Greifswald 2009 – scientific programme

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P: Fachverband Plasmaphysik

P 8: Niedertemperaturplasmen

P 8.1: Talk

Tuesday, March 31, 2009, 13:30–13:45, INP-Staffelgeschoß

Experimental investigations of the Electrical Asymmetry Effect — •Julian Schulze¹, Edmund Schüngel¹, Zoltan Donko², Dirk Luggenhölscher¹, and Uwe Czarnetzki¹ — ¹Institute for Plasma and Atomic Physics, Ruhr-University Bochum — ²Hungarian Academy of Science, Budapest, Hungary

In 2008 a method to generate a variable DC self bias even in geometrically symmetric capacitively coupled radio frequency (CCRF) discharges was proposed based on an analytical model and a fluid simulation. If the discharge is operated at a fundamental frequency and its second harmonic, it was predicted that the resulting DC self bias can be adjusted by the phase angle between the applied voltage harmonics. A PIC simulation showed that this Electrical Asymmetry Effect (EAE) allows separate control of the energy and flux of ions at the electrode surfaces. In this work the EAE and the related separate control of ion energy and flux are tested experimentally. A geometrically symmetric CCRF discharge operated at 13.56 MHz and 27.12 MHz with variable phase angle between the harmonics is operated in argon at different pressures. The DC self bias, the energy as well as the flux of ions at the grounded electrode surface, and the space and phase resolved optical emission are measured. The results show that a DC self bias is generated as an almost linear function of the phase angle. This variable DC self bias indeed allows separate control of ion energy and flux in an almost ideal way under various discharge conditions. This work is funded by the DFG through GRK 1051.