High-Accuracy Thermochemistry of Atmospherically Important Fluorinated and Chlorinated Methane Derivatives

Csontos, József; Rolik, Zoltán; Das, Sanghamitra; Kállay, Mihály

doi:10.1021/jp105268m

Cited by 91 publications

(133 citation statements)

References 86 publications

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“…On the other hand, good agreement is observed between our calculations and those derived from highly accurate computational methods reported by Feller et al, 26 Feller and Dixon, 28 Vasiliu et al, 27 Karton et al, 30 Tajti et al, 31 Grant and Dixon 32 and Klopper et al 29 It is apparent that large dis- 20 on the other hand, are much more agreeable to the theory.…”

Section: Resultssupporting

confidence: 86%

Thermochemical Properties of Halides and Halohydrides of Silicon and Carbon

Sukkaew

Ojamäe

Kordina

et al. 2015

ECS J. Solid State Sci. Technol.

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Atomization energies, enthalpies of formation, entropies as well as heat capacities of the SiH n X m and CH n X m systems, with X being F, Cl and Br, have been studied using quantum chemical calculations. The Gaussian-4 theory (G4) and Weizman-1 theory as modified by Barnes et al. 2009 (W1RO) have been applied in the calculations of the electronic, zero point and thermal energies. The effects of low-lying electronically excited states due to spin orbit coupling were included for all atoms and diatomic species by mean of the electronic partition functions derived from the experimental or computational energy splittings. The atomization energies, enthalpies of formation, entropies and heat capacities derived from both methods were observed to be reliable. The thermochemical properties in the temperature range of 298-2500 K are provided in the form of 7-coefficient NASA polynomials. © The Author Silicon carbide (SiC) is an attractive material for power electronics. The characteristics of having wide bandgap, high thermal conductivity, high blocking voltage and switching frequencies have made it superior for applications at high temperatures, frequencies and voltages.1 To this end, it is vital to achieve high material quality as well as manufacturing process reliability and efficiency. In chemical vapor deposition (CVD), a widely used fabrication method for SiC layers, this means suppressing the formation of Si clusters and parasitic depositions which are known to introduce defects and degrade the growing layers, along with shortening the lifetime of reactor components. 2-4Halogenated gases have been utilized to reduce the cluster formation by breaking the Si-Si bonds in the clusters and forming the stronger Si-halogen bonds and consequently introduce a new parameter into the process, namely the halogen/Si ratio. This ratio has shown impacts on not only the cluster formation and parasitic growth, but also on the growth rates as well as defect formations. 4,5 In complex processes such as CVD, computational modeling has become essential in research as well as process development and design. Modeling accuracy and correctness depend crucially on the quality of the kinetics and thermochemistry data input. Thermochemistry data of some halides and halohydrides of Si and C are provided in databases, 6-8 review, 9 as well as experimental [10][11][12][13][14][15][16] and theoretical studies.17-32 Nevertheless, inconsistency derived from various means of achieving data along with many data mismatches have rendered it far from complete. Here we present thermochemical properties from quantum chemical calculations of a complete set of halides and halohydrides of Si and C, namely SiX n H m and CX n H m with X = F, Cl and Br, and n+m ≤4, covering the temperature range of 298-2500 K. The study range accommodates applications such as CVD process, surface etching of semiconductors, combustion, as well as fundamental studies. The quantum chemistry composite methods of Gaussian-4 theory (G4) 33 are utilized and compared to the Weizmann...

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Section: Resultssupporting

confidence: 86%

Thermochemical Properties of Halides and Halohydrides of Silicon and Carbon

Sukkaew

Ojamäe

Kordina

et al. 2015

ECS J. Solid State Sci. Technol.

