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Nonlinear optical properties of core shell type II quantum dot structures
摘要： In this study, CdSe/CdTe Type-II quantum dots (QDs) were synthesized using dropwise method. The core/shell nanocrystals have been characterized by UV–Vis absorption and photoluminescence (PL) spectroscopies, transmission electron microscopy and z-scan technique. Nonlinear properties of each type of quantum dots were studied using femtosecond(fs) z-scan method at 800 nm wavelength with different laser intensities. Fs laser z-scan experimental set-up are used to determine two photon absorption coefficient (β ?10?12 cm/W) and nonlinear optical Kerr coefficient (n2 ? 10?20 cm2/W. The imaginary and real parts of third order susceptibility (X(3)) were calculated based on β and n2 under different laser intensities for seven different core/shell QDs. Third order susceptibility for CdSe/CdTe type II QDs was found to be about 10?12 esu.
关键词： Femtosecond Z-scan,CdSe/CdTe,Type-II quantum dots
更新于2025-09-23 15:21:01
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Synthesis, characterization and the photoinduced electron-transfer energetics of CdTe/CdSe type-II core/shell quantum dots
摘要： The CdTe/CdSe type-II core/shell quantum dots (QDs) were chemically synthesized in a noncoordinating solvent. The optical properties and structures of the synthesized QDs were characterized by absorption spectroscopy (Abs), photoluminescence (PL) spectroscopy, PL-decay lifetime, X-ray diffraction (XRD), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDX). The PL peak of the CdTe/CdSe core/shell QDs could be tuned from 698 nm (1.77 eV) to 780 nm (1.59 eV) by changing the thickness of CdSe shell and fixing the size of CdTe core. The PL quantum yields (QYs) of these QDs were from 14.1% to 31.7% and their full width at half maximum (FWHM) of PL peaks was kept below 0.12 eV during the growth process of CdSe shell on CdTe core. Compared to CdTe cores, the CdTe/CdSe type-II core/shell QDs have much longer PL decay times, up to ~100 ns. Based on Marcus theory, the charge transfer (CT) of CdTe/CdSe 1-5 monolayers (MLs) type-II core/shell QDs has been studied and the effects of quantum confinement on the structure parameters have been revealed. The reorganization energies (RE) of the CdTe/CdSe (1-5 ML) type-II core/shell QDs for the electron transfer (ET) were in the range from 60 meV to 106 meV and was found that ET takes place in the Marcus inverted region (-?G0 ET > λCT) which is typical for these QDs.
关键词： core/shell,reorganization energy,type-II quantum dots,spatial separations,CdTe/CdSe
更新于2025-09-19 17:13:59
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[IEEE 2019 34th Symposium on Microelectronics Technology and Devices (SBMicro) - Sao Paulo, Brazil (2019.8.26-2019.8.30)] 2019 34th Symposium on Microelectronics Technology and Devices (SBMicro) - Transition Energy Calculations of Type II In(As)P/InGaP Quantum Dots for Intermediate Band Solar Cells
摘要： In this work, we perform computational simulations of InAsP type II quantum dots for an intermediate band solar cell. We have varied parameters such as height, width and percentage of P of the quantum dots alloy to determine their influence on the optical transitions` energies and electronic confinement within the quantum dots.
关键词： simulation,energy transitions,InP quantum dots,type II quantum dots
更新于2025-09-12 10:27:22
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Influence of MBE growth parameters on GaSb/GaAs quantum dot morphology
摘要： In this paper, growth of self-assembled type-II GaSb/GaAs quantum dots by molecular beam epitaxy technique is presented. The effect of various growth parameters such as substrate temperature, Sb/Ga beam equivalent pressure ratio, growth rate and total mono-layer coverage on surface morphology is analyzed. The GaSb quantum dots exhibit high anisotropy along <110> and <1-10> directions under specific growth conditions. The anisotropy is discussed on the basis of incorporation of background Arsenic and anisotropic diffusion of Gallium adatoms on the GaSb surface. The low temperature photoluminescence measurements in GaAs capped samples show recombination in the type-II quantum dots and the wetting layer.
关键词： Self assembled process,Anisotropy,Molecular beam epitaxy,Type-II quantum dots,Stranski-Krastanov growth
更新于2025-09-12 10:27:22