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Carrier multiplication in germanium nanocrystals

Light(Science & Applications) 2015年第1期4卷 498-503页

作者： Saba Saeed Chris de Weerd Peter Stallinga Frank CM Spoor Arjan J Houtepen Laurens DA Siebbeles tom gregorkiewicz Van der Waals-Zeeman Institute University of Amsterdam1098 XH AmsterdamThe Netherlands FCT-DEEI University of the Algarve8005-139 FaroPortugal Optoelectronic Materials Faculty of Applied SciencesDelft University of Technology2628 BL DelftThe Netherlands

Carrier multiplication is demonstrated in a solid-state dispersion of germanium nanocrystals in a silicon–dioxide *** is performed by comparing ultrafast photo-induced absorption transients at different pump photon energies below and above the threshold energy for this *** average germanium nanocrystal size is approximately 5–6 nm,as inferred from photoluminescence and Raman spectra.A carrier multiplication efficiency of approximately 190%is measured for photo-excitation at 2.8 times the optical bandgap of germanium nanocrystals,deduced from their photoluminescence spectra.

关键词： carrier multiplication germanium nanocrystals transient absorption

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Thermally stimulated exciton emission in Si nanocrystals

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Light(Science & Applications) 2017年第1期6卷 228-234页

作者： Elinore MLD de Jong Huub Rutjes Jan Valenta M Tuan Trinh Alexander N Poddubny Irina N Yassievich Antonio Capretti tom gregorkiewicz Van der Waals-Zeeman Institute University of AmsterdamScience Park 9041098 XHAmsterdamThe Netherlands Department of Chemical Physics and Optics Faculty of Mathematics and PhysicsCharles UniversityKe Karlovu 312116 Prague 2Czech Republic Department of Electrical Engineering and Computer Science University of Michigan2200 Bonisteel BlvdAnn ArborMI 48109USA Ioffe Institute Russian Academy of Sciences26 Polytechnicheskaya194021 St PetersburgRussia

Increasing temperature is known to quench the excitonic emission of bulk silicon,which is due to thermally induced dissociation of ***,we demonstrate that the effect of temperature on the excitonic emission is reversed for quantumconfined silicon *** laser-induced heating of silicon nanocrystals embedded in SiO2,we achieved a more than threefold(4300%)increase in the radiative(photon)emission *** theoretically modeled the observed enhancement in terms of the thermally stimulated effect,taking into account the massive phonon production under intense *** results elucidate one more important advantage of silicon nanostructures,illustrating that their optical properties can be influenced by *** also provide an important insight into the mechanisms of energy conversion and dissipation in ensembles of silicon nanocrystals in solid *** practice,the radiative rate enhancement under strong continuous wave optical pumping is relevant for the possible application of silicon nanocrystals for spectral conversion layers in concentrator photovoltaics.

关键词： micro-photoluminescence nanocrystal optical spectroscopy silicon thermal

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Surface brightens up Si quantum dots: direct bandgap-like size-tunable emission

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Light(Science & Applications) 2013年第1期2卷 242-247页

作者： Katerina Dohnalova Alexander N Poddubny Alexei A Prokofiev Wieteke DAM de Boer Chinnaswamy P Umesh Jos MJ Paulusse Han Zuilhof tom gregorkiewicz Van der Waals-Zeeman Institute University of AmsterdamNL-1098 XH AmsterdamThe Netherlands Laboratory of Organic Chemistry Wageningen University6703 HB WageningenThe Netherlands Department of Chemical and Materials Engineering King Abdulaziz UniversityJeddahSaudi Arabia Ioffe Physical-Technical Institute RAS 26 Polytechnicheskaya194021 Saint-PetersburgRussia Current address:MIRA Institute Department of Biomedical ChemistryUniversity of TwenteBuilding Zuidhorst EnschedeThe Netherlands

Colloidal semiconductor quantum dots(QDs)constitute a perfect material for ink-jet printable large area displays,photovoltaics,light-emitting diode,bio-imaging luminescent markers and many other *** this purpose,efficient light emission/absorption and spectral tunability are necessary *** are currently fulfilled by the direct bandgap ***-QDs could offer the solution to major hurdles posed by these materials,namely,toxicity(e.g.,Cd-,Pb-or As-based QDs),scarcity(e.g.,QD with In,Se,Te)and/or *** we show that by combining quantum confinement with dedicated surface engineering,the biggest drawback of Si—the indirect bandgap nature—can be overcome,and a‘direct bandgap’variety of Si-QDs is *** demonstrate this transformation on chemically synthesized Si-QDs using state-of-the-art optical spectroscopy and theoretical *** carbon surface termination gives rise to drastic modification in electron and hole wavefunctions and radiative transitions between the lowest excited states of electron and hole attain‘direct bandgap-like’(phonon-less)*** results in efficient fast emission,tunable within the visible spectral range by QD *** findings are fully justified within a tight-binding theoretical *** the C surface termination is replaced by oxygen,the emission is converted into the well-known red luminescence,with microsecond decay and limited spectral *** that way,the‘direct bandgap’Si-QDs convert into the‘traditional’indirect bandgap form,thoroughly investigated in the past.

关键词： direct bandgap optical spectroscopy optoelectronics organic capping silicon quantum dots tight binding model

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Neuronal photoactivation through secondharmonic near-infrared absorption by gold nanoparticles

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Light(Science & Applications) 2018年第1期7卷 79-91页

作者： Wieteke D.A.M.de Boer Jan J.Hirtz Antonio Capretti tom gregorkiewicz Mercè Izquierdo-Serra Shuting Han Christophe Dupre Yuriy Shymkiv Rafael Yuste NeuroTechnology Center Department of Biological SciencesColumbia UniversityNew YorkNY 10027USA Van der Waals–Zeeman Institute University of Amsterdam1098 XH AmsterdamNetherlands Present address:Laboratori de Fisiologia Molecular Departament de Ciències Experimentals i de la SalutUniversitat Pompeu FabraBarcelonaSpain

Optical activation of neurons requires genetic manipulation or the use of chemical photoactivators with undesirable side *** a solution to these disadvantages,here,we demonstrate optically evoked neuronal activity in mouse cortical neurons in acute slices and in vivo by nonlinear excitation of gold *** addition,we use this approach to stimulate individual epitheliomuscular cells and evoke body contractions in Hydra *** achieve this,we use a low-power pulsed near-infrared excitation at the double-wavelength of the plasmon resonance of gold nanoparticles,which enables optical sectioning and allows for high spatial precision and large penetration *** effect is explained by second-harmonic Mie scattering,demonstrating light absorption by a second-order nonlinear process,which enables photothermal stimulation of the *** approach also minimizes photodamage,demonstrating a major advancement towards precise and harmless photoactivation for neuroscience and human therapeutics.

关键词： activation harmonic absorption

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