Grain growth in processing plasmas

In this paper we revisit the problem of grain growth in processing plasmas, recently reviewed by Watanabe (1997). in our model we include the effect o f grain size dependence on secondary electron emission. we find that the se condary emission from the grains due to energetic gamma-electrons from the negatively biased electrode cannot alone produce grains of opposite polarit y (i.e. the smaller grains are positively charged and the larger grains are negatively charged), but could do so if additionally there is electron dep letion. While electron depletion occurs in the sheath due to its negative p otential, it can also occur at the sheath edge due to absorption by the lar ge population of dust grains. Additionally, we note that even at the sheath edge stochastic heating of the smaller grains by energetic gamma-electrons leading to stochastic thermionic emission could also lead to a small fract ion of very small grains to be positive at any time.