Hasil untuk "Electric apparatus and materials. Electric circuits. Electric networks"

Huan Wei, Jing Guo, Heng Liu et al.

Abstract Thermal stability is crucial for doped organic semiconductors (OSCs) and their applications in organic thermoelectric (OTE) devices. However, the capacity of n‐dopants to produce thermally stable n‐doped OSC films has not been thoroughly explored, with few reports of high thermal stability. Here, a novel n‐dopant, phosphazenium tetrafluoroborate (P2BF4) is introduced, which effectively induces n‐doping in N2200, P(PzDPP‐CT2) and several other commonly used OSCs. Remarkably, the electrical conductivity of P2BF4‐doped OSC films remains almost unchanged even after heating at temperatures > 150 °C for 24 h, far superior to the films doped with benchmark N‐DMBI. The exceptional thermal stability observed in P2BF4‐doped P(PzDPP‐CT2) films allows for stable operation of the corresponding organic thermoelectric devices at 150 °C for 16 h, a milestone not previously achieved. This study offers valuable insights into the development of n‐dopants capable of producing OSCs with outstanding thermal stability, paving the way for the practical realization of OTE devices with enhanced operation stability.

Farzin Asadi

Farzin Asadi

Måns J. Mattsson, Kham M. Niang, Jared Parker et al.

Abstract The complete subgap defect density of states (DoS) is measured using the ultrabroadband (0.15 to 3.5 eV) photoconduction response from p‐type thin‐film transistors (TFTs) of tin oxide, SnO, and copper oxide, Cu2O. The resulting TFT photoconduction spectra clearly resolve bandgaps that show the presence of interfacial and oxidized minority phases. In tin oxide, the SnO majority phase has a small 0.68 eV bandgap enabling ambipolar or p‐mode TFT operation. By contrast, in copper oxide TFTs, an oxidized minority phase with a 1.4 eV bandgap corresponding to CuO greatly reduces the channel hole mobility at the charge accumulation region. Three distinct subgap DoS peaks are resolved for the copper oxide TFT and are best ascribed to copper vacancies, oxygen‐on‐copper antisites, and oxygen interstitials. For tin oxide TFTs, five subgap DoS peaks are observed and are similarly linked to tin vacancies, oxygen vacancies, and oxygen interstitials. To achieve desirable unipolar p‐mode TFTs, the conduction band‐edge defect density of oxygen interstitials must be sufficiently large to suppress n‐mode conduction. In both channel materials, the metal vacancy peak densities near the valence band edge determine the hole concentrations, which then predict the TFT Fermi level energy, observed on‐off ratios, and threshold voltages.

Gyeong Min Seo, Jeong Wook Kim, Byoung Don Kong

ABSTRACT Bilayer MoS2 exhibits bandgap narrowing under a vertical electric field due to inversion symmetry breaking, with the extent of reduction scaling proportionally with field strength. Leveraging this intrinsic property, this study investigates its impact on the performance of bilayer MoS2 Schottky barrier field‐effect transistors, with a particular focus on the role of Schottky barrier height reduction in improving subthreshold swing. Density functional theory calculations quantify field‐dependent shifts in the conduction and valence band edges, which are integrated into transport simulations considering thermionic emission and tunneling at the metal‐semiconductor interface, as well as drift‐diffusion in the channel. The barrier height reduction achieves a subthreshold swing of 44.7 mV/dec in a bilayer MoS2 FET with a 2 nm HfO2 gate dielectric, representing a 37.5% improvement. In a CMOS inverter configuration, barrier height reduction leads to improvements in switching speed by up to 38% and reduces total power consumption by approximately 5%, demonstrating its effectiveness in enhancing both performance and energy efficiency.

Sijia Li, Yang Lu, Shenghao Jing et al.

