Спектроскопия потерь энергии отраженных электронов γ-Fe-=SUB=-2-=/SUB=-O-=SUB=-3-=/SUB=-

The reflection electron energy losses spectra, obtained in a wide primary electron energy range of 200 - 3000 eV, are investigated. From these experimental spectra, for each primary electron energy, the spectra of the inelastic scattering cross section of electrons are calculated as the dependence of the product of the inelastic electron mean free path and the differential inelastic scattering cross section of electrons on the electron energy loss. The analysis of the fine structure of the reflection electron energy losses was carried out by decomposing the electron energy losses spectra in the region of energy losses of valence electrons into elementary peaks. A relationship is established between each of their elementary peaks with single and multiple energy losses due to the excitation of bulk and surface plasmons and interband transitions of electrons from the valence band to free states above the Fermi level. The analysis of the obtained results was carried out on the basis of experimental and theoretical literature data on the band structure of  Fe2O3.

Theoretical Simulation of Backscattering Electron Coefficient for SixGe1-x/Si Heterostructure as a Function of Primary Electron Beam Energy and Ge Concentration

This study aims to investigate the backscattering electron coefficient for SixGe1-x/Si heterostructure sample as a function of primary electron beam energy (0.25-20 keV) and Ge concentration in the alloy. The results obtained have several characteristics that are as follows: the first one is that the intensity of the backscattered signal above the alloy is mainly related to the average atomic number of the SixGe1-x alloy. The second feature is that the backscattering electron coefficient line scan shows a constant value above each layer at low primary electron energies below 5 keV. However, at 5 keV and above, a peak and a dip appeared on the line scan above Si-Ge alloy and Si, respectively, close to the interfacing line. Furthermore, the shape and height of peak and dip broadening depend on the primary electron energy and incidence position with respect to the interfacing line. The last feature is that the spatial resolution of the backscattered signal at the interfacing line is improving by decreasing the primary electron energy (below 5 keV) and the shared element (Si) concentration. On the other hand, a poor compositional contrast has been shown at low primary electron energy below 5 keV. For energies above 5 keV, the spatial resolution becomes weak. These results can be explained by the behavior of the incident electrons inside the solid (interaction volume), especially at a distance close to the interfacing line and their chance to backscatter out of the sample. In general, a good compositional contrast with a high spatial resolution can be achieved at primary electron energy equal to 1 keV. Keywords: Monte Carlo model, Backscattering electron coefficient, Si-Ge/Si, Elastic scattering, Spatial resolution, Compositional contrast.

Ionization effects produced in diamonds subjected to mono-energetic β -ray bombardment

The ionization produced within diamond specimens by the passage of high-energy β -rays has been investigated using the methods of conduction pulse counting, and a new technique has been developed to enable pulse-height spectra to be taken, rapidly and in quick succession, under widely different experimental conditions. It is shown that only a small proportion of the incident β -rays may dissipate their total energy within the specimen and that pulse-height spectra can be interpreted successfully only when a conduction pulse is related to the energy lost by the electron producing it. Under conditions of saturation field strength and low crystal polarization, the conduction pulse magnitude is proportional to the energy dissipated. The mean value of energy per ion pair is thus independent of the primary electron energy and the experimental value of 20 eV is shown to be remarkably consistent between diamond specimens. This value differs from the previously accepted value of 10 eV and, if used in preference to 10 eV, removes many apparent anomalies from previously published work. A theory is outlined in which it is proposed that the degradation of the primary electron energy takes place principally by interaction with the valence electrons of the crystal. The mean energy per ion pair depends, therefore, not only on the width of the forbidden gap in the solid, as previously suggested, but also on the width of the valence band and particularly on the position of the maximum in the density of states curve within the valence band. The available data for diamond suggest a value of approximately 18 eV for the mean ionization energy. This value is consistent with the experimental value from the maximum pulse height under saturation conditions. The finite breadth of the pulse spectra, however, can be explained only by some charge-reducing process occurring after the total dissipation of the incident energy. The process is tentatively linked with the scintillation response of the diamond crystal. Finally, criteria are suggested by which the conduction pulse response of various solids may be predicted.