Numerical Investigation of Reactive Species Generation in $$He/O_2$$ H e / O 2 Admixture Capacitively Coupled Plasma
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RESEARCH ARTICLE-PHYSICS
Numerical Investigation of Reactive Species Generation in He/O2 Admixture Capacitively Coupled Plasma Ziane Kechidi1
· Hannachi Zitouni2 · Abdelatif Tahraoui3 · Ahmed Hafid Belbachir4 · Soumia Bendella5
Received: 20 April 2020 / Accepted: 17 September 2020 © King Fahd University of Petroleum & Minerals 2020
Abstract We report results from a one-dimensional, numerical simulation of a capacitively coupled H e/O2 admixture plasma, operated at pressure varying from 1.5 to 7.5 Torr and over a range of molecular oxygen admixtures (H e + 0.1%O2 –H e + 10%O2 ). This study is used to investigate the effect of the gas pressure and the addition of small fractions of molecular oxygen on some important species production which have been extensively used for various biomedical applications and several new plasma technologies. The species densities have been presented, and the dominant key production processes have been identified. At a fixed (H e + 1%O2 ) admixture, the electron density decreases with increasing pressure, and the densities of negative ions are relatively high at high pressures and decrease for the positive ions. However, the atomic O, the molecular metastable O2 (v), singlet-delta O2 (a 1 1g ) and singlet-sigma O2 (b1 6+ g ) states are found to be the dominant species and their densities are weakly dependent on the gas pressure. At a fixed pressure, as the O2 admixture increases, the electron impact with O2 molecules becomes higher, and consequently, the electron generation decreases considerably. The formation of O, O2 (v), O2 (a 1 1g ) and O2 (a 1 1g ) increases until it reaches a peak at 4%O2 and then falls significantly with increasing O2 admixture. However, the atomic metastable O(1 D) and H e∗ are less important and they decrease rapidly due to collisional quenching or Penning ionization. The ozone O3 formation is optimal at 4%O2 . The positive and negative atomic and molecular ions are also relatively less important, and they decrease sharply with increasing O2 admixture due to ion-ion and ion-molecule neutralization. The addition of oxygen resulted in a decrease in all plasma species due to the electronegativity property of oxygen. These results are in fairly good agreement with some experimental observations and allow for a better understanding of the main physicochemical mechanisms taking place in H e/O2 plasmas admixtures. Keywords Reactive species production · Low-temperature plasmas · Capacitively coupled radiofrequency plasmas · H e/O2 admixture plasmas
1 Introduction
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Ziane Kechidi [email protected] ; [email protected] Hannachi Zitouni [email protected] Abdelatif Tahraoui [email protected] Ahmed Hafid Belbachir [email protected]
Non-equilibrium capacitively coupled discharges operating in H e/O2 admixtures at pressures ranging from few mTorrs to atmospheric pressure have been extensively used in many fields that expand from material processing to bioapplications. They have been proven to be promising plasma sources of
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