Dielectric Layer Research Articles

Additively manufactured micro-lattice dielectrics for multiaxial capacitive sensors.

Soft sensors that can perceive multiaxial forces, such as normal and shear, are of interest for dexterous robotic manipulation and monitoring of human performance. Typical planar fabrication techniques have substantial design constraints that often prohibit the creation of functionally compelling and complex architectures. Moreover, they often require multiple-step operations for production. Here, we use an additive manufacturing process based on continuous liquid interface production to create high-resolution (30-micrometer) three-dimensional elastomeric polyurethane lattices for use as dielectric layers in capacitive sensors. We show that the capacitive responses and sensitivities are highly tunable through designs of lattice type, thickness, and material-void volume percentage. Microcomputed tomography and finite element simulation are used to elucidate the influence of lattice design on the deformation mechanism and concomitant sensing behavior. The advantage of three-dimensional printing is exhibited with examples of fully printed representative athletic equipment with integrated sensors.

Recycled plastics based impact noise resilient layer development

Sustainability and the carbon footprint reduction is commonly associated with recycling and secondary use of materials, for example also in the building construction industry. For decades, experts have been dealing with this topic across the entire spectrum of the development of building structures. One of the areas where soft recycled materials find suitable application is the area of building acoustics with a focus on impact noise attenuation. This contribution focuses on resilient layers dedicated for lightweight floating floors. This type of flooring is very often used in the reconstruction of apartments in apartment buildings. There is usually no possibility to realize heavy floating floors or for static reasons or reasons of the structural height of rooms or door openings. The work focuses on the development of floor underlayer mats based on recycled material in several variants. These were experimentally compared with conventional materials used in practice as the so-called impact sound insulation layers under laminate floors in terms of improving the impact noise insulation as well as the dynamic stiffness and the loss factor.

Cleanroom-free fabrication of flexible capacitive pressure sensors using paintable silver electrodes on stationery paper and random microstructured polydimethylsiloxane dielectric layer

Abstract In this work, we propose a facile, low-cost, and cleanroom-free approach for fabricating flexible capacitive pressure sensors based on paintable Ag electrodes on stationery paper substrates (Ag–paper electrodes) and a random microstructured polydimethylsiloxane (PDMS) dielectric layer transferred from emery paper. COMSOL Multiphysics simulations and experimental investigations suggest that the pressure sensor with random microstructured PDMS dielectric layer performs better than the sensor with ordered micropyramidal dielectric layer. The developed Ag–paper electrode and random microstructured PDMS dielectric layer-based pressure sensors are workable in a wide pressure range (up to 630 kPa) and exhibit a high sensitivity of 0.132 kPa−1 up to 1 kPa, low hysteresis (6.6%) with loading–unloading of ∼500 kPa pressure, high stability during a ∼5250 cyclic test, and the ability to sense a low pressure of ∼27 Pa. The developed sensor also successfully transduces arterial pulse wave forms when it is properly attached to the wrist. Using the proposed process, a flexible capacitive pressure sensor matrix of 4 × 4 array is also successfully developed for single- and multiple-point pressure mapping with minimal cross-talk. The proposed sensor process is simple and inexpensive to implement, and offers spatial pressure mapping for e-skin applications.

Enhanced SWIR Absorption in PMMA‐Coated TiN‐Based Metamaterial

AbstractAchieving highly efficient absorption in the short wavelength infrared (SWIR) spectral region is crucial for advancing numerous technologies. SWIR absorption enhances energy harvesting in solar cells, improves the sensitivity of infrared sensors, and enables precise control of thermal radiative properties in thermal emission devices. These advancements are essential for applications such as thermal imaging, night vision, and thermophotovoltaic systems. The study presents a simple, cost‐effective design of a polymer‐coated multilayer perfect absorber (MPA) metamaterial optimized for the SWIR spectral region. The proposed MPA structure is composed of four distinct layers: a top layer made of polymethyl methacrylate (PMMA) polymer, a second layer featuring arrays of circular titanium nitride (TiN) disks, a dielectric middle layer consisting of a pure zinc oxide (ZnO) film, and a bottom metallic layer formed by a thin film of TiN. The results demonstrate that the MPA achieves near‐perfect absorption, with a remarkable 99% efficiency centered at a wavelength of 1.3 µm. The absorption properties are further investigated with respect to various structural parameters to ensure better performance of the absorber. These absorbers hold great promise for applications in energy absorption, infrared sensing, thermal emission, and related fields.

