Plasma Processing Research Articles

Neutral gas temperature of adamantane in a radio-frequency inductively coupled plasma electrothermal micro-thruster using optical emission spectroscopy

Abstract The gas temperature of adamantane plasma in a 13.56~MHz radio-frequency (RF) inductively coupled plasma was measured using optical emission spectroscopy. Rovibrational band fitting of the Second Positive System of nitrogen gas (N$_2$) from the addition of N$_2$ and Swan system of homo-nuclear carbons (C$_2$) from adamantane dissociation were used to obtain the gas temperature through the rotational temperature under the assumption of rotational-translational equilibrium. The measured temperature ranged from 400~K to 700~K, increasing with RF power range from 10~W to 100~W and adamantane flow rate from 0.25~mg~s$^{-1}$ to 1~mg~s$^{-1}$, with discharge pressures up to a few Torr. The energy released during adamantane dissociation contributed to a slight temperature increase compared to conventional pure N$_2$ plasma. Adding a large amount of helium (He) acted as a quencher, reducing the gas temperature. In an adamantane-He mixture, the gas temperature remained stable at mid-range power and at lower adamantane flow rates. Justification of gas temperature and a simple power balance model were described. Applications of adamantane spectroscopy include propulsion, plasma processing, and astrophysics, with the inclusion of future studies.

Engineering the Metal/Oxide Interfacial O‐Filling Effect to Tailor Oxygen Spillover for Efficient Acidic Water Oxidation

AbstractThe oxygen spillover on the metal/oxide electrocatalysts interface acts as an essential role in promoting the oxygen evolution reaction (OER) for proton exchange membrane water electrolyzers (PEMWEs). However, oxygen spillover mechanisms and corresponding regulatory strategies are still unclear for addressing slow OH‐migration kinetics. Herein, an interface is constructed between Iridium (Ir) and Niobium (Nb)‐doped Titanium oxide (TiO2) with abundant oxygen vacancies area by plasma processing, enabling oxygen spillover from the metal Ir to supports. The optimized Ir/Nb‐doped TiO2 with a significant OER activity (η = 253 mV) and durability in acids compared to commercial IrO2. In situ experiments combined with theoretical computations reveal the presence of interfacial oxygen vacancies not only regulates the Ir structure toward boosted activity but also constructs a directional spillover pathway from Ir to interfacial oxygen vacancies area and then TiO2 via the OH*‐filling route, which strikingly mitigates the OH* migration barriers. In addition, the optimized Ir/Nb‐doped TiO2 exhibits excellent performance (1.69 V/1.0 A cm−2@80 °C) and long‐term stability (≈500 h@1.0 A cm−2) with practical potential in PEMWEs. This work provides a unique insight into the role of oxygen spillover, paving the way for designing Ir‐based catalysts for PEMWEs.

Prospects of cold plasma in enhancing food phenolics: analyzing nutritional potential and process optimization through RSM and AI techniques

Consumption of plant-based food is steadily increasing and follows an augmented trend owing to their nutritive, functional, and energy potential. Different bioactive fractions, such as phenols, flavanols, and so on, contribute highly to the nutritive profile of food and are known to have a sensitivity toward higher temperatures. This limits the applicability of traditional thermal treatments for plant products, paving the way for the advancement of innovative and non-thermal techniques such as pulsed electric field, microwave, ultrasound, cold plasma, and high-pressure processing. Among these techniques, cold plasma would be an operative choice in plant-based applications due to their higher efficacy, greenness, chemical exclusivity, and quality retention. The efficiency of the plasma process in ensuring the bioactive potential depends on several factors, such as feeding gas, input voltage, exposure time, pressure, and current flow. This review explains in detail the optimization of process parameters of the cold plasma technique, ensuring greater extractability or retention of total phenols and antioxidant potential. Response surface methodology (RSM) is one of the common techniques involved in the optimization of these course factors. It also covers the convention of artificial intelligence-based methods, such as artificial neural networks (ANN) and genetic algorithms (GA), in evaluating the data on process parameters. The review critically examines the strengths of each optimization tool in determining the optimal process parameters for maximizing phenol retention and antioxidant activity. The ascendancy of these techniques was mentioned in the studies regarding fruit, vegetables, and their products, and they can also be applied to other food products.

