Dielectric Effect Research Articles

Construction of the N, S co-doped C/FeS2 materials for low thickness and high-efficiency microwave absorption

Research into electromagnetic wave-absorbing materials is essential to tackle the growing impact of electromagnetic wave pollution on human health and social advancement. Therefore, a method for synthesizing N,S co-doped C/FeS2 porous carbon composite absorbers (N,S@APCs) with low thickness, low filler content, and high performance is reported. The porous carbon structures were prepared by a high-temperature-hydrothermal two-step method using directly liquefied coal pitch as the carbon source. The successful doping of diatomic N and S at optimal concentrations enhances their impedance matching capacity. At the same time, forming FeS2 through the reaction between S and Fe3+ in the raw material efficiently improves the dielectric loss effect and enhances interfacial and dipole polarization effects. These factors together contribute to the strong absorption performance and low matching thickness of the fabricated N, S@APCs. At a thickness of 1.5 mm, 10 wt% of absorber filling resulted in a strong absorption performance with RLmin=-51.05 dB. Meanwhile, at a thickness of 1.7 mm, an effective absorption bandwidth of 4.76 GHz was achieved. This research offers a novel viewpoint on investigating porous carbon absorbers at low thicknesses. It serves as a reference for later investigations into polyatomic co-doped porous carbon absorbers.

Modeling and solving for vibration and buckling of circular functionally graded dielectric plates reinforced by graphene platelets considering complex conditions

The vibration and bucking behaviors of circular functionally graded (FG) dielectric plates reinforced by graphene platelets (GPL) under external electric fields are studied at the presence of many complex factors such as dielectric effect, pre-stress, gradient slope, imperfect bonding between GPL and matrix material, interface electron tunneling and Maxwell–Wagner-Sillars (MWS) polarization. Based on the effective medium theory and linear rule of mixtures, material properties of the GPL reinforced composites (GPLRC) are calculated. Dynamic differential equations of the circular FG-GPLRC dielectric plates are numerically solved by the differential quadrature method, and natural frequencies and critical loads are obtained. Trans-scale analyses for the influences of the volume fraction, geometric size, gradient distributed pattern and gradient slope on the percolation threshold, permittivity and the vibration or buckling characteristics are provided. Furthermore, variations of the natural frequencies and critical loads with electric field parameters, the pre-stress and thickness of the interphase layer are also discussed. Results show that the natural frequencies and critical loads of the plates can be changed artificially and effectively by adjusting the external electric field, pre-stress and the parameters of GPL. The larger the diameter to thickness ratio of GPL, the bigger the equivalent permittivity and the smaller the percolation threshold. When the volume fractions of GPL are less than the threshold, the mechanical properties dominate the vibration and buckling. However, when the volume fractions are bigger than the threshold, the electrical properties have significant influences. Therefore, higher macro mechanical properties can be obtained by changing the microstructure of the materials.

Harnessing Conformational Disorder of Organic Cations for Efficient Blue Quasi‐2D Perovskite LEDs

AbstractDespite quasi‐2D perovskite offering great control over the optoelectronic properties, disordered organic cations are often perceived as detrimental to device performance, primarily affecting charge carrier mobility. However, it is proposed that such disordered organic cations‐enabled excellent excitonic properties can be beneficial for fabricating high‐efficiency perovskite light‐emitting diodes (PeLEDs) facilitated by reduced dielectric screening effect. Here, by incorporating acetamidinium bromide additives, the conformational disorder of organic cation is precisely manipulated and meticulously probed using sum frequency generation vibrational spectroscopy. Finally, a distinctive inverse relationship is elucidated between the degree of conformational order, characterized as relative structure ordering , and key performance metrics such as photoluminescence quantum yield and external quantum efficiency (EQE). By optimizing the configurational disorder, sky‐blue (485 nm) PeLEDs achieve a noteworthy EQE of 14.42% and exhibit significantly prolonged operational stability in open‐air conditions. This finding underscores the potential advantages of disordered organic cations in enhancing exciton properties and radiative recombination efficiency.

