Polarization Effects Research Articles

Investigation of Polarization Effect on Terahertz-Enhanced Air Plasma Acoustic Emission

Investigation of Polarization Effect on Terahertz-Enhanced Air Plasma Acoustic Emission

Design studies on electronics and data acquisition of a real time diamond spectrometer for the SPARC neutron camera.

The design of a compact 2 × 2 diamond matrix with independent and redundant pixels optimized for the spectrometric neutron camera of the SPARC tokamak is presented in this article. Such a matrix overcomes the constraints in dynamic range posed by the size of a single diamond sensor while keeping the ability to perform energy spectral analysis, marking a significant advancement in tokamak neutron diagnostics. A charge pre-amplifier based on radio frequency amplifiers based on InGaP technology transistors, offering up to 2GHz bandwidth with high robustness against radiation, has been developed. A first single-channel device has been tested and proven to provide a fast signal development time of 20-25ns, necessary to mitigate pileup effects while offering precise energy measurements. As the diamond sensors may suffer from polarization effects due to the trapping of charges at the diamond/metal interface, a periodical bias inversion can guarantee optimal performance. To facilitate that, a reversible high voltage power supply has been developed. The ongoing development of data acquisition equipment and real-time processing algorithms based on programmable gate arrays further enhances the neutron camera's capabilities.

MSSTGNN: Multi-Scaled Spatio-Temporal Graph Neural Networks for short- and long-term traffic prediction

Accurate traffic prediction plays a crucial role in ensuring traffic safety and minimizing property damage. The utilization of STGNNs in traffic prediction has gained significant attention from researchers aiming to capture the intricate time-varying relationships within traffic data. While existing STGNNs commonly rely on Euclidean distance to assess the similarity between nodes, which may fall short in reflecting POI or regional functions. The traffic network exhibits static from a macro perspective, whereas undergoes dynamic changes in the micro perspective. Previous researchers incorporating self-attention to capture time-varying features for constructing dynamic graphs have faced challenges in overlooking the connections between nodes due to the Softmax polarization effect, which tends to amplify extreme value differences, and fails to accurately represent the true relationships between nodes. To solve this problem, we introduce the Multi-Scaled Spatio-Temporal Graph Neural Networks (MSSTGNN), which aims to comprehensively capture characteristics within traffic from multiscale viewpoints to construct multi-perspective graphs. We employ a trainable matrix to enhance the predefined adjacency matrices and to construct an optimal dynamic graph based on both trend and period. Additionally, a graph aggregate technique is proposed to effectively merge trend and periodic dynamic graphs. TCN is developed to model nonstationary traffic data, and we leverage the skip and residual connections to increase the model depth. A two-stage learning approach and a novel MSELoss function is designed to enhance the model's performance. The experimental results demonstrate that the MSSTGNN model outperforms the existing methods, achieving state-of-the-art performances across multiple real-world datasets.

NPDC structure double-channel N-polar E-mode GaN HEMTs: Innovations in enhancing RF and DC performance and mitigating trap effects

—High-electron-mobility transistors (HEMTs) based on gallium nitride (GaN) are favored for their exceptional performance in high-power and high-frequency applications. However, developing dual-channel HEMTs presents challenges due to spontaneous polarization effects and design complexities. This study introduces a novel N-polar E-mode GaN HEMT with a dual-channel structure, featuring recessed drain-source regions and non-alloyed ohmic contacts. TCAD simulations provide theoretical insights and optimization strategies for these structures, focusing on the combination of N-polar GaN and ultra-wide bandgap AlN barrier layers. The optimized device demonstrates a threshold voltage of +1.08 V and a 45.9 % increase in current density. The N-polar double-channel HEMT (NPDC-HEMT) exhibited a 55.75 % improvement in peak transconductance, with Ft increasing from 13.3 GHz to 30.1 GHz and Fmax from 63.7 GHz to 65.9 GHz. Further enhancement was achieved in the T-gate variant (NPDC-T-HEMT), with Ft reaching 52.6 GHz and Fmax 94.4 GHz. The dual-channel design effectively mitigated short-channel effects and current collapse, demonstrating the potential for high-power RF applications.

