Theoretical Study of N Incorporation Effect during SiC Oxidation

2013 ◽  
Vol 740-742 ◽  
pp. 455-458 ◽  
Author(s):  
Shigenori Kato ◽  
Kenta Chokawa ◽  
Katsumasa Kamaiya ◽  
Kenji Shiraishi
Keyword(s):  
First Principles ◽  
Theoretical Study ◽  
Oxidation Process ◽  
The Other ◽  
No Oxidation ◽  
First Principles Calculation ◽  
Interface Properties ◽  
Covalent Bonds ◽  
State Generation ◽  
N Incorporation

We investigated the atomistic mechanism of N incorporation during SiC oxidation by the first principles calculation. We found that N atoms play two characteristic roles in NO oxidation of SiC surface. One is that N atoms tend to form three-fold coordinated covalent bonds on a SiC(0001) surface, which assist the termination of surface dangling bonds, leading to improve the interface properties. The other is that N atoms form N-N bond like a double bond. The N2 molecule is desorbed from SiC surface, which do not disturb the oxidation process of SiC surfaces. These results indicate that N incorporation is effective to suppress defect state generation at SiO2/SiC interfaces during SiC oxidation.

scholarly journals Strain Conditions for the Inverse Heusler Type Fully Compensated Spin-Gapless Semiconductor Ti2MnAl: A First-Principles Study

Materials ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2091 ◽  
Author(s):  
Tie Yang ◽  
Liyu Hao ◽  
Rabah Khenata ◽  
Xiaotian Wang
Keyword(s):  
Thermodynamic Properties ◽  
First Principles ◽  
Density Functional ◽  
Theoretical Study ◽  
Debye Model ◽  
Pressure Effects ◽  
First Principles Calculation ◽  
Strain Condition ◽  
Functional Theory ◽  
Future Work

In this work, we systematically studied the structural, electronic, magnetic, mechanical and thermodynamic properties of the fully compensated spin-gapless inverse Heusler Ti2MnAl compound under pressure strain condition by applying the first-principles calculation based on density functional theory and the quasi-harmonic Debye model. The obtained structural, electronic and magnetic behaviors without pressure are well consistent with previous studies. It is found that the spin-gapless characteristic is destroyed at 20 GPa and then restored with further increase in pressure. While, the fully compensated ferromagnetism shows a better resistance against the pressure up to 30 GPa and then becomes to non-magnetism at higher pressure. Tetragonal distortion has also been investigated and it is found the spin-gapless property is only destroyed when c/a is less than 1 at 95% volume. Three independent elastic constants and various moduli have been calculated and they all show increasing tendency with pressure increase. Additionally, the pressure effects on the thermodynamic properties under different temperature have been studied, including the normalized volume, thermal expansion coefficient, heat capacity at constant volume, Grüneisen constant and Debye temperature. Overall, this theoretical study presents a detailed analysis of the physical properties’ variation under strain condition from different aspects on Ti2MnAl and, thus, can provide a helpful reference for the future work and even inspire some new studies and lead to some insight on the application of this material.

First-principles calculation on γ-Fe/La2O3 interface properties and austenite refinement mechanism by La2O3

2021 ◽  
Vol 259 ◽  
pp. 124194
Author(s):  
Xiaoyong Jiao ◽  
Wantang Fu ◽  
Wei Shao ◽  
Xiongwei Zhu ◽  
Yefei Zhou ◽  
...  
Keyword(s):  
First Principles ◽  
First Principles Calculation ◽  
Interface Properties ◽  
Refinement Mechanism

A Theoretical Study of Dislocation Formation at Surfaces in Covalent Materials: Effect of Step Geometry and Reactivity

2005 ◽  
Vol 108-109 ◽  
pp. 193-198
Author(s):  
Sandrine Brochard ◽  
Julien Godet ◽  
Laurent Pizzagalli ◽  
Pierre Beauchamp ◽  
José Soler
Keyword(s):  
First Principles ◽  
Theoretical Study ◽  
Quantitative Agreement ◽  
First Principles Calculation ◽  
Atomistic Simulations ◽  
Near Surface ◽  
Empirical Potential ◽  
Qualitative And Quantitative ◽  
Surface Steps ◽  
Semi Empirical

Atomistic simulations using both semi-empirical potential and first principles calculation have been performed to study the initiation of plasticity near surface steps in silicon. A comparison of both techniques on a prototypic case shows qualitative and quantitative agreement. Then each method has been used to analyze in detail some characteristics of the surface step: the step geometry thanks to semi-empirical potential calculations, and the step reactivity with ab initio techniques.

scholarly journals The Effect of Indium Concentration on the Structure and Properties of Zirconium Based Intermetallics: First-Principles Calculations

2016 ◽  
Vol 2016 ◽  
pp. 1-8
Author(s):  
Fuda Guo ◽  
Junyan Wu ◽  
Shuai Liu ◽  
Yongzhong Zhan
Keyword(s):  
Density Functional Theory ◽  
First Principles ◽  
Density Functional ◽  
Indium Content ◽  
The Other ◽  
First Principles Calculation ◽  
First Principles Calculations ◽  
Structure And Properties ◽  
Functional Theory ◽  
Formation Enthalpies

The phase stability, mechanical, electronic, and thermodynamic properties of In-Zr compounds have been explored using the first-principles calculation based on density functional theory (DFT). The calculated formation enthalpies show that these compounds are all thermodynamically stable. Information on electronic structure indicates that they possess metallic characteristics and there is a common hybridization between In-p and Zr-d states near the Fermi level. Elastic properties have been taken into consideration. The calculated results on the ratio of the bulk to shear modulus (B/G) validate that InZr3has the strongest deformation resistance. The increase of indium content results in the breakout of a linear decrease of the bulk modulus and Young’s modulus. The calculated theoretical hardness ofα-In3Zr is higher than the other In-Zr compounds.

