Electron and ion reactions with hexamethyldisiloxane and pentamethyldisiloxane

Carles, Sophie; Garrec, Jean-Luc Le; Mitchell, James B.

doi:10.1063/1.2774984

Cited by 20 publications

(24 citation statements)

References 33 publications

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“…In favour of a simplified ion kinetics, it is assumed that this ion–molecule reaction proceeds according to

{A r}^{prefix+} + {((), {C H}_{3})}_{3} SiOSi {((), {C H}_{3})}_{3} \overset{k_{normalH 3}}{\to} {((), {C H}_{3})}_{3} {SiOSi}^{prefix+} {((), {C H}_{3})}_{2} + {C H}_{3} + A r,

where, again, the pentamethyldisiloxanyl ion and methyl radical are generated. The rate coefficient k H3 of the reaction is 2.0 × 10 −9 cm 3 /s . The energetically preferred

{A r}_{2}^{prefix+}

–HMDSO reaction also leads to the generation of the pentamethyldisiloxanyl ion and a methyl radical and reads as

{A r}_{2}^{prefix+} + {((), {C H}_{3})}_{3} SiOSi {((), {C H}_{3})}_{3} \overset{k_{normalH 4}}{\to} {((), {C H}_{3})}_{3} {SiOSi}^{prefix+} {((), {C H}_{3})}_{2} + {C H}_{3} + 2 A r .

…”

Section: Description Of the Modelmentioning

confidence: 99%

“…The total rate coefficient k H2 = k H2a + k H2b of this reaction at a gas temperature T g = 300 K is k H2 = 3.6 × 10 −6 (T e /300 K) −0.5 cm 3 /s, [24] where the dependence on the electron temperature T e = 2u e /(3k B ) with the Boltzmann constant k B is approximated according to Bardsley and Biondi. [25] Furthermore, collision processes of HMDSO with the atomic and molecular argon ions are involved.…”

Section: Reaction Kinetics Modelmentioning

confidence: 99%

“…The rate coefficient k H3 of the reaction (13) is 2.0 × 10 −9 cm 3 /s. [24] The energetically preferred Ar + 2 -HMDSO reaction also leads to the generation of the pentamethyldisiloxanyl ion and a methyl radical and reads as…”

Section: Reaction Kinetics Modelmentioning

confidence: 99%

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Impact of hexamethyldisiloxane admixtures on the discharge characteristics of a dielectric barrier discharge in argon for thin film deposition

Loffhagen

Becker

Czerny

et al. 2017

Contributions to Plasma Physics

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Atmospheric‐pressure dielectric barrier discharges (DBDs) in argon with admixtures of small amounts of hexamethyldisiloxane (HMDSO) have been analysed by means of numerical modelling. A time‐dependent, spatially one‐dimensional fluid‐Poisson model has been used, which takes into account the spatial variation of the discharge plasma between the plane‐parallel dielectrics covering the electrodes. Main features of the model, including the reaction kinetics for HMDSO, are given. Good agreement with related experimental studies of the ignition voltage for HMDSO amounts of up to 200 ppm and the temporal course of the discharge current for conditions typical of deposition experiments is obtained by the model calculations when assuming that 30% of the reactions of HMDSO with excited argon atoms, with a rate coefficient of 5.0 × 10−10 cm3/s, lead to the production of electrons due to Penning ionization. The modelling results for constant frequency f = 86.2 kHz and applied voltage Ua = 4 kV show that the electrical energy dissipated in the DBD decreases with an increasing amount of HMDSO and enable the determination of the energy absorbed per HMDSO molecule on the basis of their energy balance. The analysis of the plasma–chemical processes also makes clear that collision processes of HMDSO with excited argon atoms and molecules leading to neutral reaction products are essential for the formation of thin polymer films.

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“…In favour of a simplified ion kinetics, it is assumed that this ion–molecule reaction proceeds according to

{A r}^{prefix+} + {((), {C H}_{3})}_{3} SiOSi {((), {C H}_{3})}_{3} \overset{k_{normalH 3}}{\to} {((), {C H}_{3})}_{3} {SiOSi}^{prefix+} {((), {C H}_{3})}_{2} + {C H}_{3} + A r,

where, again, the pentamethyldisiloxanyl ion and methyl radical are generated. The rate coefficient k H3 of the reaction is 2.0 × 10 −9 cm 3 /s . The energetically preferred

{A r}_{2}^{prefix+}

–HMDSO reaction also leads to the generation of the pentamethyldisiloxanyl ion and a methyl radical and reads as

{A r}_{2}^{prefix+} + {((), {C H}_{3})}_{3} SiOSi {((), {C H}_{3})}_{3} \overset{k_{normalH 4}}{\to} {((), {C H}_{3})}_{3} {SiOSi}^{prefix+} {((), {C H}_{3})}_{2} + {C H}_{3} + 2 A r .

