Discharge Emission Research Articles

Optical emission of magnetron discharges as a function of the composition of argon—nitrogen gas mixtures

DC magnetron discharges in argon-nitrogen gas mixtures are characterized by optical emission spectroscopy (OES). Optical lines from the cathode species (aluminium) and the gas mixture (argon, nitrogen) are measured at constant total pressure, as a function of the gas mixture composition. The experimental data are compared with a theoretical model of the plasma. This model solves self-consistently the Boltzmann equation for electrons and the kinetic equations for aluminium, argon, and molecular and atomic nitrogen states. Despite the fact that this model does not include surface consumption of nitrogen species, its results compare satisfactorily with OES ones.

無電解ニッケル‐リン合金めっき皮膜の耐食性に及ぼす上層スズめっきの影響

Electroless nickel-phosphorus alloy was plated on steels, and tin plated on top of these. Double-plating films were analyzed by glow discharge emission spectrometry (GDS) before and after heat treatment. Effects of heat treatment on X-ray diffraction patterns, anodic polarization curves, and corrosion resistance were investigated compared to electroless nickel-phosphorus alloy films. Anodic polarization currents for tin/electroless nickel-phosphorus alloy double-plating films were greatly suppressed by heat treatment at 400°C. X-ray diffraction measurements confirmed the formation of intermetallic tin-nickel compounds after heat treatment. Current values were assumed suppressed due to formation of these compounds.GDS results showed that film surfaces were blue due to nickel oxides forming on them in heating electroless nickel-phosphorus alloy films at 400°C in an atmosphere. Electroless nickel-phosphorus alloy films with a tin overlayer did not show this color, however, because intermetallic tin-nickel compounds formed on the film surface. CASS tests showed that electroless nickel-phosphorus alloy films with a tin overlayer were superior in corrosion resistance to films without this overlayer.

Particle accumulation in a flowing silane discharge

Particle trapping in different areas of a parallel-plate, radio frequency silane discharge, and its effect on plasma optical emission of SiH and Hα, has been studied under high gas-flow and low power-density conditions, as used for “device-quality” hydrogenated amorphous silicon (a-Si:H) film deposition. The largest density of particles occurs between the electrodes, near the downstream corners of the rectangular electrodes. Particles are trapped in these positions by sheath fields, until reaching sufficient size to escape with the flow. The region of strong particle trapping has an increased intensity of optical emission, with Hα increased nearly fourfold. Slow oscillatory behavior of particle scattering and discharge emission was observed for pressures near 30 Pa. Power deposited in the discharge has also been measured; for a constant rf voltage and gas-flow speed it changes weakly with pressure, with the maximum at ∼40 Pa. Combined with film growth-rate measurements, this yields a discharge energy deposition of ∼17 eV per deposited Si atom.

Comparative study on emission characteristics of d.c.- and r.f.-powered Grimm glow discharge plasmas. Use of argon spectral lines

Equivalent discharge conditions, where the intensities of the analyte are almost the same between the d.c. and the r.f. power modes, have been investigated in Grimm glow discharge emission spectrometry. The two plasmas have similar emission and sputtering characteristics, enabling the conditions to be found easily. Various emission lines of argon ion are commonly observed from the argon discharges regardless of the power modes. A method to determine the equivalent discharge conditions is suggested, based on intensity analysis of the argon ionic lines.

Selection of self-absorption free analytical lines of aluminum in glow discharge optical emission spectrometry

To obtain a larger dynamic range in the glow discharge emission spectrometric determination of aluminum, the use of the ionic lines instead of the atomic resonance line was suggested. The ionic lines are essentially free from self-absorption leading to better linearity of analytical curves, while the atomic lines suffer from self-absorption to a certain extent. The ionic lines of aluminum are hardly emitted by the argon plasma; however, they can be excited by the neon-argon as well as the argon-helium mixed gas plasma. Therefore, the mixed plasma gases should be used. Calibration curves were measured for the different plasma gases and the concentration interval over which they were linear was estimated.

Correlation between Soft X-Ray Emission and Dynamics of Fast Capillary Discharges

A capillary discharge was driven by a fast pulse power generator `LIMAY-I' (3 Ω–70 ns) to investigate plasma dynamics. A two-stage pre-ionization circuit was developed to obtain uniformly preionized plasma load as the initial condition. Time-resolved radiations from the plasma column were observed by X-ray detectors and a fast streak camera. Experimental results indicated that the column can implode (rapidly contract) stably in an initial pressure range of 200–1000 Pa of argon. The reproducibility of the signal was quite good and the behavior of plasma column was well explained by one-dimensional magnetro-hydrodynamic (1D-MHD) simulation. These results suggest that the final plasma parameters satisfy the lasing condition for collisionally pumped Ne-like Ar with a sufficient margin of stability.

