Band Gap Widening and Quantum Confinement Effects of ZnO Nanowires by First-Principles Calculation

2011 ◽  
Vol 675-677 ◽  
pp. 243-246 ◽  
Author(s):  
Mei Li Guo ◽  
Xiao Dong Zhang
Keyword(s):  
Optical Properties ◽  
Band Gap ◽  
First Principles ◽  
Quantum Confinement ◽  
Density Functional ◽  
High Energy ◽  
Zno Nanowires ◽  
First Principles Calculation ◽  
Confinement Effects ◽  
Quantum Confinement Effects

ZnO nanowires are promising for photonic devices, biosensor and cancer cell imaging. We have performed a first-principles study to evaluate the electronic and optical properties of ZnO nanowires. We have employed the Perdew–Burke–Ernzerhof form of generalized gradient approximation in the frame work of density functional theory. Calculations have been carried out at different configurations. With decreasing diameter, the band gap of ZnO nanowires is increased due to the increase of quantum confinement effects. The results of imaginary part of the dielectric function indicate that the optical transition between valence band and conduction band has shifted to the high energy range as the diameter decreases. The ZnO nanowires show size-tunable optical properties.

QUANTUM CONFINEMENT EFFECTS ON THE OPTICAL PROPERTIES OF ION BEAM SPUTTERED NICKEL OXIDE THIN FILMS

2001 ◽  
Vol 15 (02) ◽  
pp. 191-200 ◽  
Author(s):  
M. GHANASHYAM KRISHNA ◽  
A. K. BHATTACHARYA
Keyword(s):  
Thin Films ◽  
Optical Properties ◽  
Nickel Oxide ◽  
Band Gap ◽  
Quantum Confinement ◽  
Ion Beam ◽  
Confinement Effects ◽  
Oxide Thin Films ◽  
Quantum Confinement Effects ◽  
Nickel Oxide Thin Films

Quantum confinement effects on the optical properties of ion beam sputtered nickel oxide thin films are reported. Thin films with crystallite sizes in the range 9 to 14 nm have been deposited on to fused silica substrates. There is an increase in band gap, from 3.4 to 3.9 eV, and a decrease in refractive index, from 2.4 to 1.6, with decrease in crystallite size, that can be attributed to quantum confinement effects. The effective mass approximation has been used to explain the observed behaviour in band gap variation.

scholarly journals Electronic and optical properties of vacancy ordered double perovskites A2BX6 (A = Rb, Cs; B = Sn, Pd, Pt; and X = Cl, Br, I): a first principles study

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Muhammad Faizan ◽  
K. C. Bhamu ◽  
Ghulam Murtaza ◽  
Xin He ◽  
Neeraj Kulhari ◽  
...  
Keyword(s):  
Optical Properties ◽  
Band Gap ◽  
First Principles ◽  
Density Functional ◽  
Perovskite Solar Cells ◽  
Dielectric Constants ◽  
Maximum Efficiency ◽  
Exchange Potential ◽  
Double Perovskites ◽  
Electronic And Optical Properties

AbstractThe highly successful PBE functional and the modified Becke–Johnson exchange potential were used to calculate the structural, electronic, and optical properties of the vacancy-ordered double perovskites A2BX6 (A = Rb, Cs; B = Sn, Pd, Pt; X = Cl, Br, and I) using the density functional theory, a first principles approach. The convex hull approach was used to check the thermodynamic stability of the compounds. The calculated parameters (lattice constants, band gap, and bond lengths) are in tune with the available experimental and theoretical results. The compounds, Rb2PdBr6 and Cs2PtI6, exhibit band gaps within the optimal range of 0.9–1.6 eV, required for the single-junction photovoltaic applications. The photovoltaic efficiency of the studied materials was assessed using the spectroscopic-limited-maximum-efficiency (SLME) metric as well as the optical properties. The ideal band gap, high dielectric constants, and optimum light absorption of these perovskites make them suitable for high performance single and multi-junction perovskite solar cells.

