Bochum 2015 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe
P: Fachverband Plasmaphysik
P 18: Low Temperature Plasmas II
P 18.5: Vortrag
Mittwoch, 4. März 2015, 11:45–12:00, HZO 30
Instabilities in a capacitively coupled RF oxygen plasma — •Christian Küllig, Thomas Wegner, and Jürgen Meichsner — Institute of Physics, University of Greifswald
Instabilities in a capacitively coupled radio frequency (13.56 MHz) plasma (CCP) in oxygen were experimentally investigated using Gaussian beam microwave interferometry, Langmuir probe diagnostics and optical emission spectroscopy. The fluctuating line integrated electron density, spatio-temporally resolved floating potential and optical emission intensity were measured, respectively. Whereby, the appearance of an instable RF plasma depends on the total gas pressure and RF power. The frequency of the periodic fluctuations varies between 0.3 to 3 kHz. The electron density fluctuation is between 0.2×1015 and 3.5×1015 m−2, which can be the same order of magnitude as the mean electron density. The temporally resolved floating potential profiles show that the instability represents a kind of discharge breathing. During one fluctuation period the discharge changes between a low and high electronegative mode, whereupon the electric field reversal appears additionally to the RF sheath heating at the high electronegative mode. Furthermore, a perturbation calculation was performed, taking into account four particle balance equations (O2+, e, O−, O2−) and 16 elementary processes, which provides a fluctuation frequency in the range comparable to the experimental results. The calculation indicates the important role of the negative ions and the interaction of ionization, attachment and detachment processes for the origin of the instability. // Funded by the DFG CRC, Transregio 24, project B5.