Characteristic Electron Energy Loss Spectra Research Articles

Comparative analysis of characteristic electron energy loss spectra and inelastic scattering cross-section spectra of Fe

The inelastic electron scattering cross section spectra of Fe have been calculated based on experimental spectra of characteristic reflection electron energy loss as dependences of the product of the inelastic mean free path by the differential inelastic electron scattering cross section on the electron energy loss. It has been shown that the inelastic electron scattering cross-section spectra have certain advantages over the electron energy loss spectra in the analysis of the interaction of electrons with substance. The peaks of energy loss in the spectra of characteristic electron energy loss and inelastic electron scattering cross sections have been determined from the integral and differential spectra. It has been shown that the energy of the bulk plasmon is practically independent of the energy of primary electrons in the characteristic electron energy loss spectra and monotonically increases with increasing energy of primary electrons in the inelastic electron scattering cross-section spectra. The variation in the maximum energy of the inelastic electron scattering cross-section spectra is caused by the redistribution of intensities over the peaks of losses due to various excitations. The inelastic electron scattering cross-section spectra have been analyzed using the decomposition of the spectra into peaks of the energy loss. This method has been used for the quantitative estimation of the contributions from different energy loss processes to the inelastic electron scattering cross-section spectra of Fe and for the determination of the nature of the energy loss peaks.

Polarized spectral complexes of optical functions of monovalent mercury iodide

Spectral complexes of optical functions of monovalent mercury iodide Hg2I2 were determined for E ⊥ c and E || c polarizations in the range from 2 to 5.5 eV at 4.2 K. The permittivity and characteristic electron energy loss spectra were expanded in simple components with the determination of their main parameters, including the energy of the maximum and the oscillator strength. The calculations were performed based on known reflectance spectra. Computer programs based on Kramers–Kronig relations and the improved parameter-free method of Argand diagrams were used.

Indirect interband transitions in graphite with a wide quasigap

Sets of fundamental optical functions in the energy range of 0–40 eV for longitudinal indirect interband transitions in graphite with a quasi-gap up to 2.6 eV have been determined for the first time. Their structure and parameters depend strongly on the electron wave vector transfer q. The nature of the peaks and shoulders of these functions is explained within the model of theoretical shifted bands for four electron wave vector transfers q in a volume characteristic electron-energy losses for the Γ-P direction in the Brillouin zone. The calculations were performed on the basis of the known experimental volume characteristic electron-energy loss spectra of graphite in the range of 0–40 eV for |q| = 0.00, 0.375, 0.625, and 1.00 A−1 using a special software package.

Adsorbate-induced surface rearrangement of the system Pd/Mo(1 1 1)

The thickness effect of Pd-adlayer on thermal stability of the Mo(1 1 1) surface has been investigated. It is found for θ>3 ML that heating to T>700 K results in faceting of the type {2 1 1}. At 920 K a reversible transition from the faceted to the planar surface occurs, which is accompanied by meaningful changes in work function opposite in sign to those measured upon the irreversible surface evolution during heating a new layer. It is also found that the faceting process is accompanied by changes in characteristic electron energy loss spectra with the loss energy of the faceted surface higher by 0.7 eV than that of the planar one. The dependence of desorption energy has been determined and four adsorption states found with their related energies of 4.82, 4.47, 4.13 and 3.92 eV/atom, respectively, in the range 0< θ<3 ML.

Investigation of the extent, rate, and mechanisms of electron-stimulated modification of the C60 fullerite by EELS

A parameter representing the intensity ratio of the two features in the characteristic electron energy loss spectrum that are most sensitive to electron irradiation is proposed for use in characterizing the extent of electron-stimulated modification of fullerite. By normalizing this parameter, we succeeded in obtaining a universal scale for the extent of modification that can be unambiguously related to the π-electron density. The dose dependence of this parameter is shown to be described by one exponential, thus permitting one to conclude that both the polymerization and amorphization of the fullerite are dominated by one mechanism, namely, the formation of intermolecular chemical bonds, which is stimulated by valence-electron excitation. The rate of the electron-stimulated modification, or the dose susceptibility of the material, is defined through the derivative of this parameter. The dependence of this rate on the incident electron energy is obtained. It is shown that structural changes are mainly due to a swarm of numerous secondary and decelerated electrons rather than to the primary electron.

