Plasmon excitations in graphitic carbon spheres

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In ferroelectric materials, domain wall displacement plays a key role in the dielectric properties measured with respect to the driving field amplitude and frequency. The low to medium field dielectric response in many ferroic systems can be often described by classical Rayleigh model, which is rate-independent i.e., it depends only on the strength of ac signal. However experiments show that the nonlinear parameters are frequency dependent. Thus a more general approach, which can describe both purely nonlin

Three-dimensional (3D) electron microscopy (3DEM) aims at the determination of the spatial distribution of the Coulomb potential of macromolecular complexes. The 3D reconstruction of a macromolecule using single-particle techniques involves thousands of 2D projections. One of the key parameters required to perform such a 3D reconstruction is the orientation of each projection image as well as its in-plane orientation. This information is unknown experimentally and must be determined using image-processing t

We investigate the dielectric permittivity of SiO2 on Si(100) substrates using a first-principles approach. It is shown that both the static and high-frequency dielectric constants of the oxide overlayer increase when the oxide thickness is reduced. This behavior of the overlayer is found to be well reproduced by a classical two-layer model in which the pure oxide and the suboxide layer are treated as distinct dielectrics. Implications for interfaces between silicon and high-k gate oxides are discussed. (C)

Gold nanoparticles were supported on activated carbon fibers (ACF) using the aq. soln. of [Au(en)2]Cl3 via ion-exchange with surface hydroxyl groups followed by redn. in H2. The obtained catalysts were tested in CO oxidn. at room temp. Surface phenolic groups fix Au3+-ions leading to the formation of small Au particles (.apprx.5 nm) after the redn. with high activity in the reaction. AAS, TPD, HRTEM/EDAX and XPS were used for characterization of the catalysts and supports.

The damping rate of the n = 1 toroidal Alfven eigenmodes (TAE) mode in Ohmic-heated JET plasmas has been measured and compared with the prediction of the kinetic NOVA-K code, which includes electron and ion Landau damping of the global shear-Alfven wave field, collisional damping, and radiative damping. It was found that the calculated damping rate is too small to account for the measured value under these experimental conditions. A relatively weak dependence of the damping rate on the normalized Larmor rad

Localized direct electron heating (EH) by mode-converted (MC) ion cyclotron range of frequencies (ICRF) waves in D(H) tokamak plasmas has been clearly observed for the first time in Alcator C-Mod. Both on- and off-axis (high field side) mode conversion EH (MCEH) have been observed. The MCEH profile was obtained from a break-in-slope analysis of electron temperature signals in the presence of radio frequency shut-off. The temperature was measured by a 32-channel high spatial resolution (less than or equal to

The density functional theory (DFT) is a recognised method for the calculation of electronic properties of materials. As such it can also be used for the calculation of energy loss near edge structures. Some care has to be taken since the DFT is intended for ground state calculation. The effect of the core hole left by the excited electron is different in an insulator and in a metal and can be observed in both cases. For an insulator (MgO, Si), a supercell calculation is needed while in the case of copper,

TEM image simulations are used to couple the results from molecular dynamics (MD) simulations to experimental TEM images. In particular we apply this methodology to the study of defects produced during irradiation. MD simulations have shown that irradiation of FCC metals results in a population of vacancies and interstitials forming clusters. The limitation of these simulations is the short time scales available, on the order of 100 s of picoseconds. Extrapolation of the results from these short times to th

Backscattered electron (BSE) images of heat-cured concretes show alite grains surrounded by inner C-S-H gel of two distinct grey levels (referred to as two-tone inner C-S-H gel). The lighter rim forms at elevated temperature whereas the darker rim develops during subsequent exposure to moisture at 20 °C. This microstructural feature can potentially be used as an indicator to assess the curing history of a concrete. However, microstructural examinations of room-temperature concretes containing silica fume or

Using a combined experimental and theoretical approach, we address C 1⁢𝑠 core-level shifts in amorphous carbon. Experimental results are obtained by x-ray photoelectron spectroscopy (XPS) and electron-energy-loss spectroscopy (EELS) on thin-film samples of different atomic density, obtained by a pulsed-laser deposition growth process. The XPS spectra are deconvoluted into two contributions, which are attributed to sp2- and sp3-hybridized atoms, respectively, separated by 0.9 eV, independent of atomic densit

We investigate numerically the spectrum of plasmon resonances for metallic nanowires with a nonregular cross section, in the 20-50 nm range. We first consider the resonance spectra corresponding to nanowires whose cross sections form different simplexes. The number of resonances strongly increases when the section symmetry decreases: A cylindrical wire exhibits one resonance, whereas we observe more than five distinct resonances for a triangular particle. The spectral range covered by these different resona

Microcrystalline hydrogenated silicon films (muc-Si:H) have been deposited by a high current DC plasma in argon-silane-hydrogen mixtures at growth rates up to 10 nm/s and at substrate temperatures below 500 degreesC. Scanning electron microscopy, X-ray diffraction and FTIR analyses show that these films are highly crystallized. The surface morphology depends strongly on the experimental conditions and varies from a cauliflower structure to a prismatic one. The crystalline orientation of the films also chang

Plasmon excitations in graphitic carbon spheres

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Analysis of the non linear domain wall response in ferroelectric thin films

A Multiresolution Approach to Orientation Assignment in 3D Electron Microscopy of Single Particles

Dielectric effect of a thin SiO2 interlayer at the interface between silicon and high-k oxides

Gold nanoparticles on activated carbon fibers: Role of carbon surface groups for controlling the Au-particle size and catalytic activity

Experimental test of damping models for n=1 toroidal Alfven eigenmodes in JET

Ion cyclotron range of frequencies mode conversion electron heating in deuterium-hydrogen plasmas in the Alcator C-Mod tokamak

Improvement of energy loss near edge structure calculation using Wien2k

Correlating TEM images of damage in irradiated materials to molecular dynamics simulations

What causes differences of C-S-H gel grey levels in backscattered electron images?

𝑠⁢𝑝²⁢/𝑠⁢𝑝³ hybridization ratio in amorphous carbon from C 1⁢𝑠 core-level shifts: X-ray photoelectron spectroscopy and first-principles calculation

Plasmon resonances of silver nanowires with a nonregular cross section

Rapid deposition of hydrogenated microcrystalline silicon by a high current DC discharge