Negative Permittivity Research Articles

Achieving High Quality Factor Interband Nanoplasmonics in the Deep Ultraviolet Spectrum via Mode Hybridization.

Interband plasmons (IBPs) enable plasmonic behavior in nonmetallic materials, such as semiconductors. Originating from interband electronic transitions, IBPs are characterized by negative real permittivity that can extend into deep ultraviolet (DUV) spectrum, as demonstrated using silicon. However, the practical applications of IBPs are limited by their inherently broad resonances. In this study, we address this limitation by hybridizing the localized plasmon resonance of silicon nanostructures with the Fabry-Pérot resonance of a SiO2 dielectric layer atop a silicon substrate. This design achieves a simulated quality factor (Q-factor) of ∼43, with experimental measurements yielding a Q-factor of 37 at ∼4.6 eV within the DUV region. Furthermore, we demonstrate a 5.4-fold enhancement in DUV absorption for lignin-modified polyethylene glycol films when integrated with the hybridized DUV cavity, showcasing the potential for UV blocking applications. Our findings offer a versatile platform that can be adapted to other IBP systems and open new opportunities in UV-specific applications.

Adjustable and weak negative permittivity behavior in carbon nanofiber/poly(vinylidene fluoride) metacomposites

Adjustable and weak negative permittivity behavior in carbon nanofiber/poly(vinylidene fluoride) metacomposites

Design of wide bandwidth metamaterial for biosensor and wireless application

Abstract We present a new design and study of metamaterial (MTM) structure for wide bandwidth for biosensor and wireless applications. The geometrical parameters were analyzed and optimized for a triple-band operation in the frequency range of 0.1–16 GHz. The propagation characteristics were obtained using Finite element method. The proposed MTM provides negative permittivity at 1.4 GHz and negative permeability in the 9–16 GHz region. The proposed design exhibits left-handed characteristics in L, C, and Ku microwave region’s frequency band. The electric field (E), magnetic field (H), and surface current distribution of the proposed MTM unit cell have been studied at three different resonance frequencies. The proposed MTM design has a wide bandwidth of 2.2 GHz in C-band and a high effective medium ratio (EMR) of 13.37. The performance of the sensor is evaluated for different biomedical samples in the refractive index range of 1.00 to 1.39. The results indicate that the proposed biosensor has a high sensitivity in triple band of microwave region. The present research work can be highly suitable for Wi-Fi and satellite applications due to its overall performance, including wide bandwidth in the C-band, high EMR, and triple band operation.

Compact wide-stopband slow-wave half-mode substrate integrated waveguide filter with interdigital complementary split-ring resonator metasurface

Abstract In this work, a compact slow-wave half-mode substrate integrated waveguide (HMSIW) bandpass filter is developed by loading the proposed interdigital complementary split-ring resonator (IDCSRR) metasurface for wireless communication and sensing applications. The IDCSRR metasurface is constituted by etching interdigital slots inside the conventional CSRR, which can effectively enhance the product of the equivalent capacitance and inductance of the structure, and eventually reduces the resonant frequency. Through the evanescent-mode transmission generated in HMSIW by the negative permittivity effect of IDCSRR metasurface, miniaturized filter can be realized. Later, to further reduce the filter’s size, the capacitance-enhanced ring-mushroom units are patterned into HMSIW to generate slow-wave effect. Then, to improve the filter’s out-of-band suppression, the source-load coupling scheme is utilized to generate extra transmission zero. Meanwhile, to further widen the stopband, meander spurlines are etched on the input and output microstrip lines to suppress the higher-order harmonics with its bandgap function. To demonstrate the availability of the aforementioned concepts, a bandpass filter based on the HMSIW-IDCSRR unit cell is realized. Measurements show that the fabricated prototype exhibits an center frequency (f0) of 0.97GHz. Moreover, the out-of-band suppression can reach 30dB, with the upper stopband up to 4.31 f0. Hence, the proposed filter achieves good stopband and miniaturization performance.

Study of Negative Permittivity in Nanosized LaNiO3 for Electromagnetic Interference Shielding: A Modified Drude Model Approach

Study of Negative Permittivity in Nanosized LaNiO₃ for Electromagnetic Interference Shielding: A Modified Drude Model Approach

Materials with Negative Permittivity or Negative Permeability-Review, Electrodynamic Modelling, and Applications.