All-solid-state batteries (ASSBs) have emerged as prominent research high ground for next-generation energy storage systems owing to intrinsic safety and high theoretical energy density. Among various solid-state electrolytes (SSEs) systems, sulfide SSEs are considered critical for surpassing the safety and energy density constraints of conventional liquid batteries, attributable to exceptional room temperature ionic conductivity (>10−3 ​S ​cm−1) and superior mechanical properties. Nonetheless, sulfide SSEs encounter several challenges. Limited chemical stability renders the sulfide SSEs prone to moisture-induced reactions that generate toxic H2S gas and cause structural degradation, thus necessitating stringent moisture control during processing. Moreover, the narrow electrochemical window triggered unexpected oxidation/reduction decomposition under extreme voltage conditions, leading to interfacial failure at both anode and cathode side. Additionally, the coarse-grained SSEs are not processable to build effective conductive network in the electrodes. In order to improve the practicality of sulfide SSEs, appropriate surficial or bulk functionalization strategies towards sulfide SSEs is essential to overcome their intrinsic moisture sensitivity, narrow electrochemical window and the weakness on building conductive networks in the electrodes. This review delineates the prevailing issues and challenges associated with sulfide SSEs, systematically summarizes recent advances in the functionalization and modification mechanisms of the sulfide SSEs, and provides a thorough discussion on development trends and future prospects of SSEs functionalization, thereby offering valuable insights for the practical implementation of ASSBs.

V. R. Bilyk, R. M. Dubrovin, A. K. Zvezdin et al.

The idea to find a magnet that responds to an electric field as efficiently as to its magnetic counterpart has long intrigued people's minds and recently became a cornerstone for future energy efficient and nano-scalable technologies for magnetic writing and information processing. In contrast to electric currents, a control by electric fields promises much lower dissipations and in contrast to magnetic fields, electric fields are easier to apply to a nanoscale bit. Recently, the idea to find materials and mechanisms facilitating a strong and simultaneously fast response of spins to electric field has fueled an intense research interest to electromagnons in non-collinear antiferromagnets. Here we show that THz spin resonance at the frequency 0.165 THz in collinear antiferromagnet Cr$_{2}$O$_{3}$, which does not host any electromagnons, can be excited by both THz magnetic and electric fields. The mechanisms result in comparable effects on spin dynamics, when excited by freely propagating electromagnetic wave, but have different dependencies on the orientation of the applied THz electric field and the antiferromagnetic Néel vector. Hence this discovery opens up new chapters in the research areas targeting to reveal novel principles for the fastest and energy efficient information processing - ultrafast magnetism, antiferromagnetic spintronics, and THz magnonics.

Ming Sun, Xinhua Wang, Wei Cui

Sulfate-reducing Bacteria (SRB) corrosion is a serious threat to the safety of marine pipelines.To reveal the influence of the corrosion behavior of X60 pipeline steel in the presence of SRB cultured in seawater and mud from the East China Sea The corrosion behavior of X60 pipeline steel was studied with weight loss measurements, microstructure and membrane composition analysis, electrochemical measurements The corrosion rate in sterile seawater is 0.11 mm/y, whereas, in SRB-infested seawater, it increases by 245 % to 0.38 mm/y. In sterile sea mud, the corrosion rate is 0.15 mm/y, but in SRB-infested sea mud, it increases by 87 % to 0.28 mm/y. In the corrosive environment of seawater and mud in the East China Sea, SRB significantly accelerates the microbial corrosion of X60 pipeline steel. These findings provide theoretical guidance for further research on SRB corrosion mechanisms and corrosion control of marine pipelines.

Pjotrs Žguns, Nuh Gedik, Bilge Yildiz et al.

