Observation of Si2 in a chemical vapor deposition reactor by laser excited fluorescence

For the first time an intermediate chemical species, Si2, has been observed in the gas phase during the chemical vapor deposition of silicon from silane. This observation is inconsistent with previous theoretical models for silicon deposition, which assume that either thermodynamic equilibrium or surface kinetics determines the silicon deposition rate. It is consistent with the predictions of a new model for chemical vapor deposition by Coltrin et al., in which gas phase chemical kinetics play an important role in the deposition mechanism. The Si2 molecule could be a precursor to the nucleation of silicon particulates in the gas phase.