scholarly journals Binding Energy of Exciton in Quantum Dots with the Central-cell Correction Depending on the Dot Sizes

2007 ◽  
Vol 14 (2) ◽  
pp. 95-99 ◽  
Author(s):  
To Thi Thao ◽  
Nguyen Ai Viet
Keyword(s):  
Quantum Dots ◽  
Binding Energy ◽  
Variational Methods ◽  
Effective Mass ◽  
Short Range ◽  
Central Cell ◽  
Short Range Potential ◽  
Two Parameters ◽  
Center Cell ◽  
Good Agreement

The binding energy of exciton in quantum dots with a parabolic confinement potential was calculated by variational methods beyond the Kohn-Luttinger effective mass theory, when the central-cell correction was taken into account.We have assumed that a short range potential with two parameters for strength and range for exciton, representing the center-cell effect also depends on dot size. Our result is in good agreement with experiment.

LOCALIZED EXCITONS IN SELF-ASSEMBLED InxGa1-xN QUANTUM DOTS

2005 ◽  
Vol 19 (12) ◽  
pp. 589-598
Author(s):  
XIAN-QI DAI ◽  
FENG-ZHEN HUANG ◽  
JUN-JIE SHI
Keyword(s):  
Quantum Dots ◽  
Binding Energy ◽  
Variational Approach ◽  
Structural Parameters ◽  
Exciton Binding Energy ◽  
Mass Approximation ◽  
Energy Maximum ◽  
Localized Excitons ◽  
The Relationship ◽  
Good Agreement

Within the framework of effective-mass approximation, the exciton states localized in cylindrical InGaN quantum dots (QDs) are investigated using a variational approach. The relationship between the exciton states and structural parameters of QDs with radius R and height L are studied in detail. The numerical results show that the exciton binding energy is sensitive to the ratio of R/L for a QD with a given volume. There is a maximum in the binding energy, where the electrons and holes are the most efficiently confined in the QDs with special structural parameters. The binding energy maximum can be obtained at about L = 1.7 nm for different QD volumes. The exciton binding energy and emission wavelength depend sensitively on structural parameters and the In content in the In x Ga 1-x N active layer. Our calculated emission wavelengths are in good agreement with experimental data.

THE EFFECT OF POSITION DEPENDENT EFFECTIVE MASS OF HYDROGENIC IMPURITIES IN PARABOLIC GaAs/GaAlAs QUANTUM DOTS IN A STRONG MAGNETIC FIELD

2009 ◽  
Vol 23 (26) ◽  
pp. 5109-5118 ◽  
Author(s):  
A. JOHN PETER
Keyword(s):  
Magnetic Field ◽  
Quantum Dots ◽  
Binding Energy ◽  
Effective Mass ◽  
Bound States ◽  
Mass Approximation ◽  
Infinite Case ◽  
Dependent Mass ◽  
The Magnetic Field ◽  
Peak Value

The binding energy of shallow hydrogenic impurities in parabolic GaAs/GaAlAs quantum dots is calculated as a function of dot radius in the influence of magnetic field. The binding energy has been calculated following a variational procedure within the effective-mass approximation. Calculations are presented with constant effective-mass and position dependent effective masses. A finite confining potential well with depth is determined by the discontinuity of the band gap in the quantum dot and the cladding. The results show that the impurity binding energy (i) increases as the dot radius decreases for the infinite case, (ii) reaches a peak value around 1R* as the dot radius decreases and then diminishes to a limiting value corresponding to the radius for which there are no bound states in the well for the infinite case, and (iii) increases with the magnetic field. Also it is found that (i) the use of constant effective mass (0.067 m0) is justified for dot sizes ≥ a* where a* is the effective Bohr radius which is about 100 Å for GaAs , in the estimation of ionization energy and (ii) the binding energy shows complicated behavior when the position dependent mass is included for the dot size ≤ a*. These results are compared with the available existing literatures.

scholarly journals Barrier Thickness and Hydrostatic Pressure Effects on Hydrogenic Impurity States in Wurtzite GaN/AlxGa1−xN Strained Quantum Dots

