WoS İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/394
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Article Citation - WoS: 41Citation - Scopus: 45Optical Properties in a ZnS/CdS Core/Shell Spherical Quantum Dot: Electric and Magnetic Field and Donor Impurity Effects(MDPI, 2023-01-29) Toscano-Negrette, Rafael G.; Leon-Gonzalez, Jose C.; Vinasco, Juan A.; Morales, A. L.; Koc, Fatih; Kavruk, Ahmet Emre; Duque, C. A.A theoretical analysis of optical properties in a ZnS/CdS/ZnS core/shell/shell spherical quantum dot was carried out within the effective mass approximation. The corresponding Schrodinger equation was solved using the finite element method via the 2D axis-symmetric module of COMSOL-Multiphysics software. Calculations included variations of internal dot radius, the application of electric and magnetic fields (both oriented along z-direction), as well as the presence of on-center donor impurity. Reported optical properties are the absorption and relative refractive index change coefficients. These quantities are related to transitions between the ground and first excited states, with linearly polarized incident radiation along the z-axis. It is found that transition energy decreases with the growth of internal radius, thus causing the red-shift of resonant peaks. The same happens when the external magnetic field increases. When the strength of applied electric field is increased, the opposite effect is observed, since there is a blue-shift of resonances. However, dipole matrix moments decrease drastically with the increase of the electric field, leading to a reduction in amplitude of optical responses. At the moment impurity effects are activated, a decrease in the value of the energies is noted, significantly affecting the ground state, which is more evident for small internal radius. This is reflected in an increase in transition energies.Article Citation - WoS: 13Citation - Scopus: 15Advanced Tunability of Optical Properties of CdS/ZnSe Multi-Shell Quantum Dot by the Band Edge Engineering(Elsevier, 2023-01) Koc, Fatih; Kavruk, Ahmet Emre; Sahin, MehmetIn this study, the advanced manipulability of wave functions in a type-II multi-shell hetero-nanostructure (MS-HNS) and the tunability of radiative exciton lifetime over a wide range with and/or without changing in transition energies has been demonstrated by the band edge engineering. For this purpose, the electronic and optical properties of exciton (X) and biexciton (XX) in a spherical CdS/ZnSe/ZnTe/CdSe HNS have been explored in detail. In the calculations, effects of all Coulombic interactions between the charges have been taken into account on the wave functions. Moreover, in the case of XX, the exchange-correlation potential between the same charged particles has also been considered. The results have been presented as a function of CdS core radius and ZnSe shell thickness and the probable physical reasons have been discussed in detail.Article Citation - WoS: 24Citation - Scopus: 25A Model for the Recombination and Radiative Lifetime of Trions and Biexcitons in Spherically Shaped Semiconductor Nanocrystals(Amer Inst Physics, 2013-05-06) Sahin, Mehmet; Koc, FatihIn this letter, we propose a different model to determine the recombination oscillator strength of trions and biexcitons for bound and unbound cases in the effective mass approximation. The validity of our model has been confirmed by the radiative lifetime of the trion and biexciton in a spherical quantum dot. The results show that the model works with sufficient accuracy in comparison with results of more complex methods such as quantum Monte Carlo techniques and atomistic calculations. (C) 2013 AIP Publishing LLC.