scholarly journals Effect of Vacancy Defects on the Electronic Structure and Optical Properties of GaN

2017 ◽  
Vol 2017 ◽  
pp. 1-6 ◽  
Author(s):  
Lili Cai ◽  
Cuiju Feng
Keyword(s):  
Optical Properties ◽  
Electronic Structure ◽  
Lower Energy ◽  
Density Functional ◽  
Nitrogen Vacancy ◽  
Main Peak ◽  
Generalized Gradient ◽  
Vacancy Defects ◽  
Gallium Vacancy ◽  
Defect Levels

The effect of gallium vacancy (VGa) and nitrogen vacancy (VN) defects on the electronic structure and optical properties of GaN using the generalized gradient approximation method within the density functional theory were investigated. The results show that the band gap increases in GaN with vacancy defects. Crystal parameters decrease in GaN with nitrogen vacancy (GaN:VN) and increase in GaN with gallium vacancy (GaN:VGa). The Ga vacancy introduces defect levels at the top of the valence band, and the defect levels are contributed by N2p electron states. In addition, the energy band shifts to lower energy in GaN:VNand moves to higher energy in GaN:VGa. The level splitting is observed in the N2p states of GaN:VNand Ga3d states of GaN:VGa. New peaks appear in lower energy region of imaginary dielectric function in GaN:VNand GaN:VGa. The main peak moves to higher energy slightly and the intensity decreases.

scholarly journals Oxygen vacancy and doping atom effect on electronic structure and optical properties of Cd2SnO4

RSC Advances ◽  
2018 ◽  
Vol 8 (2) ◽  
pp. 640-646 ◽  
Author(s):  
Mei Tang ◽  
JiaXiang Shang ◽  
Yue Zhang
Keyword(s):  
Optical Properties ◽  
Electronic Structure ◽  
Oxygen Vacancy ◽  
Density Functional ◽  
Generalized Gradient ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
La Doped ◽  
Doping Atom ◽  
Atom Effect

The electronic structure and optical properties of oxygen vacancy and La-doped Cd2SnO4 were calculated using the plane-wave-based pseudopotential method based on the density functional theory (DFT) within the generalized gradient approximation (GGA).

scholarly journals DFT Calculation on the Electronic Structure and Optical Properties of InxGa1-xN Alloy Semiconductors

2019 ◽  
Vol 26 (2) ◽  
pp. 127-132
Author(s):  
Xuewen WANG ◽  
Wenwen LIU ◽  
Chunxue ZHAI ◽  
Jiangni YUN ◽  
Zhiyong ZHANG
Keyword(s):  
Optical Properties ◽  
Absorption Spectrum ◽  
Electronic Structure ◽  
Density Functional ◽  
Dft Calculation ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Photoelectric Performance ◽  
The Density Functional Theory ◽  
Alloy Semiconductors

Using the density functional theory (DFT) of the first principle and Generalized gradient approximation method, the electronic structures and optical properties of the InxGa1-xN crystals with different x (x = 0.25, 0.5, 0.75, 1) have been calculated in this paper. The influence of the electronic structure on the properties has been analyzed. Then the influence of doping quantity on the characteristics has been summarized, which also indicates the trend of complex dielectric function, absorption spectrum and transitivity. With the increase of x, the computational result shows that the optical band gap (i.e.Eg) of the InxGa1-xN crystal tends to be narrow, then the absorption spectrum shifts to the low-energy direction. And the Fermi energy slightly moves to the bottom of conduction band which would cause the growth of conductivity by increasing x. In a word, the InxGa1-xN compound can be achieved theoretically the adjustable Eg and photoelectric performance with x, which will be used in making various optoelectronic devices including solar cell and sensors.