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Guangxin Wang ◽  
Xiuzhi Duan ◽  
Wei Chen
Keyword(s):  
Quantum Dots ◽  
Hydrostatic Pressure ◽  
Binding Energy ◽  
Effective Mass ◽  
Dielectric Constants ◽  
Pressure Effects ◽  
Physical Parameters ◽  
Barrier Thickness ◽  
Hydrogenic Impurity ◽  
Donor Binding Energy

Within the framework of the effective mass approximation, barrier thickness and hydrostatic pressure effects on the ground-state binding energy of hydrogenic impurity are investigated in wurtzite (WZ) GaN/AlxGa1−xN strained quantum dots (QDs) by means of a variational approach. The hydrostatic pressure dependence of physical parameters such as electron effective mass, energy band gaps, lattice constants, and dielectric constants is considered in the calculations. Numerical results show that the donor binding energy for any impurity position increases when the hydrostatic pressure increases. The donor binding energy for the impurity located at the central of the QD increases firstly and then begins to drop quickly with the decrease of QD radius (height) in strong built-in electric fields. Moreover, the influence of barrier thickness along the QD growth direction and Al concentration on donor binding energy is also investigated. In addition, we also found that impurity positions have great influence on the donor binding energy.

Donor States in Spherical GaAs-Ga1-xAlxAs Quantum Dots

1997 ◽  
Vol 11 (15) ◽  
pp. 673-679 ◽  
Author(s):  
Ecaterina C. Niculescu ◽  
Ana Niculescu
Keyword(s):  
Quantum Dots ◽  
Quantum Dot ◽  
Effective Mass ◽  
Coulomb Potential ◽  
Adjustable Parameter ◽  
Binding Energies ◽  
Central Cell ◽  
Shallow Donors ◽  
Mass Approximation ◽  
Donor States

The effect of the central cell correction on the binding energies of shallow donors in a spherical GaAs-Ga 1-x Al x As quantum dot is studied. The effective-mass approximation within a variational scheme is adopted and central cell corrections are calculated by using a Coulomb potential modified with an adjustable parameter. For small values of the radius of the dot large corrections are obtained for the shallow donors studied.

scholarly journals Impact of QW coupling on the binding energy in InGaN/GaN under the effects of the size, the impurity and the internal composition

2020 ◽  
Vol 330 ◽  
pp. 01012
Author(s):  
Walid Belaid ◽  
Haddou El Ghazi ◽  
Izeddine Zorkani ◽  
Anouar Jorio
Keyword(s):  
Binding Energy ◽  
Quantum Wells ◽  
Effective Mass ◽  
Variational Approach ◽  
Shallow Donor ◽  
Donor Impurity ◽  
Coupled Quantum Wells ◽  
Surrounding Matrix ◽  
Main Effect ◽  
Good Agreement

In the present paper, the binding energy of hydrogenic shallow-donor impurity in simple and double coupled quantum wells based on unstrained wurtzite (In,Ga)N/GaN is investigated. Considering the effective-mass and dielectric mismatches between the well and its surrounding matrix, the numerical calculations are performed within the framework of the parabolic band and the single band effective-mass approximations under the finite potential barrier using finite element method (FEM). According to our results, it appears that the main effect of the wells coupling is to enhance the binding energy. It is also obtained that the binding energy is strongly sensitive to the internal and external parameters and can be adjusted by the quantum well/barrier width, the impurity position and the internal Indium composition. Our results are in good agreement with the finding especially for those obtained by the variational approach.

scholarly journals Electrostatically assisted macroion association

2021 ◽  
Vol 24 (3) ◽  
pp. 33502
Author(s):  
J. Reščiš
Keyword(s):  
Monte Carlo ◽  
Molecular Docking ◽  
Binding Energy ◽  
Short Range ◽  
Dynamic Equilibrium ◽  
Model System ◽  
Binding Energies ◽  
Effective Attraction ◽  
Theoretical Results ◽  
Good Agreement

A model system of highly asymmetric polyelectrolyte with directional short-range attractive interactions was studied by canonical Monte Carlo computer simulations. Comparison of MC data with previously published theoretical results shows good agreement. For moderate values of binding energies, which matches those of molecular docking, a dynamic equilibrium between free and dimerized macroions is observed. Fraction of dimerized macroions depends on macroion concentration, binding energy magnitude, and on the valency of small counterions. Divalent counterions induce an effective attraction between macroions and enhance dimerization. This effect is most notable at low to moderate macroion concentrations.

