The effect of boundary layer thickness on diamond film formation in an atmospheric pressure plasma was investigated by adding argon to the methane-hydrogen reactant jet so as to increase the jet momentum. It was found that argon addition significantly increased the range of conditions over which well-faceted, continuous diamond film could be grown. A numerical model was developed to predict the two-dimensional temperature and flow fields in the reactor and the one-dimensional chemical kinetics in the substrate boundary layer. An interesting outcome of these calculations is that the largest effect of thinning the boundary layer by adding argon to the central jet is a significant enhancement in the flux of monatomic carbon vapor to the substrate, and the experimentally observed results can be correlated with the calculated carbon fluxes.
Bibliographical noteFunding Information:
This work was partially supported by the National Science Foundation (CTS-9115464), by the Engineering Research Center for Plasma-Aided Manufacturing and by the Minnesota Supercomputer Institute.