Improving the color gamut of gold nanostructures using vertical tandem nano-disks

Metallic nanoparticles have been used in structural coloration applications since they provide an alternative for the synthesis of color filters, with extended color gamut, enhanced color saturation, and brightness. These optical properties can be further improved when integrating nanoparticles into coupled dimers that give rise to enhanced hybridized plasmon resonances. In this contribution, gold nano-disks are split into Au/SiO2/Au layered structures to enhance its plasmon resonances and evaluate its improved performance as reflective color filters. To do so, the reflectance spectra of the layered disks were obtained with numerical simulations, identifying high amplitude peaks in the visible band and low-amplitude peaks in the near infrared one, related to the hybridized resonances. By choosing the appropriate size of the intermediate dielectric and metallic layers, as well as the near-field coupling, peaks can be tuned along the visible and near infrared bands, respectively. The chromatic coordinates of the addressed nanostructures obtained from the reflectance spectra show that the nanostructures hold color gamut that extends toward magenta, orange, yellowish, and reddish shades of colors.

Wake-Up Free Hf₀.₅Zr₀.₅O₂ Ferroelectric Capacitor by Annealing and Inserting a Top Dielectric Layer

Wake-Up Free Hf₀.₅Zr₀.₅O₂ Ferroelectric Capacitor by Annealing and Inserting a Top Dielectric Layer

Highly Efficient Wide Bandgap Perovskite Solar Cells With Tunneling Junction by Self-Assembled 2D Dielectric Layer.

Reducing non-radiative recombination and addressing band alignment mismatches at interfaces remain major challenges in achieving high-performance wide-bandgap perovskite solar cells. This study proposes the self-organization of a thin two-dimensional (2D) perovskite BA2PbBr4 layer beneath a wide-bandgap three-dimensional (3D) perovskite Cs0.17FA0.83Pb(I0.6Br0.4)3, forming a 2D/3D bilayer structure on a tin oxide (SnO2) layer. This process is driven by interactions between the oxygen vacancies on the SnO2 surface and hydrogen atoms of the n-butylammonium cation, aiding the self-assembly of the BA2PbBr4 2D layer. The 2D perovskite acts as a tunneling layer between SnO2 and the 3D perovskite, neutralizing the energy level mismatch and reducing non-radiative recombination. This results in high power conversion efficiencies of 21.54% and 19.16% for wide-bandgap perovskite solar cells with bandgaps of 1.7 and 1.8 eV, with open-circuit voltages over 1.3 V under 1-Sun illumination. Furthermore, an impressive efficiency of over 43% is achieved under indoor conditions, specifically under 200 lux white light-emitting diode light, yielding an output voltage exceeding 1 V. The device also demonstrates enhanced stability, lasting up to 1,200 hours.

Two-layered optimized metamaterial antenna with high gain and wide bandwidth for 5G mm-Wave applications

A two-layered high gain and wide bandwidth metamaterial antenna working at 29 GHz for mm-Wave applications is proposed in this paper. The metamaterial antenna has an overall compact size of 12.5 x 12.5 x 7.28 mm3. It is realized with a Rogers Duroid 5880 dielectric layer 0.78 mm thick used as substrate and a Rogers RO3010 dielectric layer 1.5 mm thick at distance 5 mm above the radiation element. The radiation element is composed of a square-cut-at-the-four-corners, patch antenna with probe pin feeding. In addition, for further antenna performance enhancement, negative refractive index printed metamaterials surround the patch antenna offering bandwidth and gain enhancement. Simulated results show a significantly wide bandwidth of 7.91 GHz ranging from 26.04 GHz to 33.95 GHz and a high peak realized gain of 12.2 dB. These features make the antenna a good candidate for 5G mm-Wave applications.

Fabrication of Electrospun Porous TiO2 Dielectric Film in a Ti–TiO2–Si Heterostructure for Metal–Insulator–Semiconductor Capacitors

The development of metal–insulator–semiconductor (MIS) capacitors requires device miniaturization and excellent electrical properties. Traditional SiO2 gate dielectrics have reached their physical limits. In this context, high-k materials such as TiO2 are emerging as promising alternatives to SiO2. However, the deposition of dielectric layers in MIS capacitors typically requires high-vacuum equipment and challenging processing conditions. Therefore, in this study, we present a new method to effectively fabricate a poly(vinylidene fluoride) (PVDF)-based TiO2 dielectric layer via electrospinning. Nano-microscale layers were formed via electrospinning by applying a high voltage to a polymer solution, and electrical properties were analyzed as a function of the TiO2 crystalline phase and residual amount of PVDF at different annealing temperatures. Improved electrical properties were observed with increasing TiO2 anatase content, and the residual amount of PVDF decreased with increasing annealing temperature. The sample annealed at 600 °C showed a lower leakage current than those annealed at 300 and 450 °C, with a leakage current density of 7.5 × 10−13 A/cm2 when Vg = 0 V. Thus, electrospinning-based coating is a cost-effective method to fabricate dielectric thin films. Further studies will show that it is flexible and dielectric tunable, thus contributing to improve the performance of next-generation electronic devices.

