Search Results (1,243)

Hexagonal Boron Nitride (h-BN) is an exceptional dielectric material with significant potential for high-performance electronic and optoelectronic devices. While previous studies have explored its role in GaN-based MIS (metal/insulator/semiconductor) structures, the influence of few-layer h-BN on AlGaN MIS devices—particularly with varying Al compositions—remains unexplored. In this work, we systematically investigate the Fowler–Nordheim tunneling effect in few-layer h-BN integrated into AlGaN MIS architectures, focusing on the critical roles h-BN layer count, AlGaN alloy composition, and interfacial properties in determining device performance. Through combined simulations and experiments, we accurately determine key physical parameters, such as the layer-dependent effective mass and band alignment, and analyze their role in optimizing MIS device characteristics. Our findings reveal that the 2D h-BN insulating layer not only enhances breakdown voltage and reduces leakage current but also mitigates interfacial defects and Shockley–Read–Hall recombination, enabling high-performance AlGaN MIS devices under elevated voltage and power conditions. This study provides fundamental insights into h-BN-based AlGaN MIS structures and advances their applications in next-generation high-power and high-frequency electronics. Full article

The photon spin Hall effect (PSHE) arises from the spin–orbit interaction of light. Metasurfaces enable precise control over the PSHE through their influence. Using electromagnetic simulations as its foundation, this work engineers a metal–insulator–metal (MIM) metasurface for generating vortex beams in the near-infrared band, targeting enhanced modulation of the PSHE. Electromagnetic simulations embed vanadium dioxide (VO₂)—a thermally responsive phase-change material—within the MIM metasurface architecture. Numerical evidence confirms that harnessing VO₂’s insulator–metal-transition-mediated optical switching dynamically tailors spin-dependent splitting in the illuminated MIM-VO₂ hybrid, thereby achieving a significant amplification of the PSHE displacement. Electromagnetic simulations determine the reflection coefficients for both VO₂ phase states in the MIM-VO₂ structure. Computed spin displacements under vortex beam incidence reveal that VO₂’s phase transition couples to the MIM’s top metal and dielectric layers, modifying reflection coefficients and producing phase-dependent PSHE displacements. The simulation results show that the displacement change of the PSHE before and after the phase transition of VO₂ reaches 954.7 µm, achieving a significant improvement compared with the traditional layered structure. The dynamic modulation mechanism of the PSHE based on the thermal–optical effect has been successfully verified. Full article

A square patch metasurface is designed, simulated, fabricated, and experimentally tested to investigate polarization characteristics quantitatively. The metasurface consists of one layer unit cell in the form of a square patch with one via and a lumped resistor, which is used for harvesting RF (radio frequency) energy. FR4 dielectric is used as a substrate supported by a metal ground plane. Polarization-dependent properties with specific surface current patterns and voltage dip are obtained when simulating under normal incidence of a plane wave. This characteristic results from changes in surface current conditions when the polarization angle is varied. A voltage dip appears at a specific polarization angle when the surface current pattern is symmetrical. This condition occurs when the position of the lumped resistor from the center of the patch is perpendicular to the linearly polarized incident electric field. A couple of 10 × 10 arrays with different resistor positions are fabricated and tested. The experimental results are in good agreement with the simulated results. The proposed design demonstrates a symmetric unit cell structure with one via and a resistor that exhibits polarization-dependent behavior for linear polarization. An asymmetric patch design is explored through both simulation and measurement to mitigate polarization dependence by suppressing the dip behavior, albeit at the expense of reduced absorption efficiency. This study provides a complete polarization analysis for both symmetric and asymmetric patch metasurfaces with a single via and a single lumped resistor, and introduces a predictive relation between the position of the resistor relative to the center of the patch and the resulting voltage dip behavior. Full article

In this paper, preliminary gate reliability of p-GaN HEMTs under high positive gate bias is studied. Gate robustness is of great interest both from an academic and industrial point of view; in fact, different tests and models can be explored to estimate the device lifetime, which must meet some minimum product requirements, as specified by international standards (AEC Q101, JESD47, etc.). However, reliability characterizations are usually time-consuming and are performed in parallel on multiple packaged devices. Therefore, it would be useful to have a faster method to screen out weaker gate trials, already on-wafer, before reaching the packaging step. For this purpose, a room-temperature stress procedure is presented and described in detail. Then, this screening test is applied to devices with a reference gate process, and, as a result, high gate leakage degradation is observed. Afterwards, a different process implementing a dielectric layer between p-GaN and gate metal is evaluated, highlighting the improved behavior during the stress test. However, it is also observed that devices with this process suffer from very high drain leakage, and this effect is then studied and understood through TCAD (technology computer-aided design) simulations. Finally, the effect of a surface treatment performed on the p-GaN is analyzed, showing improved gate pre-reliability while maintaining low drain leakage. Full article

