Etudes des proprietes physiques par spectroscopie magneto-optique de couches minces d'oxydes magnetiques prepare par depot laser pulse.

Single layers and the multilayers of magnetic oxides prepared by pulsed laser deposition were studied by magneto-optical spectroscopy in the spectral range of 1,2 eV to 5,0 eV in polar Kerr configuration. Nickel ferrite (NiFe2O4) single layers were chosen as a model system to study the combined contributions of the light propagation in the layer and of the surface reflection. The dielectric tensor of NiFe2O4 was determined by optical and magneto-optical ellipsometry on a natural facet of a single crystal. Simultaneous presence of the two contributions (propagation and reflection of light) make this non destructive technique of magneto-optical spectroscopy depth selective. This depth selectivity was verified also in the case of yttrium garnet (Y3Fe5O12) and samarium orthoferrite (SmFeO3) single layers.Available from STL Prague, CZ / NTK - National Technical LibrarySIGLECZCzech Republi

A 1D conical nanotubular TiO2/CdS heterostructure with superior photon-to-electron conversion

Herein, a new strategy to efficiently harvest photons in solar cells is presented. A solar cell heterostructure is put forward, based on a 1D conical TiO2 nanotubular scaffold of high aspect ratio, homogenously coated with a thin few nm layer of CdS light absorber using atomic layer deposition (ALD). For the first time, a large variety of conical nanotube layers with a huge span of aspect ratios was utilized and ALD was used for the preparation of a uniform CdS coating within the entire high surface area of the TiO2 nanotubes. The resulting 1D conical CdS/TiO2 tubular heterostructure acts as a sink for photons. Due to the multiple light scattering and absorption events within this nanotubular sink, a large portion of photons (nearly 80%) is converted into electrons. It is the combination of the scaffold architecture and the light absorber present on the high surface area as a very thin layer, the optimized charge transport and multiple optical effects that make this heterostructure very promising for the next generation of highly performing solar cells

Spectroscopic ellipsometry characterization of ZnO:Sn thin films with various Sn composition deposited by remote-plasma reactive sputtering

AbstractZnO:Sn thin films were deposited onto thermally oxidized silicon substrates using a remote plasma reactive sputtering. Their optical constants (refractive index n and extinction coefficient k) were determined from ellipsometric data recorded over a wide spectral range (0.05–6eV). Parametrization of ZnO:Sn complex dielectric permittivity consists of a parameterized semiconductor oscillator function describing the short wavelength absorption edge, a Drude oscillator describing free carrier absorption in near-infrared part of spectra and a Lorentz oscillator describing the long wavelength absorption edge and intra-band absorption in the ultra-violet part of the spectra. Using a Mott-Davis model, the increase in local disorder with increasing Sn doping is quantified from the short wavelength absorption edge onset. Using the Wemple-DiDomenico single oscillator model for the transparent part of the optical constants spectra, an increase in the centroid distance of the valence and conduction bands with increasing Sn doping is shown and only slight increase in intensity of the inter-band optical transition due to Sn doping occurs. The Drude model applied in the near-infrared part of the spectra revealed the free carrier concentration and mobility of ZnO:Sn. Results show that the range of transparency of prepared ZnO:Sn layers is not dramatically affected by Sn doping whereas electrical conductivity could be controlled by Sn doping. Refractive index in the transparent part is comparable with amorphous Indium Gallium Zinc Oxide allowing utilization of prepared ZnO:Sn layers as an indium-free alternative

Pulsed laser deposition and optical characterizations of the magnetic samarium orthoferrite

International audienc

Optical investigations of the quality and optical processes of photonic and plasmonic nanostructures

Optical scatterometry based on spectroscopic ellipsometry and other measurement techniques together with optical simualtions are used to analyze the quality of various nanostructure patterns and to study the optical behavior of selected photonic and plasmonic devices

Vascularization, High-Volume Solution Flow, and Localized Roles for Enzymes of Sucrose Metabolism during Tumorigenesis by Agrobacterium tumefaciens

Vascular differentiation and epidermal disruption are associated with establishment of tumors induced by Agrobacterium tumefaciens. Here, we address the relationship of these processes to the redirection of nutrient-bearing water flow and carbohydrate delivery for tumor growth within the castor bean (Ricinus communis) host. Treatment with aminoethoxyvinyl-glycine showed that vascular differentiation and epidermal disruption were central to ethylene-dependent tumor establishment. CO(2) release paralleled tumor growth, but water flow increased dramatically during the first 3 weeks. However, tumor water loss contributed little to water flow to host shoots. Tumor water loss was followed by accumulation of the osmoprotectants, sucrose (Suc) and proline, in the tumor periphery, shifting hexose-to-Suc balance in favor of sugar signals for maturation and desiccation tolerance. Concurrent activities and sites of action for enzymes of Suc metabolism changed: Vacuolar invertase predominated during initial import of Suc into the symplastic continuum, corresponding to hexose concentrations in expanding tumors. Later, Suc synthase (SuSy) and cell wall invertase rose in the tumor periphery to modulate both Suc accumulation and descending turgor for import by metabolization. Sites of abscisic acid immunolocalization correlated with both central vacuolar invertase and peripheral cell wall invertase. Vascular roles were indicated by SuSy immunolocalization in xylem parenchyma for inorganic nutrient uptake and in phloem, where resolution allowed SuSy identification in sieve elements and companion cells, which has widespread implications for SuSy function in transport. Together, data indicate key roles for ethylene-dependent vascularization and cuticular disruption in the redirection of water flow and carbohydrate transport for successful tumor establishment