A central challenge in spintronics is the development of materials for efficient spin-polarized current generation. While crystalline Heusler alloys often fall short of predicted half-metallicity due to structural disorder, their amorphous analogs present a promising avenue. In this work, we investigate how the composition-dependent structural evolution of short-range order controls room temperature electronic transport in amorphous FexSi1−x (0.44 ≤ x ≤ 0.75) alloy thin films. This structural evolution, revealed by X-ray reflectivity, underpins a transition from hopping to metallic conduction across distinct amorphous phases (FeSi → Fe2Si → Fe3Si). In the FeSi-like phase region, electronic transport is governed by Mott variable-range hopping, resulting in high resistivity and low Hall mobility. The onset of metallic conduction within the amorphous Fe2Si- and Fe3Si-like composition ranges yields lower resistivity alongside enhanced hole mobility. Our results establish a direct structure-property relationship in amorphous FexSi1−x alloys, demonstrating the ability to selectively design electronic transport through fine compositional tuning. Understanding the interplay between local atomic order and electronic transport in amorphous Fe–Si alloys provides key insights for engineering next-generation spintronic devices.
Nickel-based superalloys are widely deployed in high-pressure compressors and turbine rotors in various aeroengines. Developing advanced processing strategies is essential to boost the service performance of the alloy. In this work, molecular dynamics simulations based on the modified analytical embedded-atom method are performed to investigate the uniaxial tensile behaviors of γ/γ′ nanowires (NWs). The cross-sectional sizes of NWs range from 1.416 to 4.249 nm, and the simulation temperatures vary from 100 to 700 K. Cross-sectional size and temperature serve as key factors for surface activity, which in turn exerts a significant influence on the mechanical properties. The results obtained demonstrate that the mechanical properties increase exponentially with increasing cross-sectional size but decrease linearly with the rising temperature. Surface activity, including surface energy and surface thickness, acts as the driving force for dislocation or slip nucleation and is regulated by size and temperature. The critical size threshold for the transition of deformation mechanisms from crystal slip to twin formation is approximately 2.75 nm, as the size and temperature have a synergistic effect on the surface energy. The coupled effect of size, temperature, and surface, each of which imposes distinct regulatory roles, respectively, collectively governs the deformation behavior and mechanisms of NWs. In small NWs, deformation is primarily dominated by dislocation glide. By contrast, in larger NWs, plastic deformation is dominated by twin-mediated plasticity that impedes the dislocation movement and lattice glide. The study reveals the coupled size–temperature–surface effects on the deformation behaviors, which provides a theoretical foundation for the design of superalloys used in extreme environments.
Methane dissociation in low-pressure radio-frequency inductively coupled plasmas (RF-ICP) is governed by the coupled effects of electron energy distribution, excitation kinetics, and residence time. In this work, methane cracking is investigated in a low-pressure RF-ICP reactor with systematic variation of pressure and methane flow rate, while plasma behavior and reaction products are characterized using optical emission spectroscopy, residual gas analysis, and X-ray photoelectron spectroscopy. The results reveal an optimal operating regime near 1 × 10 −2 mbar, where sufficient electron density is maintained without excessive collisional damping, enabling efficient vibrational excitation, methane dissociation, and hydrogen formation. Under these conditions, enhanced dissociation pathways lead to a methane conversion of approximately 63%, maximized hydrogen formation, and an estimated minimum specific energy cost of ∼64 kJ/mol H 2 , while the formation of C 2 hydrocarbons is suppressed. Increasing methane flow rate reduces residence time and vibrational excitation, resulting in weakened plasma activation and lower hydrogen yield despite increased feed availability. Surface analysis confirms the formation of hydrogenated amorphous carbon (a-C:H) with mixed sp 2 /sp 3 bonding, consistent with plasma-assisted methane dissociation and solid-carbon formation. These findings demonstrate how pressure- and flow-controlled energy transfer mechanisms govern methane dissociation and product selectivity in RF-ICP plasmas.
