Direct kinetic studies of SiH3+SiH3, H, CCl4, SiD4, Si2H6, and C3H6 by tunable infrared diode laser spectroscopy

Abstract

Gas phase reactions of silyl radical, SiH3, are investigated at room temperature using tunable diode laser flash kinetic spectroscopy. Photolytic generation of silyl at 193 and 248 nm is demonstrated using several different precursor systems. The silyl recombination reaction, SiH3+SiH3→Si2H6, is studied by quantitative measurement of SiH3 and attendant product densities. Analysis yields a refinement of the rate constant, krc=(7.9±2.9)×10−11 cm3 molecule−1 s−1. By modeling silyl densities following photolysis of HCl in SiH4, bimolecular rate constants for H+SiH3 and H+SiH4 are determined to be (2±1)×10−11 and (2.5±0.5)×10−13 cm3 molecule−1 s−1, respectively. Reactions of SiH3 with SiD4, Si2H6, CCl4, and C3H6 (propylene) are studied under pseudo-first-order conditions. Derived upper limits to the rate constants show these reactions to be slow at room temperature. The data demonstrate the reactivity of silyl with open-shell (radical) species and the general inertness of silyl toward closed shell molecules. Under typical chemical vapor deposition conditions, SiH3 is, therefore, a kinetically long-lived species in the gas phase and consequently a potentially important film forming species under plasma and photochemical deposition conditions.