Fourier transform infrared spectroscopy of effluents from pulsed plasmas of 1,1,2,2-tetrafluoroethane, hexafluoropropylene oxide, and difluoromethane

Gas-phase Fourier transform infrared spectroscopy (FTIR) has been used to analyze the effluents from C2H2F4, hexafluoropropylene oxide (CF3CFOCF2, HFPO), and CH2F2 pulsed plasmas. A series of reference spectra for possible effluent species was used to identify the major species in each. The major species in pulsed C2H2F4 plasmas were found to be: C2H2F4, HF, C2F4, C2HF5, CHF3, and SiF4 (formed from free fluorine). For HFPO pulsed plasmas, the major effluents are: HFPO, CF3COF3, COF2, C2F4, C2F6, CO, CF4, and C3F8, whereas for CH2F2 pulsed plasmas, the major effluents are: CH2F2, HF, SiF4, and CHF3. Reaction sets were postulated for each precursor to account for the observed effluents, and these sets were used to explain the trends of species concentrations with pulse on and pulse off time. In each case, most of the effluent concentration trends could be traced back to competition between dissociation pathways of a particular molecule. For both C2H2F4 and CH2F2, the main reactions were the competition betw...