147-NM PHOTOLYSIS OF MONOSILANE

The 147-nm photolysis of SiH4 results in the formation of H2, Si2H6, Si3H8, and a solid hydridic silicon film. Two primary processes are involved, namely, (a) SiH4 + hv → SiH2 + 2H and (b) SiH4 + hv → SiH3 + H, with ɸa = 0.83 and ɸb = 0.17. The quantum yields depend on the pressure of SiH4 but at 2 Torr are Ф(-SiH4) = 4.4 ± 0.6, Ф(Si2H6) = 1.29 ± 0.08, Ф(Si3H8) = 0.46 ± 0.01, and Ф(Siwall) = 0.5; the quantum yields for H2 formation were not measured. A mechanism is proposed, which incorporates the known reactions of SiH2 and SiH3 radicals, and is shown to be in accord with the experimental facts. © 1979, American Chemical Society. All rights reserved.