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.

Stability and Reactivity of [11-20] Step in Initial Stage of Epitaxial Graphene Growth on SiC(0001)

2014 ◽  
Vol 778-780 ◽  
pp. 1150-1153
Author(s):  
Hiroyuki Kageshima ◽  
Hiroki Hibino ◽  
Hiroshi Yamaguchi ◽  
Masao Nagase
Keyword(s):  
Surface Morphology ◽  
First Principles ◽  
Epitaxial Graphene ◽  
First Principles Calculation ◽  
Control Parameters ◽  
Graphene Growth ◽  
Initial Stage ◽  
The Stability

The energetics for the Si desorption and the C adsorption at a [11-20] step on SiC(0001) surface are studied using the first-principles calculation. It is found that the [11-20] step is stable and nonreactive. The stability of the step is thought to govern the surface morphology during the graphene formation. It is shown that the Si pressure and the temperature are the control parameters for the surface morphology and the graphene quality.

Theoretical Strength of Metals and Intermetallics from First Principles

2005 ◽  
Vol 482 ◽  
pp. 33-38 ◽  
Author(s):  
Mojmír Šob ◽  
Jaroslav Pokluda ◽  
Miroslav Černý ◽  
Pavel Šandera ◽  
V. Vitek
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
First Principles ◽  
State Of The Art ◽  
The State ◽  
Experimental Results ◽  
Theoretical Strength ◽  
Stability Conditions ◽  
The Stability

The state of the art of ab-initio calculations of the theoretical strength (TS) of materials is summarized and a database of selected theoretical and experimental results presented. Differences between theoretical and experimental TS values are discussed by assessing the stability conditions.

scholarly journals Effects of Doped Elements (Si, Cr, W and Nb) on the Stability, Mechanical Properties and Electronic Structures of MoAlB Phase by the First-Principles Calculation

Materials ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 4221
Author(s):  
Yongxin Jian ◽  
Zhifu Huang ◽  
Yu Wang ◽  
Jiandong Xing
Keyword(s):  
Mechanical Properties ◽  
Chemical Bonding ◽  
First Principles ◽  
Electronic Structures ◽  
Density Functional ◽  
Formation Enthalpy ◽  
First Principles Calculation ◽  
Elemental Doping ◽  
The Stability ◽  
W Doping

First-principles calculations based on density functional theory (DFT) have been performed to explore the effects of Si, Cr, W, and Nb elements on the stability, mechanical properties, and electronic structures of MoAlB ternary boride. The five crystals, with the formulas of Mo4Al4B4, Mo4Al3SiB4, Mo3CrAl4B4, Mo3WAl4B4, and Mo3NbAl4B4, have been respectively established. All the calculated crystals are thermodynamically stable, according to the negative cohesive energy and formation enthalpy. By the calculation of elastic constants, the mechanical moduli and ductility evolutions of MoAlB with elemental doping can be further estimated, with the aid of B/G and Poisson’s ratios. Si and W doping cannot only enhance the Young’s modulus of MoAlB, but also improve the ductility to some degree. Simultaneously, the elastic moduli of MoAlB are supposed to become more isotropic after Si and W addition. However, Cr and Nb doping plays a negative role in ameliorating the mechanical properties. Through the analysis of electronic structures and chemical bonding, the evolutions of chemical bondings can be disclosed with the addition of dopant. The enhancement of B-B, Al/Si-B, and Al/Si-Mo bondings takes place after Si substitution, and W addition apparently intensifies the bonding with B and Al. In this case, the strengthening of chemical bonding after Si and W doping exactly accounts for the improvement of mechanical properties of MoAlB. Additionally, Si doping can also improve the Debye temperature and melting point of the MoAlB crystal. Overall, Si element is predicted to be the optimized dopant to ameliorate the mechanical properties of MoAlB.

First Principles Calculation for Point Defect Behavior, Oxygen Precipitation and Cu Gettering in Czochralski Silicon

2005 ◽  
Vol 108-109 ◽  
pp. 365-372 ◽  
Author(s):  
Koji Sueoka ◽  
S. Shiba ◽  
S. Fukutani
Keyword(s):  
Crystal Growth ◽  
Point Defect ◽  
First Principles ◽  
First Principles Calculation ◽  
Interstitial Oxygen ◽  
Defect Engineering ◽  
Czochralski Silicon ◽  
Oxygen Precipitation ◽  
Initial Stage ◽  
P Type

Theoretical consideration for technologically important phenomena in defect engineering of Czochralski silicon was performed with first principles calculation. (i) Point defect behaviour during crystal growth, (ii) enhanced oxygen precipitation in p/p+ epitaxial wafers, and (iii) Cu gettering by impurities are main topics in this work. Following results are obtained. (i) Interstitial Si I is dominant in p type Si while vacancy V is dominant in n type Si during crystal growth when dopant concentration is higher than about 1x1019atoms/cm3. (ii) In initial stage of oxygen precipitation including a few interstitial oxygen (O) atoms, BOn complex is more stable than On complex. The diffusion barrier of O atom in p+ Si is reduced to about 2.2eV compared with the barrier of about 2.5eV in intrinsic Si. (iii) In substitutional B, Sb, As, P and C atoms, only B atom can be an effective gettering center for Cu.

First-principles study of Cu adsorption on vacancy-defected/Au-doped graphene

2018 ◽  
Vol 32 (11) ◽  
pp. 1850139 ◽  
Author(s):  
Yang Liu ◽  
Libao An ◽  
Liang Gong
Keyword(s):  
First Principles ◽  
Population Analysis ◽  
First Principles Calculation ◽  
Matrix Composites ◽  
Mulliken Population ◽  
Vacancy Defects ◽  
Subsequent Investigation ◽  
Doped Graphene ◽  
The Stability ◽  
P Type

To enhance the interaction between Cu and graphene in graphene reinforced Cu matrix composites, the first principles calculation was carried out to study the adsorption of Cu atoms on graphene. P-type doping and n-type doping were formed, respectively, on vacancy-defected and Au-doped graphene based on band structure analysis, and this was verified by subsequent investigation on density of states. A computation on charge transfer confirmed that p-type doping could promote the electron transport between Cu and graphene, while n-type doping would prevent it. In addition, adsorption energy and Mulliken population analysis revealed that both vacancy defects and Au doping could improve the stability of the Cu–graphene system. The research conducted in this paper provides useful guidance for the preparation of Cu/graphene composites.

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 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.

The stability of 3C-SiC(111) on Si(111) Thin Films: First-principles calculation

2021 ◽  
pp. 138318
Author(s):  
Eric K.K. Abavare ◽  
Bright Kwakye-Awuah ◽  
Oswald A. Nunoo ◽  
Peter Amoako-Yirenkyire ◽  
G. Gebreyesus ◽  
...  
Keyword(s):  
Thin Films ◽  
First Principles ◽  
First Principles Calculation ◽  
The Stability
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