Design and Analyze the Effect of Hetero Material and Dielectric on TFET with Dual Work Function Engineering

Background: As the size of the field effect transistors is reduced down to nanometers, the performance of the devices is affected by various short-channel effects. To overcome these effects, various novel devices are used. Tunnel Field Effect Transistors (TFET) are novel devices in which the drain current needs to be improved. Gate engineering and III-V compound materials are proposed to improve the ON current and reduce the leakage current along with its ambipolar behaviour. Methods: The proposed device structure is designed with a heterojunction hetero dielectric dual material gate Tunnel Field Effect Transistor incorporating various combinations of III-V compound materials such as AlGaAsSb/InGaAs, InGaAs/Ge, InGaAs/InP and SiGe/Si. As in III-V composite materials like AlGaAsSb/InGaAs, the narrower bandgap at the source channel interface helps to improve the electric field across the junction. At the same time, the wider bandgap at the channel drain junction leads to unidirectional current flow, resulting in ambipolar reduction. 2D TCAD simulation is used to obtain the electrical parameters for Hetero junction TFETs and the comparison analysis of different Hetero device structures. Results: The device's electrical parameters, such as energy band diagram, current density, electric field, drain current, gate capacitance and transconductance, have been simulated and analyzed. Besides, the dual material used in the gate, such as Metal1 (M1) and Metal2 (M2), along with HfO2/SiO2 stacked dielectric, helps improve the gate controllability over the channel and the leakage current reduction. Conclusion: An ION=10-1A/μm, IOFF = 10-12A/μm at drive voltage 0.5V is obtained for InGaAs/InP layer at the source channel hetero junction TFET, and ION=10-2A/μm, IOFF =10-14A/μm at drive voltage 0.5V is obtained for SiGe/Si layer at the source channel hetero junction TFET. Therefore, the InGaAs/InP and SiGe/Si layer TFET are more suitable for ultra-low power integrated circuits.

Negative Capacitance and Dielectric Constant of Nanocomposite SiAlzOxNy(Si) Films with Semiconductor Nanoparticles.

The electrical properties of nanocomposite SiAlzOxNy(Si) films containing Si nanoclusters embedded into amorphous SiAlzOxNy matrix have been studied by measurements of DC current-voltage and AC capacitance-voltage characteristics. Analysis of the results allowed us to conclude the existence of a negative dielectric constant. The temperature dependence of the negative dielectric constant has been obtained and analyzed. The negative capacitance has been revealed during measurements of capacitance-voltage characteristics at testing signal frequency of 2 kHz. The negative capacitance also points out the appearance of a negative dielectric constant effect. The qualitative model for explanation of negative dielectric constant based on peculiarities of SiAlzOxNy(Si) films polarization due to electron capture at Si nanoparticles-amorphous SiAlzOxNy matrix interface traps near cathode region has been proposed. In the case of AC C-U measurements, a negative capacitance is observed if conductivity current through the nanocomposite film is relatively high.

Response of helielectric nematics under an in-plane electric field.

In traditional chiral nematic liquid crystals, the apolar cholesterics, the dielectric effect is the main driving force for responding to an electric field. The emerging polar chiral nematics, dubbed helielectric nematics, are the polar counterparts of the cholesterics. The head-to-tail symmetry breaking of the new matter state enables it to respond sensitively to the polarity of an electric field. Here, we report on the observation of a sequential polar winding/unwinding process of polarization helices under an electric field applied perpendicular to the helical axes, which behaves distinctly from the unwinding of the apolar cholesteric helices. Understanding the helix-unwinding behaviors provides insights for developing switchable devices based on helielectric nematics.

Modulation of Auger recombination via facet engineering in CsPbBr3 perovskite nanocrystals

We demonstrate the modulation of Auger recombination via facet engineering in CsPbBr3 perovskite nanocrystals, where the static dielectric screening effect is revealed to prevail over the dynamic polaronic screening effect.

Enhanced X and Ku band microwave absorption powered by a magnetic–dielectric synergistic effect in Pr-doped M/W composite hexaferrites

Pr-doped M/W composite hexaferrites exhibit satisfactory microwave absorption performance due to high magnetic loss and dielectric loss caused by strong resonance interaction and multiple polarization mechanisms.

Improving the Born equation: Origin of the Born radius and introducing dielectric saturation effects

Improving the Born equation: Origin of the Born radius and introducing dielectric saturation effects

Achieving Ultrahigh DC-Power Triboelectric Nanogenerators by Lightning Rod-Inspired Field Emission Modeling.

