MULTIPHOTON IONIZATION SPECTROSCOPY MEASUREMENTS OF SILICON ATOMS DURING VAPOR-PHASE SYNTHESIS OF CERAMIC PARTICLES

Resonance-enhanced multiphoton ionization spectroscopy has been applied to the problem of detection of gas-phase species in a dense particle-forming flow. Relative silicon atom profiles in an atmospheric pressure flame reactor producing silica particles have been made using a 2+1 ionization scheme. The results have shown that silicon atoms are confined to a very narrow time window in the reactor (<15 ms). In addition, the nonresonant background indicated the presence of ionizable clusters and could be a valuable tool for observing the presence and location of small clusters. The effect of varying silane loading changed both the location and magnitude of the silicon concentration observed. The results suggest that chain branching chemistry is important in the production of silicon and that enhancement of pyrolytic relative to oxidative processes occurs as the silane loading is increased. Finally, the role of charged particles on electron capture was investigated. It was found that significant attenuation of the electron current can lead to highly erroneous results.