A PLASMA GENERATOR WITH SECTIONALIZED INTERELECTRODE INSERTS AND ITS USAGE IN A VACUUM SET-UP FOR DEPOSITING DIAMOND-LIKE FILMS

A cascaded arc plasma generator with interelectrode inserts (IEI) has been constructed to investigate the process of depositing of diamond-like films by using the thermal plasma CVD-method. The energy characteristics of the generator have also been carefully studied and analysed. The experimental data obtained indicates that it is advantageous to use sectionalized interelectrode inserts to achieve a better performance. Cool working gas is injected into the gaps between the thin sections to form a gaseous screen and produce better heating conditions. The internal diameters of the interelectrode inserts used in the plasma generator were varied in the range of 4 to 10 mm. Supplementary injections of argon into the gaps between the sections of the interelectrode insert make it possible to achieve a heating efficiency up to η=0.7 with the power of the plasma generator within the range of 2÷23 kW. The investigation shows that the current-voltage characteristics of the plasma generator tend to improve with the ratio of the arc current to the diameter of the discharge chamber exceeding 10 A/mm. This allows us to use conventional power supply sources with constant or slightly dropping voltage. The IEI plasma generator permits of producing supersonic Argon plasma jets, into which chemical reactants (such as C₂H₂, CH₄, H₂, etc.) are introduced. The chemical reactants can be introduced into the jet either at their outlet or directly into the discharge chamber of the plasma generator. The set-up makes it possible to vary the pressure of the gas in the chemical reactor in the range of 2·10² ÷ 8·10³ Pa which influences the film growth rate. The area of film deposition can be regulated by changing the configuration of the anode-nozzle of the generator. Raman Spectra analysis of the carbon films on molybdenum substrates obtained on the IEI plasma generator by the CVD method indicate a peak near 1332 cm⁻¹ which corresponds to the peak at which the sp³ lattice structure of natural diamond occurs.