First-Principles Calculations on the Electronic Structure of ZnO Nanowires

2012 ◽  
Vol 198-199 ◽  
pp. 23-27
Author(s):  
Nan Zhang ◽  
Hong Sheng Zhao ◽  
Dong Yang ◽  
Wen Jie Yan
Keyword(s):  
Electronic Structure ◽  
Band Gap ◽  
Valence Band ◽  
Conduction Band ◽  
First Principles ◽  
Density Functional ◽  
Valence Band Maximum ◽  
Zno Nanowires ◽  
Cross Sectional ◽  
Quantum Size

Based upon the density functional theory (DFT) in this paper, the first-principles approach is used to study the electronic structure of different cross-sectional diameters of ZnO [0001] nanowires of wurtzite structure. The results show that ZnO [0001] nanowires have a wide direct band gap. Located in the G-point of the Brillouin zone the conduction band minimum and valence band maximum are relatively smooth. The conduction band is mainly composed of Zn 4s and Zn 4p states, and the valence band is composed of Zn 3d and O 2p states. The effective mass of conduction band electrons and valence band holes are large while their mobility is very low which show that conductive ability of pure defect-free [0001] ZnO nanowires is weak. Along with the increase of the cross-sectional diameters, the band gap gradually decreases that indicates quantum size effects are obvious in the nano size range.

The Electronic and Structural Properties of 3C-SiC: A First-Principles Study

2014 ◽  
Vol 971-973 ◽  
pp. 208-212 ◽  
Author(s):  
Ying Gao ◽  
Fu Chun Zhang ◽  
Wei Hu Zhang
Keyword(s):  
Band Gap ◽  
Valence Band ◽  
Conduction Band ◽  
First Principles ◽  
Density Functional ◽  
Energy Splitting ◽  
Functional Theory ◽  
Structure Density ◽  
Indirect Band Gap ◽  
Electronic And Structural Properties

We investigate geometric structure, electronic structure and ground properties of 3C-SiC as obtained form first-principles calculations based on density functional theory with the LDA, GGA, B3LYP and HSE06 method. After comparative analysis of the total energy, band structure, density of states and the bulk modulus, we found that 3C-SiC was an indirect band gap semiconductor, the top of valence band was located at Γ point, and the bottom of conduction band was located at X point. The indirect band gap of 3C-SiC calculated by LDA, GGA, B3LYP and HSE06 was 1.34 eV, 1.44 eV, 2.88 eV and 2.26 eV, respectively. Especially for B3LYP and HSE06 methods which clearly calculated the energy splitting and the energy dispersion of both the top of valence band and the bottom of conduction band was in well agreement with the experimental data. These results will provide theoretical basis for the design and application of SiC materials.

A STUDY ON STRAIN AFFECTING ELECTRONIC STRUCTURE OF WURTZITE ZnO BY FIRST PRINCIPLES

2009 ◽  
Vol 23 (19) ◽  
pp. 2339-2352 ◽  
Author(s):  
LI BIN SHI ◽  
SHUANG CHENG ◽  
RONG BING LI ◽  
LI KANG ◽  
JIAN WEI JIN ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Electronic Structure ◽  
Band Structure ◽  
Valence Band ◽  
Density Of States ◽  
First Principles ◽  
Density Functional ◽  
Functional Theory ◽  
Electron Density Difference ◽  
Different Strains

Density of states and band structure of wurtzite ZnO are calculated by the CASTEP program based on density functional theory and plane-wave pseudopotential method. The calculations are carried out in axial and unaxial strains, respectively. The results of density of states in different strains show that the bottom of the conduction band is always dominated by Zn 4s, and the top of valence band is always dominated by O 2p. The variation of the band gap calculated from band structure is also discussed. In addition, p-d repulsion is used in investigating the variation of the top of the valence band in different strains and the results can be verified by electron density difference.

