Search results for "optoelectronic"
showing 10 items of 2328 documents
Light field propagation by metal micro- and nanostructures
2001
The ability to sustain plasmon oscillations gives rise to unique properties of metal nanostructures, which can be exploited for the controlled manipulation of light fields on the nanoscale. In this context we investigate electromagnetic coupling effects within lithographically produced ensembles of gold nanoparticles with a photon scanning tunnelling microscope. To provide an interface between these nano-optical devices and classical far-field optics, we investigate surface plasmon propagation on microstructured metal thin films.
Nanocrystallization of amorphous alloys using microwaves:In situtime-resolved synchrotron radiation studies
2009
Important energy and time savings can be achieved with the thermal treatment of materials by replacing conventional heating methods with microwave heating. The nano- crystallization of Co-Fe-W-B amorphous alloy powders under microwave irradiation was followed for the first time by in situ time-resolved synchrotron radiation powder diffraction. It is shown that even a very short exposure to the electromagnetic field (single pulse microwave application) typically of the order of a few seconds is sufficient to obtain the bulk nano- crystalline state. A metastable high-temperature Co-W-B orthorhombic phase forms during the microwave heating, which gradually transforms to the tetragonal Co2B sta…
Acoustic properties of nanoscale oxide heterostructures probed by UV Raman spectroscopy
2007
We study high quality molecular-beam epitaxy grown BaTiO3/SrTiO3 superlat-tices using ultraviolet Raman spectroscopy. In the low energy spectral region, acoustic phonon doublets are observed. These are due to the artificial superlattice periodicity and consequent folding of the acoustic phonon dispersion. From the study of samples with different BaTiO3/SrTiO3 layer thicknesses the effective sound velocities within each of the layers are obtained.
Determination of defect content and defect profile in semiconductor heterostructures
2011
In this article we present an overview of the technique to obtain the defects depth profile and width of a deposited layer and multilayer based on positron annihilation spectroscopy. In particular we apply the method to ZnO and ZnO/ZnCdO layers deposited on sapphire substrates. After introducing some terminology we first calculate the trend that the W/S parameters of the Doppler broadening measurements must follow, both in a qualitative and quantitative way. From this point we extend the results to calculate the width and defect profiles in deposited layer samples.
Optical properties of the low-molecular amorphous azochromophores and their application in holography
2015
The films based on the low-molecular amorphous azochromophore 2-(3-(4-((4- (Ethyl(2-(trityloxy)ethyl)amino)phenyl)diazenyl)styryl)-5,5-dimethylcyclohex-2-enylidene) malononitrile (IWK-2M) were prepared. The optical properties of the material, such as transmittance and reflection spectra of the film, sensitivity to polarization holographic recording by two wavelengths (405 and 532 nm) were studied. The direct relief formation during the polarization holographic recording was explored, relief depth dependence on exposure and record beam intensity was investigated. The holographic matrix on this material base was produced without chemical etching process; the replication of holographic image w…
Luminescence properties of AlN nanostructures revealed under UV light irradiation
2007
The luminescence properties of the AlN nanostructures – nanorods and nanotips -revealed under the UV irradiation are similar to those of the AlN ceramics. Presumably they are induced by the recombination processes in the oxygen-related centers. All the studied luminescence processes (photoluminescence, thermoluminescence and optically stimulated luminescence) in the nanostructures occur mainly through the host lattice excitation. That may be explained by the smaller concentration of the defect centers and more perfect structure of the host lattice of the nanostructures compared to the ceramics. The small mutual differences revealed in the spectra and TL curves of the AlN nanotips and nanoro…
Millimeter wave absorption by confined acoustic modes in CdSe/CdTe core-shell quantum dots
2007
International audience; Taking advantage of the specific core-shell charge separation structure in the CdSe/CdTe core-shell Type-II quantum dots (QDs), we experimentally observed the resonant-enhanced dipolar interaction between millimeter-wave (MMW) photons and their corresponding (l = 1) confined acoustic phonons. With proper choice of size, the absorption band can be tuned to desired frequency of MMW imaging. Exploiting this characteristic absorption, in a fiber-scanned MMW imaging system, we demonstrated the feasibility of CdSe/CdTe QDs as the contrast agents of MMW imaging.
High-brilliance double-stage soft x-ray laser pumped by multiple pulses applied in grazing incidence
2014
A new compact scheme for a double-stage seeded x-ray laser is demonstrated. This laser is offering greatly improved beam quality and brilliance making it a useful tool for applications.
Gas-phase supersaturation effects on morphology properties of ZnO nano and microstructures grown by PVT
2016
A systematic study of the morphology evolution of ZnO nanostructures grown by physical vapour transport was carried out. The evolution of the shape with the growth time is shown to depend on the different gas-phase supersaturation and temperature conditions encountered in the crystallization zone of the tube furnace. The observed morphology transitions are discussed, and a growth model for ZnO nanostructures is given.
Thermal activated carrier transfer between InAs quantum dots in very low density samples
2010
In this work we develop a detailed experimental study of the exciton recombination dynamics as a function of temperature on QD-ensembles and single QDs in two low density samples having 16.5 and 25 dots/¼m2. We corroborate at the single QD level the limitation of the exciton recombination time in the smallest QDs of the distribution by thermionic emission (electron emission in transient conditions). A portion of these emitted carriers is retrapped again in other (larger) QDs, but not very distant from those emitting the carriers, because the process is limited by the diffusion length at the considered temperature.