RF MODULATION OF POSITIVE-ION ENERGIES IN LOW-PRESSURE DISCHARGES

In this work a filament-assisted dc argon discharge is generated between parallel electrodes. A rf signal (<13.56 MHz) is applied to one electrode in order to modulate the plasma potential. The degree of modulation is monitored using an emissive Langmuir probe. The velocity distribution of ions arriving at the earthed electrode is observed to respond to the rf modulation of the local space potential, the effect diminishing as the rf frequency is increased above the ion plasma frequency. A model is developed to describe the behavior of the ions to the rf modulation of the space potential. Good agreement between the simulation and experimental results is observed. The modulation of ion velocities by nonsinusoidal potentials is briefly examined.