Infrared Multiphoton Decomposition of Monosilane

Article abstract of DOI:10.1021/ja00413a005

The decomposition of SiH4 by infrared radiation from a pulsed CO2 TEA laser at 944.19 cm^-1 has been studied in the pressure range of 10-22 torr and at a fluence of 1.0 J/cm².The products observed are H2, Si2H6, Si3H8, Si4H10, Si5H12, and a solid (SiHx)n.The energy absorption from the laser beam increases with increasing pressure of SiH4 and/or of He, showing that collisions are necessary to pump molecules into the quasicontinuum from which resonant absorption of the laser photon occurs readily.The addition of He also increases the decomposition rate showing that the decomposition is a multiphoton decomposition and not a purely thermal reaction.The primary dissociation of SiH4 is to H2 and SiH2 and it is the further reactions initiated by attack of SiH2 on SiH4 that cause the observed decomposition.It is shown that the results are accounted for by a Boltzmann distribution of infrared photons in SiH4 and a reaction mechanism identical with that shown to obtain in the pyrolysis of SiH4.