Striations in electronegative capacitively coupled radio-frequency plasmas: Effects of the pressure, voltage, and electrode gap

Yong Xin Liu, I. Korolov, Edmund Schüngel, You Nian Wang, Z. Donkó, Julian Schulze

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

Capacitively coupled radio-frequency (CCRF) CF4 plasmas have been found to exhibit a self-organized striated structure at operating conditions, where the plasma is strongly electronegative and the ion-ion plasma in the bulk region (largely composed of CF3 + and F- ions) resonates with the excitation frequency. In this work, we explore the effects of the gas pressure, the RF voltage, and the electrode gap on this striated structure by phase resolved optical emission spectroscopy and particle-in-cell/Monte Carlo collisions simulations. The measured electronic excitation patterns at different external parameters show a good general agreement with the spatio-temporal plots of the ionization rate obtained from the simulations. For a fixed driving frequency, the minima of the CF3 + or F- ion densities (between the density peaks in the bulk) are comparable and independent of other external parameters. However, the ion density maxima generally increase as a function of the pressure or RF voltage, leading to the enhanced spatial modulation of plasma parameters. The striation gap (defined as the distance between two ion density peaks) is approximately inversely proportional to the pressure, while it exhibits a weak dependence on the RF voltage and the electrode gap. A transition between the striated and non-striated modes can be observed by changing either the pressure or the RF voltage; for 13.56 and 18 MHz driving frequencies, we present a phase diagram as a function of the pressure and voltage amplitude parameters.

Original languageEnglish
Article number073512
JournalPhysics of Plasmas
Volume24
Issue number7
DOIs
Publication statusPublished - Jul 1 2017

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striation
radio frequencies
electrodes
electric potential
ions
optical emission spectroscopy
excitation
gas pressure
simulation
plots
phase diagrams
modulation
ionization
collisions
cells
electronics

ASJC Scopus subject areas

  • Condensed Matter Physics

Cite this

Striations in electronegative capacitively coupled radio-frequency plasmas : Effects of the pressure, voltage, and electrode gap. / Liu, Yong Xin; Korolov, I.; Schüngel, Edmund; Wang, You Nian; Donkó, Z.; Schulze, Julian.

In: Physics of Plasmas, Vol. 24, No. 7, 073512, 01.07.2017.

Research output: Contribution to journalArticle

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