A review of natural materials that exhibit negative permittivity or permeability, including gaseous plasma, metals, superconductors, and ferromagnetic materials, is presented. It is shown that samples made of such materials can store large amount of the electric (magnetic) energy and create plasmonic resonators for certain values of permittivity, permeability, and dimensions. The electric and the magnetic plasmon resonances in spherical samples made of such materials are analyzed using rigorous electrodynamic methods, and the results of the analysis are compared to experimental data and to results obtained with other methods. The results of free oscillation and Mie scattering theories are compared. Similarities and differences between permittivity and permeability tensors for magnetized plasma and magnetized ferromagnetic materials are underlined. Several physical phenomena are explained on the grounds of rigorous electrodynamic analysis and experiments. These phenomena include unequal electric and magnetic energies stored in plasmonic resonators, the small influence of dielectric losses on the Q-factors of magnetic plasmon resonances, the role of radiation and dissipation losses on the properties of plasmonic resonators, and the theoretical possibility of the existence of lightning plasma balls.

Nano carbon powder‐multiwalled carbon nanotubes/poly(vinylidene fluoride) percolating composites with low‐percolation binary functional phases and negative permittivity

AbstractPolymer percolating composites with negative permittivity via the construction of percolating structures are of great interest in electromagnetism. In this study, nano carbon powder‐multiwalled carbon nanotubes/poly(vinylidene fluoride) (CP‐MWCNTs/PVDF) composites comprising binary functional phases CP‐MWCNTs were fabricated using hot‐pressing method. The composites achieved both low percolation threshold and tunable negative permittivity properties across the entire frequency range of testing. Percolation phenomenon was observed as functional phases content reaching 5 wt%, which was reflected as the establishment of percolation network and the occurrence of electrical percolation, resulting in a shift toward metal‐like conduction mechanism. Additionally, the notably low percolation threshold can be ascribed to the synergistic effect between the binary functional phases. The plasma oscillation of free electrons within conductive percolation network plays a crucial role in achieving negative permittivity, a phenomenon that can be elucidated using the Drude model from the free electron theory. Furthermore, analyses of the impedance and equivalent circuit illuminate the connection between percolation phenomenon and dielectric behavior. These findings further reveal the influence of functional phases' morphology and composition on percolation behavior and negative permittivity properties, while expanding the application of polymer‐based percolating composites in electromagnetic devices.Highlights Tunable negative permittivity related to plasma oscillation is achieved. Binary functional phases exhibit a low percolation threshold. Synergistic effect of functional phases leads to low percolation threshold.

Origin of Chiral Phase Transition of Polar Vortex in Ferroelectric/Dielectric Superlattices.

Chiral vortices and their phase transition in ferroelectric/dielectric heterostructures have drawn significant attention in the field of condensed matter. However, the dynamical origin of the chiral phase transition from achiral to chiral polar vortices has remained elusive. Here, we develop a phase-field perturbation model and discover the softening of out-of-plane vibration mode of polar vortices in [(PbTiO3)m/(SrTiO3)m]n superlattices at a critical epitaxial strain or temperature. The softening of the mode leads to the appearance of the axial polarization at vortex cores, resulting in chiral phase transition. It is found that the local negative permittivity plays a crucial role in the enhanced oscillation of axial polarization near the phase transition. Our findings not only reveal the origin of the chiral phase transition of polar vortices but also provide considerable new insight into the dynamics of topological structures and topological phase transitions in ferroelectric systems.

Flexible and biocompatible polyvinyl alcohol/nitrogen-doped porous carbon film with weakly negative permittivity in radio frequency for wearable devices

Flexible and biocompatible polyvinyl alcohol/nitrogen-doped porous carbon film with weakly negative permittivity in radio frequency for wearable devices

Self-Assembly of Colloidal Dumbbell Isomers and Plasmonic Properties for Optical Metamaterials.

