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

Abstract

A combination of electron scattering and laser-induced fluorescence (LIF) techniques was used in the experimental determination of the absolute cross section for the formation of Si(1S) ground-state atoms following the neutral molecular dissociation of SiH4 by electron impact for energies from 20 eV to 100 eV. Electron impact on SiH4 produces—among other species—Si(1S) ground-state atoms which are detected by pumping the Si(3p)2 1S→(3p)(4s)1P transition at 390 nm with a tunable dye laser and recording the subsequent Si(3p)(4s)1P→(3p)2 1D fluorescence at 288 nm. We found a peak cross section for the formation of Si(1S) atoms from SiH4 of 4.5×10−17 cm2 at an impact energy of 60 eV. When compared to the previously determined total SiH4 neutral dissociation cross section obtained from measurements in a constant-flow plasma reactor [Perrin et al., Chem. Phys. 73, 383 (1982)], we find a branching ratio of about 0.037 for the formation of Si(1S) atoms in the electron-impact induced neutral dissociation of SiH4. The absolute calibration of our measured dissociation cross section was made relative to the cross section for the formation of N2+(X) ground-state ions produced by electron impact on N2 which was previously measured in the same apparatus using the same experimental technique. This cross section is known to within ±10% and can serve as a benchmark for the calibration of neutral dissociation cross sections as discussed previously [Abramzon et al., J. Phys. B 32, L247 (1999)]. © 2000 American Institute of Physics.