Cross sections for radicals from electron impact on methane and fluoroalkanes

Molecular and atomic radicals from electron-impact dissociation of methane and a variety of fluoroalkanes are detected mass spectrometrically as organotellurides produced by the reaction of the radicals at the surface of a tellurium mirror. The radicals detected include CH(3) from CH(4); CF(3) from CF(4) and CHF(3); CHF(2) from CHF(3) and CH(2)F(2); CH(2)F from CH(3)F; and CF(3) and C(2)F(5) from C(2)F(6) and C(3)F(8) produced by electron impact at energies between 10 eV and 500 eV. Relative cross sections are measured. These are placed on an absolute scale by comparison with related measurements. For the collision energies relevant to processing plasmas, 10-30 eV, it is shown that dissociation into neutrals rather than dissociative ionization is mainly responsible for the production of molecular radicals. (C) 1998 American Institute of Physics..