In this study, we explore the self-assembly of various colloidal symmetric dumbbell (DB) isomers, including dipole Janus, cis-Janus, trans-Janus, apolar-inward and polar-inward perpendicular Janus, and alternating perpendicular Janus DBs. Using dissipative particle dynamics (DPD) simulations under conditions mimicking experimental setups, we investigate cluster formation driven by emulsion droplet evaporation. Our findings reveal a diverse set of cluster structures, which are in good agreement with experimental and simulation results reported in the literature while also predicting the formation of novel cluster configurations. These structures, characterized by well-defined and predictable patterns, are potentially applicable to creating colloidal molecules and crystals. Furthermore, we examine the dynamics of cluster formation to gain insight into the mechanisms guiding the self-assembly of these diverse colloidal DBs. The study highlights the impact of particle isomerism on the resulting assembly structures. We further select a set of typical nanoclusters obtained, including a tetrahedral cluster, which is the simplest, to study its plasmonic properties. Our findings indicate that increasing the nanoparticle (NP) radius or decreasing the gap between NPs leads to a red shift in the plasmonic resonance wavelength and enhances the resonance strength. We identify critical parameter regions where the electric-dipole and magnetic-dipole resonances can be engineered to achieve negative dielectric permittivity and magnetic permeability, which are essential for developing negative-index metamaterials.

A mirror symmetric dodecagon resonator based double band ENG-metamaterial with multilayer tunability and sensing application

A new mirror-symmetric dodecagon resonator-based metamaterial (MM) has been proposed. It is intended for sensing applications. This MM is a candidate for further study because its transmission coefficient shows numerous resonances in the S and C bands. A low-loss Rogers RT5880 substrate is used to construct the resonating patch, which has an electrical size of 0.104λ × 0.104λ . The proposed MM is electromagnetically characterized using permeability, permittivity, and refractive index studies, revealing resonances at 3.12 GHz and 4.58 GHz. Several parametric analyses have optimized the structure’s design and size. The MM responds similarly to single cells and arrays because of its dodecagon mirror symmetry structure. Electromagnetic characterization studies reveal that the suggested MM exhibits negative permittivity, negligible permeability, and a refractive index. A sandwich construction on top of the frequency-tunable patch of the unit cell is used to investigate frequency tuning utilising various dielectric property-based substrates. The calculated outcome satisfies the simulated effect well. The MM, with an effective medium ratio (EMR) of 9.62, is well-suited for frequency-selective microwave devices due to its unique characteristics. Different oil samples with varying dielectric characteristics are used to test the sensor’s accuracy. The proposed sensor also has high sensitivity, high Q-Factor, and High FOM with a value of 60.89, 65, and 3957.85, respectively. As a result, the proposed sensor has broad applicability, especially in the industrial sector.

Metasurface-Assisted mutual coupling suppression in circularly polarized MIMO antenna array for Sub-6 GHz applications

A double-sided decoupling metasurface (DSDM) method is proposed to reduce the mutual coupling between very closely spaced circularly polarized (CP) MIMO antenna elements for sub-6 GHz applications. A proposed DSDM structure with a square-shaped patch layer is placed over the array to reduce mutual coupling by non-propagating evanescent waves and manipulating the polarization of propagating reflected CP waves. This decoupling mechanism relies on the DSDM’s negative electric permittivity extracted from the meta-atom. When the CP waves were incident to DSDM polarizer through the excited CP antenna of the array, the polarization states of the reflected and transmitted CP waves were changed as controlled by DSDM. In reflection mode, the negative permittivity of DSDM produce two type of the waves reflected waves generated the polarization mismatch and evanescent waves that reduce the coupling between CP antennas, while the transmission mode, controlling the radiation pattern at φ = 45° or φ = 135°. The low-profile proposed decoupling structure was fabricated and experimentally validated. The decoupling design significantly mitigated the measured mutual coupling between the CP antenna elements at 3.5 GHz by more than 15 dB and by more than 13 dB at 3.02 GHz to 3.67 GHz, compared to the reference array. The proposed design achieves less than a 3 dB axial ratio, maximum realized gain of 5.52 dBic at 3.5 GHz. An excellent agreement between the simulated and measured outcomes has been studied.

Tunable negative permittivity performance of Bamboo-derived carbon/NiS2/(CoFe2O4)x/PVC metacomposites in light-dependent resistor and low-frequency reflector

