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P: Fachverband Plasmaphysik

P 20: Poster Session- Low Temperature Plasmas

P 20.11: Poster

Mittwoch, 2. März 2016, 16:30–19:00, Empore Lichthof

Secondary negative ions in oxygen CCP — •Sebastian Scheuer, Ralf Schneider, and Jürgen Meichsner — Institute of Physics, University of Greifswald, Felix-Hausdorff-Str. 6, 17489 Greifswald, Germany

The influence of electrode material on secondary negative ion emission was studied in an asymmetric, capacitively coupled radio frequency discharge at low oxygen pressure. Beside the stainless steel electrode the investigations were focused on several dielectrics, e.g., silica (SiO2), alumina (Al2O3), magnesia (MgO), on the powered electrode. The secondary negative ions, accelerated in the high-voltage RF sheath toward the plasma bulk and extracted at the grounded electrode, were measured by energy dispersive ion mass spectrometry. The energy distribution ranges from low energetic negative ions penetrating the low-voltage sheath at the grounded aperture of the mass spectrometer to the maximum kinetic energy corresponding to mean RF sheath voltage at the powered electrode. In particular, the high-energetic end of the ion energy distribution contains negative ions which were directly produced on the surface of the powered electrode. In the case of magnesia on the RF electrode the intensity of these energetic negative ions becomes significantly apparent in the ion energy distribution function. First results from PIC-MCC simulation adapted to the experiment are presented.