Dominance of Silylene Chemistry in the Decomposition of Monomethylsilane in the Presence of a Heated Metal Filament

Toukabri, R.; Shi, Yujun

doi:10.1021/jp502795u

Cited by 11 publications

(11 citation statements)

References 48 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…On the other hand, homolytic reactions prevail over molecular eliminations for the initial radical intermediates and the stable molecules. Previous studies − suggested that homolytic reactions were more important than molecular eliminations in silenes/silylenes in the HMDS pyrolysis, while this study indicated that both homolytic reactions and molecular eliminations were important.…”

Section: Discussionmentioning

confidence: 41%

“…The radical reactions are common in thermal decomposition processes. The competition between the radical reactions and the silene/silylene reactions has been discussed in a series of studies on thermal decomposition of methyl-substituted silanes in the hot wire CVD process. − It has been demonstrated that the radical reactions take over the silene/silylene reactions gradually with increasing number of methyl substitutions. On the other hand, the silene/silylene reactions become more important with the increase of the number of Si–H bonds.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Mechanistic Study of Thermal Decomposition of Hexamethyldisilane by Flash Pyrolysis Vacuum Ultraviolet Photoionization Time-of-Flight Mass Spectrometry and Density Functional Theory

et al. 2019

View full text Add to dashboard Cite

Thermal decomposition of hexamethyldisilane (HMDS) was studied from room temperature to 1310 K using flash pyrolysis vacuum ultraviolet single-photon ionization time-of-flight mass spectrometry (VUV-SPI-TOFMS). Decomposition pathways of HMDS and initial reaction intermediates were also investigated using density functional theory (DFT) at the B3LYP/6-311++G(d,p) level. Unimolecular decomposition reactions of HMDS involving Si–Si and Si–C bond cleavage, as well as decomposition producing Me4Si and :SiMe2 via a three-centered elimination, were determined as the initiation reactions. Me3SiSi(Me)2 •, Me4Si, Me3Si•, and :SiMe2 were major products of the initiation reactions. These initial products were apt to decompose by homolytic reactions. Me2SiCH2, :SiMe2, and other silene/silylene intermediates preferred decomposing through molecular eliminations. Both homolytic and molecular elimination reactions are important in the pyrolysis of HMDS.

show abstract

Section: Discussionmentioning

confidence: 41%

Section: Introductionmentioning

confidence: 99%

Mechanistic Study of Thermal Decomposition of Hexamethyldisilane by Flash Pyrolysis Vacuum Ultraviolet Photoionization Time-of-Flight Mass Spectrometry and Density Functional Theory

et al. 2019

View full text Add to dashboard Cite

show abstract

“…The peaks at m/z 66, 68, 70, 78, 80, 82, and 84 originate from the secondary reaction products of BTD decomposition. 27,40 When compared to the filament-on mass spectra of DSCB in Figure 3, all of the high-mass-product peaks from DSCB including the main ones at m/z 102, 118, 132, and 174 have been significantly suppressed, to an extent that is greater than the effect of BTD addition on the DSCB decomposition efficiency. At the same time, new peaks at m/z 98, 112, and 140 have appeared.…”

Section: ■ Results and Discussionmentioning

confidence: 95%

Promotion of Exocyclic Bond Cleavages in the Decomposition of 1,3-Disilacyclobutane in the Presence of a Metal Filament

Badran

Shi

2015

J. Phys. Chem. A

Self Cite

View full text Add to dashboard Cite

The primary decomposition of 1,3-disilacyclobutane (DSCB) on a tungsten filament and its secondary gas-phase reactions in a hot-wire chemical vapor deposition (CVD) reactor have been studied using laser ionization mass spectrometry. Under the collision-free conditions, DSCB decomposes on the W filament to produce H2 molecules with an activation energy of 43.6 ± 4.1 kJ·mol(-1). With the help of the isotope labeling and chemical trapping methods, the mechanistic details in the secondary gas-phase reactions important in the hot-wire CVD reactor setup have been examined. The dominant pathway has been demonstrated to be the insertion of the cyclic 1,3-disilacyclobut-1-ylidene, generated by exocyclic Si-H bond rupture, into the Si-H bond in DSCB to form 1,1'-bis(1,3-disilacyclobutane) (174 amu). The successful trapping of 1,3-disilacyclobut-1-ylidene by both 1,3-butadiene and trimethylsilane provides compelling evidence for the existence of this cyclic silylene species in the hot-wire CVD reactor with DSCB. Other reactions operating in the reactor include the DSCB cycloreversion to form silene and the ring opening of DSCB via 1,2-H shift to produce silene/methylsilylene and 1-methylsilene/silylene. The introduction of an additional Si atom in the four-membered ring monosilacyclobutane molecule has caused two major changes in the reaction chemistry assumed by DSCB: (1) The endocyclic cycloreversion reactions that dominate in the decomposition of monosilacyclobutane molecules only play a much less important role in the dissociation of DSCB; and (2) the exocyclic bond cleavages are promoted in DSCB due to the ring stabilization caused by the introduction of one additional Si atom.

