Search Results (166)

Electric-field-sensitive dielectrics play a crucial role in electric field induction sensing and related capacitive conversion, with interfacial polarization and charge accumulation largely determining the signal output. This paper introduces graphene/transition metal dichalcogenide (TMD) (MoSe₂, MoS₂, and WS₂) heterojunctions as functional fillers to enhance the dielectric response and electric-field-induced voltage output of flexible polydimethylsiloxane (PDMS) composites. Density functional theory (DFT) calculations were used to evaluate the stability of the heterojunctions and interfacial electronic modulation, including binding behavior, charge redistribution, and Fermi level-referenced band structure/total density of states (TDOS) characteristics. The calculations show that the graphene/TMD interface is primarily controlled by van der Waals forces, exhibiting negative binding energy and significant interfacial charge rearrangement. Based on these theoretical results, graphene/TMD heterojunction powders were synthesized and incorporated into polydimethylsiloxane (PDMS). Structural characterization confirmed the presence of face-to-face interfacial contacts and consistent elemental co-localization within the heterojunction filler. Dielectric spectroscopy analysis revealed an overall improvement in the dielectric constant of the composite materials while maintaining a stable loss trend within the studied frequency range. More importantly, calibrated electric field induction tests (based on pure PDMS) showed a significant enhancement in the voltage response of all heterojunction composite materials, with the WS₂-G/PDMS system exhibiting the best performance, exhibiting an electric-field-induced voltage amplitude 7.607% higher than that of pure PDMS. This work establishes a microscopic-to-macroscopic correlation between interfacial electronic modulation and electric-field-sensitive dielectric properties, providing a feasible interface engineering strategy for high-performance flexible dielectric sensing materials. Full article

We investigate optical bistability (OB) in a hybrid system comprising a semiconductor quantum dot (SQD), a metallic nanoshell (MNS), and a cell membrane within the framework of the multipole approximation. Bistability phase diagrams plotted in the system’s parameter subspaces demonstrate that, in the weak exciton–phonon coupling regime, dynamic switching of bistable states among no-channel, single-channel, and dual-channel configurations can be achieved via precise modulation of the MNS’s dielectric shell thickness. Especially, a critical sensing threshold is identified: the absorption peak disappears and a bistable effect emerges when only 1.82% of normal cells undergo malignant transformation. Furthermore, the bistable region exhibits a gradual broadening trend with an increasing proportion of cancerous cells, yielding a quantitative and ultra-sensitive readout that underpins a highly accurate strategy for early cancer diagnosis. These findings not only deepen our fundamental understanding of bistability regulation in hybrid quantum-plasmonic systems interfaced with biological materials but also offer valuable insights for the development of next-generation optical switches and biomedical sensing platforms. Full article

In the present study, molecular dynamics simulations with three interatomic potentials (Polymer Consistent Force Field, Adaptive Intermolecular Reactive Empirical Bond Order, and Tersoff) are employed to investigate strain-dependent interfacial thermal resistance across one-dimensional to two-dimensional junctions. Carbon nanotube–graphene junctions exhibit exceptionally low interfacial resistances (1.69–2.37 × 10⁻¹⁰ K·m²/W at 300 K)—two to three orders of magnitude lower than conventional metal–dielectric interfaces. Strain-dependent behavior is highly potential-dependent, with different potentials showing inverse, positive, or minimal strain sensitivity. Local phonon density of states analysis with Tersoff reveals that strain-induced spectral redistribution in graphene toward lower frequencies enhances phonon coupling with carbon nanotube modes. Temperature significantly affects resistance, with 37–59% increases at 10 K compared to 300 K due to long-wavelength phonon scattering. Boron nitride nanotube–hexagonal boron nitride nanosheet junctions exhibit 60% higher resistance (3.2 × 10⁻¹⁰ K·m²/W) with temperature-dependent strain behavior and spacing-insensitive performance. Interfacial resistance is independent of pillar height, confirming junction-dominated transport. The discovery of exceptionally low interfacial resistances and material-specific strain responses enables the engineering of thermally switchable devices and mechanically robust thermal pathways. These findings directly address critical challenges in next-generation flexible electronics where devices must simultaneously manage high heat fluxes while maintaining thermal performance under repeated mechanical deformation. Full article

