Bonn 2000 – wissenschaftliches Programm
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P: Plasmaphysik
P 16: Plasmadiagnostik (Poster)
P 16.38: Poster
Mittwoch, 5. April 2000, 10:30–13:00, Aula
On the hydrocarbon chemistry in a surface wave discharge containing methane — •L. Mechold1, J. Röpcke1, X. Duten2, and A. Rousseau2 — 1Institut für Niedertemperatur-Plasmaphysik, Greifswald, Germany — 2Laboratoire de Physique des Gaz et des Plasmas, CNRS, Orsay, France
The dissociation of methane and the conversion into higher hydrocarbons in a variety of PECVD processes is of interest because plasmas are frequently used to deposit thin films. The monitoring of transient or stable plasma reaction products, in particular, the measurement of their ground state concentrations, is the key to improved understanding of the plasma chemistry. The contribution will describe recent studies of the hydrocarbon chemistry in a surface wave discharge (f = 2.45 GHz, P = 600 W) in hydrogen plasmas containing few percent of CH4 using infrared tunable diode laser absorption spectroscopy (TDLAS). The methyl radical was one of the main species of interest. Its concentration was found at about 1012 molecules cm−3. In addition the molecular concentrations of CH4, C2H2, C2H4 and C2H6 have been measured in a relatively wide range of flow rate (22 - 385 sccm) and pressure (0.1 -4 Torr). For the first time the dissociation of CH4 and the production of C2H2, C2H4 and C2H6 was measured time-resolved under static conditions. While the precursor gas molecule methane shows a decraesing concentration with time a maximum was found for the stable hydrocarbons produced in the plasma. For the TDLAS measurements the IRMA system was used [1].
[1] J. Röpcke et al, Frontiers in Low Temperature Plasma Diagnostics III, Saillon 1999, Conf. Proc., 113 (1999).