Optical Emission Spectra Of Plasma Research Articles

Explore the growth mechanism of high-quality diamond under high average power density in the MPCVD reactor

Investigating the mechanism behind the high-efficiency deposition of high-quality diamond has always been a prominent topic in related research. This paper investigates the CH4-H2 plasma characteristics and related chemical reaction kinetics in the average power density range of 18–100 W·cm−3, which is a typical range for large-area diamond film deposition. The number densities of H, CH3 and C2H2 increase linearly with the average power density. C2H2 is the main hydrocarbon in the discharge, and CH3 is the main single-carbon hydrocarbon. The number density and radial uniformity of CH3 and C2H2 increase with the average power density, which is necessary for the high rate and uniform deposition of diamond films. The plasma's optical emission spectra indicate an acceleration in the C2 production rate at high power density. The diamond film deposition experiment demonstrates the efficacy of high average power density in achieving high-quality diamond deposition at a high growth rate.

First-principles simulation of optical emission spectra for low-pressure argon plasmas and its experimental validation

Various spectral line emissions are often used for the experimental characterization of low-temperature plasmas. For a better understanding of the relation between the plasma characteristics and optical emission spectra, first-principle numerical simulations for low-pressure radio-frequency driven capacitively-coupled plasmas (CCPs) of argon have been performed by coupling one-dimensional particle-in-cell/Monte Carlo collision (PIC/MCC) simulations with a global collisional-radiative model (CRM). The only ionization and excitation mechanisms included in the PIC/MCC simulations of this study are the electron-impact ionization and excitations of the ground-state Ar atoms, as done commonly, whereas the electron-impact ionization of metastable states and other ionization mechanisms are also included in the CRM to account for the optical emission spectra. The PIC/MCC coupled CRM provides the emission spectra, which are then compared with experimental data obtained from the corresponding Ar CCPs with a gas pressure ranging from 2 Pa to 100 Pa. The comparison has shown good agreement for pressures up to about 20 Pa but increasingly notable deviations at higher pressures. The deviation is ascribed to the missing consistency between the PIC/MCC simulations and CRM at higher pressures, where the ionization from the metastable states is more dominant than that from the ground states, indicating a significant change in the electron energy distribution function due to the electron collisions with excited Ar atoms at higher pressures.

Effects of operational parameters on plasma characteristics and liquid treatment of a DBD-based unipolar microsecond-pulsed helium atmospheric pressure plasma jet

A dielectric-barrier-discharge-based square unipolar microsecond-pulsed helium atmospheric pressure plasma jet (APPJ) was characterized by combining a simplified equivalent circuit model with a transferred charge (Q) measured by introducing an additional capacitance in series with the reactor. From Q-V plots, Cd and Ccell for DBD reactors under pulsed excitation were determined. Q-V plots were drawn for varying operational parameters, and the dissipated energy per cycle was evaluated. Operational parameters, such as the gas flow rate and pulse frequency, were varied, and the resulting changes in the plasma plume length, gas temperature, excitation temperature, discharge current, dissipated power, and optical emission spectra were examined. As an example of the application of the plasma jet, liquid media, including de-ionized water, were exposed to the APPJ, and their properties (pH and electrical conductivity) and concentrations of reactive species generated in the media were measured as functions of the operational parameters. Furthermore, changes in the plasma-activated media after storage for different durations and under different conditions were examined. The correlation between plasma characteristics and properties of plasma-treated liquid is discussed.

Effects of duty ratio on liquid- and polymer-surface treatment by a unipolar microsecond-pulsed helium atmospheric-pressure plasma jet

Effects of duty ratio of a unipolar microsecond-pulsed helium atmospheric-pressure plasma jet (APPJ) on liquid- and polymer-surface treatments were investigated. In addition, changes in the plasma plume length, gas temperature, excitation temperature, discharge current, absorption power, and optical emission spectra were examined by varying the other operating parameters, such as applied voltage and additive flow of oxygen or water vapor. As an example of liquid sample, de-ionized water (DW) was exposed to an APPJ, and the concentrations of the reactive species generated in the DW were measured as functions of the operating parameters. Polycarbonate, polypropylene, and polymethylmethacrylate were employed as exemplary substrate materials to investigate the effect of plasma treatment on polymeric surfaces. The APPJ treatment increased the surface energy and changed the wetting characteristics of the surface from hydrophobic to hydrophilic. X-ray photoelectron spectroscopy results showed that a short-time plasma treatment with He and/or He/O2, He/H2O affects the surface wettability owing to the introduction of polar groups.

