Absolute cross section for the formation of Si(S-1) atoms following electron impact dissociation of SiH4

A combination of electron scattering and laser-induced fluorescence (LIF) t echniques was used in the experimental determination of the absolute cross section for the formation of Si(S-1) ground-state atoms following the neutr al molecular dissociation of SiH4 by electron impact for energies from 20 e V to 100 eV. Electron impact on SiH4 produces-among other species-Si(S-1) g round-state atoms which are detected by pumping the Si(3p)(2) S-1 -->(3p)(4 s)P-1 transition at 390 nm with a tunable dye laser and recording the subse quent Si(3p)(4s)P-1 -->(3p)(2) D-1 fluorescence at 288 nm. We found a peak cross section for the formation of Si(S-1) atoms from SiH4 of 4.5x10(-17) c m(2) at an impact energy of 60 eV. When compared to the previously determin ed total SiH4 neutral dissociation cross section obtained from measurements in a constant-flow plasma reactor [Perrin , Chem. Phys. 73, 383 (1982)], w e find a branching ratio of about 0.037 for the formation of Si(S-1) atoms in the electron-impact induced neutral dissociation of SiH4. The absolute c alibration of our measured dissociation cross section was made relative to the cross section for the formation of N-2(+)(X) ground-state ions produced by electron impact on N-2 which was previously measured in the same appara tus using the same experimental technique. This cross section is known to w ithin +/- 10% and can serve as a benchmark for the calibration of neutral d issociation cross sections as discussed previously [Abramzon , J. Phys. B 3 2, L247 (1999)]. (C) 2000 American Institute of Physics. [S0021-9606(00)006 30-6].