Ar Glow Discharge Research Articles

Changes of the TiO2 thin film electro-optical properties in the Ar and N2 glow discharge plasma due to effects of the electric field in plasma's sheath

Titanium dioxide thin films were prepared on glass substrates by spin-coating sol-gel method. The samples were exposed to the N2 and Ar glow discharge plasmas. The properties of the crystal structure and electro-optical features were measured. The average crystallite size of the thin films was decreased at 30% and 41% by the plasma of N2 and Ar, respectively. We showed the changes in the charge distribution of the crystal unit cells and the chemical bonds’ characteristics that lead to alteration of the single-oscillator parameters. Due to the N2 and Ar plasmas, the third-order nonlinear susceptibility in long-wavelength was increased about 25% and 123%, respectively. An alteration occurred in the optical band gap through TiN formation on the surface of the TiO2 thin film in the N2 plasma. This empirical study illustrated more considerable changes in TiO2/Ar thin film, due to the stronger electric field in the sheath of Ar plasma.

Enhanced thermionic emission of mayenite electride composites in an Ar glow discharge plasma

Mayenite electride has attracted increasing research interests because of its unique electronic properties. The thermionic emission behavior of the mayenite electride is relatively unknown. Previous studies revealed that mayenite electride exhibited a bare work function ranged from 2.1–2.6 eV when the thermionic emission was tested in vacuum, and enhanced emission currents could be achieved by applying a super-high external electric field. In this paper, the thermionic emission behavior and the corresponding effective work function of two types of mayenite electride based composites, mayenite electride-titanium and mayenite electride-carbon, were investigated in an Ar glow discharge plasma at elevated temperatures (400–1000 K) without applying a high external electric field, which is critical for the application in electric propulsion and other aerospace apparatus, yet never had been done before. During the testing, the thermal equilibrium process and plasma sheath expansion were observed. The effective work function of the two mayenite electride composites were determined as a function of temperature. The Rasor-Warner model was applied to determine the bare work function and adsorption-site density of the mayenite electride based composites. Results suggested that the adsorption of Ar ions led to the enhanced thermionic emission (~30 A/m2 at 985 K) and low effective work functions (0.9–2.2 eV) of mayenite electride based composites, without the need of applying high electric fields. Our findings will pave the ways for the application of mayenite electride and its composites as the thrust cathode materials for electric propulsion where plasma is present.

Treatment of the ZnO and TiO2 Thin Films by Electric Field in Plasma Sheath to Improve the Metal-Dye Electronic Coupling in Dye-Sensitized Solar Cells

In this study, the effect of the electric field of Ar and N2 plasma sheath on the crystalline structure and the optoelectronic properties of ZnO and TiO2 thin films were investigated, in order to improve the electronic coupling of metal-N719 dye in dye-sensitized solar cells. The thin films were prepared via the sol-gel method and then treated in Ar and N2 glow discharge plasma. The plasma effect on the crystalline structure was determined using the XRD spectra and the scanning electron microscope images. The electric field in the Ar plasma sheath is stronger than the N2 plasma, so the crystalline changes in the ZnO/Ar and TiO2/Ar were larger in comparison to ZnO/N2 and TiO2/N2. The variations evaluated via the UV-VIS spectra for the optoelectronic properties coincided with the changes in the crystalline structure. A detailed study of the dispersion parameters and the third-order nonlinear optical susceptibilities represented alterations in the chemical properties of the surface of the thin films.The thin films of ZnO, ZnO/Ar, ZnO/N2, TiO2, TiO2/Ar, and TiO2/N2 were sensitized by the N719 dye via the immersion method, with enough duration of time for the adsorption and the aggregation to take place. According to the measurements of the short circuit photocurrent density, the order of enhancement in the electronic coupling is: ZnO/Ar-N719> ZnO/N2-N719> TiO2/Ar-N719> TiO2/N2-N719. The plasma remarkably enhances the Zn-N719 electronic coupling via the reduction of the Zn2+/dye complexes, in the case of the Ti-N719, increment in the electronic coupling occurs by the reduction of the H-bonds.

