Electrical measurements in dusty plasmas as a detection method for the early phase of particle formation

Abstract

The formation of dust particles in reactive plasmas affects the electrical characteristics of the plasma. We have investigated the time resolved development of the electrical characteristics due to particle formation, i.e. the voltage and current at the surface of the powered electrode in capacitively coupled Ar–C2H2 and Ar–CH4 dusty plasmas. The stray impedances of the reaction chamber were characterized in order to trace the change in plasma impedance during particle formation. Using a simple equivalent circuit model the plasma impedance is represented as a series combination of a resistor and a capacitor. It was observed that the plasma impedance becomes more resistive as the particles grow. In the case of Ar–CH4 plasmas three different characteristic steps were observed, which might be related to the nucleation, coagulation and agglomeration phase of particle formation. Compared with other dust particle detection methods this technique is easy to implement, non-intrusive and very sensitive even for the smallest particles.