show abstract

“…For MMS, a 4% mixture was used instead of a 1% MMS−He sample due to the fact that the intensities of the peaks were extremely weak when the 1% mixture was used. From our previous study on the gasphase chemistry of MMS, 32 it was found that the major products were 1,2-dimethyldisilane (DMDS) (m/z 90) and 1,3-disilacyclobutane (DSCB) (m/z 88). These products were found to be formed from methylsilylene insertion and methylsilylene dimerization reactions, respectively.…”

Section: Effect Of Source Gas Pressure On Mms Gas-phase Chemistrymentioning

confidence: 99%

“…The lack of hydrocarbon molecules with increasing pressure of MMS is probably due to the fact that free radicals do not participate in the gas-phase chemistry when using MMS, despite the fact that free radicals were detected from the study of the primary decomposition of MMS on the tantalum filament. 32,33 To support the conclusion that the dominant chemistry with MMS is not affected during secondary gas-phase reactions due to the absence of small hydrocarbons produced, experiments of MMS with the addition of ethene were conducted. These experiments will give us insights into the effect of the ethene presence on MMS chemistry if it was produced under our experimental conditions.…”

Section: Effect Of Source Gas Pressure On Mms Gas-phase Chemistrymentioning

confidence: 99%

Effect of pressure on the gas-phase chemistry when using monomethylsilane and dimethylsilane in hot-wire chemical vapor deposition

ToukabriRim

ShiYujun

2015

Can. J. Chem.

View full text Add to dashboard Cite

The effect of source gas pressure on the gas-phase reaction chemistry of dimethylsilane (DMS) and monomethylsilane (MMS) in the hot-wire chemical vapor deposition process has been studied by examining the secondary gas-phase reaction products in a reactor using a soft laser ionization source coupled with mass spectrometry. For DMS, the increase in sample pressure has resulted in the formation of small hydrocarbons, including ethene, acetylene, propene, and propyne. This leads to a switch from silylene dominant chemistry to a free radical dominant one with the pressure increase at low filament temperatures of 1200 and 1300°C. At the lower pressure of 0.12 Torr, the formation of 1,1,2,2-tetramethyldisilane by dimethylsilylene insertion reaction into the Si-H bond in DMS is favored over trimethylsilane produced from a free radical recombination reaction for a short reaction time. However, when the pressure is increased by 10 times, the gas-phase chemistry becomes dominated by the formation of trimethylsilane. We have demonstrated that trapping of the corresponding active intermediates by the small hydrocarbons produced in situ is responsible for the observed switch. In the study with MMS, the gas-phase chemistry is dominated by the formation of 1,2-dimethyldisilane and 1,3-disilacyclobutane at both pressures of 0.48 and 1.2 Torr. Unlike DMS, the gas-phase reaction chemistry with MMS does not involve free radicals, which are the precursors to produce small hydrocarbons. The absence of small hydrocarbons formed in situ with MMS explains the preservation in chemistry upon the increase in pressure when MMS is used as a source gas.Résumé : On a étudié dans un réacteur l'effet de la pression du gaz source sur la réaction en phase gazeuse du diméthylsilane (DMS) et du monométhylsilane (MMS) par un procédé de dépôt chimique en phase vapeur à fil chaud, en étudiant les produits secondaires dans la phase gazeuse au moyen d'un laser de faible puissance utilisé comme source d'ionisation et couplé avec un spectromètre de masse. Dans le cas du DMS, l'augmentation de la pression de l'échantillon a entraîné la formation d'hydrocarbures légers, notamment l'éthène, l'acétylène, le propène et le propyne. On en déduit que l'environnement chimique où la formation du silylène prédomine passe à un environnement chimique où la formation de radicaux libres prédomine dans lequel une augmentation de la pression s'est produite à de basses températures du filament (1200 et 1300°C). À la pression la plus faible (0,12 Torr), pendant un temps de réaction court, la formation du 1,1,2,2-tétraméthyldisilane par réaction d'insertion du diméthylsilylène dans le lien Si−H du DMS a été favorisée, par rapport à la formation du triméthylsilane issu de la réaction de recombinaison de radicaux libres. Toutefois, lorsque la pression était décuplée, la formation en phase gazeuse du triméthylsi-lane était prédominante. Nous avons démontré que le piégeage des intermédiaires réactifs par les hydrocarbures légers produits in situ est responsable du changement obse...

show abstract

Dominance of Silylene Chemistry in the Decomposition of Monomethylsilane in the Presence of a Heated Metal Filament

Cited by 11 publications

References 48 publications

Mechanistic Study of Thermal Decomposition of Hexamethyldisilane by Flash Pyrolysis Vacuum Ultraviolet Photoionization Time-of-Flight Mass Spectrometry and Density Functional Theory

Mechanistic Study of Thermal Decomposition of Hexamethyldisilane by Flash Pyrolysis Vacuum Ultraviolet Photoionization Time-of-Flight Mass Spectrometry and Density Functional Theory

Promotion of Exocyclic Bond Cleavages in the Decomposition of 1,3-Disilacyclobutane in the Presence of a Metal Filament

Effect of pressure on the gas-phase chemistry when using monomethylsilane and dimethylsilane in hot-wire chemical vapor deposition

Contact Info

Product

Resources

About