Tunneling Effect Research Articles

Ag-doped PDA interface strategy for selective electron transition integrating EMI shielding and anti-corrosion performance

Metal-based electromagnetic interference (EMI) shielding composites are essential for ensuring electromagnetic compatibility but are often compromised by susceptibility to corrosion, especially in harsh environments. Existing strategies to mitigate coupling corrosion typically involve physical barriers, which inevitably hinder conductivity. In this study, we introduce a novel interface doping approach to fabricate lightweight Graphite@PDA/Ag@Ag composites that simultaneously enhance EMI shielding and corrosion resistance. The PDA/Ag layer selectively regulates electrons with different migration directions and energies to migrate, increasing charge transfer resistance at Ag/graphite interfaces and ensuring conductivity through a tunneling effect. This design achieves an ultralow corrosion rate of 4.313 × 10-8 μm/yr (a billionth that of 316L stainless steel) alongside superior EMI shielding effectiveness of 109 dB in the X-band at 1.5 mm thickness. Remarkably, the composite maintains over 90 dB shielding efficiency after 7 d in NaCl solutions across various pH levels. Furthermore, simulated corrosion under South China Sea conditions predicts a coating loss of less than 0.026 μm over 7 years. This work presents a transformative approach to mitigating coupling corrosion in EMI shielding materials, offering a practical route to high-performance, corrosion-resistant composites without the need for a protective topcoat.

Surface plasmon-coupled Ag nanosphere-internalized nanocavity arrays for ultrasensitive SERS sensing

Surface-enhanced Raman spectroscopy (SERS) is strongly dependent on the metallic plasmonic nanostructures that can generate plasmon resonance coupling effects. Plasmonic nanostructures with sub-nanometer interparticle gaps or cavities have shown great potential in generating high local electromagnetic fields. Unfortunately, achieving precise control over the geometrical morphology of these nanostructures at the sub-nanometer scale presents significant challenges, particularly in applications where high consistency and homogeneity are required. Here, a reliable approach is proposed to construct plasmon-coupled Ag nanosphere-internalized nanocavity (SIC) arrays to enhance sensitivity and reproducibility in SERS sensing. This novel SIC nanostructure consists of a precise arrangement of Ag nanospheres located at the bottom of Au nanocavities, separated by a precisely controlled nano-Al2O3 dielectric layer. The Al2O3 dielectric layer plays a crucial role in inhibiting quantum tunneling effects at the nanogaps, thereby suppressing charge recombination and leading to strong plasmon resonance coupling. The SERS enhancement tends to significantly diminishes as the nanogap size increases from 4 to 10nm, a spatially averaged SERS enhancement factor of 3.5*108 was obtained when the gap size is 4nm, aligning well with the FDTD simulation results. As a representative application, an indirect detection strategy is utilized to selectively detect TNT with a high level of homogeneity and reproducibility, achieving a relative standard deviation of less than 7.8%. Together with the capability to be fabricated on a flexible polyimide substrate, the SIC substrate shows significant potential for practical applications.

Development of green synthesised AgNPs decorated on MWCNT modified guar gum-based self-healing hydrogel for strain sensors

Flexible conductive hydrogel strain sensors are gaining popularity due to their exceptional stretchability, sensitivity, and potential for wearable devices. However, their widespread use is hindered by significant issues, such as poor electrical conductivity and weak response time. To address these challenges, new hydrogels based on guar gum, borax, and glycerol have been fabricated via a green synthesis technique. These hydrogels were reinforced with functionalised multiwalled carbon nanotubes (f-MWCNTs) and silver nanoparticle decorated multiwalled carbon nanotubes (AgNP-MWCNTs). The resulting conductive hydrogels exhibited a self-healing capability of 83.2% and effective strain sensing with a gauge factor of 6.58. The incorporation of AgNP-MWCNTs significantly improved the electrical conductivity up to 3.05 ± 0.02 S m− 1, thanks to the tunnelling effect between f-MWCNTs and the synergic interaction of AgNP-MWCNTs. Moreover, the hydrogel sensors displayed excellent durability, enduring 3000 cycles of tensile loading and unloading at 50% strain. This innovative use of green design principles offers a straightforward, cost-effective, and environmentally friendly process for producing high-performance soft materials. These materials hold significant promise for various practical applications, including artificial skins, flexible electronics, and healthcare monitoring, highlighting the high relevance and impact of this research.