Magnesium hydrides offer superior theoretical hydrogen storage capacities; however, their practical implementation is severely constrained by sluggish sorption kinetics. This study employs first-principles density functional theory (DFT) to elucidate the atomistic mechanisms governing hydrogen interaction with Mg(0001) surfaces, incorporating clean, vacancy-containing, Ti-doped, and Ti-M (M = Nb, V, Zr) co-doped configurations. Two-dimensional potential energy surface mapping reveals that H2 dissociation on pristine Mg(0001) is kinetically hindered by a 0.95 eV activation barrier along the bridge site (90,150). Substitutional Ti-doping significantly enhances surface reactivity, reducing this barrier to 0.25 eV, thereby functioning as a potent catalyst for hydrogen activation. Despite this catalytic benefit, nudged elastic band calculations identify a critical "dual role" for transition metal dopants: while Ti facilitates surface dissociation, it introduces a substantial subsurface kinetic trap characterized by a secondary migration barrier of 0.897 eV. Conversely, surface vacancies act primarily as diffusion promoters; although they increase the surface dissociation barrier to 1.10 eV, they facilitate hydrogen entry by lowering the initial penetration barrier to 0.328 eV. Projected density-of-states analysis confirms that Ti d-states provide the requisite orbital flexibility for facile dissociation but simultaneously induce localized stabilization that arrests long-range mobility. We demonstrate that Ti-V co-doping optimizes the energetic landscape, effectively mitigating Ti-induced trapping by restoring the subsurface barrier to 0.220 eV. This investigation identifies a fundamental Sabatier-type trade-off between surface activation and bulk transport, providing a robust theoretical framework for the strategic design of Mg-based storage materials.
Interaction of the first few deposited atomic layers with the substrate plays an important role in the growth and morphology of very thin films of metals and semiconductors. Self-assembled monolayers (SAMs) of organic molecules have a wide range of applications, from molecular electronics to immobilization of biomolecules. SAMs of organic molecules can be used to control the morphology, electrical, magnetic, and optical properties of overgrown metals and semiconductors. Here we report the thickness-dependent variation in the morphology and the optical properties of ZnO deposited by RF sputtering on the SAM of 1-octadecanethiol (ODT) and 16-mercaptohexadecanoic acid (MHA) grown on Au/Si. Morphology of ZnO thin films deposited on the SAM strongly depended on the organic functional group of the SAM. Uniformly distributed clusters, like the formation of ZnO, were observed when deposited on ODT, whereas a uniform thin film of ZnO was grown when deposited on MHA SAM. Band gap of deposited thin films depends on the thickness and morphology of the deposited ZnO.
Despite the interest in cellulose nanofibers for bioelectronic applications, limited research on transistors has been reported. In this study, we introduce n-type cellulose metalsemiconductor field-effect transistors (MESFETs) based on the Schottky junction effect using cellulose nanofibers from kenaf and broadleaf. In comparison with conventional highly pi-extended aromatic organic semiconductors, the Hall effect of kenaf and broadleaf revealed carrier mobilities of 55.1 and 15.6 cm2/Vs, respectively, which are two orders of magnitude higher. Their electrical resistivities of 5.80 & times; 107 and 6.71 & times; 107 Omega cm, which are two and ten orders of magnitude lower, respectively. The cellulose MESFET exhibits advantageous properties for significant amplification under negative gate voltages and a high on/off ratio under positive gate voltages. At Vg = 3 V, the on/off ratio reached 1.825, which is relatively favorable compared to that of ferroelectric polymer semiconductor devices. The proposed MESFET shows substantial potential for future applications in flexible and sustainable paper-based electronic devices.
Methods that could enable the generation of plasmas in air, at atmospheric pressure, and with the ability to precisely target where and when the plasmas are created are of great interest to domains such as fuel combustion. In this study, we show experimentally that this can be achieved by focusing nanosecond pulses through time reversal (TR) on split-ring resonator initiators. The choice of the TR signal determines the initiator on which the plasma is created. The role of the initiator in reaching the required gas breakdown field, the influence of the TR pulse duration and the electrical signature of the plasma on the received signal are also briefly investigated.