STRUCTURAL, ELECTRONIC, MAGNETIC AND OPTICAL PROPERTIES OF FERROMAGNETIC Pb1-xEuxSe AND Pb1-xEuxTe ALLOYS (x = 0, 0.25, 0.50, 0.75 AND 1)

2013 ◽  
Vol 27 (19) ◽  
pp. 1350100 ◽  
Author(s):  
S. M. ALAY-E-ABBAS ◽  
S. YOUNAS ◽  
S. HANIF ◽  
M. SHARIF ◽  
IQBAL HUSSAIN ◽  
...  
Keyword(s):  
Optical Properties ◽  
Electronic Structure ◽  
Density Functional ◽  
Full Potential ◽  
Nonlinear Behaviour ◽  
Generalized Gradient ◽  
Electronic Band ◽  
Plane Wave Method ◽  
Energy Dependent ◽  
Electronic Band Structures

First-principles total energy calculations have been performed using full potential linear-augmented-plane-wave method within the framework of density functional theory to study the structural, electronic, magnetic and optical properties of the Pb 1-x Eu x Se and Pb 1-x Eu x Te (0 ≤ x ≤1) alloys in the ferromagnetic (FM) ordering. The calculations have been extended to treat the strongly localized f electrons of Eu atom by the self-interaction correction (SIC) approach. For structural optimization, the Wu and Cohen generalized gradient approximation (GGA) functional has been used, whereas for calculating electronic properties, the GGA parameterization scheme formulated by Engel and Vosko (EV) has also been utilized. It has been observed that the use of experimental value of Coulomb parameter (Uf- expt. ) within the SIC does not yield an accurate EuSe and EuTe energy band structure. The improvement in the electronic band structures of nonmagnetic PbSe / PbTe and ferromagnetic EuSe / EuTe have been achieved by considering the effects of spin–orbit coupling for Pb atoms, by a suitable choice of U and by treating the U values for Eu atom's f and d electrons as parameters. The electronic and optical properties of FM Pb 1-x Eu x Se in agreement with experiments can be achieved by combining EV GGA with a Hubbard U < Uf- expt. , however, a stronger and stable AFM coupling in EuTe leaves the above scheme unable to provide good electronic structure of FM Pb 1-x Eu x Te . In case of Pb 1-x Eu x Se the nonlinear behaviour of electronic structure is reflected in the optical properties of Eu -doped PbSe that have been studied in terms of incident photons' energy dependent complex dielectric function.

Exploring the role of vacancy defects in the optical properties of LiMgPO4

2020 ◽  
Vol 22 (28) ◽  
pp. 16244-16257 ◽  
Author(s):  
Pampa Modak ◽  
Brindaban Modak
Keyword(s):  
Density Functional Theory ◽  
Optical Properties ◽  
Electronic Structure ◽  
Density Functional ◽  
Structure Calculation ◽  
Hybrid Density Functional Theory ◽  
Functional Theory ◽  
Vacancy Defects ◽  
Hybrid Density Functional

A systematic electronic structure calculation employing hybrid density functional theory has been carried out to explore the role of all possible vacancy defects in neutral and charged states in the optical properties of LiMgPO4.

First-principles study of electronic and optical properties of Sr2ZnN2 under pressure

2016 ◽  
Vol 30 (10) ◽  
pp. 1650139
Author(s):  
Kai Liang ◽  
Hui Zhao
Keyword(s):  
Refractive Index ◽  
Optical Properties ◽  
Electronic Structure ◽  
Dielectric Function ◽  
First Principles ◽  
Density Functional ◽  
Optical Transition ◽  
Dft Method ◽  
Structural Parameter ◽  
Generalized Gradient

