Field Effect Research Articles

Statistical and numerical analysis of magnetic field effects on laminar natural convection heat transfer of nanofluid in a hexagonal cavity

This paper presents a statistical and numerical investigation that examines the optimization and sensitivity analysis of the unsteady laminar natural convective heat transfer flow of Fe3O4-water nanofluid in a hexagonal cavity considering the impacts of a sloping magnetic field in one-component nanofluid model. The inclined walls of the cavity are maintained at a constantly low temperature, while the bottom wall is uniformly heated. The upper wall, however, is regarded as adiabatic. The nanofluid thermal conductivity model incorporates the impact of Brownian motion. The Galerkin weighted residual finite element method has been employed to solve the governing dimensionless equations. The results are provided regarding the average Nu, streamlines, and isotherms. The study uses response surface methodology to analyze the sensitivity of parameters such as the Ha, Ra, and nanoparticle volume percentage. Using a response surface policy allows for optimizing the process and identifying the most favorable circumstances to achieve the maximum thermal transfer rate. The flow pattern of the nanofluid is significantly affected by the magnetic field and its alignment. The numerical results indicate a significant rise in the average Nu as the nanoparticle volume percentage, magnetic field inclination angle, nanoparticle type factor, and Ra increase. Conversely, the Hartmann number and the nanoparticle's diameter have contrasting effects. When considering Brownian motion, the average Nu grows by 225.89 % for Ra = 106 with ϕ = 0.03 and 25.28 % for the other case. The optimal condition for heat transfer occurs when Ra = 106, Ha = 4, and ϕ =0.03 while keeping the other parameters constant.

Field enhancement induced by surface defects in two-dimensional ReSe2 field emitters.

The field emission properties of rhenium diselenide (ReSe2) nanosheets on Si/SiO2 substrates, obtained through mechanical exfoliation, have been investigated. The n-type conduction was confirmed by using nano-manipulated tungsten probes inside a scanning electrode microscope to directly contact the ReSe2 flake in back-gated field effect transistor configuration, avoiding any lithographic process. By performing a finite element electrostatic simulation of the electric field, it is demonstrated that the use of a tungsten probe as anode, at a controlled distance from the ReSe2 emitter surface, allows the collection of emitted electrons from a reduced area that furtherly decreases by reducing the tip-sample distance, i.e. allowing a local characterization of the field emission properties. Experimentally, it is shown that the turn-on voltage can be linearly reduced by reducing the cathode-anode separation distance. By comparing the measured current-voltage characteristics with the numerical simulations, it is also shown that the effective field enhancement on the emitter surface is larger than expected because of surface defects. Finally, it is confirmed that ReSe2 nanosheets are suitable field emitters with high time stability and low current fluctuations.

First-Principles Investigation of Janus MgZnXY (X, Y = O, S, Se, Te; X ≠ Y) Monolayers for Short-Channel Field Effect Transistor

First-Principles Investigation of Janus MgZnXY (X, Y = O, S, Se, Te; X ≠ Y) Monolayers for Short-Channel Field Effect Transistor

Effect of magnetic field on the Bose–Einstein condensation of quantum well exciton–polaritons

We theoretically investigate the nonlinear effects of a magnetic field on the relaxation process of exciton–polaritons toward Bose–Einstein condensation in GaAs quantum wells. Our study reveals that the modification of the exciton’s effective mass, Rabi splitting, and dispersion significantly alters the relaxation rate of polaritons as they approach condensation. By employing a quasi-stationary pump, we clarify the dynamics of the total and condensed polariton populations in response to varying magnetic field strengths. Notably, we demonstrate that under low-energy pumping conditions, the presence of a magnetic field significantly suppresses condensation. This suppression is attributed to the decreased scattering rate between energy levels, which is a consequence of the reduced steepness in the high-energy dispersion. Conversely, increasing both the pump energy and the magnetic field can enhance relaxation efficiency, leading to a substantially larger number of condensed polaritons.

Band Versus Hopping Transport in Conducting Polymers by Ab Initio Molecular Dynamics: Exploring the Effect of Electric Field, Trapping and Temperature

Band Versus Hopping Transport in Conducting Polymers by Ab Initio Molecular Dynamics: Exploring the Effect of Electric Field, Trapping and Temperature

Linking Electronic and Structural Disorder Parameters to Carrier Transport in a Modern Conjugated Polymer.

