Detachment-induced electron production in the early afterglow of pulsed cc-rf oxygen plasmas
- University of Greifswald, Institute of Physics, Felix-Hausdorff-Str. 6, 17489 Greifswald (Germany)
Line integrated electron densities are measured by 160.28 GHz Gaussian beam microwave interferometry in a 10 Hz pulsed (50% duty cycle) cc-rf oxygen discharge, operating at 13.56 MHz. Depending on the processing parameters, the oxygen rf discharge displays two different operation modes regarding its electronegativity. For higher rf power with negative self-bias voltage above -220 V, the oxygen discharge acts as electropositive plasma (n{sub -}/n{sub e} Much-Less-Than 1), whereas at lower rf power and self-bias voltage the plasma becomes strongly electronegative (n{sub -}/n{sub e}>2). In the latter mode, a significant electron density increase is measured in the early afterglow (<100 {mu}s) within a pressure range from 20 to 100 Pa. By use of a simple rate equation model, the temporal behavior of the electron density could be reproduced for both modes of electronegativity. The electron production in the early afterglow is mainly caused due to the detachment of negative atomic oxygen ions by metastable oxygen molecules.
- OSTI ID:
- 22085969
- Journal Information:
- Physics of Plasmas, Vol. 19, Issue 7; Other Information: (c) 2012 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
- Country of Publication:
- United States
- Language:
- English
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