1. Infrared spectroscopic and modeling studies of H2/CH4 microwave plasma gas phase from low to high pressure and power.
- Author
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Rond, C., Hamann, S., Wartel, M., Lombardi, G., Gicquel, A., and Röpcke, J.
- Subjects
INFRARED spectroscopy ,INFRARED lasers ,SEMICONDUCTOR lasers ,MICROWAVE plasmas ,PLASMA gas research - Abstract
InfraRed Tunable Diode Laser Absorption Spectroscopy technique has been implemented in a H
2 /CH4 Micro-Wave (MW frequency f=2.45 GHz) plasma reactor dedicated to diamond deposition under high pressure and high power conditions. Parametric studies such as a function of MW power, pressure, and admixtures of methane have been carried out on a wide range of experimental conditions: the pressure up to 270 mbar and the MW power up to 4 kW. These conditions allow high purity Chemical Vapor Deposition diamond deposition at high growth rates. Line integrated absorption measurements have been performed in order to monitor hydrocarbon species, i.e., CH3 , CH4 , C2 H2 , C2 H4 , and C2 H6 . The densities of the stable detected species were found to vary in the range of 1012 -1017 molecules cm-3 , while the methyl radical CH3 (precursor of diamond growth under these conditions) measured into the plasma bulk was found up to 1014 molecules cm-3 . The experimental densities have been compared to those provided by 1D-radial thermochemical model for low power and low pressure conditions (up to 100 mbar/2 kW). These densities have been axially integrated. Experimental measurements under high pressure and power conditions confirm a strong increase of the degree of dissociation of the precursor, CH4 , associated to an increase of the C2 H2 density, the most abundant reaction product in the plasma. [ABSTRACT FROM AUTHOR]- Published
- 2014
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