Massive-vortex realization of a Bosonic Josephson Junction

We study the mass exchange between two rotating, quantum massive vortices in a two-component Bose-Einstein condensate. The vortices, in the majority component, exhibit a filled core, where the in-filling minority component undergoes a quantum tunneling effect. Remarkably, we observe that the two-vortex system features stable Josephson oscillations, as well as all the nonlinear phenomena, including the macroscopic quantum self-trapping, that characterize a Bosonic Josephson Junction. We propose an analytical model for describing the intervortex tunneling, obtained by implementing the coherent-state representation of the two-mode Bose-Hubbard model. This allows us to give the explicit expression of the model's parameters in terms of the physical macroscopic parameters of the two-vortex system. The comparison of the dynamical scenario predicted by the model with that emerging from the Gross–Pitaevskii equations is very good for sufficiently small atom numbers, while at larger atom numbers it grows less precise, presumably due to the partial exclusion of the many-body interactions from our model. The definition of an effective self-interaction parameter allows us to include the many-body effects, thus restoring a quite good agreement with the numerical results. Interestingly, the recognition of the bosonic Josephson dynamics paves the way to the investigation of new dynamical behaviors in multivortex configurations. Published by the American Physical Society 2024

Force-electric properties of smart cementitious composites reinforced with carbon fiber and conductive recycled fine aggregates

A type of intelligent cement mortar was created in the laboratory to achieve higher piezoresistive sensitivity for self-health monitoring of concrete structures and to address the reduction in mechanical properties caused by using recycled fine aggregate (RFA). It is a type of cement-based material that natural fine aggregate is partially replaced with highly conductive modified recycled fine aggregate (M-RFA) treated with graphite powder-agar gel impregnation, and a small amount of carbon fibre (CF) was uniformly distributed in the M-RFA mortar to construct a three-dimensional conductive network. The paper studied the intelligent cement mortar's workability, mechanical properties, conductivity, and piezoresistive performance. The results show that the content of M-RFA has little effect on the working performance of the composites, and CF significantly affects the working performance of the composites, which can meet the requirements after adding a superplasticizer. The addition of M-RFA will reduce the mechanical properties of smart cement mortar, but the multi-doped carbon fibre can restore the reduction of mechanical properties caused by M-RFA. Since CF helps M-RFA to be embedded in a conductive network by directly connecting M-RFA or tunnelling effect, conductive mortars doped with CF and M-RFA can significantly reduce resistivity, improve piezoresistive sensitivity, and improve signal stability. The loading rate affects the piezoresistive properties of cement mortar, and the strain sensitivity is negatively linearly correlated with the loading rate. It is worth noting that the conductive mortar with 0.24 vol% carbon fibre and 80 % M-RFA content achieves the highest strain sensitivity (836.9), lower resistivity (150.1 Ω•cm), and the best economy.

Damage Characteristics of Blasting Surrounding Rock in Mountain Tunnel in Fault Fracture Zones Based on the Johnson–Holmquist-2 Model

Blasting is a widely employed technique for tunnel construction in mountainous regions; however, it often causes damage to the surrounding rock mass, particularly in fault fracture zones, which can lead to hazards such as rockfalls and collapses. This study examines the characteristics of damage to surrounding rock due to tunnel blasting through fault fracture zones. Based on an actual tunnel blasting construction project, we conducted a finite element analysis using the JH-2 material model, taking into account the width of the fault fracture zone. Results indicate that as the width of the fault fracture zone increases, the disturbance effect of tunnel blasting on the surrounding rock becomes more pronounced. Compared to the arch bottom and arch waist of the tunnel, the tunnel vault primarily absorbs the slip deformation and compressive forces resulting from blasting disturbances in the fault fracture zone. The findings of this paper contribute a valuable methodology for analyzing the mechanical mechanisms in mountain tunnel blasting and provide essential theoretical parameters to inform the design and construction of tunnel blasting projects.

