Mass analysis has been conducted on the positive ions and neutral species in the downstream region of Ar/CF4/O2 plasmas. The neutral species have been ionized by Li+ attachment before mass analysis. The CF2O+, C2F5O+ and CnF2n-1O+ (1 ≤n≤ 6) positive ions and the CnF2nO (1 ≤n≤ 7) neutral species have been found as the species composed of C, F and O. The intensity of C2F 4O observed via the Li+-attachment mass spectra has been exceptionally weak in comparison to the intensities of CF2O and C3F6O. In addition, neither C2F4 nor C3F6 have been observed, although CnF 2n (n≥ 4) have been observed as the species composed only of C and F. These findings suggest that CnF2nO (n≥ 3) are produced mainly through the following reactions: CF3(CF 2)mCF = CF2 + O(3P) → CF 2(3B1) + CF3(CF2) mCFO (m≥ 1) and CF3(CF2)mCF = CF(CF2)nCF3 + O(3P) → CF 3(CF2)mCF + CF3(CF2) nCFO (m, n≥ 1), where the CF3(CF2) n- group might have side chains, as in (CF3) 2CF(CF2)n-2-. With the help of quantum chemistry calculations of reaction enthalpies and transition states, the formation mechanisms of the observed species have been discussed in detail.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)
- Physical and Theoretical Chemistry