2D PIC simulations of realistic plasma-surface interactions in geometrically asymmetric capacitive radio frequency discharges*

The effects of realistic surface coefficients on the charged particle dynamics in geometrically asymmetric capacitively coupled argon discharges operated at low pressure and high voltage are studied by 2D Particle-In-Cell/Monte Carlo collision simulations. By including plasma and SiO$_2$ surface interaction processes, the energy dependent ion ($\gamma$-electron) and electron induced ($\delta$-electron) secondary electron emission are found to influence the electron dynamics a lot. Due to the high energy ion bombardment at the electrodes, a high number of $\gamma$-electrons is emitted. These $\gamma$-electrons are found not to contribute much to the ionization directly, as they are too energetic after being accelerated by the sheath electric field, but they can significantly enhance the $\delta$-electron emission from boundary surfaces, especially in asymmetric discharges, where they constitute the main channel for the $\delta$-electron emission. After the $\delta$-electrons are emitted, they cause nearly 40\,\% of the total ionization. By switching on and off the surface coefficients, large changes of the electron dynamics and a reduced plasma density is found, which indicates that both the $\gamma$- and $\delta$-electrons play important roles in the discharge.\\ \\In collaboration with: Julian Schulze, Ruhr-University Bochum;Peter Hartmann, Wigner Research Centre for Physics; Zoltan Donk\'o, Wigner Research Centre for Physics; Yuan-Hong Song, Dalian University of Technology