PIC simulations of capacitively coupled oxygen rf discharges

Capacitively coupled discharges with a radio-frequency operated voltage (ccrf) are important for plasma assisted material processing. Experiments with electronegative oxygen ccrf discharges show a high-energy peak in the energy distribution of negative ions arriving at the anode, depending on the cathode material used. One possible explanation is ionization at or close to the surface of the cathode for the production of negative ions. By introducing an additional surface ionization model into a Particle-In-Cell (PIC) simulation with Monte Carlo Collisions (MCC) the experimental result is reproduced qualitatively. Comparison of one dimensional and two dimensional simulation results allows an improved understanding of the microscopic processes determining the dynamics of negative ions.