Impedance matching assistance based on frequency modulation for capacitively coupled plasmas

The efficiency and repeatability of capacitively coupled plasma (CCP) processes are highly dependent on achieving precise impedance matching between the plasma load and the RF power supply. This paper presents a numerical investigation of the role of frequency modulation in enhancing impedance matching of RF CCPs, a technique that can be critical to maintaining operational efficiency and plasma stability. Through a detailed simulation approach, the research explores how variations in the driving frequency impact plasma characteristics and electrical parameters, particularly focusing on the CCP’s impedance behavior. The simulations demonstrate that when impedance matching is achieved at a fixed fundamental frequency of 13.56 MHz, changes in driving frequency will lead to reduced power coupling efficiency and increased reflection. The study introduces a frequency modulation strategy that allows us to re-establish high-quality impedance matching after changes of the plasma impedance occur, e.g., due to changes of the variable capacitor settings inside the matchbox or gas pressure, thereby improving the CCP’s performance. As the driving frequency can be adjusted electrically, adjusting the impedance matching by frequency modulation is much faster than based on mechanical adjustments of variable capacitors inside the matching and could, thus, allows quicker matching. The findings underscore the impact of frequency modulation on power absorption efficiency and highlight the sensitivity of impedance matching to driving frequency fluctuations. This study provides a foundation for further exploration into the optimization of RF CCP systems with the potential to enhance process control and plasma performance across a range of industrial applications, especially pulsed CCPs.

Integrated Biosensor with Microfluidic Chip and Microwave Sensor Chip for Cell Separation and Detection

AbstractIn this work, an integrated biosensor consisting of spiral microfluidic array and microwave sensors is proposed for simultaneous separation and detection of cells. The biosensor integrated by plasma processing technology is fabricated by soft lithography and glass‐based IC process, which has the advantages of simple preparation, low cost, and reliable structure. In the field of clinical medicine, Escherichia coli (E. coli) is the causative agent of urinary tract infections, which leads to an increase in the number of white blood cells (WBCs) present in the urine. Different concentrations of E. coli and WBCs mixed solution are configured to perform biological cell experiments and the capability of the biosensor in separating and detecting WBCs is verified. Interdigital capacitors (IDCs) and split ring resonators (SRRs) are employed to detect the WBCs obtained by microfluidic array separation. The microfluidic array exhibits a WBC collection rate of 92.7%. The capacitance of the IDC and the resonant amplitude of the SRR exhibit a decrease of 51.36 pF and 0.34 dB, which demonstrates a satisfactory linearity of 0.96 and 0.98, respectively. Consequently, the integrated biosensor used to simultaneously separate and detect WBCs has the potential for the early diagnosis of urinary tract infections in clinical medicine.

Machining Path Optimization of Inductively Coupled Plasma Based on Surface Heat Transfer Model

Inductively coupled plasma (ICP), a non-contact optical processing method, has been widely used in the preparation of fused quartz. However, the thermal effect during processing inevitably affects the stability of the removal rate, reduces the processing accuracy, and restricts the further development of plasma processing. This paper analyzes the critical temperature that affects the changes in plasma removal depth, establishes a heat transfer model for plasma jet processing through simulations, derives the heat conduction equation during processing, and obtains the critical radius corresponding to the critical temperature related to the processing speed. Additionally, this work analyzes the path temperature of the grating track used in processing and obtains the path temperature variation curve. Based on the critical radius, a staggered grating track was proposed, which verified that this track can effectively control the path temperature, thereby suppressing the error caused by the thermal effect of processing. This study not only helps to gain a deeper understanding of the heat transfer process in plasma machining, but also provides a basis for achieving high-precision plasma machining path optimization schemes.

MAGPIE: A Machine Learning Approach to Decipher Protein-Protein Interactions in Human Plasma.

Immunoprecipitation coupled to tandem mass spectrometry (IP-MS/MS) methods is often used to identify protein-protein interactions (PPIs). While these approaches are prone to false positive identifications through contamination and antibody nonspecific binding, their results can be filtered using negative controls and computational modeling. However, such filtering does not effectively detect false-positive interactions when IP-MS/MS is performed on human plasma samples. Therein, proteins cannot be overexpressed or inhibited, and existing modeling algorithms are not adapted for execution without such controls. Hence, we introduce MAGPIE, a novel machine learning-based approach for identifying PPIs in human plasma using IP-MS/MS, which leverages negative controls that include antibodies targeting proteins not expected to be present in human plasma. A set of negative controls used for false positive interaction modeling is first constructed. MAGPIE then assesses the reliability of PPIs detected in IP-MS/MS experiments using antibodies that target known plasma proteins. When applied to five IP-MS/MS experiments as a proof of concept, our algorithm identified 68 PPIs with an FDR of 20.77%. MAGPIE significantly outperformed a state-of-the-art PPI discovery tool and identified known and predicted PPIs. Our approach provides an unprecedented ability to detect human plasma PPIs, which enables a better understanding of biological processes in plasma.