Quantum confinement effects and strain-induced band-gap energy shifts in core-shell Si-SiO2nanowires

2011 ◽  
Vol 83 (24) ◽  
Author(s):  
O. Demichel ◽  
V. Calvo ◽  
P. Noé ◽  
B. Salem ◽  
P.-F. Fazzini ◽  
...  
Keyword(s):  
Band Gap ◽  
Quantum Confinement ◽  
Band Gap Energy ◽  
Core Shell ◽  
Confinement Effects ◽  
Gap Energy ◽  
Quantum Confinement Effects

Mechanical Properties and Size Effects of ZnO Nanowires Studied by First-Principles Calculation

2010 ◽  
Vol 654-656 ◽  
pp. 1670-1673
Author(s):  
Zhan Jun Gao ◽  
You Song Gu ◽  
Yue Zhang
Keyword(s):  
Mechanical Properties ◽  
First Principles ◽  
Size Effects ◽  
Density Functional ◽  
Elastic Moduli ◽  
Axial Direction ◽  
Zno Nanowires ◽  
First Principles Calculation ◽  
Different Diameters ◽  
Ground State Energies

First-principles density functional calculations were performed to investigate mechanical properties of ZnO nanowires and the size effects. Structural optimizations were performed first, and a series of strains were applied to the nanowires in the axial direction. The ground state energies were calculated and the elastic moduli of ZnO nanowires were obtained from the energy versus strain curves. It is found that the elastic moduli of the ZnO nanowires with three different diameters (1.2, 1.5 and 1.8nm) are 136.3, 138.7 and 138.0 GPa, respectively, and that of bulk ZnO along [0001] direction is 140.1 GPa. The elastic modulus of ZnO nanowire is slightly lower than that of the bulk and it decreases as the diameter decreases. Comparisons to experimental results and theoretical predications are made.

First Principles Investigation on the Structural, Electronic and Optical Properties of Amorphous Silica Glass

2017 ◽  
Vol 268 ◽  
pp. 92-96
Author(s):  
R.M. Nor ◽  
S.N.M. Halim ◽  
Mohamad Fariz Mohamad Taib ◽  
M. Kamil Abd-Rahman
Keyword(s):  
Optical Properties ◽  
Band Gap ◽  
Electronic Properties ◽  
Amorphous Silica ◽  
First Principles ◽  
Glass Structure ◽  
Small Sample ◽  
First Principles Calculation ◽  
Electronic And Optical Properties ◽  
Amorphous Quartz

The structural, electronic, and optical properties of an amorphous SiO2 (a-SiO2) model is investigated by using first-principles calculation. Most research works used beta-cristobalite glass structure as a reference to amorphous silica structure. However, only the electronic properties were been presented without any link towards the optical properties. Here, we demonstrate simultaneous electronic and optical properties, which closely matched to a-SiO2 properties by generating small sample of amorphous quartz glass. Using the Rietveld refinement, amorphous silica structure was generated and optimized using density functional theory in CASTEP computer code. A thorough analysis of the amorphous quartz structure obtained from different thermal treatment was carried out. The structure of amorphous silica was validated with previous theoretical and experimental works. It is shown that small sample of amorphous silica have similar structural, electronic and optical properties with a larger sample. The calculated optical and electronic properties from the a-SiO2 glass match closely to previous theoretical and experimental data from others. The a-SiO2 band gap of 5.853 eV is found to be smaller than the experimental value of ~9 eV. This is due to the underestimation and assumption made in DFT. However, the band gap value is in good agreement with the other theoretical works. Apart from the absorption edge at around 6.5 eV, the refractive index is 1.5 at 0eV. Therefore, this atomic structure can served as a reference model for future research works on amorphous structures.