Spatially-Resolved Spectroscopic Diagnostics of a Miniature RF Atmospheric Pressure Plasma Jet in Argon Open to Ambient Air

The spatially-resolved electron temperature, rotational temperature, and number density of the two metastable Ar 1 s levels were investigated in a miniature RF Ar glow discharge jet at atmospheric pressure. The 1 s level population densities were determined from optical absorption spectroscopy (OAS) measurements assuming a Voigt profile for the plasma emission and a Gaussian profile for the lamp emission. As for the electron temperature, it was deduced from the comparison of the measured Ar 2 p i → 1 s j emission lines with those simulated using a collisional-radiative model. The Ar 1 s level population higher than 10 18 m − 3 and electron temperature around 2.5 eV were obtained close to the nozzle exit. In addition, both values decreased steadily along the discharge axis. Rotational temperatures determined from OH(A) and N 2 (C) optical emission featured a large difference with the gas temperature found from a thermocouple; a feature ascribed to the population of emitting OH and N 2 states by energy transfer reactions involving the Ar 1 s levels.

In-situ preparation of Pd nanoparticles in the pore channel of CMK-3 for Suzuki coupling reaction

Palladium nanoparticles (PdNPs) supported on ordered mesoporous carbon (CMK-3) were prepared by Ar glow discharge plasma technology (P-PdNPs/CMK-3) without the use of any chemical additives or surfactants and chemical method using ascorbic acid as reducing agent (AA-PdNPs/CMK-3), respectively. The PdNPs/CMK-3 catalysts were characterized by XRD, N2 absorption-desorption and TEM analysis. The results showed that the as-prepared PdNPs were of the face-centered cubic structure, P-PdNPs/CMK-3 had an average particle size of 3.4 nm (lower than CMK-3 pore diameter of 3.7 nm), which corresponded to an average diameter of 11.1 nm for AA-PdNPs/CMK-3. The in-situ preparation of P-PdNPs/CMK-3 had a higher dispersion of Pd species and mainly formed inside the pore channels of CMK-3, but distributed on the outer surface of support for AA-PdNPs/CMK-3. The yield reached 95% in the presence of 0.1 mmol% P-PdNPs/CMK-3 at 40 °C for 30 min towards the reaction of 4-bromonitrobenzene and phenylboronic acid, which corresponded to 86% for AA-PdNPs/CMK-3. The better stability and recyclability for P-PdNPs/CMK-3 were confirmed by the hot filtration and recycling test.

Experimental measurements of the hollow cathode DC glow discharge parameters in Ar and He plasmas

In this article, we focus on some of the fundamental parameters of SS316L hollow cathode glow discharge. Four SS316L samples are placed at different locations on the cathode surface and the current passed through them is measured in Ar and He glow discharge plasmas. The wall current densities of Ar and He are in the range of 8–25 µA cm−2 and 8–35 µA cm−2, respectively. Results also show that with decreasing working pressure, the ion flux and current density distribution on the wall surface becomes more uniform. The ion flux of the Ar and He is in the range of 1013 to 1014 . Total energy losses of Ar and He are measured at the pressure range of 1.4–5.5 × 10−2 torr and 3.2–7.1 × 10−1, respectively. In both Ar and He, total energy losses decreased with increasing pressure. The secondary electron emission coefficients of Ar and He, which are evaluated for the hallow cathode configuration, are about 0.42 and 0.26, respectively, and are higher in comparison with the plate cathode configuration.

Heterogeneous sono-Fenton-like process using nanostructured pyrite prepared by Ar glow discharge plasma for treatment of a textile dye

The plasma-treated pyrite (PTP) nanostructures were prepared from natural pyrite (NP) utilizing argon plasma due to its sputtering and cleaning effects resulting in more active surface area. The NP and PTP were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Brunauer–Emmett–Teller (BET) and scanning electron microscopy (SEM) methods. The performance of the PTP was greater than NP for treatment of Reactive Red 84 (RR84) by the heterogeneous sono-Fenton process. The optimum amounts of main operational parameters were obtained as PTP of 4g/L, initial dye concentration of 10mg/L, pH of 5, and ultrasonic power of 300W after 120min of reaction time. Also, the effects of enhancers, and inorganic salts and t-butanol as hydroxyl radical scavengers on the degradation efficiency were investigated. Gas chromatography–mass spectroscopy analysis (GC–MS) was applied for detection of some degradation intermediates. Environmentally friendly plasma modification of the NP, in situ production of H2O2 and OH radicals, low leached iron concentration and repeated reusability at the milder pH are the significant benefits of the PTP utilization.

