Hasil untuk "Plasma engineering. Applied plasma dynamics"

Xing Han, Yangyang Fu

In extreme ultraviolet (EUV) lithography, high-energy photon pulses generate transient plasmas and thus can degrade lithography system performance. This study investigates the dynamics of EUV-induced plasma adjacent to an electrostatic chuck, with a focus on the coupling mechanism between the plasma and the applied electric field. First-principle particle-in-cell simulations demonstrate that photoelectron emission serves as the dominant mechanism for electron production during an EUV pulse. Concurrently, electron-induced secondary emission significantly alters the potential distribution and electron density within positively biased regions, thereby modulating local plasma density. The space charge separation and the associated distortion of the electric field lead to anomalous electron and ion energy distributions, which in turn enhance ion sputtering on ruthenium surfaces. During the post-EUV-pulse phase, ion-induced secondary electron emission becomes the dominant source of electrons, sustaining the plasma during its gradual decay. The applied electric field established between the grounded blade and the reticle surface facilitates the extraction and loss of ions, thereby accelerating local ion density decay. Spatiotemporal electron and ion energy distribution functions and ion fluxes indicate that the EUV-induced plasma transitions from a photoionization-dominated to a sheath-controlled state. These findings provide deep insights into the evolution of EUV-induced plasmas and enhance the understanding of particle sputtering-induced damage under coupled conditions, laying the foundation for improving pattern fidelity and process stability in nanolithography.

Louis Saugé, G. Gaborit, Antoine Rousseau

This work presents an experimental study of ionization wave propagation in a helium plasma jet ignited with a 500 ns pulsed high voltage operating with and without a secondary grounded electrode. Fast camera imaging is coupled with non-perturbative electric field measurements using a Pockels effect-based probe to analyse the ionization front (IF) dynamics. By subtracting the Laplacian electric field components, both radial and axial electric field components generated by the plasma jet are extracted and their temporal evolution is determined. The presence of a grounded electrode is shown to double the IF propagation length and induce restrikes in the inter-electrode region, as evidenced by characteristic drops in the radial electric field component. The axial evolution of the radial electric field and IF velocity is reported, together with their correlation as a function of applied voltage.

G. Arora, Petr Bílek, Jiří Fujera et al.

In this study, we investigated time- and space-resolved plasma emissions generated by reflected high-voltage (HV) pulses in deionised water to determine the electron density. HV pulses with a 3.5 ns rise time and 160 kV amplitude were applied in a point-to-plane electrode geometry under single-shot conditions. The primary pulse, delivered to the chamber through a coaxial cable, produced a series of reflected pulses owing to load mismatch. Optical emission characteristics were recorded and resolved spatio-temporally across visible and near-infrared spectral regions. High-speed images showed that the primary discharge was diffuse, whereas the reflected pulses produced filamentary plasma structures. Imaging spectrometry revealed that the primary pulse generated a continuous spectrum with higher intensity away from the anode apex, while the reflected pulses exhibited broadened hydrogen and oxygen atomic lines superimposed on the continuum. These reflected pulses were analysed to estimate electron density and temperature under both space- and time-resolved conditions. The continuum was first removed by fitting its profile, and the resulting residuals were used to extract plasma parameters. Electron density ( ne) was determined from the broadened spectral lines, and electron temperature ( Te) was obtained from Boltzmann plots. The density decayed over time (from 2.5 to 0.5×1019 cm−3) while remaining roughly constant along the anode axis, whereas the electron temperature remained stable at 2–3 eV across space and time. The emergence of additional Balmer-series lines at higher reflections signalled ionisation threshold depression during the early reflections. Overall, this study provides the first consistent experimental evidence of the extreme conditions generated during nanosecond discharges in liquid water.

