Investigations of CH4, C2H2 and C2H4 dusty RF plasmas by means of FTIR absorption spectroscopy and mass spectrometry

Infrared (IR) absorption spectroscopy and mass spectrometry have been simul taneously applied to dusty radiofrequency (RF) plasmas in methane, acetylen e and ethylene. The combination of IR absorption spectroscopy and mass spec trometry allows the chemical composition and structure of the most relevant plasma-produced neutral species, the ionic plasma composition and the chem ical composition of the nanometer-sized particles to be precisely identifie d. The production of acetylenic compounds (C2Hx) seems to be a key mechanis m for the powder formation in all the investigated hydrocarbon plasmas. Ele ctron attachment to acetylenic compounds and the following ion-neutral reac tions might lead to the high-mass carbon anions, which are trapped in the p lasma and finally end in powder formation. The hydrogenation of the monomer strongly influences the composition of the ions. Finally the composition o f the plasma-produced particles is mainly sp(3) bonded carbon and the infra red spectra show similarities to that of polyethylene.