Abstract The highest ambient‐pressure Tc among binary compounds is 40 K (MgB2). Higher Tc is achieved in high‐pressure hydrides or multielement cuprates. Alternatively, are explored superconducting properties of binary, metastable sub‐oxides, that may emerge under extremely low oxygen partial pressure. The emphasis is on the rock‐salt structure, which is known to promote superconductivity, and exploring AlO, ScO, TiO, and NbO. Dynamic lattice stability is achieved by introducing metal and oxygen vacancies in the fashion of Nb1−xO1−x‐type structure (x = ¼). The electron‐phonon (e‐ph) coupling is remarkably large in Al1−xO1−x and Ti1−xO1−x (λ ≈ 2 at x = ¼), with Tc ≈ 35 K according to the Allen–Dynes equation. Significantly, the coupling strength is comparable to that in high‐pressure hydrides, yet, in contrast to hydrides and MgB2, the coupling is largely driven by low frequency phonons. Sc1−xO1−x and Nb1−xO1−x show significantly smaller λ and Tc. Further, hydrogen intercalation to boost λ and Tc is investigated. Only Ti1−x(O1−xHx) and Nb1−x(O1−xHx) are dynamically stable upon intercalation, where H, respectively, decreases and increases Tc. The effect of H doping on electronic structure and Tc is discussed. Altogether, the study suggests that metal sub‐oxides are promising compounds to achieve strong e‐ph coupling at ambient pressure.

Jorge Íñiguez-González, Hugo Aramberri

The experimental demonstration of electric skyrmion bubbles and the recent prediction of their Brownian motion have brought topological ferroelectrics close to their magnetic counterparts. Electric bubbles (e-bubbles) could potentially be leveraged in applications for which magnetic skyrmions have been proposed (e.g., neuromorphic computing). Yet, we still lack a strategy to create currents of e-bubbles. Here, using predictive atomistic simulations, we illustrate two approaches to induce e-bubble currents by application of suitable electric fields, static or dynamic. We focus on regimes where e-bubbles display spontaneous diffusion, which allows us to generate a current by simply biasing their Brownian motion. Our calculations indicate that e-bubble velocities over 25 m/s can be achieved at room temperature, suggesting that these electric quasiparticles could rival the speeds of magnetic skyrmions upon further optimization.

N. Saraswathi, T. Sasi Rooba, S. Chakaravarthi

Sentiment Analysis technique involves extracting the relevant information from Unstructured User Reviews (UUR) dataset fetched from online and classifying them into appropriate positive and negative comments for making decisions. In UUR, data may be in noisy state, irrelevant features exist which creates high dimensional feature space. To design an effective sentiment learning model, users are required to extract the most relevant sentiment features from UUR. To overcome the issue, we proposed a Linguistic rule based feature selection method for extracting and selecting the sentiment features for Sentiment Analysis as it improves the predictive performance of classification algorithms. The proposed novel feature selection method involves identifying the various sentiment features in the review dataset by using filtering methods such as POS tags, n-grams. In the ensemble model, where the Random Forest classification algorithm is trained for textual sentiment classification, the chosen sentiment feature sets are used. Finally, we test our approach using the real-time review dataset that was collected from a multitude of sources, and the results demonstrate prediction accuracy that is superior to that of existing Sentiment analysis techniques.

Francesca Rolle, Francesca Durbiano, Stefano Pavarelli et al.

Carbon dioxide (CO2) is the most important greenhouse gas generated by human activities. Its concentration has been growing in the atmosphere reaching a current annual average of 410 μmol mol−1. Reliable determinations of the atmospheric CO2 concentration are of great importance for the development of models used in climate change predictions. The production of reference mixtures of known composition is a key step for the achievement of reliable data for the monitoring of greenhouse gases in atmosphere.The present work deals with a comparison of two methods for gas mixtures preparation, the first based on the gravimetric preparation of gas mixtures in high pressure cylinders and the second based on dynamic dilution, for generating gas mixtures at the desired amount fraction online.Reference mixtures of CO2 can be used for the calibration of monitoring sensors, with various applications ranging from environmental monitoring to industrial process control.

Jiameng Nan, Yujing Zhang, Yu Xie et al.

