The spectra of transmisson coefficients and absorption indices of single-domain and multidomain LaBGeO5 samples have been measured. It is shown that, to measure more exactly the optical rotation ρ, it is necessary to use the spectra of transmission coefficients not only for the cases of parallel and crossed polarizers but also at other angles between them. The obtained ρ values for both samples are described quite well by only dispersion using the Drude formula. This is in agreement with the fact that the ρ value should not change during transition to the single-domain state of the crystal at a given symmetry (P31 in the ferroelectric phase and P3121 in the paraelectric phase). It is shown that the Cherenkov-type second harmonic generation (SHG) is observed only in a polydomain sample, while the second-harmonic radiation is not polarized. The domain structure of the samples was observed by scanning electron microscopy and piezoelectric force microscopy. The presence of a labyrinth-like domain structure was shown for the multidomain sample, whereas for a single-domain sample no changes in contrast were observed within the scanned region.

The structure and optical properties of crystals from the langasite family (La1 - xNdх)3Ga5SiO14 with different Nd content were investigated. The rotation of the light polarization plane, ρ, was calculated for these crystals from measured transmission spectra in polarized light. It is shown that for small values of ρ (~3-5 degrees/mm), it is necessary to use transmission spectra not with parallel and crossed polarizers, as is usually done, but at different angles between them, for example ±45°, to obtain better results. Circular dichroism measurements of these crystals were performed. Using Kramers-Kronig relations, the connection between the circular dichroism bands and the rotation of the light polarization plane in the absorption band region was determined. Dispersion curves of ρ values were calculated, taking into account absorption in the wavelength range of 400–1000 nm for crystals (La0.6Nd0.4)3Ga5SiO14, (La0.4Nd0.6)3Ga5SiO14, Nd3Ga5SiO14, and compared with the dispersion of ρ for langasite crystal La3Ga5SiO14. Average refractive indices and optical activity parameters of these crystals were calculated from structural data. It is shown that the dependence of the average refractive indices and ρ values on the parameters of the elementary cell, calculated under the assumption of no absorption, is linear. However, such a linear dependence is not observed for experimental ρ values, which is associated with the influence of absorption and the peculiarities of the structure (nonlinear change in the geometry of optically active regions of electron density upon replacing part of La with Nd).

The results of studying the structural features of samples of zinc-oxide films obtained by magnetron deposition on chips of lanthanum-magnesium hexaaluminate and the surface of sapphire substrates with a gold buffer layer are presented. Analysis of the structure and morphology of the films is carried out using a set of methods, including high-resolution X-ray diffractometry, the method of constructing pole figures, and transmission electron microscopy. It is shown that when using cleavages of lanthanum-magnesium hexaaluminate, an epitaxial ZnO film is formed without signs of growth rotating domains. The use of a gold buffer layer during growth on sapphire substrates improves the crystalline quality of ZnO films, but does not completely suppress domain growth.

The results of studying the specific features of the growth of zinc oxide films formed on sapphire substrates by magnetron sputtering in an inhomogeneous electric field are presented. The films have been analyzed by high-resolution X-ray diffractometry, pole figure technique, and electron microscopy. A sequence of changes in the lateral structure with an increase in the film thickness, which depends also on the local potential, is revealed. Thus, regions with a higher surface potential correspond to the ZnOá10 0ñ(0001)||Al2O3á11 0ñ(0001) epitaxial ratio with the least lattice mismatch.

Yttrium‒aluminum garnet single crystals, including cerium-doped ones, have been grown from melt by Bagdasarov’s method. A comparative spectroscopy study of garnet single crystals and specially prepared ceramics of the same composition has been carried out. The comparative analysis suggests that an increase in the concentration of cerium ions in the garnet crystals improves the spectral-luminescence and scintillation characteristics of the latter and facilitates effective quenching of the substrate luminescence. Ways of optimizing the synthesis conditions to improve the efficiency of scintillators based on Y _1-x Ce x 3 Al 5 O 12 garnet crystal have been proposed.

The structure and optical properties of langasite family crystals (La 1– x Nd x ) 3 Ga 5 SiO 14 with different Nd contents have been studied. The optical rotation ρ for these crystals has been calculated from the measured polarized-light transmission spectra. It is shown that, at a small ρ value (~3–5 deg/mm), the transmission spectra recorded at different angles between polarizers (e.g., ±45°) should be used to obtain the best results, rather than the transmission spectra at parallel and crossed polarizers, as is generally accepted. The circular dichroism of these crystals has been measured. The relationship between the circular-dichroism bands and the change in the optical rotation near the absorption bands has been determined using the Kramers–Kronig relations. Variances of the parameter ρ with allowance for absorption in the wavelength range of 400–1000 nm have been calculated for (La 0.6 Nd 0.4 ) 3 Ga 5 SiO 14 , (La 0.4 Nd 0.6 ) 3 Ga 5 SiO 14 , and Nd 3 Ga 5 SiO 14 crystals and compared with the variance of ρ for a La 3 Ga 5 SiO 14 langasite crystal. The mean refractive indices and parameters of optical activity of these crystals have been calculated from the structural data. It is shown that the dependences of the mean refractive index and parameter ρ, calculated within the no-absorption approximation, on the unit-cell parameters are linear. Note that the dependence observed for experimental ρ values is not linear, which is related to the influence of absorption and structural features (nonlinear change in the geometry of optically active regions of the electron density when La is partially replaced with Nd).

