N. S. Sochugov

Optical studies of plasma inhomogeneities in a high-current pulsed magnetron discharge

Results are presented for experimental studies of the plasma glow in a high-current pulsed magnetron discharge by using a high-speed optical frame camera. It is found that the discharge plasma is inhomogeneous in the azimuthal direction. The plasma bunches rotate with a linear velocity of ∼1 cm/μs in the direction of electron Hall drift, and their number is proportional to the discharge current. Plasma inhomogeneities in the form of plasma jets propagate in the form of plasma jets from the cathode region toward the anode. It is shown analytically that the formation of inhomogeneities is caused by the necessity to transfer high-density electron current across the magnetic field.

a-C:H films deposited in the plasma of barrier and surface discharges at atmospheric pressure

The aim of this work is the synthesis of the diamond-like coatings in a barrier and surface discharges at the atmospheric pressure and the investigation of their properties. The best characteristics had the coatings obtained from methane (the ratio of hydrogen atoms to carbon atoms is H/C=1.04, the ratio of the diamond-like and graphite-like C-C bonds sp 3 :sp 2 100%:0%) and from the acetylene and hydrogen mixture (1:19) (H/C=0.73, sp 3 :sp 2 = 68%:32%) in barrier discharge, as well as from methane in surface discharge (H/C =0.69-1.03, sp 3 :sp 2 =78%:22%). By their chemical and phase composition these coatings are close to the diamond-like hydrogenated (a-C:H) films obtained by traditional methods of plasma assisted chemical vapor deposition at low pressure (<10 Torr). At the same time proposed methods for fast deposition of a-C:H films make this process less expensive compared to the conventional techniques, which implies that the field of application of these films can be widened substantially.

Ion-assisted pulsed magnetron sputtering deposition of ta-C films

Abstract The process of ion-assisted deposition of ta-C films by pulsed magnetron sputtering of a graphite target has been investigated. Probe measurements of the magnetron discharge plasma have been performed and its space- and time-dependent characteristics have been obtained as functions of the sputtering parameters and the bias voltage applied to the substrate. It has been shown that the density of the pulsed magnetron discharge plasma approaches values typical of pulsed laser or vacuum arc cathode sputtering of graphite (1017−1018 m−3). Raman scattering was used to examine the ta-C films produced at both low and high pulsed bias voltages applied to the substrate (Usub

Plasma-Chemical Conversion of Lower Alkanes with Stimulated Condensation of Incomplete Oxidation Products

Oxidative conversion of a mixture of natural gas and oxygen in a barrier-discharge plasma-chemical reaction was investigated experimentally. The process was conducted at atmospheric pressure and room temperature. The discharge was initiated by high-voltage pulses of 50–100 μs duration at a repetition frequency of up to 2 kHz. The principal feature of the process was that in the plasma-chemical reactor conditions were created which stimulated the condensation of the products of incomplete oxidation of methane that resulted in the formation of aerosol even from nonsaturated vapor. The removal of intermediate reagents from the gaseous phases into the aerosol prevented them from further oxidation. Depending on the experimental conditions, the mass percentage of the components of the condensate formed varied within the following limits: formic acid from 20 to 40%, methanol from 8 to 15%, methylformate from 4 to 8%, and water from 40 to 60%. The conversion process has been realized on a laboratory setup of average power up to 1 kW. In the single-pass mode, a 57% degree of conversion of the mixture has been achieved. The energy value of the condensate is 15–20 kWh/kg.

Mid-temperature solid oxide fuel cells with thin film ZrO2: Y2O3 electrolyte

Data on the mid-temperature solid-oxide fuel cells (SOFC) with thin-film ZrO2-Y2O3 (YSZ) electrolyte are shown. Such a fuel cell comprises a carrying Ni-YSZ anode, a YSZ electrolyte 3–5 μm thick formed by vacuum ion-plasma methods, and a LaSrMnO3 cathode. It is shown that the use of a combined method of YSZ electrolyte deposition, which involves the magnetron deposition of a 0.5–1.5-μm thick sublayer and its pulse electron-beam processing allows a dense nanostructured electrolyte film to be formed and the SOFC working temperature to be lowered down as the result of a decrease in both the solid electrolyte Ohmic resistance and the Faradaic resistance to charge transfer. SOFC are studied by the methods of voltammentry and impedance spectroscopy. The maximum power density of the SOFC under study is 250 and 600 mW/cm−2 at temperatures of 650 and 800°C, respectively.