Abstract A metasurface is a kind of ultrathin artificial composite composed of subwavelength elements with unique abilities in manipulating electromagnetic waves. However, the static nature of its conventional metallic/dielectric constituent material has limited its fixed functionality in narrow frequency ranges. The two‐dimensional carbon sheet, i.e., graphene, is a promising platform for effectively tuning the functionality as well as operation frequency band of metasurface. Here, the authors propose and demonstrate a kind of graphene hybrid metasurface for dual‐band extraordinary electromagnetic transmission (EET). The metasurface is composed of two graphene/metal hybrid resonators with EET properties. It is shown that the EET of the graphene hybrid metasurfaces can be tuned by increasing the bias voltage on the graphene from 0 to 3 V. Furthermore, it is found that the transmission amplitude and operating frequency band of EET can be controlled by changing the relative position and thus the coupling of the two graphene hybrid resonators. The proposed design strategy of the hybrid metasurfaces is promising for many applications based on active EM or optical modulations.

Matthias Moser, Mamta Pradhan, Mohammed Alomari et al.

In this work, multi-layer PECVD SiNx/SiNx and SiNx/SiOy passivations are developed featuring very high soft breakdown strength and tunable stress properties, which would allow for stress engineering and wafer bow minimization. AlGaN/GaN-on-Si wafers (150 mm) with very low initial bow (<5 μm) are processed in a CMOS compatible manner. The effect of the major processing steps, namely passivation and metal deposition, on the wafer bow is continuously monitored. In this process aimed at power devices, relatively thick passivation is needed (1.5 μm), which would induce very high stresses on the wafer if a single-layer deposition is applied. Hence, deposition of multiple layers is explored through mechanical modelling and simulation, leading to a stress-free passivation. The optimized multi-layer dielectric consists of two different SiNx single layers (referred to as T40 and R100), which have opposite stress properties, with T40 being tensile and R100 being compressive. By adjusting the thickness ratio of both layers and the number of total layers, mechanical stress within the multi-layer can be neutralized to achieve stress-free deposition. In addition, the optimization of the film properties includes the electrical properties of the passivation, and is designed primarily for high voltage applications. The developed SiNx/SiNx passivation has a soft breakdown strength with more than 8 MV/cm, and leakage currents below 1 nA/mm2 up to soft breakdown. After dielectric development, Schottky and MIS device characteristics with SiNx/SiNx multi-layers are characterized in DC and pulse mode measurements. As measurements suggest, the developed passivation is suitable for GaN-on-Si HEMT applications.

Jan C. Balzer, Clara J. Saraceno, Martin Koch et al.

Terahertz (THz) systems open up the possibility of new applications of electromagnetic waves. Enormous bandwidths up to several terahertz enable the development of powerful spectroscopy systems that can provide insights into the structure and material of objects with micrometer resolution. New high power and compact THz time-domain spectroscopy (TDS) systems will be presented. The wide bandwidth also enables high-resolution imaging under far-field conditions to analyze arbitrary objects from a distance. In addition, a near-field system-on-a-chip imaging system is presented that achieves a resolution of 10 &#x03BC;m. Additionally, the application of terahertz waves presents challenges due to the low transmit power of the sources, high attenuation in free space, and the high noise figures of the receivers. These challenges can be overcome by antennas with high gain. Since - depending on the application - spatial scanning or focusing in a time-varying direction is required, beam steering is an essential component of many THz systems. In terms of communications, terahertz carrier frequencies offer wide bandwidths, enabling correspondingly high data rates of 100 Gbit&#x002F;s and more. As a result, the frequency bands between 250 GHz and 450 GHz have already been identified and&#x002F;or allocated for communication services and are being discussed as a component of 6G mobile communications. Concepts and demonstrations for 6G terahertz mobile communications will be presented. The high bandwidth of terahertz waves can also be used for high-accuracy indoor localization.

Yu‐Hsiang Hsueh, Ashok Ranjan, Lian‐Ming Lyu et al.

Abstract In this study, the effect of stacking faults (SFs) on electromigration in silver nanowires (AgNWs) in particular, with respect to their effects on necking and void growth, is investigated. The galvanic replacement reaction is used to synthesize the AgNWs in bulk at low cost. By varying the concentration of silver nitrate, AgNWs are obtained with and without SFs. In situ TEM analysis provides strong evidence that the SFs can effectively suppress the migration of surface atoms. Furthermore, an investigation of the void growth process reveals that SF facets parallel to the {111} plane contribute to the anisotropic change in morphology and slow down the rate of void growth by 135 times. Thus, planar defects can be beneficial to extending the lifetimes of devices by causing intrinsic changes to the material properties.