Investigation of Excitation Mechanism of Cu II Lines under Different Atmospheres

The excitation mechanism of Cu II lines under an Ar and Ne glow discharge plasmas were investigated. Charge transfer collision is the domain excitation mechanism which resulting into the intensive emission of Cu II lines at particular wavelength. Under Ne glow discharge plasma, charge transfer collision and Penning type collision makes great contribution to the violently emission of particular Cu II lines.

Reaction kinetics studies on plasma‐treated polypropylene–polystyrene interfaces

AbstractIn this article, the effects of low temperature Ar glow discharge plasma modification on the surface of polypropylene (PP) and polystyrene (PS) plates were characterized by X‐ray photoelectron spectroscopy, and the temporal change of the complex viscosity (η*) of PP/PS plates with a sandwich structure were measured by a rotational rheometer. The results showed that the formation of reactive groups on the surface of PP and PS plates was due to the reaction of O2 with some free radicals when exposed to air. In the rheology study, because of the increase of interfacial adhesion strength due to the coupling reaction between the reactive groups at the interface, η* increased with welding time. There were two distinct stages for the changes of η* with welding time. In Stage I, η* increased rapidly and indicated a reaction‐controlled kinetics, the apparent reaction kinetics was a first‐order reaction; in Stage II, η* increased slowly and indicated a diffusion‐controlled reaction. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Fuel hydrogen retention of tungsten and the reduction by inert gas glow discharges

Polycrystalline tungsten was exposed to deuterium glow discharge followed by He, Ne or Ar glow discharge. The amount of retained deuterium in the tungsten was measured using residual gas analysis. The amount of desorbed deuterium during the inert gas glow discharge was also measured. The amount of retained deuterium was 2–3 times larger compared with a case of stainless steel. The ratios of desorbed amount of deuterium by He, Ne and Ar glow discharges were 4.6, 3.1 and 2.9%, respectively. These values were one order of magnitude smaller compared with the case of stainless steel. The inert gas glow discharge is not suitable to reduce the fuel hydrogen retention for tungsten walls. However, the wall baking with a temperature higher than 700K is suitable to reduce the fuel hydrogen retention. It is also shown that the use of deuterium glow discharge is effective to reduce the in-vessel tritium inventory in fusion reactors through the hydrogen isotope exchange.

Fabrication of metallic magnetic nanostructures by argon ion milling using a reversed-polarity planar magnetron ion source

We demonstrate that a planar magnetron may be used as a source of ions for milling micro- and nanostructured devices. Reversing the polarity of the magnetron head, in combination with applying a voltage bias to the thin-film sample, allows acceleration of ions produced in the Ar glow-discharge to energies suitable for pattern transfer via etching. We have fabricated generic Hall-bar and nanowire L-bar structures from sputter deposited Ta/Ni/Ta trilayer films grown onto clean GaAs(001) surfaces. No degradation of the magnetic properties or contamination of the deposition chamber vacuum is observed, demonstrating that this method is effective for etching magnetic device structures patterned by both optical- and electron-beam lithography techniques.

Exchange and reduction of retained hydrogen isotope by glow discharges

Following hydrogen glow discharge of stainless steel, a deuterium glow discharge was conducted to exchange the retained hydrogen in the stainless steel for deuterium. During the deuterium discharge, about 60% of the retained hydrogen desorbed. The amount of retained deuterium was 1.5 times larger than that of desorbed hydrogen. After the deuterium discharge, glow discharge cleaning with inert gas was conducted and the amount of the removed hydrogen isotope was evaluated. The removal ratio of hydrogen isotopes in the stainless steel was the largest during He glow discharge, and the smallest during Ar glow discharge. The removal ratio of retained hydrogen isotope by neon discharge cleaning did not change although sequential discharges of deuterium and neon were conducted repeatedly.

Vibrational Distribution of N2(C, ν) State in a Pulsed-DC Generated N2–Ar Glow Discharge

ABSTRACT The dependence of vibrational distributions (VDs) of N2(C, ν) state on argon fraction and filling pressure was investigated in terms of integrated band intensities of second positive system (C, ν′ → B, ν″) of N2. The vibrational temperature was determined from slope of the Boltzmann fit of these VDs and found to be strongly dependent on argon fraction in the discharge. The spectroscopic results suggested that collisional transfer of energy from Ar (3P2,0) metastable atoms to N2(X, ν) ground state is the main excitation pathway for population of N2(C, ν) state.