Magnetic Field-Induced Polar Order in Monolayer Molybdenum Disulfide Transistors.

In semiconducting monolayer transition metal dichalcogenides (ML-TMDs), broken inversion symmetry and strong spin-orbit coupling result in spin-valley lock-in effects so that the valley degeneracy may be lifted by external magnetic fields, potentially leading to real-space structural transformation. Here, magnetic field (B)-induced giant electric hysteretic responses to back-gate voltages are reported in ML-MoS2 field-effect transistors (FETs) on SiO2/Si at temperatures <20 K. The observed hysteresis increases with |B| up to 12 T and is tunable by varying the temperature. Raman spectroscopic and scanning tunneling microscopic studies reveal significant lattice expansion with increasing |B| at 4.2 K, and this lattice expansion becomes asymmetric in ML-MoS2 FETs on rigid SiO2/Si substrates, leading to out-of-plane mirror symmetry breaking and the emergence of a tunable out-of-plane ferroelectric-like polar order. This broken symmetry-induced polarization in ML-MoS2 shows typical ferroelectric butterfly hysteresis in piezo-response force microscopy, adding ML-MoS2 to the single-layer material family that exhibits out-of-plane polar order-induced ferroelectricity, which is promising for such technological applications as cryo-temperature ultracompact non-volatile memories, memtransistors, and ultrasensitive magnetic field sensors. Moreover, the polar effect induced by asymmetric lattice expansion may be further generalized to other ML-TMDs and achieved by nanoscale strain engineering of the substrate without magnetic fields.

Photoinduced modulation and the effect of CNT loading on field effect transistor characteristics of CNT/ZnO/PVDF composite.

CNT/ZnO/PVDF polymer composite phototransistor is studied for the effect of CNT loading and the photoinduced modulation on its transfer characteristics. XRD study shows that the induced strain in the composite is due to the addition of CNT to the ZnO/PVDF composite. The percentage of β-phase present in PVDF is estimated through Raman spectroscopy and the composite's spectral response is determined by UV-Vis absorbance spectroscopy. From the DC electrical conductivity study it is found that the percolation threshold for the composites is obtained for 0.3 wt% of CNT, and 0.44 wt % of CNT loading makes the composite conductive. On adding 1 wt% of CNT, the electrical conductivity of the ZnO/PVDF composite increases 40 times (~ 0.2 μS/m). The temperature-dependent DC conductivity shows that the conductivity of the composites changes from variable range hopping (VRH) to band conductance upon an increase in CNT loading above the percolation threshold and exhibits a negative temperature coefficient (NTC). Two terminal photoconductivity studies are done to understand the photo enhancement and sensitivity of all the devices. PE hysteresis studies show that the polarization of the composites increases drastically from 0.05 μC/cm2 below the percolation threshold to 10 - 30 μC/cm2 above the percolation threshold of CNT in the composite. To study the effect of interfacial polarization on photoconductivity, the composite is studied in a three-terminal device format using SiO2 as a gate dielectric. A band diagram analysis of the oxide-composite and CNT/ZnO interface is done to understand the mechanism behind the photoinduced field effect on transfer characteristics and the effect of CNT loading. The switching behavior and decay time under UV illumination are studied to understand the effect of CNT loading and photoinduced polarization. The persistent photoconductivity decreases and the charge collection efficiency of the FET increases as the CNT loading increases.