Effect of electron irradiation on the spectra of elementary excitations in C60 fullerite

Electron irradiation produces changes in the spectra of elementary excitations of C60 fullerite, which are manifested by decrease in the π-plasmon energy, bandgap width, and energies of the HOMO-LUMO and other molecular transitions, smoothening of the corresponding spectral features, and significant growth in the quasicontinuous low-energy background intensity, the latter being indicative of an increase in the conductivity. The observed “red shifts” are related to collectivization of a part of the π electrons, the formation of chemical bonds between adjacent molecules (polymerization), and the corresponding increase in the proportion of sp3-hybridized electrons. Characteristic electron energy loss (EEL) spectra of an intact fullerite sample non-perturbed by the polymerization process were measured. The EEL spectra of fullerite exhibit a multipole structure due to the (σ + π)-plasmon and reveal an exciton feature which is highly sensitive with respect to electron irradiation and can be used to characterize the initial fullerite structure and to indicate the polymerization onset.

Cs/GaAs(100) surface: Two-dimensional metal or Hubbard insulator?

The evolution of the characteristic electron energy loss spectra accompanying the deposition of cesium on GaAs(100) surfaces with various superstructural reconstructions is studied experimentally. It is shown that the appearance of loss peaks in the GaAs band gap for Cs coverages θCs>0.5 monolayers is due to resonances in the longitudinal and transverse polarizability of two-dimensional metallic clusters of adatoms.

CHARACTERISTIC ELECTRON ENERGY LOSS SPECTRA IN SiC BURIED LAYERS FORMED BY C+ IMPLANTATION INTO CRYSTALLINE SILICON

SiC buried layers were snythesized by a metal vapor vacuum arc ion source,with C+ ions implanted into crystalline Si substrates.According to X-ray photoelectron spectroscopy,the characteristic electron energy loss spectra of the SiC buried layers were studied.It was found that the characteristic electron energy loss spectra depend on the profiles of the carbon content,and correlate well with the order of the buried layers.

On the mechanisms of characteristic electron energy loss spectra of polymers

A transmission electron beam spectrometer has been constructed with which the angular distributions of electron energy losses in thin films ( approximately 150 nm) of polyethylene, polystyrene and evaporated carbon ( approximately 50 nm) have been studied. The results indicate that the broad energy loss around 20 eV, which is common to the three materials studied, may be explained in terms of inelastic collisions of beam electrons with the bound electrons of the valence state and generation of plasma oscillations.

Measurement and interpretation of the electron energy loss spectra of iron and its oxides

Abstract The characteristic electron energy loss spectra of high purity samples of iron and its oxides were measured using cpmbined electron microscopy and energy analysis. By comparing these with X-ray absorption spectra it was possible to identify the single electron excitation processes and to deduce the plasmon energy of the electrons in iron.

Characteristic electron energy losses in germanium

The characteristic electron energy loss spectrum of germanium was studied in a transmission type experiment as a function of the changes in structure due to electron bombardment. The structure of the material was characterized by electron micrograph and diffraction techniques. The electron energy loss spectrum of germanium was studied up to 45 eV, and loss peaks were observed at 15.7 eV and 31.6 eV as well as a 6 eV carbon loss. The positions of the most intense characteristic energy loss peak at 15.7 eV and its first multiple were constant for a large variation in the lattice parameters for the individual films.

