Near-electrode sheath dynamics, current anharmonicity and battery effect in asymmetrical, low-pressure radio-frequency discharges

The asymmetrical RF discharge is considered on the basis of a simple model. Simple and clear formulae are given to describe the motion of near-electrode sheath-plasma interfaces and evolution of anharmonic current, and to describe self-bias when there is a blocking capacitor in an external circuit. It is shown that in the case of a rather high blocking capacitor in an asymmetric discharge, positive charge flows into the large electrode, not electrons (as usual). The 'battery' effect is discussed, i.e. the arising of constant EFM and direct current flow in an asymmetric discharge in the case when only conductors are in the external circuit. The model and simple computational formulae are convenient to interpret experiments and to make it possible to estimate discharge and plasma parameters from electric measurements of current and potentials.