Hannover 2010 – scientific programme

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P: Fachverband Plasmaphysik

P 8: Poster: Low Temperature Plasmas I

P 8.20: Poster

Tuesday, March 9, 2010, 16:00–18:00, Lichthof

Optimization of the Electrical Asymmetry Effect in geometrically symmetric capacitively coupled radio frequency discharges — •Edmund Schüngel¹, Julian Schulze¹, Zoltan Donko², and Uwe Czarnetzki¹ — ¹Institute for Plasma and Atomic Physics, Ruhr-University Bochum — ²Hungarian Academy of Science

An electrical asymmetry in capacitively coupled radio frequency discharges with symmetrical electrode configuration can be induced by driving the discharge with a fundamental frequency and its second harmonic. For equal amplitudes of the applied voltage waveforms it has been demonstrated by modeling, simulation, and experiments that this Electrical Asymmetry Effect (EAE) leads to the generation of a variable DC self bias, that depends almost linearly on the phase angle between the driving voltages. Here the dependence of the DC self bias generated by the EAE on the choice of the driving voltage waveform is investigated experimentally, by a PIC simulation, and an analytical model. First, the EAE in dual frequency discharges is optimized by choosing optimum amplitudes of each applied harmonic. It is found that the ratio of high to low frequency amplitude should be about 1/2 to generate the strongest relative bias. Second, the EAE in multi-frequency discharges is investigated. It is found that the maximum relative DC self bias can be strongly enhanced by applying multiple consecutive frequencies with particular amplitudes to the discharge. This optimization of the EAE should allow a better control of the ion energy over an energy range that is significantly broader than before.