Absorption and intensity-dependent photoluminescence measurements on CdSe quantum dots: assignment of the first electronic transitions

Ekimov, A. I.; Hache, F.; Schanne-Klein, Marie-Claire; Ricard, D.; Flytzanis, C.; Kudryavtsev, I. A.; Yazeva, T. V.; Rodina, A. V.; Éfros, Al. L.

doi:10.1364/josab.10.000100

Cited by 754 publications

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“…(3) is the field produced by the SQD dipole moment P SQD = −iμ R at the MNP. The exciton radius in CdSe is about 5 nm, 25 while the typical radius of the considered SQD is about 1.5-2 nm, so the wave functions involved in the optical transition are extended over the whole dot. In deriving Eq.…”

Section: Formalismmentioning

confidence: 99%

Optical bistability and hysteresis of a hybrid metal-semiconductor nanodimer

Малышев¹,

2011

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Optical response of an artificial composite nanodimer comprising a semiconductor quantum dot and a metal nanosphere is analyzed theoretically. We show that internal degrees of freedom of the system can manifest bistability and optical hysteresis as functions of the incident field intensity. We argue that these effects can be observed for real-world systems, such as a CdSe quantum dot and an Au nanoparticle hybrid. These properties can be revealed by measuring the optical hysteresis of Rayleigh scattering. We also show that the total dipole moment of the system can be switched abruptly between its two stable states by small changes in the excitation intensity. The latter promises various applications in the field of all-optical processing at the nanoscale, the most basic of them being the volatile optical memory.

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Section: Formalismmentioning

confidence: 99%

Optical bistability and hysteresis of a hybrid metal-semiconductor nanodimer

Малышев¹,

2011

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“…The motion of electrons and holes is analyzed within the 6-band model that has successfully described optical spectra of CdSe NCs [23]. The significant elongation of NRs (b ≫ a) makes it possible, by using an adiabatic approximation, to separate the parallel motion from the motion perpendicular to the NR axis.…”

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confidence: 99%

“…The arrows in Fig.1 show the optically allowed transitions between the electron and hole QSLs, which have been obtained by the calculation of the overlap integral K nΛ,n ′ Λ ′ |jz | = d 2 ρΨ (e) nl (ρ)Ψ ± jz (ρ) (see Ref. [23]). The energy shift δε nΛj z of each 1D hole subband at finite k z can be described in terms of the 1D effective mass: δε nΛj z (k z ) =h 2 k 2 z /2m nΛj z .…”

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1D Exciton Spectroscopy of Semiconductor Nanorods

2004

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We have theoretically shown that optical properties of semiconductor nanorods are controlled by 1D excitons. The theory, which takes into account anisotropy of spacial and dielectric confinement, describes size dependence of interband optical transitions, exciton binding energies. We have demonstrated that the fine structure of the ground exciton state explains the linear polarization of photoluminescence. Our results are in good agreement with the measurements in CdSe nanorods.PACS numbers: 71.70.Gm, 77.22.Ej There is growing interest in nano-size crystalline semiconductor structures of various shapes such as nanocrystals (NCs) [1], nanorods (NRs) [2] and nanowires (NWs) [3] created by the "from the bottom up" technological approach. Size-tunable control of their optical and transport properties combined with the ability to move these nano-size objects around with precise control opens the exciting possibilities for the creation of new functional materials which can be used in unlimited applications. Among these nanostructures, the NCs are the most heavily studied and one can find a broad description of their properties and their potential applications in the reviews of Brus [4] and Alivisatos [5].The optical properties of NRs, however, differ significantly from those of NCs. Compared to NCs, the NRs show higher photoluminescence (PL) quantum efficiency [2], strongly linear polarized PL [6,7], an increase of the global Stokes shift [6], and significantly faster carrier relaxation [8]. The Auger processes in NRs are strongly suppressed relative to those in NCs [9,10], which subsequently decreases the optical pumping threshold for stimulated emission [10,11]. The size and shape dependence of the optical and tunneling gaps measured in CdSe NRs [12] shows an unexpectedly large difference that cannot be explained by the electron-hole Coulomb correction to the optical gap used for NCs. To describe their measurements Katz et al.[12] applied the four-band theory developed by Sercel and Vahala [13]. The most important result of the latter paper was the prediction of an inverse order of light and heavy hole subbands in NWs, which was later confirmed by semiempirical pseudopotential calculations [6,14,15] and numerical calculations within the 6 band model [16]. An anisotropy of the light hole-toelectron optical transition matrix element predicts some degree of the PL linear polarization parallel to the NW [17,18].The dielectric confinement connected with the difference between dielectric constants of semiconductor crystallites, κ s , and surrounding medium, κ m , (for example, see [19]) usually does not affect the optical spectra of NCs because the charge distributions of an excited electron and hole practically compensate each other at each point of the NC. This leads to a complete screening of an electric field of the total charge from penetration into the surrounding medium. This is not the case, however, in NRs where the electron and hole are at a distance larger than a NR radius and interact predominantly throu...

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“…The confinement of photo-generated electrons and holes in the nanocrystals can be tuned by adjusting the shape and height of the potential. Extensive work has been devoted to detailed comparison of theory of quantum confined electronic states in these nanocrystals with experiments in which the diameter of spherical dots is varied [5][6][7][8][9][10][11][12][13] . Early phenomenological models are based on the effective mass approximation [7][8][9][10] ; later developments include tight-binding models 11,12 and empirical pseudo-potential calculations 13 .…”

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confidence: 99%