Molecular growth paths and dust-particles nucleation precursors in Ar/C2H2 low pressure discharges

A numerical model was used to investigate the effect of acetylene concentration in the feed gas on molecular growth and solid particle nucleation in argon-acetylene CCRF discharges. Results showed that for large acetylene conversion yields and small acetylene concentrations in the discharge, the ionization kinetic is driven by the Penning process and the molecular growth is governed by neutral polyynes. The cluster size distribution predicted shows that nucleation is unlikely in this situation. On the contrary, for limited conversion yields and significant acetylene concentrations in the discharge, the ionization kinetic is driven by the electron-impact process; the molecular growth is governed by positive ions and leads to significant concentrations of neutral polyynes and enhanced nucleation rate.

Automated summary

A numerical model was used to investigate the effect of acetylene concentration on molecular growth and solid particle nucleation in argon-acetylene CCRF discharges. The results showed that at low acetylene concentrations, the ionization kinetic is driven by the Penning process and the molecular growth is governed by neutral polyynes. On the other hand, at high acetylene concentrations, the ionization kinetic is driven by the electron-impact process, leading to increased concentration of neutral polyynes and enhanced nucleation rate.