Aachen PK 2003 – scientific programme
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P: Plasmaphysik
P 17: Poster III
P 17.29: Poster
Thursday, March 20, 2003, 17:30–19:15, Foyer
Expanding thermal plasma deposition of hydrogenated amorphous carbon films — •Jan Benedikt, Remco Woen, and Richard van de Sanden — Eindhoven University of Technology, P.O.Box 513, 5600 MB, Eindhoven, The Netherlands
Plasma chemistry in an Ar/C2H2 expanding thermal plasma (ETP) was studied by means of a Cavity Ring Down Spectroscopy (CRDS) and Mass Spectrometry (MS). CRDS was used for C, CH and C2 radical detection. It is demonstrated that C, CH and C2 are products of a secondary reaction chain of argon ions and electrons with radical products formed in the primary reaction of argon ions and electrons with acetylene. With MS, the consumption of acetylene in the plasma and the production of the C4H2, C6H2 and C6H6 molecules were measured. A plasma chemistry model was build, which can very well reproduce the measured data. Both measurements and model show that by increasing the acetylene injection flow the composition of the plasma can by controlled from a C, CH, C2 radical flux, C2H dominant radical flux to C4H2 molecule rich flux. Consequently the film properties and the growth rate can be controlled. The highest growth rate is reached at the moment when all radicals are reacted away in the gas phase with acetylene and that C4H2 probably deposits. The direct evidence corroborating this fact is the wall condition dependent C4H2 density in the reactor after switching on the plasma. The essential conditions for the sticking of C2H2 are plasma activated surface, internal excitation of these molecules and the high flux towards the surface.