Thermalization of exciton states in silicon nanocrystals

Julsgaard, Brian; Lu, Ying‐Wei; Balling, P.; Larsen, A. Nylandsted

doi:10.1063/1.3251783

Cited by 4 publications

(2 citation statements)

References 16 publications

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“…Importantly, both experimental and theoretical efforts have begun to explore the fine structure of sustainable materials. On the experimental side, the nature of dark and bright exciton states corresponding to spin-allowed and forbidden transitions, respectively, has been investigated with temperature-dependent PL decay measurements for InP/ZnS, 250 ZnSe 251 and Si 252 NCs. Meanwhile, atomistic pseudopotential calculations have investigated the relationship between the magnitude of the bright/dark exciton splitting and the size of GaAs, InAs and Si QDs.…”

Section: Sustainable Future Quantum Technology With Colloidal Ncsmentioning

confidence: 99%

A sustainable future for photonic colloidal nanocrystals

2015

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Colloidal nanocrystals - produced in a growing variety of shapes, sizes and compositions - are rapidly developing into a new generation of photonic materials, spanning light emitting as well as energy harvesting applications. Precise tailoring of their optoelectronic properties enables them to satisfy disparate application-specific requirements. However, the presence of toxic heavy metals such as cadmium and lead in some of the most mature nanocrystals is a serious drawback which may ultimately preclude their use in consumer applications. Although the pursuit of non-toxic alternatives has occurred in parallel to the well-developed Cd- and Pb-based nanocrystals, synthetic challenges have, until recently, curbed progress. In this review, we highlight recent advances in the development of heavy-metal-free nanocrystals within the context of specific photonic applications. We also describe strategies to transfer some of the advantageous nanocrystal features such as shape control to non-toxic materials. Finally, we present recent developments that have the potential to make substantial impacts on the quest to attain a balance between performance and sustainability in photonics.

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Section: Sustainable Future Quantum Technology With Colloidal Ncsmentioning

confidence: 99%

A sustainable future for photonic colloidal nanocrystals

2015

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“…This means, that there must be spin-flip processes involved to reach the thermal equilibrium. Julsgaard et al have directly observed such scattering processes [29] and showed that the scattering time is around 0.1µs, indeed significantly smaller than the photoluminescence decay time.…”

Section: R R (T ) ∝ I (T ) · R Plmentioning

confidence: 97%

Optical Properties of Silicon Nanoparticles

Meier

Lorke

2012

Nanoparticles From the Gasphase

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This chapter reviews recent results on optical spectroscopy on silicon nanoparticles. The quantum confinement effect causing a spectral shift of the photoluminescence together with an intensity enhancement is discussed. The small spatial dimensions lead not only to a change of the electronic states, but affect also the vibronic spectrum as is seen in results on first-and second-order Raman scattering. Using time-resolved spectroscopy, the excitonic fine structure of silicon nanoparticles is investigated and a crossover of bright and dark exciton states is found. The analysis of the recombination dynamics allows to determine the size-dependence of the oscillator strength, which is in the order of 10 −5 and increases with decreasing particle size. Finally, we demonstrate an electroluminescence device based on silicon particles using impact ionization. IntroductionDue to the fact that most physical, chemical, and mechanical properties of nanostructured materials are determined by their structure, especially by geometry and size, many applications have been developed based on fundamental research in this field. The reasons for the novel effects in such nanomaterials are manifold, ranging from surface effects, e.g., in nanoparticle based gas sensors, to quantum confinement effects in sufficiently small structures. Among the inorganic materials used

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Quantum confinement in Si and Ge nanostructures: Theory and experiment

Barbagiovanni

Lockwood

Simpson

et al. 2014

Applied Physics Reviews

200

132

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The role of quantum confinement (QC) in Si and Ge nanostructures (NSs) including quantum dots, quantum wires, and quantum wells is assessed under a wide variety of fabrication methods in terms of both their structural and optical properties. Structural properties include interface states, defect states in a matrix material, and stress, all of which alter the electronic states and hence the measured optical properties. We demonstrate how variations in the fabrication method lead to differences in the NS properties, where the most relevant parameters for each type of fabrication method are highlighted. Si embedded in, or layered between, SiO 2 , and the role of the sub-oxide interface states embodies much of the discussion. Other matrix materials include Si 3 N 4 and Al 2 O 3. Si NSs exhibit a complicated optical spectrum, because the coupling between the interface states and the confined carriers manifests with varying magnitude depending on the dimension of confinement. Ge NSs do not produce well-defined luminescence due to confined carriers, because of the strong influence from oxygen vacancy defect states. Variations in Si and Ge NS properties are considered in terms of different theoretical models of QC (effective mass approximation, tight binding method, and pseudopotential method). For each theoretical model, we discuss the treatment of the relevant experimental parameters. V

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Thermalization of exciton states in silicon nanocrystals

Cited by 4 publications

References 16 publications

A sustainable future for photonic colloidal nanocrystals

A sustainable future for photonic colloidal nanocrystals

Optical Properties of Silicon Nanoparticles

Quantum confinement in Si and Ge nanostructures: Theory and experiment

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