Understanding charge transport in conjugated polymers is crucial for the development of next-generation organic electronic applications. It is presumed that structural disorder in conjugated polymers originating from their semicrystallinity, processing, or polymorphism leads to a complex energetic landscape that influences charge carrier transport properties. However, the link between polymer order parameters and energetic landscape is not well established experimentally. In this work, we successfully link statistical surveys of the local polymer electronic structure with paracrystalline structural disorder, a measure of statistical fluctuations away from the ideal polymer packing structure. We use scanning tunneling microscopy/spectroscopy to measure spatial variability in electronic band edges in PM6 films, a high-performance conjugated polymer, and find that films with higher paracrystallinity exhibit greater electronic disorder, as expected. In addition, we show that macroscopic charge carrier mobility in field effect transistors and and trap influence in hole-only diode devices is positively correlated with these microscopic structural and electronic parameters.

High-performance single-crystalline In2O3 field effect transistor toward three-dimensional large-scale integration circuits

Formation of a single crystalline oxide semiconductor on an insulating film as a channel material capable of three-dimensional (3D) stacking would enable 3D very-large-scale integration circuits. This study presents a technique for forming single-crystalline In2O3 having no grain boundaries in a channel formation region on an insulating film using the (001) plane of c-axis-aligned crystalline indium gallium zinc oxide as a seed. Vertical field-effect transistors using the single-crystalline In2O3 had an off-state current of 10−21 A μm−1 and electrical characteristics were improved compared with those using non-single-crystalline In2O3: the subthreshold slope was improved from 95.7 to 86.7 mV dec.−1, the threshold voltage showing normally-off characteristics (0.10 V) was obtained, the threshold voltage standard deviation was improved from 0.11 to 0.05 V, the on-state current was improved from 22.5 to 28.8 μA, and a 17-digit on/off ratio was obtained at 27 °C.

Characterization of bulk trap density using fully I–V-based optoelectronic differential ideality factor in multi-layer MoS2 FETs

Abstract Molybdenum disulfide (MoS2) has excellent optoelectronic properties, chemical stability, and a two-dimensional (2D) structure, making MoS2 a very versatile field-effect device material. Herein, we characterize MoS2 and utilize a photo-responsive I–V technique for extracting the energy distribution of the bulk traps in multi-layer MoS2 field effect transistors (FET). This method uses the differential ideality factor in both dark and light conditions. The differential ideality factor enables the efficient quantitative extraction of the device trap density by considering the nonlinear characteristics of the subthreshold region (V ON < V GS < V T). To accurately differentiate between the sub-bandgap traps and the interface traps near the conduction band, near-infrared light (λ= 1530 nm) optical illumination was used for the light state characterization. The bulk trap densities under dark state and light state conditions were derived for multi-layer (7-layer and 9-layer) MoS2 FET channels, and the influence of light illumination and overall multi-layer thickness on the bulk trap density was confirmed. The accurate extraction of the trap density enables the design of MoS2 FETs with long-term stability and high optoelectronic performance.

Review of External Field Effects on Electrocatalysis: Machine Learning Guided Design

AbstractExternal field‐enhanced electrocatalysis is a novel and promising approach for boosting the efficiency of electrocatalytic reactions, potentially achieving significant enhancement without altering the composition and structure of electrocatalysts. In addition, the scaling relations of electrocatalysis typically lead to similar variations of initial‐state and transition‐state (TS) energy, which minimally impacts the reaction energy barrier. A sophisticated design of the external field effects shall break these scaling relations. This review provides a comprehensive overview of current research on the effect of mechanical, electric, and magnetic fields on electrocatalysis. It meticulously details the mechanisms underlying activity enhancement based on external field regulations, spanning from the synthesis of electrocatalytic materials to their behavior during the reaction process and modulation of the electrolyte environment. Additionally, the applications of emerging machine learning (ML) technologies in electrocatalysis design, including machine learning interatomic potentials (MLIPs) to simulate large‐scale and dynamic chemical reaction processes, data‐driven design and optimization of electrocatalysis performance, are briefly reviewed. In addition, the significant potential of ML technologies in conjunction with external field regulation, envisioning them as effective tools for optimizing or reverse designing electrocatalysis, considering both thermodynamic and kinetic factors as well as the dynamic effect of electrocatalyst surfaces under extreme external fields, is highlighted.

