Large‐area atmospheric pressure dielectric barrier discharges in Ar–HMDSO mixtures: Experiments and fluid modelling

Loffhagen, Detlef; Becker, Markus M.; Hegemann, Dirk; Nisol, Bernard; Watson, Sean; Wertheimer, M. R.; Klages, Claus‐Peter

doi:10.1002/ppap.201900169

Cited by 19 publications

(25 citation statements)

References 48 publications

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“…This finding agrees well with the analysis provided by [30], where the consumption of TMS in an atmospheric-pressure Ar-TMS microplasma was found to be more effective at low TMS concentrations compared with their consumptions at high concentrations. A similar trend of monomer depletion in a large-area atmosphericpressure DBD in Ar-HMDSO mixtures was recently discussed in [37]. This decrease of the percentage monomer consumption during the residence time of the plasma in the discharge with increasing monomer fraction is a direct consequence of the finite number of excited argon species available to dissociate and/or ionize the monomer via energy transfer.…”

Section: Temporal Behavior Of Dbds In Ar-tms Mixturessupporting

confidence: 72%

“…The time-dependent, spatially one-dimensional model considers the axial component z of the plasma between the plane-parallel, dielectric covered electrodes, where the electrode on the left side is powered by the voltage (1) and that to the right is grounded. Such a spatially one-dimensional treatment is well suited for the analysis of DBDs operating in the homogeneous or glow mode [36] and was successfully applied for the analysis of DBDs, e.g., in Ar [34], Ar-HMDSO mixtures [35,37], N 2 with 0.1 vol% O 2 [38], and CO 2 [39].…”

Section: Description Of the Modelmentioning

confidence: 99%

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Modeling of Atmospheric-Pressure Dielectric Barrier Discharges in Argon with Small Admixtures of Tetramethylsilane

Loffhagen

Becker

Czerny

et al. 2020

Plasma Chem Plasma Process

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A time-dependent, spatially one-dimensional fluid-Poisson model is applied to analyze the impact of small amounts of tetramethylsilane (TMS) as precursor on the discharge characteristics of an atmospheric-pressure dielectric barrier discharge (DBD) in argon. Based on an established reaction kinetics for argon, it includes a plasma chemistry for TMS, which is validated by measurements of the ignition voltage at the frequency $$f =86.2\, {\hbox{kHz}}$$ f = 86.2 kHz for TMS amounts of up to 200 ppm. Details of both a reduced Ar-TMS reaction kinetics scheme and an extended plasma-chemistry model involving about 60 species and 580 reactions related to TMS are given. It is found that good agreement between measured and calculated data can be obtained, when assuming that 25% of the reactions of TMS with excited argon atoms with a rate coefficient of $$3.0 \times 10^{-16}\, {\hbox{m}^3/\hbox{s}}$$ 3.0 × 10 - 16 m 3 / s lead to the production of electrons due to Penning ionization. Modeling results for an applied voltage $${U}_{{\mathrm{a}},0} = 4\, {\hbox{kV}}$$ U a , 0 = 4 kV show that TMS is depleted during the residence time of the plasma in the DBD, where the percentage consumption of TMS decreases with increasing TMS fraction because only a finite number of excited argon species is available to dissociate and/or ionize the precursor via energy transfer. Main species resulting from that TMS depletion are presented and discussed. In particular, the analysis clearly indicates that trimethylsilyl cations can be considered to be mainly responsible for the film formation.

