Dielectric Films Research Articles

Polarization Manipulated Transmissive Structural Color Based on Dual Complementary Nanograting Cavities

Abstract2D structural color metasurfaces have emerged as an ideal and sustainable alternative to chemical dyes due to their stability and environment‐friendly attributes. In this study, a polarization‐manipulated transmissive structural color based on dual complementary nanograting cavities (DC‐NGC) is proposed and experimentally validated. The DC‐NGC structure is implemented with Ag‐covered dielectric nano gratings sitting on a substrate with a thin dielectric and metallic film. It is found that not only strong polarization dependent and wavelength selective transmission occurs in the structure, but also an additional selective absorption under transverse magnetic (TM) incidence for high‐order transmission associated with the inherent multiple nanocavity resonant modes. These features make both high design flexibility and a rich color palette with a narrow linewidth possible. Experimental demonstrations are performed by validating the polarization‐dependent and wavelength‐selective behaviors, fabricating a color palette with varying structural parameters and three different vibrant and colorful patterns showcasing diverse colors under different polarization states. The proposed dual‐nanograting‐cavity color filter with versatile polarization colors and superior color purity holds significant potential in various applications, including full‐color filtering, display, and micro‐pattern anti‐counterfeiting.

Laser-induced damage thresholds in SiO2-coated aluminum mirrors under various ultrashort pulse widths

The influence of laser temporal parameters on the laser-induced damage threshold (LIDT) is particularly complex due to the variation and uncertainty in damage mechanisms associated with different pulse widths, especially in the range that bridges transitional damage mechanisms. Metallic mirrors are ideally suited for ultrashort pulse optical systems owing to their broad spectral range. A comprehensive understanding of the damage behavior of metallic mirrors under ultrashort pulse widths is crucial for optimizing their performance and manufacturing processes. Consequently, a laser damage testing platform was established in the laboratory to conduct 1-on-1 and area-based damage testing method on SiO2-coated aluminum mirrors, covering a pulse width range of 0.2 to 11 ps. The experimental results revealed two transitions in the LIDT from 0.2 to 11 ps. Specifically, within the 0.3 to 8 ps pulse width range, the LIDT inversely correlated with the pulse width, adhering to a power-law relationship. Conversely, for pulse widths below 0.3 ps and between 8 and 11 ps, the LIDT positively correlated with the pulse width. Observations using optical microscopy and scanning electron microscopy (SEM) exhibited the damage morphology at different pulse widths, which indicated that damage initially occurred in the SiO2 dielectric film on the sample surface, demonstrating a transition in the laser damage mechanism across the experimental pulse width range.

A polypropylene-based all-organic dielectric polymer film with high dielectric constant, low dielectric loss, and high breakdown strength

A polypropylene-based all-organic dielectric polymer film with high dielectric constant, low dielectric loss, and high breakdown strength

Effect of Temperature on Condensed State Structure and Conductivity Characteristics of Micron-Level Biaxially Oriented Polypropylene Films.

Polymer-based dielectric films are increasingly demanded for devices under high electric fields used in new energy vehicles, photovoltaic grid connections, oil and gas exploration, and aerospace. However, leakage current is one of the significant factors limiting the improvement of the insulation performance. This paper tested the leakage current and condensed state structure characteristics of biaxially oriented polypropylene (BOPP) films and obtained the nonlinear characteristics of leakage current of BOPP films in the range of 40-440 V/μm and 40-110 °C. The conduction mechanisms of BOPP films are hopping conductivity within 40-120 V/μm and the Poole-Frenkel effect within 120-440 V/μm, and the threshold electric field of the two kinds conduction mechanisms decreases from 120 to 80 V/μm above 70 °C. The in situ FTIR results indicate that the structure of the BOPP films including band structure, amorphous phase, and isotacticity indices changes above 70 °C, corresponding to the threshold electric field of both conductivity mechanisms gradually decreasing from 120 to 80 V/μm at 70 °C. This study can provide guidance for the optimization design to suppress the leakage current of BOPP and improve its insulation performance.

