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