A Broadband Excimer-Halogen Emitter Utilizing Xenon Bromide and Iodide

The results are given of an investigation of the output characteristics of an electric-discharge excimer-halogen UV emitter utilizing a Xe/Br₂/J₂ mixture. A longitudinal glow discharge with an interelectrode spacing of 50 cm and inside diameter of the discharge tube of 1.4 cm is ignited at the working mixture pressure of 1 kPa and power input to the plasma of 10–350 W. A study is performed of the current-voltage characteristics of the discharge, plasma radiation spectra in the 190–350 nm range, and distributions of the brightness of radiation of molecules as a function of the pumping conditions, as well as of pressure and partial composition of the gas mixture. It is demonstrated that the plasma of the discharge being investigated is a source of broadband UV radiation in a system of bands of 253 nm XeJ, 282 nm XeBr, and 292–310 nm Br₂ ^*, which are joined by the radiation of resonance line of iodine atom with = 206 nm. The total power of UV radiation of plasma increases linearly with the electrical power of the glow discharge.     

Characteristics of a longitudinal glow discharge

A system of equations has been solved that describes the positive column in a glow discharge in a cylindrical channel bearing a longitudinal gas flow.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 48, No. 2, pp. 289–296, February, 1985.     

The effect of He or Ar/O2 plasma treatment on Si surface prior to chemical vapor deposition of SiO2

The effect of O₂ plasma pretreatment on the SiO₂/Si interface property was studied using direct plasma varying the plasma power, He or Ar/O₂ ratio and the pretreatment time. The decrease of the pretreatment plasma power decreased the plasma damage and improved the interface property. The addition of He in O₂ glow discharge improved the electrical and the interface properties and there was an optimum He/O₂ ratio. The improvement of the interface property by Ar/O₂-plasma pretreatment was better than that by He/O₂, which is believed to be due to the lower oxidation rate of the Si surface. C–V analysis showed that the P_b center defect density was influenced by plasma pretreatment process parameters. To investigate the oxidation states near to and at the SiO₂/Si interface, X-ray photoelectron spectroscopy depth analysis was used and the gas phase in the glow discharge was investigated using optical emission spectroscopy analysis at various experimental conditions.     

The Effect of a Longitudinal Magnetic Field on the Radiation of Glow Discharge in Helium

The effect of a longitudinal magnetic field on the radiation of a glow discharge in helium is investigated experimentally. It is demonstrated that, with pressures in the discharge chamber below approximately 140 Pa, the intensity of radiation of spectral lines of helium and of continuous spectrum increases by a factor of 200–300 under the effect of a magnetic field. So strong an increase in the radiation of glow discharge in helium is observed in the region where no electric field of discharge is present. An attempt is made at attributing the obtained result to the decrease in the ambipolar diffusion of electrons to the wall; this brings about an increase in the density and temperature of electrons which start exciting metastable states of helium.__________Translated from Teplofizika Vysokikh Temperatur, Vol. 43, No. 4, 2005, pp. 516–525.Original Russian Text Copyright © 2005 by I. M. Ulanov and A. Yu. Litvintsev.     

Diagnostics of Surface-Plasma Formations in a Pulsed Surface Discharge

The main parameters (temperature and electron concentration) of the plasma formed in the near-wall and near-electrode regions of a high-current pulsed surface discharge with separate torches at atmospheric and lower pressures have been determined and analyzed. The mechanism of failure of the face (working) surface of cylindrical electrodes and a dielectric surface has been investigated on the basis of analysis of heat flows. The surface and open discharges were compared.__________Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 78, No. 2, pp. 165–171, March–April, 2005.     

等离子体化学气相沉积参量对Ar等离子体电子特性的影响

采用加热的调谐单探针技术。研究了射频辉光放电Ar等离子体空间电子能量分布函数,电子平均能量和电子密度,并系统分析了等离子体增强化学气相沉积工艺参量对等离子体空间电子特性的影响。     

Glow discharge source interfacing to mass analyzers: theoretical and practical considerations

The fundamental requirements for the optimum mechanical interface between a glow discharge ion source and a mass spectrometer are described in this paper. Specifically, the properties of a typical glow discharge ion source are compared and contrasted to those of a typical inductively coupled plasma ion source. The critical parameters and theoretical considerations of glow discharge and inductively coupled plasma ion source interfaces are reviewed, and the results of experiments using both quadrupole and time-of-flight mass spectrometers with a glow discharge source are presented. The experimental results clarify several important problems in the glow discharge ion sampling process. Our findings indicate that a shock wave structure does not occur in the supersonic expansion of the glow discharge ion source. Ions of different masses have similar initial kinetic energies in the glow discharge; thus, the angle of the skimmer cone is not a critical parameter for efficient ion beam extraction. Another consquence is that space charge effects in glow discharge ion sources repel heavy ions farther off axis than light ions. Thus, there are distinct and fundamental differences between glow discharge and inductively coupled plasma ion sources which are relevant to both ion sampling and ion extraction processes.     