Aircraft, as electromagnetically complex targets, have radar cross-sections (RCSs) that are influenced by various factors, with the inlet duct being a critical component that often serves as a primary source of electromagnetic scattering, significantly impacting the scattering characteristics. In light of the conflict between aerodynamic performance and electromagnetic characteristics in the design of aircraft engine inlet grilles, this paper proposes a metasurface radar-absorbing inlet grille (RIG) solution based on a NACA symmetric airfoil. The RIG adopts a sandwich structure consisting of a polyethylene terephthalate (PET) dielectric substrate, a copper zigzag metal strip array, and an indium tin oxide (ITO) resistive film. By leveraging the principles of surface plasmon polaritons, electromagnetic wave absorption can be achieved. To enhance the design efficiency, a multi-objective Bayesian optimization framework driven by the expected hypervolume improvement (EHVI) is constructed. The results show that, compared with a conventional rectangular cross-section grille, an airfoil-shaped grille under the same constraints will reduce both aerodynamic losses and the absorption bandwidth. After 100-step EHVI–Bayesian optimization, the optimized balanced model attains a 57.79% reduction in aerodynamic loss relative to the rectangular-shaped grille, while its absorption bandwidth increases by 111.99%. The RCS exhibits a reduction of over 8.77 dBsm in the high-frequency band. These results confirm that the proposed optimization design process can effectively balance the conflict between aerodynamic performance and stealth performance for RIGs, reducing the signal strength of aircraft engine inlets. Full article

Hyperbolic plasmons are a highly desired property in optoelectronics and biomolecular sensing. The necessary condition to realize hyperbolic plasmons is a significant anisotropy of the principal components of the dielectric function, such that at a certain frequency range, one component is negative and the other is positive, i.e., one component is metallic, and the other one is dielectric. Here, we study the effect of anisotropy in ${\mathrm{ReS}}_2$, and our theory shows that ${\mathrm{ReS}}_2$ can host hyperbolic plasmons in the ultraviolet frequency range. The operating frequency range of the hyperbolic plasmons can be tuned with the number of ${\mathrm{ReS}}_2$ layers. However, we note that the significantly large imaginary part of the macroscopic dielectric response in all layered variants of ReS₂ can result in substantial losses for the hyperbolic plasmons, as in the case with other known hyperbolic materials, with the exception of MoOCl₂. We also note that ReS₂ hosts ultraviolet hyperbolic plasmons while ZrSiSe, WTe₂, and CuS nanocrystals host infrared plasmons, providing a novel platform for optoelectronics in the ultraviolet range. Full article

In this paper, a solution to the problem of electromagnetic field scattering on a periodic, constrained, planar antenna structure placed on the boundary of two dielectric media was formulated. The scattering matrix of such a structure was derived, and its generalization for the case of an antenna with a multilayer dielectric substrate was defined. By applying the Galerkin spectral method, the problem was reduced to a system of algebraic equations for the coefficients of current distribution on metal elements of the antenna grid, considering the distribution of the electromagnetic field on Floquet harmonics. The finite transverse dimension of the antenna was considered by introducing, to the solution of the case of an unconstrained antenna, a window function on the antenna aperture. The presented formalism allows modeling the operation of periodic, dielectric, composite antenna arrays. Full article

Linear passive electrical devices/components are usually characterized in the frequency domain by their impedance, i.e., the ratio of the voltage and current phasors. The use of the impedance concept does not raise particular concerns in low-frequency regimes; however, things become more complicated when it comes to rapid time-varying phenomena, mainly because the voltage depends not only on the position of the points between which it is defined but also on the choice of the integration path that connects them. In this article, based on first principles (Maxwell equations and Poynting vector flow considerations), we discuss the concept of impedance and define it unequivocally for a class of electrical devices/components with rotational symmetry. Two application examples are presented and discussed. One simple example concerns the per-unit-length impedance of a homogeneous cylindrical wire subject to the skin effect. The other, which is more elaborate, concerns a heterogeneous structure that consists of a dielectric disk sandwiched between two metal plates. For the lossless situation, the high-frequency impedance of this device (circular parallel plate capacitor) reaches zero when the frequency reaches a certain critical frequency f_c; then, it becomes inductive and increases enormously when the frequency reaches another critical frequency at 1.6 f_c. The influence of losses on the impedance of the device is thoroughly investigated and evaluated. Impedance corrections due to dielectric losses are analyzed using a frequency-dependent Debye permittivity model. The impedance corrections due to plate losses are analyzed by considering radial current distributions on the outer and inner surfaces of the plates, the latter exhibiting significant variations near the critical frequencies of the device. Full article

