The effect of secondary electrons on the separate control of ion energy and flux in dual-frequency capacitively coupled radio frequency discharges

Dual-frequency capacitive discharges are used to separately control the mean ion energy, ε ¯ ion , and flux, Γ ion , at the electrodes. We study the effect of secondary electrons on this separate control in argon discharges driven at 2 + 27 MHz at different pressures using Particle in Cell simulations. For secondary yield γ ≈ 0 , Γ ion decreases as a function of the low frequency voltage amplitude due to the frequency coupling, while it increases at high γ due to the effective multiplication of secondary electrons inside the sheaths. Therefore, separate control is strongly limited. ε ¯ ion increases with γ , which might allow an in situ determination of γ -coefficients.