Ultrathin Indium Tin Oxide Accumulation Mode Electrolyte‐Gated Transistors for Bioelectronics

AbstractElectrolyte‐gated field effect transistors and electrochemical transistors have emerged as powerful components for bioelectronic sensors and biopotential recording devices. A set of parameters must be considered when developing devices to amplify weak electrophysiological signals. These include maximum transconductance values, cut‐off frequencies, and large on/off current ratios. Organic polymer‐based devices have recently dominated the field, especially when considering flexibility as a key factor. Oxide semiconductors may also offer these features, as well as advantages like higher mobility. Herein, flexible, ultrathin, indium tin oxide (ITO) electrolyte‐gated transistors are reported. These accumulation‐mode devices combine n‐type operation with µe = 9.5 cm2 Vs−1, high transconductance (gm = 44 mS), and on/off ratios (105) as well as optically transparent layouts. While oxides are normally considered brittle, mechanically flexible ITO layers are obtained by room temperature deposition of amorphous layers onto parylene C. This process results in low strain, producing devices that survive bending. ITO electrochemically degrades, however, with cycling. To overcome this, the surface is passivated with high dielectric constant inert capping layers of Ta2O5 or Ta2O5/AlN. This greatly improves stability while preserving low gate voltages. Based on their overall performance, ITO‐based EGFETs are promising for bioelectronics.

Hybrid Quantum Mechanical, Molecular Mechanical, and Machine Learning Potential for Computing Aqueous-Phase Adsorption Free Energies on Metal Surfaces.

Performing reliable computer simulations of elementary processes occurring at metal-water interfaces is pivotal for novel catalyst design in sustainable energy applications. Computational catalyst design hinges on the ability to reliably and efficiently compute the potential energy surface (PES) of the system. Due to the large system sizes needed for studying processes at liquid water-metal interfaces, these systems can currently not be described using density functional theory (DFT). In this work, we used a hybrid quantum mechanical, molecular mechanical, and machine learning potential for studying the adsorption behavior of phenol, atomic hydrogen, 2-butanol, and 2-butanone on the (0001) facet of Ru under reducing conditions when Ru is not oxidized. Specifically, we describe the adsorbate and the surrounding metal atoms at the DFT level of theory. Here, we also considered the electrostatic field effect of the water molecules on adsorbate-metal interactions. Next, for the water-water and water-adsorbate interactions, we used established classical force fields. Finally, for the water-Ru surface interaction, for which no reliable force fields have been published, we used Behler-Parrinello high-dimensional neural network potentials (HDNNPs). Employing this setup, we used our explicit solvation for metal surface (eSMS) approach to compute the aqueous-phase effect on the low-coverage adsorption of selected molecules and atoms on the (0001) facet of Ru. In agreement with previous experimental and computational studies of oxygenated molecules over transition metal facets, we found that liquid water destabilizes the tested adsorbates on Ru(0001). Interestingly, our findings indicate that adsorbates on Ru are less affected by the presence of an aqueous phase than on other transition metals (e.g., Pt), highlighting the necessity of experimental investigations of Ru-based catalytic systems in liquid water.

Ground state magnetic structure and magnetic field effects in the layered honeycomb antiferromagnet YbOCl

YbOCl is a representative member of the van der Waals layered honeycomb rare-earth chalcohalide RChX (R = rare earth; Ch = O, S, Se, and Te; and X = F, Cl, Br, and I) family reported recently. Its spin ground state remains to be explored experimentally. We grew high-quality single crystals of YbOCl and conducted comprehensive thermodynamic, elastic, and inelastic neutron scattering experiments down to 50 mK. The experiments reveal an antiferromagnetic phase below 1.3 K which is identified as a spin ground state with an intralayer ferromagnetic and interlayer antiferromagnetic ordering. By applying sophisticated numerical techniques to a honeycomb (nearest-neighbor)–triangle (next-nearest-neighbor) model Hamiltonian which accurately describes the highly anisotropic spin system, we are able to simulate the experiments well and determine the diagonal and off-diagonal spin-exchange interactions. The simulations give an antiferromagnetic Kitaev term comparable to the Heisenberg one. The experiments under magnetic fields allow us to establish a magnetic field–temperature phase diagram around the spin ground state. Most interestingly, a relatively small magnetic field (∼0.3 to 3 T) can significantly suppress the antiferromagnetic order, suggesting an intriguing interplay of the Kitaev interaction and magnetic fields in the spin system. The present study provides fundamental insights into the highly anisotropic spin systems and opens a window to look into Kitaev spin physics in a rare-earth-based system. Published by the American Physical Society 2024