Spectroscopic and Thermal Properties for Exploding Silver Wire Plasma in Deionized Water

The goal of this research is to use optical emission spectroscopy to investigate the parameters of exploding silver wire plasma. The silver discharge plasma's emission spectra were recorded and studied. For silver wire of diameter 0.4 mm and different currents 75,100, and 125A in deionized water, the plasma electron temperature ( ) was calculated by Boltzmann plot and container plasma medium temperature by thermal camera, and the electron density ( ) was computed by Stark broadening using the hydrogen (H line) at 656.279 nm With increasing current from 75 to 125 A, the electron density (ne) increased from 3.160× to 8.762× , while electron temperatures increased from 0.571 to 1.334 eV under the same conditions. The plasma's optical emission spectrum (OES) includes a peak at 653 nm that corresponds to the H line of the hydrogen atom, as well as additional peaks that belong to Ag (AgI and AgII lines). Researchers looked into the relationship between plasma electron temperature, emission line intensity, and number density. Nanoparticle concentration rises as the intensity of the emission line rises, while their size decreases. It is feasible to deduce that plasma parameters have a regulated relationship with the concentration and size of nanoparticles produced.

Effects of nonthermal plasma-activated water on the microbial sterilization and storage quality of blueberry

This study has presented the potential use of plasma-activated water (PAW) for the inactivation of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) inoculated on blueberries. The generation parameters of PAW were optimized to a voltage of 8 kV, a frequency of 14 kHz, a processing volume of 30 mL, and a processing time of 50 min. PAW treatments achieved significantly higher (p < 0.05) reductions than those obtained by water treatment in E. coli and S. aureus. As shown by propidium iodide and acridine orange staining, electron microscopy and optical emission spectra of plasma, the microbial inactivation of PAW was attributable to damage to the cell membrane and the denaturation of DNA induced by reactive oxygen species produced from plasma. During storage, PAW treatment was more beneficial to the quality of blueberries than water treatment. Thus, PAW immersion is a promising method for maintaining the freshness of blueberries.

Methane detection to 1 ppm using machine learning analysis of atmospheric pressure plasma optical emission spectra

Optical emission spectroscopy from a small-volume, 5 μl, atmospheric pressure RF-driven helium plasma was used in conjunction with partial least squares-discriminant analysis for the detection of trace concentrations of methane gas. A limit of detection of 1 ppm was obtained and sample concentrations up to 100 ppm CH4 were classified using a nine-category model. A range of algorithm enhancements were investigated including regularization, simple data segmentation and subset selection, feature selection via Variable Importance in Projection and wavelength variable compression in order to address the high dimensionality and collinearity of spectral emission data. These approaches showed the potential for significant reduction in the number of wavelength variables and the spectral resolution/bandwidth. Wavelength variable compression exhibited reliable predictive performance, with accuracy values >97%, under more challenging multi-session train—test scenarios. Simple modelling of plasma electron energy distribution functions highlights the complex cross-sensitivities between the target methane, its dissociation products and atmospheric impurities and their impact on excitation and emission.

Слаботочный разряд в потоке аргона при атмосферном давлении в условиях образования атомов металлов: электрические и оптические характеристики

The paper presents the results of a study of the current-voltage characteristics and optical emission spectra of plasma of a atmospheric pressure pulsed discharge plasma at a frequency of several tens of kilohertz and a pulse duration of up to 10 μs, in the mode of generation of plasma flows containing metal particles. The features of the plasma generator conclude in combination of the design of electrodes, as well as the modes of electric and gas supply of the discharge system. The cathode is a crucible containing a melting insert which allows the discharge operation in a low-current form with a current of 40 mA to 1 A, at a sufficiently high voltage of 150 to 200 V, without transition to arc discharge mode. Such parameters make it possible to generate atomic flows of a melting cathode insert, which are blown out by a jet of working argon gas, pumped at a flow rate of 1 l/min, outside the discharge system. The entry of a metal component into a gas-discharge plasma affects the parameters of the discharge operation, as well as the properties of its optical emission. In the context of this phenomenon, the spectral distributions of the intensity of optical radiation corresponding to the lines of magnesium, indium, and zinc were investigated, as well as their time dependence during the current pulse period operation, in relation to the identification of physical features leading to stable generation of flows of metal atoms at atmospheric pressure.

