Search results for "Diffraction"
showing 10 items of 1584 documents
Defects at the TiO2(100) surface probed by resonant photoelectron diffraction.
2006
We report photoelectron diffraction (PED) experiments of weakly sub-stoichiometric TiO 2 (100) rutile surfaces. Apart from standard core-level PED from the Ti-2p3/2 line, we have studied valence band PED from the defect induced Ti-3d states in the insulating band gap. For maximum yield, the latter were resonantly excited at the Ti-2p absorption edge. The PED patterns have been analyzed within the forward scattering approximation as well as by comparison with simulated PED patterns obtained in multiple scattering calculations. The analysis shows that the defect induced Ti-3d charge is mainly located on the second layer Ti atoms. © 2007 Elsevier B.V. All rights reserved.
Defect States at theTiO2(110)Surface Probed by Resonant Photoelectron Diffraction
2008
The charge distribution of the defect states at the reduced ${\mathrm{TiO}}_{2}(110)$ surface is studied via a new method, the resonant photoelectron diffraction. The diffraction pattern from the defect state, excited at the $\mathrm{Ti}\mathrm{\text{\ensuremath{-}}}2p\mathrm{\text{\ensuremath{-}}}3d$ resonance, is analyzed in the forward scattering approach and on the basis of multiple scattering calculations. The defect charge is found to be shared by several surface and subsurface Ti sites with the dominant contribution on a specific subsurface site in agreement with density functional theory calculations.
Diffraction by fractal metallic supergratings.
2007
The reflectance of corrugated surfaces with a fractal distribution of grooves is investigated. Triadic and polyadic Cantor fractal distributions are considered, and the reflected intensity is compared with that of the corresponding periodic structure. The self-similarity property of the response is analyzed when varying the depth of the grooves and the lacunarity parameter. The results confirm that the response is self-similar for the whole range of depths considered, and this property is also maintained for all values of the lacunarity parameter. © 2007 Optical Society of America. Fil: Skigin, Diana Carina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación…
Characterization By Electroreflectance Of Thin Films And Thin Film Interfaces In Layered Structures.
1987
This paper reports investigations of ZnS quasi-amorphous films by electroreflectance (ER). The films were produced by thermal evaporation and their structure determined by electron diffraction. A voltage Vo cos cut was applied through the film with two evaporated Al electrodes. A lock-in amplifier gave 2 signals, Sf at f=ω/2π frequency and S2f at 2f frequency. The S2f spectrum, characteristic of the centrosymmetric bulk component of the film, reveals tails of localized states typical of amorphous semi-conductors. The Sf spectrum, characteristic of the interface layers with broken centro-symmetry, reveals tails of impurity levels which we attributed to diffusion of the electrode metal into t…
Optimization of thermal coefficient of electrical resistivity of Co-Ti-Si thin films due to laser-induced chemical reactions
2001
The CO2 laser induced optimization of the thermal coefficient of electrical resistivity in Co-Ti-Si thin films is realized. The X-ray diffraction studies of the annealed Co- Ti-Si films confirm that the changes of electrical properties are related to forming a small structure of crystalline compounds Ti5Si3 and CoSi2 in an amorphous matrix.
Magnetic and structural properties of the nanostructured Fe 1–x Si x system with x = 0.1, 0.2 and 0.3, mechanical alloyed and sintered
2007
The magnetic and structural properties of the nanostructured system Fe1–xSix with x = 0.1, 0.2 and 0.3 were studied by X-Ray diffraction (XRD), SEM, and Mossbauer Spectrometry (MS). The samples were prepared by compacting and sintering at two temperatures, 900 and 1000 uC, from powders obtained by means of two procedures: by elemental mixing of Fe and Si powders and by mechanical alloying (MA). For samples obtained from mixed powders and sintered at 900 and 1000 uC, XRD and MS show the presence of pure iron and silicon, indicating that these conditions do not favor alloying, except for the sample with 30 at.% and 1000 uC, for which, besides of iron and silicon patterns, the DO3 and FeSi pha…
128-Channel Silicon Strip Detector Installed at a Powder Diffractometer
2004
Silicon strip detectors represent a new class of one-dimensional position-sensitive single photon counting devices. They allow a reduction of measurement time at the powder diffractometers by a factor up to 100 compared to instruments with a single counter, while maintaining comparable count statistics. Present work describes a 128-channel detector working with a standard diffractometer. The detector is 12.8 mm long and covers the angular range of 3.2 deg. We discuss the diffraction geometry in real and reciprocal space, the FWHM of diffraction peaks, and the background level. Measurements were made on standard samples and on complex samples of industrial importance (e. g., portland clinker…
Controlling the Formation of Sodium/Black Phosphorus IntercalationCompounds Towards High Sodium Content
2021
The solid-state synthesis of pure sodium-black phosphorus intercalation compounds (Na-BPICs) has been optimized in bulk for two stoichiometric ratios. Specifically, in-situ X-Ray diffraction (XRD) allowed the precise identification of the optimal temperature range for the formation of Na-BPICs: 94°C–96°C. Moreover, as the undesired formation of Na3P takes place at this very same range, we succeeded in introducing a new synthetic route based on a fast-thermal ball milling implementation that results in the bulk production of BPIC without Na3P in 9 out of 10 cases. Finally, by combining XRD, Raman spectroscopy, and DFT calculations we developed a new structural model for Na-based BPICs showin…
COMPARING PARTICLE SIZE DISTRIBUTION ANALYSIS BY SEDIMENTATION AND LASER DIFFRACTION METHOD
2009
In this paper a brief review of the laser diffraction method is firstly carried out. Then, for 30 soil samples having a different texture classification sampled in Sicilian basin, a comparison between the two techniques is developed. The analysis demonstrated that the sand content measured by Sieve-Hydrometer method can be assumed equal to the one determinated by laser diffraction technique while an overestimation of the clay fraction measured by Sieve-Hydrometer method respect to laser diffraction technique was obtained. Finally a set of equations useful to refer LD measurements to SH method was proposed.
Comparison between grain-size analyses using laser diffraction and sedimentation methods
2010
A comparison between laser diffraction method (LDM) and the sieve-hydrometer method (SHM) was carried out for 228 soil samples representing a different texture classification sampled in a Sicilian basin. The analysis demonstrated that the sand content measured by SHM can be assumed equal to that determined by LDM technique, while the clay fraction measured by LDM was lower than that measured by the SHM. A set of equations to transform LDM results to SHM results was proposed. The influence of the LDM measurements of clay on the estimated percentage of silt + very fine sand particles (particle diameter ranging from 0.002 mm to 0.1 mm), which is useful for estimating soil erodibility, was also…