This work investigated the electrical, dielectric, and magnetic properties of ferrofluids containing Fe₃O₄ nanoparticles and their composites with chitosan (30–100 cP and 100–300 cP), relevant to magnetic hyperthermia. The nanoparticles were synthesized by coprecipitation and characterized using impedance spectroscopy, X-ray diffraction, scanning microscopy with X-ray microanalysis, Mössbauer spectroscopy, and calorimetry. The study showed that the chitosan coating altered the textural properties of Fe₃O₄, reducing the specific surface area from 76.3 m²/g to 68.9–72.5 m²/g. The zeta potential and particle size showed strong pH dependence. Impedance measurements showed that the conductivity of ferrofluids was frequency- and temperature-dependent, with both metallic and dielectric conductivity observed. The complex dielectric permittivity exhibited Maxwell–Wagner–Sillars interface polarization. Calorimetry revealed that specific absorption rate (SAR) ranged from 11.4 to 23.4 W/g, depending on the chitosan concentration and type, while the chitosan coating reduced SAR by 12–40%. These results confirm that the electrical and dielectric parameters of ferrofluids significantly influence their thermal capabilities, which is important for optimizing magnetic hyperthermia therapy when energy dissipation is considered in bio-heat models. Full article

Robust control over the coupling and propagation of surface plasmon polaritons (SPPs) is essential for advancing various plasmonic applications. Traditional planar structures, commonly used to design SPP directional couplers, face limitations such as low extinction ratios and design complexities. These issues frequently hinder the dense integration and miniaturisation of photonic systems. Recently, exceptional points (EPs)—unique degeneracies within the parameter space of non-Hermitian systems—have garnered significant attention for enabling a range of counterintuitive phenomena in non-conservative photonic systems, including the non-trivial control of light propagation. In this work, we develop a rigorous temporal coupled-mode theory (TCMT) description of a non-Hermitian metagrating composed of alternating silicon–germanium nanostrips and use it to explore the unidirectional excitation of SPPs at EPs in the visible spectrum. Within this framework, EPs, typically associated with the coalescence of eigenvalues and eigenstates, are leveraged to manipulate light propagation in nonconservative photonic systems, facilitating the refined control of SPPs. By spatially modulating the permittivity profile at a dielectric–metal interface, we induce a passive parity–time ($\mathcal{PT}$)-symmetry, which allows for refined tuning of the SPPs’ directional propagation by optimising the structure to operate at EPs. At these EPs, a unidirectional excitation of SPPs with a directional intensity extinction ratio as high as 40 dB between the left and right excited SPP modes can be reached, with potential applications in integrated optical circuits, visible communication technologies, and optical routing, where robust and flexible control of light at the nanoscale is crucial. Full article

The rapid detection of pathogenic bacteria is important for the global public health field. Existing detection technologies are generally limited by log efficiency, high costs, and susceptibility to contamination. Advanced detection methods, such as surface plasmon resonance (SPR), have been proposed to break these limitations, with the advantages of fast detection speed and high sensitivity. SPR operates on the principle of attenuated total internal reflection at a metal–dielectric interface. This technique exploits the resonant absorption of incident photons by surface plasmons, facilitating the detection of tiny variations in the local refractive index by tracking the resonance condition change. This review provides a comprehensive overview of the development in the detection of foodborne pathogens using SPR technology, including a detailed discussion of the working principles of SPR, related instrumentation, and various detection methods. Specifically, this review focuses on a discussion of different SPR detection methods in terms of assembly processes, detection specificity, sensitivity, and detection limits in SPR biosensors, aiming to provide the readers with a fundamental knowledge of SPR. Full article