Thermal annealing effect on the corrosion resistance of AlCuNiTiZr high entropy alloy films in sulfuric acid solution

In this study, corrosion-resistant AlCuNiTiZr high-entropy alloy (HEA) films were deposited by direct current magnetron sputtering. The films were found to be amorphous. Corrosion resistance of the films in 0.5 M H2SO4 solution were investigated and compared with 316L stainless steel. The minimum corrosion current density of the HEA films was about one order of magnitude lower than that of 316L stainless steel. The inductively coupled plasma optical emission spectra showed that the concentrations of Cu, Ni, Ti and Zr ions in the corrosion solution were as low as 10−7 mol / L, while the concentration of Al ions was 7.5×10−6 mol / L. It is revealed that two passivation layers were formed on the surface from electrochemical impedance spectroscopy and equivalent electrical circuit, and the passivation layers resulted in protective effect on the AlCuNiTiZr HEA films in the sulfuric acid solution.

Laser induced dielectric breakdown for synthesis of chlorofluorosilanes

Tetrafluorosilane (SF4) and tetrachlorosilane (SiCl4) plasmas have been widely used as a source of either F or Cl for etching silicon or as a source of silicon for deposition of Si-based materials. Using different combinations of F and Cl in molecules of chlorofluorosilane SiFxCly adds additional flexibility in realization of these processes. Direct synthesis of SiFxCl4-x (x = 1, 2, 3) from SiF4 and SiCl4 is thermodynamically forbidden under standard conditions. This restriction is removed in low-temperature plasmas studied in this work: a laser induced dielectric breakdown (LIDB) plasma and steady-state inductively-coupled plasma (ICP). The plasmas differ in many respects including energy content, temperature, and electron density that lead to different ionization/excitation states of plasma species, which are observed from plasma optical emission spectra. IR spectroscopy and mass-spectrometry confirm the formation of three chlorofluorosilanes, SiF3Cl, SiF2Cl2, and SiFCl3 that constitute ∼60 % in products of LIDB plasma and split 50/50 between SiF3Cl, SiFCl3 and SiF2Cl2. Experimental observations are verified by equilibrium static calculations via the minimization of Gibbs free energy and by dynamic calculations via the chemical-hydrodynamic plasma model of a spherically expanding plasma plume. The both types of calculations qualitatively agree with the results of spectroscopic analysis and reproduce dominant presence of SiF2Cl2 as the temperature of the gas approaches the room temperature.

Plasma characteristics and mode transition of atmospheric pressure gas–liquid discharge oxygen plasma

In this paper, a capacitor assisted AC high-voltage was employed to generate a gas–liquid discharge in pure oxygen at atmospheric pressure. The discharge images, waveforms of voltage and discharge current, and optical emission spectra of plasma were diagnosed for the purpose of investigating the discharge modes. The gas temperature (Tg), excitation temperature of hydrogen (Texc), and electron density (ne) were calculated by the spectra of OH (A2Σ–X2Π), the intensity ratio of Hα and Hβ, and the Stark broadening of Hβ, respectively. The effects of applied voltage and capacitance value on the mode transition of discharge were also discussed. It is found that due to the presence of capacitor, not only is the unlimited growth of discharge current restrained, but the transition of discharge mode is also controllable. There are three discharge modes of gas–liquid discharge oxygen plasma (GLDOP), and with the increase of applied voltage or capacitance value, discharge modes are transited from the streamer mode, to the glow-like mode, and to the abnormal glow/arc mode. With the mode transition, the Tg and Texc of GLDOP increase and the ne decreases. In contrast, the change of Tg and ne is negligible when GLDOP maintains one kind of discharge mode.

Herbometallic nano-drug inducing metastatic growth inhibition in breast cancer through intracellular energy depletion.