Theoretical Investigation on Electronic Properties of ZnO Crystals Using DFT-Based Calculation Method

2015 ◽  
Vol 1112 ◽  
pp. 41-44 ◽  
Author(s):  
Yudi Darma ◽  
Freddy Giovanni Setiawan ◽  
Muhammad Aziz Majidi ◽  
Andrivo Rusydi
Keyword(s):  
Band Gap ◽  
Valence Band ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Valence Band Maximum ◽  
Band Gaps ◽  
Generalized Gradient ◽  
Strong Electron ◽  
Electronic Band ◽  
Rocksalt Structure

We study the electronic band structure and density of states (DOS) on ZnO material in various crystal structures : wurtzite (W), zincblende (ZB), and rocksalt (RS) phases. Calculations are based on Density Functional Theory (DFT) with Generalized Gradient Approximation (GGA) for exchange-correlation functional and Hubbard correction to consider the strong electron correlations in 3d orbitals. After structural optimization, GGA results show that wurtzite and zincblende structures have a direct band gap of 0.749 eV and 0.637 eV, respectively, whereas rocksalt structure has an indirect band gap of 0.817 eV. Symmetrical shape of total DOS for spin up and spin down electrons indicates a zero total magnetic moment. For all ZnO structures, the upper valence band is formed by hybridization among O 2p and Zn 3d orbitals, while lower valence and conduction band are primarily filled by O 2s and Zn 4s, respectively. The GGA+U approach is found to improve the calculated band gaps and correct the position of Zn 3d state below Valence Band Maximum (VBM). From GGA+U, the band gaps for W-ZnO, ZB-ZnO, and RS-ZnO are 1.12 eV, 1.00 eV, and 1.11 eV, respectively.

Graphene sheet with periodic vacancy: A first principles study

2021 ◽  
Author(s):  
Deepti Maikhuri ◽  
Jaiparkash Jaiparkash ◽  
Haider Abbas
Keyword(s):  
Density Functional Theory ◽  
Magnetic Properties ◽  
Electronic Structure ◽  
Band Gap ◽  
Graphene Sheet ◽  
First Principles ◽  
Density Functional ◽  
Computational Analysis ◽  
Functional Theory ◽  
First Principles Study

Abstract We present a comprehensive first-principles study of the electronic structure of graphene sheet with periodic vacancy. We report the structural, electronic, and magnetic properties of the graphene sheet with periodic vacancy that possess 48 C & 28 H atoms. Computational analysis based on density functional theory predicts that the periodic vacancy can modulate the properties of graphene sheet. Results show that periodic vacancies lead to the manipulation of band gap & could be utilized to tailor the electronic properties of the sheet. Also, it is found that, the graphene sheet with periodic vacancy is non-magnetic in nature.

Electronic Structure and Ground State Properties of A4[Ag4O4] (A=Na, K and Rb): A First-Principles Study

2013 ◽  
Vol 665 ◽  
pp. 43-48
Author(s):  
Rajagopalan Umamaheswari ◽  
M. Yogeswari ◽  
G. Kalpana
Keyword(s):  
Electronic Structure ◽  
Band Gap ◽  
Ground State ◽  
First Principles ◽  
Density Functional ◽  
Electronic Band Structure ◽  
First Principles Calculation ◽  
Partial Density ◽  
Electronic Band ◽  
Ground State Properties

The first-principles calculation within density functional theory is used to study in detail the electronic structure and ground state properties of alkali-metal oxoargenates A4[Ag4O4] (A= Na, K and Rb). The total energies calculated within the atomic sphere approximation (ASA) were used to determine the ground state properties such as equilibrium lattice parameter, c/a ratio, bulk modulus and cohesive energy. The theoretically calculated equilibrium lattice constants values are in well agreement with the available experimental values. The electronic band structures, total and partial density of states are calculated. The result of electronic band structure shows that the KAgO and RbAgO are direct band gap semiconductors with their gap lying between the Γ-Γ points, whereas NaAgO is found to be an indirect band gap semiconductor with its gap lying between Z-Γ points.