…”

Section: Description Of the Modelmentioning

confidence: 99%

Section: Reaction Kinetics Modelmentioning

confidence: 99%

See 1 more Smart Citation

Impact of hexamethyldisiloxane admixtures on the discharge characteristics of a dielectric barrier discharge in argon for thin film deposition

Loffhagen

Becker

Czerny

et al. 2017

Contributions to Plasma Physics

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“…The assumption made implies that the interactions of HMDSO with the group of electrons belonging to the low part of the electron energy distribution function are predominant. Besides, it has been reported 22,38 that electron attachment is not observed in pure HMDSO or in HMDSO-Ar mixtures. Our attempts to record negative ions in the HMDSO-Ar discharge also failed.…”

Section: Consistent Description Of the Observed Processes -Attemptmentioning

confidence: 99%

Influence of the temporal variations of plasma composition on the cyclic formation of dust in hexamethyldisiloxane-argon radiofrequency discharges: Analysis by time-resolved mass spectrometry

Despax

Caquineau

2016

AIP Advances

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Cyclic formation of dust nanoparticles in hexamethyldisiloxane (HMDSO, Si2O(CH3)6)-argon RF discharge with pulsed injection of HMDSO was studied using time-resolved mass spectrometry (MS) and optical emission spectroscopy (OES). A large amount of C2H2, considered as promoter of dust nucleation in hydrocarbon plasmas, was found as a by-product of HMDSO fragmentation. Although no negative ions were detected the presence of C2H2 in the HMDSO-Ar discharge supports the hypothesis of a dust growth mechanism based on negative ions being trapped in the plasma. It was found that at the beginning of each cycle of dust formation during α–γ′ transition, the discharge sustaining process is accompanied by a strong consumption of the HMDSO main by-products: HMDSO-15, CH4 and C2H2. At the end of the cycle, corresponding to the progressive disappearance of dust, the discharge switches back to its initial conditions. The beginning of the inverse transition, i.e. γ′–α, is most likely correlated to the growing void in the dust cloud and dust disappearance. In presence of dust nanoparticles, Ar+ and ArH+ dominate the ion population and consequently the discharge maintenance. When the dust particles gradually disappear, the discharge is rather controlled by Si2O(CH3)5+ ions. Moreover, the increased amount of such heavy ions reveals clearly their important income in the dust repelling process due to the drag force on the large sized dust even at short time scale during the injection time of HMDSO. Atomic-H production increases during the transition from dusty plasma to HMDSO-rich plasma with no dust and its role is associated to a delay in the dust nucleation stage.

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“…Various experimental investigations have been reported in the literature [9,[15][16][17] to evaluate the reactions of HMDSO with active particles and subsequent reactions of the precursor fragments. In addition, the reactions of argon ions with the precursor have been identified as primary processes [17,20,21]. Subsequent reactions of the fragments are reported in [18].…”

Section: Model Descriptionmentioning

confidence: 99%

Study of thin Film Formation From Silicon‐Containing Precursors Produced by an RF Non‐Thermal Plasma Jet at Atmospheric Pressure

Schäfer

Foest

Sigeneger

et al. 2012

Contrib. Plasma Phys.

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The deposition of thin silicon-organic films by atmospheric pressure PECVD using an RF-excited plasma jet has been investigated experimentally and theoretically. Static deposition experiments have been performed on flat polymer and glass samples using the silicon containing molecules HMDSO, OMCTS and silane. The experiments are classified with respect to power, flow rate, operating conditions and deposition rate. The deposited films have been analysed using profilometry and Fourier transform infrared spectroscopy. It is found that electric power and gas flow stability determine distinctive areas in the operating diagram characterized by the deposition rate, profile shape and the chemical properties of the film depending on introduced precursors. The highest O/Si ratio (close to two) is found for laminar flow regimes. Here, the films are characterized by a low carbon content, too. The experimental findings for different flow conditions are discussed in relation to results of a two-dimensional axisymmetric fluid model. The model predicts the interaction of gas heating and flow, the plasma generation in the active volume, the transport of active plasma particles into the effluent and the generation and transport of precursor fragments towards the substrate surface. A remarkable influence of the gas flow on the plasma kinetics is observed only with respect to the density of molecular argon ions, which are transported together with electrons into the effluent. The calculated flux of precursor fragments onto the substrate surface agrees qualitatively with measured profiles of the film thickness.

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Electron and ion reactions with hexamethyldisiloxane and pentamethyldisiloxane

Cited by 20 publications

References 33 publications

Impact of hexamethyldisiloxane admixtures on the discharge characteristics of a dielectric barrier discharge in argon for thin film deposition

Impact of hexamethyldisiloxane admixtures on the discharge characteristics of a dielectric barrier discharge in argon for thin film deposition

Influence of the temporal variations of plasma composition on the cyclic formation of dust in hexamethyldisiloxane-argon radiofrequency discharges: Analysis by time-resolved mass spectrometry

Study of thin Film Formation From Silicon‐Containing Precursors Produced by an RF Non‐Thermal Plasma Jet at Atmospheric Pressure

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