Ultrahigh Energy Density in All‐Organic Composites Synergistically Tailored by PMMA and Molecular Semiconductor

AbstractThe inherent limitations (particularly low discharged energy density, Ud ≈2 J∙cm−3) of commercially available biaxially‐oriented polypropylene (BOPP) film capacitors significantly restrict their broader application in advanced energy storage systems. This study presents a novel approach to overcome this limitation through the development of all‐organic dielectric composite films. A ternary polymer blend matrix, comprising poly(methyl methacrylate) (PMMA), poly(vinylidene fluoride) (PVDF), and poly(vinylidene fluoride‐hexafluoropropylene) (P(VDF‐HFP)), is employed, with the incorporation of 1,4,5,8‐naphthalenetetracarboxylic dianhydride (NTCDA) molecular semiconductors as nanofillers. Systematic investigation reveals that controlled modulation of the PMMA content within the blend matrix effectively suppresss leakage current by reducing crystallinity, minimizing crystallite size, and stabilizing the γ‐phase in the ferroelectric polymer matrix. Simultaneously, the introduction of NTCDA nanofillers create a high density of deep electron traps, thereby impeding charge injection and enhancing charge carrier trapping within the composite film. The optimized composite film, incorporating 0.5 vol.% NTCDA and 40 wt.% PMMA within the PVDF/P(VDF‐HFP) matrix, demonstrates a substantial enhancement in both breakdown strength (Eb) of 1054 MV∙m−1 and Ud of 28.10 J∙cm−3, representing a considerable improvement over conventional BOPP‐based capacitor. These findings offer a promising strategy for the design and fabrication of high‐performance all‐organic dielectric composite films for next‐generation energy storage applications.

Interfacial modulation and optimization of the electrical properties of ZrGdO x composite films prepared using a UVO-assisted sol-gel method.

In this paper, Gd-doped ZrO2 gate dielectric films and metal-oxide-semiconductor (MOS) capacitors structured as Al/ZrGdO x /Si were prepared using an ultraviolet ozone (UVO)-assisted sol-gel method. The effects of heat treatment temperature on the microstructure, chemical bonding state, optical properties, surface morphology and electrical characteristics of the ZrGdO x composite films and MOS capacitors were systematically investigated. The crystalline phase of the ZrGdO x films appeared only at 600 °C, indicating that Gd doping effectively inhibits the crystallization of ZrO2 films. Meanwhile, as the heat treatment temperature increased from 300 °C to 600 °C, the content of oxygen vacancies decreased from 18.57% to 11.95%, and the content of metal-hydroxyl-oxygen bonds decreased from 14.72% to 8.64%. Heat treatment temperature proved to be effective in passivating the oxygen defects and reducing the trap density within the dielectric layer. At 500 °C, the MOS capacitor exhibited the best electrical characteristics, including the highest dielectric constant (k = 19.3), the smallest hysteresis (ΔV fb = 0.01 V), the lowest boundary trapping oxide charge density (N bt = 2.7 × 1010 cm-2), and the lowest leakage current density (J = 9.61 × 10-6 A cm-2). Therefore, adjusting the heat treatment temperature can significantly improve the performance of ZrGdO x composite films and capacitors, which is favorable for the application of CMOS devices in large-scale and high-performance electronic systems.

Nonclassical Optical Response of Particle Plasmons With Quantum‐Informed Local Optics

AbstractAs the dimensions of plasmonic structures or the field confinement length approach the mean free path of electrons, mesoscopic optical response effects, including nonlocality, electron spill‐in or spill‐out, and Landau damping, are expected to become observable. In this work, a quantum‐informed local analogue model (QILAM) that maps these nonclassical optical responses onto a local dielectric film is presented. The primary advantage of this model lies in its compatibility with the highly efficient boundary element method (BEM), which includes retardation effects with relatively large particle sizes. Furthermore, the approach offers a unified framework that connects two important semiclassical theories: the generalized nonlocal optical response (GNOR) theory and the Feibelman d‐parameters formalism. It is envisioned that QILAM can evolve into a multiscale electrodynamic tool for exploring nonclassical optical responses in diverse plasmonic structures in the future. This can be achieved by directly translating mesoscopic effects into observable phenomena, such as plasmon resonance energy shifts and linewidth broadening in the scattering spectrum.