Combined design of dielectric material and layer structure of vanadium nitride/graphene composites for ultra-broadband microwave absorption

Combined design of dielectric material and layer structure of vanadium nitride/graphene composites for ultra-broadband microwave absorption

Design and investigation of indium tin oxide-based transparent broadband microwave absorbers

This paper presents the design of a novel wideband transparent microwave absorber based on indium tin oxide (ITO). The absorber adopts a multilayer structure, with the top layer composed of a nested square structure made of ITO material, an intermediate dielectric layer of polyvinyl chloride (PVC), and a bottom layer of polyethylene terephthalate (PET) coated with ITO as the reflector. By optimizing structural parameters such as the thickness of the ITO film and the dimensions of the spacer layer, efficient broadband microwave absorption exceeding 90% is achieved within the frequency range of 2.43 to 5.67 GHz, while simultaneously meeting requirements for optical transparency and broadband performance. Simulation experiments and theoretical analyses demonstrate excellent polarization and incident angle stability of the absorber structure. Finally, samples are fabricated using screen printing technology, and free-space testing results are consistent with simulation predictions, validating the feasibility of the design.

2D Reconfigurable Memtransistor for High‐Performance Dual‐Mode Memory and Broadband Photodetection

AbstractDeveloping multifunctional nanoelectronics will facilitate simplifying the circuits for future high‐integrated system. CuInP2S6 (CIPS) exhibiting ferroionic phenomena allows the manipulation of polarization and conductive behaviors. Here, a MoS2 transistor is fabricated with CIPS gate dielectric layer to realize the functions of nonvolatile memory, broadband photodetector and voltage comparator. It exhibited convex‐shaped anti‐ambipolar transfer characteristics, with a sharp boundary as the n‐/p‐type conductance conversion line, guiding the precise modulation of its working modes by tuning voltage. The CIPS works as a ferroelectric insulator to support the n‐type transistor, while as a semiconductor dominated by Cu+ migration to reconfigure a p‐type memristive transistor. It owns hysteresis behavior in both modes, demonstrating the n‐ and p‐type memory windows synchronously. Also, it exhibits the nonvolatile memory property with low energy‐consumption of 4 pJ per bite, good endurance of 2567 write‐erase cycles, and good retention with a high current on/off ratio of 2 × 103 over 104 s without any obvious decay. Moreover, it extends the photodetection from visible to near‐infrared with the responsivity of 321 AW−1 at 1200 nm wavelength. This work provides an effective strategy for the realization of multiple functions by specific materials and devices.

Multiphase soft metal enabled high-performance fabric-based wearable energy harvesting

Highly efficient and flexible power sources have always been the focus and goal in the field of wearable electronics. However, the existing wearable power sources are limited by their large size, high weight, electrolyte leakage, and poor mechanical compliance, which seriously hinders their practical applications. Herein, we propose a novel strategy to achieve and demonstrate a fabric-based high-performance wearable triboelectric nanogenerator (TENG) structure. The metals of gallium (Ga), bismuth (Bi), indium (In), and tin (Sn) are mixed according to specific mass ratios, and then they are transformed in liquid phase to form room-temperature multiphase soft metals of GaBiInSn. The material exhibits both metallic and fluidic properties, and possesses a characteristic of multiphase structure. The GaBiInSn material is directly deposited between polytetrafluoroethylene (PTFE) layers and nonwoven fabrics to establish multi-level conductive and frictional interfaces, creating charge transfer and solid-liquid hybrid dielectric layers. Therefore, the thin film-type triboelectric nanogenerators with a structure of PTFE/GaBiInSn/nonwoven fabric (LM-P-TENGs) is manufactured. The LM-P-TENGs can be integrated onto fabrics without compromising their breathability, comfortableness, and flexibility. Particularly, LM-P-TENGs efficiently convert the mechanical energy of human limb movements into sustainable electrical energy output. Under the human limb mechanical triggering conditions, LM-P-TENG achieves a champion specific open-circuit voltage up to 900 V, peak short-circuit current density of 43.3 mA/m2, and high power density of 12.56 W/m2. This work demonstrates the application potential of room-temperature multiphase soft materials in flexible wearable power sources, while introducing a novel power supply mode for wearable electronics. Additionally, the LM-P-TENGs also present applications in self-powered wearables, medical biosensing systems, human-machine interaction systems, near-eye display systems, etc. for the flexible electronics.

