Instabilities in a capacitively coupled oxygen plasma
- Institute of Physics, University of Greifswald, Felix-Hausdorff-Str. 6, 17489 Greifswald (Germany)
Periodic fluctuations in the frequency range from 0.3 to 3 kHz were experimentally investigated in capacitively coupled radio frequency (13.56 MHz) oxygen plasma. The Gaussian beam microwave interferometry directly provides the line integrated electron density fluctuations. A system of two Langmuir probes measured the floating potential spatially (axial, radial) and temporally resolved. Hence, the floating potential fluctuation development is mapped within the discharge volume and provides a kind of discharge breathing and no wave propagation. Finally, it was measured the optical emission pattern of atomic oxygen during the fluctuation as well as the RF phase resolved optical emission intensity at selected phase position of the fluctuation by an intensified charge-coupled device camera. The deduced excitation rate pattern reveals the RF sheath dynamics and electron heating mechanisms, which is changing between low and high electronegativity during a fluctuation cycle. A perturbation calculation was taken into account using a global model with 15 elementary collision processes in the balance equations for the charged plasma species (O{sub 2}{sup +}, e, O{sup −}, O{sub 2}{sup −}) and a harmonic perturbation. The calculated frequencies agree with the experimentally observed frequencies. Whereby, the electron attachment/detachment processes are important for the generation of this instability.
- OSTI ID:
- 22410276
- Journal Information:
- Physics of Plasmas, Vol. 22, Issue 4; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CHARGE-COUPLED DEVICES
DISTURBANCES
ELECTRON ATTACHMENT
ELECTRON DENSITY
ELECTRONEGATIVITY
EXCITATION
FLUCTUATIONS
INTERFEROMETRY
KHZ RANGE 01-100
LANGMUIR PROBE
MHZ RANGE 100-1000
MICROWAVE RADIATION
OXYGEN
PHOTON EMISSION
PLASMA
PLASMA HEATING
PLASMA INSTABILITY
RADIOWAVE RADIATION
WAVE PROPAGATION