Cancer cells need extensive energy supply for their uncontrolled cell division and metastasis which is exclusively dependent on neighboring cells, especially adipocytes. Herein, we have introduced a novel herbometallic nano-drug, Heerak Bhasma nanoparticle (HBNP) from natural resources showing high potential in the reduction of energy supply thereby promoting cell death in breast cancer cells. Inductively coupled plasma optical emission spectra (ICP-OES), atomic absorption spectra (AAS), Raman spectra, X-ray diffraction analyses confirmed the physicochemical properties of HBNP. The differential light scattering (DLS) and field emission scanning electron microscope (FESEM) analyzed the cell-permeable size of HBNP, whereas, cell viability assay confirmed the non-toxic effect. Seahorse energy efflux assay, apoptotic cell quantification, ROS, mitochondrial membrane potential, in vivo oxidative stress etc. were measured using standard protocol. The notable changes in cancer energy metabolism investigated by cellular Mito and Glyco-stress analyses confirmed the HBNP induced intracellular energy depletion. Also, a significant reduction in mitochondrial membrane potential and subsequently, extensive reactive oxygen species (ROS) generations were observed in presence of HBNP followed by the induction of cell apoptosis. The cell invasion and wound healing assay followed by reduced expression both protein (MMP 2, MMP 9) and cytokine (IL6, IL10) had signified the effectiveness of HBNP against cancer metastasis. In addition, HBNP also showed an excellent antitumor activity in vivo followed by developing healing characteristics due to oxidative stress. All these findings strongly suggest that HBNP has the potential to be the new cancer therapeutic. A schematic phenomenon represents the overall HBNP mediated anticancer activity via limitation of both fatty acid uptake and energy metabolism.

Measurements of the electrical parameters and wound area for investigation on the effect of different non-thermal atmospheric pressure plasma sources on wound healing time

In this research, the effect of three different non-thermal atmospheric pressure plasmas on the skin wound healing was investigated. For this reason, 15 mice were assigned into 3 groups with 5 in each group. Each group was treated with one of the non-thermal atmospheric plasma for 5 consecutive days. The exposure time for each treatment was 30 s. Natural wound healing was compared with treated wound healing for 11 consecutive days. The voltage and current waveforms of each device, momentary powers, optical emission spectra of plasmas, the reduction ratios of wound area, and morphological changes were measured. The wounds treated by He plasma jet were healed faster than the wounds treated by others due to the discharge power, the uniformity of its plasma and the reactive species produced in He Plasma. On the second day after wounding, the treated wound with He plasma jet healed faster than the control wound.

Diffuse vacuum arc with heated cathode made of ceramic (CeO2) and metal (Cr) mixture

The paper presents a diffuse vacuum arc with heated cathode made of ceramic (CeO2) and metal (Cr) mixture, initiated and studied for the first time. Plasma sources of multicomponent mixtures are demanded for plasma based methods of rare-earths recycling and spent nuclear fuel reprocessing, which are currently under development. The discharge current–voltage characteristic was measured for different cathode temperatures (1950–2250 K); in the range of the arc current 30–100 A the voltage varied from 6 to 11 V. A cooling effect of the mixed cathode due to the thermionic emission at presence of the arc plasma was found; the effect reached about 150 W at the arc current of 30 A. The cooling effect and the current–voltage characteristic distinguish the discharge from the diffuse vacuum arcs with single-component cathodes made of cerium dioxide and chromium. The plasma parameters and optical emission spectra were analyzed for various cathode temperatures and arc currents (electron temperature was 0.4–0.6 eV, local particle densities in plasma near the cathode were in range 1011–1013 cm−3). The study is of interest for plasma sources development and increase of their efficiency as well as for the tasks aimed at ionization of multicomponent mixtures.

Effect of working gas on the deposition rate of CaP coatings formed by radio frequency magnetron sputtering of a hydroxyapatite target

This study is dedicated to the influence of the inert working gas on the deposition rate of CaP coatings formed by radio frequency magnetron sputtering of a hydroxyapatite target in Ar, Kr and Xe. The optical emission spectra of plasma, the elemental and phase composition of the formed coatings are investigated. The deposition rates of the CaP coatings formed in Ar and Kr are approximately comparable and higher than ones formed in Xe.

High power impulse magnetron sputtering of Zn/Al target in an Ar and Ar/O2 atmosphere: The study of sputtering process and AZO films

Reactive high power impulse magnetron sputtering (R-HiPIMS) has been demonstrated as a promising technique for the ZnO:Al (AZO) thin film deposition at low temperature with improved electrical properties compared to the reactive direct current magnetron sputtering (R-dcMS). However, there are not enough studies about the HiPIMS process using Zn/Al target itself. Additionally, AZO films have not been deposited with the pulse duration times long enough to allow the discharge to develop into the self-sputtering mode. C-V-t characteristics and the time average plasma optical emission spectra were studied as a function of different sputtering parameters, such as frequency, average power, pulse duration time, and oxygen flow rate. AZO films were deposited on glass substrates without intentional heating by R-HiPIMS using 500 μs long pulses. Structural, electrical and optical properties of the AZO films were studied as a function of peak current. Obtained peak power densities are relatively low compared to other metals due to the strong argon gas rarefaction, however, it is possible to increase the peak power density above 0.5 kW/cm2 by increasing the time between pulses or the average power to reach the HiPIMS regime. If the pulse duration time is 500 μs, the sustained self-sputtering discharge can be observed when the peak power density is above 0.3 kW/cm2. The peak current is sensitive to the oxygen content in the sputtering atmosphere so that it can be used as a control parameter for the reactive sputtering. The lowest obtained resistivity of the AZO films is 1.0 × 10−3 Ωcm with the transmittance around 70% in the visible light range. From the XRD measurements, there is the indication of existing zincblende structural phase in the R-HiPIMS deposited AZO films using high oxygen partial pressure.