5567278 Process and apparatus for circulating backwater in a papermaking machine : Meinander Paul Grankulla, Finland assigned to POM Technology Oy Ab

Significant quantities of perfluoroalkyl acids (PFAAs) are released to the environment from fluorochemical manufacturing processes through wastewater discharge and air emission in China, which may lead to human exposure and health risks through crop bioaccumulation from PFAAs-contaminated soil and irrigation water. This paper systematically studied the distribution and transport of PFAAs in agricultural soil, irrigation water and precipitation, followed by crop bioaccumulation and finally human exposure of PFAAs within a 10 km radius around a mega-fluorochemical industrial park (FIP). Hotspots of contamination by PFAAs were found near the FIP and downstream of the effluent discharge point with the maximum concentrations of 641 ng/g in agricultural soil, 480 ng/g in wheat grain, 58.8 ng/g in maize grain and 4,862 ng/L in precipitation. As the distance increased from the FIP, PFAAs concentrations in all media showed a sharp initial decrease followed by a moderate decline. Elevated PFAA concentrations in soil and grains were still present within a radius of 10 km of the FIP. The soil contamination was associated with the presence of PFAAs in irrigation water and precipitation, and perfluorooctanoic acid (PFOA) was the dominant PFAA component in soil. However, due to bioaccumulation preference, short-chain perfluoroalkyl carboxylic acids (PFCAs), especially perfluorobutanoic acid (PFBA), became the major PFAA contaminants in grains of wheat and maize. The bioaccumulation factors (BAFs) for both grains showed a decrease with increasing chain length of PFAAs (approximately 0.5 log decrease per CF2 group). Compared to maize grain, wheat grain showed higher BAFs, possibly related to its higher protein content. The PFCA (C4-C8) concentrations (on a log10 basis) in agricultural soil and grain were found to show a linear positive correlation. Local human exposure of PFOA via the consumption of contaminated grains represents a health risk for local residents, especially for toddlers and children.

流動層によるオーステナイト系ステンレス（ＳＵＳ３０４）鋼のほう化処理

Boronizing is well known to improve wear and corrosion resistance, because boron forms intermetallic compounds. Although the characteristics of boronized austenitic stainless steel have been reported, little information is available on boronizing in fluidized beds. We analyzed, the boronized layer using glow discharge emission spectrometry (GDS), X-ray thin diffraction, and ESCA. We studied the friction and wear characteristics and corrosion behavior of boronized SUS 304 stainless steel, and obtained the following results, (1) The Knoop hardness was 1900HK for specimen treated for 4h at 1123K. A boronized layer was formed with three lamellar layers, the first layer mainly FeB, the second Fe2B, and the third a ferritic phase. The FeB layer had a fine structure and the physical etching of GDS was useful for observing this microstructure.(2) The boron concentration was about 50 at% in the first layer, about 40 at% in the second, and about 30 at% in the third. The boronized layer contained about 10 at% Cr. Ni and Si enrichment were detected in the ferritic phase.(3) The boronized specimen had a high wear resistance to SUJ 2 and Al2O3 than an untreated one, but the friction characteristics was not greatly improved.(4) Corrosion resistance was improved against 0.1N HCl but not against 0.1N H2SO4 or 10% oxalic acid solution.

Self-absorption in Quantitative Glow Discharge Emission Spectrometry

The emission intensities of five resonance atomic lines affected by self-absorption were investigated as a function of analyte concentration in a sample for a Grimm-type atomization/excitation source operated in the dc mode in argon. Based on considerations of radiative transfer within the source, and using the two-layer model and other approximations, the equationwas derived, linking the emission intensity I E M , the sputter rate q M and the analyte concentration c E M in the matrix, where E is a particular element in a matrix M . The R E0 and β E constants resulting from fitting the experimental data to this relationship were investigated as functions of GD operating conditions. It was shown that R E0 can be regarded as the (generalized) emission yield. Dependence of the R E0 and β E parameters on discharge operating conditions suggests that they could reflect more fundamental processes occurring in the discharge. Comparison of β E factors for different lines, however, leads to results that are not explicable within the adopted model. Methodology of quantitative GD-OES analysis was generalized to be applicable also to self-absorption lines with non-linear intensity responses.

Photoluminescent Mn-Doped ZNS Nanoclusters Synthesized within Block Copolymer Nanoreactors

ABSTRACTMn-doped ZnS nanoclusters were synthesized within microphase-separated films of diblock copolymers containing carboxylic acid units on one of the blocks. Zinc was selectively sequestered into the acid-containing domains by treating the films with diethylzinc or an aqueous zinc acetate solution. Manganese was loaded by subsequent treatment of the films with aqueous manganese acetate solutions. The manganese ions displaced a fraction of the zinc ions, and the extent of loading was controlled by varying the loading time, and the concentration of the manganese acetate solution. The extent of loading was tracked using ICP discharge emission spectroscopy. The doped nanoclusters were formed by subsequent treatment with H2S. The size of the doped ZnS nanoclusters could be varied by carrying out the H2S exposure in the presence of a coordinating base. Photoluminescence measurements revealed that the doped nanoclusters were photoluminescent, and showed the characteristic manganese emission. The universal doped cluster synthesis scheme used is quite general and can be easily modified to produce other doped nanocluster clusters, such as Tb-doped ZnS, or Mn-doped CdS.

