A5078770002- Semiconductor Quantum Structures and Devices
- Quantum Dots Synthesis And Properties
- Quantum and electron transport phenomena
- GaN-based semiconductor devices and materials
- ZnO doping and properties
- Silicon Nanostructures and Photoluminescence
- Nanowire Synthesis and Applications
- Strong Light-Matter Interactions
- Chalcogenide Semiconductor Thin Films
- Spectroscopy and Quantum Chemical Studies
- Advanced Semiconductor Detectors and Materials
- Electronic and Structural Properties of Oxides
- Semiconductor materials and devices
- Ga2O3 and related materials
- Photonic and Optical Devices
- Advanced Photocatalysis Techniques
- X-ray Diffraction in Crystallography
- TiO2 Photocatalysis and Solar Cells
- Laser-Matter Interactions and Applications
- Mechanical and Optical Resonators
- Nonlinear Optical Materials Studies
- Photochemistry and Electron Transfer Studies
- Copper-based nanomaterials and applications
- Quantum optics and atomic interactions
- Metal-Organic Frameworks: Synthesis and Applications
Institut de Physique et Chimie des Matériaux de Strasbourg
2012-2023
Centre National de la Recherche Scientifique
2011-2023
Université de Strasbourg
2010-2023
Canadian Nautical Research Society
2014-2015
Institut de Physique de Rennes
2009
Université de Rennes
2009
University of Trento
2004
Goethe University Frankfurt
1992
We present evidence of all-optical trion generation and emission in pristine single-walled carbon nanotubes (SWCNTs). Luminescence spectra, recorded on individual SWCNTs over a large cw excitation intensity range, show peaks redshifted with respect to the bright exciton peak. Clear chirality dependence is observed for 22 separate SWCNT species, allowing determination electron-hole exchange interaction binding energy contributions. data together ultrafast pump-probe experiments...
The surface polarization instabilities of a Coulomb-interacting electron-hole pair in spherical semiconductor quantum dot inside dielectric medium are studied. Two independent numerical solutions for the ground state presented which based on direct integration Schr\"odinger equation or diagonalization Hamiltonian matrix. For decreasing confinement potential at fixed radius, and radius potential, it is found that electron-hole-pair changes from volume state, both particles mostly dot, to...
We present a study of free carrier photogeneration and multicarrier bound states, such as biexcitons trions (charged excitons), in semiconducting single-walled carbon nanotubes. Pump-and-probe measurements performed with fs pulses reveal the effects strong Coulomb interactions between carriers on their dynamics. Biexciton formation by optical transition from exciton population results an induced absorption line (binding energy 130 meV). Exciton-exciton annihilation process is shown to evolve...
The near-field Coulomb interaction between a nano-emitter and graphene monolayer results in strong F\"orster-type resonant energy transfer subsequent fluorescence quenching. Here, we investigate the distance dependence of rate from individual, i) zero-dimensional CdSe/CdS nanocrystals ii) two-dimensional CdSe/CdS/ZnS nanoplatelets to monolayer. For increasing distances $d$, individual decays as $1/d^4$. In contrast, nanoplatelet deviates simple power law, but is well described by theoretical...
The luminescence of rare earths in CeO<sub>2</sub>is sensitized by intrinsic Ce<sup>3+</sup>ions.
We investigated the structural and optical properties of Eu-doped ZnO thin films made by sol-gel technique magnetron reactive sputtering on Si (100) substrate. The elaborated process are polycrystalline while show a strongly textured growth along c-axis. X-ray diffraction patterns transmission electron microscopy analysis that all samples free spurious phases. presence Eu2+ Eu3+ into matrix has been confirmed x-ray photoemission spectroscopy. This means small fraction Europium substitutes...
We collect a large number of experimental data from various sources to demonstrate that free-standing (FS) oxide-passivated silicon nanocrystals (SiNCs) exhibit considerably blueshifted emission, by 200 meV on average, compared those prepared as matrix-embedded (ME) ones the same size. This is suggested arise compressive strain, exerted their matrix, which plays an important role in light-emission process; this strain has been neglected up now opposed impact quantum confinement or surface...
We propose an analysis of the emission properties anatase and rutile titanium dioxide (TiO2) that emphasizes role strong electron-phonon interaction. performed measurements photoluminescence (PL) spectra bulk monocrystals under continuous wave-laser excitation their temperature dependence. show in both rutile, weakly bound self-trapped excitons are actually made out from carrier polarons give rise to a broad band visible spectral range. The thermal activation motion allows hopping distant...
Porous silicon grains embedded in the phosphorus doped SiO2 matrix exhibit improved photoluminesce properties and better stability comparison with native porous samples. We have tested this material for presence of room temperature optical amplification under femtosecond (100 fs, 395 nm) excitation. Combined variable stripe length shifted excitation spot experiments reveal positive gain, net modal gain coefficient reaching 25 cm−1 at a pump intensity 1.1 W/cm2 (mean power). The spectrum is...