Multi-Frequency Asymmetric Absorption-Transmission Metastructures-Photonic Crystals and Their Application as a Refractive Index Sensor.

In this paper, a kind of metastructure-photonic crystal (MPC) with multi-frequency asymmetric absorption-transmission properties is proposed. It is composed of various dielectric layers arranged in a periodically tilting pattern. When electromagnetic waves (EMWs) enter from the opposite direction, MPC shows an obvious asymmetry. EMWs are absorbed at 13.71 GHz, 14.37 GHz, and 17.10 GHz in forward incidence, with maximum absorptions of 0.919, 0.917, and 0.956, respectively. In the case of backward incidence, transmission above 0.877 is achieved. Additionally, the MPC is utilized for refractive index (RI) sensing, allowing for wide RI range detection. The refractive index unit is denoted as RIU. The RI detection range is 1.4~3.0, with the corresponding absorption peak variation range being 17.054~17.194 GHz, and a sensitivity of 86 MHz/RIU. By adjusting the number of MPC cycles and tilt angle, the sensing performance and operating frequency band can be tailored to meet various operational requirements. This MPC-based RI sensor is simple to fabricate and has the potential to be used in the development of high-performance and compact sensing devices.

An organic-inorganic dual network built in fast-growing wood veneers to improve the flame retardant and mechanical properties of plywood

Fast-growing wood is widely used in plywood production due to its short growth cycle and low cost. However, its loose fiber structure, inferior material quality, and high flammability significantly limit the application range of plywood products and hinder high-value utilization. This paper reports a simple method for modifying fast-growing wood veneers. We modified phenolic resin with Mg(OH)₂@nano-silica composite particles and impregnated it into the veneers, constructing an organic-inorganic hybrid dual-network structure on both the surface and interior of the veneers. The plywood prepared from the modified veneers exhibited a bending strength of 115.6 MPa, a modulus of elasticity of 9.7 GPa, and a wet shear strength of 2.1 MPa, representing increases of 86.1 %, 47.0 %, and 90.9 %, respectively, compared to plywood made from unmodified veneers. Additionally, the peak heat release rate decreased by 15.3 %, and the ignition time was extended to 26 s. The uniformly distributed inorganic network effectively mitigated stress concentration and, together with the phenolic resin, formed an efficient thermal insulation layer, enhancing the flame retardancy of the material. This study offers a simple and effective treatment method for reinforcing fast-growing wood veneers, promoting the use of fast-growing wood in high-performance applications.

Enforcing interface field continuity to advance finite element approximations in heterogeneous materials

To investigate the discrete field continuity at the interface of inhomogeneous materials, this paper investigates the scattering of electromagnetic waves interacting with a perfect electrical conductor object coated with dielectric materials, employing the finite element method. In the derivation process of the variational formulation, the tangential continuity of electric fields eliminates any discrepancies occurring along the internal interfaces. However, while it is important to maintain tangential continuity of electric and magnetic fields at the interface between different dielectrics, this requirement is not met precisely within discrete space. As a result, approximations can exhibit inaccuracies and potentially fail to fully capture the underlying physical phenomena. To alleviate these issues, we propose an imposition of tangential continuity of the magnetic field within the minimizing functional, thereby ensuring adherence to interface conditions between two dielectric layers. This approach can be naturally applied to a variety of interface problems to enhance the approximation accuracy of interaction models in real-world environments.

Study on the mechanism of advanced pre-degradation on hydrogenation of multi-crystalline silicon solar cells

