On the influence of electrode surfaces on the plasma chemistry and striations in a capacitive chlorine discharge

One-dimensional particle-in-cell/Monte Carlo collisional (PIC/MCC) simulations are performed on capacitive chlorine discharges [1] with 2.54 cm gap rf driven by a sinusoidal voltage at driving frequency of 13.56 MHz.  The properties of the discharge, the reaction rates for creation and loss of a few key species, the electron energy probability function, and the primary electron power absorption processes are explored as the gas pressure and the inclusion of secondary electron emission processes in the discharge model is varied.  The most realistic secondary electron emission model includes contribution from ions, electrons, and neutrals bombarding the electrodes.  The negative ion Cl^- is almost entirely created by dissociative attachment and lost through ion-ion recombination, and therefore the capacitive chlorine discharge is recombination dominated.  We apply Boltzmann term analysis to study the origination and properties of the electric field and the  electron power absorption within the electronegative core [2].  The discharge becomes increasingly Ohmic with increased pressure and eventually behaves as a resistive load.  Furthermore, we observe self organized striation structures in the capacitive chlorine discharge in a certain pressure regime [3].  The properties of the discharges are explored focusing on the striations, as the gas pressure and secondary electron emission are varied.   The striations start to appear at pressure around 15 Pa and peak in amplitude around 40 Pa and then decline again with further increase in pressure.  We find that the amplitude and the number of striations increase with the addition of secondary electron emission to the discharge model.