We report measurements of absolute cross sections for the electron-impact ionization and dissociative ionization of the SiDx (x=1-3) free radicals from threshold to 200 eV using the fast-neutral-beam technique. The deuterated rather than the protonated target species were used in order to allow a better separation of the various product ions from a given parent in our apparatus. A common feature of all three radicals studied in this work is a dominant parent ionization cross section with essentially the same absolute value of roughly 3.7×10-16 cm2 at 70 eV. Dissociative ionization processes for all three targets are less significant with a single dissociative process dominating in each case, viz. the removal of a single D atom (SiDx+e-→SiDx-1+D+2e -). The cross section for this dominant dissociative ionization channel also had the same maximum value of about 1.2×10-16 cm2 for all three targets. A comparison of the experimentally determined total single ionization cross sections with calculated cross sections using a modified additivity rule showed good to satisfactory agreement for all three targets in terms of the absolute values, but reveals some discrepancies in the cross section shapes.
ASJC Scopus subject areas
- Physics and Astronomy(all)
- Physical and Theoretical Chemistry