An explicitly correlated potential energy surface for N2-OCS complex: Out-of-plane motion and tunneling dynamics.

A four-dimensional potential energy surface (4D-PES) has been constructed for the N2-OCS complex. The PES is achieved by applying the explicitly correlated coupled cluster method, which incorporates single, double, and perturbative triple excitations [CCSD(T)-F12a], along with the augmented correlation consistent triple zeta (aug-cc-pVTZ) basis set. The rovibrational levels are precisely determined and assigned through bound state calculations and wavefunction analysis. The calculated transition frequencies reproduce the experimental observations accurately, achieving an RMSE of 0.0005cm-1 for the 23 rotational transitions (J ≤ 6, Ka ≤ 2). The R-φ contour plot of the wave function clearly demonstrates the unambiguous delocalization of the dihedral angle, and the averaged geometry of the ground vibrational state is determined to be non-planar with φ = 90°. To obtain a quantitative analysis of this phenomenon, we expanded the 3H-solution model [Guo et al., J. Quant. Spectrosc. Radiat. Transfer 309 (2023) 108711] from a three-dimensional system (Ar-AgF) to a nine-dimensional system (N2-OCS). Based on this model, the tunneling splitting was calculated to be 0.0822cm-1, which excellently matches the experimental result of 0.0817cm-1. The excellent agreement between the theoretical and experimental results suggests that the wavefunction delocalization and out-of-plane motion can be attributed to the tunneling effects in the ground vibrational state.

Investigation of inter-dot tunnelling effect in hybrid coupled QDs heterostructures for short-wave infrared detection (SWIR) application

This paper explores the coupling between two different types of dots for enhancing the performance of p type/hole based (p-i-p) quantum dot infrared photodetectors (QDIPs). There are two possible con: Stranski-Krastanov (SK) QDs can be deposited on submonolayer (SML) QDs, or the SML QDs can be deposited first, followed by SK QDs. Here, both configurations are tried, and the fact that the tunnelling improves with a decrease in the barrier is exploited. The tunnelling of carriers from one QD to another QD is facilitated by the overlap of their wavefunctions, which depends on their spatial separations between the dots. A smaller barrier will lead to enhanced tunnelling probability. Utilising this idea, samples with 20 nm and 7.5 nm barriers between the QDs are grown with both types of configurations. An enhancement is anticipated in the absorption and carrier lifetime of the p-i-p QDIP structures, making them well-suited for detection in short-wavelength infra-red regions. The p-i-p configuration with the active layers of coupled QDs sandwiched between p-type dopped layers, can effectively absorb SWIR photons and generate long-lived carriers for improved photodetection performance. With the help of Photoluminescence (PL), Photoluminescence Excitation (PLE), and X-ray Diffraction (XRD) experiments, we expect large dispersion in SK on SML configuration, significantly improved carrier transfer via tunnelling and thermalisation and, changes in dot density for both of the configurations. Development of a more efficient SWIR device is expected by the insightful understanding of carrier transfer by tunnelling and thermalization with respect to the barrier thickness in the coupled QD based heterostructures.

Quantum Chemistry Study on Cl-Initiated Reactions of 2-Chloropropane and 2-Methylpropanoyl Halogen (Cl, Br, F): Mechanism, Kinetics, and Atmospheric Implications.

Halogenated volatile organic compounds (HVOCs) pose significant bioaccumulative and toxicological risks, necessitating effective strategies for their removal. Here, we show, through a computational study employing density functional theory and coupled cluster methods, the detailed mechanism and kinetic properties of Cl-initiated degradation reactions of 2-chloropropane (2-CP, (CH3)2CHCl) and 2-methylpropanoyl halide ((CH3)2CHCOX, X = Cl, Br, F). The reaction rate constants of all the channels were calculated by the canonical variational transition state theory (CVT) with the correction of the small curvature tunneling effect (SCT) at 200-1000 K. The subsequent transformation pathways of the major radical products of (CH3)2CHCl and (CH3)2CHCOCl in the presence of O2, NO, and HO2 radical were investigated. The results elucidate the reaction pathways and rate constants, which are in excellent agreement with the experimental data at 296 K. We further explore the atmospheric implications of these reactions by assessing the atmospheric lifetime (τ) and ozone depletion potential (ODP). Additionally, we delve into the aquatic toxicity and bioaccumulation potential of the reactants and their transformation products. This study not only advances our knowledge of the atmospheric fate of halogenated hydrocarbons but also underscores the importance of considering the environmental and toxicological impacts in the development of HVOC mitigation strategies.

