Electron Beams in Capacitively Coupled Radio-Frequency Discharges

The generation of electron beams by the expanding sheath is observed experimentally in asymmetric single-frequency capacitively coupled radio-frequency discharges using phase-resolved optical-emission spectroscopy. Depending on the discharge geometry and conditions, such beams can propagate through the entire discharge and are reflected at the opposing plasma boundary. They are closely related to stochastic heating, and their generation is enhanced by the plasma-series-resonance effect. Confinement of these energetic electrons can lead to an effective heating of the plasma.