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

Abstract

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 14eV. 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±0.1eV, 4.5±0.1eV and 5.6±0.1eV, respectively. For SiF4 the AEs for F−, SiF3− and F2−, through the dominating resonance are found to be 10.2±0.1eV, 10.2±0.1eV and 10.3±0.1eV, respectively. From GeF4 the molecular ion GeF4− and the fragments GeF3−, GeF2−, GeF− and F− are all observed with appreciable intensities, and the F− production is found to be significantly close to 0eV 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.