Production of large-area coatings on glasses and plastics

Abstract This article describes an extended DC magnetron with a cylindrical cathode. The magnetron design provides for sputtering the cathode material on two opposite sides, allowing one to deposit coatings simultaneously on two plane substrates of area up to 2×3 m2. An extended ion source of magnetron type designed for cleaning and modification of the substrate surface prior to coating deposition is described as well. The characteristics of low-emissivity coatings on glasses and of conductive coatings on plastics are given. An electric circuit for pulsed power of a magnetron sputtering system, based on an artificial pulse-forming line, is proposed. The results of experiments where diamond-like films were deposited on large-area substrates by the method of pulsed magnetron sputtering of a graphite target synchronized with a pulsed high-voltage bias applied to the substrate are presented.

Investigation of Plasma Characteristics in an Unbalanced Magnetron Sputtering System

Results are presented from experimental studies of a magnetron sputtering system for different configurations of the magnetic field above the cathode surface. The current-voltage characteristics of a magnetron discharge at different working gas pressures (0.08–0.3 Pa) and currents in the unbalancing coil were studied. The production and transport of charge carriers in a magnetron discharge with an unbalanced magnetic field was investigated by means of probe measurements of plasma characteristics and ion energies in the region between the substrate and the magnetic trap at the cathode surface. The radial distributions of the ion current density, plasma potential, and floating potential in the unbalanced operating mode are found to have pronounced extrema at the magnetron axis. It is shown that the plasma density near the substrate can be increased considerably when the axial magnetic field is high enough to efficiently confine plasma electrons and prevent their escape to the chamber wall.

Properties of diamondlike films obtained in a barrier discharge at atmospheric pressure

Diamondlike films are synthesized from gaseous hydrocarbons in a barrier discharge at atmospheric pressure. The films were investigated using transmission electron microscopy, electron diffraction, and infrared spectroscopy. A technique for determining the quantitative characteristics of the films (hydrogen content, ratio of different types of carbon-carbon bonds and hydrocarbon groups) using standard samples is described. The highest-quality films were obtained from methane (ratio of hydrogen to carbon atoms H/C=1.04, fraction of diamondlike to graphitelike bonds sp3: sp2=100%: 0%) and from a mixture of acetylene and hydrogen in the ratio 1:19 (H/C=0.73, sp3: sp2=68%: 32%).

Deposition of highly adhesive amorphous carbon films with the use of preliminary plasma-immersion ion implantation

Abstract The usability of the following two types of plasma generators for deposition of highly adhesive a-C:H films on the large area substrates has been studied: (1) a source of plasma generated by means of a non-self-sustained arc discharge in low-pressure gas; and (2) an ion-plasma source on the basis of a Hall current accelerator with closed electron drift. The distinctive features of both sources are: (a) the possibility of the generation of extended flows (up to 2 m) of relatively dense plasma (∼10 10 cm −3 ); and (b) control of the plasma ionization degree, allowing realization of both preliminary plasma-immersion ion implantation (PIII) of a substrate and subsequent plasma-immersion ion-assisted deposition (PIID) of a-C:H film. The results of experimental investigations into the characteristics of the sources in different operational regimes are presented. Taking into account the probe measurements of plasma parameters, both generators have been optimized to operate in the PIII and PIID regimes. Characteristics of the pulsed negative bias applied to the substrate in both regimes have also been determined. It was shown that both sources allowed deposition of a diamond-like film on large-area substrates with a growth rate of 100–300 nm h −1 . A hard (20–30 GPa) a-C:H coating containing approximately 60% of carbon atoms with sp 3 hybridization and having satisfactory adhesion to the substrate can be obtained if short (∼60 μs) high-voltage (∼6 kV) bias pulses are applied to the substrate.

Use of the hydrocarbon plasma of a low-pressure arc discharge for deposition of highly adhesive a-C:H films

Abstract It has been investigated whether a source of a hydrocarbon plasma generated by a non-self-sustained low-pressure arc discharge is suitable for production of highly adhesive a-C:H films. The distinguishing feature of this plasma source is the possibility for varying the degree of plasma ionization and the degree of destruction of hydrocarbon gases, making possible to realize both pure plasma-immersion ion implantation (PIII) and plasma-immersion ion deposition (PIID) in a unified vacuum cycle. The plasma parameters were measured with probes as functions of discharge current. Based on these measurements, the parameters of plasma generator have been determined for the PIII and PIID operation. The parameters of the pulsed bias voltage applied to the substrate in the process of the ion implantation and growth of an a-C:H film have also been preliminary chosen. For PIID it has been demonstrated that the improvements in quality of the a-C:H coating and in its adherence to the substrate are attained when an energy per carbon atom built in the coating is lying in the range 200–500 eV. The growth rates of a-C:H films in this case are approximately 200–300 nm/h. It was shown that the most favorable for achieving high energies per deposited carbon atom and for reducing of residual intrinsic stress are short (∼60 μs) high-voltage (>1 kV) substrate bias pulses.