Darmstadt 2008 – wissenschaftliches Programm

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P: Fachverband Plasmaphysik

P II: Poster: Niedertemperaturplasmen, Plasmatechnologie

P II.11: Poster

Dienstag, 11. März 2008, 11:00–13:00, Poster C3

Electric field reversals in single- and dual-frequency capacitively coupled radio frequency discharges at various pressures — •J Schulze¹, Z Donko², B Heil¹, D Luggenhölscher¹, T Mussenbrock³, R P Brinkmann³, and U Czarnetzki¹ — ¹Institute for Plasma and Atomic Physics, Ruhr-University Bochum — ²Hungarian Academy of Sciences, Budapest, Hungary — ³Institute for Theoretical Electrical Engineering, Ruhr-University Bochum

The spatio-temporal excitation in asymmetric single and symmetric dual-frequency discharges is investigated experimentally by Phase Resolved Optical Emission Spectroscopy and theoretically by simulations. The single frequency discharge is operated at 13.56 MHz and low pressures (< 1 Pa) in rare gases as well as molecular gases. The dual-frequency discharge is operated at 1.94 MHz + 27.12 MHz and 65 Pa in He-O2 with small rare gas admixture. In both cases maxima of the excitation rate during sheath contraction are observed indicating a reversal of the electric field. In the dual-frequency case a Particle in Cell (PIC) simulation is performed that reproduces the experimentally observed excitation profiles. It explicitly shows a reversed field at distinct phases. A fluid model using input parameters from the PIC simulation reproduces this scenario. Based on this fluid model the mechanisms leading to a field reversal can be understood. Depending on pressure those are either electron collisions with the neutral background gas, electron inertia, or a combination of both.

Funded by the DFG through SFB591, GRK1051, the Hungarian Scientific Research Fund and supported by Andor Technology.