Mass spectrometric investigation of the roles of several chemical intermediates in diamond synthesis

Abstract

Mass spectrometric studies were performed to investigate several key chemical intermediates and identify their roles in diamond synthesis in a C₂H₄/C₂H₂/O₂ combustion-flame chemical vapour deposition process. The diamond deposition rate and diamond quality were correlated with the growth parameters, the distance from the substrate to the torch nozzle and the oxygen–fuel ratio. The dependences of the intermediate concentrations as functions of the distance to the torch nozzle and oxygen–fuel ratio were established. It was suggested that an appropriate balance between high hydrocarbon intermediates (C₂H₂⁺, C₃H₃⁺, C₃H₄⁺, C₄H₂⁺, C₄H₃⁺) and carbon etchants (O⁻, OH⁻, and H₃O⁺) was required to achieve effective diamond deposition. Influence of the resonant vibrational excitation of ethylene molecules on diamond deposition was investigated. The resonant vibrational excitation stimulated the formation of high hydrocarbon intermediates while suppressing the yield of carbon etchants, which suggested the possibility of modifying the combustion process in a way that favours diamond synthesis through resonant vibrational excitation.