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Diagnostics spectroscopiques d'espèces carbonées et modélisation physico-chimique de plasmas micro-ondes dans les mélanges H2/CH4 et Ar/H2/CH4 utilisés pour le dépôt de diamant

Abstract : The work presented in the frame of this thesis dealt with spectroscopic diagnostic and modelling of 2.45 GHz-microwave plasmas obtained under moderate pressure using a cavity coupling system in H2/CH4 and Ar/H2/CH4 mixtures. These plasmas are suitable for the deposition of poly- and nano crystalline diamond films, respectively. The density of methyl radical (CH3), which is assumed to be the main growing species for poly crystalline diamond deposition (H2/CH4 plasmas), was determined using two absorption techniques : a UV Broadband Absorption Spectroscopy (BAS) at 216 nm and IR Tuneable Diode Laser Absorption Spectroscopy (TDLAS) around 606-612 cm-1 (16.5 µm). To our best knowledge, these two techniques were for the first time used simultaneously on the same system. The results obtained from the two diagnostics showed a good agreement in a relatively wide range of experimental conditions. The TDLAS setup was used to quantify hydrocarbon stables species in the discharge, such as CH4, C2H2, C2H4, C2H6. Since BAS and TDLAS are line of sight averaged techniques, the analysis of the experimental data required the use of a 1 D non-equilibrium transport model that provides species-density and gas temperature variations along the optical beam. This model describes the plasma in term of 28 species/131 reactions reactive flow. The thermal non-equilibrium is described by distinguishing a first energy mode for the electron and a second one for the heavy species. A similar 1 D model was developed to describe the discharge along the axial direction of the reactor perpendicularly to the substrate surface. The use of this model allowed a better understanding of the coupling between plasma kinetics, energy transfer and species and energy transport toward the growing surface. Ar/H2/CH4 discharges were investigated using UV and visible BAS that enabled us to investigate the Mulliken (231 nm) and Swan (516 nm) spectroscopic systems of the C2. This radical is assumed to be the main precursor for nano-crystalline diamond formation. This investigation allowed determining the temperature and density of C2. Results yield a gas temperature around 3500 K and C2 density ranging between 5 x 1013 and 1014 cm-3, which is in fairly good agreement with the results obtained from a 0 D quasi-homogenous thermo-chemical model.
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https://tel.archives-ouvertes.fr/tel-00007244
Contributor : Guillaume Lombardi <>
Submitted on : Thursday, October 28, 2004 - 10:26:53 PM
Last modification on : Monday, October 19, 2020 - 11:11:57 AM
Long-term archiving on: : Friday, April 2, 2010 - 9:13:02 PM

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  • HAL Id : tel-00007244, version 1

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Guillaume Lombardi. Diagnostics spectroscopiques d'espèces carbonées et modélisation physico-chimique de plasmas micro-ondes dans les mélanges H2/CH4 et Ar/H2/CH4 utilisés pour le dépôt de diamant. Physique Atomique [physics.atom-ph]. Université Paris Sud - Paris XI, 2003. Français. ⟨tel-00007244⟩

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