EMISSION SPECTROSCOPY, MASS SPECTROMETRY AND KINETICS IN CH_4-CO_2 PLASMAS USED FOR DIAMOND DEPOSITION

摘要

Diamond deposition in microwave CH_4-CO_2 plasmas depends on various parameters that change the nature and the concentration of the various species in the plasma. The power density injected in the plasma appears to have a great influence. It is varied by changing both the microwave power and the pressure. Emission spectroscopy allows the determination of the ro-vibrational temperature and then the kinetic temperature of the heavy species. Mass spectrometry associated to a molecular beam sampling is used to study both the stable species (H_2, CH_4, CO, CO_2, …) and the radicals (H, OH, CH_3, C_3H_3, C_3H5_, …). At the highest power density, a reactor modelling allows to show that the kinetics in the plasma is very influenced by the gas temperature while the dissociation by electrons is necessary to initiate the mechanism at low power densities. It permits to correlate the experimental conditions with the etching/deposition domains.