On the accuracy and limitations of fluid models of the cathode region of dc glow discharges

This paper compares the performance and limitations of different models of the cathode region of cold-cathode low-pressure dc glow discharges: (i) we review known modelling approaches, (ii) develop our own simulation codes based on these approaches, (iii) perform calculations using these codes for reference sets of discharge conditions, which allows a critical comparison of the models and (iv) for a further check of the simulation results we carry out Langmuir probe measurements of electron densities in abnormal Ar glow discharges. The theoretical approaches include fluid models both neglecting and including the electron energy balance equation, as well as hybrid models, which combine the fluid treatment of slow plasma species with the kinetic simulation of fast electrons. We also test the effect of the choice of the ionization source term in fluid models. We find that the electron densities calculated from the fluid models are far (several orders of magnitude) below the experimental values even if the electron energy equation is considered in the calculations. This weakness of fluid models clearly points out the importance of an accurate calculation of the ionization source term, which can only be accomplished by a kinetic approach under the conditions of highly nonlocal electron transport in the cathode region of glow discharges. In hybrid models Monte Carlo simulation is used for this purpose, and indeed, this approach gives electron densities comparable to our experimental data.

Reduction of hydrogen and helium retention in stainless steel by argon glow discharge

Although wall conditioning using Ar glow discharges is occasionally employed to reduce helium and hydrogen retention in the inner walls of the vacuum chamber of nuclear fusion devices, the effect of an Ar glow discharge on the reduction of helium and hydrogen retention has never been systematically investigated. In the present experiment, Ar glow discharges were applied to the stainless steel walls of a glow discharge device. Residual gas analysis (RGA) clearly showed that the Ar glow discharge significantly reduced the amount of helium and hydrogen retained. It was found that the fraction of the amount of desorbed helium to the initial retained amount of helium was as high as 13% and the fraction of the amount of desorbed hydrogen to the initial amount of hydrogen was as high as 36%.

アルゴングロー放電質量分析法における種々のマトリックスに対する相対感度係数

Unification of relative sensitivity factors (RSFs) in Ar glow discharge mass spectrometry was investigated. A Mega flat cell was used as a discharge cell for disk samples; ultra-high purity Ar (99.9999%) was used as the discharge gas. A sample mask for the disk sample with an inner diameter of 12 mm (made by Ta: part of the anode) was used, and a donut-shaped alumina (Al2O3) piece with an inner diameter of 20 mm was used for insulation between the sample and the anode. Discharge parameters were set as 1 kV–3 mA. Reference materials, such as Al, Co, Ni, Ti, Cu, and Fe matrices, were measured; the RSF value of every element for each matrix was determined. Then the RSF values were recalculated using Fe as the internal standard element, and the possibility of unification was verified for each matrix. Results showed that the RSF values of elements analyzed for each matrix normalized by Fe agreed well for five kinds of matrices. The relative standard deviation (RSD (%)) of the average of those RSFs varied: from greater, 15% for W and 18% for Cu; to smaller, 6% for Si and 5% for Cr. Results therefore demonstrated that using the RSF value for Fe can enable quantitative analysis within 10% of relative error of materials and substances for which no reference material (group) is available. For example, Si and Si-based materials and substances can be analyzed by normalizing the RSF value of Si to 1, recalculating the RSF values of the element analyzed therewith, and using them for corrective quantitative analysis.

Interface microstructure engineering by high power impulse magnetron sputtering for the enhancement of adhesion