Determination and analysis of spectral fluorescence cross-sections of bacteria aerosols

Fluorescence cross-sections of single bacteria provide information on the strength of fluorescence response of bacteria for particular excitation conditions and give hints about a possible distinguishability of bacteria by fluorescence techniques. In this report, the fluorescence cross-sections of dry bacteria aerosols are derived from fluorescence spectra by absolute calibration of the measuring system. The fluorescence is measured in a continuous aerosol flow. The aerosol concentration is calculated from microscopic analyses of bacteria samples taken from the aerosol flow. Established calibration methods such as Mie scattering from monodisperse spheres and Raman scattering from water are applied to the same set of fluorescence spectra. The cross-section data obtained are evaluated with regard to their independency from the applied measuring system. The results are compared to data published in the literature. Polarization effects are identified to contribute to the discrepancies between the different datasets.Graphical abstract

Control of ferroelectricity in Ta-doped HfO2 and its non-zero-crossing current–voltage hysteresis behavior

Hafnium oxide (HfO2)-based ferroelectrics are being explored as potential candidates for ferroelectric memory devices due to their highly compatibility with complementary metal-oxide-semiconductor (CMOS) technology. Enhancing the remanent polarization and investigating the underlying mechanism are crucial tasks. In the present study, tantalum (Ta) was introduced as a dopant to induce ferroelectric properties in HfO2, a large portion of orthorhombic phase was recognized in the as-grown Ta:HfO2 without further thermal treatment. The remanent polarization of Ta:HfO2 thin films can be optimized by adjusting the oxygen flow rates during the sputtering process. The influencing factors for enhanced ferroelectric performance include the control of Ta concentration, its valence state, and the presence of singly ionized oxygen vacancies, which are influenced by oxygen addition. Furthermore, the resistive switching behavior showing non-zero crossing current–voltage (I–V) hysteresis is associated with ferroelectricity and the presence of oxygen vacancies. A model has been proposed to explain the ferroelectric resistive switching with non-zero crossing I–V characteristics by considering the role of oxygen vacancies and polarization effects. This model suggests that the oxygen vacancies at the surface layer, along with ferroelectric polarization, play a crucial role in electron transport.

Turning crisis into opportunity: Intrinsically polarised low concentration eutectic electrolytes enable highly reversible zinc anodes

Low-concentration electrolytes (LCEs) hold great promise for sustainable energy storage due to their low viscosity, excellent wettability, and cost-effectiveness. However, their intrinsic polarization issues often lead to side reactions and dendrite growth, hindering their broader application. Herein, we present an approach to convert the negative effects of intrinsic polarization in LCEs into advantages, overcoming these challenges. The experimental and theoretical analyses demonstrate that acetate-adsorbed zinc anodes can harness the intrinsic polarization of LCEs to direct the electrocrystallization process on their surfaces. This promotes the preferential orientation of Zn(002) plane with high stability, resulting in symmetric batteries loaded with low-concentration eutectic electrolytes (LCEE) that maintain surprisingly low voltage polarization during the dendrite-free growth of up to 3150 h. In addition, by forming an organic-inorganic composite film enriched with N and Cl, LCEE achieves rapid migration of Zn2+. This allows Zn//PANI full batteries with LCEE to demonstrate superior capacity and cycling stability compared to other Zn-based batteries with LCEs. This study not only achieves a divergent design in LCEs but also provides clear guidance for future electrolyte development.

Ageing-Related Macrophage Polarisation in the Trigeminal Ganglion Enhances Incisional Intraoral Pain.

Although macrophage polarisation in the trigeminal ganglion (TG) is crucial in orofacial pain hypersensitivity, the effect of ageing-related changes and their involvement in intra-oral nociception remains unclear. We assessed the effect of ageing-related macrophage polarisation in TG on intra-oral mechanical pain hypersensitivity following palatal mucosal incision using senescence-accelerated mice (SAM)-prone8 (SAMP8) and SAM-resistant 1 (SAMR1). Mechanical head-withdrawal reflex threshold (MHWRT) of the palatal mucosa was measured for 21 days after palatal mucosal incision. On days 3 and 14, the abundance of Iba-1-immunoreactive (IR) cells, CD11c-IR cells (pro-inflammatory macrophages (M1)), C-C motif chemokine ligand 2 (CCL2)-IR M1-macrophages, CD206-IR cells (anti-inflammatory macrophages (M2)) and transforming growth factor-β (TGF-β)-IR M2-macrophages in the TG was analysed. The effect of continuous intra-TG administration of CCL2-neutralising antibody or recombinant-CCL2 on MHWRT was examined. Incision-induced decrease in MHWRT was enhanced in SAMP8 compared with that in SAMR1. On days 3 and 14, the number of CCL2-IR M1-macrophages in TG was increased in SAMP8 compared with that in SAMR1. CCL2-neutralising antibody suppressed, whereas recombinant-CCL2 increased pain hypersensitivity in SAMP8. Mechanical pain hypersensitivity after oral mucosal injury is potentiated and sustained by age-related enhancement of CCL2 signalling via M1-macrophage hyperactivation in TG.