First-principles calculations of ternary Sr2ZnN2 compound using density-functional theory (DFT) method within the generalized gradient approximation (GGA) has been performed. Based on the optimized structural parameter, the electronic properties and optical properties have been researched. The calculated lattice constants are in agreement with the experimental and theoretical results. The electronic structure have been investigated throughout the calculated band structure and density of states (DOS). It shows that this compound belongs to the semiconductors with a band gap of about 0.775[Formula: see text]eV. Furthermore, in order to clarify the optical transition of this material, the optical properties such as dielectric function, absorption coefficient, reflectivity, refractive index and energy-loss function at different pressures of 0, 10 and 20[Formula: see text]GPa in the energy range 0–20[Formula: see text]eV were performed and discussed. It shows that Sr2ZnN2 is a strong anisotropy material and the imaginary part of dielectric function shifts to higher energy region as the pressure increases. The square of calculated static refractive index is equal to static dielectric function, which corresponds to the theory formula. In conclusion, pressure is a effective method to change the electronic structure and optical properties.

Influence of Nd-Doping on Electronic Structure and Optical Properties of ZnO

2014 ◽  
Vol 941-944 ◽  
pp. 658-661
Author(s):  
Lan Li Chen ◽  
Hong Duo Hu ◽  
Zhi Hua Xiong
Keyword(s):  
Optical Properties ◽  
Electronic Structure ◽  
Conduction Band ◽  
First Principles ◽  
Energy Region ◽  
Lower Energy ◽  
Density Functional ◽  
Functional Theory ◽  
Level Shifts ◽  
Lower Energy Region

A detailed first-principles study of electronic structure and optical properties of Nd-doping ZnO with various concentrations of Nd was performed using density functional theory. The results show that the band gap of Nd-doping ZnO slightly widens with the increasing Nd concentration, this is because the conduction band undergoes a greater shift toward the lower-energy region than the valence band, which is agreement with experimental results. Furthermore, in comparison to pure-ZnO, the Fermi level shifts into the conduction band after Nd-doping ZnO. And the calculated result of imaginary part of dielectric function of Nd-doping ZnO shows that there is a sharp peak in the lower-energy region, which is due to the electrons transition between d-d orbital of Nd atom.

Ab initio calculation on the Optical Properties of AA- Stacked two dimensional Graphene, Silicene, Germanene, and Stanene

2018 ◽  
Vol 1 (1) ◽  
pp. 46-50
Author(s):  
Rita John ◽  
Benita Merlin
Keyword(s):  
Optical Properties ◽  
Band Structure ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Complex Refractive Index ◽  
Single Layer ◽  
Generalized Gradient ◽  
Electronic Band ◽  
Wide Range ◽  
Optical Region

In this study, we have analyzed the electronic band structure and optical properties of AA-stacked bilayer graphene and its 2D analogues and compared the results with single layers. The calculations have been done using Density Functional Theory with Generalized Gradient Approximation as exchange correlation potential as in CASTEP. The study on electronic band structure shows the splitting of valence and conduction bands. A band gap of 0.342eV in graphene and an infinitesimally small gap in other 2D materials are generated. Similar to a single layer, AA-stacked bilayer materials also exhibit excellent optical properties throughout the optical region from infrared to ultraviolet. Optical properties are studied along both parallel (||) and perpendicular ( ) polarization directions. The complex dielectric function (ε) and the complex refractive index (N) are calculated. The calculated values of ε and N enable us to analyze optical absorption, reflectivity, conductivity, and the electron loss function. Inferences from the study of optical properties are presented. In general the optical properties are found to be enhanced compared to its corresponding single layer. The further study brings out greater inferences towards their direct application in the optical industry through a wide range of the optical spectrum.

First principles calculations of structural, electronic and optical properties of InN compound

2015 ◽  
Vol 29 (05) ◽  
pp. 1550028 ◽  
Author(s):  
R. Graine ◽  
R. Chemam ◽  
F. Z. Gasmi ◽  
R. Nouri ◽  
H. Meradji ◽  
...  
Keyword(s):  
Optical Properties ◽  
Band Structure ◽  
Density Functional ◽  
Local Density ◽  
Indium Nitride ◽  
Alternative Form ◽  
Full Potential ◽  
Generalized Gradient ◽  
Pressure Derivative ◽  
Electronic And Optical Properties