A new design of a galvanic sensor of pulsed X-ray radiation is proposed, which is a flat electric capacitor with a window in one metal lining and a solid dielectric made of the single crystal sapphire with a thickness of 200-300 µm inside. The influence of the surface roughness of the sapphire in the window area on the galvanic linear sensor of X-ray radiation has been established. Tests have shown that with ultra-smooth polishing of the sapphire plate working surface in the window area to a roughness of Rq≤ 0.2 nm, it is possible to provide the galvanic linear detection of X-rays with an energy in the range of 0.1-1 keV and a power density of 1-2 MW•cm-2 with a sensor response time of about 8 ns. Sensors of this type can be used in studies of inertial nuclear fusion processes

A new design of a galvanic sensor of pulsed X-ray radiation is proposed, which is a flat electric capacitor with a window in one metal lining and a solid dielectric made of a single-crystal sapphire with a thickness of 200-300 μm inside. The influence of the surface roughness of the sapphire in the window area on the galvanic linear sensor of X-ray radiation has been established. Tests have shown that, with ultra-smooth polishing of the sapphire plate working surface in the window area to a roughness of R q ≤ 0.2 nm, it is possible to provide the galvanic linear detection of X-rays with an energy in the range of 0.1-1 keV and power density of 1-2 MW· cm -2 with a sensor response time of about 8 ns. Sensors of this type can be used in studies of inertial nuclear fusion processes. Keywords: X-ray radiation, galvanic sensor, sapphire, dielectric, flat capacitor.

Specific features of the formation of nanoporous Al 2 O 3 , AlN, and Ni(Fe+Al) 2 O 4 films on sapphire substrates by thermal sputtering of metals with subsequent firings in an appropriate gas medium are studied. This synthesis process involves interaction of the metal solid phase with an active ambient gas medium (oxygen or nitrogen), some other chemical reactions, diffusion, and crystallization. It can be controlled via a set of synthesis parameters to achieve desired film properties and structure. It is shown that variations in the thickness of initial metal films, annealing temperature and time, and sample heating rate affect the run and completeness of the above processes and allow one to obtain films with a required structure (in particular, films with a nanoporous structure with pores 10–200 nm in size).

A comparative study of the inelastic electron scattering on supersmooth surfaces of sapphire single crystals, including those with gold and platinum nanolayers, was performed. The techniques of cathodoluminescence spectroscopy, probe microscopy, and energy-dispersive microanalysis, as well as additional annealing of samples in air up to 1200°C, were used. It was found that, under electron-beam irradiation, gold nanocrystals interact with sapphire surface to form etch pits on it. No such pits were found on the sapphire surface with platinum layers. The sapphire radiolysis is assumed to be the main cause of sapphire etching in the Au/Al2O3 system and the increase in its cathodoluminescence in comparison with pure sapphire. The changes in the cathodoluminescence spectra of the samples of the Pt/Al2O3 system are related to the electron beam defocusing on the rough surface and the platinum ability to inhibit sapphire radiolysis.

A wide bandgap oxide/transition metal multilayered structure, consisting of four submicron-thick Ga-doped ZnO layers and three ultrathin Co metal layers, is studied to highlight the induction of room temperature ferromagnetism (RTFM), a fundamental outcome of investigations dealing with dilute magnetic semiconductors and multiferroic materials. A comprehensive study including the structural, optical and magnetic properties of both as-deposited and high-temperature annealed samples is described. Optical transmittance spectroscopy and x-ray diffraction measurements confirm the conversion of the layered structure into a solid-state solution of Co within the Ga-doped ZnO after annealing. The study discloses RTFM in the as-deposited state due to nonoxidized metal components within the multilayer structure.

X-ray diffractometry, X-ray profilometry, atomic-force microscopy, and sclerometer tests are employed in the study of R -cut plates of sapphire single crystals grown with the aid of the Kyropoulos technique and used as substrates for the silicon-on-sapphire structures. Regions with different degrees of perfection can be found even on a single plate. Mutually consistent results of the four experimental methods based on different physical principles can be used to reveal regions of structural imperfection on the surface of a plate. It is expedient to employ a complex procedure for multipoint monitoring of the parameters of plates to reduce the number of defect samples that serve as substrates in the production of electronic devices.

The morphology and structure of heteroepitaxial ZnO films deposited on the (0001) surface of crystalline substrates of lanthanum–magnesium hexaaluminate LaMgAl 11 O 19 by magnetron sputtering have been investigated by electron microscopy, probe microscopy, X-ray diffraction (XRD) analysis, and electron diffraction analysis. It is established that the structure of these ZnO films is more perfect than that of the films on (0001) sapphire substrates (including those containing a buffer aluminum nitride layer).

An R-cut sapphire wafers grown by Kyropoulos technique for fabrication of silicon-on-sapphire structures has been examined with the use of X- ray diffractometry, reflectometry, atomic-force microscopy and sclerometry methods. It is found that areas of different degree of crystal structure perfection are present even within the same wafer. It is shown that the results obtained by four different methods, based on different physical principles, are in good agreement and allow to recognize the areas of imperfect structure on the wafer surface. Implementation of comprehensive control of the quality parameters at several points of wafer surface is justified in order to reduce the production defects in the usage of sapphire wafers for fabrication of semiconductor devices.