Electron-impact ionization of silicon tetrachloride (SiCl4)

Abstract

We measured absolute partial cross sections for the formation of various singly charged and doubly charged positive ions produced by electron impact on silicon tetrachloride (SiCl4) using two different experimental techniques, a time-of-flight mass spectrometer (TOF-MS) and a fast-neutral-beam apparatus. The energy range covered was from the threshold to 900 eV in the TOF-MS and to 200 eV in the fast-neutral-beam apparatus. The results obtained by the two different experimental techniques were found to agree very well (better than their combined margins of error). The SiCl3(+) fragment ion has the largest partial ionization cross section with a maximum value of slightly above 6x10(-20) m2 at about 100 eV. The cross sections for the formation of SiCl4(+), SiCl+, and Cl+ have maximum values around 4x10(-20) m2. Some of the cross-section curves exhibit an unusual energy dependence with a pronounced low-energy maximum at an energy around 30 eV followed by a broad second maximum at around 100 eV. This is similar to what has been observed by us earlier for another Cl-containing molecule, TiCl4 [R. Basner, M. Schmidt, V. Tamovsky, H. Deutsch, and K. Becker, Thin Solid Films 374 291 (2000)]. The maximum cross-section values for the formation of the doubly charged ions, with the exception of SiCl3(++), are 0.05x10(-20) m2 or less. The experimentally determined total single ionization cross section of SiCl4 is compared with the results of semiempirical calculations.

Electron-impact ionization of SiCl, SiCl₂ and SiCl₄ molecules

“…For SiCl 4 [ Fig. 3] the ionization cross sections are considerably lower than the experimental results of Basner et al [12] up to 200 eV. Their results for SiCl 4 [ Fig.…”

“…1] the ionization cross sections calculated by Kothari et al [16] using [16]; triangles -data by DM formalism [10] ; squares -data by Mahoney et al [10]. Kothari et al [16] King et al [14] Basner et al [12] BEB BEB/3 [16]; triangles -data by DM formalism [12 ]; squares -data by Basner et al [12]; crosshair -data by King et al [14].…”

“…From experimental side a few results are available [10][11][12][13][14] for these molecules. Comparisons are made of present results with experimental results and the theoretical results of DM formalism [10,12] and the CSP-ic model of Kothari et al [16].…”

“…The energy range covered in the TOF-MS was from the ionization threshold to 900 eV and up to 200 eV in fast-neutralbeam apparatus. Basner et al [12] have measured electron impact ionization of SiCl 4 using two different experimental techniques namely, a time-of-flight mass spectrometer (TOF-MS) and a fast-neutral-beam techniques. The energy range covered in the TOF-MS was from the ionization threshold to 900 eV and up to 200 eV in fast-neutral-beam apparatus.…”

“…From theoretical side, the authors [10][11][12] have calculated the total ionization cross sections using DM formalism. Deutsch et al [15] have calculated the ionization cross sections of SiCl x (x=1-4) using a modified additivity rule (MAR) in the energy range from 30 to 200 eV.…”