Particle-in-Cell/Monte Carlo Collision Simulations of Striations in Inductively Coupled Plasmas

Abstract

Striations in inductively coupled plasmas (ICPs) appear as a series of cocoons beneath a coil through which a source current is driven. In this study, we have simulated striations in ICPs using the particle-in-cell/Monte Carlo collision method. The simulated effects of pressure on striation characteristics are in good agreement with experimental observations. It is found that the discharge structure and electron heating mechanism of striated ICPs are markedly different from those of normal ICPs. In particular, electron heating occurs once in one rf cycle in striated ICPs but twice in normal ICPs. Electron heating in striated ICPs may be ascribed to a strong self-excited electric field induced by the oscillating motion of the electron density at approximately the ion density, resulting in a high electron temperature. Furthermore, the relationship between the spatial period of the striation and the discharge space is put forward as a generation criterion for striations in rf discharges. Striations tend to occur when the region of plasma generation due to ionization is adjacent to walls where plasma is lost. #

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

“…Self-organized striated structures of the plasma emission-established this way-have been observed in CCRF CF 4 plasmas by Phase Resolved Optical Emission Spectroscopy (PROES) and their formation was analyzed and understood by Particle in Cell / Monte Carlo Collision (PIC/MCC) simulations [31]. It is quite obvious that the physical origin of the striations in electronegative CCRF discharges is different from those observed previously in electropositive plasmas [33][34][35][36][37][38][39][40][41][42][43][44][45][46]. For example, one well-known scenario is the striated structure of DC glow discharges, wherein ion-acoustic or ionization waves are considered to be the origin of these features [33][34][35][36].…”

“…For example, one well-known scenario is the striated structure of DC glow discharges, wherein ion-acoustic or ionization waves are considered to be the origin of these features [33][34][35][36]. Striations can also occur in inductively coupled plasmas [37][38][39], atmospheric pressure CCRF He H 2 O ⁄ discharges [40], atmospheric pressure plasma jets [41][42][43] , plasma display panels [44], and plasma clouds in the ionosphere [45,46] , etc. In all of these systems, the appearance of striations is associated with the electron kinetics.…”

Striations in electronegative capacitively coupled radio-frequency plasmas: analysis of the pattern formation and the effect of the driving frequency

“…Very recently, a stratified filament occurring in the discharge tube of a RF argon APPJ was observed in numerical modeling, which identified the different nonlinear dependences of the ionization and recombination rates on the electron density as the reason for the formation of the spatial patterns [16]. In the low-pressure RF regime, stationary or moving striated structures at random intervals have also been observed in planar inductively coupled argon plasmas (ICP) [17][18][19]. The formation of these striations was inferred to arise from ionization waves similar to that in the positive column, also associated with the particular reactor geometry (e.g., an elongated tube or a narrow-gap ICP), but a comprehensive explanation is missing.…”

Experimental Observation and Computational Analysis of Striations in Electronegative Capacitively Coupled Radio-Frequency Plasmas

“…Strong modulations of the plasma density and light emission -termed as "striations" -have extensively been studied in electropositive DC discharges [19][20][21][22], wherein ion-acoustic or ionization waves form the basics of these features. Striations also occur in electropositive inductively coupled plasmas [23], plasma display panels [24], and in plasma clouds in the ionosphere [25,26]. In these system the appearance of striations is explained by theories based on the electron kinetics.…”