Issue Information: Plasma Process. Polym. 01/2025

Issue Information: Plasma Process. Polym. 01/2025

Platinum nanoparticles wrapped in carbon-dot-films as oxygen reduction reaction catalysts prepared by solution plasma sputtering.

Fuel cells have become increasingly important in recent years because of their high energy efficiency and low environmental impact. However, key challenges remain in the widespread adoption of fuel-cell vehicles, including reducing Pt usage in catalysts and improving their durability. In this study, a high-performance Pt@carbon-dot-film core-shell catalyst was successfully synthesized using a nonequilibrium reaction field, i.e., solution plasma (SP) process, by adjusting the electrolyte pH. Four pH solutions (pH = 4.4, 7, 8, and 11) were employed as the discharge liquid environment for the SP process. The catalyst synthesized in the pH = 8 solution exhibited a mass activity of approximately 500 mA mg-1, which was twice as high as that of the commercial Pt/C catalyst (256 mA mg-1) with the same loading amount. The onset and half-wave potentials were 0.99 and 0.89 V, respectively, both of which exceeded those of commercial Pt/C catalysts (0.95 and 0.86 V, respectively). Furthermore, the enhanced catalytic performance corresponded to the Pt/C bonding between Pt and the carbon shell generated during the SP process.

Surface functionalization of fibrous material by roll-to-roll low pressure plasma processing

Surface functionalization of fibrous material by roll-to-roll low pressure plasma processing

Protective film on cerium metal through in-situ formation of a dense CeO2 oxide layer using air plasma

The rapid spontaneous oxidation of cerium in the atmospheric environment is reported to be attributed to its porous oxide structure, and there is a scarcity of strategies for enhancing its corrosion resistance. In this study, a dense ceria layer was fabricated in situ on the surface of cerium using a simple plasma process method, which significantly improved its resistance to drastic oxidation in air. By subjecting the cerium sample to plasma treatment in air for 400 s, a dense surface CeO2 layer with a thickness of approximately 1 μm was formed. Compared with untreated cerium metal samples, no significant changes were observed in terms of surface morphology and composition characteristics even after exposure to atmospheric conditions for up to 60 days. Theoretical calculations have demonstrated that the presence of a relatively stable CeO2 layer serves as an effective barrier against water adsorption/dissociation and particularly inward diffusion of hydrogen, thereby preventing their penetration into bulk cerium. The utilization of plasma method for generating a homogeneous surface oxide layer without introducing additional metal elements presents a novel strategy for protecting active metals exhibiting poor air corrosion resistance

Sterilization of blueberry juice under solution plasma process: Factors, quality, and its action mechanisms

Sterilization of blueberry juice under solution plasma process: Factors, quality, and its action mechanisms

Graphene Supported NiFe-LDH and PbO2 Catalysts Prepared by Plasma Process for Oxygen Evolution Reaction.

The development of efficient catalysts for water electrolysis is crucial for advancing the low-carbon transition and addressing the energy crisis. This work involves the fabrication of graphene-based catalysts for the oxygen evolution reaction (OER) by integrating NiFe-LDH and PbO2 onto graphene using plasma treatment. The plasma process takes only 30 min. Graphene's two-dimensional structure increases the available reaction surface area and improves surface electron transport. Plasma treatment further improves catalyst performance by facilitating nanoparticle attachment and creating carbon defects and sulfur vacancies. Density functional theory (DFT) calculations at the PBE provide valuable insights into the role of vacancies in enhancing catalyst performance for OER. The catalyst's conductivity and electronic structure are greatly impacted by vacancies. While modifications to the electronic structure increase the kinetics of charge transfer, the vacancy structure can produce more active sites and improve the adsorption and reactivity of OER intermediates. This optimization of intermediate adsorption and electronic properties leads to increased overall OER activity. The catalyst NiFe-PbO2/S/rGO-45, synthesized through plasma treatment, demonstrated an overpotential of 230 mV at 50 mA·cm-2 and a Tafel slope of 44.26 mV dec-1, exhibiting rapid reaction kinetics and surpassing the OER activity of commercial IrO2. With its excellent performance, the prepared catalyst has broad prospects in commercial applications such as water electrolysis and air batteries.

