Particle coating in seeded dusty plasma reactor: Distribution of deposition rates

Abstract

We seed a low-pressure radio-frequency plasma with micron and submicron silica particles and induce surface deposition of plasma-generated solid films. This process produces surface coatings ranging from few nm to several hundred nm. The size distribution of the coated particles (core plus shell) is monitored as a function of time and is found to increase both in mean size as well as in variance. To explain the broadening of the distribution we propose a deposition model which assumes that the reaction rate is nonuniform within the plasma. This model predicts that the average particle radius increases linearly with deposition time with a slope equal to the average deposition rate while the variance increases as a quadratic function of time. These predictions compare favorably with experiments conducted with seeds ranging 0.1–2.3 μm in radius. Based on this model we are able to obtain the distribution of film deposition rates in the plasma. We find that this distribution is wide with a substantial fraction of particles experiencing very low deposition rates.