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

Abstract

The reaction of SiH4 with nitrogen is studied in apost-discharge device by means of a mass spectrometer. The atomic nitrogenis produced in a dc discharge and the silane is injected downstream andreacts mostly with the atomic nitrogen. Induced effects due to thevibrational excitation of the molecules (change in the ionization crosssection when molecules are ionized in the ionization chamber of the massspectrometer) are minimized by adding a buffer gas (N2) that isinjected 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 accordingto SiH4 + N⟶k1SiH2 + NH2.Then the two radicals SiH2 and NH2 produced react alsowith the atomic nitrogen via the reactions SiH2 + N⟶k2products and NH2 + N⟶k2products. These two radicals react alsotogether via SiH2 + NH2⟶k4products.The absolute concentrations of the main species considered in the reactionmechanism are measured using different methods and absolute concentrationsof the species are compared with results given by a kinetic model. ARunge-Kutta-Merson algorithm is used in order to resolve the set ofordinary differential equations. The experimental results are well fittedwith a relative accuracy of 20%, using the reaction rate constants k1,k2, k3 and k4 in the ranges (1.2-1.7)×10-16 m3 s-1, (9.0-13.7)×10-16 m3 s-1, (5.8-8.8)×10-16 m3 s-1 and(4.2-6.2)×10-16 m3 s-1, respectively.