Semiclassical Transition State Theory (SCTST) Rate Coefficients for the Unimolecular Decomposition of the Ethoxy (CH3CH2O) Radical.

The thermal unimolecular decay of ethoxy is important in high-temperature combustion environments where the ethoxy radical is a key reactive intermediate. Two dissociation pathways of ethoxy, including the β-C-C scission to yield CH3 + CH2O and the H-elimination to make H + CH3CHO, were characterized using a high-level coupled-cluster-based composite quantum chemical method (mHEAT-345(QΛ)). The former route is found to be dominant while the latter is insignificant, in agreement with previous experimental and theoretical studies. Thermal rate coefficients are calculated for P = 0.001-658 atm (of air) and T = 300-2500 K using semiclassical transition state theory (SCTST) in combination with a pragmatic two-dimensional E,J-resolved master equation (2DME). The effects of tunneling and anharmonicity on the calculated rate constants are also examined. The tunneling factor is found to be inversely dependent on pressure, contrary to previous observations of pressure-dependent tunneling in entrance channels.

Local Electronic Correlation in Multicomponent Møller-Plesset Perturbation Theory.

We present in this contribution the first application of local correlation in the context of multicomponent methods. Multicomponent approaches allow for the targeted simulation of electrons together with other Fermions (most commonly protons) as quantum particles. These methods have become increasingly popular over the last years, particularly for the description of nuclear quantum effects (in strong hydrogen bonds, proton tunneling, and many more). However, most implementations are still based on canonical formulations of wave function theory, which we know for decades to be computationally inefficient for capturing dynamical correlation effects. Local correlation approaches, particularly with the use of pair natural orbitals (PNOs), enable asymptotically linear scaling of computational costs with very little impact on the overall accuracy. In this context, the efficient use of density fitting approximations in the integral calculation proves essential. We start by discussing our implementation of density-fitted NEO-MP2 and NEO-PNO-LMP2, upgrading the electronic correlation treatment up to PNO local coupled cluster level of theory. Several challenging examples are provided to benchmark the method in terms of accuracy as well as computational cost scaling. Following appropriate protocols, anharmonic corrections to localized X-H stretches can be applied routinely with little computational overhead.

Kinetic Study on the H-Abstraction Reactions from 1-Nitropropane by H and OH Radicals.

To improve the comprehension of the combustion kinetics of 1-nitropropane (1-NP), the H-abstraction reactions from 1-NP by H and OH radicals are theoretically explored using the canonical variational transition-state theory combined with the multistructural torsional anharmonicity and small-curvature tunneling corrections (MS-CVT/SCT). The M08-HX/cc-pVTZ method is adopted for geometry optimizations and frequency calculations due to its effective performance in describing the current reaction systems with an average mean unsigned deviation of 0.95 kcal mol-1 against the benchmark by the high-level DLPNO-CCSD(T)/CBS(T-Q) method. The rate constants for the investigated reactions are calculated using the MS-CVT/SCT method at 200-2000 K, and a good agreement is achieved by comparing our calculations with the available literature data. The rate constant calculations show that the multistructural torsional anharmonicity, variational effect, and tunneling effect have different influences on the H-abstraction reactions 1-NP + H/OH, and the reaction channel at the Cβ position is the most important above the room temperature. With our calculations, a literature combustion kinetic model of 1-NP is revised, and the new model demonstrates improved performance across most conditions. Sensitivity analysis demonstrates that the H-abstraction reaction channel, 1-NP + OH = CH3CHCH2NO2 + H2O, alters the combustion kinetics of 1-NP and plays an important role in controlling its ignition process.