Enhanced Dielectric Performance in PVDF-Based Composites by Introducing a Transition Interface.

Polymeric dielectrics have garnered significant interest worldwide due to their excellent comprehensive performance. However, developing polymeric dielectric films with high permittivity (εr) and breakdown strength (Eb) and low dielectric loss (tanδ) presents a huge challenge. In this study, amorphous aluminum oxide (Al2O3, AO) transition interfaces with nanoscale thickness were constructed between titanium oxide (TiO2, TO) nanosheets and polyvinylidene fluoride (PVDF) to manufacture composites (PVDF/TO@AO). TO@AO nanosheets showed favorable dispersion in the polymer-based composites. Improved permittivity, suppressed dielectric loss, and enhanced breakdown strength were achieved by introducing AO coating with intermediate permittivity onto TO nanosheets to build a transition interface. The transition interface efficiently depressed the mobility of the charge carrier and electric conduction of the PVDF/TO@AO composites. As a result, the PVDF-based composite with 1 wt% TO@AO showed superior comprehensive performance, including high εr of ~12.7, low tanδ of ~0.017, and exceptional Eb of ~357 kV/mm. This strategy supplies a novel paradigm for the application of fabricating dielectric films with excellent comprehensive performance.

Anomalous Hall effects in magnetic weak topological insulator films

Anomalous Hall effects in magnetic weak topological insulator films

Post-Treatment of Monolayer MoS2 Field-Effect Transistors with H2O Vapor: Alleviation of Remote Channel Doping.

Atomic layer deposition (ALD) of high-k dielectric films on MoS2 channels can lead to inadvertent remote electron doping of channels owing to nonequilibrium ALD conditions, such as the low temperatures and short purge times required for pinhole-free coating, as well as the weak physical adsorption of ALD precursors on MoS2. In this study, we propose the application of a simple and effective H2O vapor post-treatment (H2O PT) at 100 °C immediately after complete integration of bottom- and top-gate monolayer MoS2 field-effect transistors (FETs), to address the inadvertent channel doping effect. When H2O PT was applied to bottom-gate monolayer MoS2 FETs with an ALD-Al2O3 passivation layer, the mitigation of channel doping was confirmed through electrical and optical measurements. Chemical analyses indicated that H2O PT alleviated the remote doping effect by reducing the number of C/H impurities and possible oxygen defects near the ALD-Al2O3/MoS2 interface. These impurities and defects were associated with the incomplete reaction of the ALD precursor due to the nonequilibrium ALD used for the complete coating of Al2O3 on MoS2. Applying H2O PT to top-gate monolayer MoS2 FET arrays significantly narrowed the distributions of the threshold voltage and subthreshold swing. Moreover, it reduced the gate dielectric leakage current induced by the dielectric damage incurred during physical vapor deposition of the gate electrode. Finally, the time-dependent stability of top-gate monolayer MoS2 FETs subjected to H2O PT was confirmed for at least two months in air.

High-performance biodegradable dielectric composite: Towards minimizing electronic waste

Polymer-based dielectric capacitors are crucial in modern electronics due to their wide capacitance range, high operating voltage, lightweight nature, and graceful failure reliability. However, the predominant use of nondegradable dielectric polymers raises environmental concerns. This study addresses this issue by preparing flexible biodegradable dielectric composite films of poly(butylene adipate-co-terephthalate) (PBAT) incorporating varying amounts of nitrogen-doped and non-doped biochar derived from banana peel waste. It was found that the incorporation of biochar in the nanocomposite improved various properties such as dielectric properties, biodegradability, mechanical strength, and thermal stability. The PBAT nanocomposite with 10 wt% N-doped biochar exhibited an 83 % rise in dielectric constant compared to pure PBAT while maintaining a low dielectric loss of 0.071 at 1000 Hz. This approach offers a cost-effective and environmentally sustainable method, showing potential for advancing next-generation disposable electronic materials with enhanced performance attributes.

In-plane aligned doping pattern in electrospun PEI/MBene nanocomposites for high-temperature capacitive energy storage

To achieve superior energy storage performance in dielectric polymer film, it is crucial to balance three key properties: high dielectric constant, high breakdown strength, and low dielectric loss. Here, we...