Acceptor Binding Energies in GaN and AIN

1997 ◽  
Vol 482 ◽  
Author(s):  
Francisco Mireles ◽  
Sergio E. Ulloa
Keyword(s):  
Binding Energy ◽  
Effective Mass ◽  
Crystalline Phase ◽  
Energy Shift ◽  
Binding Energies ◽  
Bulk Crystals ◽  
Shallow Acceptors ◽  
Crystal Phases ◽  
Binding Energy Calculations ◽  
Good Agreement

AbstractWe present binding energy calculations for Mg, Zn, and C substitutional shallow acceptors in GaN and AIN for both, wurtzite (WZ) and zincblende (ZB) crystal phases. The calculations are performed within the effective mass theory through the 6 × 6 Rashba-Sheka-Pikus and the Luttinger- Kohn matrix Hamiltonians for WZ and ZB bulk crystals, respectively. An analytic representation for the pseudopotential is used to introduce the nature of the impurity atom. The energy shift due to polaron effects is also considered in this approach. The estimated ionization energies are in good agreement with those reported experimentally and those reported theoretically employing other methods. We find that the binding energies for ZB GaN acceptors are shallower than the corresponding impurities in the WZ crystalline phase. The binding energy dependence upon the crystal field splitting in the WZ compounds is analyzed.

Excitonic quasimolecules containing of two quantum dots

2016 ◽  
pp. 4024-4028 ◽  
Author(s):  
Sergey I. Pokutnyi ◽  
Wlodzimierz Salejda
Keyword(s):  
Quantum Dots ◽  
Binding Energy ◽  
Exchange Interaction ◽  
Coulomb Interaction ◽  
Silicate Glass ◽  
Glass Matrix ◽  
Silicate Glass Matrix

The possibility of occurrence of the excitonic  quasimolecule formed of spatially separated electrons and holes in a nanosystem that consists  of  CuO quantum dots synthesized in a silicate glass matrix. It is shown that the major contribution to the excitonic quasimolecule binding energy is made by the energy of the exchange interaction of electrons with holes and this contribution is much more substantial than the contribution of the energy of Coulomb interaction between the electrons and holes.

Supramolecular Assembly of U(IV) Clusters and Superatoms

2020 ◽  
Author(s):  
Ian Colliard ◽  
Gregory Morrosin ◽  
Hans-Conrad zur Loye ◽  
May Nyman
Keyword(s):  
Quantum Dots ◽  
Supramolecular Assembly ◽  
Emergent Properties ◽  
Organic Media ◽  
Body Centered Cubic ◽  
Cluster Anions ◽  
Charge Balance ◽  
Interpenetrating Networks ◽  
Hierarchical Assembly ◽  
Two Parameters

Superatoms are nanometer-sized molecules or particles that can form ordered lattices, mimicking their atomic counterparts. Hierarchical assembly of superatoms gives rise to emergent properties in superlattices of quantum-dots, p-block clusters, and fullerenes. Here, we introduce a family of uranium-oxysulfate cluster anions whose hierarchical assembly in water is controlled by two parameters; acidity and the countercation. In acid, larger Ln<sup>III</sup> (Ln=La-Ho) link hexamer (U<sub>6</sub>) oxoclusters into body-centered cubic frameworks, while smaller Ln<sup>III</sup> (Ln=Er-Lu &Y) promote linking of fourteen U<sub>6</sub>-clusters into hollow superclusters (U<sub>84</sub> superatoms). U<sub>84</sub> assembles into superlattices including cubic-closest packed, body-centered cubic, and interpenetrating networks, bridged by interstitial countercations, and U<sub>6</sub>-clusters. Divalent transition metals (TM=Mn<sup>II </sup>and Zn<sup>II</sup>), with no added acid, charge-balance and promote the fusion of 10 U<sub>6</sub> and 10 U-monomers into a wheel–shaped cluster (U<sub>70</sub>). Dissolution of U<sub>70</sub> in organic media reveals (by small-angle Xray scattering) that differing supramolecular assemblies are accessed, controlled by TM-linking of U<sub>70</sub>-clusters. <br>

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