Hybrid bonding technology has emerged as a critical 3D integration solution for advanced semiconductor packaging, enabling simultaneous bonding of metal interconnects and dielectric materials. However, conventional hybrid bonding processes face significant contamination challenges during O₂ plasma treatment required for OH group formation on SiCN or the other dielectric material surfaces. The aggressive plasma conditions cause Cu sputtering and metal migration, leading to chamber and substrate contamination that accumulates over time and degrades process reliability. In this work, we present a novel approach to address these contamination issues by implementing a molybdenum disulfide (MoS₂) barrier layer formed through plasma-enhanced chemical vapor deposition (PECVD) sulfurization of Mo films. The ultrathin MoS₂ layer acts as an effective barrier preventing Cu sputtering during O₂ plasma processing, thereby eliminating chamber contamination, and it also enables post-bonding electrical connectivity through controlled Cu filament formation via memristive switching mechanisms. When voltage is applied to the Cu-MoS₂-Cu structure after hybrid bonding, Cu ions migrate through the MoS₂ layer to form conductive filaments, establishing reliable electrical connections without compromising the bonding interface integrity. This innovative approach successfully resolves the fundamental contamination problem in hybrid bonding while maintaining excellent electrical performance, offering a pathway toward contamination-free and high-yield hybrid bonding processes for next-generation 3D-integrated devices. Full article

Plasmonic metasurfaces that convert hydrogen-induced dielectric changes into optical signals hold promise for next-generation hydrogen sensors. Here, we employ simulations and theoretical analysis to systematically assess single-layer, bilayer, and trilayer nanodisk arrays comprising magnesium, palladium, and noble metals. Although monolithic Mg nanodisks show strong optical contrast after hydrogenation, the corresponding surface plasmon resonance disappears completely, preventing quantitative spectral tracking. In contrast, bilayer heterostructures, particularly those combining Mg and Au, achieve a resonance red-shift of Δλ = 62 nm, a narrowed full width at half maximum (FWHM) of 207 nm, and a figure of merit (FoM) of 0.30. Notably, the FoM is boosted by up to 15-fold when tuning both material choice and stacking sequence (from Mg-Ag to Au-Mg), underscoring the critical role of interface engineering. Trilayer “sandwich” architectures further amplify performance, achieving a max 10-fold and 13-fold enhancement in Δλ and FoM, respectively, relative to its bilayer counterpart. Particularly, the trilayer Mg-Au-Mg reaches Δλ = 120 nm and FoM = 0.41, outperforming most previous plasmonic hydrogen sensors. These enhancements arise from maximized electric-field overlap with dynamically changing dielectric regions at noble-metal–hydride interfaces, as confirmed by first-order perturbation theory. These results indicate that multilayer designs combining Mg and noble metals can simultaneously maximize hydrogen-induced spectral shifts and signal quality, providing a practical pathway toward high-performance all-optical hydrogen sensors. Full article

The electromagnetic density of states (EM-DOS) plays a crucial role in understanding light–matter interactions, especially at metal–dielectric interfaces. This study explores the impact of interface geometry, material properties, and nanostructures on EM-DOS, with a focus on surface plasmon polaritons (SPPs) and evanescent waves. Using a combination of analytical and numerical methods, the behavior of EM-DOS is analyzed as a function of distance from metal–dielectric interfaces, showing exponential decay with penetration depth. The influence of different metals, including copper, gold, and silver, on EM-DOS is examined. Additionally, the effects of dielectric materials, such as Ti${\mathrm{O}}_2$, PMMA, and ${\mathrm{Al}}_2$${\mathrm{O}}_3$, on the enhancement of electromagnetic field confinement are discussed. The study also investigates the effect of nanostructures, like nanohole and nanopillar arrays, on EM-DOS by calculating effective permittivity and analyzing the interaction of quantum emitters with these structures. Results show that nanopillar arrays enhance EM-DOS more effectively than nanohole arrays, especially in the visible spectrum. The findings provide insights into optimizing plasmonic devices for applications in sensing, quantum technologies, and energy conversion. Full article

