Search results for "scanning"
showing 10 items of 1808 documents
Gallium nitride thin films as processed by several techniques: Their possible applications for PV-devices
2011
We present in this work the characterization studies carried on GaN — thin films as processed by the Close Spaced Vapor Technique (CSVT), Laser Ablation (LA), and Molecular Beam Epitaxy (MBE), under particular growth parameters for each of the three techniques. The films characterization was performed by x-ray diffraction (X-RD), Photoluminescence (PL), Raman spectroscopy, optical transmission, energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). With these results an analysis of the samples was done, with an aim for a possible application of these thin films for PV-devices.
Ge-doped silica nanoparticles: production and characterisation
2016
Silica nanoparticles were produced from germanosilicate glasses by KrF laser irradiation. The samples were investigated by cathodoluminescence and scanning electron microscopy, providing the presence of nanoparticles with size from tens up to hundreds of nanometers. The emission of the Germanium lone pair center is preserved in the nanoparticles and atomic force microscopy revealed the presence of no spherical particles with a size smaller than ~4 nm. The absorption coefficient enhancement induced by Ge doping is reputed fundamental to facilitate the nanoparticles production. This procedure can be applied to other co-doped silica materials to tune the nanoparticles features.
Alkoxide-intercalated CoFe-layered double hydroxides as precursors of colloidal nanosheet suspensions: structural, magnetic and electrochemical prope…
2014
Alkoxide-intercalated CoFe-layered double hydroxides (CoFe–LDHs) were synthesized via the non-aqueous methanolic route. According to powder X-ray diffraction and field emission scanning electron microscopy, they exhibit a nanosized plate-like morphology with a basal space of 9.21 A. The hydrolysis of the material in water leads to colloidal suspensions of nanosheets with lateral dimensions of about 20 nm and thicknesses of ca. 4 nm as demonstrated by atomic force microscopy and dynamic light scattering. Atomic resolution scanning transmission electron microscopy combined with electron energy-loss spectroscopy confirm the high crystalline quality of the crystals and the proper Co/Fe stoichio…
Near-field scanning optical microscopy to study nanometric structural details of LiNbO3 Zn-diffused channel waveguides
2008
A near-field scanning optical microscope (NSOM) is used to perform structural and optical characterization of the surface layer after Zn diffusion in a channel waveguide fabricated on lithium niobate. A theoretical approach has been developed in order to extract refractive index contrast from NSOM optical transmission measurements (illumination configuration). As a result, different solid phases present on the sample surface can be identified, such as ZnO and ZnNb2O6. They appear like submicrometric crystallites aligned along the domain wall direction, whose origin can be ascribed to some strain relaxation mechanism during the annealing process after Zn diffusion. Jose.Canet-Ferrer@uv.es
Structural, electronic, and magnetic properties of pseudomorphic CrFe nanostripes on W(110)
2007
We have grown pseudomorphic binary ${\mathrm{Cr}}_{1\ensuremath{-}x}{\mathrm{Fe}}_{x}$ alloy monolayers and sequences of Cr and Fe nanostripes on W(110) by molecular-beam epitaxy in ultrahigh vacuum. By coadsorption of Cr and Fe a pseudomorphic random CrFe alloy grows on the W(110) substrate. At a substrate temperature of $700\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ the CrFe alloy forms monolayer stripes in the step flow growth mode. We have measured magnetic properties of the monolayer alloy for $0.75\ensuremath{\leqslant}x\ensuremath{\leqslant}1$ using Kerr magnetometry. At a constant relative temperature $t=T∕{T}_{C}$ the saturation value of the Kerr rotation shows a maximum at $x=0.95$ an…
Porous structure of Purevision™ versus Focus® Night&Day™ and conventional hydrogel contact lenses
2002
The surface and bulk structures of hydrogel contact lenses that contain siloxane moieties, Purevision™ (balafilcon A) and Focus®Night&Day™ (lotrafilcon A), were investigated. Standard hydrogel lenses of low (Seequence®), medium (Acuvue®), and high water content (Precision UV®) were used as controls. All the lenses were dehydrated in a series of ethanol solutions of increased concentration, critical-point dried in CO2, and sputter coated with gold/palladium before they were examined by scanning electron microscopy. Of all lenses examined, only the balafilcon lenses presented, in addition to the polymer network porosity characteristic of all hydrogels, a macroporous structure that was observe…
Chemical hydrogels based on a hyaluronic acid-graft-α-elastin derivative as potential scaffolds for tissue engineering
2013
In this work hyaluronic acid (HA) functionalized with ethylenediamine (EDA) has been employed to graft α-elastin. In particular a HA-EDA derivative bearing 50 mol% of pendant amino groups has been successfully employed to produce the copolymer HA-EDA-g-α-elastin containing 32% w/w of protein. After grafting with α-elastin, remaining free amino groups reacted with ethylene glycol diglycidyl ether (EGDGE) for producing chemical hydrogels, proposed as scaffolds for tissue engineering. Swelling degree, resistance to chemical and enzymatic hydrolysis, as well as preliminary biological properties of HA-EDA-g-α-elastin/EGDGE scaffold have been evaluated and compared with a HA-EDA/EGDGE scaffold. T…
Magnetic Anisotropies and Coupling Mechanisms inFe/Mo(110)Nanostripes
2005
Using low-temperature (5 K) spin-polarized scanning tunneling microscopy, we have studied the morphology and magnetic properties of monolayer (ML) and double layer (DL) thick Fe nanowires grown by step flow on a Mo(110) single crystal. Magnetic contrast has been obtained using tungsten tips covered by Au/Co thin films. We find that the DL Fe nanowires, similarly to ML Fe nanowires, are perpendicularly magnetized. Because of the dipolar coupling, separated DL Fe nanowires are antiferromagnetically coupled. DL wires that are touching at step edges are ferromagnetically ordered due to direct exchange coupling. We measured the widths of the magnetic domain walls in the ML and DL Fe nanowires. T…
Effect of zinc concentration on the microstructure and relaxation frequency of Mn–Zn ferrites synthesized by solid state reaction
2013
Abstract Mn3Zn polycrystalline ferrites with Mn1−xZnxFe2O4 stoichiometry (x=0.59, 0.61, 0.65) were prepared by solid state reaction. These ferrites were heated at different temperatures. The cubic structure with space group Fd3m (Oh7) No. 227 was confirmed by the refinement of x-ray diffraction (XRD) powders through Rietveld´s method using fullprof. Scanning electron microscopy (SEM) results revealed for all compounds a non-homogeneous grain size and shape distribution, with a mean grain size of 9 μm. The Curie temperature Tc was found to decrease as the Zn concentration increases. The magnetic domain relaxation was investigated by inductance spectroscopy (IS). The relaxation frequency fr s…
Effect of antisite defects on the magnetic properties of ZnFe2 O4
2013
Magnetic zinc ferrite (ZnFe2O4) nanopowders were synthesized using the sol–gel autocombustion method. X-ray diffraction (XRD) and scanning electron microscopy (SEM) measurements demonstrated that thermal decomposition of the 1-mm-thick xerogel layers in air formed monophasic spinel ferrite nanopowders with a particle size less than 30 nm. X-ray photoelectron spectroscopy (XPS) showed that the obtained reaction product contained antisite defects, with zinc ions occurring at the octahedral sites of the spinel structure. The concentration of antisite defects or inversion degree decreased when the relatively low annealing temperature was increased from 150 to 500 °C. Overall, the obtained ZnFe2…