Electron induced ionization of plasma processing gases: C₄F_x (x  =  1–8) and the isomers of C₄F₆ and C₄F₈

The total ionization cross section (Q _ion) for C₄F_x (x  =  1–8) fluorocarbons and the isomers of C₄F₆ and C₄F₈ molecules are calculated from ionization threshold to 5 keV using the binary-encounter bethe method. The targets are fully optimized using the Hartree–Fock (HF) method and density function theory (DFT) for their minimum energy structure and orbital parameters. The present Q _ion with HF parameters showed good agreement with the experimental data for 1,3-C₄F₆, 2-C₄F₆, 2-C₄F₈ and 1-C₄F₈. On the other hand, the Q _ion with DFT parameters are in good accordance with the recent theoretical results for 1,3-C₄F₆ and 2-C₄F₆. The Q _ion for c-C₄F₈ showed much variation among the various results. The isomer effect in Q _ion is negligible for the isomers of C₄F₆ and C₄F₈ molecules. The calculation of Q _ion for C₄F, C₄F₂, C₄F₃, C₄F₄, C₄F₅, c-C₄F₆, C₄F₇ and iso-C₄F₈ is a maiden attempt. The present cross section data are important quantities for low temperature plasma modeling especially related to the fluorocarbon plasmas. (paper)