Study on nanoparticle coagulation and charging dynamics in pulse-modulated radio-frequency acetylene discharges

Here, we report on how nanoparticles behave in pulse-modulated radio-frequency acetylene discharges as studied by combining an aerosol dynamics model with a one-dimensional hydrodynamic model. A discussion is presented of how the duty cycle and modulation frequency affect the electron density and temperature, the negative ion density, and the nanoparticle density and charge. First, the electron density increases significantly upon decreasing the duty cycle or modulation frequency at the same average power, and the electron temperature drops more rapidly than the electron density in the afterglow. Second, the negative ions move to the wall when the pulse-off time is sufficiently long, which results in a lower nanoparticle density, especially for large nanoparticles. Finally, the nanoparticle charge can be reduced by appropriately decreasing the duty cycle or the modulation frequency, while only the large nanoparticle charge decreases sharply when the pulse-off time is sufficiently long.