Oxygen Vacancies in Amorphous HfO2 and SiO2

2008 ◽  
Vol 1073 ◽  
Author(s):  
Chioko Kaneta ◽  
Takahiro Yamasaki
Keyword(s):  
First Principles ◽  
Density Functional ◽  
Formation Energy ◽  
Oxygen Vacancies ◽  
Gate Dielectrics ◽  
Propagation Mechanism ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
The Difference ◽  
Formation Energies

ABSTRACTFormation energies and electronic properties of oxygen vacancies in amorphous HfO2 gate dielectrics are investigated by employing the first-principles method based on the density functional theory. We have found that the formation energy of neutral oxygen vacancy in amorphous HfO2 distributes from 4.7 to 6.1 eV, most of which is lower than the value for cubic HfO2, 6.0 eV. We also investigated the stabilities of the Vo pairs in various charged state and compared with those in amorphous SiO2. We found that Vo++ is stabilized in the vicinity of Vo in SiO2. In HfO2, however, this does not happen. This suggests the difference of defect propagation mechanism in HfO2 and SiO2.

Calculation of electronic structure and mechanical properties of DO3–Fe75-xSi25Nix intermetallic compounds by first principles

2015 ◽  
Vol 29 (13) ◽  
pp. 1550087
Author(s):  
R. Ma ◽  
M. P. Wan ◽  
J. Huang ◽  
Q. Xie
Keyword(s):  
Mechanical Properties ◽  
Intermetallic Compounds ◽  
First Principles ◽  
Electronic Structures ◽  
Density Functional ◽  
Elastic Parameters ◽  
Functional Theory ◽  
Ni Content ◽  
The Density Functional Theory ◽  
The Difference

Based on the density functional theory (DFT), the plane-wave pseudopotential method was used to investigate the electronic structures and mechanical properties of DO 3– Fe 75-x Si 25 Ni x(x = 0, 3.125, 6.25 and 9.375) intermetallic compounds. The elastic parameters were calculated, and then the bulk modulus, shear modulus and elastic modulus were derived. The paper then focuses on the discussion of ductility and plasticity. The results show that by adding appropriate Ni to Fe 3 Si intermetallic compound can improve the ductility. But the hardness will increase when the Ni content exceeds 6.25%. Analysis of density of states (DOS) and overlap populations indicates that with the difference of the strength of bonding and activity, there were some differences of ductility among different Ni contents. The Fe 71.875 Ni 3.125 Si 25 has the lowest hardness because the covalent bonding (Fe–Si bond and Si–Ni bond) has the minimum covalent electrons.

Hydrogen Storage of Platinum Atoms Adsorbed on Graphene: First-Principles Plane Wave Calculations

2012 ◽  
Vol 246-247 ◽  
pp. 1057-1060 ◽  
Author(s):  
Ye Lu He ◽  
Shu Xia Wang
Keyword(s):  
Plane Wave ◽  
Hydrogen Storage ◽  
Molecular Orbital ◽  
First Principles ◽  
Density Functional ◽  
Generalized Gradient ◽  
Geometrical Structures ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
The Difference

The geometrical structures of platinum atoms adsorbed on graphene were optimized using plane wave pseudopotential method with generalized gradient approximation based upon the density functional theory. Adsorption energies of both intrinsic graphene and platinum atoms adsorbed on graphene were calculated theoretically. The results show that: Compared with the intrinsic, H2 molecules are strongly adsorbed onto the platinum atoms adsorbed on graphene with higher adsorbed energy. The difference between the highest hydrogen molecule occupied molecular orbital and the 1owest unoccupied molecular orbital is significantly reduced. Between hydrogen and other atoms, the charge transfers are apparent increased. All are help for hydrogen storage.

REACTIVITY AND STABILITY OF OXYGEN VACANCIES ON TiO2 ANATASE (101) SURFACE: FIRST-PRINCIPLES CALCULATIONS

2011 ◽  
Vol 25 (29) ◽  
pp. 4029-4037
Author(s):  
QILI CHEN ◽  
CHAOQUN TANG ◽  
BO LI ◽  
GUANG ZHENG ◽  
KAIHUA HE
Keyword(s):  
First Principles ◽  
Density Functional ◽  
Oxygen Vacancies ◽  
Atomic Displacement ◽  
Oxygen Adsorption ◽  
First Principles Calculations ◽  
Functional Theory ◽  
Tio2 Anatase ◽  
Technical Parameters ◽  
Formation Energies

In this study, density-functional theory plane-wave pseudopotential method was employed to investigate several oxygen vacancies on TiO 2 anatase (101) surface. At first, a suitable defect-free slab model has been established by analyzing the surface energies and the atomic relaxations influenced by different technical parameters. The formation energies of different kinds of oxygen vacancies in the outermost layer have also been compared as well as the atomic displacement of the defective surfaces. It was found that the presence of bridging oxygen vacancy is more energetically favored and causes larger atomic displacement than other types of surface oxygen vacancies. The reactivity of oxygen vacancies has also been tested by both molecular and dissociated oxygen adsorption. Furthermore, we discussed the configurations and the electronic properties of O 2-adsorbed surface, and found that the appearance of oxygen adsorbate-induced states in the band gap can make the surface sensitive to visible light.