Bilayer transition metal dichalcogenides (TMDs) are promising materials for next-generation field-effect transistors (FETs) due to their atomically thin structure and favorable transport properties. In this study, we employ density functional theory (DFT) to compute the electronic band structures and phonon dispersions of bilayer WS₂, WSe₂, and MoS₂, and the electron-phonon scattering rates using the EPW (electron-phonon Wannier) method. Carrier transport is then investigated within a semiclassical full-band Monte Carlo framework, explicitly including intrinsic electron-phonon scattering, dielectric screening, scattering with hybrid plasmon–phonon interface excitations (IPPs), and scattering with ionized impurities. Freestanding bilayers exhibit the highest mobilities, with hole mobilities reaching 2300 cm²/V·s in WS₂ and 1300 cm²/V·s in WSe₂. Using hBN as the top gate dielectric preserves or slightly enhances mobility, whereas HfO₂ significantly reduces transport due to stronger IPP and remote phonon scattering. Device-level simulations of double-gate FETs indicate that series resistance strongly limits performance, with optimized WSe₂ pFETs achieving ON currents of 820 A/m, and a 10% enhancement when hBN replaces HfO₂. These results show the direct impact of first-principles electronic structure and scattering physics on device-level transport, underscoring the importance of material properties and the dielectric environment in bilayer TMDs. Full article

Diabetes has become a global health challenge, driving the demand for innovative, non-invasive diagnostic technologies to improve glucose monitoring. Urinary glucose concentration, a reliable indicator of metabolic changes, provides a practical alternative for frequent monitoring without the discomfort of invasive methods. In this simulation-based study, we propose a novel asymmetric photonic structure that integrates Tamm plasmon polariton (TPP) modes and a cavity mode for high-precision refractive index sensing, with a conceptual focus on the potential detection of urinary glucose. The structure supports three distinct resonance modes, each with unique field localization. Both the TPP modes, confined at the metallic–dielectric interfaces, serve as stable references whose wavelengths are unaffected by refractive-index variations in human urine, whereas the cavity mode exhibits a redshift with increasing refractive index, enabling high responsiveness to analyte changes. The evaluation of sensing performance employs a sensitivity formulation that leverages either TPP mode as a reference and the cavity mode as a probe, thereby achieving dependable measurement and spectral stability. The optimized design achieves a sensitivity of 693 nm·RIU⁻¹ and a maximum figure of merit of 935 RIU⁻¹, indicating high detection resolution and spectral sharpness. The device allows both reflectance and transmittance measurements to ensure enhanced versatility. Moreover, the coupling between TPP and cavity modes demonstrates hybrid resonance, empowering applications such as polarization-sensitive or angle-dependent filtering. The figure of merit is analyzed further, considering resonance wavelength shifts and spectral sharpness, thus manifesting the structure’s robustness. Although this study does not provide experimental data such as calibration curves, recovery rates, or specificity validation, the proposed structure offers a promising conceptual framework for refractive index-based biosensing in human urine. The findings position the structure as a versatile platform for advanced photonic systems, offering precision, tunability, and multifunctionality beyond the demonstrated optical sensing capabilities. Full article

Hexagonal boron nitride (h-BN) possesses a unique combination of a wide bandgap, high thermal conductivity, and chemical inertness, making it a key insulating and thermal management material for advanced electronics and nanocomposites. However, its intrinsic hydrophobicity and strong interlayer van der Waals forces severely limit exfoliation efficiency and dispersion stability, particularly in scalable liquid-phase processes. Here, we report a synergistic exfoliation strategy that integrates acid-induced hydroxylation with gallium (Ga) intercalation to achieve high-yield (>80%) production of ultrathin (<4 nm) hydrophilic h-BN nanosheets. Hydroxylation introduces abundant -OH groups, expanding interlayer spacing and significantly increasing surface polarity, while Ga intercalation leverages its native Ga₂O₃ shell to form strong interfacial interactions with hydroxylated basal planes. This oxide-mediated adhesion facilitates efficient layer separation under mild sonication, yielding nanosheets with well-preserved lateral dimensions and exceptional dispersion stability in polar solvents. Comprehensive characterization confirms the sequential chemical and structural modifications, revealing the crucial roles of hydroxylation-induced activation and Ga₂O₃ assisted wettability enhancement. This combined chemical activation–soft metallic intercalation approach provides a scalable, solution-processable route to high-quality h-BN nanosheets, opening new opportunities for their integration into dielectric, thermal interface, and multifunctional composite systems. Full article

