Electron Kinetics in Radio-Frequency Atmospheric-Pressure Microplasmas

Iza, Felipe; Lee, Jae Koo; Kong, Michael G.

doi:10.1103/physrevlett.99.075004

Cited by 227 publications

(225 citation statements)

References 22 publications

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“… -=0, and the electron loss balances the positive ion flux thereby keeping the plasma quasi-neutral. Although atmospheric-pressure sheath-dominated discharges in which quasi-neutrality does not hold have been reported in the literature, these occur in discharges with a smaller gap than the 2mm considered in this study [19,20] . Diffusion in the radial direction is neglected here since the mean distance travelled by particles during their lifetime is much shorter than the radius of the electrodes [14,21] : for a typical lifetime () of 1ms and a diffusion constant (D) of 1cm 2 /s, the distance travelled in a lifetime is Reaction rates needed to determine the generation/loss of species in the discharge (G k ) depend on the mean electron energy.…”

Section: Computational Modelmentioning

confidence: 86%

A theoretical insight into low-temperature atmospheric-pressure He+H₂plasmas

Liu

Iza

Wang

et al. 2013

Plasma Sources Sci. Technol.

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H 2 -containing low-temperature plasmas are used in a wide range of industrial applications. In the past decades, efforts have been made to understand and improve the performance of these plasmas, mainly when operated at low-and medium-pressures. Studies of hydrogen containing plasmas at atmospheric pressure, however, are scarce despite the potential advantage of operation in a vacuum free environment. Here the chemistry of low-temperature atmospheric-pressure He+H 2 plasmas is studied by means of a global model that incorporates 20 species and 168 reactions. It is found that for a fixed average input power the plasma density decreases sharply when the H 2 concentration is higher than ~0.2%, whereas the atomic H density peaks at a H 2 concentration of ~2%. Operation at larger hydrogen concentrations leads to lower plasma density and lower H concentration because at high H 2 concentrations significant power is dissipated via vibrational excitation of H 2 and there is an increasing presence of negative ions (H -). Key plasma species and chemical processes are identified and reduced sets of reactions that capture the main physicochemical processes of the discharge are proposed for use in computationally-demanding models. The actual waveform of the input power is found to affect the average density of electrons, ions and metastables but it has little influence on the density of species requiring low-energy for their formation, such as atomic hydrogen and vibrational states of hydrogen.

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Section: Computational Modelmentioning

confidence: 86%

A theoretical insight into low-temperature atmospheric-pressure He+H₂plasmas

Liu

Iza

Wang

et al. 2013

Plasma Sources Sci. Technol.

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“…For the single RF discharge under atmospheric pressure, different ionization mechanisms including sheath expansion, sheath collapse and sheath gas breakdown can be involved [49,50]. The dominant mechanism depends on the amplitude of the voltage or the input power [51].…”

Section: Rf Dischargementioning

confidence: 99%

Atmospheric-pressure diffuse dielectric barrier discharges in Ar/O₂gas mixture using 200 kHz/13.56 MHz dual frequency excitation

Liu

Starostin²,

Peeters

et al. 2018

J. Phys. D: Appl. Phys.

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IntroductionDevelopment of a large linear or volumetric source of diffuse non-thermal plasma at atmospheric pressure remains to be an essential challenge both from a scientific and a technological point of view. Such a source is required in various applications including plasma-assisted gas phase chemical conversion, surface modification and synthesis of high quality functional thin films [1][2][3][4]. The emerging atmospheric-pressure plasma enhanced chemical vapour deposition (AP-PECVD) technology can potentially achieve a considerable cost efficiency in comparison to the common low-pressure plasma methods, by the possibility of in-line production and by avoiding expensive large-footprint vacuum equipment [5]. One of the common ways to create a large area non-thermal plasma at atmospheric pressure is the dielectric barrier discharge (DBD) AbstractAtmospheric-pressure diffuse dielectric barrier discharges (DBDs) were obtained in Ar/O 2 gas mixture using dual-frequency (DF) excitation at 200 kHz low frequency (LF) and 13.56 MHz radio frequency (RF). The excitation dynamics and the plasma generation mechanism were studied by means of electrical characterization and phase resolved optical emission spectroscopy (PROES). The DF excitation results in a time-varying electric field which is determined by the total LF and RF gas voltage and the spatial ion distribution which only responds to the LF component. By tuning the amplitude ratio of the superimposed LF and RF signals, the effect of each frequency component on the DF discharge mechanism was analysed. The LF excitation results in a transient plasma with the formation of an electrode sheath and therefore a pronounced excitation near the substrate. The RF oscillation allows the electron trapping in the gas gap and helps to improve the plasma uniformity by contributing to the pre-ionization and by controlling the discharge development. The possibility of temporally modifying the electric field and thus the plasma generation mechanism in the DF discharge exhibits potential applications in plasma-assisted surface processing and plasma-assisted gas phase chemical conversion.

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“…There have been many studies carried out in associated fields to advance practical applications and fundamental theoretical work. [6][7][8][9][10] In the conventional CAP discharge, a sinusoidal mono-excitation source is often adopted with a frequency range from the kHz to MHz regime. However, it is difficult to achieve independent control and optimization of plasma parameters by considering the ability of a singular excitation source.…”

Section: All Article Content Except Where Otherwise Noted Is Licensmentioning

confidence: 99%

Electron heating and mode transition in dual frequency atmospheric pressure argon dielectric barrier discharge

et al. 2017

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Plasma ionization, excitation, mode transitions and associated electron heating mechanisms in atmospheric pressure dielectric barrier discharges (DBD) driven by dual radio frequency sources are investigated in this paper. The electrons are found to be heated mainly by the high frequency component in the plasma bulk when discharged in α mode. On the contrary, the low frequency component is primarily responsible for heating in the sheath which is caused by intense motion in the sheath. It was also found that variation of the lower frequency component ratio could effectively modulate the electron energy distribution as determined from time averaged EEDF. The results above have demonstrated that the independent control of plasma parameters via non-linear synergistic effect between the dual frequency sources can be achieved through reasonable selection of processing parameters.

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Electron Kinetics in Radio-Frequency Atmospheric-Pressure Microplasmas

Cited by 227 publications

References 22 publications

A theoretical insight into low-temperature atmospheric-pressure He+H₂plasmas

A theoretical insight into low-temperature atmospheric-pressure He+H₂plasmas

Atmospheric-pressure diffuse dielectric barrier discharges in Ar/O₂gas mixture using 200 kHz/13.56 MHz dual frequency excitation

Electron heating and mode transition in dual frequency atmospheric pressure argon dielectric barrier discharge

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Electron Kinetics in Radio-Frequency Atmospheric-Pressure Microplasmas

Cited by 227 publications

References 22 publications

A theoretical insight into low-temperature atmospheric-pressure He+H2plasmas

A theoretical insight into low-temperature atmospheric-pressure He+H2plasmas

Atmospheric-pressure diffuse dielectric barrier discharges in Ar/O2gas mixture using 200 kHz/13.56 MHz dual frequency excitation

Electron heating and mode transition in dual frequency atmospheric pressure argon dielectric barrier discharge

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A theoretical insight into low-temperature atmospheric-pressure He+H₂plasmas

A theoretical insight into low-temperature atmospheric-pressure He+H₂plasmas

Atmospheric-pressure diffuse dielectric barrier discharges in Ar/O₂gas mixture using 200 kHz/13.56 MHz dual frequency excitation