Modeling studies of diamond deposition with thermal plasmas

Summary form only given. In the case of a special DC plasma jet facility the DC plasma jet generation zone is modeled in a simple way with the given plasma power and the gas flow rates of the individual species. Based on that information of velocity, temperature, pressure, plasma density and number densities of the species in the nozzle exit plane are obtained. Next, the flow, energy and composition fields in the reactor are determined. Continuity, Navier-Stokes, conservation of energy, conservation of chemical species equations and equations of state are used for this purpose. It is assumed that the flow is generally two-dimensional, viscous, with variable transport properties, compressible (subsonic/supersonic), chemical reacting, and is treated as continuum. The chemical kinetics rates for ionization as well as chemical reactions are taken from the literature. The flow is in thermodynamic equilibrium. The substrate surface processes constitute the boundary conditions for the flow modeling. They include the energy and species exchange between the gas and the substrate. While the energy exchange is fully described by media thermal conductivities, separate models are used for the surface chemical kinetics. The model gives some interesting results. It can be shown that the better match of the pressure in the nozzle region of the plasma torch to that of the plasma reactor improves, as expected, the stability of the plasma flow.