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Nucleation, growth and behavior of dust particles in reactive low pressure radiofrequency plasmas: From nanocrystals to submicron polycrystalline grains.

Abstract : Ionized gases containing fine solid particles, called dusty plasmas, are used mainly to deposit nanostructured thin film layers and to synthesize nanoparticles with controlled properties.
The main objective of this PhD thesis was to succeed in synthesizing dust particles of desired size and/or chemical composition, for applications in microelectronics, photovoltaic conversion (silicon nanocrystals) and astrophysics (tholins, ISD grains).
The localization and the study of the beginning of the aggregation phase have been performed through a parametric study of an instability in Argon/Silane plasmas. Then, a study of the dust cloud shape and behavior has been performed in two different discharges. Those studies brought to the fore the strong influence of dust particle growth on both the plasma characteristics and the dust cloud. They allowed us to optimize our deposition parameters to synthesize single-crystal silicon nanoparticles. A parametric study of the electrical characteristics of the plasma (current, voltage, electron and ion densities) in Nitrogen/Methane allowed us to target the best parameters to synthesize tholins (Titan's aerosol analogues). Moreover, in-situ Mie-Rayleigh ellipsometry in Nitrogen/Acetylene plasmas gave us information concerning the synthesized ISD grains structure, optical index). Finally, low gas temperature effects have been investigated in order to increase the size of the single-crystal silicon nanoparticles. Different hypothesis (chemical and thermodynamical) are discussed in order to explain the obtained results: dust formation kinetics accelerated and increase in the nanocrystal size.
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Submitted on : Thursday, April 17, 2008 - 3:50:21 PM
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  • HAL Id : tel-00274266, version 1

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Marjorie Cavarroc. Nucleation, growth and behavior of dust particles in reactive low pressure radiofrequency plasmas: From nanocrystals to submicron polycrystalline grains.. Physics [physics]. Université d'Orléans, 2007. English. ⟨tel-00274266⟩

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