Tri‐Layer Heterostructure Channel of a‐IGZO/a‐ITZO/a‐IGZO Toward Enhancement of Transport and Reliability in Amorphous Oxide Semiconductor Thin Film Transistors

AbstractThin film transistors (TFTs) based on amorphous oxide semiconductors (AOS) are promising candidates for panel displays. However, the trade‐off between mobility and reliability in AOS‐TFTs hinders their further applications in next‐generation display techniques and newly developed logic and memory circuits. Here, a structural strategy is proposed for the mobility‐reliability trade‐off, via a triple‐layer channel containing a Ga‐free high‐mobility layer (amorphous InSnZnO, a‐ITZO) sandwiched by two Ga‐rich layers (amorphous InGaZnO, a‐IGZO) with higher reliability. Gate‐induced carrier accumulation is verified mainly being energetically confined within the high mobility a‐ITZO layer, at the newly defined a‐ITZO/a‐IGZO interface. Compared to single layer a‐ITZO‐TFTs, triple‐channel a‐IGZO/a‐ITZO/a‐IGZO TFTs (GTG‐TFTs) exhibit outstanding stability and electrical transport performances, with suppressed positive/negative‐bias‐stress voltage shifts from 1/0.3 to 0.1/0.004 V, enhanced field effect mobility from ≈40 to 56 cm2V−1s−1, and optimized sub‐threshold swing down to 80 mV dec−1. Further numerical simulations and charge transport characterizations, including magnetotransport and gate‐induced Hall effect, indicate that charge transport in tri‐layer structure is less affected by energetic disorders present at gate insulator interfaces.

Eco-friendly and Recyclable Liquid Metal Synthesis of Two-Dimensional Cr2O3 and CrN Nanosheets for Photoresponse and Field Effect Transistors

Eco-friendly and Recyclable Liquid Metal Synthesis of Two-Dimensional Cr₂O₃ and CrN Nanosheets for Photoresponse and Field Effect Transistors

Quantitative analysis of the effect of the magnetic field generated by a PET/MR scanner on positron range

Image quality in positron emission tomography (PET) is influenced by positron range. In this work, the effect of the magnetic field of a PET/MR Siemens Biograph mMR 3T on the quality of PET images was studied. Experimental measurements were conducted using18F and68Ga-filled phantoms to quantify image uniformity, recovery coefficients (RCs), spill-over ratios and percent contrast for spherical lesions. Tissue-equivalent phantoms (lung inhale and exhale, adipose, water, trabecular and cortical bone) were used together with a line source to quantify the impact of the magnetic field on the reconstructed PET images. A comparative analysis was made with images obtained with a PET/CT Biograph Vision 600, using the same radionuclides and phantoms. Higher RCs values were obtained when the image quality phantom was filled with68Ga and scanned with the PET/MR system compared to those obtained with the PET/CT scanner. Hot spheres in the lesion detectability phantom, appear contracted in the transverse direction in the PET/MR system, an effect more evident for68Ga compared to18F, but no elongation in the direction parallel to the magnetic field was observed. In the PET/CT scanner, radial profiles taken from axial slices of line sources, show longer distribution tails extending beyond 20 mm when filled with68Ga and placed inside lung-inhale tissue. In the PET/MR scanner the radial profiles of all materials collapsed into a single distribution with tails extending no more than 10 mm in the direction perpendicular to the magnetic field. Positron range depends on positron energy and material density in which they traverse. The results show an evident improvement in image quality in the transaxial direction only, particularly in phantoms filled with68Ga when using a PET/MR system as opposed to images acquired in the PET/CT system due to the presence of the magnetic field.

Computational fluid dynamics simulation of ammonia leakage scenarios during ship-to-ship bunkering

Ammonia is emerging as a potential marine fuel, yet its toxicity and risk of accidental leaks pose significant safety challenges compared to other alternatives. This study focuses on the critical ship-to-ship bunkering process using Computational Fluid Dynamics (CFD) simulations to analyse diverse ammonia leakage scenarios considering various leak orientations relative to the wind and the ships. The numerical setup was initially validated against controlled experiments, demonstrating satisfactory agreement. Results indicate that atmospheric ammonia dispersion is significantly influenced by obstacles like the superstructure and hull in the near field, with diminishing effect in the far field. Conventional Gaussian plume models are inadequate within the first few hundred metres from the release source due to the complex near-field flow patterns and increased turbulence generated by the wakes of the hull and superstructure. These findings underscore the necessity for improved ship-scale dispersion models to accurately evaluate the impact of obstacles on ammonia dispersion. The consequence analysis reveals that upward leaks create larger risk zones with potential for irreversible health effects, while horizontal leaks may expose personnel to life-threatening concentrations. Vertical leaks in crosswind configurations generate lethal zones covering tens of metres on deck. These results highlight the importance of considering the exact location of the transfer hose relative to the ship and all potential wind orientations in risk assessments. Given the extensive range of potential dispersion patterns and the inadequacy of conventional Gaussian dispersion models in this context, we strongly recommend vessel-specific CFD simulations before certifying ammonia bunkering operations as safe. This approach is crucial for accurate risk assessment at the ship scale, where complex geometries and multi-directional flows invalidate the assumptions of traditional point-source, uni-directional dispersion models.

