The Reaction of Hydrogen Atoms with Silyl Radicals; the Decomposition Pathways of Chemically Activated Silanes

Abstract

The reactions of hydrogen atoms with silane and the methylated silanes -with the exception of tetramethylsilane -have been investigated in a fast flow reactor. Under our experimental conditions hydrogen abstraction from the Si-H bond is followed by combination of hydrogen atoms with the corresponding silyl radicals. The molecules formed in this way are activated by about 375 kJ/mol of vibrational energy. Two decomposition channels have been unequivocally identified, namely the elimination of molecular hydrogen and of methane, both with concomittant formation of the respective silylenes. In a subsequent step, silylene inserts into the substrate under formation of disilanes. With increasing degree of methylation. stabilization of the activated molecule competes with decomposition and dominates the kinetics in the case of trimethylsilane. With methyl-and dimethyl-silane, methyl radicals are observed as an additional reaction product. On the basis of RRKM calculations it is unlikely that they originate from a direct decomposition of the activated molecules.Absolute values for the room temperature rate constants of the abstraction reactions are given; for H + CH 3 SiH 3 , Arrhenius parameters have been determined.

Mercury‐sensitized photochemical vapor deposition of amorphous silicon

“…A rate constant for the reaction of H radicals with silane, k,, of 2.6 E l 1 mol/cm'/s at 305 K with an activation energy of 10.4 kJ/mol has been adopted (Austin and Lampe, 1977). This is in good agreement with 2.65 E l l mol/cm3/s determined at room temperature (Worsdorfer et al, 1983).…”

Application of electronic structure and transition state theory: Reaction of hydrogen with silicon radicals

“…Experimental kinetic studies have been studied extensively for the reverse hydrogen extraction reaction in the gas phase 20–31. Only three have focused on the temperature dependence of the rate constant 20–22.…”

“… Arrhenius plots for the MP2/MP2/CCSD aug‐cc‐pVDZ method is shown for both the forward and reverse directions of the studied reaction. Experimental results are from references 20–31. The forward experimental results are obtained from balance with the reverse.…”

A high temperature study of the reaction SiH4+H ⇋ SiH3+H2

“…We have successfully included a mechanism which was recently proposed by [20] to describe the pyrolysis of C2H4 The rate coefficient of reaction (Rl) given in [20] was slightly increased by a factor of about 1. 6 to get the Literature values of k5 compared to the results of the present study concentration profiles of C2H51 decomposition experiments and also to match the initial slope of the H-atom profiles of the Slrb/C,H,VAr experiments. This adjustment seems to be justified due to the fact that compared to [20] our study was performed at pressures being a fac- Table 2.…”