HIGH-TEMPERATURE KINETICS OF SI+N2O

In the present study the very fast high-temperature thermal decomposition of silane was used as a Si atom source to initiate its reactions with N2O. The experiments were performed behind reflected shock waves in SiH4/N2O/Ar systems by applying Atomic Resonance Absorption Spectroscopy (ARAS) for detecting Si and N atoms. Initial mixtures of 0.5-50 ppm SiH4 and 25-200 ppm N2O were used to perform experiments in the temperature 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 determined by fitting calculated to measured profiles. From energetical reasons reaction R3 can proceed via two exothermic product channels: Si + N2O reversible arrow SiN + NO (R3a; k(3a)) and Si + N2O reversible arrow SiO + N-2 (R3b; k(3b)) To separate both possible channels, N atoms were measured, which are to be expected from secondary reactions including the products of the channel (R3a). Again by computer fittings rate 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) cm(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 computer simulations based on a proposed reaction mechanism revealed estimates of further rate coefficients.