Direct current triboelectric nanogenerators (DC-TENGs) are a groundbreaking technology to capture micromechanical energy from the natural environment, which is crucial for directly powering sensor networks. However, the research bottleneck in enhancing the triboelectric electrification capability and charge storage capability of dielectrics has hindered the overall performance breakthroughs of the DC-TENG. Here, a field emission model-based DC-TENG (FEM-TENG) is proposed, inspired by lightning rods. The enhanced local electric field between dielectric materials and electrodes induces strong electron tunneling, which improves charge neutralization on the surface of materials and their internal charge storage space, thereby utilizing the dielectric volume effect effectively and strengthening triboelectricity. Guided by the field emission model, the FEM-TENG with a historic crest factor of 1.00375 achieves a groundbreaking record of an average power density of 16.061 W m-2 Hz-1 (1,591 W m-3 Hz-1), which is 5.36-fold of the latest DC-TENG. In particular, the FEM-TENG with high durability (100%) truly realizes the collection of breeze energy and continuously drives 50 thermohygrometers. Four additional applications exemplify the FEM-TENG, enabling comprehensive sensing of land, water, and air. This work proposes a paradigm strategy for the in-depth utilization of dielectric films, aiming to enhance the output power of DC-TENGs.

Ballistic transport in sub-10 nm monolayer InAs transistors for high-performance applications.

As an outstanding two-dimensional (2D) semiconductor among III-V compounds, InAs has attracted significant attention due to its much higher electron mobility than silicon and potential for enhanced opportunities in the field of electronic and optical devices. Recently, 2D semiconducting InAs with a thickness of 4.8 nm has been successfully prepared. Here, we systematically investigated the ballistic transport characteristics of sub-10 nm monolayer InAs (InAsH2) metal-oxide-semiconductor field-effect transistors (MOSFETs) by using ab initio quantum transport simulation, which includes on-state current, subthreshold swing, intrinsic delay time, and power consumption. The results suggest that the monolayer (ML) InAsH2 MOSFETs exhibit excellent performance with a beneficial doping concentration and underlap, which can meet the high-performance requirements of the International Technology Roadmap for Semiconductors (ITRS) for the 2013 version until the length of the gate is decreased to 4.0 nm. Moreover, we studied the influence of high-k dielectric effects. We found that both the on-state current and subthreshold swing with a 5.0 nm-gate-length are apparently improved. This work indicates that ML InAsH2 is a suitable nominee for the upcoming generation of channel materials.

Structural and Dielectric Studies of Ni1−xAlxFe2O4

The nanoparticles of Ni1−xAlxFe2O4(x = 0,0.5) were synthesized via using sol-gel route and studied the structural and dielectric effect of aluminium content on Nickel site. The X-ray diffraction (XRD) revealed the single-phase cubic spinel structure of the parent compound. The lattice constant, volume, density, bond lengths, specific surface area and crystallite size were determined from the Rietveld refinement. In the Raman analysis, there are five active modes present in the synthesized samples. FTIR spectroscopy confirmed the formation of spinel ferrite and showed the characteristics absorption bands of metal oxygen (Fe-O) observed around 424-450 and 601-620 cm−1 corresponding to the stretching vibration frequency of the metal-oxygen at the octahedral site and tetrahedral site respectively. Dielectric behaviour showed that the value of dielectric constant (ε') and tangent loss (tanδ) decreases with frequency and confirmed the general behaviour of ferrites. The AC Conductivity (σac) was found lower in Ni0.5Al0.5Fe2O4 compared to NiFe2O4.

Boosting Photovoltaic Output by Dual External Manipulations on 1D Ferroelectric Nanorods Solar Cell: Electric Field and Giant Dielectric Constant Variation

Unlike common photovoltaic (PV) cells whose performance has been anchored, the merits for the cells made of ferroelectric crystals, due to the non‐centrosymmetric structure, provide possibility to further enhance the efficiency by dual external manipulations through increasing the internal electric field strength and the dielectric screening effect, based on anomalous photovoltaic (APV) arisen by the external poling and giant dielectric constant variation through temperature‐controlled ferro‐paraelectric phase transition. In this study, a synergistic effect achieving a 67% improvement in power conversion efficiency (PCE) of the n‐i‐p configuration solar cell by ferroelectric polarization and high dielectricity is observed, taking c‐axis‐aligned single‐crystalline ferroelectric SbSI nanorods as the active layer. The opposite poling effects are revealed leading to asymmetric characteristics in the n‐i‐p configuration. The enhancements of Jsc induced by inherent giant variation imply strong dielectric screening facilities to lower carrier cross section captured by charged defects, uniformly suppressing various recombination mechanisms, understood by the Langevin model. Therefore, solar cells employing n‐i‐p structured ferroelectric thin films as absorbing layers hold promising potential for achieving defect‐tolerance high performance through rational design, external polarization, and dielectric property control.

