Low Energy Electron Attachment by Some Chlorosilanes

Area of Science:

• Physical Chemistry
• Chemical Physics
• Materials Science

Background:

• Understanding the gas-phase reaction kinetics of chlorosilanes is crucial for various industrial applications, including semiconductor manufacturing.
• Previous studies have explored the properties of chlorosilanes, but detailed kinetic data, especially concerning negative ion formation, remains an active area of research.

Purpose of the Study:

• To experimentally determine the rate coefficients (k) and activation energies (E) for SiCl4, SiHCl3, and Si(CH3)2(CH2Cl)Cl in the gas phase.
• To investigate the relationship between these kinetic parameters and the electronic properties, such as electron affinity, of these chlorosilane molecules.
• To explore the geometric changes associated with negative ion formation using computational methods.

Main Methods:

• Pulsed Townsend technique for gas-phase kinetic measurements at temperatures ranging from 298-378 K.
• Arrhenius equation fitting to determine activation energies from temperature-dependent rate coefficients.
• Density Functional Theory (DFT) calculations at the B3LYP/6-31G(d) level to study negative ion formation and geometry changes.

Main Results:

• Rate coefficients (k) and activation energies (E) were determined for SiCl4, SiHCl3, and Si(CH3)2(CH2Cl)Cl.
• A linear correlation was established between the rate coefficients and activation energies of chlorosilanes.
• Calculations revealed relationships between geometric changes during negative ion formation, polarizability of the attaching center, and adiabatic electron affinities (AEA).

Conclusions:

• The study provides fundamental kinetic data for key chlorosilane molecules.
• The findings highlight a predictable relationship between kinetic parameters and electronic properties in chlorosilanes.
• Computational analysis offers insights into the mechanism of negative ion formation and its dependence on molecular characteristics.