Generation of highly energetic electrons through interaction with modulated plasma sheaths
Sebastian Wilczek, Jan Trieschmann, Julian Schulze, Edmund Schüngel, Ralf Peter Brinkmann, Aranka Derzsi, Ihor Korolov, Zoltan Donko, Thomas Mussenbrock
WELTPP-17, Kerkrade, The Netherlands, 20-21 November (oral contribution)
In capacitively coupled radio frequency discharges a fraction of electrons is accelerated due to the expansion of the modulated plasma sheath. Especially at low pressures, these beam-like electrons have energies much higher than the ionization threshold and are very important to sustain the plasma. This effect is persistent, even if secondary electron-emission is excluded. Under distinct discharge conditions the electron beams disturb the plasma bulk drastically, which leads to a violation of quasi-neutrality. Consequently, strong electric fields exist even in the center of the discharge. In this work, the formation of highly energetic electrons is investigated by means of 1d3v Particle-In-Cell simulations. It is shown that the number of electron beams as well as the modulation of the plasma sheaths can be modified with tuning the driving voltage amplitude. Additionally, the excitation at frequencies close to the local electron plasma frequency plays a major role in conjunction with local resonance phenomena.