Transition of an atmospheric-pressure glow discharge from the diffuse to spark phase

The dynamics of glow and the electrical characteristics of a nanosecond glow discharge in the course of a transition from the diffuse to spark phase have been studied in a rod-plane electrode geometry in air at atmospheric pressure. For this purpose, a sequence of alternating-polarity voltage pulses with an amplitude decaying from 135–170 kV was applied to the interelectrode gap with a length of 5–6 cm. It is established that the spark channel formation is preceded by the stage of diffuse glow and that the spark parameters are correlated with the statistical features of the stage of gap shortage (bridging) preceding the diffuse glow. This analysis also revealed the important role of thermal processes in the dynamics of glow discharge development.     

Use of a transverse nanosecond discharge at the prebreakdown electron ionization multiplication stage for selective excitation of neon atoms

An investigation is made of the characteristics of a transverse nanosecond discharge in Ne/SF₆ and He/Ne/SF₆ mixtures at the prebreakdown electron ionization multiplication stage. The conditions needed to obtain a stable transverse discharge with ultraviolet spark preionization are studied as well as the spectral and temporal characteristics of the plasma radiation. It is shown that this transverse discharge burning regime may be promising for the selective excitation of neon atoms which may be used to develop an electric-discharge, λ=585.3 nm, Ne(3s–3p) plasma laser. Pis’ma Zh. Tekh. Fiz. 24, 85–90 (January 12, 1998)     

Localization of pulsed energy deposition in a transverse surface discharge initiated in a gas flow with shock wave

The localization of a nanosecond transverse surface discharge initiated in a plasma sheet sliding over a dielectric surface in a channel featuring gas flow with a plane shock wave has been studied by monitoring glow intensity distribution at the discharge-ionized channel surface in the presence of the shock wave. Judging from the glow pattern, the entire energy of discharge is usually localized in a low-pressure region in front of the propagating shock wave. The density of energy deposited in front of the shock wave can be varied (in particular, increased up to 12–15 eV per particle) by initiating the discharge at various positions of the shock wave. Transitions from the discharge with glow localized sharply in front of the shock wave to the regimes with glow extended behind the front or with a volume glow region ahead of the shock wave were observed for certain values of the Townsend parameter (E/P) and Mach number (M).     

Parameters of the positive column of glow discharge with dust particles

We calculate the measured nonlocal parameters of the plasma of the positive column of direct current glow discharge in the presence of dust structures with different dust particle concentrations. The calculations are performed for typical conditions of the positive column of low-pressure glow discharge in air at which a collisional regime of maintaining discharge is achieved. The discharge plasma is described using the diffusion approximation; the flows to the surface of the dust particles are described in the orbital motion limited approximation. Calculation is carried out for micron-size particles with concentrations of up to 10¹¹ m^?3. The distribution of the dust component is assumed to be independent of the discharge parameters. Radial distributions of the plasma components and of the electric field component are obtained. The charges of dust particles for various concentrations and discharge parameters are calculated. It is demonstrated that for a certain particle concentration, the absorption efficiency of plasma particles becomes comparable with diffusion losses at the tube walls. The influence of the dust cloud on the electric field configuration at different dust particle concentrations in the cloud is analyzed. The current-voltage characteristics of the positive column of glow discharge are calculated. A higher discharge stability toward the perturbative action of dust particles at high discharge current values is demonstrated.     

The application of the glow discharge to material processing

The mechanism and characteristics of the glow discharge are outlined. Energetic electrons and ions, which are generated in the cathode fall region, may be focused or guided to form a beam by geometrical arrangements of the discharge electrodes and by magnetic fields. Two practical arrangements are described: a spherical hollow cathode device, which produces a hot zone at its centre; and a hollow anode device, which produces wellcollimated electron and ion beams. Glow discharge beam devices work at rough vacuum pressures, in the range 10^–2 to 1 mm Hg, and are particularly suited to the processing of glass and oxide ceramics since, owing to the presence of plasma, no electrical charging of target insulating materials takes place. Limitations are set on the operating conditions of glow discharges by the heat input to the electrodes, by erosion due to sputtering, and by the glow-to-arc transition. Proper engineering, however, should allow cathode current densities of the order of 1 A/cm² when operated at an anode voltage of the order of 10 kV, and focusing should realise electron beam power densities of up to the order of 1 MW/cm², with efficiency of about 50%. Thus, the glow discharge may have a wide range of applications to material processing, from etching by sputtering at low power to processing by the most intense heating. New methods of forming and fabricating oxide bodies based on condensation of vapour and on powder deposition are discussed.     

Investigation of dynamic characteristics of a glow discharge in gas flows

Stability of the gas-discharge-supply circuit system relative to current fluctuations is examined. The estimates are in agreement with investigations of a glow discharge in an air flow.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 56, No. 6, pp. 960–966, June, 1989.     

