L. Maillé

Microwave plasma chemical vapour deposition of tetramethylsilane: correlations between optical emission spectroscopy and film characteristics

Abstract In a tetramethylsilane (TMS) (Si(CH 3 ) 4 )/argon microwave discharge used for deposition, optical emission spectroscopy (OES) measurements are carried out along the reactor axis between the precursor inlet and the deposition surface which is independently heated. The results are examined in connection with the deposit features. The changes in the relative amounts of the detected species such as H, Si + , H 2 , CH, C 2 , SiH and SiC 2 highlight competitions between the decomposition of the precursor and recombinations in the plasma flow. This leads to the occurrence of reactive bond carriers SiC, CC, CH when close to the substrate. It appears that hydrogen is mainly carried to the growing surface through species bonded to carbon. Some film characteristics revealed by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) characterizations and hardness measurements are discussed and can be well correlated to trends detected in the gas phase. The interest of such films whose features (hardness and low dry friction coefficient) can be adjusted is underlined.

Elaboration of C/C Composites Based on the Infiltration of a Hydrocarbon Precursor in Supercritical State into the Preform

This paper reports on the development of a new process for the fabrication of a C/C composite for aeronautic and aerospace industries, in order to reduce the infiltration time of the carbon perform. The infiltration of a carbon fibrous preform by means of a hydrocarbon in the supercritical fluid state is done at high temperature in order to obtain a carbon matrix. The microstructure of the pyrocarbon coating is characterized by SEM and TEM. The experimental parameters (temperature, hydrocarbon pressure, residence time) are tuned in order to elaborate the carbon matrix. The best conditions lead to in-depth rapid densification from the top of the preform. After several experiments, the densification has been improved.