Current-induced spin polarization and spin Hall effect in III-V compounds two-dimensional materials

Current-induced spin polarization and spin Hall effect in III-V compounds two-dimensional materials

Differential and integral elastic cross sections for electrons and positrons collisions with carbon dioxide molecules

This study investigates the elastic scattering of electrons and positrons by carbon dioxide (CO2) molecules over a wide energy range from 1 eV to 1 KeV. We have computed differential and integral elastic cross-sections (DCS and ICS) using partial wave analysis and compared the theoretical results with available experimental data. Our findings show a strong correlation with experimental results, particularly at mid to high-energy ranges, validating the employed theoretical frameworks. Additionally, the Sherman function was examined to explore spin polarisation effects during scattering events. This research provides crucial insights for applications in atmospheric physics, materials science, and molecular scattering processes, demonstrating its direct relevance to real-world problems and paving the way for further investigation into particle-molecule interactions.

The coupling effect of polarization and lattice strain on charge transfer between quintuple-layer Al2X3/Al2Y3 (X, Y = O, S, Se, Te; X ≠ Y) interfaces

The electronic properties of two-dimensional (2D) polar semiconductor heterostructures are closely related to the degree of interlayer charge transfer. Taking 2D quintuple-layer (QL)-Al2S3 and QL-Al2O3 semiconductor as examples, we study the electronic properties and interlayer charge transfer of QL-Al2S3/Al2O3 interfaces by first-principles calculations. The driving force of the directional interlayer charge transfer is the polarization electric field. The kinetic process of interface charge transfer is related to the charge (strain) distribution of QL-Al2S3 and QL-Al2O3. By changing the strain distribution of QL-Al2S3/Al2O3 interfaces with same polarization arrangement, the electronic properties and interfacial charge transfer of heterojunctions can be adjusted. Our work is an important indicator for understanding the dynamic process of interlayer charge transfer between 2D polar semiconductors. In addition, we propose one method for regulating the electronic properties of heterojunctions by coupling polarization and lattice strain.

High‐efficiency electromagnetic absorption of HfC–SiCf ceramics with a 3D reticular structure

AbstractThe development of high‐temperature electromagnetic (EM) wave absorbing materials is an important direction for achieving radar stealth in high‐speed aircraft. In this study, HfC–SiCf composite ceramics with 3D reticular structure were synthesized in one‐step using the molten‐salt‐assisted carbon thermal reduction method. During the synthesis process, SiC grew in situ into a fibrous structure with a diameter of 500 nm and lengths ranging from 2 to 30 µm. By adjusting the molar ratio of HfC to SiC, the HfC‐30 mol% SiC (HS30) exhibited the best EM absorption performance at room temperature, with a minimum reflection loss (RLmin) of −31.4 dB at 16.1 GHz and an effective absorption bandwidth (EAB) of 4.6 GHz. The excellent absorption performance was attributed to the 3D reticular structure composed of SiC fibers, HfC bulk, and HfC nanoparticles, which significantly increased the number of pores and heterogeneous interfaces in the material. These microinterfaces induced interface polarization effects, thereby effectively enhancing the EM absorption. As the temperature increased, the EM absorption performance declined. At 900°C, the HS30 sample exhibited an EAB of 1.18 GHz from 12.4 to 13.58 GHz and an RLmin of 22.6 dB at 13.0 GHz. This research provides references for understanding the effects of material composition and structure on EM absorption performance.