Modeling heat transfer I a glow discharge in the stationary mode

The temperature field of a stationary glow discharge in a gas-discharge chamber is investigated by using modelling of the heat transfer processes. The solution of the problem was obtained on the basis of an asymptotic expansion of the equations.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 56, No. 6, pp. 966–970, June, 1989.     

Spark Stage of Welding Arc Discharge Binding on an Aluminum Surface

The article presents a study of the spark stage of binding of the welding arc discharge on the surface of aluminum covered by oxide film. The experiments have shown the formation of cathode- and anodedirected leaders in a nonuniform field between the pin cathode (tungsten) and the plate (aluminum). It has been found that, if the cathode spot occurs against the background of uniform discharge glow, then the spark channel forms, as a rule, in two stages. At the first stage, a diffuse channel bound to the cathode spot that forms in the gap. At the second stage, a highly conductive contracted spark channel spreads from the cathode side along the diffuse channel; the brightness of that spark channel is comparable to that of the cathode plasma glow. From the color spectrum, it has been found that intensive aluminum emission takes place in the domain of binding spots already at the stage of avalanche-streamer spark formation. The estimated calculation of the heat flux rate in the binding spot of the spark discharge has shown values of 10⁶–10⁸ W/cm², i.e., comparable to laser heating parameters. The spark discharge exerts a significant thermal impact consisting of melting of the surface in the spark binding zone and the development of the recrystallization process of an amorphous film matrix in the zone of thermal effect. Electron diffraction through the thin film layer in the thermal effect zone has shown clear concentric rings corresponding to the polycrystal γ-phase of Al₂O₃. According to transmission electron microscope data, the average size of γ-phase grains in the surface film layer after impact by the spark is d = 8–15 nm, whereas the volume of the produced γ-phase is at least 70%. The stable thermodynamic α-phase in the melting zone has been fixed. By the moment of arc discharge excitation, the entire aluminum surface in the spark-binding zone has been free of oxide film.     

The analyses of an SiF4 plasma in an R.F. glow discharge for preparing fluorinated amorphous silicon thin films

The measurements of plasma parameters, such as an electron energy and an electron energy distribution function using a probe method, and of the optical emission spectroscopy for observing the chemical reactions in a plasma were studied for characterizing the glow discharge SiF₄ plasma. The probability of a basic dissociation process of the SiF₄ molecule by the electron impact was supported by the optical emission and also by the electron energy in the plasma. The discussions as to the electron energy distribution function in an r.f. glow discharge plasma suggest that a mean electron energy obtained by a double-probe method may not be very critical.The contribution of atomic hydrogen radicals and the probable reactions responsible for the deposition in the gas phase and/or on the substrate surface are also discussed.     

Electric field reversal in near-cathode region of glow discharge in helium

Longitudinal distributions of plasma parameters in a short (free of positive column) glow discharge in helium show evidence for the formation of a potential well for thermal electrons and the reversal of electric field in plasma of negative glow and Faraday dark space. Depending on the reduced discharge length pL, one or two points of field reversal can appear, which determines the sign of the anode fall.     

Influence of the initial composition of a methane-argon mixture on the electricophysical parameters and plasma composition of DC glow discharge

High Temperature - The stationary parameters and composition of DC glow discharge plasma (p = 40–200 Pa, i = 30–70 mA) in CH4-Ar mixtures of different compositions have been studied by...     

A Nanosecond High-Current Discharge in a Supersonic Gas Flow

The parameters of a nanosecond self-sustained volume discharge with pre-ionization of gas by UV radiation in an air flow are investigated. In the case of nonuniform distribution of the flow parameters, the discharge “contracts” to regions of lower density of gas, which become sources of higher intensity of glow. Comparison is made of the specific energy release in the self-sustained discharge at the stage of its uniform combustion and during self-localization in the zone of discontinuities (gradients) of gasdynamic parameters. It is demonstrated that, in the latter case, the effect of discharge on the characteristics of flow may increase significantly owing to an appreciable growth of specific energy deposition.     

Glow discharge mass spectrometric analysis of atmospheric particulate matter

A direct current (dc) glow discharge mass spectrometer has been used to analyze atmospheric particulate matter. The sample preparation used is simple and time-saving. The air is sucked by a pump through a single-orifice impactor stage, in which the aerosols are impacted on a metal support, forming a central spot. This metal plate is directly used as a cathode in a dc glow discharge mass spectrometer. Evaluation of the sample loading and of the discharge parameters allowed us to optimize the signal intensity and to minimize its decrease, the latter being a consequence of its consumption by continuous sputtering in the discharge. The available aerosol analysis time could be prolonged to more than 3 h, a time span necessary to perform a multielement analysis using a magnetic sector instrument and long integration times. A NIST reference aerosol was measured to evaluate the quantitative analysis potential. The internal reproducibility was better than 10% RSD, and the limits of detection were estimated to be in the low ppm or sub ppm region. Even without the use of any standards or correction factors, glow discharge mass spectrometry could offer good semiquantitative results, based only on the use of an internal standard.