Analysis of the formation of stable species in atmospheric pressure DBDs in Ar-TMS mixtures

Experimental and modelling studies of the formation of stable molecules in dielectric barrier discharges (DBDs) at atmospheric pressure are presented. The reactor consists of two coaxial borosilicate glass tubes with 2-mm thick walls and outer radii of 12 and 15 mm, respectively, leaving a gap of 1 mm. Discharges in argon with small admixtures (up to 100 ppm) of tetramethylsilane (TMS), powered by a sinusoidal voltage (4 kV amplitude, 86.2 kHz), are analysed. Fourier-transform infrared spectroscopy is applied to measure the number densities of various stable molecules in the effluent for different residence times. The measurements are compared with results obtained by time-dependent, spatially one-dimensional fluid-Poisson modelling including an Ar-TMS plasma chemistry with about 90 species and 700 reactions. The measured and calculated number densities generally agree satisfactorily for several stable molecules confirming the performance of the model. In particular, trimethylsilane is the primary organosilicon species generated, methane becomes the predominant stable hydrocarbon component, and large amounts of hydrogen molecules are predicted by numerical modelling.