R. A. Kornev

A study of silicon tetrafluoride reduction with hydrogen in radiofrequency discharge

The process of plasma-chemical conversion of silicon tetrafluoride in a radiofrequency (13.56 MHz) discharge has been studied. The dependence of the yield of silicon on the specific energy input and the H2/SiF4 molar ratio has been examined in the pressure range of 0.1–0.3 Tort. The maximum yield of silicon is 60%, and the optimal specific energy consumption is 44.6 MJ per mole of Si. A mechanism has been proposed for the plasma-assisted reduction of silicon tetrafluoride under the given experimental conditions.

Behavior of carbon-containing impurities during plasma synthesis of trichlorosilane

The behavior of CCl4 and CHCl3 admixtures during the plasma synthesis of trichlorosilane via the hydrogenation of SiCl4 in a capacitively coupled radiofrequency (40.68 MHz) discharge was studied. It was shown that the main portion of the impurities undergo chemical transformations yielding silicon carbide and carbon. The degree of conversion determined from the impurity concentrations in the reactant SiCl4 and its hydrogenation products is strongly dependent on the processing parameters and reaches 99.9% for CCl4 and 96% for CHCl3.

Catalytic effects of electrode material on the silicon tetrachloride hydrogenation in RF-arc-discharge

A silicon tetrachloride reduction in RF-arc-discharge (40.86 MHz) has been experimentally studied. The electrode material significantly affects the composition of the chlorosilanes in the gas phase at the outlet of the reactor which may be attributed to high and at the same time different catalytic activity of Cu, Ni, Nb, and Zr metals belonging to the transition of d-elements and W f-elements of the periodic table. The corrosion has been observed on the electrodes with the formation of chlorides of Cu, Ni, Nb, Zr, and W metals. In the system formed by two electrodes and plasma there are three main reactive regions in which the recovery of silicon tetrachloride by hydrogen at different flows is conducted independently from each other. The analysis of exhaust gases, chemically active plasma and condensed phase by emission-spectroscopy and GCMS spectrometry made it possible to propose the mechanism of formation of observed intermediate species and final products. On the basis of the obtained results we can conclude that this type of RF-plasma discharge includes two mechanisms of plasma chemical reactions: one with the participation of active particles formed in plasma and one initiated by the catalytically-active surface of the electrode.

Behavior of organochlorine impurities in the process of plasma-enhanced synthesis of trichlorosilane

The behavior of the impurity compounds C2H2Cl2, C2HCl3, C2Cl4, and C2H2Cl4 in the process of plasma-enhanced synthesis of trichlorosilane via the hydrogenation of SiCl4 in a capacitively-coupled radiofrequency (40.68 MHz) discharge was investigated. It has been shown that the concentration of the impurities substantially decreases during the synthesis of trichlorosilane. The degree of conversion determined in terms of the concentration of an impurity in initial SiCl4 and in its hydrogenation products depends on the pressure and reaches more than 80% for C2H2Cl2, C2HCl3, or C2Cl4 and 60% for C2H2Cl4.

Silicon tetrachloride conversion in microwave discharge hydrogen plasma

Silicon tetrachloride conversion in microwave discharge hydrogen plasma has been experimentally investigated. The main products of this process are silicon, hexachlorodisilane, and polychlorosilanes. The proportions of the products depend on specific energy input and on the place in which the reactants (SiCl4 and H2) are introduced into the plasma discharge zone. The conditions ensuring a 90% silicon yield have been determined. The gas dynamic and heat transfer processes in a cylindrical reactor have been numerically simulated for these conditions. The temperature interval in the discharge zone (2000–2500 K) and the rate of quenching of products (silicon-containing radicals) have been estimated. Experimental data of this study and their comparison with data available from the literature suggest a hypothesis concerning the reactions responsible for the formation of silicon, hexachlorodisilane, and polychlorosilanes.

Synthesis of 28SiC from 28SiF4 and Methane in Radiofrequency (13.56 MHz) Arc Hydrogen Plasma

Some features of atmospheric-pressure radiofrequency (13.56 MHz) arc discharge and its use for obtaining bulk samples of isotope-enriched silicon carbide via the reaction between SiF4 and methane in a hydrogen medium have been considered. It has been shown that power in this type of discharge is released mainly in the near-electrode regions. The deposition of silicon and graphite occurs in a layer-by-layer mode, so that the product carbide contains up to 40% free carbon; therefore, the process requires optimization. At the same time, the proposed type of RF arc discharge with the product deposition zone localized at the ends of the electrodes makes it possible to avoid not only additional heating of the reactor space and walls, but also the loss of expensive isotope-enriched silicon fluoride.

Gas-dynamic and thermal processes in a high-frequency induction plasma torch with tangential stabilization of the gas flow

The gas-dynamic and heat-exchange processes in a coaxial type plasma torch with tangential stabilization of the gas flow and a central inlet for feeding the raw material into the high-temperature region of plasma at atmospheric pressure were studied. The temperature range in the high-temperature zone (3500–4000 K) and near the plasma torch walls (930–1400 K) and the residence time of the reaction mixture in the high-temperature zone were estimated. The peculiarities of the gas flow motion using a feed probe were considered. The results, in comparison with the experimental operating modes of the plasma torch, make it possible to proceed to the construction of a plasma torch of higher productivity.

Features of germanium tetrafluoride reduction with hydrogen in inductively and capacitively coupled radiofrequency discharges

The process of plasma-chemical conversion of germanium tetrafluoride in a radiofrequency discharge (13.56 MHz) has been studied. The dependences of the germanium yield on the specific energy input, the H2/GeF4 molar ratio, and the total pressure have been measured. The maximum germanium yield is more than 95%. The minimum specific energy consumption at an energy input of 9 MJ/mol is 9.4 MJ/mol or 2.6 kW h/mol Ge. A mechanism of plasma-assisted reduction of germanium tetrafluoride under the given the experimental conditions has been proposed.

Reduction of Silicon Tetrachloride with Hydrogen in a Chemically Active Plasma

Gas-dynamic and thermal processes occurring in a UHF reactor under optimal conditions for the preparation of silicon have been modeled. The distribution of the gas temperatures, the residence time of the reagents in the high temperature zone, and the rate of quenching of the reaction products have been determined. A mechanism for the formation of silicon with participation of H·,

Preparation of glasses in the Ge-S-I system by plasma-enhanced chemical vapor deposition

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