Optical properties of PbSe

Suzuki, Norihiro; Sawai, Katsuyuki; Adachi, Sadao

doi:10.1063/1.358926

Cited by 77 publications

(76 citation statements)

References 19 publications

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“…These equations are obtained using the MG effective medium theory and bulk PbSe data at 400 nm ( R ϭ Ϫ10.67, I ϭ 20.54), 35 as optical properties are also bulk-like at this wavelength. In addition to our data, Dai et al 17 recently reported a wavelength-integrated gap, (normalized by a standard peak width of K ϭ 60 nm).…”

Section: Discussionmentioning

confidence: 99%

Size-Dependent Optical Properties of Colloidal PbS Quantum Dots

et al. 2009

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We quantitatively investigate the size-dependent optical properties of colloidal PbS nanocrystals or quantum dots (Qdots) by combining-the Qdot absorbance spectra with detailed elemental analysis of the Qdot suspensions. At high energies, the molar extinction coefficient epsilon increases With the Not volume d(3) and agrees with theoretical calculations using the Maxwell-Garnett effective medium theory and bulk values for the Qdot dielectric function. This demonstrates that quantum confinement has no influence on E in this spectral range, and it provides an accurate method to calculate the Qdot concentration. Around the band gap, epsilon only increases with d(1.3), and values are comparable to the epsilon of PbSe Qdots. The data are related to the oscillator strength f(if) of the band gap transition and results agree well with theoretical tight-binding calculations, predicting a linear dependence of f(if) on d. For both PbS and PbSe Qdots, the exciton lifetime tau is calculated from f(if). We find values ranging between 1 and 3 mu s, in agreement with experimental literature data from time-resolved luminescence spectroscopy. Our results provide a thorough general framework to calculate and understand the optical properties of suspended colloidal quantum dots. Most importantly, it highlights the significance of the local field factor in these systems

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Section: Discussionmentioning

confidence: 99%

Size-Dependent Optical Properties of Colloidal PbS Quantum Dots

et al. 2009

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“…of PbSe nanocrystals deposited on gold by spectroscopic ellipsometry. The dielectric function of the PbSe nanocrystals can be described by a sum of two Lorentz oscillators, as reported before for bulk PbSe [7]. This shape of the dielectric function is determined by an increase of the oscillator strength and the joint density of states near the Van Hove singularities along the directions and in the Brillouin zone [8].…”

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confidence: 97%

“…Since the width of the oscillator is considerable, the resonance energies are slightly shifted relative to the maximum of im . The spectrum of im obtained at the 8.8 nm nanocrystals resembles that of bulk PbSe [7]. Figure 4 represents the resonance energy of the oscillators as a function of the nanocrystal height.…”

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confidence: 97%

“…This model was chosen since the description of the dielectric function of PbSe in the visible as a sum of two Lorentz oscillators has been reported before for bulk PbSe [7]. As demonstrated by Fig.…”

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“…One is obtained taking the anisotropy of into account, whereas the second assumes a layer with an isotropic dielectric function equal to xy . First, since the isotropic [7]. and anisotropic spectra coincide, Fig.…”

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Effect of Quantum Confinement on the Dielectric Function of PbSe

et al. 2004

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Monolayers of lead selenide nanocrystals of a few nanometers in height have been made by electrodeposition on a Au(111) substrate. These layers show a thickness-dependent dielectric function, which was determined using spectroscopic ellipsometry. The experimental results are compared with electronic structure calculations of the imaginary part of the dielectric function of PbSe nanocrystals. We demonstrate that the size-dependent variation of the dielectric function is affected by quantum confinement at well-identifiable points in the Brillouin zone, different from the position of the band-gap transition. DOI: 10.1103/PhysRevLett.92.026808 PACS numbers: 73.22.Dj, 73.63.-b Semiconductor nanocrystals with dimensions below 10 nm possess optical properties that depend strongly on the size and shape of the nanocrystals. This is due to confinement of the exciton wave function in the limited space of the nanocrystal [1]. In many cases, the sizedependent optical properties can be understood by considering the effects of quantum confinement on the band-gap transition, i.e., the electronic transition with lowest energy, and a few other closely related transitions [2]. However, quantum confinement will affect all electronic transitions throughout the entire Brillouin zone and, thus, decide the dielectric function of a semiconductor nanocrystal in a broad energy range. Despite the scientific and technological importance, only a few studies have been published in which the dielectric function of semiconductors nanocrystals is considered [3,4].Here, we present a study on the effects of quantum confinement on the dielectric function of PbSe nanocrystals in the energy range 1.5-4 eV. Bulk PbSe is a low band-gap semiconductor, with a band-gap transition of 0.26 eV at room temperature (at the L point of the Brillouin zone) and several other critical points (Van Hove singularities) at higher energy (at the L point and along the and directions). PbSe nanocrystals form an ideal case for this study: They can be electrodeposited on a gold substrate with good control over their size and shape [5], and the effects of quantum confinement are expected to be strong due to the low effective masses of the electrons and holes [6]. We studied the dielectric function ! of PbSe nanocrystals deposited on gold by spectroscopic ellipsometry. The dielectric function of the PbSe nanocrystals can be described by a sum of two Lorentz oscillators, as reported before for bulk PbSe [7]. This shape of the dielectric function is determined by an increase of the oscillator strength and the joint density of states near the Van Hove singularities along the directions and in the Brillouin zone [8]. We found that the resonance energies of these oscillators increase strongly relative to the bulk values when the nanocrystal height is less than 5 nm. This blueshift is accompanied by a change of the oscillator width and the oscillator strength. These results are compared with a tight-binding calculation of the dielectric function of an infinite PbSe sheet with v...

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Full-potential optical calculations of lead chalcogenides

Delin

Ravindran

Eriksson

et al. 1998

Int. J. Quant. Chem.

179

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We report on ab initio calculations of the optical properties of the lead chalcogenides PbS, PbSe, and PbTe performed with a relativistic full-potential linear muffin-tin orbital method within the local density approximation. Our calculated spectra are in excellent agreement with recent ellipsometry measurements. The origin of the peaks in the spectra is discussed, as well as the effects of increasing the chalcogen atomic

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Optical properties of PbSe

Cited by 77 publications

References 19 publications

Size-Dependent Optical Properties of Colloidal PbS Quantum Dots

Size-Dependent Optical Properties of Colloidal PbS Quantum Dots

Effect of Quantum Confinement on the Dielectric Function of PbSe

Full-potential optical calculations of lead chalcogenides

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