Silane ionization cross section

In RF discharges of silane, SiH usually is the most abundant ion, but others (SiH, and Si H+ with 1 < n < 9) also are present [319]. The relative abundance of SiH ions increases with increasing pressure, while that of SiH decreases [319]. The ionization cross section of SiHt is higher than that of SiHj [320], but SiH is lost via the reaction SiH -1- SiH4 —> SiHj -F SiH3 [305], At pressures lower than 0.1 Torr SiHt becomes the dominant ion. 

Chatham, H. Hils, D. Robertson, R. Gallagher, A. Total and Partial Electron Collisional Ionization Cross Sections for Methane, Ethane, Silane, and Di silane. J. Chem. Phys. 1984, 81, 1770-1777. 

This article describes recent advances in the experimental determination of electron impact ionization cross sections for silane (SiH4) its radicals, SiH. (x = 1 to 3) and the Si-organic molecules tetramethylsilane (TMS), Si(CH3)4 tetraethoxysilane (TEOS), Si(0-CH2-CH3)4 and hexamethyldisiloxane (HMDSO), (CH3)3-Si-0-Si-(CH3)3, which is one of the simplest siloxane compounds. These are model substances, and the results obtained for these species may be used in efforts to predict the ionization properties of other, more complex Si-organic molecules. The ionization cross sections of the stable compounds were measured using a high-resolution double-focusing mass spectrometer. The cross-section data for the radicals were obtained in a fast-neutral-beam apparatus. 

A detailed description of the fast-beam apparatus and of the experimental procedure employed in the determination of absolute partial ionization cross sections has been given in previous publications (Wetzel et al, 1987 Freund et al., 1990 Tamovsky and Becker, 1992 Tamovsky and Becker, 1993). For the measurements of the cross sections of silane radicals, a dc discharge biased at typically 2 to 3 kV through SiD4 served as the primary ion source. Deuterated rather than protonated target species were used in these studies to facilitate a... 

Measured Appearance Energies and Partial Ionization Cross Sections at 70 eV Impact Energy for the Various Fragment Ions Produced by Dissociative Ionization OF Silane... 

The rate coefficient for electron impact ionization depends very sensitively on the ionization energy, as is demonstrated in Fig. 8. We calculated the ratio of the rate coefficients for total ionization of silane for different electron temperatures using the total ionization cross sections of Chatham et al. (1984) and Krishnakumar and Srivastava (1995). The primary difference between the two cross-section data sets at low energies is a 0.6-eV difference in the measured ionization energy [with Chatham et al. (1984) reporting the lower value]. As expected, the... 

Fig. 8. Ratio of the rate coefficient for total ionization of silane for different electron temperatures using the total ionization cross sections of Krishnakumar and Srivastava (1995) (labeled Krishna 1 nd Chatham el al. (1984) (labeled Chatham)-...

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