Thermal electron attachment to halogenated silanes in the gas phase

Rationale

Silane derivatives play a crucial role in industrial plasma processes for the fabrication of various electronic devices such as lighting devices, solar cells, and displays. Accurate quantitative data are essential for modeling technological plasmas. This study reports the rate coefficients (k) and activation energies (E_a) for thermal electron attachment to Si₂Cl₆, Si (CH₃)₃CHF₂, and SiCl (CH₃)₂Si(CH₃)₃, which are key parameters for understanding the underlying processes in plasmas. The results obtained for other silane derivatives were also analyzed and discussed.

Methods

The measurements were conducted using the pulsed Townsend technique. In this technique, electrons generated by a laser under an electric field travel to the anode, inducing a charge on it. In the presence of a scavenger gas, electrons are captured, leading to a decrease in the rate of charge increase over time. The kinetic parameters were deduced from the shape of the pulse. The G4 method was used to obtain bond dissociation energies (BDEs).

Results

This study determined the kinetic parameters for thermal electron attachment to Si₂Cl₆, Si (CH₃)₃CHF₂, and SiCl (CH₃)₂Si(CH₃)₃ for the first time. The rate coefficients at 298 K were found to be 2.17 ± 0.04 × 10⁻⁹cm³s⁻¹, 2.01 ± 0.09 × 10⁻¹²cm³s⁻¹, and 8.05 ± 0.07 × 10⁻¹²cm³s⁻¹, respectively. The corresponding activation energies were determined to be 0.37 ± 0.04 eV, 0.29 ± 0.03 eV, and 0.21 ± 0.01 eV for Si₂Cl₆, Si (CH₃)₃CHF₂, and SiCl (CH₃)₂Si(CH₃)₃, respectively. The experiment was conducted over the temperature range of 298–378 K.

Conclusions

The findings of this study provide significant new insights into fundamental parameters such as rate coefficients and activation energies for thermal electron capture by chlorinated and fluorinated silane derivatives. These data contribute to advancing our understanding of thermal electron interactions with chlorosilanes, which can be utilized for controlling important species in the plasmas of various modern technologies.