Chemical composition and bond structure of aerosol particles of amorphous hydrogenated silicon forming from thermal decomposition of silane

Onischuk, A. A.; Strunin, V.P.; Samoilova, Rimma I.; Носов, А. В.; Ushakova, M.A.; Panfilov, V. N.

doi:10.1016/s0021-8502(97)00026-8

Cited by 29 publications

(40 citation statements)

References 45 publications

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“…The structure of these clusters suggests that continued growth will lead to particles that have compact structures made up of five-and six-membered rings, with hydrogen present only at the surface of the clusters. This is consistent with the relatively low degree of hydrogenation of the silicon particles studies by Onischuk et al 40 It would be useful, for purposes of modeling aerosol dynamics in real reactors, to have a simpler and computationally less expensive means of computing the nucleation rate than is provided by a large, detailed reaction mechanism. From the results presented above, it is clear that there are some regimes where simple, approximate expressions for the nucleation rate can be derived.…”

Section: Kinetic Simulations and Reaction-path Analysissupporting

confidence: 83%

Thermochemistry and Kinetics of Silicon Hydride Cluster Formation during Thermal Decomposition of Silane

1998

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Product contamination by particles nucleated within the processing environment often limits the deposition rate during chemical vapor deposition processes. A fundamental understanding of how these particles nucleate could allow higher growth rates while minimizing particle contamination. Here we present an extensive chemical kinetic mechanism for silicon hydride cluster formation during silane pyrolysis. This mechanism includes detailed chemical information about the relative stability and reactivity of different possible silicon hydride clusters. It provides a means of calculating a particle nucleation rate that can be used as the nucleation source term in aerosol dynamics models that predict particle formation, growth, and transport. A group additivity method was developed to estimate thermochemical properties of the silicon hydride clusters. Reactivity rules for the silicon hydride clusters were proposed based on the group additivity estimates for the reaction thermochemistry and the analogous reactions of smaller silicon hydrides. These rules were used to generate a reaction mechanism consisting of reversible reactions among silicon hydrides containing up to 10 silicon atoms and irreversible formation of silicon hydrides containing 11-20 silicon atoms. The resulting mechanism was used in kinetic simulations of clustering during silane pyrolysis in the absence of any surface reactions. Results of those simulations are presented, along with reaction path analyses in which key reaction paths and rate-limiting steps are identified and discussed.

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Section: Kinetic Simulations and Reaction-path Analysissupporting

confidence: 83%

Thermochemistry and Kinetics of Silicon Hydride Cluster Formation during Thermal Decomposition of Silane

1998

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“…2000 cm (the hydrogen atoms of these groups are close enough to each other and give broad NMR line due to homonuclear dipole interaction) [21].…”

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confidence: 99%

Studying of silane thermal decomposition mechanism

Onischuk

Strunin

Ushakova

et al. 1998

Int. J. Chem. Kinet.

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The mechanism of silane thermal decomposition is investigated in a flow reactor. The time dependencies of silane consumption and disilane formation were compared with those parameters of solid product (aerosol particles) such as concentration, total hydrogen content in solid product, and fraction of hydrogen contained in solid product as polyhydride groups (SiH 2 ) n . Silane loss and gaseous product formation were analyzed using a mass spectrometer. The hydrogen content in solid product was analyzed by the methods of IR-spectroscopy and hydrogen evolution. Based on a simple kinetic scheme we qualitatively explained the experimental dependencies of silane conversion and disilane formation, the effective activation energy of the decomposition process, and the amount of polyhydride groups in the solid product on reaction time and initial silane concentration.

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“…The most natural is to start with the analysis of the solid product of decomposition, generated in the form of aerosol particles. These particles consist of amorphous hydrogenated silicon [43][44][45]. The mechanism of particle growth is similar to the wall deposit growth at the same conditions and the active centers present on the surface of particles are the same as these centers on the surface of wall deposit.…”

Section: Introductionmentioning

confidence: 88%

“…The methods provided a major breakthrough in the present understanding of the mechanism of heterogeneous reactions on ideal surfaces. However, the problem is that the morphology, composition of these ideal surfaces and the nature of their active centers differ very much from those of amorphous hydrogenated silicon resulting from heterogeneous/homogeneous silane decomposition [43].…”

Section: Introductionmentioning

confidence: 99%

“…Until recently there was a lack of reference data on the aerosol particle reactivity and the nature, concentration and localization of active centers in them. However, some useful information can be found in the studies of a-Si:H films (see references further in Sections 4 and 5), since aerosol particles have the same structural groups and the same defects as a-Si:H films [43][44][45]. Nevertheless, aerosol particles differ noticeably from a-Si:H films.…”

Section: Introductionmentioning

confidence: 99%

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EPR investigation of a-Si:H aerosol particles formed under silane thermal decomposition

et al. 1998

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The dangling bond defects were investigated in a-Si:H particles formed under silane thermal decomposition in flow reactor. EPR together with hydrogen evolution method were used. The experimental results allowed us to conclude that there are two kinds of dangling bond defects in aSi:H aerosol particles. The defects of the first kind are localized on the surface of interconnected microvoids and microchannels (surface dangling bonds) and those of the second kind are embedded in amorphous silicon network (volume dangling bonds). The thermal equilibration of dangling bonds and temperature dependence of equilibrium dangling bond concentration were investigated. It was found that at temperatures >400 K the dangling bond concentration N reversibly depends on sample temperature. The volume dangling bond concentration increases with temperature increasing (the effective activation energy of dangling bond formation U> 0), and the surface dangling bond concentration decreases with temperature increasing (U < 0). It has been found that EPR line is considerably asymmetric for samples with high hydrogen content and for low hydrogen content the EPR line is weakly asymmetric. A conclusion was drawn that the asymmetry degree depends on amorphous silicon lattice distortions. This conclusion has been confirmed by EPR spectra simulations.

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Chemical composition and bond structure of aerosol particles of amorphous hydrogenated silicon forming from thermal decomposition of silane

Cited by 29 publications

References 45 publications

Thermochemistry and Kinetics of Silicon Hydride Cluster Formation during Thermal Decomposition of Silane

Thermochemistry and Kinetics of Silicon Hydride Cluster Formation during Thermal Decomposition of Silane

Studying of silane thermal decomposition mechanism

EPR investigation of a-Si:H aerosol particles formed under silane thermal decomposition

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