Blackening of argon/mercury cold cathode discharge lamps

We report about the physical and chemical origin of the quick loss of intensity of certain argon/mercury cold cathode illumination tubes, especially those manually coated with luminous powder using the European powder technology. The reason is the disintegration of the phosphoric acid binder, which leads to the release of water vapor in the operating plasma tube. Subsequently formed mercury–water complexes lower the intensity of the UV emission of the Hg discharge in the 250 nm range, because the complexes decay radiationless into the ground state, thus, reducing the brightness of the fluorescent powder in the visible range substantially. If shut off, the respective tubes show a turn in color of the luminous powder coating from white to a light brown. We also found that the released water vapor causes heavy sputtering of the activated hollow-cathode-type nickel electrodes. Possible reasons for this are discussed, too.

High selectivity plasma etching of silicon dioxide with a dual frequency 27/2 MHz capacitive radio frequency discharge

A 27 MHz/2 MHz Ar/CO/CFx rf capacitive discharge was used to selectively etch submicron SiO2/Si, SiO2/TiSi2 and SiO2/TiN structures. The borophosphosilicate glass etch rate (∼1.0 μm/min) was observed to decrease with bottom electrode temperature, whereas etch selectivity to TiSi2 (≳50:1) was found to increase with temperature, with a photoresist selectivity ≳50:1. Plasma emission of the dual frequency discharge indicated the presence of an abundant concentration of the CF2 radical (249 nm) as compared to a lower frequency (400 kHz) rf discharge with low etch selectivity (<20:1). Langmuir probe measurement indicated an enhancement of ion density of an order of magnitude (∼5×1010 cm−3) as compared to the low frequency (400 kHz) rf discharge. Particle-in-cell simulation was used to calculate plasma density as a function of excitation frequency. Plasma density scales with the square of the source frequency while it remains relatively independent of the substrate frequency.

The influence of metastables on the plasma-induced emission in a helium rf discharge

Space- and time-resolved emission spectroscopy is commonly used to investigate heating mechanisms in rf discharges (plane parallel plate configuration). The metastable density in these discharges is several orders of magnitude lower than the density of the ground-state atoms; however, the electron collision excitation cross sections of some helium levels out of the metastable levels exhibit values which are several orders of magnitude larger and have much lower thresholds than those for the ground state. It is therefore questionable whether stepwise excitation from metastable levels can be neglected in the interpretation of the spatiotemporal plasma-induced emission of rf discharges. To our knowledge only the excitation of ground-state atoms has been taken into account in model calculations to this date. With respect to the energy balance of such a discharge, this assumption is probably correct. However, with respect to the emission of light, our computational results show that some specific levels are excited significantly by electron collisions with metastables. We will show in this contribution, on the basis of our measurements, that this effect is responsible for the observed emission profiles of some lines. Consequently, the interpretation of the emission profiles in helium rf discharges has to take account of the role of metastables.

Influence of humidity on current waveform and light emission of a low-frequency discharge controlled by a dielectric barrier

The aim of this work is to determine the effect of humidity on a silent discharge in air. A point to plane configuration has been used. Current and emission spectra of the discharge have been recorded in dry and humid air for short and long inter-electrode gaps and with the plane electrode coated by a silicone rubber plate alone or under a polypropylene film. Results show the typical corona discharge regimes. For a long gap, humidity decreases the number of breakdown streamer pulses. For a short gap, the behavior observed depends on the surface conduction of the dielectric in contact with the discharge. These results show that the presence of humidity in the discharge cell not only modifies the gas but also the surface states of the dielectrics coating the electrodes. The surface charge decay appears as a major parameter, since it is related to the local field value which results from the applied field and the reverse field induced by charge accumulation during previous discharges.