Accurate characterization of thin films with complex surface roughness requires precise modeling of both the film and its interfaces. In ellipsometry, surface roughness can be described using Bruggeman, Lorenz-Lorenz, or Maxwell-Garnett effective medium approximations (EMAs). Here, we adopt the Maxwell-Garnett EMA because it provides a simple yet physically meaningful representation of a composite air/material layer, accurately accounting for the volumetric fraction of inclusions while remaining computationally efficient. The model comprises two roughness sublayers atop a dense SiO2 layer, each represented as an air/SiO2 mixture with decreasing volume fractions according to Maxwell-Garnett theory. The substrate optical constants are known, and the dense layer is described using a fixed Lorentz model. Ellipsometric intensities (Is and Ic) are computed via the transfer matrix method (TMM) in MATLAB and treated as simulated data. A genetic algorithm (GA) is used to invert these data and extract key opto-geometrical parameters, including the dense layer's refractive index, layer thicknesses, and porosity fractions. Results show that the multilayer EMA combined with GA enables more accurate and robust parameter retrieval, particularly for complex roughness profiles. The approach is experimentally validated on a resin thin film deposited on a silicon substrate, providing a reliable framework for optical characterization of rough thin-film surfaces.
Non-thermal plasma (NTP) technology is effective for oxidation of atmospheric elemental mercury. This study focuses on the critical power supply parameters, including voltage, frequency, and pulse width, in a nanosecond pulsed corona discharge system and systematically investigates their influence on both Hg0 oxidation and ozone generation under varying discharge conditions. Experimental results demonstrate that increasing the pulse voltage significantly enhances the discharge intensity and the generation of reactive species, thereby raising the Hg0 oxidation rate to above 90%. Increasing the discharge frequency leads to a higher overall energy input per unit time and further improves Hg0 oxidation efficiency, although the energy per pulse reduces slightly. But changing the pulse width in the range of 400-2000 ns, the Hg0 oxidation rate exhibits only minor variation, remaining nearly constant at approximately 90%. These findings provide a theoretical basis and parameter optimization strategy for the industrial application of non-thermal plasma in atmospheric mercury pollution control.
In this paper, a novel Gate and Drain side Field plate AlGaN/GaN HEMT (GDFP-HEMT) is proposed, featuring multiple vertical field plates on the gate side and both vertical and horizontal field plates on the drain side. This new configuration of the HEMTs improves the electric field distribution and device performance in comparison to the conventional AlGaN/GaN HEMT (C-HEMT). The device structure includes a carbon-doped GaN buffer layer to enhance electrical isolation and reduce leakage currents, along with Al2O3 as a dielectric under the gate. Simulations using TCAD-Silvaco and VICTORY DEVICE software were performed to optimize field plate design and analyze its impact on key device parameters such as electron concentration, current density, and breakdown voltage. Results show that the proposed GDFP-HEMT achieves improved current handling, reduced electric field peaks, and a significant increase in breakdown voltage, reaching up to 900 V. The analysis confirms that careful design of the field plates, including their placement and configuration, plays a crucial role in enhancing the performance of AlGaN/GaN HEMTs.
Eu 3+ doped NaLaMgWO 6 red phosphors were prepared by solid state sintering method. The electronic structures of the phosphors are evaluated through density functional theory calculation. The band structure and density of states are studied. Y 3+ or Lu 3+ ions were adopted to enhance the luminescence properties of the red phosphors. When excited at 465 nm, these phosphors present strong red emission at 618 nm. The octahedral distortion leads to the improvement of the luminescence performance of the NaLaMgWO 6 : Eu 3+ phosphors. The photoluminescence intensity at 150 °C is 77% of that at room temperature. The chromaticity coordinates of prepared phosphors are in the red region and near the standard value for red color. These results indicate that this series of tungstate phosphors can serve as a potential red emitting material for lighting devices.
