Abstract

Maximizing dissociated species transport in plasma assisted chemical vapor deposition (CVD), is important in many low pressure plasma jet processes. To deposit high quality diamond by low pressure plasma assisted CVD, it is important to maximize the atomic hydrogen transport to the substrate. One route to process improvement is to explore ways in which unstable species transport can be maximized. A two-dimensional computational model of a supersonic contoured nozzle attached to a dc torch will be described for examining the chemical non-equilibrium of the flow. If the fluid dynamic time scales of interest are faster than the kinetic time scales of interest, it is believed that unstable precursor transport can be controlled, improved and optimized. This paper will examine an implicit formulation for the numerical simulation of a multi-component reacting Ar-H2 plasma. It is found that dissociation, ionization and charge exchange reactions must all be included in a reaction model. The ionic species significantly alter the temperature profiles upstream of nozzle choking. However, to increase the number of hydrogen atoms at the nozzle exit, the arc attachment should be positioned as close as possible to the converging-diverging nozzle throat.

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