Temporal structure of electron heating in asymmetric single-frequency and dual-frequency capacitive discharges

The power dissipation in asymmetric capacitively coupled low-pressure plasmas can be drastically enhanced by the self-excitation of collective resonances. This applies to both Ohmic heating, which is related to collisions of electrons with neutrals, and stochastic heating which reflects the energy transfer from the oscillating plasma boundary sheath to the electrons. This work studies the phase-resolved structure of the power dissipation in asymmetric single-frequency and dual-frequency discharges on the basis of a self-consistent global model. A resonance-free global model (which represents the “traditional” scenario of the heating process) is consulted for comparison. It is shown that the energy dissipation in asymmetric capacitive discharges is enhanced around the moment of the sheath collapse but assumes the nonresonant value when the sheath extension is large. In the dual-frequency case, the effect is synchronized with the low-frequency cycle but strongly dependent on the value of the high-frequency power.