Plasma chemistry and growth of nanosized particles in a C₂H₂ RF discharge

A model describing the chemical clustering kinetics in a low-pressure acetylene RF discharge has been developed. The model contains neutral chain and cyclic hydrocarbons, positive and negative ions, and electrons. The gas-phase chemistry includes neutral-neutral reactions, electron induced H-abstraction, electron attachment, and ion-ion neutralization. In addition, diffusion losses to the reactor walls are considered. The model predicts the time evolution of species concentrations and chemical reaction rates, and reveals the preferred clustering pathways. The clustering occurs mainly through addition of growth species and formation of linear molecules. However, the amount of aromatic hydrocarbons produced is not negligible even at room temperature and increases strongly with the gas temperature. The FTIR and NMR measurements performed indicate the presence of aromatic compounds in the particles produced.