A Study on the Development of Real-Time Chamber Contamination Diagnosis Sensors.

Plasma processes are critical for achieving precise device fabrication in semiconductor manufacturing. However, polymer accumulation during processes like plasma etching can cause chamber contamination, adversely affecting plasma characteristics and process stability. This study focused on developing a real-time sensor system for diagnosing chamber contamination by quantitatively monitoring polymer accumulation. A quartz crystal sensor integrated with flexible printed circuit boards was designed to measure the frequency shifts corresponding to polymer thickness changes. An impedance probe was also employed to monitor variations in the plasma discharge characteristics. The sensor demonstrated high reliability with a measurement scatter of 2.5% despite repeated plasma exposure. The experimental results revealed that polymer accumulation significantly influenced the plasma impedance, and this correlation was validated through real-time monitoring and scanning electron microscopy (SEM). The study further showed that the sensor could detect the transition point of the plasma state changes under varying process gas conditions, enabling the early detection of potential process anomalies. These findings suggest that the developed sensor system can be crucial for diagnosing plasma and chamber conditions, providing valuable data for optimizing preventive maintenance schedules. This advancement offers a pathway for improving process reliability and extending the operational lifetime of semiconductor manufacturing equipment.

Characterizing Superflares in HR 1099 Using Temporal and Spectral Analysis of XMM-Newton Observations

Abstract In the present paper, we analyze three energetic X-ray flares from the active RS CVn binary HR 1099 using data obtained from XMM-Newton. The flare duration ranges from 2.8 to 4.1 hr, with e-folding rise and decay times in the range of 27–38 minutes and 1.3–2.4 hr, respectively, indicating rapid rise and slower decay phases. The flare frequency for HR 1099 is one flare per rotation period. Time-resolved spectroscopy reveals peak flare temperatures of 39.44, 35.96, and 32.48 MK, emission measures of 7 × 1053–8 × 1054 cm−3, global abundances of 0.250, 0.299, and 0.362 Z ⊙, and peak X-ray luminosities of 1031.21−32.29 erg s−1. The quiescent state is modeled with a three-temperature plasma maintained at 3.02, 6.96, and 12.53 MK. Elemental abundances during quiescent and flaring states exhibit the inverse-first ionization potential (i-FIP) effect. We have conducted a comparative analysis of coronal abundances with previous studies and found evidence supporting the i-FIP effect. The derived flare semi-loop lengths of 6–8.9 × 1010 cm were found to be comparable to the other flares detected on HR 1099; however, they are significantly larger than typical solar flare loops. The estimated flare energies, ranging from 1035.83−37.03 erg, classify these flares as super-flares. The magnetic field strengths of the loops are found to be in the range of 350–450 G. We diagnose the physical conditions of the flaring corona in HR 1099 through the observations of superflares and provide inference on the plasma processes.

Highly Air-Stable N-Doped Two-Dimensional Violet Phosphorus with Atomically Flat Surfaces.

Few-layer violet phosphorus (VP) shows excellent potential in optoelectronic applications due to its unique in-plane anisotropy and high mobility. However, the poor air stability of VP severely limits its practical applications. This article reports highly air-stable VP obtained by a two-step nitrogen plasma treatment where the nitrogen volume flow rate is controlled to coordinate physical etching and chemical doping. Specially, this plasma process can remove partial oxidations formed on the VP surface with barely etching to the intrinsic VP surface but efficiently incorporates nitrogen into VP, resulting in surface nitrogen-doped VP (N-VP) nanosheets with atomically smooth surfaces that exhibit excellent air stability. Atomic force microscopy images show that the N-VP nanosheet, nearing a monolayer thickness, maintained its surface morphology and flatness unchanged in ambient air for over 60 days. The improved stability of N-VP can be partly due to its atomically smooth surface, which reduces the number of active or oxidation sites. Further elucidation was made by density functional theory calculations, showing that this ultrastability may intrinsically be attributed to repairing P vacancies by N dopants. This research provides a feasible strategy for significantly enhancing the durability of VP.