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Section: Temporal Behavior Of Dbds In Ar-tms Mixturessupporting

confidence: 72%

Section: Description Of the Modelmentioning

confidence: 99%

Modeling of Atmospheric-Pressure Dielectric Barrier Discharges in Argon with Small Admixtures of Tetramethylsilane

Loffhagen

Becker

Czerny

et al. 2020

Plasma Chem Plasma Process

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“…[ 117 ] Pure HMDSO or HMDSO‐dominated plasma was found to show a decrease both in n e and T e as compared with pure Ar plasma at comparable conditions, indicating a large energy transfer into dissociation. [ 94,118,119 ] A 20% drop in T e was reported already for highly diluted HMDSO/Ar plasma, which saturated at about 30% lower T e values for higher HMDSO concentrations (RF CCP, 6 Pa). [ 54 ] By comparing Figure 2a with Figure 4d, a drop in n e can also be noticed for the HMDSO plasma conditions examined here.…”

Section: Resultsmentioning

confidence: 88%

“…Low deposition rates related to a reduced conversion have also been reported in an MW plasma fed with pure HMDSO at p = 35 Pa with T e ≈ 1.7 eV. [ 84 ] Furthermore, for even lower T e < 1.5 eV, as for example observed at atmospheric pressure, [ 119 ] a highly inefficient energy transfer through electrons yielding film‐forming species might be expected. Indeed, in an AP plasma system fed with N 2 /HMDSO, very low deposition rates were observed when oxygen impurities, as far as possible, could be avoided.…”

Section: Resultsmentioning

confidence: 93%

Plasma polymerization of hexamethyldisiloxane: Revisited

Hegemann

Bülbül

Hanselmann

et al. 2020

Plasma Processes & Polymers

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Activation reactions of molecules in plasma are investigated using plasma polymerization of hexamethyldisiloxane as a model system for plasma‐state polymerization. Underlying reaction pathways and film‐forming mechanisms are revisited based on a simplified macroscopic approach, considering the average energy available per monomer particle, Epl, in relation to the threshold energy, Eth, which represents an activation barrier for plasma polymerization. Basic principles are discussed involving averaged values for collision frequency, cross‐section, and reaction rate to produce film‐forming species combining macroscopic and microscopic quantities. Considering the energy uptake from the electric field by the electrons, the energy transfer from electrons to monomer molecules, and the conversion into film‐forming species, it is demonstrated that Epl/Eth is equally relevant as the electron energy distribution function for plasma‐chemical activation reactions.

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“…For the latter applications, hexamethyldisiloxane (HMDSO) has frequently been employed as a precursor (“monomer”) to investigate the deposition process (“plasma polymerization”) and film properties, respectively. [ 2–17 ]…”

Section: Introductionmentioning

confidence: 99%

Evidence of ionic film deposition from single‐filament dielectric barrier discharges in Ar–HMDSO mixtures

Bröcker

Perlick

Klages

2020

Plasma Processes & Polymers

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The short residence time of Ar-HMDSO (Ar-hexamethyldisiloxane) gas mixtures rapidly flowing across atmospheric-pressure, glow-type, single-filament dielectric barrier discharges is utilized to accomplish thin-film deposition via a purely ionic route. A comparison of thin-film volumes obtained from profilometry, on the one hand, and from the transferred charge, on the other hand, enables to evaluate the mass of the ions contributing to the film growth. For HMDSO fractions at the lower end of the studied range of molar fractions, 50 ppm, pentamethyldisiloxanyl cations (Me 3 SiOSiMe 2 + , PMDS +), generated from the monomer via Penning ionization by Ar(1s) species, are mainly responsible for film formation. For HMDSO fractions growing beyond 1,000 ppm, ionic oligomerization processes by reactions of PMDS + with HMDSO molecules result in a 2.5-fold increase of the average deposited ion mass.

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Large‐area atmospheric pressure dielectric barrier discharges in Ar–HMDSO mixtures: Experiments and fluid modelling

Cited by 19 publications

References 48 publications

Modeling of Atmospheric-Pressure Dielectric Barrier Discharges in Argon with Small Admixtures of Tetramethylsilane

Modeling of Atmospheric-Pressure Dielectric Barrier Discharges in Argon with Small Admixtures of Tetramethylsilane

Plasma polymerization of hexamethyldisiloxane: Revisited

Evidence of ionic film deposition from single‐filament dielectric barrier discharges in Ar–HMDSO mixtures

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