Theoretical Study of the Electronic Structures of Na-Doped ZnO

2014 ◽  
Vol 665 ◽  
pp. 124-127 ◽  
Author(s):  
Qi Xin Wan ◽  
Bi Lin Shao ◽  
Zhi Hua Xiong ◽  
Dong Mei Li ◽  
Guo Dong Liu
Keyword(s):  
Electronic Structure ◽  
First Principles ◽  
Electronic Structures ◽  
Density Functional ◽  
Formation Energy ◽  
Theoretical Study ◽  
The Other ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Doped Zno

The first-principles with pseudopotentials method based on the density functional theory was applied to calculate the formation energy of impurities and the electronic structure of ZnO doped with Na. In Na-doped ZnO, NaOis the most unstable than the other cases. Simultaneously, NaZnis more stable than Naiaccording to that NaZnhave smaller formation energy. Furthermore, the electronic structure of Na-doped ZnO indicates that that NaZnbehaves as an acceptor, while Naibehaves as a donor.

First-Principles Calculation of Defect Formation and Positron Annihilation States in Bi2Te3

2017 ◽  
Vol 373 ◽  
pp. 41-45 ◽  
Author(s):  
Bin Zhao ◽  
Bo Zhou ◽  
Chong Yang Li ◽  
Ning Qi ◽  
Zhi Quan Chen
Keyword(s):  
First Principles ◽  
Density Functional ◽  
Formation Energy ◽  
Defect Formation ◽  
First Principles Calculation ◽  
Functional Theory ◽  
Rich Condition ◽  
The Density Functional Theory ◽  
Positron Wave Function ◽  
Positron Lifetimes

Defect formation energy in Bi2Te3 thermoelectric material was calculated using a first principles approach based on the Density Functional Theory (DFT). For vacancy-type defect, the Te1 vacancy (VTe1) is the most stable defect with low formation energy in both Bi-rich and Te-rich conditions, which indicates that the Te1 vacancies have higher probability to be formed. For antisite defects, the formation energy of BiTe1 is much lower than that of BiTe2 in Bi-rich condition, while in Te-rich condition it is beneficial for TeBi with lower formation energy. Positron wave function distribution and positron lifetimes of different annihilation states in Bi2Te3 were also calculated using the atomic superposition (ATSUP) method. The positron bulk lifetime in Bi2Te3 is about 231 ps, and for the neutral vacancy-type defects without relaxation, the positron lifetimes of VBi, VTe1 and VTe2 are 275 ps, 295 ps and 269 ps, respectively.

scholarly journals Electron-phonon interaction in In-induced √7 ×√3 structures on Si(111) from first-principles

2021 ◽  
Author(s):  
I. Yu. Sklyadneva ◽  
Rolf Heid ◽  
Pedro Miguel Echenique ◽  
Evgueni Chulkov
Keyword(s):  
Density Functional Theory ◽  
Double Layer ◽  
First Principles ◽  
Linear Response ◽  
Density Functional ◽  
Single Layer ◽  
Phonon Interaction ◽  
Functional Theory ◽  
Electron Phonon Interaction ◽  
The Density Functional Theory

Electron-phonon interaction in the Si(111)-supported rectangular √(7 ) ×√3 phases of In is investigated within the density-functional theory and linear-response. For both single-layer and double-layer √(7 ) ×√3 structures, it...

Electronic structure of the thermoelectric materials PbTe and AgPb18SbTe20 from first-principles calculations

2010 ◽  
Vol 25 (6) ◽  
pp. 1030-1036 ◽  
Author(s):  
Pengxian Lu ◽  
Zigang Shen ◽  
Xing Hu
Keyword(s):  
Band Structure ◽  
Thermoelectric Properties ◽  
First Principles ◽  
Electronic Structures ◽  
Density Functional ◽  
Partial Density ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Scanning Transmission ◽  
Linearized Augmented Plane Wave

To investigate the effects of substituting Ag and Sb for Pb on the thermoelectric properties of PbTe, the electronic structures of PbTe and AgPb18SbTe20 were calculated by using the linearized augmented plane wave based on the density-functional theory of the first principles. By comparing the differences in the band structure, the partial density of states (PDOS), the scanning transmission microscope, and the electron density difference for PbTe and AgPb18SbTe20, we explained the reason from the aspect of electronic structures why the thermoelectric properties of AgPb18SbTe20 could be improved significantly. Our results suggest that the excellent thermoelectric properties of AgPb18SbTe20 should be attributed in part to the narrowing of its band gap, band structure anisotropy, the much extrema and large DOS near Fermi energy, as well as the large effective mass of electrons. Moreover, the complex bonding behaviors for which the strong bonds and the weak bonds are coexisted, and the electrovalence and covalence of Pb–Te bond are mixed should also play an important role in the enhancement of the thermoelectric properties of the AgPb18SbTe20.

