high-κ stacks exhibits the typical "Type I″ straddling band offsets (BOs). In addition, the wide bandgap SiO2 interlayer keeps the valence band maximum (VBM) and conduction band minimum (CBM) in the stacks away from those of diamond, effectively confining the electrons and holes in MOS devices. This work exhibits the potential of SiO2/high-κ oxide gate dielectrics for diamond devices and provides theoretical insights into the rational design of high-quality gate dielectrics for diamond-based MOS device applications.

Broadband terahertz absorber based on patterned slotted vanadium dioxide

This study aims to explore broadband terahertz absorbers based on metamaterials by introducing a design featuring patterned slotted vanadium dioxide. This absorber structure includes a vanadium dioxide resonator layer, an intermediate Topas dielectric layer, and an underlying metal reflector layer. To enhance the absorption bandwidth, the vanadium dioxide resonant layer is strategically patterned to optimize impedance matching. Simulation outcomes reveal that, under positive incidence, the absorption rate exceeds 90 % within the frequency range of 1.5–4.2 THz. The absorber demonstrates a substantial absorption bandwidth of 2.7 THz, centered at 2.85 THz, corresponding to a relative bandwidth of 94.7 %. Additionally, through modulation of the conductivity of vanadium dioxide, the absorption peak can be finely tuned, spanning from approximately 2.5 %–99 %. In addition, it's angularly symmetrical and exhibits absorption properties for wide-angle incidence. The tunable terahertz absorber designed in this paper simultaneously achieves high absorption over a wide frequency range, is dynamically tunable, and has a simple structure. From the application point of view, it can provide a way to realize detection, and imaging in the terahertz range.

Impact of sound-insulated joints in the dynamic behavior of Cross-Laminated Timber structures

Cross-Laminated Timber (CLT) has gained an increasing success and widespread diffusion among wood products. Due to the novelty of the components and the dry-assembling techniques, certain aspects of its behavior and performance remain unexplored; among these, the use of sound-insulated joints and brackets, along with their possible drawbacks on mechanical performance.In this paper the authors discuss the results of dynamic identification (ID) tests carried out on twin full-size CLT mockups (two-story), one of which was furnished with sound-insulation details based on an elastomeric interlayer. Ambient (white noise and random excitations) and forced vibration (mass shaker) tests were carried out to identify modal parameters.The paper mainly aims at: i) assessing potential differences in the overall dynamic behavior of the two mockups, likely due to the introduction of acoustic insulation, ii) detecting possible drawbacks of insulation layers on mechanical performances, iii) increasing the knowledge about dynamics of CLT structures.The results of Operational Modal Analysis (OMA) are presented and the variations in the dynamics between the mockups are discussed. The construction of finite element (FE) models and their calibration – with joint properties variations – are then presented. The outcomes revealed a drop of modal frequencies values (at least 20 %) upon the introduction of elastomeric insulation, whilst no significant alteration was observed in the mode shapes. Model updating based on the FE models demonstrated that the dynamic response and the frequency variations were mostly associated with wall-to-wall and wall-to-diaphragms joints, and hold-down connections.

Lantern-inspired capacitive pressure sensor with wide linear measuring range

In the field of pressure sensing, high sensitivity and linearity are two critical performance indicators, but striking a balance between them remains a prominent challenge for sensors. Existing solutions typically involve the structural design of electrodes or dielectric layers, often requiring complex and expensive techniques for designing microstructures. This study presents a novel flexible capacitive pressure sensor characterized by its low-cost nature, ease of manufacture, and scalability in design. The lantern accordion-like structure inspires the design of the dielectric layer and the porous structure is designed using thermally expandable microspheres (TEM). The synergy of surface microstructures and internal microstructures results in a high sensitivity of 3.07 × 10−3 kPa−1 within a wide linear response range of 0–100 kPa. The developed sensor is also evaluated for its weight detection capabilities, highlighting its promising weight and pressure data acquisition.

