Electron-induced secondary electrons in low-pressure capacitively coupled radio-frequency plasmas

We investigate the effects of secondary electrons (SEs) induced by electrons on the discharge characteristics in low-pressure single-frequency capacitively coupled plasmas (CCPs) by Particle-in-Cell/Monte Carlo Collisions simulations. Such SEs ($\delta$-electrons) were found to have a remarkable influence on the plasma parameters in argon at 0.5 Pa and 6.7 cm gap between SiO$_2$ electrodes (B. Horv\'ath et al. 2017 \textit{Plasma Sources Sci. Technol.} \textbf{26} 124001). Here we study the impact of $\delta$-electrons on the ionization dynamics and plasma parameters at various pressures and voltage amplitudes, assuming different SE yields for ions ($\gamma$-coefficient). The voltage amplitude, the gas pressure and the value of the $\gamma$-coefficient affect the role of $\delta$-electrons in the ionization dynamics. While their effect is most striking at low pressures, high voltage amplitudes and high $\gamma$-coefficients, in the whole parameter regime investigated here the realistic description of the electron-surface interaction changes significantly the computed plasma parameters compared to results based on a widely used simple model for the description of the electron-surface interaction.