Rational Control of Maximum EMI/CPL Intensity and Wavelength of Bora[6]helicene via Polarity and Vibronic Effects.

Solvent polarity control as an efficient methodology to regulate the chiroptical properties, including spectral shape, width, intensity, wavelength, etc., has emerged as a novel frontier in optical materials design. However, the underling relationship connecting polarity to the optical property remains unclear. Herein, using state-of-the-art computations and the FC|VG model, the solvent effect on the chiroptical properties of bora[6]helicene was accurately and systematically computed to shed light on this issue. It is found that the vibronic coupling is crucial in explaining the spectral shape, width, and relative intensity of different peaks. Moreover, the intensity and position of the emission (EMI) and circularly polarized luminescence (CPL) are closely related to the polarity of the solvent. Intriguingly, we got a series of good linear relationships between polarity and EMI|CPL (|r| ≥ 0.95). Thus, this parameter can be used as a potential descriptor to estimate the intensity and position of EMI|CPL, leading to new strategies for designing fully colored fluorescent materials.

Comparing the effects of anodal and cathodal transcranial direct current stimulation of primary motor cortex at varying intensities on motor learning in healthy young adults.

Inconsistent results are observed in the effects of transcranial direct current stimulation (tDCS) with different montages on motor learning. This study aimed to compare the effects of anodal and cathodal tDCS (c-tDCS) over primary motor cortex (M1) at different intensities on motor learning in healthy young adults. The participants were randomly divided into: (1) 1mA M1 c-tDCS, (2) 1mA M1 anodal tDCS (a-tDCS), (3) 2mA M1 c-tDCS, (4) 2mA M1 a-tDCS and (5) M1 sham tDCS groups. The groups received 20-min stimulation with serial reaction time task (SRTT) incidentally, while the tDCS was turned off after 30 s in the sham tDCS group. Response time (RT) and error rate (ER) during SRTT were assessed prior, during and 72 h after the intervention. The results of the paired t-test indicated that online learning occurred in all groups (p< 0.05), except in M1 c-tDCS (1mA) (p> 0.05). One-way ANOVA analysis also indicated that there were differences in offline learning (RT (F(DF) =5.19(4); p< 0.001; and ER (F(DF) =9(4), p< 0.0001) among groups, with more offline learning in 1mA M1 a-tDCS, 2mA M1 c-tDCS and 2mA M1 a-tDCS groups (p< 0.05). On the other hand, the 1mA M1 c-tDCS group did not indicate any consolidation effect or even a trend toward negative offline learning. M1 a-tDCS with different intensities and also 2mA M1 c-tDCS may be helpful for the enhancement of motor learning in young healthy adults. This study enhances our understanding of tDCS intensity and polarity effects on motor learning, with potential for optimizing therapeutic protocols.

When Disagreement Becomes Uncivil on Social Media: The Role of Passive Receiving and Active Expression of Incivility in Influencing Political Polarization

Exposure to cross-cutting viewpoints may not always play the deliberative role it is supposed to. This study uses both panel survey and social media data to examine how disagreement can trigger incivility, including exposure to and expression of incivility, and further elicit emotions and influence polarization. Results from the two-wave panel survey indicate that cross-cutting exposure has a polarizing effect first through promoting exposure to uncivil messages and expression of uncivil opinions, then through negative emotions. Notably, cross-cutting exposure can indirectly reduce polarization by first encouraging expression of uncivil opinions and then eliciting positive emotions, highlighting the importance of active expression. Analysis of data from the Hong Kong-based discussion forum HKDisc demonstrates that cross-cutting exposure is positively related to exposure to uncivil messages, and exposure to and expression of incivility predict polarization regardless of whether positive or negative emotions are detected in the uncivil content. This study provides empirical evidence of the effects of cross-cutting exposure and incivility on polarization at the individual and collective levels.

