Dynamic effects in dual-frequency capacitively coupled discharges

Investigations of the discharge current shape in a low frequency single frequency discharge and in a dual frequency discharge are performed in this paper. For this purpose a Particle in cell with Monte-Carlo Collisions numerical simulation of the capacitively coupled discharge in argon, operated at frequencies of 1.76 MHz and 81 MHz, is carried out. As a result the non-sinusoidal, close to triangle shape of the discharge current is obtained even for the case of a symmetric discharge. The physical reason of such nonsinusoidal behavior of the discharge current is the dynamic structure of the discharge sheaths. Corresponding to the discharge current, the sheath edge motion is also non-sinusoidal and non-symmetric. These results may be important for the appropriate choice of the current and voltage waveforms in analytic modeling of single and dual frequency discharges.