Electronic structures and optical properties of IV A elements-doped 3C-SiC from density functional calculations

2018 ◽  
Vol 32 (32) ◽  
pp. 1850389 ◽  
Author(s):  
Xuefeng Lu ◽  
Tingting Zhao ◽  
Xin Guo ◽  
Meng Chen ◽  
Junqiang Ren ◽  
...  
Keyword(s):  
Optical Properties ◽  
Band Gap ◽  
Electronic Structures ◽  
Density Functional ◽  
Visible Region ◽  
First Principles Calculation ◽  
Charge Difference Density ◽  
Direct Band ◽  
Density Analysis ◽  
Indirect Band Gap

Electronic structures and optical properties of IV A elements (Ge, Sn and Pb)-doped 3C-SiC are investigated by means of the first-principles calculation. The results reveal that the structure of Ge-doped system is more stable with a lower formation energy of 1.249 eV compared with those of Sn- and Pb-doped 3C-SiC systems of 3.360 eV and 5.476 eV, respectively. Doping of the IV A elements can increase the band gap, and there is an obvious transition from an indirect band gap to a direct band gap. Furthermore, charge difference density analysis proves that the covalent order of bonding between the doping atoms and the C atoms is Ge–C [Formula: see text] Sn–C [Formula: see text] Pb–C, which is fully verified by population values. Due to the lower static dielectric constant, the service life of 3C-SiC dramatically improved in production practice. Moreover, the lower reflectivity and absorption peak in the visible region, implying its wide application foreground in photoelectric devices.

First-principles study of optical properties in Ca-doped ZnO alloys

Open Physics ◽  
2012 ◽  
Vol 10 (5) ◽  
Author(s):  
Li-Na Bai ◽  
Jian-She Lian ◽  
Wei-Tao Zheng ◽  
Qing Jiang
Keyword(s):  
Optical Properties ◽  
First Principles ◽  
Density Functional ◽  
Optical Transition ◽  
High Energy ◽  
Ternary Alloys ◽  
Potential Candidate ◽  
Coulomb Interactions ◽  
Generalized Gradient ◽  
Light Emitters

AbstractVarious electronic and optical properties of Zn1−x CaxO ternary alloys of wurtzite structure are calculated using a first-principles approach based on the framework of the generalized gradient approximation to density-functional theory. In particular, on-site Coulomb interactions are introduced, which can reasonably well predict the electronic properties and band gaps of the Zn1−x CaxO (0≤x≤0.25) system. The imaginary part of the calculated dielectric function indicates that the optical transition between O 2p states in the valence band and Zn 4s states in the conduction band shifts to the high-energy range as the Ca concentration increases. The calculated band gap shows a significant increase with increasing Ca concentration. Therefore, Zn1−x CaxO ternary alloys may be a potential candidate alloy for optoelectronic materials, and especially for light-emitters and detectors.

scholarly journals Electronic structure and optical properties of CsI under high pressure: a first-principles study

RSC Advances ◽  
2017 ◽  
Vol 7 (83) ◽  
pp. 52449-52455 ◽  
Author(s):  
Qiang Zhao ◽  
Zheng Zhang ◽  
Xiaoping Ouyang
Keyword(s):  
Density Functional Theory ◽  
High Pressure ◽  
Optical Properties ◽  
Electronic Structure ◽  
First Principles ◽  
Calculation Method ◽  
Density Functional ◽  
First Principles Calculation ◽  
Functional Theory ◽  
First Principles Study

We investigated the effects of high pressure on the electronic structure and optical properties of a CsI crystal through a first-principles calculation method based on density functional theory.

First Principles Calculations of Electronic and Optical Properties of Al1-xLaxN

2011 ◽  
Vol 393-395 ◽  
pp. 110-113
Author(s):  
Chang Peng Chen ◽  
Mei Lan Qi
Keyword(s):  
Optical Properties ◽  
Band Gap ◽  
Density Functional ◽  
Density Functional Method ◽  
High Energy ◽  
Functional Method ◽  
Absorption Region ◽  
Additional Absorption ◽  
Calculation Results ◽  
La Substitution

Based on the density functional method, the electronic structures and the optical properties for Al1-xLaxN(x=0, 0.0625, 0.125, 0.1875) are comparatively investigated in detail. The calculation results indicate that La substitution of the Al sites induces effective reduction of the band gap of AlN, and the band gap being continuously reduced when increasing La doping level. With the increase of La concentration, both the imaginary part of dielectric function and the absorption spectrum show red-shift corresponding to the change of band gaps. Moreover, additional absorption peaks are observed above the absorption edge in the high-energy range which widens the absorption region.

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