This paper presents three realizations of a complete set with a horn antenna and a focusing Gradient Index (GRIN) lens in X-band. The set was specifically designed for advancing additive manufacturing (AM) of polymers with different materials and techniques. The set has three constituent parts: a horn antenna, a support, and a lens. The horn antenna is the active element and must be electrically conductive; it was manufactured with Rigid10K acrylic resin and subsequently metallized using an electroless process. The support needed to be light, robust, and electrically transparent, so that Polyamide 11 (PA11) was used. The lens realization was intended for a dielectric material whose permittivity varies with its density. Therefore, the dielectric permittivity and loss tangent of different polymeric materials used in AM at 2.45, 6.25, and 24.5 GHz were measured. In addition, stochastic and gyroid mesh structures have been studied. These structures allow for printing a volume that presents porosity, enabling control over material density. Measuring the dielectric characteristics of each material with each density enables the establishment of graphs that relate them. The sets were then manufactured, and their frequency response and radiation diagram were measured, showing excellent results when compared with the literature. Full article

The structural and electrical properties of double perovskite compounds SrLaFe_1−xMn_xTiO_6−δ (x = 0, 0.33, 0.67, and 1.0) were studied using X-ray diffraction (XRD) and dielectric impedance measurements. The reparation of perovskite compounds was successfully achieved through the precursor solid-state reaction in air at 1250 °C. The purity phase and crystal structures of perovskite compounds were determined by means of the standard Rietveld refinement method using the FullProf suite. The best fitting results showed that SrLaFeTiO_6−δ was orthorhombic with space group Pnma, and both SrLaFe_0.67Mn_0.33TiO_6−δ and SrLaFe_0.33Mn_0.67TiO_6−δ were cubic structures with space group Fm3m, while SrLaMnTiO_6−δ was tetragonal with a I/4m space group. The charge density maps obtained for these structures indicated that the compounds show an ionic and mixed ionic–electronic conduction. The dielectric impedance measurements were carried out in the range of 20 Hz to 1 MHz, and the analysis showed that there is more than one relaxation mechanism of Debye type. Doping with Mn was found to reduce the dielectric impedance of the samples, and the major contribution to the dielectric impedance was established to change from a capacitive for SrLaFeTiO_6−δ to a resistive for SrLaMnTiO_6−δ. The fall in values of electrical resistance may be related to the possible occurrence of the double exchange (DEX) mechanism among the Mn ions, provided there is oxygen deficiency in the samples. DC-resistivity measurements revealed that SrLaFeTiO_6−δ was an insulator while SrLaMnTiO_6−δ was showing a semiconductor–metallic transition at ~250 K, which is in support of the DEX interaction. The dielectric impedance of SrLaFe_0.67Mn_0.33TiO_6−δ was found to be similar to that of (La,Sr)(Co,Fe)O_3-δ, the mixed ionic–electronic conductor (MIEC) model. The occurrence of a mixed ionic–electronic state in these compounds may qualify them to be used in free lead solar cells and energy storage technology. Full article

Over the last decade, numerous impedance studies of the conductivity of suspensions containing colloidal (dielectric, semiconducting or metallic) particles have often led to the conclusion that the well-known Maxwell theory is insufficient to quantitatively explain the properties of these systems. We review some of the most characteristic results and show how the applicability of the Maxwell’s theory can be restored taking into account the adsorption phenomena occurring during AC impedance measurements in nanoparticle suspensions. The latter can drastically change the capacitance of the metal-electrolyte cell boundaries from the standard value, making it strongly dependent on the nanoparticle concentration. This factor significantly affects conductivity measurements through RC circuit characteristics. We present an analysis of available impedance measurement data of the dependence of conductivity on the nanoparticle concentration in this new paradigm. In order to emphasize the novelty and the acute sensitivity of ac-diagnosis to the presence of adsorption phenomena at the metal-electrolyte interface, direct adsorption determinations at such interfaces by using two modern experimental techniques are also presented. The main result of this work is the restoration of Maxwell’s theory, attributing the observed discrepancies to variations in cell conductance. Full article

This paper presents a carbon monoxide (CO) detection mechanism achieved through further improvement of the sensing antenna based on hybrid spoof localized surface plasmons (SLSPs) and cavity resonance. Unlike conventional approaches relying on chemical reactions or photoelectric effects, the all-metal configuration detects dielectric variations through microwave-regime resonance frequency shifts, enabling CO/air differentiation with theoretically enhanced robustness and environmental adaptability. The designed system achieves measured figures of merit (FoMs) of 183.2 RIU⁻¹, resolving gases with dielectric contrast below 0.1%. Experimental validation successfully discriminated CO (ε_r = 1.00262) from air (ε_r = 1.00054) under standard atmospheric pressure at 18 °C. Full article