High-energy density dielectric film capacitors enabled by grain boundary engineering

We demonstrate that the energy storage performance of 0.85BaTiO3-0.15Bi(Mg0.5Zr0.5)O3 films has been significantly enhanced by designing film microstructure, providing a practical avenue for developing high-performance dielectric film capacitors.

One-step fabrication of high energy storage polymer films with a wide bandgap and high melting temperature induced by the fluorine effect for high temperature capacitor applications with ultra-high efficiency.

The development of polymer dielectrics with both high energy density and low energy loss is a formidable challenge in the area of high-temperature dielectric energy storage. To address this challenge, a class of polymers (Parylene F) are designed by alternating fluorinated aromatic rings and vinyl groups in the polymer chain to confine the conjugating sequence and broaden the bandgap with the fluorine effect. The target films with desired thickness, ultra-high purity, and a wide bandgap are facilely fabricated by a one-step chemical vapor deposition (CVD) technique from monomers. The symmetric and bulky aromatic structures exhibit high crystalline performance and excellent stability at high temperature. The presence of strongly electronegative fluorine atoms effectively enhances bandgap and electron trapping capability, which effectively reduces the conduction loss as well as the possibility of breakdown at high temperatures. CVD technology avoids the post-processing film-forming process, ensuring the fabrication of thin films with high quality. These benefits allow Parylene F films to effectively store electrical energy at temperature up to 150 °C, exhibiting a record discharged energy density of 2.92 J cm-3 at charge-discharge efficiency exceeding 90%. This work provides a new idea for the design and synthesis of all-organic polymer dielectric films for high temperature applications.

Energy storage performance and dielectric tunability of AgNbO3 ferroelectric films

AgNbO3 ceramics have attracted significant attention as environmentally friendly energy storage materials; however, their low energy densities limit further development. In this study, a 400- nm AgNbO3 films with a dense microstructure and flat surface is prepared by pulsed laser deposition. The dielectric tenability and hysteresis loops of the film reveal its ferroelectric nature. The dielectric tunability of the AgNbO3 film was 63.6% at 600kV/cm. The breakdown strength reached 1500kV/cm, resulting in a high recoverable energy density of 13.3J/cm3. The recoverable energy storage density of AgNbO3 films indicates good temperature stability with a variation of < 10% between 30 ℃ and 150 ℃ and good frequency stability with a variation of < 10% between 103Hz and 105 Hz. These results suggest that AgNbO3 dielectric films are promising energy storage materials.

Adhesive Temperature-Sensitive Paint Films for Aerodynamic Heating Measurements

Temperature-sensitive paint (TSP) films are developed via application of the TSP to 0.11-mm-thick polyvinyl-chloride films with an adhesive backing. This approach allows the TSP to be quickly replaced on models if surface damage occurs during testing, which is common in impulse facilities used to create hypersonic flow conditions. This work demonstrates that quantitative calibration of the TSP signal is still possible and that only the top coat of TSP is necessary for application to the thermally insulative films, which aids in simplifying heat flux calculations. The TSP film is also compared to infrared thermography of a 20° cone in Mach 7 flow, which demonstrates practical use in an aerodynamic setting. Overall, this approach may yield better calibration capabilities and higher measurement throughput and quality.

Fully printed non-contact touch sensors based on GCN/PDMS composites: enabling over-the-bottom detection, 3D recognition, and wireless transmission

ABSTRACT The rapid advancement in intelligent bionics has elevated electronic skin to a pivotal component in bionic robots, enabling swift responses to diverse external stimuli. Combining wearable touch sensors with IoT technology lays the groundwork for achieving the versatile functionality of electronic skin. However, most current touch sensors rely on capacitive layer deformations induced by pressure, leading to changes in capacitance values. Unfortunately, sensors of this kind often face limitations in practical applications due to their uniform sensing capabilities. This study presents a novel approach by incorporating graphitic carbon nitride (GCN) into polydimethylsiloxane (PDMS) at a low concentration. Surprisingly, this blend of materials with higher dielectric constants yields composite films with lower dielectric constants, contrary to expectations. Unlike traditional capacitive sensors, our non-contact touch sensors exploit electric field interference between the object and the sensor’s edge, with enhanced effects from the low dielectric constant GCN/PDMS film. Consequently, we have fabricated touch sensor grids using an array configuration of dispensing printing techniques, facilitating fast response and ultra-low-limit contact detection with finger-to-device distances ranging from 5 to 100 mm. These sensors exhibit excellent resolution in recognizing 3D object shapes and accurately detecting positional motion. Moreover, they enable real-time monitoring of array data with signal transmission over a 4G network. In summary, our proposed approach for fabricating low dielectric constant thin films, as employed in non-contact touch sensors, opens new avenues for advancing electronic skin technology.

