WoS İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/394
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Article Citation - WoS: 35Citation - Scopus: 42The Photoionization Cross Section of a Hydrogenic Impurity in a Multi-Layered Spherical Quantum Dot(Amer Inst Physics, 2012-04-15) Sahin, Mehmet; Tek, Firdes; Erdinc, Ahmet; Erdin, AhmetIn this study, we have investigated the photoionization cross section of an on-center hydrogenic impurity in a multi-layered spherical quantum dot. The electronic energy levels and their wave functions have been determined fully numerically by shooting method. Also, we have calculated the binding energy of the impurity by using these energy values. The photoionization cross section has also been computed as a function of the layer thickness and normalized photon energies. We have discussed in detail the possible physical reasons behind the changes in the binding energies and photoionization cross section. It is observed that both the binding energies and the photoionization cross sections depend strongly on the layer thickness and photon energies. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4705410]Article Citation - WoS: 68Citation - Scopus: 76The Inter-Sublevel Optical Properties of a Spherical Quantum Dot-Quantum Well With and Without a Donor Impurity(Amer Inst Physics, 2012-09-01) Tas, Hatice; Sahin, MehmetIn this study, we have investigated the inter-sublevel optical properties of a core/shell/well/shell spherical quantum dot (QD) with the form of quantum dot-quantum well heterostructure. In order to determine the energy eigenvalues and corresponding wave functions, the Schrodinger equation has been solved full numerically by using shooting method in the effective mass approximation for a finite confining potential. The inter-sublevel optical absorption and the oscillator strength between ground (1 s) and excited (1 p) states have been examined based on the computed energies and wave functions. Also, the effect of a hydrogenic donor impurity, located at the center of the multi-shell spherical quantum dot (MSQD), has been researched for different core radii (R-1), shell thicknesses (T-s), and well widths (T-w) in certain potential. It is observed that the oscillator strengths and the absorption coefficients are strongly depend on the core radii and layer thicknesses of the MSQD. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4751483]Article Citation - WoS: 15Citation - Scopus: 15The Electronic Properties of a Two-Electron Multi-Shell Quantum Dot-Quantum Well Heterostructure(Amer Inst Physics, 2013-07-24) Aydin, Rasit; Sahin, MehmetA detailed investigation of the electronic properties of a double electron in a core/shell/well/shell quantum dot heterostructure has been systematically studied for cases with and without an on-center donor impurity. For this purpose, the Poisson-Schrodinger equations have been solved self-consistently in the frame of the single band effective mass approximation and Hartree treatment. The variation of the binding energies of negatively charged donor impurity (D-) have been examined for different core radii, shell thicknesses, and well widths. The results obtained have been presented comparatively as a function of layer thicknesses and probable physical reasons behind in their behavior have been discussed. (C) 2013 AIP Publishing LLC.Article Citation - WoS: 56Citation - Scopus: 61The Electronic Properties of a Core/Shell Spherical Quantum Dot With and Without a Hydrogenic Impurity(Amer Inst Physics, 2012-04-15) Tas, Hatice; Sahin, MehmetIn this study, we have performed a detailed investigation of the electronic properties of a core/shell/well/shell multilayered spherical quantum dot, such as energy eigenvalues, wave functions, electron probability distribution, and binding energies. The energy eigenvalues and their wave functions of the considered structure have been calculated for cases with and without an on-center impurity. For this purpose, the Schrodinger equation has been numerically solved by using the shooting method in the effective mass approximation for a finite confining potential. The electronic properties have been examined for different core radii, barrier thicknesses, and well widths in a certain potential. The results have been analyzed in detail as a function of the layer thicknesses and their physical reasons have been interpreted. It has been found that the electronic properties are strongly dependent on the layer thicknesses. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3702874]Article Citation - WoS: 14Citation - Scopus: 16TD-DFTB Study of Optical Properties of Silver Nanoparticle Homodimers and Heterodimers(Amer Inst Physics, 2020-10-14) Liu, Zhen; Alkan, Fahri; Aikens, Christine M.The absorption spectra for face-centered cubic nanoparticle dimers at various interparticle distances are investigated using time-dependent density functional tight binding. Both homodimers and heterodimers are investigated in this work. By studying nanoparticles at various interparticle distances and analyzing their vertical excitations, we found that as the interparticle distance decreases, a red shift arises from contributions of the transition dipole moment that are aligned along the z-axis with nondegenerate features; blue shifts occur for peaks that originate from transition dipole moment components in the x and y directions with double degeneracy. When the nanoparticles are similar in size, the features in the absorption spectra become more sensitive to the interparticle distances. The best-fit curves from vertical excitation energy in the form of AR(-b) for Delta E-redshift/Delta E-blueshift vs R are determined. In this way, we determined trends for absorption peak shifts and how these depend on the interparticle distance.Article Citation - WoS: 33Citation - Scopus: 35Oscillation Characteristics of Mutually Impinging Dual Jets in a Mixing Chamber(Amer Inst Physics, 2018-11-01) Tomac, Mehmet N.; Gregory, James W.In this study, we consider the oscillatory behavior of mutually impinging jets in an enclosed, domeshaped mixing chamber. The frequency of the impinging jet oscillations is dictated by the flow rate, with the oscillatory behavior being grouped into three regimes: a low flow rate regime (Re < 1500), a transition regime (1500 < Re < 2000), and a high flow rate regime (Re > 2000). The detailed characteristics of the oscillations in the high flow rate regime (Re = 6800 in the present study) are investigated through simultaneous frequency and refractive-index-matched particle image velocimetry measurements. The oscillation mechanism in the high flow rate regime was found to be similar to that of the other two regimes, where jets collide and interact in an oscillatory manner. However, in the high flow rate regime, there is a distinct and phase-evolving process of saddle point formation and jet bifurcation that is not present at the lower flow rates. The jet bifurcation process is also distinctly related to the balance of vortical structures inside the mixing chamber, and saddle point formation plays a key role in the internal and external flow field of this configuration. The external sweep angle of the exiting jet increases with the flow rate throughout the low and transition flow rate regimes, but a constant sweep angle was found to persist in the high flow rate regime. Thus, formation and location of the internal saddle point is directly linked to the external sweep angle of the jet. (C) 2018 Author(s).Article Citation - WoS: 41Citation - Scopus: 42Linear and Nonlinear Optical Properties of GaAs/AlxGa1-xAs Multi-Shell Spherical Quantum Dot(Amer Inst Physics, 2013-11-11) Kavruk, Ahmet Emre; Sahin, Mehmet; Koc, Fatih; Emre Kavruk, AhmetIn this work, the optical properties of GaAs/AlxGa1-xAs/GaAs/AlyGa1-yAs multi-shell quantum dot heterostructure have been studied as a function of Al doping concentrations for cases with and without a hydrogenic donor atom. It has been observed that the absorption coefficient strength and/or resonant absorption wavelength can be adjusted by changing the Al content of inner-barrier and/or outer-barrier regions. Besides, it has been shown that the donor atom has an important effect on the control of the electronic and optical properties of the structure. The results have been presented as a function of the Al contents of the inner-barrier x and outer-barrier y regions and probable physical reasons have been discussed. (c) 2013 AIP Publishing LLC.