The electrical performance of monocrystalline silicon solar cells was significantly improved under hydrogenation alone with appropriate conditions, while the similar improvements of multi-crystalline silicon (mc-Si) solar cells were relatively slight. In this paper, an advanced pre-degradation (Adv.Pre-Deg) was introduced to improve the hydrogenation effect and enhance the performance of mc-Si solar cells. Meanwhile, further studies were conducted on the influence mechanism of Adv.Pre-Deg on subsequent hydrogenation, and some microscopic detection was applied to characterize the effect of Adv.Pre-Deg on the following hydrogenation. The results indicated that Adv.Pre-Deg only slightly influenced the crystallinity, dangling bonds, and defects within the surface dielectric layer, which illustrated that Adv.Pre-Deg hardly harmed the dielectric layer. Then, Raman imaging demonstrated that Adv.Pre-Deg displayed primary assistance in stimulating impurities or defects in silicon bulk in advance. According to the detection of the Si-H bond, we also concluded that the effective performance improvement on mc-Si silicon solar cells through Adv.Pre-Deg & hydrogenation was due to the pre-activation of impurities or defects by Adv.Pre-Deg. Moreover, Adv.Pre-Deg enhanced the passivation effect of hydrogenation on interstitial Fei+ from 30.3%rel. to 89.1%rel. and dislocation defects from 21.92%rel. to 46.18%rel., doubling the improvement of bulk passivation on mc-Si. Therefore, the method of combining Adv.Pre-Deg with hydrogenation aims to be applied to other types of solar cells and focus on improving performance and suppressing various degradations, such as TOPCon and HJT.

Ternary TiO2/MoS2/ZnO hetero-nanostructure based multifunctional sensing devices

Novel sensing applications benefit from multifunctional nanomaterials responsive to various external stimuli such as mechanics, electricity, light, humidity, or pollution. While few such materials occur naturally, the careful design of synergized nanomaterials unifies the cross-coupled properties which are weak or absent in single-phase materials. In this study, 2D MoS2 integrated with ultrathin dielectric oxide layers forms hetero-nanostructures with significant impacts on carrier transport. The ternary TiO2/MoS2/ZnO hetero-nanostructures, along with their individual properties, improve the performance of multifunctional sensing devices. The synthesized hetero-nanostructure exhibits a responsivity of up to 16 mA/W to 700 nm light and responds to 5 ppm ammonia gas at room temperature. These enhancements are attributed to interface charge transfer and photogating effects. The ternary TiO2/MoS2/ZnO hetero-nanostructure is compatible with existing semiconductor fabrication technologies, making it feasible to integrate into flexible, lightweight semiconductor devices and circuits. These results may inspire new photodetectors and sensing devices based on two-dimensional (2D) layered materials for IoT applications.

Tunable Plasmon Resonance in Silver Nanodisk-on-Mirror Structures and Scattering Enhancement by Annealing.

In this study, we evaluated the surface plasmon characteristics of periodic silver nanodisk structures fabricated on a dielectric thin-film spacer layer on a Ag mirror substrate (NanoDisk on Mirror: NDoM) through finite difference time domain (FDTD) simulations and experiments involving actual sample fabrication. Through FDTD simulations, it was confirmed that the NDoM structure exhibits two sharp peaks in the visible range, and by adjusting the thickness of the spacer layer and the size of the nanodisk structure, sharp peaks can be obtained across the entire visible range. Additionally, we fabricated the NDoM structure using electron beam lithography (EBL) and experimentally confirmed that the obtained peaks matched the simulation results. Furthermore, we discovered that applying annealing at an appropriate temperature to the fabricated structure enables the adjustment of the resonance peak wavelength and enhances the scattering intensity by approximately five times. This enhancement is believed to result from changes in the shape and size of the nanodisk structure, as well as a reduction in grain boundaries in the metal crystal due to annealing. These results have the potential to contribute to technological advancements in various application fields, such as optical sensing and emission enhancement.

Analysis of Thermal Properties of Materials Used to Insulate External Walls.

This article emphasizes the significance of understanding the actual thermal properties of thermal insulation materials, which are crucial for avoiding errors in building design and estimating heat losses within the energy balance. The aim of this study was to analyse the thermal parameters of selected thermal insulation materials, particularly in the context of their stability after a period of storage under specific conditions. The materials chosen for this study include commonly used construction insulations such as polystyrene and mineral wool, as well as modern options like rigid foam composites. Experimental studies were conducted, including the determination of the thermal conductivity coefficient λ, as well as numerical analyses and analytical calculations of heat flow through a double-layer external wall with a window. The numerical analyses were performed using the TRISCO software version 12.0w, based on the finite element method (FEM). A macrostructural analysis of the investigated materials was also performed. The findings indicated that improper storage conditions adversely affect the thermal properties of insulation materials. Specifically, storing materials outdoors led to a deterioration in insulating properties, with an average reduction of about 4% for the standard materials and as much as 19% for the tested composite material. Insufficient understanding of the true thermal properties of insulation materials can result in incorrect insulation layer thickness, degrading the fundamental thermal parameters of external walls. This, in turn, increases heat loss through major building surfaces, raises heating costs, and indirectly contributes to greenhouse gas emissions.