Mechanisms of Nitrogen Incorporation at 4H-SiC/SiO2 Interface during Nitric Oxide Passivation – A First Principles Study

2016 ◽  
Vol 858 ◽  
pp. 465-468 ◽  
Author(s):  
D.P. Ettisserry ◽  
Neil Goldsman ◽  
Akin Akturk ◽  
Aivars J. Lelis
Keyword(s):  
Nitric Oxide ◽  
Silicon Dioxide ◽  
First Principles ◽  
Density Functional ◽  
Oxygen Vacancies ◽  
Functional Theory ◽  
Power Mosfets ◽  
Voltage Instability ◽  
Nitrogen Incorporation ◽  
Effective Mobility

In this work, we investigate the behavior of Nitrogen atoms at 4H-Silicon Carbide (4H-SiC)/Silicon dioxide (SiO2) interface during nitric oxide passivation using ab-initio Density Functional Theory. Our calculations suggest different possible energetically favorable and competing mechanisms by which nitrogen atoms could a) incorporate themselves into the oxide, just above the 4H-SiC substrate, and b) substitute for carbon atoms at the 4H-SiC surface. We attribute the former process to cause increased threshold voltage instability (hole traps), and the latter to result in improved effective mobility through channel counter-doping, apart from removing interface traps in 4H-SiC power MOSFETs. These results support recent electrical and XPS measurements. Additionally, Nitric Oxide passivation is shown to energetically favor re-oxidation of the 4H-SiC surface accompanied by the generation of oxygen vacancies under the conditions considered in this work.

Oxygen vacancy migration in CSZ using density functional theory

2008 ◽  
Vol 1122 ◽  
Author(s):  
Byeong-Eon Lee ◽  
Dae-Hee Kim ◽  
Yeong-Cheol Kim
Keyword(s):  
Density Functional Theory ◽  
Oxygen Vacancy ◽  
Density Functional ◽  
Oxygen Vacancies ◽  
Nearest Neighbor ◽  
Functional Theory ◽  
The Third ◽  
Vacancy Migration ◽  
Neighbor Site ◽  
Formation Energies

AbstractWe studied oxygen migration in calcia-stabilized cubic zirconia (CSZ) using density functional theory. A Ca atom was substituted for a Zr atom in a 2×2×2 ZrO2 cubic supercell, and an oxygen vacancy was produced to satisfy the charge neutrality condition. We found that the formation energies of an oxygen vacancy, as a function of its location with respect to the Ca atom, were varied. The relative formation energies of the oxygen vacancies located at the first-, second-, third-, and fourth-nearest-neighbors were 0.0, −0.07, 0.19, and 0.19 eV, respectively. Therefore, the oxygen vacancy located at the second-nearest-neighbor site of the Ca atom was the most favorable, the oxygen vacancy located at the first-nearest-neighbor site was the second most favorable, and the oxygen vacancies at the third- and fourth-nearest-neighbor sites were the least favorable. We also calculated the energy barriers for the oxygen vacancy migration between oxygen sites. The energy barriers between the first and the second nearest sites, the second and third nearest sites, and the third and fourth nearest sites were 0.11, 0.46, and 0.23 eV, respectively. Therefore, the oxygen vacancies favored the first- and second-nearest-neighbor oxygen sites when they drifted under an electric field.

First principles analysis of oxygen vacancy formation and migration in Sr2BMoO6 (B = Mg, Co, Ni)

RSC Advances ◽  
2016 ◽  
Vol 6 (38) ◽  
pp. 31968-31975 ◽  
Author(s):  
Shuai Zhao ◽  
Liguo Gao ◽  
Chunfeng Lan ◽  
Shyam S. Pandey ◽  
Shuzi Hayase ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Oxygen Vacancy ◽  
First Principles ◽  
Density Functional ◽  
Dft Method ◽  
Double Perovskites ◽  
Functional Theory ◽  
Oxygen Vacancy Formation ◽  
The Density Functional Theory ◽  
And Migration

In this work, we present a detailed first-principles investigation on the stoichiometric and oxygen-deficient structures of double perovskites, Sr2BMoO6 (B = Mg, Co and Ni), using the density functional theory (DFT) method.

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