Thermodynamics of silicon nitride. I. Standard molar enthalpies of formation ΔfHmoat the temperature 298.15 K of α-Si3N4and β-Si3N4

This work presents an in-depth investigation of the properties of complexes composed of hydrogen, silicon or oxygen with carbon, which are major unintentional impurities in undoped GaN. This manuscript is a complement to our previous work on carbon-carbon and carbon-vacancy complexes. We have employed a first-principles method using Heyd-Scuseria-Ernzerhof hybrid functionals within the framework of generalized Kohn-Sham density functional theory. Two H-C, four Si-C and five O-C complexes in different charge states have been considered. After full geometry relaxations, formation energies, binding energies and both thermal and optical transition levels were obtained. The calculated energy levels have been systematically compared with the experimentally observed carbon related trap levels. Furthermore, we computed vibrational frequencies for selected defect complexes and defect concentrations were estimated in the low, mid and high carbon doping scenarios considering two different cases where electrically active defects: (a) only carbon and vacancies and (b) not only carbon and vacancies but also hydrogen, silicon and oxygen. We confirmed that CN is a dominant acceptor in GaN. In addition to it, substantial amount of SiGa − CN complex exists in a neutral form. This complex is a likely candidate for unknown form of carbon observed in undoped n-type GaN.PACS numbers: 61.72. 61.72.uj, 71.15.Mb, 71.55.Eq

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“…Our calculated value for ∆H f (Si 3 N 4 ) is −8.52 eV, which is in good agreement with the experimental value (−8.58 eV) 33 . With the Eq.…”

Section: Methodssupporting

confidence: 91%

“…where E(Si), E(N 2 ) and ∆H f (Si 3 N 4 ) are the energies of bulk silicon and nitrogen molecule and the formation enthalpy of the β-Si 3 N 4 , respectively. Our calculated value for ∆H f (Si 3 N 4 ) is −8.52 eV, which is in good agreement with the experimental value (−8.58 eV) 33 . With the Eq.…”

Section: Methodssupporting

confidence: 91%

A first-principles study of carbon-related energy levels in GaN. II. Complexes formed by carbon and hydrogen, silicon or oxygen

Matsubara

Bellotti

2017

Journal of Applied Physics

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“…where −9374.4 J · g −1 and −37956 J · g −1 are, respectively, the standard massic energies of combustion of W (21) and S (22) in F 2 . Corrections for VF 3 residues were based upon the unpublished results of Johnson (23) who determined c u o = −2250.2 J · g −1 for the reaction:…”

Section: Resultsmentioning

confidence: 99%

Thermodynamic properties of vanadium silicides. I. Standard molar enthalpy of formationΔfHmoof vanadium disilicide (VSi2) at the temperature 298.15 K

O’Hare

Watling

Hope

1999

The Journal of Chemical Thermodynamics

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“…Calculations were carried out by use of the Gemini II software together with the Coach database [24]. The database includes data related to Si 2 N 2 O and Si 3 N 4 but does not make any distinction between the alpha and beta allotropic forms of the latter species, which are, probably very close to each other: the standard molar enthalpies of formation of the two allotropic forms are not discernible except for the uncertainties of the measurements [25]. The calculation shows that, when using an initial elemental composition corresponding to the stoichiometry of balance Equation (1) (N = 4, Si = 4, O = 2), Si 2 N 2 O is the only solid species formed in the range of temperature 20 to 1800 • C under a total pressure of N 2 in the range 1 to 3 MPa.…”

Section: Phase Formation and Phase Stabilitymentioning

confidence: 99%

Densification of Ceramic Matrix Composite Preforms by Si2N2O Formed by Reaction of Si with SiO2 under High Nitrogen Pressure. Part 1: Materials Synthesis

2021

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Ceramic matrix composites (CMCs) have been designed and developed for extreme operating environments. The aim of the present study is to look for a rapid densification process providing a high level of material performance. The fibrous preform was made of Hi-Nicalon S fibers woven in a 3D interlock weave. The matrix was composed of Si2N2O prepared inside the CMCs by reacting a mixture of Si and SiO2 under high nitrogen pressure (1 to 3 MPa). Silica was either impregnated by slurry or obtained by oxidation of silicon grains inside the preform. The synthesis reaction was initiated by heating the impregnated preform by means of a carbon resistor submitted to Joule effect. Composition, homogeneity and porosity of the formed matrix were studied and interpreted as a function of the experimental parameters (nitrogen pressure, heating rate of the preform) as well as the recorded thermal history of the process. The present results show that the matrix formation is almost completed in less than one minute. Melting of silicon has a major influence on the process. Competition was observed between the formation of Si3N4 and Si2N2O, which could be mainly controlled by the heating rate of the preform and the nitrogen partial pressure.

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Thermodynamics of silicon nitride. I. Standard molar enthalpies of formation ΔfHmoat the temperature 298.15 K of α-Si3N4and β-Si3N4

Cited by 26 publications

References 20 publications

A first-principles study of carbon-related energy levels in GaN. II. Complexes formed by carbon and hydrogen, silicon or oxygen

A first-principles study of carbon-related energy levels in GaN. II. Complexes formed by carbon and hydrogen, silicon or oxygen

Thermodynamic properties of vanadium silicides. I. Standard molar enthalpy of formationΔfHmoof vanadium disilicide (VSi2) at the temperature 298.15 K

Densification of Ceramic Matrix Composite Preforms by Si2N2O Formed by Reaction of Si with SiO2 under High Nitrogen Pressure. Part 1: Materials Synthesis

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