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Title: The electrical asymmetry effect in geometrically asymmetric capacitive radio frequency plasmas

Abstract

The electrical asymmetry effect (EAE) allows an almost ideal separate control of the mean ion energy, , and flux, {Gamma}{sub i}, at the electrodes in capacitive radio frequency discharges with identical electrode areas driven at two consecutive harmonics with adjustable phase shift, {theta}. In such geometrically symmetric discharges, a DC self bias is generated as a function of {theta}. Consequently, can be controlled separately from {Gamma}{sub i} by adjusting the phase shift. Here, we systematically study the EAE in low pressure dual-frequency discharges with different electrode areas operated in argon at 13.56 MHz and 27.12 MHz by experiments, kinetic simulations, and analytical modeling. We find that the functional dependence of the DC self bias on {theta} is similar, but its absolute value is strongly affected by the electrode area ratio. Consequently, the ion energy distributions change and can be controlled by adjusting {theta}, but its control range is different at both electrodes and determined by the area ratio. Under distinct conditions, the geometric asymmetry can be compensated electrically. In contrast to geometrically symmetric discharges, we find the ratio of the maximum sheath voltages to remain constant as a function of {theta} at low pressures and {Gamma}{sub i} to depend onmore » {theta} at the smaller electrode. These observations are understood by the model. Finally, we study the self-excitation of non-linear plasma series resonance oscillations and its effect on the electron heating.« less

Authors:
; ;  [1]; ;  [2]
  1. Insitute for Plasma and Atomic Physics, Ruhr-University Bochum, 44780 Bochum (Germany)
  2. Institute for Theoretical Electrical Engineering, Ruhr-University Bochum, 44780 Bochum (Germany)
Publication Date:
OSTI Identifier:
22089422
Resource Type:
Journal Article
Journal Name:
Journal of Applied Physics
Additional Journal Information:
Journal Volume: 112; Journal Issue: 5; Other Information: (c) 2012 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0021-8979
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ARGON; ASYMMETRY; ELECTRODES; ELECTRON TEMPERATURE; ENERGY SPECTRA; EXCITATION; HARMONICS; HIGH-FREQUENCY DISCHARGES; IONS; PHASE SHIFT; PLASMA; PLASMA SIMULATION; PLASMA WAVES; RADIOWAVE RADIATION; RESONANCE; SYMMETRY

Citation Formats

Schuengel, E., Schulze, J., Czarnetzki, U., Eremin, D., and Mussenbrock, T. The electrical asymmetry effect in geometrically asymmetric capacitive radio frequency plasmas. United States: N. p., 2012. Web. doi:10.1063/1.4747914.
Schuengel, E., Schulze, J., Czarnetzki, U., Eremin, D., & Mussenbrock, T. The electrical asymmetry effect in geometrically asymmetric capacitive radio frequency plasmas. United States. https://doi.org/10.1063/1.4747914
Schuengel, E., Schulze, J., Czarnetzki, U., Eremin, D., and Mussenbrock, T. 2012. "The electrical asymmetry effect in geometrically asymmetric capacitive radio frequency plasmas". United States. https://doi.org/10.1063/1.4747914.
@article{osti_22089422,
title = {The electrical asymmetry effect in geometrically asymmetric capacitive radio frequency plasmas},
author = {Schuengel, E. and Schulze, J. and Czarnetzki, U. and Eremin, D. and Mussenbrock, T.},
abstractNote = {The electrical asymmetry effect (EAE) allows an almost ideal separate control of the mean ion energy, , and flux, {Gamma}{sub i}, at the electrodes in capacitive radio frequency discharges with identical electrode areas driven at two consecutive harmonics with adjustable phase shift, {theta}. In such geometrically symmetric discharges, a DC self bias is generated as a function of {theta}. Consequently, can be controlled separately from {Gamma}{sub i} by adjusting the phase shift. Here, we systematically study the EAE in low pressure dual-frequency discharges with different electrode areas operated in argon at 13.56 MHz and 27.12 MHz by experiments, kinetic simulations, and analytical modeling. We find that the functional dependence of the DC self bias on {theta} is similar, but its absolute value is strongly affected by the electrode area ratio. Consequently, the ion energy distributions change and can be controlled by adjusting {theta}, but its control range is different at both electrodes and determined by the area ratio. Under distinct conditions, the geometric asymmetry can be compensated electrically. In contrast to geometrically symmetric discharges, we find the ratio of the maximum sheath voltages to remain constant as a function of {theta} at low pressures and {Gamma}{sub i} to depend on {theta} at the smaller electrode. These observations are understood by the model. Finally, we study the self-excitation of non-linear plasma series resonance oscillations and its effect on the electron heating.},
doi = {10.1063/1.4747914},
url = {https://www.osti.gov/biblio/22089422}, journal = {Journal of Applied Physics},
issn = {0021-8979},
number = 5,
volume = 112,
place = {United States},
year = {Sat Sep 01 00:00:00 EDT 2012},
month = {Sat Sep 01 00:00:00 EDT 2012}
}