In spectroscopic ellipsometry, the selection of an appropriate dispersion model is essential for accurate optical parameter extraction. Traditional approaches rely on fixed dispersion laws chosen based on prior knowledge, which can lead to suboptimal or biased results. We propose a novel Hierarchical Genetic Algorithm (HGA) framework that autonomously selects the optimal dispersion model from a set of candidates, without requiring a priori assumptions. The method maintains a computational cost comparable to that of classical genetic algorithms (CGA), while offering the added advantage of exploring multiple models simultaneously through a hierarchical structure. Simulations on a silica layer deposited on a silicon substrate under known thickness conditions demonstrate excellent agreement with theoretical values (fitness between 10 −3 and 10 −6 , refractive index errors below 0.1%). Experimental validation on silicon samples confirms the effectiveness of the HGA, yielding results consistent with conventional methods, but without the need for predefined model selection. This approach significantly enhances the flexibility and reliability of ellipsometric characterization.
Wireless power transfer systems, particularly those based on inductive coupling, provide an increasingly attractive way to deliver power without any physical connection or cables. There exists now a large literature about the topic, but generally each paper focuses on a single application and/or a typical design procedure or modeling technique. Since the covered published works belong to a variety of approaches, it can be a difficult task to understand the underlying physical aspects and modeling approaches, particularly for a newcomer to the field. This tutorial paper reviews and describes basic aspects required to model an inductive power transfer system, with a focus on practicality. The article is based on the author's work over a period of 10 yr. It introduces and explains the published methods and principles relevant to all aspects of an inductive link, such that no specific prior knowledge about wireless power transfer is required. The objectives can be divided into three main contributions: 1) To provide fundamental equations and basic principles of inductive power transfer, which are required to begin a design process; 2) To present these typical applications related to three levels of transferred power: electric vehicle (high power); drone (mid power) and biomedical implant (low power) to describe a large overview of practical systems; 3) To give newcomers to the topic an introduction to the modeling process and key aspects to facilitate any design process.
Long-term storage of colloidal solutions presents significant challenges in maintaining the physical and mechanical properties of manufactured products over extended periods. Ensuring stability is critical for agro-alimentary products, pharmaceutical formulations, and petroleum applications to preserve product quality and longevity during storage. Monitoring the stability of colloidal dispersions is essential for anticipating potential degradation over time. This study explores the evaluation of stability criteria using quasi-surface resonant analysis. Specifically, the zeta potential of colloidal solutions is investigated via resonant optical parameter, the Free Spectral Range (FSR), to distinguish between stable and unstable dispersions. For this purpose, sensors based on organic UV210 Micro-Resonators (MRs) were fabricated using deep UV photolithography. These MRs were integrated into an optical test platform, enabling real-time data collection with a spectrometer and dedicated MATLAB processing. The study focuses on black carbon nano powders dispersed in water and in water plus an anionic surfactant (Sodium Dodecyl Sulfate, SDS). The findings show that unstable solutions exhibit an increasing FSR over time, which is indicative of sedimentation, whereas stable dispersions maintain a constant FSR. These results are validated through complementary rheological and zeta potential measurements, establishing a clear correlation between FSR variations and colloidal dispersion stability. This study demonstrates the potential of resonant optical measurements as a novel tool for assessing colloidal dispersion stability, functioning as a "zetameter" on a surfacic platform.
A theoretical model of a Si-implanted GaAs MESFET has been developed by considering a Gaussian impurity distribution within the semiconductor channel beneath the gate. The effect of electrical activation of the implanted impurities due to annealing has been incorporated to derive the effective doping distribution and thereby to calculate the drain current and threshold voltage of the device. A general mathematical formulation for the electrical activation of dopants has been proposed for Si implantation in GaAs. The impact of annealing temperature on the device performance has been rigorously studied and corresponding results are reported. It is observed that the drain current and threshold voltage of the device at post anneal condition shows a notable dependence on the activation ratio of the implanted ions. The device current usually improves with activation ratio whereas threshold voltage reduces with it. The maximum drain current and minimum threshold voltage were obtained at an annealing temperature of 800K, where the activation ratio was found to be the highest. The device performance has also been studied with respect to other implantation parameters such as projected range, projected straggle and implantation dose. In addition to the implantation defects, the impact of interface states and interfacial layers at the gate contact have been considered and their impact on device performance has been systematically studied. It is also observed that the drain current and threshold voltage shift by approximately 15.62 mA and 0.935 V, respectively, when interface state density is doubled from 1012 ev-1 cm-2 to 2 x 1012 ev-1 cm-2.
