Particle-based modeling of oxygen discharges

We present an one-dimensional particle-in-cell Monte-Carlo model for capacitively coupled radio-frequency discharges in oxygen. The model quantitatively describes the central part of the discharge. For a given voltage and pressure, it self-consistently determines the electric potential and the distribution functions for electrons, negatively charged atomic oxygen, and positively charged molecular oxygen. Previously used collision cross sections are critically assessed and in some cases modified. Provided associative detachment due to metastable oxygen molecules is included in the model, the electro-negativities in the center of the discharge are in excellent agreement with experiments. Due to lack of empirical data for the cross section of this process, we propose a simple model and discuss its limitations.