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“…For this to be reliable it is important to include all important species including the short-lived radicals where thermodynamic properties are usually not available in the commonly used databases. Quantum chemical calculations such as ab initio, DFT and their composites are great tools to derive such properties, especially for short-lived species which are hard to measure experimentally [55][56][57] .…”

Section: Present Status Of Sic-cvd Process Modelingmentioning

confidence: 99%

A Quantum Chemical Exploration of SiC Chemical Vapor Deposition

Sukkaew¹

2017

Linköping Studies in Science and Technology. Dissertations

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SiC is a wide bandgap semiconductor with many attractive properties. It has attracted particular attentions in the areas of power and sensor devices as well as biomedical and biosensor applications. This is owing to its properties such as large bandgap, high breakdown electric field, high thermal conductivities and chemically robustness. Typically, SiC homoepitaxial layers are grown using the chemical vapor deposition (CVD) technique. Experimental studies of SiC CVD have been limited to post-process measuring of the layer rather than in situ measurements. In most cases, the observations are presented in terms of input conditions rather than in terms of the unknown growth condition near the surface. This makes it difficult to really understand the underlying mechanism of what causes the features observed experimentally. With help of computational methods such as computational fluid dynamic (CFD) we can now explore various variables that are usually not possible to measure. CFD modeling of SiC CVD, however, requires inputs such as thermochemical properties and chemical reactions, which in many cases are not known. In this thesis, we use quantum chemical calculations to provide the missing details complementary to CFD modeling.We first determine the thermochemical properties of the halides and halohydrides of Si and C species, SiHnXm and CHnXm, for X being F, Cl and Br which were shown to be reliable compared to the available experimental and/or theoretical data. In the study of gas-phase kinetics, we combine ab initio methods and DFTs with conventional transition state theory to derive kinetic parameters for gas phase reactions related to Si-H-X species. Lastly, we study surface adsorptions related to SiC-CVD such as adsorptions of small C-H and Si-H-X species, and in the case of C-H adsorption, the study was extended to include subsequent surface reactions where stable surface products may be formed. iv SammanfattningSiC är ett halvledarmaterial med stort bandgap som har många attraktiva egenskaper. Det har fått särskilt mycket uppmärksamhet inom kraftkomponenter och sensorer, men också för tillämpningar inom biomedicin och biosensorer. Detta beror på materialets stora bandgap, förmågan att klara höga elektriska fält, goda värmeledningsförmåga och kemiska stabilitet. Epitaxiska skikt av SiC för kommersiella tillämpningar tillverkas med hjälp av kemisk ångdepo-sition (Chemical Vapor Deposition, CVD). Experimentella studier av SiC CVD begränsas till mätningar som görs i efterhand, snarare än under processens gång. För det mesta görs observationer med utgångspunkt från processens ingångsvärden istället för från de okända tillväxtförhållandena vid ytan. Detta gör det svårt att verkligen förstå de underliggande mekanismerna för de observerade experimentella resultaten. Med hjälp av beräkningsmetoder, såsom computational fluid dynamics (CFD) kan vi utforska olika variabler som vanligtvis inte går att mäta. Dock kräver CFD-modellering av SiC CVD ingångs-data i form av termokemiska egenskaper och kemiska reaktion...

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“…The two approaches are, thus, complementary and can be applied simultaneously to provide sturdier results. For example, experiment can be used to confirm the highly accurate enthalpies of formation derived by Csontos et al [5], for a comprehensive range of neutral halogenated methanes, which were inspired by the W3 and HEAT protocols [13,14].…”

Section: ð4:1þmentioning

confidence: 99%

“…3) were used to determine the neutral and ion energetics, which were utilised along with previously reported energies [5] in the construction of the thermochemical network shown in Sect. 4.3.4.…”

Section: Introductionmentioning

confidence: 99%

“…Quantum chemical calculations on small molecules can yield thermochemical values with a few kJ mol -1 uncertainties or better, often outperforming experimental results [5][6][7][8][9]. Recent threshold photoelectron photoion coincidence (TPEPICO) experiments, in which both the photon and the photoelectron energies are known to within 1-2 meV (0.1-0.2 kJ mol -1 ), [1,[10][11][12] are capable of measuring dissociative photoionization onset energies in small to medium sized molecules with such levels of accuracy.…”

Section: Introductionmentioning

confidence: 99%

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