Absolute total and partial electron impact ionization cross sections of hexamethyldisiloxane

Basner, R.; Foest, Rüdiger; Schmidt, Martin; Becker, K.; Deutsch, Hans‐Peter

doi:10.1016/s1387-3806(98)14027-7

Cited by 76 publications

(114 citation statements)

References 23 publications

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“…This result confirms the strong instability of HMDSO molecular ion as already reported by other authors. 21,22 Thus, Si 2 O(CH 3 ) 5 + ion intensity will be considered as an image of the HMDSO concentration in 21 When the gas discharge is ignited (Fig. 4), a strong decrease of Si 2 O(CH 3 ) 5 + (m/z 147 amu) related to the HMDSO decomposition in the plasma is observed on the mass spectrum.…”

Section: A Mass Spectrometry Detection Of Neutral Speciesmentioning

confidence: 99%

“…For energies below the HMDSO ionization energy (8.8 eV), the dissociation of the HMDSO molecule by electron impact is the dominant process. 21,37 As the bonding energy of the Si-O bond (8.31 eV) is almost twice higher than that of the Si-C bond (4.53 eV), the radical dissociation process induces a dominant production of the neutral radicals • CH 3 and Si 2 O(CH 3 ) 5 (HMDSO-15). Therefore, further reactions in the chain will be primarily initiated by these two most abundant reactive species produced in the plasma.…”

Section: Consistent Description Of the Observed Processes -Attemptmentioning

confidence: 99%

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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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Section: A Mass Spectrometry Detection Of Neutral Speciesmentioning

confidence: 99%

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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“…For computational convenience, only closed-shell molecules were considered. Along with references for the experimental cross sections, the molecules are: C 2 Cl 6 28 Tables of MO data used to generate the BEB cross sections are available from the authors upon request. As mentioned above, some vertical ionization energies 29 -36 and double-ionization energies 37 -41 were taken from experimental measurements.…”

Section: Resultsmentioning

confidence: 99%

Performance of binary‐encounter‐Bethe (BEB) theory for electron‐impact ionization cross sections of molecules containing heavy elements (Z > 10)

Scott

Irikura

2005

Surface & Interface Analysis

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The binary-encounter-Bethe (BEB) theory developed by Kim and coworkers has been successful for computing electron-impact ionization cross sections of many molecules. However, some recent publications have stated that BEB theory performs poorly for molecules that contain heavier elements such as chlorine and sulfur. We have found that the BEB calculations in those publications were performed incorrectly. When performed correctly, BEB predictions are as good for heavy-element molecules as for light-element molecules. We recommended recently that an alternative, less-confusing procedure be used for molecules that contain heavier elements. The alternative procedure, based upon effective core potentials (ECPs), does not require explicit kinetic energy corrections. For peak cross sections of a group of 18 molecules, the root-mean-square difference between BEB predictions and experimental values is 13%. Results

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“…The electron-impact ionization cross-section data for TEOS and HMDSO have been measured. (24,45) The ionization potential for organic silicon compounds is found to be relatively low, 7.7 eV for TEOS and 8.8 eV for HMDSO. A relatively complete set of cross-section data for electron-impact reactions, including dissociations, vibrational excitations, and ionizations, is available for TEOS.…”

Section: Gas-phase Chemical Mechanismsmentioning

confidence: 99%

A Global Model of Chemical Vapor Deposition of Silicon Dioxide by Direct-Current Corona Discharges in Dry Air Containing Octamethylcyclotetrasiloxane Vapor

Chen

Davidson

2004

Plasma Chem Plasma Process

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A model of the electron distribution in direct current corona plasmas is combined with a global chemistry model and a two-dimensional transport model to predict the rate of chemical vapor deposition of silicon dioxide on the discharge wire in both positive and negative discharges in dry air containing octamethylcyclotetrasiloxane. The gas-phase chemistry includes reactions to form atomic oxygen (O) and additional global reactions to form gaseous silicon dioxide precursors by the impact reactions of electrons and atomic oxygen with silicone molecules. Surface chemistry is approximated by a single step global reaction from gaseous to solid silicon dioxide. The rate coefficient between atomic oxygen and octamethylcyclotetrasiloxane is estimated from prior experiments to be on the order of 10 −12 cm 3 /molecule-s. The effects of discharge polarity, current, wire radius and air velocity (Peclet number for mass transfer) on the deposition rate are considered. Deposition rates can be minimized by using positive coronas instead of negative coronas for Peclet number less than 18.5. At higher Peclet numbers, the deposition rate is slightly higher in positive corona discharges, but devices used indoors should continue to use the positive corona in order to minimize the production of ozone. The deposition rate in the positive corona is relatively insensitive to air velocity for velocities from 0.044 to 10 m/s −1 . However,it may be minimized by operating the corona with the lowest current that provides adequate performance (e.g., particle charging) and the smallest wire that provides adequate mechanical strength.

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Absolute total and partial electron impact ionization cross sections of hexamethyldisiloxane

Cited by 76 publications

References 23 publications

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

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

Performance of binary‐encounter‐Bethe (BEB) theory for electron‐impact ionization cross sections of molecules containing heavy elements (Z > 10)

A Global Model of Chemical Vapor Deposition of Silicon Dioxide by Direct-Current Corona Discharges in Dry Air Containing Octamethylcyclotetrasiloxane Vapor

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