Mostafa M. A. Khater

Osama A. Marzouk

In the current study, we present a mathematical and computational fluid dynamics (CFD) model for simulating open-cycle linear Faraday-type continuous-electrode channels of magnetohydrodynamic (MHD) power generators, operating on combustion plasma. The model extends the Favre-averaged Navier–Stokes equations to account for the electric properties of the flowing plasma gas and its reaction to the applied magnetic field. The model takes into account various effects, such as the Lorentz force, turbulence, compressibility, and energy extraction from the plasma, and it adopts an electric potential technique along with the low magnetic Reynolds number (Rem) approximation. The model is numerically implemented using the multiphysics open-source computer programming environment “OpenFOAM,” which combines the finite volume method (FVM) and the object-oriented programming (OOP) concept. The capabilities of the model are demonstrated by simulating the supersonic channel of the large-scale pulsed MHD generator (PMHDG) called “Sakhalin”, with the aid of collected data and empirical expressions in the literature about its tested operation. Sakhalin was the world’s largest PMHDG, with a demonstrated peak electric power output of 510 MW. Sakhalin operated on solid-propellant plasma (SPP), and it had a single supersonic divergent Faraday-type continuous-electrode channel with a length of 4.5 m. We check the validity of the model through comparisons with independent results for the Sakhalin PMHDG. Then, we process our three-dimensional simulation results to provide scalar characteristics of the Sakhalin channel, one-dimensional profiles along the longitudinal centerline, and three-dimensional distributions in the entire channel. For example, we show that the temperature does not change significantly along the Sakhalin PMHDG, with the outlet mass-averaged temperature being 2738.4 K, which is close to the inlet value of 2750 K. Similarly, we find that the outlet mass-averaged absolute pressure is 3.294 bar, which is near the inlet value of 3.28 bar. On the other hand, the plasma is largely decelerated from an axial speed of 2050 m/s at the inlet to 1156 m/s at the outlet (mass average). Thus, the produced pulse electric energy is primarily extracted from the kinetic energy of the plasma, rather than from its thermal energy or its pressure energy. The resolved volume-average Lorentz force density vector is [− 89.12, 28.83, 0] kN/m3, and the resolved volume-average electric-current density vector is [1.462, − 4.517, 0] A/cm2. The presented OpenFOAM solver has several applications, including preliminary design of novel geometric shapes for MHD channels, exploration of the influence of various parameters on the performance of MHD power generators (such as the inlet Mach number, the inlet pressure, and the applied magnetic-field flux density), and estimating the residual energy contained in the exit plasma for proper identification of a downstream bottoming power cycle to extract some of this available energy. Aside from the presented OpenFOAM solver, we also provide an overview of various PMHDG systems. This study can benefit different research communities, particularly those interested in OpenFOAM applications, computational fluid dynamics (CFD), magnetohydrodynamics (MHD), open-cycle MHD generators, or multiphysics mathematical modeling.

Chenzi Lu, Shaofeng Xu, Y. Mei et al.

The auxiliary pulse voltage on the discharge dynamics of ionization wave in atmospheric pressure plasma jet is investigated by both experimental and numerical methods. The distribution of electrical potential is modified by the introduction of auxiliary pulse voltage. The velocity and intensity of ionization wave in terms of plasma bullet is enhanced by reducing the amplitude of auxiliary pulse voltage. The uniformly distributed electron and ion density are obtained by raising the amplitude of auxiliary pulse voltage. By reducing the amplitude of auxiliary pulse voltage, the ion and electron density are concentrated in the ionization wave front, which improves the radial electric field and expands the radial size of plasma bullet. It shows that the electric field, the ion and electron density, and the electron temperature can be enhanced by elevating the amplitude difference between the internal and the applied auxiliary electrical potential.

Mariska Schalk, C. T. Ryan, Bas Coppus et al.

During plasma–liquid interactions, understanding the production of electric potential at the interfacial region is important to further understand the development of various effects driven by the discharge, such as ionization, electric field, and the induced forces and flows. This study aims to characterize this electric potential development on the liquid surface through experimental methods. A helium AC kHz powered plasma jet and positive/negative pulsed jets, with a dielectric barrier discharge geometry, are investigated in contact with de-mineralied water and a NaCl 50 g l−1 solution, in both floating and grounded configurations. A voltage probe is used to obtain surface potential data over different distances from the plasma jet. This data is supported by intensified charge coupled device (iCCD) imaging to determine the moment of contact between the discharge and the liquid surface and by examining the discharge shape. For floating liquids, surface potentials were uniform over the surface, pointing toward high conductivity of the interfacial layer of water. For grounded liquids, efficient charge dissipation results in potentials that go to zero. Increasing the applied voltage amplitude, frequency and pulse width increases the surface potential. We are able to demonstrate that the surface potential measured outside of the active plasma region increases following plasma ignition towards a steady state. Apart from the usual bullet formation, the iCCD images show a diffuse volume discharge in the gas gap and a surface discharge for the pulsed jets, of which the shape depends on the liquid conductivity. An additional surface discharge is observed at the fall of the voltage pulse, which is expected to contribute to the neutralization of the surface charges.

