Simulation study of the nanoparticles nucleation in a pulse-modulated capacitively coupled rf acetylene discharge

The multi-fluid plasma equations are combined with the hydrocarbon chemical kinetics to simulate the nucleation stage of the nanoparticle formation in a pulse-modulated capacitively coupled rf acetylene discharge. The simulation code is validated by comparing its results with the available experimental and simulation results, and the agreement is quite satisfactory. It is shown that, with pulsing of the rf power, periodic oscillations develop on the temporal profiles of all hydrocarbon species. The amplitude of the oscillations decreases with the increasing pulse repetition frequency and species mass. On the long time scale of several pulse periods, the average number density of neutral molecules grows linearly with time. However, due to strong wall losses, radicals are saturated after experiencing an initial linear growth. The average number density of large neutral molecules and radicals increases with the increasing pulse repetition frequency and duty ratio. Anions are strongly affected by the power modulation, and their amplitude of oscillations is much larger than that of the radicals. Cations oscillate almost simultaneously with the electrons, and as their average number density does not grow on the long time scale, they do not play a noticeable role in the nucleation process. All roots of the nanoparticle formation can be effectively suppressed when pulses of low repetition frequency and low duty ratio are applied. Published by AIP Publishing.