Surface effects in a capacitive argon discharge in the intermediate pressure regime

One-dimensional particle-in-cell/Monte Carlo collisional simulations are performed on a capacitive argon discharge in the intermediate pressure regime (1.6 Torr). The excited argon states (metastable levels, resonance levels, and the 4p manifold) are modeled self-consistently with the particle dynamics as spaceand time-varying fluids. Most of the ionization occurs near the plasma-sheath interfaces, with little ionization within the plasma bulk region. When the excited states, and secondary electron emission due to neutral and ion impact on the electrodes are included in the discharge model, the discharge operation transitions from α-mode to γ-mode, in which nearly all the ionization is due to secondary electrons. Secondary electron production due to the bombardment of excited argon atoms is roughly 14.7 times greater than that due to ion bombardment. Electron impact of ground state argon atoms by secondary electrons contributes about 76% of the total ionization; primary electrons, about 11%; metastable Penning ionization, about 13%; and multi-step ionization, about 0.3%. Furthermore, the simulation results are compared to experimental findings at low pressure (100 mTorr) and intermediate pressure (1 Torr).