Measurement of rate constants between atomic nitrogen and silane in a nitrogen discharge afterglow

The reaction of SiH 4 with nitrogen is studied in a post-discharge device by means of a mass spectrometer. The atomic nitrogen is produced in a dc discharge and the silane is injected downstream and reacts mostly with the atomic nitrogen. Induced effects due to the vibrational excitation of the molecules (change in the ionization cross section when molecules are ionized in the ionization chamber of the mass spectrometer) are minimized by adding a buffer gas (N 2 ) that is injected downstream with the silane. The reaction scheme of the silane injected in the nitrogen post-discharge, proceed via the dissociation of the silane with atomic nitrogen according to SiH 4 + N⟶ k 1 SiH 2 + NH 2 . Then the two radicals SiH 2 and NH 2 produced react also with the atomic nitrogen via the reactions SiH 2 + N⟶ k 2 products and NH 2 + N⟶ k 2 products. These two radicals react also together via SiH 2 + NH 2 ⟶ k 4 products. The absolute concentrations of the main species considered in the reaction mechanism are measured using different methods and absolute concentrations of the species are compared with results given by a kinetic model. A Runge-Kutta-Merson algorithm is used in order to resolve the set of ordinary differential equations. The experimental results are well fitted with a relative accuracy of 20%, using the reaction rate constants k 1 , k 2 , k 3 and k 4 in the ranges (1.2-1.7)×10 -16 m 3 s -1 , (9.0-13.7)×10 -16 m 3 s -1 , (5.8-8.8)×10 -16 m 3 s -1 and (4.2-6.2)×10 -16 m 3 s -1 , respectively.