Etude de la formation de poudres par plasmas basse pression à partir de vapeurs d’hexamethyldisiloxane et à partir de méthane.

Abstract

This work is concerned with the study of powders created in low pressure plasma in hexamethyldisiloxane vapors and the study of powders created by plasma torch from a mixture of CH4 / H2. The formation of powders in the gas phase of the HMDSO vapors was detected by monitoring the electrical signal delivered by the plasma generator that we carried out and by studying the luminescence of the plasma by optical emission spectroscopy. This latest diagnostic technique has shown that the evolution of emission intensities of Si-O and Si-H species is related to the formation of powders. The SEM observations of the deposits made, showed the presence of powders on the substrates, the size and shape of which depend on the deposit parameters. Analysis of thin layers produced by FTIR spectroscopy and EDX microanalysis of powders have shown that the latter are of the SiOxCy: H type. We have developed a new way to synthesize at room temperature, starting from a methane / hydrogen mixture, powders rich in nanodiamond particles using a microwave plasma microtroche that we have produced locally. The gas phase of the micro-torch plasma was characterized by high-resolution optical emission spectroscopy and determined the gas temperature as well as the electron density of the micro-torch plasma. The morphology, structure and composition of the nanoparticles that we deposited by this method were made by SEM and TEM microscopy, by Raman spectroscopy and EELS. These characterization techniques have clearly confirmed the presence of nanodiamond for certain deposition conditions.