Weakly negative permittivity from three-dimensional printed polydimethylsiloxane/graphene films in the radio frequency band

Epsilon-negative materials (ENMs) has become a research hotspot due to their unique physical properties and practical applications in fields such as directional radiation and tunneling effects. In this work, weakly negative permittivity (from -50 at 10 kHz to -25 at 1 MHz) was realized from three-dimensional printed polydimethylsiloxane/graphene films. The dielectric properties including complex permittivity (ε', ε″), complex impedance (Z', Z″), alternating current conductivity (σac), and dielectric loss tangent (tanδ) were investigated. When graphene content reached 15 wt%, the interconnected graphene network was formed, resulting in negative permittivity. Theory calculations were further used to explore the mechanism. The electrons around carbon atoms showed significant delocalization. With the effect of the external electromagnetic field, the electrons on the surface of graphene could easily oscillate collectively, leading to negative permittivity. Differential charge density exhibited that interfacial electric fields were formed between polydimethylsiloxane and graphene, enhancing positive permittivity. Therefore, when the graphene content reached 15 wt%, the film exhibited weakly negative permittivity, which was the result of the mutual balance between the graphene conductive network and the interface electric fields.

A two-dimensional thin film structure with spectral selective emission capability suitable for high-temperature environments

Spectral selective emission materials, characterized by their high emission efficiency within specific wavelength ranges, play a crucial role in various fields such as infrared stealth and radiative cooling. In this study, leveraging the tunneling effect of ultrathin metal layers and the impedance matching principle, we designed a one-dimensional multilayer thin film structure composed of Mo/Ge/Al. This design successfully achieved spectral selective emission within the 3-14 μm infrared spectrum range, showcasing superior high-temperature infrared stealth capabilities. Research findings indicate that the infrared atmospheric window (ε3-5 μm=0.40, ε8-14 μm=0.30) maintains a low emissivity within the temperature range from room temperature to 400°C, while high emissivity in non-infrared atmospheric windows (ε5-8 μm=0.81) enables radiative cooling. The use of high emissivity in the non-infrared atmospheric window reduced the surface temperature of this structure by 15.3°C compared to untreated Si substrate under similar heating conditions. The temperature reduction was 34.1°C when compared to a Si substrate coated with a 200 nm Al film. This straightforward and easily scalable structure not only presents novel solutions for applications in infrared stealth and radiative cooling but also holds vast potential for diverse fields including military, aerospace, and industrial manufacturing, injecting fresh impetus and possibilities into technological advancement.

Regulation of Sensitized Phosphorescence in Two-Dimensional Lead Bromine Perovskites by Tuning Excited-State Interactions.

Excited-state interactions within the organic layer play a critical role in sensitized phosphorescence of two-dimensional (2D) perovskites. Herein, we regulate excited-state interactions utilizing isomeric organic ligands 1-naphthylmethylamine (1-NMA) and 1-(2-naphthyl)-methanamine (2-NMA). Transient absorption and first-principles calculations are employed to elucidate the mechanisms of triplet energy transfer (TET) and triplet excimer formation. The results indicate that wave function hybridization and tunneling effect at the inorganic/organic interface contribute to rapid (∼20 ps) and highly efficient (>98%) TET, with the triplet excimer being generated in (1-NMA)2PbBr4 at picosecond time-scale. However, triplet excimer is barely observed in (2-NMA)2PbBr4 due to varying ligand stacking modes. Despite rapid TET, the efficiency of sensitized phosphorescence is low (<0.5%), which is ascribed to pronounced nonradiative decay. By mixing isomeric ligands and optimizing respective ratio, a maximum phosphorescence enhancement of 7.6 folds is achieved. This work provides a detailed mechanistic understanding of triplet excimer sensitization and regulation of sensitized phosphorescence.

Research of Gallium Nitride as Next-Generation Semiconductor

In today’s society, semiconductors have become an indispensable material in people’s lives, as they are closely related to daily needs such as internet access, power supply, and computing. The most widely used semiconductor material currently is silicon. Its cost advantage in the early stage made other semiconductor materials lag far behind. As semiconductor manufacturing has progressed to nanoscale and even 3-nanometer technology, problems with silicon semiconductors have become increasingly apparent. As the size of silicon transistors continues to shrink, quantum tunneling effects such as leakage current and gate leakage current have caused power consumption to increase continuously. Moreover, the silicon manufacturing process requires harsh conditions such as high vacuum, high temperature, and multiple steps, which increases the production cost and process complexity. Therefore, people have pinned their hopes on the next-generation semiconductor material, gallium nitride (GaN), as an alternative to silicon. Given its superior properties such as wider bandgap, higher electron mobility, and better thermal conductivity, gallium nitride (GaN) offers promising solutions to overcome the limitations of silicon-based semiconductors.

