Implementing a model for material dependent secondary electron emission coefficients in PIC/MCC simulations of capacitive RF plasmas

Ion induced secondary electron emission coefficients ($\gamma$) are a pivotal parameter utilized in Particle-in-Cell/ Monte Carlo collision (PIC/MCC) simulations to mimic realistic plasma-surface interactions. However, $\gamma$ is usually implemented in a rudimentary way, e.g. as an arbitrary constant. Experimental and theoretical studies have, however, suggested that it is significantly influenced by the surface material, its crystallinity, the impinging ion properties, etc. Therefore, we use an ab-initio model based on Hagstrum’s theory to calculate realistic $\gamma$-coefficients, which are then included in PIC/MCC simulations. To demonstrate the effect of material dependent $\gamma$ on modeling results, simulations of 13.56 MHz, single frequency argon and helium capacitive discharges are carried out based on different models for $\gamma$. We find that, depending on the material simulated, the plasma properties will change dramatically, if realistic surface coefficients are used. Thus, we conclude that a realistic material dependent implementation of $\gamma$ is required to obtain realistic simulation results.