Dielectric Breakdown Strength of Polypropylene Blended with Ethylene Octene Elastomers

Polymer blends have become a major focus of research in exploring the potential for new dielectric material applications, particularly in the insulation of high voltage systems. In the current research area, polypropylene (PP) is being investigated as an insulation material for high voltage alternating current and direct current power cables. However, PP must be treated with rubbery materials such as elastomers to lessen its overall stiffness for power cable extrusion. While various promising results have been published on the potential use of PP/elastomer blends as dielectric materials, the dielectric effects of adding ethylene octene elastomer to PP have been less explored. This paper discusses the alternating current (AC) and direct current (DC) breakdown strength of PP that contains different amounts of ethylene octene elastomer (10, 30, and 50 wt%). The addition of ethylene octene elastomer to PP affects the breakdown performance of the blend systems under both AC and DC fields. Significantly, an increase in elastomer contents results in a notable reduction in the AC and DC breakdown strength. A discussion is presented on the mechanisms underlying the change in the breakdown strength caused by the different amounts of ethylene octene elastomer blended with PP.

Elucidating the microscopic origin of observed anti-correlation between the protein-protein and protein-water interaction energies

Water as a solvent plays an important role in dictating the structure and dynamics of the large biomolecules like proteins. It has been proposed that the protein dynamics and energetics are closely coupled to the water molecules in the hydration shell. In particular, it has been shown earlier that the fluctuations in intra-protein (protein-protein) interaction energy is strongly anti-correlated with the protein-water interaction energy (solvation energy). Moreover, the dynamical signatures of water gets reflected into the protein dynamics in terms of a dominant power law behavior. In this work, we have carried out systematic molecular dynamics (MD) simulations of three different protein systems to understand the key physical factors that contribute to such anti-correlations. First, we compare the dynamics in globular folded proteins like Lysozyme with intrinsically disordered peptides (IDPs) like Amyloid beta to show that enhanced conformational fluctuations lead to significantly stronger anti-correlation. Trp-cage miniprotein shows a similar behavior distributed over two sub-ensembles of folded and unfolded states. We also investigate what type of interactions and molecular processes are responsible for the observed anti-correlation. In particular, we observe that the extent of correlation decreases significantly in the order of charged, polar and non-polar amino acid residues. Charged residues that form salt bridge interactions show a dominant anti-correlation. Surprisingly, a few non-polar (hydrophobic and buried) residues demonstrate significant anti-correlation as well. We attribute this to the structural fluctuations that lead to an equilibrium between buried and solvent exposed states of these residues, where the protein-protein and protein-water interactions compensate each other. Our studies indicate that the molecular origin of the observed anti-correlation can be vary depending on the type of the interaction. The overall coupling/correlation is dominated by the electrostatic interactions and charged residues due to a general dielectric screening effect, whereas a few buried hydrophobic residues may also show such coupling due to structural dynamics between buried and exposed states.

Absolute quantification of nucleic acid on digital microfluidics platform based on superhydrophobic–superhydrophilic micropatterning

Digital microfluidics (DMF) shows great potential in the manipulation of individual droplets. However, the limited number of electrode control wirings for droplet control intrinsically restrains the massive generation of pL/nL individual droplets, fundamentally hindering the realization of high throughput applications on DMF such as digital nucleic acid amplification and analysis. This work demonstrates on-chip high throughput digital loop-mediated isothermal amplification (dLAMP) on a DMF platform based on a functional substrate with super-wettability contrast. Exploiting the passive dispensing technique as empowered by electrowetting on dielectric (EWOD) effect, a total of 1818 individual droplets with high uniformity are generated on the super-hydrophilic microarray within 1 min. Separation within the oil phase without tubes and valves can avoid evaporation, ensuring a precise total reaction volume. Absolute quantification of λDNA with a dynamic range of 1–1000 copies/μL is achieved by counting the amount of positive microdroplets after on-chip incubation, demonstrating the strong potential for rapid, low-cost, reliable, and quantitative nucleic acid analysis with high accuracy.