Engineering of Graphene Band Structure by Haptic Functionalization

2012 ◽  
Vol 1407 ◽  
Author(s):  
Paul Plachinda ◽  
Raj Solanki ◽  
David Evans
Keyword(s):  
Electronic Structure ◽  
Band Structure ◽  
Band Gap ◽  
Metal Atom ◽  
First Principles ◽  
Density Functional Calculations ◽  
Density Functional ◽  
Electronic Devices ◽  
Metal Carbonyl

ABSTRACTWe have employed first-principles density-functional calculations to study the electronic characteristics of graphene functionalized by metal-bis-arene and metal-carbonyl molecules. It is shown that functionalization with M-bis-arene (M(C6H6)@gr, M=Ti, V, Cr, Mn, Fe) molecules leads to an opening in the band gap of graphene (up to 0.81eV for the Cr derivative), and functionalization with M-carbonyl (M(CX)3@gr, X=O,N; M= Cr, Mn, Fe, Co) up to one 1eV for M=Cr and X=O, and therefore transforms graphene from a semi-metal to a semiconductor. The band gap induced by attachment of a metal atom topped by a functionalizing group is attributed to modification of π-conjugation and depends on the concentration of functionalizing molecules, metal’s and moiety’s electronic structure. This approach offers a means of tailoring the band structure of graphene and potentially its applications for future electronic devices.

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.

Influence of the Concentration of La High Doping on Conduction of ZnO

2011 ◽  
Vol 295-297 ◽  
pp. 1322-1325
Author(s):  
Zhi Hua Xiong ◽  
Lan Li Chen ◽  
Qi Xin Wan
Keyword(s):  
Valence Band ◽  
Conduction Band ◽  
First Principles ◽  
Lower Energy ◽  
Lattice Parameter ◽  
Valence Band Maximum ◽  
Heavily Doped ◽  
Doped Zno ◽  
Systematic Understanding ◽  
La Doped

We have performed a study on La heavily doped ZnO, based on the first principles. The calculated results show that with the increase of concentration of La, the lattice parameter is expanded. It is found that the top of valence band maximum is determined by the O-p states and the conduction band minimum is depended on the La-f and La-d states. The band gap of doping system is broadened as the increase of concentration of La, because the valence band moves towards lower energy more than the conduction band does. Furthermore, it is found that heavily doping of La with low concentration can enhance the conductivity of ZnO. The results are helpful to gain a systematic understanding of electrical properties of La-doped ZnO.

First Principles Study of the Electronic Structure of In1-xGaxN

2012 ◽  
Vol 502 ◽  
pp. 144-148
Author(s):  
Ling Ling Mi ◽  
Guo Zhong Zhao
Keyword(s):  
Electronic Structure ◽  
Energy Level ◽  
Band Gap ◽  
Valence Band ◽  
Density Functional ◽  
Wide Band ◽  
Blue Shift ◽  
High Energy ◽  
Wide Band Gap ◽  
High Energy Level

The In1-xGaxN electronic structure is calculated by First principle based on density functional theory. The energy band structures and density of state is calculated. It can be found that the hybridization of the Ga4s4p and N2p，In5s5p is stronger than that of N2p，In5s5p in the undoped system. And it leads to the valence band moving towards to low energy level and the conduction band moving to the high energy level. Correspondingly, we can find a larger band gap than that of undoped InN. In conclusion, the wide band gap lead to the blue shift and Moss-Burstein effect occurs near the top valence band.

Atomic and Electronic Structure of Symmetric Tilt Boundaries in ZnO

2000 ◽  
Vol 654 ◽  
Author(s):  
Fumiyasu Oba ◽  
Shigeto R. Nishitani ◽  
Hirohiko Adachi ◽  
Isao Tanaka ◽  
Masanori Kohyama ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Band Gap ◽  
Valence Band ◽  
First Principles ◽  
Electronic States ◽  
Structure Characteristic ◽  
Symmetric Tilt ◽  
Tilt Boundaries ◽  
Lower Valence ◽  
Atomic And Electronic Structure

AbstractWe have investigated the atomic and electronic structure of symmetric tilt boundaries in ZnO by a first-principles plane-wave pseudopotential method. Equilibrium boundary geometries with distorted- and dangling-bonds are obtained. Localized electronic states form mainly at the lower valence band and the bottom of the upper valence band owing to the bond disorder. However, the electronic states near the band gap are not significantly affected; deep states are not generated in the band gap. The small effects of the bond disorder on the electronic structure can be attributed to the band structure characteristic of ZnO.

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