An excellent adhesion of hard coatings to steel substrates is paramount in practically all application areas. Conventional methods utilize Ar glow etching or cathodic arc discharge pretreatments that have the disadvantage of producing weak interfaces or adding droplets, respectively. One tool for interface engineering is high power impulse magnetron sputtering (HIPIMS). HIPIMS is based on conventional sputtering with extremely high peak power densities reaching 3kWcm−2 at current densities of >2Acm−2. HIPIMS of Cr and Nb was used to prepare interfaces on 304 stainless steel and M2 high speed steel (HSS). During the pretreatment, the substrates were biased to Ubias=−600V and Ubias=−1000V in the environment of a HIPIMS of Cr and Nb plasma. The bombarding flux density reached peak values of 300mAcm−2 and consisted of highly ionized metal plasma containing a high proportion of Cr1+ and Nb1+. Pretreatments were also carried out with Ar glow discharge and filtered cathodic arc as comparison. The adhesion was evaluated for coatings consisting of a 0.3μm thick CrN base layer and a 4μm thick nanolayer stack of CrN∕NbN with a period of 3.4nm, hardness of HK0.025=3100, and residual stress of −1.8GPa. For HIPIMS of Cr pretreatment, the adhesion values on M2 HSS reached scratch test critical load values of LC=70N, thus comparing well to LC=51N for interfaces pretreated by arc discharge plasmas and to LC=25N for Ar etching. Cross sectional transmission electron microscopy studies revealed a clean interface and large areas of epitaxial growth in the case of HIPIMS pretreatment. The HIPIMS pretreatment promoted strong registry between the orientation of the coating and polycrystalline substrate grains due to the incorporation of metal ions and the preservation of crystallinity of the substrate. Evidence and conditions for the formation of cube-on-cube epitaxy and axiotaxy on steel and γ-TiAl substrates are presented.

ヘリウムグロー放電イオン源における高効率イオン化に対する一考察

High-effective ionization during ferrous analyses using a He glow-discharge ion source was investigated. The respective relationships between the ionization potential (Ip) of each element and various ionic strengths were studied in detail for He glow discharge and Ar glow discharge. The energies of the helium metastable atom (Hem) is 1910 kJ/mol (19.80 eV) and 2022 kJ/mol (20.96 eV). It is presumed that Hem contributes to creation of doubly-charged and singly-charged ions. Results show that numerous doubly-charged ions are generated by He glow discharge. If this ratio is greater than that of an internal standard element Fe, the RSF-value becomes greater than 1 (the ionic strength ratio decreases). Furthermore, with elements having Ip2 of more than approximately 18 eV, e.g., Ni, As, P, and C, the relative ionic strength of doubly-charged ion with respect to the singly-charged ion is only several percent at the highest. Consequently, the RSF-values approach unity (1). High-effective ionization by glow discharge is dependent upon the type of discharge gas, the matrix (internal standard element) and analyzing element, the presence of spectral interference, RSF-value, and other factors.

Reduction of Supported Noble-Metal Ions Using Glow Discharge Plasma

A novel plasma reduction method has been developed to reduce supported noble-metal ions without the use of any reducing chemicals. H2PtCl6, PdCl2, AgNO3, and HAuCl4 supported on nonporous TiO2 and porous gamma-Al2O3 and HZSM-5 were reduced using an Ar glow discharge plasma. Optical absorption spectra and X-ray photoelectron spectroscopy show that the supported metal ions are completely reduced to metallic species. Transmission electron microscopy shows that the prepared metals are amorphous clusters and homogeneously distributed with nanoscale sizes. X-ray diffraction also confirms that the plasma-reduced metals exist as small crystallites or amorphous clusters. Thermal annealing of plasma-reduced samples at elevated temperature transforms the clusters into crystals with a slight increase in particle sizes, but the sizes are still smaller than those of H2-reduced metals. O2 glow discharge plasma can also reduce noble-metal ions, accompanied by production of a small amount of oxides. Plasma reduction is very promising for the preparation of metal nanoparticles and supported metal catalysts.

Fracture behavior of diamond-like carbon films on stainless steel under a micro-tensile test condition

We investigated the stability of the DLC film coated on 304 stainless steel substrate by r.f. PACVD method. Fracture and spallation behaviors of the coating were observed during micro-tensile test of the film/substrate composite. As the tensile deformation proceeded, the cracks of the film appeared in the perpendicular direction to the tensile axis. Further deformation resulting in the local necking with shear band of 55° inclined to the tensile axis, induced the spallation of the film, which was initiated at the cracks of the film, and was aligned along the slip directions. We found that both the cracking and the spallation behaviors are strongly dependent on the pretreatment condition, such as Ar plasma pretreatment or Si buffer layer deposition. The spallation of the film was significantly suppressed in an optimized condition of the substrate cleaning by Ar glow discharge. These results show that the spallation behavior during the tensile test can be used to estimate the interfacial strength of the coating with relatively poor adhesion.