Excitation of luminescence from KCl:Tl+, KBr:Tl+, and KI:Tl+ by slow electron impact

Luminescence of Tl+-doped KCl, KBr, and Kl evaporated thin films at 290 and 77 °K is excited by slow electron impact. Emission spectra at ≥ 15 eV excitation correspond to those observed under uv excitation, but they are insensitive to the electron energy. The excitation spectra resemble closely the characteristic electron energy loss spectra of the pure alkali halides, the latter being unchanged by 10−3 mole fraction of thallous halide. Of the three pure alkali halides, only KI emits intrinsic luminescence at 77°K and only KI:Tl+ emits both intrinsic and Tl+-characteristic luminescence at 77°K. The A, B, C, and D absorption bands of Tl+ overlap the lower part of the excitation spectrum for electron impact, but that is required by the energetics. All luminescence excitations, including those below the first optical exciton, appear to be intrinsic to the alkali halide. In that case, all excitations involve migration of excitons, including those below the first optical exciton.

Characteristic electron energy loss spectrum in tungsten single crystals.: V V Korablev, Fiz Tverd Tela, 12 (6), June 1970, 1638–1640 in Russian.

Characteristic electron energy loss spectrum in tungsten single crystals.: V V Korablev, Fiz Tverd Tela, 12 (6), June 1970, 1638–1640 in Russian.

The Characteristic Electron Energy Loss Spectra of Thallous Halides

The Characteristic Electron Energy Loss Spectra of Thallous Halides

Characteristic Energy Loss Spectra of II-VI Compounds

Characteristic electron energy loss spectra of some II-VI compounds, ZnS, ZnSe, ZnTe, CdS and CdSe, were measured up to about 25 eV by transmission of 40 keV electrons and compared with the energy loss function -Im[ e (ω) -1 ] calculated from optical measurements. Good agreements between them were found in the peaks from 0 eV to about 13 eV. Some of the characteristic energy losses were explained; losses at about 11∼12 eV are due to the excitations of the valence electron plasmons, those at about 14 eV and those at about 17 eV are due to the excitations of cation d electrons and of anion s electrons respectively.

Measurement of electron energy losses in strontium

Surface and volume plasmon energies of 3.6 ± 0.05 eV and 7.8 ± 0.1 eV are measured for strontium. Energy losses due to N I and N II III ionization are identified and a peak due to a polarization wave in the N II III band is identified in the characteristic electron energy loss spectrum.

The Characteristic Loss Spectra of the Second and Third Series Transition Metals

Characteristic electron energy loss spectra are presented for the second and third series transition metals Y, Zr, Nb, Mo, Rh, Pd, Ag, and Hf, Ta, W, Re, Ir, Pt, Au. An identification of most of the spectral features in terms of collective and individual particle excitations is made.

Determination of the electron energy losses in cesium

Surface and volume plasmon energies of 2.11 and 2.96 eV, and energy losses of 20.1 and 42.8 eV are measured in the characteristic electron energy loss spectra of cesium.

Optical Constants of Germanium

The authors have attempted to assess the disagreement of various investigators on the optical properties of germanium in the far uv. The analyis subjected the reported data, out to about 25 eV, to the following tests: (1) an internal consistency check when possible by applying the Kronig-Kramers dispersion relations to the optical constants; (2) an evaluation of the optical oscillator strength distribution for the spectrum under study; (3) correlation of the values of Im(l/*) from the optical data with the characteristic electron energy loss spectrum for the material; and (4) evaluation of the oscillator strength sum for the electron energy loss distribution. A set of optical constants derived from the characteristic electron energy loss data is presented and discussed. Also, an estimate of the source of errors incurred in the application of the Kronig-Kramers dispersion relations are given and discussed in terms of optical data.

Characteristic energy losses in layered metallic thin films

Characteristic electron energy loss spectra of layered films of Bi-Mg have been measured and a new loss has been found at 12.9 ± 0.2 eV. This loss can be interpreted as a surface plasma loss at the metal-metal interface. A surface loss in Al-Mg films was not reproducible, but a new loss was observed at 26.4 eV which can be interpreted as a single Al loss (15.4 eV) plus a single Mg loss (10.9 eV).