Laser-induced fluorescence detection and kinetics of SiH2radicals in Ar/H2/SiH4RF discharges

Laser-induced fluorescence spectroscopy is used to measure spatially- and time-resolved SiH 2 radical densities in pure SiH 4 , H 2 /SiH 4 and Ar/SiH 4 radio-frequency glow discharges used for amorphous silicon thin film deposition. Absolute density calibration is obtained by a Rayleigh scattering experiment in pure nitrogen. Typical SiH 2 densities on the plasma axis are 1-10 × 10 16 m -3 . Measurements of the SiH 2 decay in the afterglow of argon/silane discharges are used to determine for the first time the SiH 2 loss probability on a-Si:H surfaces and to confirm the reaction rate coefficient of SiH 2 with SiH 4 . We find = 0.6±0.15 and k r = (2.3±0.5) × 10 -17 m 3 s -1 molecule -1 at T = 500 K and p = 9 Pa. The measured SiH 2 densities are compared to those calculated by a previously published two-dimensional plasma simulation code.