35 research outputs found
Localization of charge carriers in materials with high polaron concentration
Abstract The influence of polaron concentration on the type of transition from band to activate conductivity has been investigated. For a single polaron in the crystal lattice or for material with polaron concentration higher than the percolation threshold, such a transition is continuous, in accordance with theory. However, for intermediate cases this process becomes step-like, because the rapid increase of density of states at Fermi level leads to a change of polaron characteristics. These suppositions are illustrated by experimental results (XPS-spectra, crystal structure analysis, DC conductivity) for intercalation compounds based on titanium dichalcogenides.
The electronic structure formation of CuxTiSe2 in a wide range (0.04 < x < 0.8) of copper concentration
An experimental study of the electronic structure of copper intercalated
titanium dichalcogenides in a wide range of copper concentrations (x = 0.05 -
0.6) using the x-rays photoemission spectroscopy, resonant photoemission and
x-rays absorption spectroscopy has been performed. Negative energy shifts of
the Ti 2p and Se 3d core levels spectra and a corresponding decrease of the
photon energy in Ti 2p absorption spectra with increasing concentration of
copper have been found. Such sign-anomalous shifts may be explained by the
shielding effect of the corresponding atomic shells as a result of the dynamic
charge transfer during the formation of a covalent chemical bond between the
copper atoms and the TiSe2 matrix.Comment: 12 pages, 6 figure
Non-quasiparticle states in the core level spectra of ferromagnetic semiconductors and half-metallic ferromagnets
The Green's functions that determine x-ray spectra are calculated in the s-d
exchange model of a saturated conducting ferromagnet in the presence of the
core hole. A possibility to observe non-quasiparticle (NQP) states in the core
level (x-ray absorption, emission and photoelectron) spectroscopy is
demonstrated. It is shown that NQP contributions to resonant x-ray scattering
spectra can be considerably enhanced by core hole effects in comparison with
those to the density of states.Comment: 13 pages, 7 figures, final versio
ELECTRONIC STRUCTURE OF FeSi
The full set of high-energy spectroscopy measurements including X-ray
photoelectron valence band spectra and soft X-ray emission valence band spectra
of both components of FeSi (Fe K_beta_5, Fe L_alpha, Si K_beta_1,3 and Si
L_2,3) are performed and compared with the results of ab-initio band structure
calculations using the linearized muffin-tin orbital method and linearized
augmented plane wave method.Comment: 11 pages + 3 PostScript figures, RevTex3.0, to be published in
J.Phys.:Cond.Matte
Electronic structure of Co_xTiSe_2 and Cr_xTiSe_2
The results of investigations of intercalated compounds Cr_xTiSe_2 and
Co_xTiSe_2 by X-ray photoelectron spectroscopy (XPS) and X-ray emission
spectroscopy (XES) are presented. The data obtained are compared with
theoretical results of spin-polarized band structure calculations. A good
agreement between theoretical and experimental data for the electronic
structure of the investigated materials has been observed. The interplay
between the M3d--Ti3d hybridization (M=Cr, Co) and the magnetic moment at the M
site is discussed. A 0.9 eV large splitting of the core Cr2p{3/2} level was
observed, which reveals a strong exchange magnetic interaction of 3d-2p
electrons of Cr. In the case of a strong localization of the Cr3d electrons
(for x<0.25), the broadening of the CrL spectra into the region of the states
above the nominal Fermi level was observed and attributed to X-ray re-emission.
The measured kinetic properties are in good accordance with spectral
investigations and band calculation results.Comment: 14 pages, 11 figures, submitted to Phys.Rev.
COMPARISON OF SYSTEMS FOR REGISTRATION OF X-RAY SPECTRA AND IMAGES IN VARIOUS COMBINATIONS OF “DETECTOR-CAMERA” PAIR
An X-ray image registration system consisting of a detector, an optical lens and a digital video camera is described. The measurements were performed using detectors with different gain coefficients and two video cameras with different characteristics and pixel sizes.Работа выполнена в рамках государственных заданий Минобрнауки России (темы: “Спинˮ, г.р. № 122021000036-3; “Электронˮ, г.р. № 122021000039-4)
A LOW-INTENSITY X-RAY DETECTOR BASED ON MICROCHANNEL PLATES
The detector based on microchannel plates was designed to detect low-intensity X-ray radiation in the wavelength range 0.1 nm-0.7 nm in diffractometers and X-ray spectrometers. The secondary characteristic radiation of the samples is recorded in the X-ray spectrometer. A microchannel plates (MCP).Работа выполнена при финансовой поддержке Российского фонда фундаментальных исследований (проект № 20-02-00541 А)