Institute for Single Crystals


Institute for Single Crystals

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Kharchenko V.O.,Institute of Applied Physics | Kharchenko D.O.,Institute of Applied Physics | Lysenko I.O.,Institute for Single Crystals | Yanovsky V.V.,Institute for Single Crystals | Dvornichenko A.V.,Sumy State University
Nanosistemi, Nanomateriali, Nanotehnologii | Year: 2016

Processes of nanosize surface-structures' formation during ion-beam sputtering are studied. By considering the anisotropic model taking into account fluctuations of the incident ions' flow, the diagrams illustrating the possible types of the equiaxed and wave surface structures, which are implemented in the system, are obtained. As shown, the number of such structures at late stages of the system evolution remains constant. Temporal dependences of the surface growth and its roughness exponents are discussed. Dynamics of pattern formation on the surface is studied taking into account fluctuations of the incident angle. As shown, the statistical properties of the multiplicative-noise impact on the dynamics of pattern formation, character and morphology of the surface structures. Within the framework of the generalized model taking into account the relaxation of the irradiated surface, a phase diagram is obtained illustrating domains of main system parameters, where stationary structures on the surface of the sputtered material and smooth surface can be realized. Dynamics of structural defects is discussed in detail. The developed approach is applied to simulate sputtering process of the silicon surface with argon ions. The dependences of the penetration depth of the ions and the sputtering yield on both the incident angle and the energy of the ions are obtained. As shown, at small values of incident angle, the equiaxed (isotropic) structures are realized, whereas at large values of the incident angle, wave structures are formed during a sputtering. The dependences of the wavelength of the silicon structures on the energy of the incoming ions are calculated. As shown, the linear size of isotropic structures decreases with growing energy of the incident ions and takes the value of the order of several tens of nanometres.

Belli P.,University of Rome Tor Vergata | Bernabei R.,University of Rome Tor Vergata | Cappella F.,University of Rome Tor Vergata | Cappella F.,University of Rome La Sapienza | And 12 more authors.
Nuclear Physics A | Year: 2011

A search for double β decay of dysprosium was realized for the first time with the help of an ultra-low background HP Ge γ detector. After 2512 h of data taking with a 322 g sample of dysprosium oxide limits on double beta processes in 156Dy and 158Dy have been established on the level of T1/2≥1014-1016 yr. Possible resonant double electron captures in 156Dy and 158Dy were restricted on a similar level. As a by-product of the experiment we have measured the radioactive contamination of the Dy2O3 sample and set limits on the α decay of dysprosium isotopes to the excited levels of daughter nuclei as T1/2≥1015-1017 yr. © 2011 Elsevier B.V.

Lisitsyn V.M.,Tomsk Polytechnic University | Valiev D.T.,Tomsk Polytechnic University | Tupitsyna I.A.,Institute for Scintillation Materials of Ukraine | Polisadova E.F.,Institute for Scintillation Materials of Ukraine | And 5 more authors.
Journal of Luminescence | Year: 2014

We investigated pulsed photoluminescence and pulsed cathodoluminescence in ZnWO4 crystals and composite materials based on dispersed powders of zinc tungstate in the polymer matrix. It is shown that the size of crystal particles affects the luminescence decay time in excitation by electron and laser radiation. The decay time obtained for the composite material with nanoparticles 25 nm and 100 nm in size is equal to 5 μs and 7 μs, respectively. Relative values of the light yield of composite containing zinc tungstate crystals in the form of rods are found to be larger in comparison with crystallites in the form of grains. The mechanisms of luminescence recombination in laser and electron excitation are discussed. © 2014 Elsevier B.V.

Ryzhikov V.D.,Institute for Scintillation Materials of Ukraine | Naydenov S.V.,Institute for Single Crystals | Opolonin O.D.,Institute for Scintillation Materials of Ukraine | Volkov V.G.,Institute for Scintillation Materials of Ukraine | Smith C.F.,Naval Postgraduate School, Monterey
Progress in Biomedical Optics and Imaging - Proceedings of SPIE | Year: 2016

This work has been dedicated to the search for a new possibility to use multi-energy digital radiography (MER) for medical applications. Our work has included both theoretical and experimental investigations of 2-energy (2E) and 3- energy (3Crossed D sign•) radiography for imaging the structure of biological objects. Using special simulation methods and digital analysis based on the X-ray interaction energy dependence for each element of importance to medical applications in the X-ray range of energy up to 150 keV, we have implemented a quasi-linear approximation for the energy dependence of the X-ray linear mass absorption coefficient μm (E) that permits us to determine the intrinsic structure of the biological objects. Our measurements utilize multiple X-ray tube voltages (50, 100, and 150 kV) with Al and Cu filters of different thicknesses to achieve 3-energy X-ray examination of objects. By doing so, we are able to achieve significantly improved imaging quality of the structure of the subject biological objects. To reconstruct and visualize the final images, we use both two-dimensional (2D) and three-dimensional (3D) palettes of identification. The result is a 2E and/or 3E representation of the object with color coding of each pixel according to the data outputs. Following the experimental measurements and post-processing, we produce a 3Crossed D sign• image of the biological object - in the case of our trials, fragments or parts of chicken and Turkey. © 2016 SPIE.