The Effect of Insulation Thickness on Heat Transfer Characteristics and Flammability in Tube Mesoscale Combustors

Micropower generator is a micro-scale energy source that has two main components, namely a micro/mesoscale combustor and thermophotovoltaics (TPV). The micro-scale combustor is one part that functions as a combustion chamber that produces heat in micropower plants. Heptane is used as fuel, while the combustor combustion chamber with a diameter of 3.5 mm is made from duraluminium-quart glass tube. Combustion stability in the combustion chamber is influenced by several factors, such as temperature, geometry, and combustion chamber design. In order to maintain flame stability, mesh is added to the combustion chamber. One way to minimize heat loss in the combustion chamber is to add an insulating layer to the combustion chamber. This research aims to prove the role of adding an insulating layer in flame stability in mesoscale burners. It is necessary to add an appropriate insulating layer to minimize heat loss so that it remains stable in the mesoscale burner. This experimental test shows that the temperature distribution when adding an insulation layer with a thickness of 3 mm has a higher temperature on the outside compared to a thickness of 6 mm. Meanwhile, the temperature inside the combustor chamber with a thickness of 6 mm is superior to that with a thickness of 3 mm. The flame limit of the combustor with a mesh distance of 5 mm for liquid heptane fuel was successfully stable at an equivalent ratio of ɸ0.97 – 1.5 with a maximum speed of 31.7.

Transmission/reflection mode switchable ultra-broadband terahertz vanadium dioxide (VO2) metasurface filter for electromagnetic shielding application

In this paper, we present an ultra-broadband terahertz (THz) vanadium dioxides (VO2) metasurface (MS) filter with switchable transmission/reflection modes for electromagnetic (EM) shielding application. The MS filter is composed of a three-layer periodic composite structure, consisting of two VO2/metallic hybrid layers and a metal mesh layer, which are separated by two benzocyclobutene (BCB) dielectric layers. The transmission property of the proposed MS filter is illustrated by the numerical simulation based on the finite element method (FEM) and equivalent circuit model (ECM). When VO2 is in insulating state, the designed composite structure acts as a filter with ultra-broadband bandpass response (BPR), exhibiting that the transmission coefficient exceeds 90 % from 1.07 THz to 3.78 THz, with a relative bandwidth of 112 %. However, owing to thermal excitation, the VO2 converts from an insulating to a metallic state, the composite structure can be functioned as a filter with ultra-broadband bandstop response (BSR) with a transmission coefficient less than 6 % spanning the range of 0.1 to 4.5 THz. In addition, the physical mechanism of the designed MS filter is investigated utilizing impedance matching theory and electric field distribution analysis. Furthermore, the MS filter has good polarization insensitivity and angular stability. Finally, we quantify the shielding effectiveness (SE) in two states and evaluate the impact structural parameters of the unit-cell, resulting in a SE of more than 25 dB in reflection mode across the entire operating frequency range. Our proposed MS filter with its exquisite performance has the potential to be widely applied in EM shielding.

Multi-layer photothermal film inspired by polar bear fur for anti-icing and photothermal de-icing in cold environments

As climatic conditions worsen and time passes, icing becomes an unavoidable issue. Drawing inspiration from the thermal regulatory properties inherent in polar bear fur, we introduce a biomimetic three-layer film. This film comprises a hydrophobic shield, a photothermal conversion layer, and an insulating layer through electrospinning. The multilayered micro/nanostructure within this film amplifies its light absorption capabilities, achieving an average absorption rate of 96.27 % across wavelengths ranging from 200 to 2500 nm. Thanks to the insulation layer's thoughtful design, the film boasts high photothermal conversion efficiency. When exposed to solar radiation for 360 s at an ambient temperature of 20 °C, its surface temperature swiftly climbs to 98.3 ± 1.1 °C. The film's anti-icing capabilities are evidenced by the fact that a droplet of water takes 2964.7 s to freeze on its surface, which is approximately 118 times that of aluminum. Additionally, it demonstrates excellent photothermal de-icing performance, swiftly eliminating thick layers of ice or frost under sunlight. Moreover, this film maintains its anti-icing and hydrophobic qualities even after multiple icing and de-icing cycles, as well as durability testing. It also possesses self-cleaning properties. Given its outstanding performance, this film has tremendous potential for long-term outdoor anti-icing applications.

