DIAMOND FILM PREPARATION BY ARC-DISCHARGE PLASMA-JET-CVD AND THERMODYNAMIC CALCULATION OF THE EQUILIBRIUM GAS-COMPOSITION

In order to obtain a high growth rate of diamond, the DC plasma-jet chemical vapor deposition technique has been used. The plasma consists of argon (99.998%) and hydrogen (99.9%). CH4 (99.5%) is used as a carbon source and is mixed into the plasma jet. The plasma jet is sprayed onto a substrate fixed on a water-cooled substrate holder. The mean growth rate of diamond obtained on Si (111) and Mo substrates with this technique is approximately 80 μm/h. The influence of the synthesis parameters CH4 H2 gas ratio and the temperature of the substrate on the morphology and the properties of the diamond film have been examined by scanning electron microscopy, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, and Vickers hardness. It was found that the quality of the deposits came close to that of natural diamond. Additionally, the equilibrium concentrations of the various hydrocarbon species in the gas phase for the CH4ArH2 gas system, temperatures from 500 to 6000°C and a total pressure of 0.25 atm (25 kPa) has been computed using the thermodynamic computer program "microtherm and sage". It was found, that at temperatures, typical for the gas film near the surface of the substrate, C2H2 and C2H are the most important species. © 1992.