Experimental observation and computational analysis of striations in electronegative capacitively coupled radio-frequency plasmas

TL;DR

This study reports the first experimental observation of striations in electronegative RF plasmas and explains their formation through particle-based simulations, revealing a resonance-driven instability mechanism.

Contribution

It combines experimental observation with computational analysis to identify and understand the resonance-driven origin of striations in electronegative RF plasmas.

Findings

First experimental detection of striations in electronegative RF plasmas

Resonance between RF frequency and ion-ion plasma eigenfrequency causes electric field modulation

Simulations confirm growth and development of the instability

Abstract

Self-organized spatial structures in the light emission from the ion-ion capacitive RF plasma of a strongly electronegative gas (CF4) are observed experimentally for the first time. Their formation is analyzed and understood based on particle-based kinetic simulations. These "striations" are found to be generated by the resonance between the driving radio-frequency and the eigenfrequency of the ion-ion plasma (derived from an analytical model) that establishes a modulation of the electric field, the ion densities, as well as the energy gain and loss processes of electrons in the plasma. The growth of the instability is followed by the numerical simulations.