Effect of driving frequency on the operation of a radiofrequency glow discharge emission source

Several characteristics of the r.f. glow discharge were examined to determine their dependence on driving frequency. The cathode potential exhibited a strong dependence on frequency, as would be expected, because of the capacitive nature of the discharge. As the frequency was dropped from 13 to 6 MHz there was a dramatic rise in the r.f. voltage of the discharge (with a conductive sample), attributed to a change in the mode of power coupling. The sputtering rates of a conductive sample were dramatically greater at the lower frequencies, in part due to higher energy of the sputtering ions. The emission characteristics of the source also changed as the frequency was varied from 6 to 13 MHz. At the higher operating frequencies, atomic emission peaked at a particular r.f. power level, whereas at lower frequencies the neutral-atom signal generally increased monotonically with power. The highest signal levels were found at 20 MHz, the highest frequency studied. Detection limits were determined for both conductors and insulators; in both cases they are detector-noise-limited because of the low throughput of the spectrometer. Detection limits for a conducting sample ranged from 0.1 μ g −1 at 20 MHz to 20 μ g −1 at 3 MHz. The emission from an insulating sample showed the same trends as those from a conducting sample but required higher r.f. power; the greatest signals were found at 6 and 13 MHz because not enough power was available from the r.f. amplifier to reach the optimum power for the 20 MHz discharge. Detection limits for elements in a Macor ® ceramic sample ranged from 30 to 110 μg g −1.

Pilot Study of the Analytical Performance of the Pulsed Hollow Cathode Discharge Emission Source

Proper conditioning of the hollow cathode by sputtering is critical to the analytical performance of the hollow cathode. A pulsed discharge procedure was developed to condition the 1.5- × 5-mm stainless steel cathode. A scanning electron microscope was used to study the surface structure resulting from the conditioning. The resulting hollow bottom was bulb-shaped and the surface was mirror-like, very smooth, and shiny. The emission intensities from smooth cathodes were greater that those from the rough ones. The precision obtained here was 3–5% for Na, 5–8% for Li, and 4–10% for K. Three working curves for each element were made on different days with different cathodes that had been conditioned in the same manner for 4 h by sputtering. The three working curves virtually coincided when plotted in the same figure, demonstrating the precision and reproducibility from day to day of the hollow cathode discharge method as developed in this laboratory. The 3-σ detection limits calculated from slopes of working curves are 0.32 pg, 0.35 pg, and 3.2 pg for Na, Li, and K, respectively.

Crystallographic orientation and light emission of streamer discharges in II-VI semiconductors

Some results of Investigations on the crystallographic orientation, luminescence and stimulated emission of streamer discharges in monocrystals of hexagonal CdS, CdSe and ZnO and cubic Znsand Snseare presented.

Rotational Structure and Perturbations in the B4Π- X4Σ − (1, 0) Band of VO

The (1, 0) band of the B 4Π- X 4Σ − transition of VO has been analyzed rotationally, from Doppler-limited discharge emission and laser excitation spectra. The B 4Π, v = 1 level is heavily perturbed by a vibrational level of the a 2Σ + state and, with the extra complexity caused by the 51V nuclear hyperfine structure, could be analyzed fully only by extensive wavelength-resolved laser-induced fluorescence experiments. Making use of data from the corresponding perturbations in B 4Π, v = 0 and assuming that the vibrational dependence of the spin-orbit matrix element can be represented by a vibrational overlap integral, it has been possible to deduce the vibrational numbering of the perturbing a 2Σ + state without having to use isotopic data. It is found that the a 2Σ +, v = 0 level lies near 10412 cm −1, and that B 4Π, v = 1 is perturbed by a 2Σ +, v = 3. The a 2Σ + state comes from the same electron configuration, (4 sσ) (3 dδ) 2, as the X 4Σ − ground state. The phases of the spin-orbit matrix elements between 4Π and 2Σ + states must be chosen consistently in order to obtain a correct understanding of the rotational perturbations. A consistent set of phases is obtained with 〈 2Σ +, F 2 | H SO | 4Π 1 2 , f〉 = 〈 2Σ +, F 1 | H SO | 4Π 1 2 , e〉 = [formula] 〈 2Σ +, F 2 | H SO | 4Π − 1 2 , f〉 = −〈 2Σ +, F 1 | H SO | 4Π − 1 2 , e〉 = A/2, where A = 〈 2 Σ + || H spin- orbit || 4 Π〉.

Evaluation of a Microcavity Hollow Cathode Discharge Emission Source

A microcavity hollow cathode discharge emission source has been designed and evaluated for ultratrace analysis of sub-μL samples of solution residues. It was found that sample drying time and cathode precondition had a significant effect on the signal-to-background and signal-to-noise ratios. Detection limits for Cu and Pb were determined to be 10 pg and 210 fg, respectively.

Direct solid sample analysis of SiC-powders by DC glow discharge and DC-ARC emission spectroscopy

Glow discharge atomic emission spectroscopy (GD-OES) and the classical spectrographic method with a dc arc source (DC-ARC OES) have been applied to the direct analysis of SiC powders. The homogeneity of pellets prepared from mixtures of SiC with copper powder and used for the GD experiments was investigated in detail. Various methods have been tested for the analytical calibration. These have been applied to the direct solid sample analysis of technical SiC powders. The experimental data were evaluated by chemometrical procedures. The results of the two methods have been compared.