Infrared Laser Photochemistry of SiH4-CH3Cl Mixtures

Article abstract of DOI:10.1021/j100373a039

By use of a pulsed CO2 TEA laser at 944.19 cm^-1 and fluences in the range of 0.49-0.71 J/cm², the infrared photochemistry of SiH4-CH3Cl mixtures has been studied in a pressure range of 50-100 Torr and over a temperature range of 295-428 K.The gaseous products observed are H2, CH4, Si2H6, and SiH3Cl, with trace amounts of Si3H8 and perhaps CH3SiH2Cl.As is usual in silane decomposition, a brown solid product containing silicon, hydrogen, and under some conditions, chlorine was also produced.The photochemical conversion is best described by initial decomposition of SiH4 to SiH2 and H2 followed by competition of SiH4 and CH3Cl for SiH2 molecules.The production of CH4 is believed to occur via the decomposition of highly energized CH3SiH2Cl* (formed by SiH2 insertion into the C-Cl bond of CHCl3), yielding CH4 and SiHCl as products.SiH3Cl is then formed by the secondary reaction of SiHCl with SiH4.Studies of the temperature dependece of the rates of competing reactions suggest that the activation energy for insertion of SiH2 into the C-Cl bond of CH3Cl is, within experimental error, equal to that for SiH2 insertion into the Si-H bond of SiH4.