The present study focuses on the structural and optical properties of ZnO thin films fabricated by sol-gel process spin coated onto Si (100) quartz substrates. have a hexagonal wurtzite structure with grain size about 50 nm. x-ray photoelectron spectroscopy measurements reveal presence Zn2+ zinc hydroxyl groups at film. Optical were studied photoluminescence (PL) absorption low room temperatures. spectrum is dominated sharp excitonic peak At temperature, PL observations show two transitions:...
Silicon nanocrystals (SiNCs) smaller than 5 nm are a material with strong visible photoluminescence (PL). However, the physical origin of PL, which, in case oxide-passivated SiNCs, is typically composed slow-decaying red–orange band (S-band) and fast-decaying blue–green (F-band), still not fully understood. Here we present interpretation F-band based on results an experimental study, which combine temperature (4–296 K), temporally (picosecond resolution) spectrally resolved luminescence...
We report on a study of the spin coherence and formation dynamics charged excitons in p-doped ${\mathrm{C}\mathrm{d}\mathrm{T}\mathrm{e}/\mathrm{C}\mathrm{d}}_{1\ensuremath{-}x\ensuremath{-}y}{\mathrm{Mg}}_{x}{\mathrm{Zn}}_{y}\mathrm{Te}$ quantum well by time-resolved photoluminescence under strictly resonant excitation either neutral or exciton transition. The analysis decay polarization oscillation this when transverse magnetic field is applied allows us to conclude that via an state does...
When using 100 fs light pulses with 2 eV photon energy, the degenerate two-photon absorption process in bulk wurtzite CdS exhibits a saturation behavior intensity of 65 GW/c${\mathrm{m}}^{2}$. This observation is possible because optical pulse duration shorter than 350 thermalization time photocreated carriers their bands that we measured. From an averaged carrier--LO-phonon interaction deduced which order 25 fs. Examination band structure and electronic state density shows this due to...
The present study focused on ZnO thin films fabricated by sol–gel process and spin coated onto Si (1 0 0) quartz substrates. have a hexagonal würtzite structure with grain diameter about 50 nm. Optical properties were determined photoluminescence (PL) absorption spectroscopy. spectrum is dominated sharp excitonic peak at room low temperatures. At temperature, two transitions observed PL. One near to the prohibited energy band in ultraviolet (UV) region other centered 640 nm, characteristic...
The influence of high-energy grinding on the photocatalytic activity nanocrystalline titania (TiO2) powders was investigated. Either in gas or liquid reactions, is observed to decrease with milling time. structural and surface characterizations showed that catalytic not correlated induced transformation anatase TiO2 into rutile via high-temperature high-pressure phase TiO2-II but introduction defects amorphization nanocrystals (nc). This has been change photoluminescence properties powders....
Sputtered ZnO thin films doped with Nd present efficient down-shifting properties.
To investigate the properties of a two-dimensional carrier gas at intermediate densities, we perform picosecond transient four-wave mixing experiments on trions (charged excitons) and neutral excitons in modulation p-doped ${\mathrm{C}\mathrm{d}\mathrm{T}\mathrm{e}/\mathrm{C}\mathrm{d}}_{1\ensuremath{-}x\ensuremath{-}y}{\mathrm{Mg}}_{x}{\mathrm{Zn}}_{y}\mathrm{Te}$ quantum wells. The determination trion exciton dephasing rates reveals localization both holes potential fluctuations induced by...
Oligophenylenevinylene (OPV) tetracarboxylate luminescent ligand 5 has been synthesized and used for the design of a new Ni(II) layered organic−inorganic compound (8) obtained by reaction with nickel(II) nitrate hexahydrate. The hybrid 8 characterized powder X-ray diffraction its magnetic properties have investigated as function temperature. structure consists stacking ferromagnetic based layers at ca. 29 Å apart. A 3D order occurs TC = 9.5 K. study temperature dependence OPV-based shows...
Silicon nanocrystals (Si-ncs) of sufficiently small size, emitting luminescence at short wavelengths (which implies the occurrence quasi-direct radiative recombination) and being densely packed in a planar thin film ensures stimulated emission (StE) lifetime) can become suitable active material for observation StE visible region. In this paper, we describe fabrication method nanostructures type, based on enhanced electrochemical etching silicon wafers followed by embedding porous grains into...
We report the observation of positive optical gain in silicon nanocrystals (Si-nc) embedded nitride measured by variable stripe length technique. evidence onset stimulated emission and coefficients up to 52 cm−1 at highest excitation power (6.5 W/cm2). Photoluminescence dynamics presents two distinct recombination lifetimes nanosecond microsecond ranges. This was interpreted terms fast carrier trapping nitrogen-induced localized states Si-nc surface subsequent slow radiative recombination,...
Embedding luminescent rare earth ions into transparent oxides such as ZnO is a well-known approach to functionalize the material by adding photon-management properties. In this paper we present detailed study of luminescence properties and energy level structure Pr3+ Yb3+ embedded in thin films deposited magnetron reactive sputtering. Careful photoluminescence excitation spectra allowed identifying locating almost all excited levels ions. Thus, an complete electronic diagram these crystal...