Negative ion formation through dissociative electron attachment to the group IV tetrafluorides: Carbon tetrafluoride, silicon tetrafluoride and germanium tetrafluoride

Dissociative electron attachment (DEA) to the group IV tetrafluorides: CF₄, SiF₄ and GeF₄, is reported in the incident electron energy range from about 0 to 14 eV. The F₂ ^- formation from CF₄ is established and the appearance energies (AEs) for F^-, CF₃ ^- and F₂ ^- are determined using a three-point calibration for the energy scale. These are found to be 4.7 ± 0.1 eV, 4.5 ± 0.1 eV and 5.6 ± 0.1 eV, respectively. For SiF₄ the AEs for F^-, SiF ₃ ^- and F₂ ^-, through the dominating resonance are found to be 10.2 ± 0.1 eV, 10.2 ± 0.1 eV and 10.3 ± 0.1 eV, respectively. From GeF₄ the molecular ion GeF ₄ ^- and the fragments GeF₃ ^-, GeF ₂ ^-, GeF^- and F^- are all observed with appreciable intensities, and the F^- production is found to be significantly close to 0 eV incident electron energy. The present findings are compared with earlier experiments and discussed in context to the thermochemistry of the respective processes as well as the nature of the underlying resonances.