Focusing of electrons reflected from layered crystal

The mechanism of the formation of the diffraction patterns upon inelastic reflection of mean-energy electrons from the VSe₂(0001) layered crystal has been investigated. It is found that the strong scattering of electrons by short atomic chains of the Se-V-Se layer triads leads to the weakening of electron focusing and the enhancement of diffraction scattering in deeper layers, which gives rise to the Kikuchi lines. It is demonstrated that, at an energy of 2 keV, the diffraction pattern is adequately described by the cluster model of single scattering. The atomic structure of thin near-the-surface layer of VSe₂ has been investigated by the computer simulation of experimental data.     

Influence of Nanoscale Titanium Dioxide Modifications on the Nano-Organization of Elastomers

Crystallography Reports - The diffraction patterns of fluorine rubbers ICF-26 and ICF-32 and vulcanizates based on ICF-32 with nanoscale titanium dioxide modifications are found to contain...     

Experimental study of the stability and reflective properties of depleted uranium thin films at a wavelength of 4.5 nm

A technology of depleted uranium thin films, which can be used as high-reflectivity X-ray mirrors at a wavelength of 4.5 nm, is presented. The coefficient of X-ray reflection by these mirrors varies from 90 to 10% at grazing angles between 1° and 10°. The stability of the reflection coefficients for 200-Å-thick depleted uranium films covered by a protective carbon layer 100 and 200 Å in thickness and for 200-Å-thick uranium-nickel films with a nickel content of 9 and 23 wt % is studied. A high-reflectivity mirror is fabricated with the goal of increasing the X-ray radiation intensity in RKK-1-100 X-ray calibration equipment. Advice on fabrication of X-ray mirrors based on depleted uranium films is given.     

Processes of silicide formation in the Fe/Si(111)7 × 7 system

The initial stages of the formation of iron silicides in the Fe/Si(111)7 × 7 system in the course of solid-phase epitaxy are investigated using high-resolution photoelectron spectroscopy (～100 meV) with synchrotron radiation. The spectra of the Si 2p core and valence-band electrons obtained after deposition of iron coverages of up to 28 monolayers on the surface of the sample and subsequent isochronous annealings at 650°C are measured and analyzed. It is shown that the first to form under Fe deposition is an ultrathin film of the metastable silicide FeSi with a CsCl-type structure, on which a layer of the Fe-Si solid solution with segregated silicon grows. At coverages in excess of 10 monolayers, an iron film grows on the surface of the sample. Annealing of a silicon crystal coated with a Fe layer leads to the sequential formation of two stable silicide phases, namely, the ?-FeSi and β-FeSi₂ phases, in the near-surface region of the sample. It is found that the process of solid-phase synthesis of the ?-FeSi phase passes through the stage of transformation of the iron film into the Fe-Si solid solution.     

Pyroelectric and piezoelectric properties of thin PZT films at the morphotropic phase boundary

It has been shown that, in polycrystalline thin PZT films with the Zr/Ti = 0.535/0.465 ratio of ions in octahedral positions of the perovskite structure, the permittivity and the pyroelectric and piezoelectric responses increase with increasing linear sizes of growth blocks to reach anomalously large values. It has been assumed that the observed effects originate from a combination of two factors, namely, the possible presence of the monoclinic phase and a well-developed domain structure in the films.     

Focusing of electrons reflected from a crystal with loss of energy

A study is made of the features arising in the spatial distributions of reflected electrons as a result of a focusing effect. Experiments are conducted on single-crystal Mo (100) with primary electron energies of 0.5–2 keV and detection of electrons which lose fixed amounts of energy up to 300 eV. An analysis of the data establishes the dependence of the electron focusing efficiency on the amount of energy loss. It is shown that when electrons are reflected with single losses through plasmon excitation, the magnitude of the effect is determined mainly by the average number of scattering atoms encountered by an electron along its path to the surface. When the energy losses are high, defocusing owing to multiple elastic and inelastic scattering of the electrons is found to predominate. Zh. Tekh. Fiz. 68, 128–133 (June 1998)     

1D-3D crossover in hopping conduction of carbynes

D.C. and A.C. conductivities of carbyne samples were studied over the temperature range 1.8–300 K at frequencies 10 MHz–1 GHz. It was established that a variation in the fraction of sp ² bonds in carbynes induces transition from one-to two-and then to three-dimensional conduction. In the one-dimensional hopping conduction regime, the resistivity of carbynes depends on temperature as ρ=ρ₀exp[(T ₀/T)^1/2], whereas Coulomb correlations are insignificant. The Hunt model of one-dimensional A.C. conductivity is experimentally confirmed.     

Low-frequency dynamic response of the bismuth strontium ferrite (Bi,Sr)FeO3−x

Broad-range measurements of the dynamic response of polycrystalline samples of the (Bi,Sr)FeO_3?x perovskite-like solid solution are performed over a frequency range from 10 Hz to 1 GHz at temperatures of 100–300 K for the first time. The colossal dielectric constant effect and the influence of electric contacts on the results of measurements are considered. It is shown that the frequency dependences of the permittivity and dynamic conductivity of (Bi,Sr)FeO_3?x samples can be described within the universal dielectric response model.