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

Liu, Yong‐Xin; Korolov, Ihor; Schüngel, Edmund; Wang, You Nian; Donkó, Zoltán; Schulze, Julian

doi:10.1063/1.4993603

Cited by 30 publications

(48 citation statements)

References 66 publications

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“…The formation of such striations was already reported in direct current (DC) glow discharges. 24,[26][27][28] For RF capacitive coupled discharges, striations have also been also observed, in electronegative gases 25 and in argon, when plasma is created between two wires wrapped around a long dielectric tube, over a certain range of frequencies and gas pressures. 29,30 The non-linear dependence of the ionization rate on the electron density is shown to be the main underlying mechanism of the striation phenomena.…”

Section: A First Characterization (Reactor A)mentioning

confidence: 99%

Experimental and numerical study of the plasma in coaxial capacitive coupled radio frequency discharge

Alhomsi

Bauville

Pasquiers

et al. 2021

Journal of Applied Physics

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A coaxial configuration of discharge is proposed for plasma surface treatment and possibly other applications. The reactor is based on a cylindrical structure, with the inner cylinder radio frequency powered (RF, 13.56 MHz) and the outer cylinder grounded, playing the role of a guard ring. The charged species can escape from the inner cavity through two longitudinal slits made in both cylinders, aligned to each other, and producing a linear slab of plasma. Hence, it is possible to project the plasma directly onto a surface placed under the slits, called external plate. The operation of this device is uniform and stable in argon for a large pressure range (0.8-50 mbar). Furthermore, simulations using the Plasimo™ software package were performed to evaluate the plasma parameters and to explain the experimental results. The ion flux on the surface exposed to this plasma increases when RF power increases, and the pressure or gap distance to the plate decreases. This cylindrical capacitive coupled plasma configuration can be very effective for surface treatment of different materials (conductors or insulators) on large area (when the plate or the system is moving perpendicular to the slits) due to energetic ions and active species released from the plasma.

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Section: A First Characterization (Reactor A)mentioning

confidence: 99%

Experimental and numerical study of the plasma in coaxial capacitive coupled radio frequency discharge

Alhomsi

Bauville

Pasquiers

et al. 2021

Journal of Applied Physics

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“…The plasma polymerization involves plasmas of complex organic vapors, which have a larger range of species including radicals, ionic oligomers and fragmented neutrals [10,11]. For this purpose, two different gases (argon and oxygen) are used and compared for an electrode separation of 22cm at a constant gas pressure of 100mTorr.…”

Section: Depositing Monomersmentioning

confidence: 99%

Numerical simulation of an RF asymmetric nonthermal plasma reactor used for plasma polymerisation

Elaissi

Alyousef

2019

IJM

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The aims of this paper is to investigate the control of plasma properties via the geometrical asymmetry effect in a capacitive coupled discharge used for polymer processing. The simulation results prove that the bulk position and density profiles of positive ions, negative ions, and electrons have a clear dependence on geometric asymmetry effect. The underlying mechanisms identified shows a more collisional sheath at the smaller powered surface due to the larger sheath width, and a higher energy at the smaller surface due to the higher mean sheath voltage compared to the larger surface. The argon modelling results are compared to experimental results from the literature for a range of operating conditions. The results show that the argon model results can be used to predict the plasma parameters for other gases used for polymer processing.

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“…Besides, in their latest research they found that the transition could also appear by adjusting the voltage amplitude, gas pressure or electrode gap [21]. However, in all of the related investigations of STR mode, the effect of secondary electron emission on discharges was not taken into account so far, neither was the transition of the electron heating mode caused by it.…”

Section: Introductionmentioning

confidence: 99%

Disruption of self-organized striated structure induced by secondary electron emission in capacitive oxygen discharges

Wang

Wen

Zhang

et al. 2019

Plasma Sources Sci. Technol.

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Self-organized striated structure has been observed experimentally and numerically in CF 4 plasmas in radio-frequency capacitively coupled plasmas (RF CCPs) recently (Liu et al 2016 Phys. Rev. Lett. 116 255002). In this work, the striated structure is investigated in a capacitively coupled oxygen discharge with the introduction of the effect from the secondary electron emission, based on a particle-in-cell/Monte Carlo collision model (PIC/MCC). As we know, the transport of positive and negative ions plays a key role in the formation of striations in electronegative gases, for which, the electronegativity needs to be large enough.As the secondary electron emission increases, electrons in the sheaths gradually contribute more ionization to the discharge. Meanwhile, the increase of the electron density, especially in the plasma bulk, leads to an increased electrical conductivity and a reduced bulk electric field, which would shield the ions' mobility. These changes result in enlarged striation gaps.And then, with more emitted electrons, obvious disruption of the striations is observed accompanied with a transition of electron heating mode. Due to the weakened field, the impact ionization in the plasma bulk is attenuated, compared with the enhanced ionization caused by secondary electrons. This would lead to the electron heating mode transition from striated (STR) mode to γ-mode. Besides, our investigation further reveals that γ-mode is more likely to dominate the discharge under high gas pressures or driving voltages.

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

Cited by 30 publications

References 66 publications

Experimental and numerical study of the plasma in coaxial capacitive coupled radio frequency discharge

Experimental and numerical study of the plasma in coaxial capacitive coupled radio frequency discharge

Numerical simulation of an RF asymmetric nonthermal plasma reactor used for plasma polymerisation

Disruption of self-organized striated structure induced by secondary electron emission in capacitive oxygen discharges

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