Hannover 2010 – scientific programme

Parts | Days | Selection | Search | Downloads | Help

P: Fachverband Plasmaphysik

P 6: Low Temperature Plasmas I

P 6.4: Talk

Tuesday, March 9, 2010, 15:10–15:25, B 305

Excitation dynamics in electrically asymmetric capacitively coupled radio frequency discharges - Experiment, simulation, and model — •Julian Schulze¹, Edmund Schüngel¹, Zoltan Donko², and Uwe Czarnetzki¹ — ¹Institute for Plasma and Atomic Physics, Ruhr-University Bochum — ²Hungarian Academy of Science

The symmetry of capacitively coupled radio frequency (CCRF) discharges can be controlled electrically by applying a fundamental frequency and its second harmonic with fixed but adjustable phase shift θ between the driving voltages. In such a discharge a variable DC self bias is generated as an almost linear function of θ for 0°<θ<90°. This Electrical Asymmetry Effect allows separate control of ion energy and flux at the electrodes. Here electron dynamics in electrically asymmetric geometrically symmetric dual frequency discharges operated in argon at 13.56MHz and 27.12MHz is investigated experimentally, by a PIC simulation, and by an analytical model. At high pressures the excitation dynamics works differently compared to conventional CCRF discharges: Unlike classical discharges the time modulated fractions of the maximum excitation rates adjacent to each electrode within one low frequency period will be similar (symmetric excitation), if the DC self bias is strong (θ=0°, 90°) and significantly different (asymm. exc.), if the bias vanishes (θ=45°). At low pressures the excitation dynamics works similar to classical discharges, i.e. the excitation will be asymmetric, if the bias is strong, and symmetric, if the bias vanishes. This dynamics is understood in the frame of an analytical model, which could be applied to other types of CCRF discharges as well.