First-Principles Study of Interfacial Reaction Atomic Process at Silicon Oxidation

1997 ◽  
Vol 492 ◽  
Author(s):  
H. Kageshima ◽  
K. Shiraishi
Keyword(s):  
First Principles ◽  
Process Model ◽  
Silicon Oxide ◽  
Oxidation Process ◽  
First Principles Calculation ◽  
Microscopic Approach ◽  
Silicon Oxidation ◽  
Atomic Process ◽  
Plausible Assumption ◽  
Enhanced Diffusion

ABSTRACTA theoretical atomic process model of the interfacial oxidation reaction on a silicon substrate is proposed based on first-principles calculation. In the calculation, H-terminated Si(100) surfaces are used for the first approximation of the silicon-oxide/silicon interfaces. The proposed atomic process model is based on the plausible assumption that the remaining stress in the oxidized region is kept at a minimum and does not break the grown Si-O-Si network when the oxidation proceeds. As a natural consequence, Si atoms are emitted from the interface as the oxidation proceeds to release the stress due to substitution of Si-Si bonds by Si-O-Si bonds. This emission is consistent with well-known experiments of oxidation-induced stacking faults and oxidation-enhanced diffusion. Our model presents a microscopic approach for understanding the silicon oxidation process, whereas the widely accepted Deal-Grove model presents a macroscopic one.

scholarly journals First-Principles Calculation on Initial Stage of Oxidation of Si (110)-(1 × 1) Surface

2011 ◽  
Vol 2011 ◽  
pp. 1-5 ◽  
Author(s):  
Takahiro Nagasawa ◽  
Koji Sueoka
Keyword(s):  
First Principles ◽  
Experimental Results ◽  
The Other ◽  
First Principles Calculation ◽  
Preferential Oxidation ◽  
Coverage Ratio ◽  
Surface Areas ◽  
Initial Stage ◽  
The Stability

The initial stage of oxidation of an Si (110)-(1 × 1) surface was analyzed by using the first-principles calculation. Two calculation cells with different surface areas were prepared. In these cells, O atoms were located at the Si–Si bonds in the first layer (A-bonds) and at the Si–Si bonds between the first and second layers (B-bonds). We found that (i) the most stable site of one O atom was the A-bond, and (ii) an O (A-bond) –Si–O (A-bond) was the most stable for two O atoms with a coverage ratio of while an O (A-bond) –Si–O (B-bond) was the most stable for . The stability of O (A-bond) –Si–Si–O (A-bond) was less than the structures obtained in (ii). The other calculations showed that the unoxidized A-bonds should be left when a coverage ratio of is close to 1. These simulations suggest that the O atoms will form clusters in the initial stage of oxidation, and the preferential oxidation will change from the A-bonds to the B-bonds up to the formation of 1 monolayer (ML) oxide. The results obtained here support the reported experimental results.

Effects of Sulfur Passivation on 6H-SiC(0001) Surface and Si/6H-SiC Interface

2016 ◽  
Vol 858 ◽  
pp. 185-188 ◽  
Author(s):  
Xiao Min He ◽  
Zhi Ming Chen ◽  
Lian Bi Li
Keyword(s):  
Density Of States ◽  
First Principles ◽  
Density Functional ◽  
First Principles Calculation ◽  
Covalent Bonds ◽  
Functional Theory ◽  
Binding Force ◽  
Sulfur Passivation ◽  
Specific Geometry ◽  
Interface Structures

The un-passivated and passivated 6H-SiC(0001) surface and Si(-220)/6H–SiC (0001) interface are investigated by first-principles calculation based on density functional theory. It is demonstrated that the surface energy of 6H-SiC(0001) surface with seven atom-layers converges well. When the surface is passivated with sulfur(S), the density of states decreases obviously, implying that the passivated 6H-SiC(0001) surface are more stable. Four specific geometry models of Si(-220)/6H–SiC(0001) interface structures with different terminations are chosen. The calculated adhesion energies suggest that, for un-passivated interface, the atomic binding force and interface stability of C-termination interface are stronger than Si-termination interface, while for passivated interface, the tendency is opposite. The calculations about the density of states of un-passivated interfacial suggest that the Si-Si covalent bonds are formed at Si-terminated interface, and that C-Si covalent bonds are formed at C-terminated interface. After the interface is passivated with S atoms, the interaction between Si and S atoms is observed.

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