On the Role of Metastable States in Low Pressure Oxygen Discharges

摘要

We use the one-dimensional object-oriented particle-in-cell Monte Carlocollision code {\tt oopd1} to explore the spatio-temporal evolution of theelectron heating mechanism in a capacitively coupled oxygen discharge in thepressure range 10 -- 200 mTorr. The electron heating is most significant in thesheath vicinity during the sheath expansion phase. We explore how including andexcluding detachment by the singlet metastable states O$_2$(a$^1 \Delta_{\rmg}$) and O$_2$(b$^1\Sigma_{\rm g}^+$) influences the heating mechanism, theeffective electron temperature and electronegativity, in the oxygen discharge.We demonstrate that the detachment processes have a significant influence onthe discharge properties, in particular for the higher pressures. At 10 mTorrthe time averaged electron heating shows mainly ohmic heating in the plasmabulk (the electronegative core) and at higher pressures there is no ohmicheating in the plasma bulk, that is electron heating in the sheath regionsdominates.