M. Klich, David A Schulenberg, S. Wilczek et al.

This study investigates electron dynamics in three distinct discharge modes of a cross-field atmospheric pressure plasma jet: the non-neutral, quasi-neutral, and constricted modes. Using a hybrid Particle-In-Cell/Monte Carlo Collisions simulation, we systematically vary the applied voltage and driving frequency to explore these modes and their transitions. At low power, the discharge operates in a non-neutral mode, characterized by near-extinction behavior, analogous to the chaotic mode in other plasma devices. As power increases, the plasma transitions to a quasi-neutral mode, exhibiting the Ω- and Penning-mode heating mechanisms, similar to the bullet mode in parallel-field jets. At high power, the discharge enters a constricted mode, where plasma density increases significantly, and the discharge contracts toward the electrodes along the entire channel. Experimental validation using phase-resolved optical emission spectroscopy confirms the existence of the constricted mode as a distinct operational regime. These findings provide deeper insights into discharge mode transitions, contributing to the optimization of atmospheric pressure plasmas for various applications.

V. Velliangiri, D. Vasu, M. Ramkumar et al.

This study aims to enhance 3D‐printed poly‐ε‐caprolactone (PCL) scaffolds for bone tissue engineering. For this purpose, an amine‐rich coating was applied on the surface of the scaffold using nonthermal atmospheric plasma polymerization of allylamine. The applied potential (16, 18, and 20 kV) and flow rates (2, 4, and 6 lpm) were explored with respect to the surface properties of the plasma‐polymerized PCL scaffolds. A variety of characterization techniques were employed to examine the samples, including X‐ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM), and contact angle (CA) assessments. The findings from XPS indicated that elevated potentials enhanced the incorporation of amine functional groups. Images obtained via atomic force microscopy (AFM) and scanning electron microscopy (SEM) demonstrated a notable augmentation in surface roughness with increased discharge potentials. Contact angle measurements showed considerable improvement in hydrophilicity for the surface‐modified PCL scaffolds. Moreover, from in vitro investigation, it was found that the scaffolds modified with high retention of monomeric functionalities demonstrated significant cell‐compatible properties. Conclusively, this work establishes the fact that this new technique of plasma polymerization can improve the surface properties of PCL scaffolds, and by appropriate selection of operating parameters, amine coatings could be optimized to enhance the cytocompatibility of the PCL scaffolds.

Yang Wan, Chuanke Li, Wei Lu et al.

Donghyeon Seo, Seunghyun Baik, Seongsik Jeong et al.

Keisuke Enomoto, Jun Taniguchi

Effective high-aspect-ratio molds that minimize vacuum processes are becoming increasingly important for producing metalenses and other devices. To fabricate a high-aspect-ratio structure, a metal film must be used as a mask for dry etching, typically achieved via vacuum deposition. To avoid this vacuum process, we devised a method to develop an etching mask in the air using silver ink. The manufacturing method involved filling the mold with silver ink, baking it, removing silver from the convex parts of the mold with a polyethylene terephthalate film, and placing silver from the concave parts of the mold on top of the ultraviolet (UV)-cured resin using ultraviolet-nanoimprint lithography. The transferred pattern had silver on the convex parts, which was used as a mask for the oxygen dry etching of the UV-curable resin. Consequently, high-aspect-ratio resin shapes were obtained from three types of nano- and micromolds. Additionally, a high-aspect-ratio resin with silver was used as a replica mold to form a silver pattern. This process is effective and allows high-aspect-ratio patterns to be obtained from master molds.

Tilemachos Georgakopoulos, Georgios Samourgkanidis, Nadia Todorova et al.