Thermally-stable solar energy absorber structure with machine learning optimization

Major problems that the world is currently confronting include global warming and the energy crisis, and the optimal absorption of solar spectrum radiation is a pivotal stage for a green future for the effective usage of solar thermal energy. The available solar absorbers are temperature sensitive and do not provide perfect absorption for a wide operation range. The major objectives of the proposed paper are to overcome these limitations and present an ultrawideband thermally stable solar absorber. The developed absorber utilizes a high melting point material comprising a Ti reflector element, a Si3N4 dielectric layer, and a pi-shaped top TiN metal layer. Within the spectral range spanning from 200 to 2500 nm, a notable average absorption rate of 97.69 % is attained. This structure has also demonstrated exceptionally under the AM1.5 conditions with a spectral absorption efficiency of 96 %. This work presents a novel optimization approach for solar absorbers, employing K-nearest neighbor (KNN) regression models to enhance design optimization by simulation time reduction with an R2 score of 0.999. The novelty resides in the absorber surface shape, utilization of cost efficient, sustainable, and thermally stable materials, as well as the KNN regression model for optimization of proposed solar absorber structure. Due to the angle and polarization insensitive characteristics, this structure can be potentially utilized for solar energy harvesting and shielding.

Sound insulation performance of different built-in acoustic materials for new multifamily residential

ABSTRACT The Building Technical Regulations in Taiwan, Article 46–6, Section 1. require that the impact sound insulation performance △LW be greater than 17 dB. Although the regulation has been in effect for over 2.5 years, installations of qualified acoustic materials have not yet been found in the market, as they are not required to be listed for building permit applications until 2021. Owing to the slow increase in new home construction, sound insulation mats are estimated to take five to seven years to be widely adopted. To characterize the material performance, the built-in permanent sound insulation layers of various materials were tested in an unfinished residential building. Practical experiments were conducted as per the CNS 15160-7:2021standard on the 7th floor of new buildings in northern Taiwan. Eleven insulation materials were selected from different manufacturers. The insulation mats made from these materials were placed in the same environment of approximately 10 M2, then incorporated underneath the mortar substrate of the polished floor tile using the wet construction method; the 6th floor of the building was utilized to evaluate sound reduction in accordance with the CNS 8465–2:2019 standard for different materials.

Dielectric Elastomer Actuators with Enhanced Durability by Introducing a Reservoir Layer.

A Dielectric Elastomer Actuator (DEA) consists of electrodes with a dielectric layer between them. By controlling the design of the electrodes, voltage, and frequency, the operating range and speed of the DEA can be adjusted. These DEAs find applications in biomimetic robots, artificial muscles, and similar fields. When voltage is applied to the DEA, the dielectric layer undergoes compression and expansion due to electrostatic forces, which can lead to electrical breakdown. This phenomenon is closely related to the performance and lifespan of the DEA. To enhance stability and improve dielectric properties, a DEA Reservoir layer is introduced. Here, stability refers to the ability of the DEA to perform its functions even as the applied voltage increases. The Reservoir layer delays electrical breakdown and enhances stability due to its enhanced thickness. The proposed DEA in this paper is composed of a Reservoir layer and electrode layer. The Reservoir layer is placed between the electrode layers and is independently configured, not subjected to applied voltage like the electrode layers. The performance of the DEA was evaluated by varying the number of polymer layers in the Reservoir and electrode designs. Introducing the Reservoir layer improved the dielectric properties of the DEA and delayed electrical breakdown. Increasing the dielectric constant through the DEA Reservoir can enhance output characteristics in response to electrical signals. This approach can be utilized in various applications in wearable devices, artificial muscles, and other fields.

The design of the insulation layer and energy consumption optimization of the injection mould for the motor commutator

The injection molding of the motor commutator requires a long-term high-temperature operation, which poses a problem of high energy consumption. The heating zone is located behind the mold, and there is thermal radiation and convection during heating, resulting in uneven temperature distribution. To solve the above problems, an automatic lifting and insulation mechanism is proposed. An insulation frame is built with an aerogel insulation layer inside. It is connected up to the upper table of the machine, moving up and down during processing, and connected down to the crank slider mechanism. Simulation software analyzes its insulation and temperature distribution and, through experimental verification, compares the temperature distribution and energy consumption of injection molds before and after the installation of insulation mechanisms. The experimental and simulation results show that using the automatic lifting insulation layer design scheme can effectively reduce energy consumption, improve temperature distribution unevenness, and increase the yield rate.