Surface modification of fabrics using dielectric barrier discharge plasma for improved antifouling performance

Surface modification of fabrics is an effective way to endow them with antifouling properties while still maintaining their key advantages such as comfort, softness and stretchability. Herein, an atmospheric pressure dielectric barrier discharge (DBD) plasma method is demonstrated for the processing of silk fabrics using 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane (PFDS) as the precursor. The results showed the successful grafting of PFDS groups onto the surface of silk fabrics without causing damage. Meanwhile, the gas temperature is rather low during the whole processing procedure, suggesting the non-equilibrium characteristics of DBD plasma. The influence on fabrics of the processing parameters (PFDS concentration, plasma treatment time and plasma discharge power) was systematically investigated. An optimum processing condition was determined to be a PFDS concentration of 8wt%, a plasma processing time of 40 s and a plasma power of 11.87 W. However, with prolonged plasma processing time or enhanced plasma power, the plasma-grafted PFDS films could be degraded. Further study revealed that plasma processing of silk fabrics with PFDS would lead to a change in their chemical composition and surface roughness. As a result, the surface energy of the fabrics was reduced, accompanied by improved water and oil repellency as well as enhanced antifouling performance. Besides, the plasma-grafted PFDS films also had good durability and stability. By extending the method to polyester and wool against different oil-/water-based stains, the DBD plasma surface modification technique demonstrated good versatility in improving the antifouling properties of fabrics. This work provides guidance for the surface modification of fabrics using DBD plasma to confer them with desirable functionalities.

Development of blue-light GaN based micro light-emitting diodes using ion implantation technology

This study fabricated 10 μm chip size μLEDs of blue-light GaN based epilayers structure with different mesa processes using dry etching and ion implantation technology. Two ion sources, As and Ar, were applied to implant into the LED structure to achieve material isolation and avoid defects on the mesa sidewall caused by the plasma process. Excellent turn-on behavior was obtained in both ion-implanted samples, which also exhibited lower leakage current compared to the sample fabricated by the dry etching process. Additionally, lower dynamic resistance (Rd) and series resistance (Rs) were obtained with Ar implantation, leading to a better wall-plug efficiency of 10.66% in this sample. Consequently, outstanding external quantum efficiency (EQE) values were also present in both implant samples, particularly in the sample implanted with Ar ions. This study proves that reducing defects on the mesa sidewall can further enhance device properties by suppressing non-radiative recombination behavior in small chip size devices. Overall, if implantation is used to replace the traditional dry etching process for mesa fabrication, the ideality factor can decrease from 11.89 to 2.2, and EQE can improve from 8.67 to 11.03%.

Turbulent Energy Conversion Associated With Kinetic Microinstabilities in Earth's Magnetosheath

AbstractPlasma in Earth's magnetosheath rarely experiences interparticle collisions, so kinetic microinstabilities are thought to contribute to regulating the plasma thermodynamics. Instabilities excite waves and redistribute free energy in velocity space, reducing free energy in the velocity distribution function (VDF). Using 24 hr of data spread over 163 intervals of in situ magnetosheath observations by Magnetospheric Multiscale (MMS), we investigate signatures of energy conversion where the turbulent dynamics have locally distorted the VDFs into non‐Maxwellian shapes, in the context of electron and ion temperature anisotropy driven instabilities. We find enhanced average energy conversion into the particles along instability boundaries, suggesting turbulence plays a role in redistributing free energy. In so doing, we quantify the energetics associated with unstable conditions for both species. This work provides insight into the open question of how specific plasma processes couple into the turbulent dynamics, ultimately leading to energy dissipation and particle energization in collisionless plasmas.

­­­­­­Exploring surface diversification of polyvinyl alcohol/polyethylene glycol Composites by cold plasma: Ompact of Argon and oxygen plasmas on biomedical application

Tetraethyl orthosilicate was used as a crosslinker to create composites made of polyvinyl alcohol and polyethylene glycol (PVA/PEG (PP)). The composites were exposed to non-thermal plasma (NTP) treatment with an Argon and oxygen gas mixture. The NTP treatment resulted in an improvement in surface hydrophilicity. Physiographical investigations indicated surface nanotexturing, but bulk properties were unaffected. After twenty days of exposure to air, there was no detectable ageing effect, showing that the NTP-modified composites were extremely robust. The composites swelled more in intestinal pH than at gastric pH. The NTP-modified composites shown significant Biofilm eradication activity against E. coli. Plasma treated composites shown Greater antibacterial activity against E.coli and enterobacilous bacteria. Mechanical properties enhances with application of different carrier gases in the non-thermal plasma process. Release characteristics of the composites validated the controlled delivery of anticancer drug sulforaphane to the intestine. Biodegradability character increases for the plasma treated composites over the subsequent days. It was also discovered that the hydrogels were biodegradable. PVA/PEG composites treated with O and Ar plasma are therefore effective for a variety of biomedical applications.