Titanium dioxide nanoparticles were synthesized via hydrothermal treatment of tetrabutyl titanate in sulfuric acid, with controlled reaction times (10 h and 24 h) and zinc sulfate as a modifier. XRD confirmed exclusive formation of the anatase phase, with longer reaction times promoting crystallite growth. SEM and BET analyses showed that introducing Zn during synthesis suppressed agglomeration, decreased the particle size, and modified porosity while maintaining the mesoporous nature of all samples. UV–Vis diffuse reflectance spectroscopy showed a band gap near 3.2 eV, which was unaffected by Zn content or morphology. Photoconductivity studies showed a several-orders-of-magnitude increase in conductivity under vacuum conditions, especially in samples heat-treated for 24 h, due to the generation of oxygen vacancies and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mi>Ti</mi><mrow><mn>3</mn><mo>+</mo></mrow></msup></semantics></math></inline-formula> states that prolong the carrier lifetime. In particular, the TS24Z8 sample exhibited a photoconductivity enhancement of five orders of magnitude relative to its dark conductivity and nearly 30 times higher than that of the commercial P25 benchmark. In contrast, in air, photoconductivity remained low because of strong surface recombination with adsorbed oxygen. These results emphasize the critical influence of hydrothermal duration and zinc incorporation on the defect structure and electronic response of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>TiO</mi><mn>2</mn></msub></semantics></math></inline-formula>, offering insights for improved photocatalytic and optoelectronic applications.

Ilias Georgiopoulos, Dimitra Giasafaki, Dia Andreouli et al.

Atmospheric plasma spraying was used to create composite coatings employing mixed alloy matrices supplemented with carbon-based solid lubricants as feedstock materials. The current study’s goal was to examine the tribological properties of these coatings and explore the potential benefits of using CNTs as a nano-additive to minimize wear and friction while enhancing lubrication conditions in tribosystems such as piston ring–cylinder liner systems. Pin-on-disk measurements are used to correlate the chemical composition of feedstock materials with the friction coefficient and wear rate during coating operation. The enhanced behavior of the produced coatings is investigated. The anti-wear performance of Co-based cermet and metal alloys coatings, as well as the enhanced lubrication conditions during operation, are shown. In-depth discussion is provided regarding how the features of the feedstock powder affect the quality and performance of the produced coatings. The results showed that coatings based on the CoMo alloy exhibited an increase in wear due to CNT agglomeration. In contrast, CNT addition led to an improvement in bonding strength by up to 33%, a reduction in wear rate by up to 80%, and a decrease in the coefficient of friction from approximately 0.70 to 0.35 in CoNi cermet coatings. These findings demonstrate the role of CNTs in coating performance for demanding tribological applications.

Nishita Thakrar

This research analyzes Foreign Portfolio Investment (FPI) trends in India’s equity and debt markets from 2019 to 2024. It examines the macroeconomic and global factors influencing FPI flows and their impact on India’s financial landscape. The study highlights notable fluctuations in FPI inflows and outflows, driven by geopolitical tensions, monetary policy shifts, and global uncertainties, including the COVID-19 pandemic. Through statistical analysis, the research identifies key patterns and correlations between FPI movements and domestic economic indicators such as interest rates, exchange rates, and market capitalization.

Zary Adabavazeh, Amir Hossein Shiranibidabadi, Mohammad Hossein Enayati et al.

This research discusses the fabrication of a nickel matrix nanocomposite reinforced with in situ synthesized layered Ni₃Al intermetallics using mechanical alloying (MA) and spark plasma sintering (SPS). In contrast to ex situ methods that frequently produce weak interfaces, the in situ approach enhances bonding and mechanical performance by using layered Ni₃Al reinforcements with excellent deformation resistance and load-bearing potential. Twenty-hour milled Ni-Al powders were annealed at 700 °C and consolidated using SPS, achieving approximately 96% theoretical density. The nanocomposite showed exceptional mechanical properties, with a hardness of 350 ± 15 HV in contrast to 200 ± 5 HV for pure Ni, along with higher wear resistance and reduced wear track depth. These improvements resulted from microstructural refinement and the development of hard intermetallic phases. X-ray diffraction (XRD) and transmission electron microscopy (TEM) confirmed the formation of a homogeneous layered Ni₃Al structure inside the matrix, showing a crystallite size of around 40 nm post-milling. Layered reinforcements enhanced matrix–reinforcement interactions, thereby minimizing common challenges in traditional composites. This innovative production technique highlights the future potential of Ni₃Al-reinforced nanocomposites as high-performance materials for advanced engineering applications, combining outstanding mechanical and tribological properties with strong structural integrity.