Spectroscopic investigation of laser produced plasma of carbon nanotube reinforced AlMg5 metal matrix nanocomposites

Laser produced plasma of carbon nanotube reinforced AlMg5 metal matrix nanocomposites (AlMg5–CNT) is investigated by optical emission spectroscopy which dominantly consists of neutral aluminum (Al I) and magnesium (Mg I) atomic species. The blue-green (B2Σ−X2Σ) band system of AlO and green (1Σ → 1Σ) system of MgO are observed in the optical emission spectra of AlMg5–CNT plasma recorded without Ar shielding gas due to oxidation of Al I and Mg I species in air. The AlO blue-green (B2Σ−X2Σ) band system is also observed with Ar shielding gas in the optical emission spectra of plasma of AlMg5–CNT having oxidized grain boundaries which is irradiated by one or more laser pulses prior to plasma creation. The oxidation of grain boundaries in AlMg5–CNT is found to be nullified as the concentration of CNT reinforcement increases. Furthermore, the intensity ratio (IMgI/IAlI) of Mg I to Al I emission is found to be more for pristine AlMg5–CNT than that for AlMg5–CNT which is shot by one laser pulse prior to plasma creation, indicating more depletion of magnesium relative to aluminum.

Determination of metals as bio indicators in some selected bee pollen samples from Jordan.

This study was done to determine the degree of metals and heavy metals in some bee pollen sample as biological indicator for environmental pollution. Sample were collected from industrial, urban and agricultural areas of Jordan in year 2017. Eight metals (As, Cd, Cu, Mg, Pb, Ni, Se, and Zn) continents analyzed by using Inductively Coupled Plasma Optical Emission Spectrum, (ICP-OES).Results were statistically interpreted by using ANOVA analysis. Metals content in bee pollen from Jordan and China were determined within the following ranges (minimum–maximum mg/kg); Cu (copper): 11.338–0.032, Zn (Zinc): 77.022–25.24, Ni (Nickel): 2.839 to <0.01, Se (Selenium): 3.03 to <0.04, Mg (Magnesium): 1575.19–641.388, Pb (Lead): 2.567 to <0.03, Cd (Cadmium): <0.005, As (Arsenic): <0.02. The results showed that there were no statistically significant differences among metals in the bee pollen. It has also found that bee pollen produced in Jordan may be a good source of some trace elements like Se and Mg and can be used as an environmental indicator and for quality control.

Surface coupling of plasma optical emission spectra with bent metal-clad waveguide

We present the design of compact bent metal-clad waveguides to collect the vertically emitted light and to transmit to the horizontal direction. The intention of the design is to collect the plasma optical emission spectra inside the semiconductor etch process chamber to monitor plasma gas phase chemistry resides in the process chamber. Coupler A has been designed for visible spectra range from 748 to 753 nm at which the maximum coupling efficiency is over 52%, while Coupler B operates at the wavelength range from 775 to 780 nm with coupling strength of 62% and Coupler C covers the visible spectrum from 808 to 813 nm with its maximum efficiency of 60%. The surface couplers reveal good spectral characteristics, considerable alignment tolerance and minimal size of 9 × 5 × 1.6 µm3 each. Relatively simple geometrical structure over conventional grating coupler is advantageous to lower the fabrication cost as well.

Titanium dioxide and suboxide thin films grown with controlled discharge voltage in reactive direct-current sputtering

We have grown titanium dioxide and suboxide thin films using reactive direct-current magnetron sputtering methods. By monitoring the discharge voltage and plasma optical emission spectra at a constant current mode during the growth, we identified the oxidized conditions of metal target as well as the energy of plasma species, which characteristics were directly revealed in the structural and chemical properties of as-grown titanium oxide thin films. The films with a higher discharge voltage and a higher population of TiO* plasma turned out to have a dioxide configuration while ones with a lower voltage and a higher Ti* plasma are of multiple phases with suboxide counterparts.