Berlin 2005 – scientific programme
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P: Plasmaphysik
P 11: Niedertemperaturplasmen / Plasmatechnologie 5
P 11.2: Talk
Saturday, March 5, 2005, 11:30–11:45, HU 3038
Ion dynamics in plasma boundary sheaths of radio-frequency discharges operated with multiple frequencies — •Deborah O’Connell1,2, Roberto Zorat1, Miles Turner1, and Bert Ellingboe1 — 1Plasma Research Laboratory, Dublin City University, Ireland — 2present address: Institut für Plasma- und Atomphysik, Ruhr-Universität Bochum, Germany
The complex nature of multi frequency high voltage rf plasma boundary sheaths is investigated. A mass resolved ion energy analyser is incorporated into the grounded electrode of a confined symmetric capacitively coupled rf discharge. Two frequencies, 1.94 MHz and 27.12 MHz, are simultaneously supplied to the powered electrode. Discharges in hydrogen and deuterium are investigated. The relatively light ions respond to the temporal variations in the sheath potential allowing for detailed investigations of the sheath dynamics. Experimental results of ion energy distribution functions (IEDFs) and absolute ion fluxes are compared to a PIC simulation perfectly adapted to the experimental conditions. The agreement is in general very good. The basic concept of separate control of the ion flux and ion energy in dual frequency discharges can be confirmed. The ion flux is mainly controlled by the high frequency component. The IEDF is strongly influenced by both the low frequency and high frequency component. Double bi-modal structures in the IEDFs, caused by complex dynamics of dual frequency sheaths, can be explained and reproduced using a simple analytical model.