K. F. Minnebaev

Changes in the Composition and Surface Structure of Alloys in Regions with Varying Deformation

The change in the structure and composition of deformed regions hidden beneath the surface of samples are studied experimentally upon their identification by the method of successive processes of polishing and sputtering. Two present-day steel coins coated with different binary alloys, a 1-ruble coin (coated with the alloy Ni1%Fe) and a 50-kopeck coin (coated with the tompak alloy Cu10%Zn), and also a 5-kopeck coin minted in 1990 consisting of brass L60 are used as the samples. It is found that a change in the surface structure (different for the studied coins) and an increase in the light-component concentration take place in the region of increased deformation by pressing due to its diffusion to the side of greater deformation. The obtained results can be used for improving the means of determining hidden deformed regions using sputtering and stage-like analysis of the surface composition.

Anisotropy of secondary ion emission from a Ni4Mo single crystal

The azimuthal and polar angle distribution of Ni+ and Mo+ ions emitted from an ordered Ni4 Mo single crystal irradiated with 10-keV Ar+ ions was studied. Different azimuthal distributions for Ni+ and Mo+ ions emitted from the (001) Ni4Mo face were detected; emission maxima were observed in 〈 011 〉 and 〈 001 〉 directions for Ni+ and Mo+ ions, respectively. It was shown that polar distributions of nickel’s secondary ions vary with its energy. The observed systematic features were explained by correlated collisions in the upper layers of a Ni4Mo single crystal.

Features of the energy distribution of secondary particles upon the ion bombardment of graphite

The secondary emission of carbon atoms from the (0001) plane of graphite nanocrystallites bombarded with argon ions with energies of 1 and 10 keV and the incidence angle α = 45° is investigated. The unusual oscillating energy distributions of secondary C+ ions with main maxima Emax in the range of 40–60 eV and peaks corresponding to the energies E1 ≈ 20, 30, 70, 80, and 100 eV have been revealed. The C+ ion yield decreases, the energy spectrum increases, and the maximum Emax shifts to larger energies E1 with increasing emission angle (with respect to the normal to the surface). The secondary-ion emission from the (0001) face of graphite is numerically simulated with allowance for the charge exchange of secondary ions to obtain a qualitative explanation of the observed results.

Electron-beam charging of dielectrics preirradiated with moderate-energy ions and electrons

The effects of charging of dielectric targets irradiated with moderate-energy electrons in a scanning electron microscope are examined. Considerable differences in the kinetics of charging of the reference samples and the samples preirradiated with ions and electrons are reported. These differences are attributed to the processes of radiation-induced defect formation in Al2O3 (sapphire) and SiO2 that are, however, dissimilar in nature. The contributions of surface structure modification and changes in the electrophysical parameters of the surface (specifically, the charge spreading effect) are revealed. Critical doses of irradiation with Ar+ ions and electrons inducing active defect formation in dielectric targets and critical values of internal charge fields producing a significant contribution to the temporal parameters of Al2O3 and SiO2 charging are determined.

Feature of secondary ion emission at various temperature of irradiated copper single crystal

The difference between the forms and positions of the maximum of the energy spectrum of secondary 63Cu+ ions emitted from the (100) face of a Cu single crystal in close-packed <110> directions and between them at different target temperatures is revealed. For a sample at room temperature, it is established that the most probable ion energy Emax and the width h of the energy spectra at half-height increase with the polar emission angle, θ, measured from the normal to the surface. The opposite tendency, namely, a decrease in Emax with increasing θ, is obtained for ions emitted from a single crystal heated to several hundred degrees Celsius. Based on modern models of secondary ion emission, the observed regularities, which must be taken into account in the theoretical description of the process and in the practical application of secondary ions in mass spectroscopy, are discussed.

Secondary particle emission from a ferromagnetic binary compound

Secondary ion emission from an ion-bombarded binary compound in the ferro- and paramagnetic states has been studied using experimental methods and molecular dynamics simulations. The experiments were performed with a widely used NiPd binary compound, which was bombarded by obliquely incident 10-keV Ar ions. It is established that the intensity of Ni+ and Pd+ ion emission from a polycrystalline NiPd sample decreases significantly when it passes from the ferromagnetic to paramagnetic state. This effect is explained by a change in the surface binding energy and density of surface states at the Fermi level and by a cumulative process related to sputtering. The energies and directions of emission of secondary particles from poly- and single-crystalline NiPd samples in the ferromagnetic state have been jointly studied. It is established that the maximum of the polar angular distribution of secondary particles deviates toward the normal to the irradiated surface with a decrease in their energy. A difference in the azimuthal distribution of emitted Ni and Pd particles has been observed during the bombardment of a (001)NiPd crystal face and explained by specific features of correlated collisions. The best agreement of experimental data with the results of molecular dynamics simulations is obtained if the calculations are performed with allowance for an experimentally established modified composition of the three uppermost surface layers [39].

Secondary emission of carbon ions from graphite nanocrystallites

Emission of secondary C+ ions from the surface of well-oriented graphite nanocrystallites irradiated with 10 keV Ar+ ions has been studied. The energy distribution of emitted secondary ions has been measured. It has been found that the form of energy distribution and the energy corresponding to the maximum of distribution Emax depend on the polar angle θ of C+ ion emission. The linear dependence of energy in the maximum of energy spectrum of single-charged secondar y carbon ions on the polar angle of their emission Emax(θ) has been obtained. The mechanism responsible for the observed features of the energy spectra is discussed.

Angular distributions of sputtered particles from lithium-implanted aluminium and copper crystals☆

Abstract The anisotropy of angular distributions of sputtered ions from lithium-implanted aluminium and copper single crystals, measured by SIMS analysis, have been used to obtain information about the microstructure of the implanted layers. Sputtered Al + distributions from the {111} surface show three-fold symmetry with maximum intensity near the 〈110〉 and 〈100〉 directions respectively, while Li + distributions show maximum intensity only in the 〈100〉 directions. From {100] crystals the Al + distributions have four-fold symmetry while there are no preferential ejection directions for the Li + ions. This agrees conceptually with the fact that the implanted layer contains the ordered Al 3 Li (δ) phase, which has earlier been observed by TEM analysis on implanted samples. In contrast, a similar study of Li + implanted copper crystals shows that the implanted lithium is randomly located.

Influence of the magnetic phase transition on secondary ion emission from disordered Ni-Pd compounds of various compositions

Variations in secondary ion emission (SIE) from polycrystals of ferromagnetic disordered Ni-Pd compounds irradiated by argon ions with energy of 10 keV are studied experimentally. A considerable reduction in Ni+ and Pd+ ion emission upon transitioning from the ferromagnetic to the paramagnetic state is revealed for the following Ni-Pd compounds with various Curie points TC: NiPd (TC = 190°C), Ni5Pd (TC = 315°C), and NiPd5 (TC = 110°C). The observed reduction in SIE is attributed to variations in the surface binding energy and the density of electron states near the Fermi level.