HIGH-TEMPERATURE KINETICS OF SI+N2O

In the present study the very fast high-temperature thermal decomposit ion of silane was used as a Si atom source to initiate its reactions w ith N2O. The experiments were performed behind reflected shock waves i n SiH4/N2O/Ar systems by applying Atomic Resonance Absorption Spectros copy (ARAS) for detecting Si and N atoms. Initial mixtures of 0.5-50 p pm SiH4 and 25-200 ppm N2O were used to perform experiments in the tem perature range 1780 K less than or equal to T less than or equal to T 3560 K at pressures 0.5 bar less than or equal to p less than or equal to 1.7 bar. From the Si atom concentration profiles the overall rate coefficient of the reaction Si + N2O = products (R3; k(3)), was determ ined by fitting calculated to measured profiles. From energetical reas ons reaction R3 can proceed via two exothermic product channels: Si N2O reversible arrow SiN + NO (R3a; k(3a)) and Si + N2O reversible arr ow SiO + N-2 (R3b; k(3b)) To separate both possible channels, N atoms were measured, which are to be expected from secondary reactions inclu ding the products of the channel (R3a). Again by computer fittings rat e coefficients for k(3a) were obtained, which can be summarized by the following Arrhenius expression: k(3a) = 5.0 X 10(14) exp(-8100 K/T) c m(3) mol(-1) s(-1) (+/- 50%). From the results of both, Si and N atom measurements, a mean value for the remaining rate coefficient k(3b) = 8.0 X 10(13) cm(3) mol(-1) s(-1) (+/- 50%) was obtained. Detailed comp uter simulations based on a proposed reaction mechanism revealed estim ates of further rate coefficients.