Diatomic molecules embedded with Morse potential and under the effect of external fields

Diatomic molecules embedded with Morse potential and under the effect of external fields

A Novel Brillouin and Langevin Functions Dynamic Model for Two Conflicting Social Groups: Study of R&D Processes

We consider a two-group social conflict under the corporates’ research and development (R&D) business processes. Conflict participants are divided into two groups depending on their attitude to new ideas, technologies, and behavioral style for R&D creative problems—innovators and adapters. We reveal the contradiction that arises between the need to include both types of employees in one project team and their objectively antagonistic positions regarding the methods and approaches to R&D processes. The proposed research methodology is based on a modern post-non-classical paradigm formed on the principles of coherence, interdisciplinarity, openness, and nonlinearity, as well as a sociophysical approach to the social conflicts modeling. We use the general theories of magnetism, paramagnetism, and functions of P. Langevin and L. Brillouin to describe the dynamics of group participants’ preferences regarding the style of conflict behavior. The analogy of paramagnetism, consisting in the orienting effect of the magnetic field, is used to describe social groups interactions that have not only their own interests, but are also influenced by the opinions of opposite social groups. A two-dimensional, four-parameter map represents the dynamics of group conflict. Modeling results show that regardless of the initial states and with certain parameters of intra-group and intergroup interactions, the trajectories eventually converge to an attractor (limit cycle) in a two-dimensional space. No non-periodic or chaotic modes are identified in the two-group conflict, which determines the controllability of the described conflict. The results of the simulation experiments are used as decision support and contradictions resolution aimed at forming the required modes of the corporates’ research and development business processes and ensuring the group participants’ cohesion and depolarization. The results of testing the model at an industrial enterprise are presented.

Comparative study of magnetic field effect on fast plasma flow of heavy and light species investigated by spectroscopic measurement

Abstract To understand the effects of magnetic fields on the propagating plasma flows of heavy and light ion species, a laboratory-scale experiment was conducted using a pulsed-power discharge. The plasma drift velocity and electron temperature were estimated by time-of-flight and line-pair methods, respectively, using spectroscopic measurements. Ion current waveforms were measured using an ion collector. When a magnetic field was applied, the plasma drift velocity decreased and the electron temperature increased in both heavy and light plasmas. The magnetic Reynolds number, pressure balance between the plasma and magnetic field, and ion current waveforms show that heavy plasma has a high possibility of deforming the magnetic field and generating accelerated ions through interaction with the magnetic field.

Double modulation of the electric field in InGaAs/Si APD by groove rings for the achievement of THz gain-bandwidth product

Abstract Avalanche photodiode (APD) is commonly used as a receiver in optical communication and light detection and ranging (LIDAR), offering highly sensitive photodetection capabilities. A key strategy for improving the gain-bandwidth product (GBP) of the APD involves the optimization of the electric field distribution using the charge layer. However, traditional modulation methods to adjust the carrier transport and avalanche process using the charge layer often face challenges (inefficiency and non-uniformity). An InGaAs/Si APD based on the wafer bonding method with a GBP up to 1.03 terahertz (THz) is reported theoretically in this work. The charge layer and groove rings are inserted at the InGaAs/Si bonded interface to modulate the electric field in the APD effectively, demonstrating low dark current and reduced avalanche bias of the device. This approach induces a dramatic and rapid variation of the electric field at the interface while reducing the gradient of the electric field in the multiplication layer. Additionally, the indirect impact of the groove ring on mitigating the adverse effects of the lattice mismatch is pointed out, and the optimal doping concentration range of the charge layer is identified to enhance the modulation effect of the electric field for stronger impact ionization. These findings provide valuable insights for the next-generation InGaAs/Si APDs with high GBP for the high-speed data transmission.