Modeling of particulate coagulation in low pressure plasmas

In this paper we study the growth of nanometer particles in low pressure pl asmas due to coagulation. We describe results of a model which involves the self-consistent determination of plasma properties, the description of par ticle charging, as well as the description of the particle size distributio n via solution of the general dynamic equation for an aerosol. Our results show that particle coagulation in the low pressure plasma is enhanced compa red to coagulation in neutral aerosols due to the attraction of oppositely charged particles. The temporal behavior of the coagulation follows the sam e laws as coagulation of neutral particles as long as the density of nanome ter particles is larger than the positive ion density in the plasma. The po sitive ion density can be considered as the critical density for coagulatio n to occur. We also show that the details of the particle charging mechanis m are only of minor importance for the coagulation dynamics but of great-im portance for the accurate prediction of plasma parameters. [S1063-651X(99)0 1407-5].