Rationally designed photothermal-pyroelectric Fe0.9Ni0.1S2/ZnSnO3 Z-scheme heterojunction for promoting electrical charge polarization towards optimized photocatalytic H2 evolution and intermolecular N-N coupling reaction

Developing a photocatalytic composite system that can couple hydrogen (H2) evolution and benzylamine (BA) oxidation is a challenging task, especially while avoiding sacrificial agents and value-added chemicals. Here, a practical approach is reported to develop a photothermal-pyroelectric-Fe0.9Ni0.1S2/ZnSnO3 photocatalytic system with core–shell and Z-scheme heterostructure via hydrothermal and annealing methods. Although Fe0.9Ni0.1S2 nanoparticles (NPs) could convert most of near-infrared (NIR) light energy into heat energy to drive the pyroelectric effect of ZnSnO3, it also results in temperature fluctuations (ΔT) in the system, causing natural polarization and thermoelectric effects under the condensed water circulation. As a result, the as-designed Fe0.9Ni0.1S2/ZnSnO3-2 composites could yield up to 7.194 mmol g-1h−1 with exceptional photocatalytic H2 evolution under simulated sunlight. This result is 5.41 and 4.92-fold those of Fe0.9Ni0.1S2 and ZnSnO3, respectively, with 16.66 % apparent quantum yield (AQY) under 365 nm monochromatic light. At the same time, the composites could also oxidize BA and yield up to 6.640 mmol g-1h-1n-benzylidene benzylamine (NBBA) with a 90.2 % selectivity. Due to the synergistic effect of Z-scheme’s built-in electric field and photothermal-pyroelectric of Fe0.9Ni0.1S2/ZnSnO3, the surface charges released on them could direct the charge transfer pathways and restrain their recombination with accelerated electron transfer kinetics, thus extending the carrier lifetime. This work offers a new perspective for designing electrical charge polarized by the photothermal-pyroelectric effect, which can enhance H2 evolution and BA oxidation concurrently.

Analysis and study of digital economy level measurement index

PurposeThis study aims to assess the level of development of the digital economy by constructing a comprehensive measurement system. It explores regional differences within China’s digital economy, highlighting the varying degrees of digital infrastructure, industrialization, governance and innovation capabilities across provinces.Design/methodology/approachA multidimensional analytical framework including digital infrastructure, industrialization, digitization, governance and innovation was developed. Entropy methods were used to calculate the weights of each dimension. The coupled coordination degree model and the Tobit model with random effects panel are applied to analyze the current situation, discrepancies and influencing factors.FindingsThis study reveals significant regional differences in the development of China’s digital economy, characterized by a pattern of “strong in the east, weak in the west; high in the south, low in the north.” This geographical imbalance exacerbates the “polarization effect” and the “siphon effect,” where resources and growth tend to concentrate in already developed areas, further intensifying regional inequalities. The development of the digital economy is driven by principles of innovation, coordination and sharing, which facilitate the creation and dissemination of new technologies and collaboration across different sectors. However, this progress is also constrained by considerations of environmental sustainability (green) and economic openness.Originality/valueThis paper contributes to the body of knowledge by providing a novel multidimensional measurement system for the level of digital economy development. The unique application of the coupled coordination degree model and Tobit model to analyze regional differences and influencing factors provides insights into the dynamics of China’s digital economy.

Electromigration in Cu–Cu joints: Measurement of activation energy and polarity effect

Electromigration (EM) has been a pivotal reliability challenge for interconnects, but there are only few studies on EM in Cu–Cu joints. In this work, accelerated EM tests for the Cu–Cu joints were conducted at three temperatures (150 °C, 179 °C, and 208 °C) and the temperature-dependent failures were discussed. The polarity effect of the grain growth behaviors at the bonding interfaces was observed at the opposite electron flows, which may be attributed to the difference in EM-build-up stress conditions and the divergence in atomic fluxes. Moreover, the activation energy (Ea) extrapolated from the three EM temperatures was derived as 0.9 eV. As compared to the solder joints with same dimensions, the Cu–Cu joints possess more than ten times of time-to-failures (TTFs) under the same EM condition.