In SF₆ gas-insulated equipment, solid dielectrics critically degrade insulation performance by reducing the electric field’s ability to withstand gas gaps. To investigate the critical role played by solid dielectric surfaces during the initial phase of gas–solid interface discharge phenomena, this paper experimentally measures the AC breakdown voltage (U_bd) of both dielectric surface-initiated breakdown (DIBD) and electrode surface-initiated breakdown (EIBD) across eight types of post insulator samples. Tests are conducted in 36 mm SF₆ gas gaps under pressures ranging from 0.1 to 0.4 MPa. Combined with electrostatic field simulations, the results reveal that DIBD requires substantially lower U_bd than EIBD under comparable maximum electric field (E_max) conditions. As gas pressure increases, this difference becomes more pronounced. This phenomenon can be explained by three key mechanisms: First, due to the regulatory effect of dielectric materials and shielding electrodes on the electric field distribution, the high-electric-field zone along the gas–solid interface exhibits a longer effective discharge path compared to that in a pure gas gap. This configuration creates more favorable conditions for discharge initiation and subsequent propagation toward the opposite electrode. Second, microscopic irregularities on the dielectric surface induce stronger local electric field enhancement than comparable features on metallic electrodes. Third, in high-electric-field regions adjacent to the dielectric surface, desorption processes significantly enhance electron multiplication during gas discharge, and this enhancement effect becomes more pronounced as gas pressure increases, further lowering the discharge inception threshold. As a result, discharge initiation at dielectric interfaces requires less stringent electric field conditions compared to breakdown in a gas gap, especially at high gas pressure. This conclusion not only accounts for the saturation behavior in the U_bd-p characteristic of SF₆ gas–solid interface discharges but also explains why surface contaminants/defects disproportionately degrade interfacial insulation performance relative to their impact on gas gaps. Full article

Trap states in 2D transition metal dichalcogenides significantly affect the responsivity and response time of photodetectors, and previous ReS₂/Si-based heterojunction photodetectors have struggled to simultaneously achieve high responsivity and fast response. To address this issue, we developed a n-type ReS₂/p-type Si heterojunction photodetector through interface engineering. Specifically, the silicon substrate with a silicon dioxide dielectric layer was treated with inductively coupled soft plasma to adjust the thickness and surface states of the dielectric layer. This treatment created a multilayered heterostructure, which increased carrier concentration, effectively passivated sulfur-vacancy-induced defects, and thereby improved responsivity. Experimental results showed that the silicon-based n-type ReS₂ photodetector achieved a responsivity of 0.88 A W⁻¹ with a rapid response rise time of 2.5 s, a significant improvement from the intrinsic values of 12 mA W⁻¹ responsivity and 6 s rise time. Additionally, due to the defect-tunable nature of this pretreatment technique, the device exhibited enhanced Raman peaks and intensified photoluminescence (PL) absorption features, confirming the effectiveness of the interface engineering in optimizing device performance. Full article

Conductive composites are a flexible class of engineered materials that combine conductive fillers with an insulating matrix—usually made of ceramic, polymeric, or a hybrid material—to customize a system’s electrical performance. By providing tunable electrical properties in addition to benefits like low density, mechanical flexibility, and processability, these materials are intended to fill the gap between conventional insulators and conductors. The increasing need for advanced technologies, such as energy storage devices, sensors, flexible electronics, and biomedical interfaces, has significantly accelerated their development. The electrical characteristics of composite materials, including metallic, ceramic, polymeric, and nanostructured systems, are thoroughly examined in this review. The impact of various reinforcement phases—such as ceramic fillers, carbon-based nanomaterials, and metallic nanoparticles—on the electrical conductivity and dielectric behavior of composites is highlighted. In addition to conduction models like correlated barrier hopping and Debye relaxation, the study investigates mechanisms like percolation thresholds, interfacial polarization, and electron/hole mobility. Because of the creation of conductive pathways and improved charge transport, developments in nanocomposite engineering, especially with regard to graphene derivatives and silver nanoparticles, have shown notable improvements in electrical performance. This work covers the theoretical underpinnings and physical principles of conductivity and permittivity in composites, as well as experimental approaches, characterization methods (such as SEM, AFM, and impedance spectroscopy), and real-world applications in fields like biomedical devices, sensors, energy storage, and electronics. This review provides important insights for researchers who want to create and modify multifunctional composite materials with improved electrical properties by bridging basic theory with technological applications. Full article