With the continuous advancement of electromagnetic protection technologies, the development of lightweight electromagnetic wave-absorbing materials with excellent absorption performance has become a critical challenge in the field. In this study, commercially available hollow glass microspheres (HGMs) were employed as templates, and Ni²⁺/Co²⁺ metal ions were used to catalyze the polymerization of dopamine (PDA), forming HGM@Ni_xCo_y/PDA precursors. Subsequent high-temperature pyrolysis yielded lightweight composite absorbing materials, denoted as HGM@Ni_xCo_y/C. This material integrates dielectric loss, conductive loss, magnetic loss, and resonance absorption mechanisms, exhibiting outstanding electromagnetic wave absorption properties. The absorption performance can be effectively tuned by adjusting the Ni-to-Co ratio, with the optimal performance observed at an atomic ratio of 2:3. At a filler loading of 20 wt.%, HGM@Ni₂Co₃/C achieved an effective absorption bandwidth (EAB) of 6.83 GHz (ranging from 10.53 to 17.36 GHz) and a minimum reflection loss (RL_min) of −27.26 dB. These results demonstrate that the synergistic combination of hollow glass bubbles and carbon-based magnetic components not only significantly reduces the material density and required filler content but also enhances overall absorption performance, highlighting its great potential in the development of lightweight and high-efficiency electromagnetic wave absorbers. Full article

Adopting mobile robots for high voltage (HV) live-line operations can mitigate personnel casualties and enhance operational efficiency. However, conventional mechanical arms cannot inspect concealed spaces in the power cable tunnel because their joint integrates metallic motors or hydraulic serial-drive mechanisms, which limit the arm’s length and insulation performance. Therefore, this study proposes a 7-degree-of-freedom (7-DOF) bionic mechanical arm with rigid-flexible coupling, mimicking human arm joints (shoulder, elbow, and wrist) designed for HV live-line operations in concealed cable tunnels. The arm employs a tendon-driven mechanism to remotely actuate joints, analogous to human musculoskeletal dynamics, thereby physically isolating conductive components (e.g., motors) from the mechanical arm. The arm’s structure utilizes dielectric materials and insulation-optimized geometries to reduce peak electric field intensity and increase creepage distance, achieving intrinsic self-insulation. Furthermore, the mechanical design addresses challenges posed by concealed spaces (e.g., shield tunnels and multi-circuit cable layouts) through the analysis of joint kinematics, drive mechanisms, and dielectric performance. The workspace of the proposed arm is an oblate ellipsoid with minor and major axes measuring 1.25 m and 1.65 m, respectively, covering the concealed space in the cable tunnel, while the arm’s quality is 4.7 kg. The maximum electric field intensity is 74.3 kV/m under 220 kV operating voltage. The field value is less than the air breakdown threshold. The proposed mechanical arm design significantly improves spatial adaptability, operational efficiency, and reliability in HV live-line inspection, offering theoretical and practical advancements for intelligent maintenance in cable tunnel environments. Full article

The time-dependent dielectric breakdown (TDDB) degradation mechanism, governed by the synergistic interaction of multiphysics fields, plays a pivotal role in the performance degradation and eventual failure of semiconductor devices and advanced packaging back-end-of-line (BEOL) structures. This work specifically focuses on the dielectric breakdown mechanism driven by metal ion migration within inter-metal dielectric layers, a primary contributor to TDDB degradation. A SPICE-compatible modeling approach is developed to accurately capture the dynamics of this ion migration-induced degradation. The proposed model is rooted in the fundamental physics of metal ion migration and the evolution of conductive filaments (CFs) within the dielectric layer under operational stress conditions. By precisely characterizing the degradation behavior induced by TDDB, a SPICE-compatible degradation model is developed. This model facilitates accurate predictions of resistance changes across a range of operational conditions and lifetime, encompassing variations in stress voltages, temperatures, and structural parameters. The predictive capability and accuracy of the model are validated by comparing its calculated results with numerical ones, thereby confirming its applicability. Furthermore, building upon the established degradation model, the impact of line-edge roughness (LER) is incorporated through a process variation model based on the power spectral density (PSD) function. This PSD-derived model provides a quantitative characterization of LER-induced fluctuations in critical device dimensions, enabling a more realistic representation of process-related variability. By integrating this stochastic variability model into the degradation framework, the resulting lifetime prediction model effectively captures reliability variations arising from real-world fabrication non-uniformities. Validation against simulation data demonstrates that the inclusion of LER effects significantly improves the accuracy of predicted lifetime curves, yielding closer alignment with observed device behavior under accelerated stress conditions. Full article