Tunable bandpass frequency selective surface with wideband tuning and low insertion loss based on tunneling waveguide array

AbstractIn this paper, we present a tunable bandpass frequency‐selective surface (FSS) with wide tuning range. The FSS consists of a metallic rectangular waveguide array integrated into the double‐sided printed circuit board (DSPCB) and an array of embedded varactors with a bias network on the backside of the DSPCB. The waveguide array exhibits a frequency‐selective transmission peak due to the tunneling effect, and the transmission frequency can be adjusted by modifying the capacitance of varactors using different bias voltages. One benefit of this setup is that the varactors, along with the bias network, are situated on the same layer, resulting in a significant reduction in overall thickness to just 0.006λc (where λc represents the free‐space wavelength at the highest transmission frequency). Additionally, the insertion loss related to the parasitic resistance of varactors is notably reduced due to the innovative integrated design of biasing lines with varactors and the nearly full‐metal waveguide array. A prototype has been manufactured and tested, demonstrating that by varying the varactor capacitance from 0.12 to 1 pF, the passband showcases a frequency tuning range of 2.32:1, spanning from 5.8 to 2.5 GHz with an insertion loss ranging from 0.2 to 2.6 dB.

Giant tunneling magnetoresistance in insulated altermagnet/ferromagnet junctions induced by spin-dependent tunneling effect

Giant tunneling magnetoresistance in insulated altermagnet/ferromagnet junctions induced by spin-dependent tunneling effect

Nonlinear tunneling of partially nonlocal dark-dark annular sneaker waves under a parabolic potential

Annular rogue waves have been reported, but little is known about how to excite and control them, particularly their tunneling effect. From the projecting relation between the vector partially nonlocal nonlinear Schrödinger equation possessing different transverse-directional diffractions and the parabolic potential and vector constant-coefficient nonlinear Schrödinger equation, via the Darboux method, partially nonlocal dark-dark annular sneaker wave approximate solutions are found. Two aspects of the study are carried out: (i) four excitations of partially nonlocal dark-dark annular sneaker waves including complete, delayed, valley-maintained and prohibitive excitations and (ii) nonlinear tunneling of partially nonlocal dark-dark annular sneaker waves are studied. The influence of two parameters R and l on dark-dark annular sneaker waves is also analyzed. The partially nonlocal characteristics of dark-dark annular sneaker waves passing through the nonlinear well implies that the layer of annular sneaker wave structures increases in xyz-coordinate when the value of the Hermite parameter adds. These findings will further our understanding of the partially nonlocal nonlinear wave in the disciplines of cold atom and optical communication.

Threshold voltage instability of SiC MOSFETs under very‐high temperature and wide gate bias

AbstractThreshold voltage (VTH) instability affects the reliability of silicon carbide (SiC) MOSFETs. In this article, the influence of gate bias (VGS) and high temperature on VTH instability is investigated under wide VGS and very‐high temperature range (150°C to 275°C). The degradation mechanism of gate oxide under coupling of different electrical and thermal stress is revealed. When the device is subjected to +VGS, the relationship between VTH shift and temperature is not monotonic and there is a temperature turning point. This is mainly related to the capture/release and generation of electron traps. However, the VTH shift increases sharply and gate oxide breakdown for the device bias at +35 V, which is related to Fowler–Nordheim (F–N) tunnelling effect. For a large −VGS, the VTH shift is very small. Moreover, when the negative VGS decreases, the VTH shift is positively correlated with temperature, which may result from the activation and charge exchange of hole traps. However, the influence of moving ions changes the temperature dependence of VTH shift for the device bias at −30 V. Finally, the devices of different manufacturers are studied and similar change patterns are found. This finding provides guidance for the further application of SiC MOSFETs under high temperatures and different voltages.