A Study by Ab-Initio Calculation of Structural and Electronic Properties of Semiconductor Nanostructures Based on ZnSe (original) (raw)
Related papers
Analysis of structural and vibrational properties of ZnSe nanostructures: A DFT/TDDFT study
Egyptian Journal of Chemistry, 2019
T HE structural and vibrational properties of Zn n Se n (n=1,3,7,13) nanostructures have been investigated using the Gaussian 09 program, density functional theory (DFT) and time-dependent density functional theory (TDDFT) at the B3LYP level with 6-311G basis functions. The structural properties showed that the rebuilding in surface atoms deviated many bonds from their ideal length, the Zn-Se bond length decreased with the increase in the size of nanostructures and converged to the experimental value. Quantum confinement effect diminution was observed with the growing size of the nanostructures; hence, the energy gap converged to the experimental value of 2.7 eV. Moreover, the binding energy increased with the increase of the structure size, such that wurtziod2c (Zn 13 Se 13) is more stable than smaller structures. The vibrational properties results indicated that the experimental longitudinal optical mode (LO mode) is situated between bare and hydrogen passivated LO modes and very near to the bare case, this gave a good agreement with experimental findings. The presence of hydrogen atoms at the surface caused a several times decrease in vibrational force constant in comparison to the bare case. The IR spectrum for wurtzoid and HP wurtzoid were investigated. The optical edge in UV-Vis spectra of wurtzoid reduced from 4.5 eV to 4.2 eV of wurtzoid2c due to the increase in the size of the nanostructure, while the maximum peak for wurtzoid at 2.88 eV increased to 3.06 eV for wurtzoid2c showing a clear blue shift. These results leads to wide applications in fields such as photoelectronic devices, lasers, sensors, and LEDs.
A Theoretical Study on the Electronic Structure of ZnSe/ZnS and ZnS/ZnSe Core/Shell Nanoparticles
Journal of Physical Chemistry C, 2008
Results of theoretical investigation on the structural and electronic properties of GaAs/AlAs and AlAs/ GaAs core/shell nanoparticles are presented. We have considered relaxed structures of essentially spherical parts of the zinc-blende crystal structure. The electronic properties and the total energy were calculated using density-functional tight-binding method. Our results include the charge distribution, density of states (DOSs), electronic energy levels (in particular HOMO and LUMO), HOMO-LUMO gap, excitation spectra and their variation with shell thickness for both GaAs/AlAs and AlAs/GaAs core/shell systems.
Structural, and electronic properties of ZnX (X = S, Se, Te) by first-principles calculation
PROCEEDING OF THE 1ST INTERNATIONAL CONFERENCE ON ADVANCED RESEARCH IN PURE AND APPLIED SCIENCE (ICARPAS2021): Third Annual Conference of Al-Muthanna University/College of Science
The structural and electronic properties of wurtzite ZnX (X = S, Se, and Te) alloys have been explored through a highly accurate method that is Full Potential Linear Augmented Plane Wave (FP-LAPW). The framework of WIEN2k has been employed based on density functional theory. In order to enhance bandgap calculation and structure optimization, the newly-developed potential that is called modified Becke Johnson (mBJ) was used as the exchange-correlation interaction beside generalized gradient approximation (GGA). The lattice constant and bulk modulus results were close to experimental values and better than the earlier theoretical results. The mBJ findings for electronic properties were consistent with the experimental results. A direct gap (Γ-Γ) of energies have been obtained for these compounds of about 3.672 eV, 2.722 eV, 2.270 eV of ZnS, ZnSe and ZnTe, respectively. Present theoretical predictions may contribute towards the development of experimental studies on these compounds for optoelectronic devices.
Biointerface Research in Applied Chemistry , 2023
Within the framework of the density functional theory (DFT) using the Wien2k package and the method of linear extended plane waves (FP-LAPW), quantum mechanical calculations were implemented to study the structural, electronic, and optical properties of the ZnxCd1-xTe system in the full range of 0≤x≤1 with a step of 0.25. To determine the optimal volume and grid parameters, the calculation of the total energy of semiconductor nanocomposites CdTe, Zn0.25Cd0.75Te, Zn0.5 Cd0.5 Te, Zn0.75Cd0.25Te, and ZnTe, the generalized gradient approximation (GGA) was applied, which is based on relaxation (optimization) of the volume and minimization of energy (finding the energy of the ground state). According to our calculations within the framework of the DFT, with an increase in the Zn concentration, the constant lattice parameters and the size (volume) of these nanocrystals decrease and are in good agreement with the results obtained this work by the method of X-ray structural analysis. The calculated band gaps of these nanocrystals using the modified exchange-correlation potential mBJ tend to increase, which agrees with the experimental data. The results of spin-polarized and spin-orbit calculations of the band structure showed that all these nanocrystals have direct transition points for electrons. After approximation by the least-squares method, empirical formulas were obtained to establish the concentration dependence of changes in the volumes and bandgap of Zn-modified nanocrystals, which will help experimenters obtain particles with certain sizes and bandgap. Such theoretical studies further open the possibility of accurate prediction of the electronic-energy properties of other semiconductor nanosized structur
Calculation of electronic and optical properties of Zn-based II-VI semiconductors
ZnSe and ZnS are the prototype II-VI semiconductors and their cubic phase, which occurs naturally as a mineral, has been called the zinc-blende structure. ZnSe has received particular attention as a blue-lasing material and tremendous experimental efforts have been made to fabricate a sustainable ZnSe blue laser. On the other hand, the ternary system ZnS x Se 1-x is a good candidate for developing optoelectronic devices such as light emitting diodes (LEDs) or semiconductor lasers. It is also used as waveguides and confinement layers in laser diodes (LDs). In the present study, we have computed the electronic and optical properties of ZnSe, ZnS and ZnS x Se 1-x using the local model pseudopotential method under the VCA. A central aim of this study is to present the electronic and optical properties of the materials of interest in the zinc-blende structure.
Ab initio Studies of the Band Parameters of III–V and II–VI Zinc-Blende Semiconductors
Semiconductors, 2005
The effect of compression on the ionic trend of zinc blende crystals BN, BP, AlN, and AlP has been investigated using both density functional generalized gradient Perdew, Burke, and Ernzerhof (PBE) method and the restricted Hartree-Fock (RHF) theory. Lattice constant, binding energy, and bulk modulus have been also calculated. It is found that their values deviate from experimental one, and this deviation can be attributed to the small size of the clusters. On the other hand, charge transfer is in consistent with other theoretical and experimental results. In conclusion, one need to apply more accurate method, high level basis sets, and correlation corrections in order to get better ground state properties and a comprehensive calculation of polarity. However; our results are very supportive for atoms in molecules theory, because they show independent ionic atoms inside the covalent molecule.
Role ofdelectrons in the zinc-blende semiconductors ZnS, ZnSe, and ZnTe
Physical Review B, 1995
We perform ab initio pseudopotential total-energy calculations for ZnS, ZnSe, and ZnTe. Unlike in most previous calculations, we include Zn 3d orbitals (and, in case of Zn Te, Te 4d orbitals as we11) as part of the valence states in order to study the behavior of the d electrons and their in8uence on energy levels. The results for the structural and electronic properties are in better agreement with experimental data than in the case where d electrons are considered as part of the core states. The role of the d electrons in determining the bonding strength of the material and the character of the states near the band gap is analyzed and discussed.