Fedorov A.,Institute for Scintillation Materials of Ukraine | Gektin A.,Institute for Scintillation Materials of Ukraine | Lebedynskiy A.,Institute for Scintillation Materials of Ukraine | Mateychenko P.,Institute for Single Crystals | Shkoropatenko A.,Institute for Scintillation Materials of Ukraine
Radiation Measurements | Year: 2013

500 mkm thick CsI:Tl columnar films can be produced using thermal evaporation in vacuum by sublimation of the same bulk crystal. Comparison of afterglow and radiation stability of deposited CsI:Tl films with source crystal was the aim of current work. It is shown that the afterglow in the films is always below its level in initial single crystal. It was ascertained that the annealing atmospheres influence the processes leading to the activator depletion of the films during the thermal processing. © 2013 Elsevier Ltd. All rights reserved.

Khilya O.V.,Taras Shevchenko National University | Volovnenko T.A.,Taras Shevchenko National University | Turov A.V.,Taras Shevchenko National University | Zubatyuk R.I.,Institute for Single Crystals | And 2 more authors.
Chemistry of Heterocyclic Compounds | Year: 2011

The reaction of azolylacetonitriles with γ-chlorobutyryl chlorides gave the corresponding 2-(1-R-1,3-di- hydro-2H-benzimidazol-2-ylidene)-, 2-(1,3-benzothiazol-2-ylidene)-, and 6-chloro-2-(4-methylthiazol-2-ylidene)-3- oxohexanenitriles. A study of the intramolecular cyclization of 2-(quinazolin-2-ylidene)-3-oxo-6-hexanenitriles and -heptanenitriles has led to the development of an efficient method for the preparation of 2-(quinazolin-2-yl)-2-(tetrahydrofuran-2-ylidene)acetonitriles. The (Z,E)-isomerism of the synthesized 2-hetaryl-2-(tetrahydrofuran-2-ylidene) acetonitriles was studied. © 2011 Springer Science+Business Media, Inc.

Kolos N.N.,University of Kharkiv | Kovalenko L.U.,University of Kharkiv | Borovskoy V.A.,Institute for Single Crystals
Chemistry of Heterocyclic Compounds | Year: 2011

Dihydro derivatives of pyrazolo[3,4-b]pyridine-, pyrazolo[1,5-a]pyrimidine- , and [1,2,4]triazolo-[1,5-a]pyrimidinecarboxylates have been prepared by cyclocondensation of β-aroylacrylates with 5-aminopyrazoles and 3-amino-1,2,4-triazole. Heating dihydro[1,2,4]triazolo[1,5-a]pyrimidine-7- carboxylates with hydrazine hydrate led to recyclization of the pyrimidine ring to form 6-arylpyridazin-3(2H)-ones. © 2011 Springer Science+Business Media, Inc.

Baumer V.N.,Institute for Single Crystals | Strzhemechny M.A.,Ukrainian Academy of Sciences | Zloba D.I.,Ukrainian Academy of Sciences | Zubatyuk R.I.,Institute for Single Crystals | And 2 more authors.
Journal of Molecular Structure | Year: 2012

Solid state properties of meta-bromobenzophenone crystals were studied, including X-ray diffraction, integrated phosphorescence spectrometry, and ab initio calculations. The structure of meta-bromobenzophenone crystals has been determined by powder X-ray diffraction to be orthorhombic (space group Pbca) with a = 11.70461(15) , b = 7.70025(9) , c = 24.0055(2) , Z = 8. This structure includes a supramolecular network formed by weak hydrogen bonds of CH ⋯ O and CH ⋯ π short contacts. A tight π-π short contact between virtually parallel substituted and unsubstituted phenyl rings of neighbor molecules is another distinguishing feature of the crystal structure, which might be the cause of the unusual very broad lonely band in the room-temperature phosphorescence spectrum. The low-temperature (1.6 K) phosphorescence spectra are of monomeric character, revealing sharp lines superimposed on broad 0 → ν bands, which is a signature of emission from some traps. © 2012 Elsevier B.V. All rights reserved.

Deineka T.G.,Institute for Single Crystals | Doroshenko A.G.,Institute for Single Crystals | Mateychenko P.V.,Institute for Single Crystals | Tolmachev A.V.,Institute for Single Crystals | And 5 more authors.
Journal of Alloys and Compounds | Year: 2010

A new precursor of yttrium aluminum garnet with an approximate composition of NH4AlY0.6(CO3)x(OH) y(SO4)z·nH2O has been synthesized via a reverse strike co-precipitation method with ammonium hydrogen carbonate as the precipitant and ammonium aluminum sulfate as the sulfate ions source. The evolution of phase, chemical composition and morphology of the precursor during calcination has been studied by means of XRD, XPS, DTA-TG, BET methods and FT-IR spectroscopy. The loosely agglomerated powders with narrow size distribution, spherical shapes and diameter of 50-60 nm have been obtained by calcination of the sulfate-containing precursor at 1100 °C for 2 h. The doping by sulfate ions enhances densification of Y3Al 5O12:Nd3+ nanopowders compared to undoped ones. This leads to improved microstructure and optical transmittance of vacuum sintered ceramics prepared from sulfate-doped nanopowders. © 2010 Elsevier B.V. All rights reserved.

Fedorov A.,Institute for Scintillating Materials | Lebedinsky A.,Institute for Scintillating Materials | Mateychenko P.,Institute for Single Crystals
Journal of Crystal Growth | Year: 2011

The dewetting behavior of vacuum deposited CsI films on LiF (1 0 0) oriented substrate was observed. Rupture of initially continuous solid films occurs in a duration of monthsminutes, depending on film thickness. Finally, spherical particles are formed on the substrate. The particles possess a pronounced orientation in the <1 1 0> direction normal to the substrate surface. This effect has been attributed to the difference between surface energy values of the film and substrate, and the interface energy according to Young's equation. The corresponding values of surface energy have been calculated and have confirmed the nature of the observed effect. © 2010 Elsevier B.V. All rights reserved.

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