Перегляд за автором "Kovalenko, E. N."

Зараз показано 1 - 16 з 16
  • Зображення мініатюри
    Публікація
    Absorption Spectra of Thin Films Compounds in the PbCl-CuCl System
    (Eskisehir Technical University, 2021) Kovalenko, E. N.; Yunakova, O. N.; Yunakov, N. N.
  • Зображення мініатюри
    Публікація
    Absorption Spectrum of KPb2Br5 Thin Films.
    (Eskisehir Technical University, 2021) Kovalenko, E. N.; Yunakova, O. N.; Yunakov, N. N.
  • Зображення мініатюри
    Публікація
    Dispersion of refractive index of thin films CdI2 and ZnI2
    (НТК “Інститут монокристалів” Національної академії наук України, 2010) Kovalenko, E. N.; Miloslavsky, V. K.; Yunakova, O. N.
    A dispersion of refractive index in thin films CdI2 and ZnI2 are measured in the interval of lengths waves 300-1000 nanometers, its processing with the help monooscillator model is in the good agreement with data of experiment. The optical inductivity  of two compounds is determined by retrieved parameters of this model, this optical inductivity are utilised for the further analysis of excitons states in CdI2 and ZnI2, and, in particular, for determination of 1s excitons radius. The retrieved values аех are close to parameters of a unit cell of two compounds, that indicates a fitting of excitons in two compounds to excitons of intermediate electron - hole connection
  • Зображення мініатюри
    Публікація
    Effect of iodine impurity on the absorption spectrum and phase transitions in CsPbCl3 thin films
    (НТК “Інститут монокристалів” Національної академії наук України, 2018) Kovalenko, E. N.; Yunakova, O. N.; Yunakov, N. N.
    The absorption spectra of thin films of solid solutions CsPb(Cl1-xIx)3 0
  • Зображення мініатюри
    Публікація
    Electronic Absorption Spectrum of Thin K2ZnI4 Films
    (2008) Yunakova, O. N.; Miloslavsky, V. K.; Kovalenko, E. N.
    The absorption spectrum of thin K2ZnI4 films has been investigated in the range of 3–6 eV at temperatures from 90 to 340 K. It is established that this compound belongs to direct-gap insulators; low-frequency exciton excitations are localized in the ZnI4 lattice layers and have a quasi-two-dimensional character. The spectral analysis revealed the existence of two K2ZnI4 modifications, which presumably belong to the monoclinic (I) and orthorhombic (II) phases. The temperature dependences of the spectral position and halfwidth of the low-frequency exciton band in K2ZnI4 revealed the existence of first-order phase transitions at 215 and 225 K in the monoclinic and orthorhombic phases, respectively.
  • Зображення мініатюри
    Публікація
    Exciton absorption spectra of KPb2Br5 thin films
    (Institute for Single Crystals, 2016) Kovalenko, E. N.; Kovalenko, V. V.; Yunakova, O. N.; Yunakov, N. N.
    The absorption spectrum of KPb2Br5 thin film of tetragonal (I) and monoclinic (II) structures were investigated in the spectral region of 2-6 eV and the temperature range 90-440K. It was found that KPb2Br5 (I) of the tetragonal structure irreversibly becomes in KPb2Br5(II) of the monoclinic structure when T = 293 K. It is found that low-frequency exciton excitations of KPb2Br5 (I, II) are localized in the sublattice, which contains ions Pb2+, and its are two-dimensional nature.
  • Зображення мініатюри
    Публікація
    Exciton absorption spectra of RbPb2Cl5 and Rb6Pb5Cl16 thin films
    (НТК “Інститут монокристалів” Національної академії наук України, 2019) Kovalenko, E. N.; Yunakova, O. N.; Yunakov, N. N.
    The absorption spectra of thin RbPb2Cl5 and Rb6Pb5Cl16 films were studied in the spectral range 2-6 eV and the temperature interval 90-500 K. A correlation was established between the absorption spectra and the crystal structure of the compounds. Excitons in both compounds are localized in a sublattice containing Pb2+ ions, and refer to excitons of the intermediate bond. An analysis of the temperature dependence of the half-width of exciton bands establishes a two-dimensional (2D) nature of the excitons in RbPb2Cl5 and three-dimensional (3D) in Rb6Pb5Cl16.
  • Зображення мініатюри
    Публікація
    Exciton absorption spectra of thin films of RbCu2Cl3 and Rb2Cu3Cl5 ternary compounds
    (2021) Kovalenko, E. N.; Yunakova, O. N.; Yunakov, N. N.
    The absorption spectra of RbCu2Cl3 and Rb2Cu3Cl5 thin films were studied in the 2–6 eV spectral and 90–450 K temperature ranges. The localization of excitons in 3–4CuCl structural elements of crystal lattice of compounds, three-dimensional nature of excitons in RbCu2Cl3 and two-dimensional nature of excitons in Rb2Cu3Cl5 were es-tablished. The exciton spectra of RbCu2Cl3 and Rb2Cu3Cl5 thin films were interpreted based on the transitions in the Cu+ ion.
  • Зображення мініатюри
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    Exciton absorption spectrum of Cs4PbCl6 thin films
    (Institute for Single Crystals, 2015) Yunakova, O. N.; Miloslavsky, V. K.; Kovalenko, E. N.; Kovalenko, V. V.
