Tight-binding calculation of the optical absorption cross section of spherical and ellipsoidal silicon nanocrystals

Trani, F.; Cantele, Giovanni; Ninno, D.; Iadonisi, G.

doi:10.1103/physrevb.72.075423

Cited by 91 publications

(121 citation statements)

References 56 publications

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“…To the best of our knowledge, only a few attempts [12][13][14][15] have been made to perform the projection of states of finite systems from real to reciprocal space and vice versa so far. Therefore, a robust method which allows the band structure mapping from fully relaxed density functional theory (DFT) calculations of realistic Si NCs is required.…”

Section: Introductionmentioning

confidence: 99%

Theoretical analysis of electronic band structure of 2- to 3-nm Si nanocrystals

et al. 2013

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We introduce a general method which allows reconstruction of electronic band structure of nanocrystals from ordinary real-space electronic structure calculations. A comprehensive study of band structure of a realistic nanocrystal is given including full geometric and electronic relaxation with the surface passivating groups. In particular, we combine this method with large scale density functional theory calculations to obtain insight into the luminescence properties of silicon nanocrystals of up to 3 nm in size depending on the surface passivation and geometric distortion.We conclude that the band structure concept is applicable to silicon nanocrystals with diameter larger than ≈ 2 nm with certain limitations. We also show how perturbations due to polarized surface groups or geometric distortion can lead to considerable moderation of momentum space selection rules.

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Section: Introductionmentioning

confidence: 99%

Theoretical analysis of electronic band structure of 2- to 3-nm Si nanocrystals

et al. 2013

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“…The electronic structure of semiconductor nanocrystals has been previously investigated using a variety of theoretical approaches: (i) effective mass models and k · p methods 38-41 , often provide analytical solutions which are easier and more intuitive to understand than the numerical results of atomistic methods, such as (ii) the tight-binding method [42][43][44][45][46][47] , (iii) the semi-empirical pseudo-potential method, 48,49 , and (iv) fully self-consistent ab-initio methods, based on density functional theory [50][51][52][53][54][55][56][57] .…”

Section: Methodsmentioning

confidence: 99%

Origins of improved carrier multiplication efficiency in elongated semiconductor nanostructures

Sills

Califano

2015

Phys. Chem. Chem. Phys.

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Nanorod solar cells have been attracting a lot of attention recently, as they have been shown to exhibit a lower carrier multiplication onset and a higher quantum efficiency than quantum dots with similar bandgaps. The underpinning theory for this phenomenon is not yet completely understood, and is still the subject of ongoing study. Here we conduct a theoretical investigation into CM efficiency in elongated semiconductor nanostructures with square cross section made of different materials (GaAs, GaSb, InAs, InP, InSb, CdSe, Ge, Si and PbSe), using a single-band effective mass model. Following Luo, Franceschetti and Zunger we adopt the CM figure of merit (the ratio between biexciton and single-exciton density of states) as a measure of CM efficiency and investigate its dependence on the aspect ratio for both (a) constant cross section (i.e. varying the volume) and (b) constant volume (i.e., varying the cross section), by decoupling electronic structure effects from surface-related effects, increased absorption and Coulomb coupling effects. The results show that in both (a) and (b) cases elongation causes an increase in both single-and bi-exciton density of states, with the latter, however, growing much faster with increasing energy. This leads to the availability of more bi-exciton states than single-exciton states for photon energies just above the bi-exciton ground state and therefore suggests a higher probability of CM at these energies for elongated structures. Our results therefore show that the origin of the observed decrease of the CM threshold in elongated structures can be attributed purely to electronic structure effects, paving the way to the implementation of CM-efficiency-boosting strategies in nanostructures based on the lowering of the CM onset.

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“…As the later comparison with experimental data will show, this is still sufficient for calculations of optical properties in the optical wavelength regime. Although the accuracy of tight-binding parametrization for a material in a fixed state or phase can, in principle, be improved by incorporating contribution of neighbours up to the third nearest neighbour (shown by Trani et al in [20]), such extension is not available for transferable tight-binding scheme applied in XTANT.…”

Section: Modelmentioning

confidence: 99%

“…Parameters F nn are elements of the oscillator strength matrix. Although this oscillator strength is not directly available in the tight-binding schemes, according to Trani et al, it can be approximately expressed via momentum matrix elements as [20]:…”

Section: Modelmentioning

confidence: 99%

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Transient Changes of Optical Properties in Semiconductors in Response to Femtosecond Laser Pulses

2016

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Abstract:In this paper we present an overview of our theoretical simulations on the interaction of ultrafast laser pulses with matter. Our dedicated simulation tool, X-ray induced Thermal And Non-thermal Transitions (XTANT) can currently treat semiconductors irradiated with soft to hard X-ray femtosecond pulses. During the excitation and relaxation of solids, their optical properties such as reflectivity, transmission and absorption, are changing, affected by transient electron excitation and, at sufficiently high dose, by atomic relocations. In this review we report how the transient optical properties can be used for diagnostics of electronic and structural transitions occurring in irradiated semiconductors. The presented methodology for calculation of the complex dielectric function applied in XTANT proves to be capable of describing changes in the optical parameters, when the solids are driven out of equilibrium by intense laser pulses. Comparison of model predictions with the existing experimental data shows a good agreement. Application of transient optical properties to laser pulse diagnostics is indicated.

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Tight-binding calculation of the optical absorption cross section of spherical and ellipsoidal silicon nanocrystals

Cited by 91 publications

References 56 publications

Theoretical analysis of electronic band structure of 2- to 3-nm Si nanocrystals

Theoretical analysis of electronic band structure of 2- to 3-nm Si nanocrystals

Origins of improved carrier multiplication efficiency in elongated semiconductor nanostructures

Transient Changes of Optical Properties in Semiconductors in Response to Femtosecond Laser Pulses

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