Study of atmospheric-pressure dielectric barrier discharges in Ar-TMS and Ar-HMDS mixtures

The use of dielectric barrier discharges (DBDs) as a source for plasma-enhanced chemical vapour deposition (PECVD) processes has increased significantly over the past two decades. An investigation of DBDs in argon with small additions of tetramethylsilane (TMS) or hexamethyldisilane (HMDS), carried out by fluid modelling and experimental diagnostics, is presented here. DBD plasma sources with plane-parallel and single-filament configurations driven by sinusoidal voltages at frequencies of 86 and 19 kHz are used in the study. The modelling is carried out using a spatially one-dimensional fluid-Poisson model with complex reaction kinetics involving precursor species. The analysis shows that Penning ionization (PI) of precursor molecules by excited argon atoms significantly impacts the discharge characteristics. It is found that electron production is dominantly determined by these processes, which consequently affect the ignition voltage of the gas. Furthermore, the analysis of the boundary fluxes reveals that the fluxes of cations generated in PI and subsequent ion-molecule processes are predominant, making them the main candidates responsible for film formation under the investigated conditions.