Cietvielu fizikas institūts / Institute of Solid State Physics

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Browsing Cietvielu fizikas institūts / Institute of Solid State Physics by Author "Akilbekov, A."

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    Ab-Initio Calculations of Oxygen Vacancy in Ga2O3 Crystals
    (Sciendo, 2021) Usseinov, A.; Koishybayeva, Zh.; Platonenko, Aleksandrs; Akilbekov, A.; Purans, Juris; Pankratov, Vladimir; Suchikova, Y.; Popov, Anatoli I.
    Gallium oxide β-Ga2O3 is an important wide-band gap semiconductor. In this study, we have calculated the formation energy and transition levels of oxygen vacancies in β-Ga2O3 crystal using the B3LYP hybrid exchange-correlation functional within the LCAO-DFT approach. The obtained electronic charge redistribution in perfect Ga2O3 shows notable covalency of the Ga-O bonds. The formation of the neutral oxygen vacancy in β-Ga2O3 leads to the presence of deep donor defects with quite low concentration. This is a clear reason why oxygen vacancies can be hardly responsible for n-type conductivity in β-Ga2O3.--//-- Licenced under CC BY 4.0.
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    Accumulation of radiation defects and modification of micromechanical properties under MgO crystal irradiation with swift 132Xe ions
    (Elsevier B.V., 2020) Baubekova, G.; Akilbekov, A.; Feldbach, E.; Grants, Rolands; Manika, Ilze P.; Popov, Anatoli I.; Schwartz, K.; Vasil'Chenko, Evgeni A.; Zdorovets, Maxim V.; Lushchik, Aleksandr Ch
    Accumulation of F-type defects under irradiation of MgO crystals by 0.23-GeV 132Xe ions with fluence varying by three orders of magnitude has been investigated via the spectra of optical absorption and low-temperature cathodoluminescence. The number of single centers continuously increases with fluence without any marks of saturation. At the highest fluence, a mean volume concentration of 3.1 × 1019 and 3.35 × 1019 cm−3 is reached for F and F+ centers, respectively. The F+ emission strongly dominates in the cathodoluminescence of irradiated MgO and its enhancement with fluence is detected. However, the creation efficiency of the F2 aggregate centers is very low and fluence dependence has a complicated shape. Radiation-induced changes of micro-mechanical properties of the same samples have been analysed; the depth profiles of hardening correlate with the ion energy loss. A joint contribution of ionization and impact mechanisms in the formation of structural defects under MgO irradiation with Xe ions is considered.
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    Luminescence of F2 and F3 + centres in LiF crystals irradiated with 12 MeV 12C ions
    (Institute of Physics Publishing, 2018) Akilbekov, A.; Dauletbekova, A.; Kirilkin, N.; Baizhumanov, M.; Seitbayev, A.; Karipbayev, Zh.; Giniyatova, Sh.; Zabels, Roberts
    Dependences of the nanohardness and photoluminescence of F 2 and F 3 + centers on the depth in LiF crystals irradiated with 12 MeV 12 C ions to fluences 10 10 -10 15 ions/cm 2 were studied using laser scanning confocal microscopy, luminescent spectroscopy, and the nanoindentation method. The nanohardness measurements showed a significant hardening effect at the end of the ion run with the dominant contribution of defects formed by the mechanism of elastic collisions. The observed attenuation of the luminescence intensity at high fluences is associated with the intense nucleation of dislocations as traps for aggregate color centers.