Theoretical and Computational Analysis of Confinement Regimes in Spherical ZnO, CdS, and CdSe Colloidal Quantum Dots | Chapter 7 | Current Research Progress in Physical Science Vol. 7

Quantum dots (QDs) exhibit unique optical and electronic properties due to quantum confinement effects, making them promising candidates for various applications. This study investigates the confinement regimes of colloidal spherical ZnO, CdS, and CdSe quantum dots through computational simulations and theoretical analysis. Confinement regimes were delimited for each of the quantum dots based on the exciton Bohr radius of carriers of the respective semiconductor. The results delineate size-dependent confinement effects, revealing critical size ranges for strong, intermediate, and weak confinement regimes and their associated energy levels. These findings provide valuable insights into optimising quantum dot performance for applications in optoelectronics, field-effect transistors, and photonic technologies, advancing the understanding of these semiconductor nanostructures.

 

Author (s) Details

 

Harry, S. T.
Department of Physics, Ignatius Ajuru University of Education, Rumuolumeni, Port-Harcourt, Nigeria.

 

Please see the book here:- https://doi.org/10.9734/bpi/crpps/v7/4090

Ground State Confinement Energy of Quantum Dots and the Brus Equation: A Mathematical Approach | Chapter 9 | Current Perspective to Physical Science Research Vol. 8

 The present study review the ground state confinement energy term in the Brus equation for the bandgap energy of a spherically shaped semiconductor quantum dot within the framework of effective mass approximation. Bandgap variation in a nanometer sized semiconductor is due to Confinement energy. A good estimate of the confinement energy is important for optoelectronic based applications of quantum dot.  The Schrodinger wave equation for a spherical nanoparticle in an infinite spherical potential well was solved in spherical polar coordinate system. Physical reasons in contrast to mathematical expediency were considered and solution obtained. The result reveals that the shift in the confinement energy is less than that predicted by the Brus equation as was adopted in most literatures. A “bird eye" view of the brus equation reveals that it is nothing but a Schrodinger equation modified to account for the effect of an electron-hole pair (exciton) confined to a nanometric spherical shaped semiconductor referred to as quantum dot. It is blind to the varied crystal structures that exist for semiconductors.

Author(s) Details:

Harry, S. T.,
Department of Physics, Ignatius Ajuru University of Education, P.M.B. 5047, Rumuolumeni, Port Harcourt, Rivers State, Nigeria.

Adekanmbi, M. A.,
Department of Physics, Ignatius Ajuru University of Education, P.M.B. 5047, Rumuolumeni, Port Harcourt, Rivers State, Nigeria.

Please see the link here: https://stm.bookpi.org/CPPSR-V8/article/view/13986

Studies on Transient Processes under Excitation of Ultrashort Laser Pulses in Colloidal Solutions of CdSe/ZnS Quantum Dots | Chapter 6 | Research Trends and Challenges in Physical Science Vol. 5

 We previously concluded that RSA (reverse saturable absorption) is the key mechanism of optical limiting in CdSe/ZnS QDs by nanosecond pulses working simultaneously with "light quenching." The limiting kinetics and OL mechanisms are significantly altered when the pulse duration is reduced [1,2,3]. In the event of ps-pulses and bright light, free carriers absorption became considerable. We show that the Auger relaxation through the 1S(e) states determines the limiting efficiency of laser light and absorption kinetics in CdSe/ZnS colloidal solutions for picosecond durations. In the measured kinetics of a probe-pulse transmission, a "delayed limitation" effect has been discovered. Using numerical modelling, the competition between the following two relaxation mechanisms of highly excited states has been identified: relaxing through size quantization levels and phononless relaxation through traps states.

Author(S) Details

Vladimir V. Danilov
Emperor Alexander I St. Petersburg State Transport University, Saint-Petersburg 190031, Russia.

Anastasia S. Kulagina
St. Petersburg Academic University, Saint-Petersburg 194021, Russia and ITMO University, Saint-Petersburg 197101, Russia.

Nickolay V. Sibirev
ITMO University, Saint-Petersburg 197101, Russia.

View Book:- https://stm.bookpi.org/RTCPS-V5/article/view/4954

Diamagnetic Susceptibility of a Magneto-Donor in GaAs Spherical and Cylindrical Quantum Dot | Chapter 7 | Advanced Aspects of Engineering Research Vol. 2

The type effect is theoretically studied in the presence of a magnetic field on the binding energy and diamagnetic resistance of a shallow donor restricted to moving in Quantum Dots'QD '. Magnetic field effects are predominant for higher field intensity and large dots. The numerical calculations, using a variational method, are carried out in the effective mass approximation. We define an infinite deep potential as the result of quantum containment. For the Spherical Quantum Dot 'SQD' and Cylindrical Quantum Dot 'CQD', the shape effect is investigated. The findings for these two types of structures show that, with the magnetic field, the diamagnetic susceptibility and the binding energy increase. For larger dots, there are more pronounced ones. We note that the binding energy and diamagnetic susceptibility are decreasing functions of the quantum dot dimension for a zero magnetic field, according to theoretical literature findings. We hope this study will encourage further experimental interest in quantum dot structures on donors.

Author (s) Details

S. Janati. Edrissi
Groupe des Nanomatériaux et Energies Renouvelables, L P S, Faculté des Sciences Dhar Mehraz, BP 1796, Fès, Morocco.

I. Zorkani
Groupe des Nanomatériaux et Energies Renouvelables, L P S, Faculté des Sciences Dhar Mehraz, BP 1796, Fès, Morocco.

K. Rahmani
ERPTM, Polydisciplinary Faculty -Beni Mellal, Sultan My Slimane University, Beni Mellal, Morroco.

A. Jorio
Groupe des Nanomatériaux et Energies Renouvelables, L P S, Faculté des Sciences Dhar Mehraz, BP 1796, Fès, Morocco.

View Book :- https://stm.bookpi.org/AAER-V2/issue/view/31