The main goal of this study was to investigate the structural, magnetic, and electrical properties of Bamboo-derived carbon/NiS2/(CoFe2O4)x/PVC metacomposites. These metacomposites are known for being lightweight, expansive, and have high reflection loss, making them useful for various electromagnetic applications. One of the key characteristics of these metacomposites is their negative permittivity, which sets them apart as a unique material. When the concentration of CoFe2O4 nanoparticles in the metacomposites was kept below 0.0027, they exhibited negative permittivity behavior across frequencies ranging from 0 to 100 MHz and beyond. This behavior was attributed to the formation of electrical percolation within the modified bamboo structure, which plays a crucial role in achieving negative permittivity and enhanced AC conductivity. The changes in permittivity with frequency were in accordance with the Lorentz model, indicating a predictable pattern. By adjusting the CoFe2O4 mole fraction to optimize impedance, it was possible to enhance the electromagnetic absorption capabilities of the metacomposites, achieving a reflection loss of −24.363 dB with a thickness of 1 mm at frequency 1E8 Hz. These findings have the potential to advance the field of negative permittivity metacomposites, opening up opportunities for the practical integration of epsilon-negative materials and lightweight absorptive properties in devices such as memristors, low-frequency reflectors, and light-dependent resistors (LDRs).

Modified negative permittivity and X-band microwave absorption in polyvinyl Alcohol–MWCNT metacomposites

Metacomposite films with modifiable negative permittivity are promising for wearable cloaking, sensing, electromagnetic interference shielding, and microwave absorption. The purpose of this study is to fabricate metacomposite films composed of polyvinyl alcohol (PVA) and multi-walled carbon nanotubes (MWCNTs) and demonstrate control of permittivity by varying MWCNT concentration. Drude-Lorentz and Drude models show negative permittivity behaviour as the MWCNT content increases. The Drude-Lorentz and Drude models confirm that at 1 wt% MWCNT loading, percolation occurs, leading to increased conductivity and a transition from positive to negative permittivity (−9 at 10 kHz and −200 at 34 kHz). Drude's model predicts negative permittivity across the entire frequency range of PVA with 3 wt% MWCNT. Metacomposite films exhibit electrical percolation, conductivity switching, permittivity shift, and capacitive-to-inductive transitions. These composites also demonstrate excellent X-band microwave absorption properties (up to −50 dB reflection loss) and a shielding efficiency of 22 dB, suggesting an absorption-dominated shielding mechanism.

Carbon nanotube/polyvinylidene fluoride flexible composite material with low percolation threshold and adjustable negative permittivity

Carbon nanotube/polyvinylidene fluoride flexible composite material with low percolation threshold and adjustable negative permittivity

Polarization-selective metamaterial absorber using tailored Y-shaped SRR for UWB device and Doppler navigation aids applications

In this paper, we present an unprecedented metamaterial absorber design exhibiting exceptional characteristics in electromagnetic wave absorption. The proposed bent Y-shaped structure, fabricated on an FR-4 substrate with copper patches, showcases remarkable performance across a diverse frequency spectrum. Through exhaustive simulations in CST, this design manifests eight distinct resonant frequencies, achieving absorption rates exceeding 90 % at each resonance. The resonances, strategically spanning from L-band (3.728 GHz) through S-band, C-band, X-band, Ku-band, and K-band up to 22.664 GHz, signify unparalleled versatility and efficacy in mitigating electromagnetic radiation. It investigates the equivalent circuit parameters of a proposed metamaterial absorber design, focusing on inductance (L), capacitance (C), and resistance (R). This paper investigates the applications of UWB devices at 3.728 GHz and Doppler navigation aids at the 13.4 GHz frequency as regulated by the Federal Communications Commission. It includes a discussion on near-zero refractive Index Metamaterials (NZRIM), highlighting their potential utilization in achieving extraordinary control over wave behaviour. Notably, the absorber's inherent polarization insensitivity fortifies its adaptability in various applications. Additionally, the metamaterial exhibits near-zero or negative permittivity, altering electric response, while simultaneously demonstrating permeability absolute zero throughout all frequency bands sparking new avenues for exploration and challenging conventional electromagnetic theories.

Enhanced plasmonic performance of TiO2 derived TiN films via gas nitridation

This study demonstrates a cost-effective method for planar titanium nitride plasmonic film by nitriding spin-coated TiO2 in ammonia atmosphere. The effect of nitridation temperature on the structural, morphological, electrical and optical characteristics of the coated films were investigated. The films exhibited high carrier concentration of 1022/cc with significant reduction in resistivity of more than three order of magnitude, indicating the conversion to the nitride phase. Negative permittivity, crucial for plasmonic applications in the visible wavelength region, was verified for wavelengths > 463 nm using Drude-Lorentz model. A three-layer model was employed to verify the material’s plasmonic behaviour. The straightforward fabrication route, which combines spin-coating and ammonia nitridation at 950 °C, offers a new approach for titanium nitride films for plasmonic based gas and biosensing device applications in the visible region. In addition, for fabricating titanium nitride coatings for applications that require abrasion resistance, electrical conductivity, chemical stability, and biocompatibility.

