Plasma species and reaction dynamic-oriented global model studies for microscale argon discharges*

Low temperature microplasma discharges have emerging applications in biomedicine, satellite propulsion, electric device and more[Garner et al, J. Appl. Phys 128, 210903 (2020) and Fu et al Plasma Res. Express 2, 013001 (2020)]. In this work, a global model is employed to explore the importance of plasma species (e, Ar⁺, Ar₂⁺, Ar^m, Ar^r, Ar^4p, Ar₂^*) and reaction dynamics for RF current source-driven argon discharges in a sub-millimeter gap. The model shows that Ar₂⁺ starts to be the main ion species above 100 Torr, and Ar₂* is the main metastable neutrals for pressure higher than 200 Torr. The wall loss process of Ar₂⁺ is less important compared to the recommendation reaction with electrons in the bulk. For fixed driving current and gap at atmosphere, the plasma density (mainly e and Ar₂⁺) increases first and then gets relatively flat with increasing driving frequency (0.1-2GHz), meanwhile, the main loss channel of Ar₂⁺ transits from wall loss to bulk recombination. We also intend to explore the similarity law of different plasma species densities, and their generation and loss process for various pressures, gap distances, and driving frequencies.