Enhanced and directional fluorescence emission regulated by dual resonant surface modes

Fluorescence emission regulation is of great interest for its promising applications in various fields such as microscopy, chemical analysis, encryption, and sensing. Most studies focus on the regulation of the fluorescence emission process. However, the spectral separation of excitation and emission of fluorophores requires careful design of resonances to cover both emission and excitation wavelengths, which is a better choice to enhance fluorescence intensity. In this Letter, we engineer an efficient dielectric concentric ring grating on a dielectric multilayer film with two resonate modes to enhance the excitation and emission processes. By careful design of the structure, the two resonate modes occupy similar in-plane wave vector and overlap in the fluorescence area. Experimentally, fluorescence intensity enhancement about five times and the divergence of fluorescence into free space compressed to less than 5° are achieved. Our work provides what we believe to be a new strategy for the realization of high directional on-chip light emitter at room temperature.

Gan Vertical Power Finfets Using BN As Gate Dielectric

Over the past few decades, the semiconductor industry has undergone rapid advancements and transformative evolution, particularly in semiconductor materials. Wide bandgap (WBG) semiconductors, represented by gallium nitride (GaN) and silicon carbide (SiC), offer significant advantages over traditional silicon-based technologies. This research explores the suitability of BN as a dielectric material in GaN vertical power FinFETs, specifically targeting high-temperature applications. BN thin films are directly deposited by microwave-plasma-assisted chemical vapor deposition (CVD). The presence of BN is confirmed by X-ray photoelectron spectroscopy (XPS). GaN/BN vertical FinFETs are demonstrated for the first time with a current on-off ratio of 10. The high-resolution transmission electron microscopy (HRTEM) reveals the presence of BN on GaN non-polar sidewalls. BN metal-insulator-semiconductor (MIS) gate diode demonstrates increased breakdown voltage compared to GaN Schottky gate diode. Hydrogen plasma has been pinpointed as the main culprit behind variations in dielectric film thickness and the deterioration of crystal quality, both of which contribute to increased gate leakage current. Through the optimization of deposition conditions, the enhanced device demonstrates outstanding performance and maintains stable operation at temperatures up to 573K. This study provides a valuable foundation for future research on BN-based gate dielectrics in GaN vertical transistors.

Multimodal Loudspeaker Based on a Dielectric Elastomer Roll Actuator

A novel loudspeaker design integrating lightweight and efficient acoustic transducers derived from dielectric elastomer films is presented. This innovation centers on core-free dielectric elastomer roll actuators, functioning akin to artificial muscles, altering shape upon the application of an electric field. The actuators serve two roles: propelling acoustically radiating surfaces and emitting sound themselves. The paper provides a model that describes the axial vibration behavior via electromechanical and acoustic networks, facilitating understanding and comparability with electrodynamic loudspeaker systems without the need for extensive background knowledge of dielectric elastomer technology. Based on established methodologies, the design process and adaptability to diverse applications is evident. A demonstrator developed as a proof of concept with the aim of creating a broadband speaker for speech reproduction was designed, constructed, and examined utilizing the established methodology. It shows promising practicality and, in certain aspects, technological superiority over electrodynamic counterparts. Notable features, such as increased efficiency, significant weight reduction, and wide radiation pattern make this speaker viable and particularly attractive for mobile PA applications such as those found in trains and aircraft. Furthermore, the underlying principle and modeling framework allow the future creation and adaptation to a broad spectrum of applications, promising further innovation in the field.