On the efficiency of the electron sheath heating in capacitively coupled radio frequency discharges in the weakly collisional regime

In low pressure, capacitively coupled rf discharges mode transitions in the shape of the electron energy distribution function on variation of the pressure have been observed previously, and have been interpreted as a transition from dominating stochastic to dominating Joule heating. In this letter we present a similar mode transition, which has been observed at constant discharge pressure on variation of the rf current density through the discharge. By comparison to a parametric kinetic model it is shown that a dependence of the sheath heating efficiency on the magnitude of the rf sheath potentials can be considered as a possible explanation of the mode transition.