Determination of the Exciton Binding Energy in CdSe Quantum Dots

Meulenberg, Robert W.; Lee, Jonathan R. I.; Wolcott, Abraham; Zhang, Jin Z.; Terminello, Louis J.; Buuren, T. van

doi:10.1021/nn8006916

Cited by 159 publications

(199 citation statements)

References 30 publications

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“…As shown in Fig. 2 29,30 They show that both materials have an n-type behavior and suggest the existence of a large valence-band discontinuity in PbSe/CdSe heterostructures since the VBM difference is 1.13 eV, slightly higher than the one that is found in the literature. 31 Such a result is consistent with the evidence for a quasi-type-II band alignment in PbSe/CdSe HNCs.…”

Section: A As-grown Heteronanocrystalsmentioning

confidence: 65%

Phase transformation of PbSe/CdSe nanocrystals from core-shell to Janus structure studied by photoemission spectroscopy

et al. 2013

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Photoelectron spectroscopic measurements have been performed, with synchrotron radiation on PbSe/CdSe heteronanocrystals that initially consist of core-shell structures. The study of the chemical states of the main elements in the nanocrystals shows a reproducible and progressive change in the valence-band and core-level spectra under photon irradiation, whatever the core and shell sizes are. Such chemical modifications are explained in light of transmission electron microscopy observations and reveal a phase transformation of the nanocrystals: The core-shell nanocrystals undergo a morphological change toward a Janus structure with the formation of semidetached PbSe and CdSe clusters. Photoelectron spectroscopy gives new insight into the reorganization of the ligands anchored at the surface of the nanocrystals and the modification of the electronic structure of these heteronanocrystals.

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Section: A As-grown Heteronanocrystalsmentioning

confidence: 65%

Phase transformation of PbSe/CdSe nanocrystals from core-shell to Janus structure studied by photoemission spectroscopy

et al. 2013

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“…Figure 1 About half of this discrepancy can be ascribed to the exciton binding energy, which is important in optical studies but is not represented in the calculation of DOS diagrams (experimentally worth ~0.6 to 0.9 eV for the QD sizes studied here). 73 The calculated gaps can be improved with the linear response time-dependent DFT (TDDFT) 74 or GW 75 methods, but the computational cost of these methods is impractical for the large systems studied here. Decomposition of the total densities of Fig.…”

Section: Results Of Dft Calculationsmentioning

confidence: 99%

Orbital pathways for Mn2+-carriersp−dexchange in diluted magnetic semiconductor quantum dots

et al. 2011

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Abstract. Manganese-carrier magnetic exchange interactions in strongly quantum confined -conduction-band-electron interaction is described well using the recently proposed ferromagnetic kinetic s-s exchange pathway. Antiferromagnetic kinetic s-d exchange interactions previously proposed to become dominant in quantum confined diluted magnetic semiconductors (DMSs) have been evaluated quantitatively by both DFT and perturbation theory and are found to be weak compared to the ferromagnetic s-s interaction, even in these strongly confined QDs. The magnitudes of the mean-field exchange parameters are found to be nearly independent of quantum confinement over this range of QD diameters, and the dominant orbital pathways are not fundamentally altered by quantum confinement.i.

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“…With our hybridization model, however, the CB minimum energy can be tuned depending on the amount of dopant, suggesting that the Cu related PL is tunable by changing dopant concentration within a constant particle size series. The bulk CdSe VB energy is set to zero and the CB shifts for the QDs are obtained from our current XAS measurements with the VB shifts coming from prior work 22 . Also included in the figure is the appearance of levels below the native CB minimum occurring from hybridization.…”

Section: Impact Of Hybridization On the Optical Properties Of Coppmentioning

confidence: 99%

Effects of dopants on the band structure of quantum dots: A theoretical and experimental study

Wright

Meulenberg

2013

Phys. Rev. B

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In this article, we present a theoretical framework that provides predictable results on band gap modifications due to the addition of dopants into CdSe quantum dots (QDs). A theoretical model is developed that predicts a lowering of the conduction band minimum (CBM) due to hybridization. We then use x-ray absorption spectroscopy (XAS) at the Cd M3-edge to determine the effects of chemical doping on the CB of the QD. Analysis of the XAS onset energy provides evidence for a lowering of the CBM, with our calculations yielding results comparable to experiment within 0.02 eV for tested materials. Also present in the XAS data is a distinct shift of the Cd M3-edge peak maximum as a function of particle size, suggesting this peak can be used as a tracer to probe the angular momentum resolved shifts in the CB states due to quantum confinement. Our theoretical model can model a variety of dopants and theoretically predict the shift in the energy levels, and should be generalizable towards predicting similar behavior in other materials.

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Determination of the Exciton Binding Energy in CdSe Quantum Dots

Cited by 159 publications

References 30 publications

Phase transformation of PbSe/CdSe nanocrystals from core-shell to Janus structure studied by photoemission spectroscopy

Phase transformation of PbSe/CdSe nanocrystals from core-shell to Janus structure studied by photoemission spectroscopy

Orbital pathways for Mn2+-carriersp−dexchange in diluted magnetic semiconductor quantum dots

Effects of dopants on the band structure of quantum dots: A theoretical and experimental study

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