Quantitative measurements of electron collision cross sections and their database related to plasma modeling

The electron excitation cross sections of fluorine containing molecules are very relevant to plasma-assisted fabrication of large scaled-integrated circuits, semiconductor manufacturing and other technological applications. However, despite their importance, few cross sections have been reported except for major molecules such as tetrafluoromethanes. In the present study, therefore, we measured the differential and integral cross sections (DCSs and ICSs) of difluoromethane, CH₂F₂.

The cross-section measurements were performed using a crossed-beam apparatus in the incident electron energies of 4.0 - 15 eV and over scattering angle range of 10^o - 130^o. Angular distributions of elastically and inelastically scattered electrons were normalized to the well-known absolute elastic DCS of helium by the relative flow technique. Elastic and inelastic ICSs were also obtained by extrapolating the DCSs measured over the angular range from 0^o to 180^o.

The ICSs for vibrational excitations to the fundamental modes and their combinations were extracted in addition to the elastic DCSs reported in the literature. The cross-section dataset of CH₂F₂ molecules has been updated by adding the present vibrational ICSs for each vibrational mode.