AN OVERALL MECHANISM FOR THE DEPOSITION OF PLASMA POLYMERS FROM METHANE IN A LOW-PRESSURE ARGON PLASMA-JET

An overall mechanism for plasma polymer deposition from a methane-seed ed argon plasma jet was established from experimental measurements and a simplified model of reaction kinetics within the plasma jet. Total mass deposition rates were obtained at various substrate positions and methane flow rates. Methane consumption was estimated from residual g as analysis. The influence of substrate coolant temperature on deposit ion rate was evaluated. The model was based on particle densities, jet temperature, and jet velocity data published previously, and reaction rate constants from the literature were used. No adjustable parameter s were employed in this model. Experimental results for total depositi on rate and methane consumption were in good agreement with model pred ictions, The overall deposition mechanism consists of three steps: Pen ning ionization of methane by excited argon neutrals, followed by diss ociative recombination of CH(x)+ to yield CH, followed by incorporatio n of CH into the growing film upon impact. Contributions of species ot her than CH to the total deposition rate are minor, and adsorption is not a prerequisite for incorporation into the growing film.