Molecular beam mass spectrometry analysis of gaseous species responsible for diamond deposition in microwave plasmas

Abstract
This work aimed to the identification of the principal gaseous species involved in microwave plasmaassisted chemical vapor deposition of diamond from CO ₂-CH ₄ mixtures. The nature and concentration of the important precursors and etching species depend on the external controlled parameters. The influence of the inlet reactant composition is especially studied here. Mass spectrometry associated to molecular beam sampling is used to study both stable species (H ₂, CH ₄, CO, CO ₂, ...) and radicals (H, OH, CH,, C ₃H ₃, C ₃H ₅, C ₆H ₅) produced in the plasma. About twenty species have been identified. The influence of the relative concentration of these gaseous species on the deposition domain, the growth rate and the quality of diamond, especially the amount of sp ³ and sp ²hybridized carbons incorporated in the films is shown.