N. Udrea, M. Mitu, A. Scurtu et al.

The dynamics of cylindrical nylon dust particles levitated in radio frequency (RF) argon plasma were studied using a plane-parallel discharge geometry. The influence of an external magnetic field of 14–19.5 mT applied using a coil on the lower RF electrode was assessed based on experimental laboratory observations. The crystal structure and dynamics of the particles were examined in the presence of a magnetic field and after switching it off. In the absence of the field, the particles maintained a stable configuration. When the magnetic field was applied, the particles exhibited complex dynamics driven by ion flow resulting from electric and magnetic field interactions. Two distinct behaviors emerged: strongly coupled particles moved collectively in a crystal-like, rotating structure under radial ion forces. Meanwhile, particles at the structure’s edge escaped, following individual, cycloidal trajectories around the long axis. The nonspherical shape of the particles induced a nonuniform charge distribution, which significantly influenced their dynamics. Analysis revealed that the escaping particles experienced a weaker dust–dust Coulomb force compared to the dominant ion drag force. These findings demonstrate the pivotal role of particle shape and competing forces in regulating collective and individual dynamics within magnetized dusty plasmas.

Yinghua Liu, Peiqi Yin, Dawei Liu et al.

A two-dimensional axisymmetric self-consistent fluid model was established using COMSOL Multiphysics to investigate the dynamics behavior of pulsed-DC helium plasma jet enhanced by an additional floating electrode. Comparative analysis of the Laplacian electric field without and with the floating electrode shows that the floating electrode allows for an intensified electric field inside the tube, which gives rise to the higher number density of electrons and ions before the formation of plasma sheath in the initial stage of streamer development. Subsequently, with the floating electrode applied, the increase of surface charge density in the early stage of streamer development raises the ion flux to the dielectric wall and reduces the sheath potential, finally resulting in the growth of electron energy in the plasma sheath and the electron number density in the plasma channel, before the plasma jet is ejected from the tube. When the plasma jet runs out of the tube, the floating electrode leads to the remarkable improvement of the energy deposition and the significant enhancement of the deposited power, which effectively elevates the electric field and the electron energy in the streamer head. Accordingly, the accelerated impact ionization and promoted streamer propagation increase the number densities of various species and extend the jet length in the later stage of streamer development.

Momchil Shopov, K. Milanov, M. Neznakomova et al.

Poly(vinyl alcohol) (PVA) nanofiber mats were electrospun while systematically varying applied voltage, tip-to-collector distance, and solution properties to define a reproducible processing window for future plasma surface activation. Fiber morphology and diameter distributions were quantified using scanning electron microscopy (SEM) and automated analysis in ImageJ. Reducing applied voltage and increasing flight distance, in combination with tuned viscosity and high electrical conductivity, led to finer and more uniform fibers. The study provides practical guidance for controlling fiber size and stability in PVA electrospinning and establishes a baseline for subsequent plasma modification to enhance surface hydrophilicity and cell adhesion.

Yeongsun Lee, Pavel Aleynikov, Peter de Vries et al.

In cold weakly-ionized plasmas, Dreicer generation mechanism can be non-diffusive as demonstrated in [Y. Lee et. al. Phys. Rev. Lett. 133 17 175102 (2024)]. By expanding the previous letter, we present the detailed description of a proper collision operator to precisely account for the non-diffusive electron kinetics. The operator appropriately combines the Fokker-Planck operator and Boltzmann operator where free-bound collision cross sections are valid in low energy region. The proposed operator is envisaged to predict runaway electrons generations in cold weakly-ionized plasmas, particularly to design a runaway-free reactor tokamak startup.