We carried out ab initio calculations of structural, electronic and optical properties of Indium nitride ( InN ) compound in both zinc blende and wurtzite phases, using the full-potential linearized augmented plane wave method (FP-LAPW), within the framework of density functional theory (DFT). For the exchange and correlation potential, local density approximation (LDA) and generalized gradient approximation (GGA) were used. Moreover, the alternative form of GGA proposed by Engel and Vosko (EV-GGA) and modified Becke–Johnson schemes (mBJ) were also applied for band structure calculations. Ground state properties such as lattice parameter, bulk modulus and its pressure derivative are calculated. Results obtained for band structure of these compounds have been compared with experimental results as well as other first principle computations. Our results show good agreement with the available data. The calculated band structure shows a direct band gap Γ → Γ. In the optical properties section, several optical quantities are investigated; in particular we have deduced the interband transitions from the imaginary part of the dielectric function.

Electronic Structure and Optical Properties of Non-Metals (N, F, P, Cl, S)-Doped Cubic NaTaO3 by Density Functional Theory

2009 ◽  
Vol 79-82 ◽  
pp. 1245-1248 ◽  
Author(s):  
Pei Lin Han ◽  
Xiao Jing Wang ◽  
Yan Hong Zhao ◽  
Chang He Tang
Keyword(s):  
Density Functional Theory ◽  
Optical Properties ◽  
Electronic Structure ◽  
Visible Light ◽  
Absorption Edge ◽  
Density Functional ◽  
Red Shift ◽  
Functional Theory ◽  
Photoactive Materials ◽  
Metal Doped

Electronic structure and optical properties of non-metals (N, S, F, P, Cl) -doped cubic NaTaO3 were investigated systematically by density functional theory (DFT). The results showed that the substitution of (N, S, P, Cl) for O in NaTaO3 was effective in narrowing the band-gap relative to the F-doped NaTaO3. The larger red shift of the absorption edge and the higher visible light absorption at about 520 nm were found for the (N and P)-doped NaTaO3. The excitation from the impurity states to the conduction band may account for the red shift of the absorption edge in an electron-deficiency non-metal doped NaTaO3. The obvious absorption in the visible light region for (N and P)-doped NaTaO3 provides an important guidance for the design and preparation of the visible light photoactive materials.

Electronic Structure Of (AgSb)xPbn-2xTen

2003 ◽  
Vol 793 ◽  
Author(s):  
Daniel I Bilc ◽  
S.D. Mahanti ◽  
M.G. Kanatzidis
Keyword(s):  
Electronic Structure ◽  
Ab Initio ◽  
Density Functional ◽  
Full Potential ◽  
Generalized Gradient ◽  
Two Component System ◽  
Functional Theory ◽  
Covalent Interaction ◽  
Salt Structure ◽  
Linearized Augmented Plane Wave

ABSTRACTComplex quaternary chalcogenides (AgSb)xPbn-2xTen (0<x<n/2) are thought to be narrow band-gap semiconductors which are very good candidates for room and high temperature thermoelectric applications. These systems form in the rock-salt structure similar to the well known two component system PbTe (x=0). In these systems Ag and Sb occupy Pb sites randomly although there is some evidence of short-range order. To gain insights into the electronic structure of these compounds, we have performed electronic structure calculations in AgSbTe2 (x=n/2). These calculations were carried out within ab initio density functional theory (DFT) using full potential linearized augmented plane wave (LAPW) method. The generalized gradient approximation (GGA) was used to treat the exchange and correlation potential. Spinorbit interaction (SOI) was incorporated using a second variational procedure. Since it is difficult to treat disorder in ab initio calculations, we have used several ordered structures for AgSbTe2. All these structures show semimetallic behavior with a pseudogap near the Fermi energy. Te and Sb p orbitals, which are close in energy, hybridize rather strongly indicating a covalent interaction between Te and Sb atoms.

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