Discharge impedance evolution, stray capacitance effect, and correlation with the particles size in a dusty plasma

Abstract

Dust particles growing or injected in a plasma modify significantly the impedance of capacitively coupled radio frequency discharges. The principal modifications are the increase of the plasma bulk resistance and of the plasma sheath capacitance. In this work, we propose a method to evaluate the impedance of the discharge (sheath + plasma bulk) during the growth of dust particles in a plasma. This method does not require the measurement of any current/voltage phase shift. Then, the evolution of the power coupled into the plasma as well as the voltage drop across the plasma bulk are derived. It follows that the plasma coupled power increases by a factor of five during the dust growth. The effect of the reactor stray capacitance on the power coupled to the plasma is underlined. Finally, a perfect correlation between the evolution of the size of the dust particles in the plasma and the increase of the plasma/electrode sheath capacitance suggests that charged dust particles induce an electrostatic force on the plasma sheath. An analytical model is proposed in order to take this phenomenon into account in future dusty plasma electrical modelling.