Tunable negative permittivity behavior and excellent electromagnetic shielding performance of pyrolytic carbon‐glass fiber felt/epoxy resin metacomposites

AbstractEffective and accurate adjustment of negative permittivity behavior is worthy of further investigation. Herein, pyrolytic carbon‐glass fiber felt/epoxy resin (PyC‐GFF/ER) metacomposites with tunable negative permittivity were prepared using an impregnation‐calcination method. The permittivity, electrical conductivity, and electromagnetic shielding performance of the polymer metacomposites were investigated. Due to the inherent three‐dimensional structural network of GFF, the PyC adhering to the surface of glass fiber easily formed a conductive network in the composites. As the PyC content increased in the ER composites, the conductivity mechanism changed from hopping conduction to metal‐like conduction. The ER composites with high PyC contents showed negative permittivity behavior and the epsilon‐near‐zero response owing to the low frequency plasma state of free electrons in the PyC‐conduction network. By controlling the PyC content, the negative permittivity behavior of ER composites could be effectively tuned. With the increase in PyC content, the values of negative permittivity increased, and the epsilon‐near‐zero frequency shifted to a higher frequency. Moreover, the ER composites with high PyC contents showed excellent electromagnetic shielding properties (29.4 dB) at X‐band. This work not only provided a feasible method to realize the tunable negative permittivity of polymer metacomposites, but also promoted its application in the microwave field.Highlights The pyrolytic carbon‐glass fiber felt/epoxy resin composites were fabricated. The negative permittivity was first reported in the PyC‐GFF/ER composites. Tunable negative permittivity could be well explained by Drude model. The polymer composites had excellent electromagnetic shielding property.

Tunable negative permittivity behavior in alumina ceramic composites with different carbon fillers

Carbon/ceramic composites with negative permittivity have motivated a considerable concern due to their special properties and various applications. Herein, series of alumina ceramic composites consisting of different carbon fillers were prepared by the hot-pressed sintering, and the carbon fillers included carbon sphere (CS), carbon black (CB), carbon fibre (CF), carbon nanofibre (CNF) and graphene nanosheet (GN). The impact of various carbon fillers on the electrical performance of composites were investigated comparatively. It was found that CF ceramic had hopping conduction, capacitive character and positive permittivity, and micron-sized CFs were embedded in isolation within the ceramic composite. The other ceramics with carbon nanofillers demonstrated metallic-type conductance, inductive character and negative permittivity. The carbon nanofillers evenly dispersed and easily formed carbon network that improve the flow of free electrons in the composites, and the negative permittivity behavior imputed to the low frequency plasmonic state of abundant free electrons in the carbon networks. Furthermore, the magnitude of negative permittivity was in connection with the type of carbon nanofiller. The one- or two-dimensional carbon nanofillers were more easily connected to each other to form a denser carbon network, and thus the CNF and GN ceramics had the larger absolute values of negative permittivity, which was in accord with Drude model.

Tunable Negative Permittivity and Magnetic Properties of Ag/BLM Ceramic Metacomposites

Abstract Percolation composites with tunable negative permittivity have garnered significant attention due to their potential use in the field of electromagnetic interference shielding, near field amplification, antennas, and sensors. However, studies on the magnetic property at a frequency range of 100 MHz to 1 GHz are relatively scarce. The objective of this study was to examine the magnetic property and adjustable negative permittivity of silver/La-doped barium ferrite(Ag/BLM) ceramic metacomposites. In this study, Ag/BLM ceramic metacomposites with varying Ag content were prepared using a simple impregnation-calcination method. We investigate the permittivity, reactance, and permeability of Ag/BLM ceramic metacomposites at 100 MHz ~ 1GHz. The findings indicate that the percolation threshold for Ag/BLM ceramic metacomposites with x wt% is between 10 wt% and 19 wt%. When Ag content reaches 19 wt%, it creates a conductive network that generates a high number of free electrons. This leads to low-frequency plasma states and results in negative permittivity. Meanwhile, the permeability of Ag/BLM ceramic metacomposites shows the frequency dispersion due to the magnetic resonance and eddy current. Therefore, this study's findings suggest that composites with tunable negative permittivity and permeability may be developed and utilised for microwave absorption, antenna design, and wireless power transmission.