    The absorption spectrum of thin films Cs4PbCl6 is studied in the spectral range of 2-6 eV within the temperature interval 90-500K. Localization of exciton excitations in the sublattice of the compound containing Pb2+ ions is established. Excitons related to excitons of the intermediate bond and are two-dimensional nature
  • Зображення мініатюри
    Публікація
    Exciton absorption spectrum of thin (KI)1-x(PbI2)x films
    (НТК “Інститут монокристалів” Національної академії наук України, 2013) Kovalenko, E. N.; Miloslavskii, V. K.; Yunakova, O. N.
    The absorption spectra of thin films of (KI)1-x(PbI2)x is investigated in a spectral interval 2-6 eV. The formation in system KI-PbI2 of two compounds КPbI3 and К4PbI6 is established from the analysis of spectra. It is shown, that exciton excitations in investigated compounds are localised in sublattice containing lead ions and concern to intermediate communication excitons.
  • Зображення мініатюри
    Публікація
    Exciton Absorption Spectrum of Thin CsPbI3 and Cs4PbI6 Films
    (2012) Yunakova, O. N.; Miloslavsky, V. K.; Kovalenko, E. N.
    A method for preparing thin films of CsPbI3 and Cs4PbI6 complex compounds has been devel oped. Their absorption spectrum is investigated in the energy range of 2–6 eV at temperatures from 90 to 500 K. It is found that the CsPbI3 compound is unstable and passes to the Cs4PbI6 phase upon heating at T ≥ 400 K.
  • Зображення мініатюри
    Публікація
    Exciton absorption spectrum of thin films of (CsxK1-x)2CuCl3 solid solutions.
    (2024) Kovalenko, E. N.; Yunakova, O. N.; Yunakov, N. N.
    The absorption spectra of thin films of (CsxK1-x)2CuCl3 0≤х≤1 (T=90K) solid solutions in the spectral range 2–6 eV were studied. According to the analysis of the spectra, the formation of two types of compounds was observed and studied: 1) compounds at x=0 and in the range of 0.4≤х≤1 which are isostructural to Cs2CuCl3 and K2CuCl3; 2) compounds at x=0.2 which are isostructural to CsCu2Cl3. The excitonic spectra of (CsxK1-x)2CuCl3 0≤х≤1compounds are caused by transitions in the Cu+ ion. The linear concentration dependences of the spectral position of exciton bands in both types of compounds confirm the localization of excitons in sublattices containing Cu+ ions.
  • Зображення мініатюри
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    Exciton absorption spectrum of thin films of Cs1-xRbxCu2Cl3 solid solutions
    (Institute for Single Crystals, 2021) Kovalenko, E. N.; Yunakova, O. N.; Yunakov, N. N.
    The exciton absorption spectra of thin films of Cs1-xRbxPbCl3 solid solutions were studied in the spectral range 2 - 6 eV. The formation of solid solutions that are isostructural to CsCu2Cl3 was detected in the concentration range 0х0.6, the formation of solid solutions that are isostructural to RbCu2Cl3 was detected in the range 0.6<х≤1. A linear concentration dependences of the parameters of the exciton bands and the bandgap width were found in the intervals 0≤x≤0.6 and 0.6<х≤1. Exciton spectra of Cs1-xRbxCu2Cl3 0≤х≤1 solid solutions were interpreted based on the transitions in the Cu+ ion.
  • Зображення мініатюри
    Публікація
    Exciton absorption spectrum of thin films of ternary compounds in the CsCl-CuCl system
    (Фізико-технічний інститут низьких температур імені Б. І. Вєркіна, 2023) Kovalenko, E. N.; Yunakova, O. N.; Yunakov, N. N.
    The absorption spectra of thin films (CsCl)1-x(CuCl)x were studied at T=90K in the spectral range 2 – 6 eV. From the analysis of the spectra, the formation of CsCu2Cl3 and Cs2CuCl3 compounds in the CsCl – CuCl system was established. The Cs2CuCl3 compound is stable only in a vacuum; in air, it apparently decomposes into CsCu2Cl3 with a disordered crystal lattice and CsCl. The exciton spectrum of both compounds is interpreted on the basis of transitions in the Cu+ ion. A one-dimensional (1D) character of excitons in CsCu2Cl3 and a two-dimensional (2D) character in Cs2CuCl3 was established
  • Зображення мініатюри
    Публікація
    Influence of impurities on the absorption spectrum of thin Cs4PbI6 films
    (Institute for Single Crystals, 2014) Yunakova, O. N.; Miloslavsky, V. K.; Kovalenko, E. N.; Kovalenko, V. V.
    The absorption spectrum of the solid solutions (Cs1-xMx)4PbI6 (M=Rb,K) 0х1 is studied in the spectral range 2-6 eV at T = 90K. The formation of solid solutions (Cs1-xRbx)4PbI6 in all range of concentrations is established, the compound К4PbI6 is unstable. Linear concentration of long-wavelength exciton band parameters in the (Cs1-xMx)4PbI6 indicates the localization of excitons in PbI64- structural elements of the compounds crystal lattice
  • Зображення мініатюри
    Публікація
    The Exciton Absorption Spectrum of KPbI3 Thin Films
    (ФТИ им. А.Ф.Иоффе, 2014) Yunakova, O. N.; Miloslavsky, V. K.; Kovalenko, E. N.
    The absorption spectrum of KPbI3 thin films is studied in the spectral range 2–6 eV within the temperature interval 90–470 K. Localization of excitons in the sublattice of the compound containing lead ions is established. Excitons are shown to be of two dimensional nature.