Polymethyl methacrylate (PMMA) is an important plastic in society and museum collections. In heritage collections it is often important to clean and conserve items. Since ethanol is potentially a green solvent with low toxicity, it is of fundamental value to study the interactions between PMMA and ethanol. PMMA is also used extensively for micro- and nanofabrication, for example as a negative photoresist or electron beam resist. Understanding the interaction between PMMA and ethanol at the nanoscale, particularly over extended periods of contact, could yield a deeper understanding of the technologies realizable with this versatile polymer.
This study examines the structural, electronic, and thermoelectric properties of trigonal-phase copper germanium phosphide (CuGe2P3) using density functional theory (DFT) calculations. The bulk modulus is 68.98 GPa with a pressure derivative of 4.53, obtained from the Birch-Murnaghan equation of state based on energy-volume data. This is lower than the 86.7 GPa reported for the disordered zincblende phase, indicating significant structural differences. Thermoelectric transport properties were evaluated at 100, 300, and 500 K. At 100 K, strong p-type transport with high Seebeck coefficients was observed, highlighting pronounced low-temperature electronic sensitivity. Using a representative lattice thermal conductivity, the estimated figure of merit zT reaches similar to 0.29 at 500 K, suggesting moderate thermoelectric performance. These results demonstrate that CuGe2P3 combines favorable structural stability with promising transport behavior, making it a potential candidate for mid-temperature thermoelectric applications.
Electric current can be used to assist the forming of metallic materials and actuate/excite electromechanical structures. In the heart of current-assisted forming and actuation/excitation is the electrothermal interaction from electric-Joule heating. In this work, we analyze the electrothermal problem of a finite cylindrical conductor with the passing of an alternating current under a weak skin effect at steady state. Closed-form solution is derived for the spatiotemporal evolution of the temperature in the finite cylindrical conductor, which consists of time-independent temperature and time-dependent temperature. Both the time-independent temperature and time-dependent temperature are proportional to the power input to the cylindrical conductor and decrease slightly with increasing the distance to the axisymmetric axis of the cylindrical conductor. The time-independent temperature reaches maximum at the center of the finite cylindrical conductor. The time-dependent temperature exhibits cyclic change with time, which depends on the angular frequency of alternating current and geometrical dimensions of the finite cylindrical conductor. The largest cyclic variation of the time-dependent temperature appears near the ends of the finite cylindrical conductor. The analytical solutions derived in this work can be used to analyze the temperature evolution in a finite cylindrical conductor under the action of a periodic current in different forms, such as a square or triangular form.
This study delves into the electronic, structural, magnetic, and ferromagnetic properties of RbZnF3 perovskite. We explored both the pure state and configurations doped with V, Cr, Mn, Ni, and Cu atoms at a concentration of 5% in the Zn position. To achieve this, we perform KKR-CPA combined with GGA. The ferromagnetic stability of RbZn0.95Cr0.05F3 and RbZn0.95Cu0.05F3 is observed, where (Cr, and Cu)-3d is set on the spin-down of E-F connected to the half metallicity. In the case of RbZn0.95TM0.05F3 alloy, the TM-3d states show a variation in the exchange splitting (t(2g)(+), t(2g)(-)). The configuration that is predicted by the charge state is closer to the V2+ configuration, in which 3 electrons occupy t(2g)(+). In the examination of the RbZn0.95Mn0.05F3 alloy, we discover that an indirect coupling is indicated by the hybridization of the Mn-3d and F-2p orbitals between -0.22 and -0.08 Ry.