J. Nithyashri, Ravi Kumar Poluru, S. Balakrishnan et al.

This research proposes an IoT based technique for predicting rainfall forecast in coastal regions using a deep reinforcement learning model. The proposed technique utilizes Long Short-Term Memory (LSTM) networks to capture the temporal dependencies between the rainfall data collected from the coastal regions and the prediction model parameters. The proposed technique is evaluated on a dataset of rainfall data collected from the coastal regions of India and compared to traditional methods of rainfall forecasting. The accuracy and reliability of these models are evaluated by comparing them to prior models. Precipitation in coastal locations may be predicted with an average accuracy of 89% using the suggested model, as shown by the results. The suggested framework is computationally efficient and can be trained with little input. The results of this research give strong evidence that the proposed model is an effective tool for coastal precipitation forecasting.

Christoph Birkenhauer, Georg Korner, Patrick Stief et al.

Radar target simulators are not only a critical tool for verifying and testing radar systems but also play an important role in supporting the development of self-driving cars. Advances in radar sensors and techniques raise the required specifications for these units, increasing their complexity and cost. This article presents a novel and universal concept for radar target simulators that addresses these issues by responding only to the transmitted signal of a radar sensor during a fraction of the time, therefore modulating the average of the signal. This offers advantages for three independent use cases, which may be combined. First, the dynamic range and resolution of simulated target echo power can be improved even for existing systems. Second, the simulation of multiangle scenarios with a single backend is possible with this approach. Finally, hardware complexity and power consumption can be reduced. The proposed concept is examined extensively for frequency-modulated continuous wave radar, and design decisions are made. The theoretical considerations are validated with measurements with a real radar target simulator showing an improvement of up to <inline-formula><tex-math notation="LaTeX">$30 \,\mathrm{dB}$</tex-math></inline-formula> in the dynamic range with no observable negative side effects.

Alessio Zaccone, Vladimir M. Fomin

The supercurrent field effect is experimentally realized in various nano-scale devices, based on the superconductivity suppression by external electric fields being effective for confined systems. In spite of intense research, a microscopic theory and explanation of this effect is missing. Here, a microscopic theory of phonon-mediated superconductivity in thin films is presented, which accounts for the effect of quantum confinement on the electronic density of states, on the Fermi energy, and on the topology of allowed states in momentum space. By further accounting for the interplay between quantum confinement, the external static electric field, the Thomas-Fermi screening in the electron-phonon matrix element, and the effect of confinement on the Coulomb repulsion parameter, the theory predicts the critical value of the external electric field as a function of the film thickness, above which superconductivity is suppressed. In particular, this critical value of the electric field is the lower the thinner the film, in agreement with recent experimental observations. Crucially, this effect is predicted by the theory when both Thomas-Fermi screening and the Coulomb pseudopotential are taken into account, along with the respective dependence on thin film thickness. This microscopic theory of the supercurrent field-effect opens up new possibilities for electric-field gated quantum materials.

Felix Jung, Malte Schröder, Marc Timme

The adoption of battery electric vehicles (BEVs) may significantly reduce greenhouse gas emissions caused by road transport. However, there is wide disagreement as to how soon battery electric vehicles will play a major role in overall transportation. Focusing on battery electric passenger cars, we here analyze BEV adoption across 17 individual countries, Europe, and the World, and consistently find exponential growth trends. Modeling-based estimates of future adoption given past trends suggests system-wide adoption substantially faster than typical economic analyses have proposed so far. For instance, we estimate the majority of passenger cars in Europe to be electric by about 2031. Within regions, the predicted times of mass adoption are largely insensitive to model details. Despite significant differences in current electric fleet sizes across regions, their growth rates consistently indicate fast doubling times of approximately 15 months, hinting at radical economic and infrastructural consequences in the near future.