High dielectric constant ethanolamine based two-dimensional perovskite thin films and their application in perovskite PSCs

In recent years, the extensive exploration of two-dimensional (2D) perovskites in the perovskite solar cell field has been driven by their remarkable humidity stability and tunable optoelectrical properties. However, the device performance in solar cells is hampered by the constraints posed by the quantum and dielectric confinement effects. In this study, ethanolamine (EA+) with a high dielectric constant was introduced as a spacer cation to fabricate 2D perovskite (EA)2(MA)4Pb5I16 films. The investigation focused on evaluating the influence of various additives on the crystallinity, surface morphology, light absorption capacity, and carrier lifetime of EA+-based perovskite thin films. By incorporating MACl as an additive, we achieved smooth and compact perovskite thin films of superior quality, leading to perovskite solar cells (PSCs) with a remarkable photovoltaic efficiency of 10.24%. Furthermore, the unencapsulated (EA)2(MA)4Pb5I16-based device maintained 83% of its original efficiency after 840 h of storage in ambient conditions, outperforming the 2D perovskite counterpart that employed phenethylamine (PEA+) as the spacer cation with a dielectric constant of 3.314. These results convincingly demonstrate that the strategic incorporation of high dielectric constant organic cations into 2D PSCs offers a promising avenue for elevating their efficiency and humidity stability.

Optical LC-like resonances in high-index particles

Electric LC resonances, occurring in metallic circuits, govern the motion of free electrons or electric signals. In this paper, optical LC-like resonances in high-index particles (HIPs) or dielectric LC resonances have been studied, which involve bounded electrons and optical fields instead. The resonance effect is dominated by optical analogues of inductance and capacitance, which can be determined according to the electromagnetic energy bounded near the particle. The viewpoint of dielectric optical circuit with equivalent parameters facilitates the understanding of dielectric resonance effect. The result also provides a method for studying the optical properties of the HIPs.

Highly Sensitive Flexible Capacitive Pressure Sensor with Porous Hierarchical Structure Realized by a Microwave Curing Method

The introduction of porous hierarchical microstructures effectively improves the sensitivity of flexible pressure sensors. However, it is difficult to achieve porous hierarchical microstructures for pressure sensors through inexpensive, efficient, and simple preparation methods. Herein, a hemispherical array with porous hierarchical microstructure is prepared on polydimethylsiloxane substrate using a simple one‐step microwave curing process with glucose as porogen. Furthermore, the flexible electrode based on the polydimethylsiloxane substrate is combined with an ionic liquid polymeric gel membrane to obtain a flexible capacitive pressure sensor. Thanks to the deformability of porous hierarchical microstructure and the double‐dielectric layer effect of ionic liquid polymeric gel membrane, the sensor displays an ultrahigh sensitivity of 131.21 kPa−1 within 0–1 kPa. Meanwhile, the sensor has short response time, excellent dynamic loading stability, as well as excellent long‐term stability (>3000 cycles). In application testing, the sensor effectively monitors various physiological activities like pulse, breathe, speech, and swallowing, demonstrating its good prospects in the field of health electronics. Most importantly, the proposed microwave curing method can realize the preparation of porous hierarchical structure on flexible substrate through a one‐step process, which offers a fresh way for the economical, green, and efficient preparation of high‐sensitivity capacitive pressure sensors.

Modified BBFTO ceramic oxide with high dielectric constant and low loss-tangent for possible electronic applications

In this report, a complex barium titanate ceramic oxide of the form BaBi1.6Fe0.4TiO6 was prepared by the solid-state casting process. More Bi3+ percentage was selected to boost the dielectric and ferroelectric effects, while lowering the Fe3+ content could minimize the leakage current and consequently, the dielectric loss (tanδ). The X-ray diffraction (XRD) data suggests an establishment of monoclinic distortion (P21/c) of smaller mean crystallite size (∼40 nm) using the Debye-Scherrer formula. The compound exhibits dielectric values, such as ɛr ∼ 771, and relatively low loss, tanδ ∼ 0.017 at the ambient experimental conditions. Thus, the material can be incorporated into different electronic devices where higher dielectric constant and lower losses are essential, for example, multi-layered ceramic capacitors, transmission lines, and gate dielectrics. The AC-conductivity essence of the compound follows Jonscher’s power law as well as Arrhenius relation. The PE hysteresis loop was traced at different conditions with a function of the incident electric field in the ambient atmospheric conditions. The outcome of this study revealed that the material has remanent polarization hence suggesting a ferroelectric effect with less hysteresis loss; therefore, it could be useful in memory storage devices.