Статті в Scopus

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hdl:123456789/2131

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Перегляд Статті в Scopus по Автор "Ковальов, Леонід Євгенійович"
  • Матеріал
    Deep Centers Influence On Photoresponse Characteristics In High-Resistivity ZnSe
    (MRS Online Proceedings Library, Cambridge University Press, 2011) Ковальов, Леонід Євгенійович ; Kovalev, L. E. ; Kovalyov, L. E.
    The photocurrent peak after preliminary optical excitation with specific wavelength in high resistivity (ρ≍1012 Ω∗cm), unintentionally doped ZnSe monocrystals was observed. To study photocurrent “flash” phenomenon, the photocurrent relaxation spectra, photon-capture crosssection (PCCS) spectra and photo-electron paramagnetic resonance (photo-EPR) were investigated. Two-levels model involving the recombination of an S-center and an acceptor A has been developed to obtain the relation between recombination probability and instantaneous photocurrent value. The S-centers ionization energies (1.06eV and 1.14eV from the bottom of the conduction band) and charge carriers life times were determined. The acceptor's positions in ZnSe band gap are equal to 2.05, 2.11, 2.16 and 2.21eV from the bottom of the conduction band. The photocurrent and PCCS “flash” nature as well as complicated photo-EPR are associated with the relaxation of S-centers attributed to Fe ion in the band gap of semi-insulated ZnSe.
  • Матеріал
    Effect Of Thermal Annealing In Bi And Zn Melts On Local Centers In Znse
    (MRS Online Proceedings Library, Cambridge University Press, 2011) Ковальов, Леонід Євгенійович ; Kovalev, L. E. ; Kovalyov, L. E.
    Time-resolved photoluminescence (TRPL) at T=4,2K, electron paramagnetic resonance (EPR) in the range of 4,2K–77K, and wavelength modulated transmittance (WMT) spectra for both undoped and annealed in Bi and Zn melts ZnSe single crystals have been investigated. It is found that the annealing in Bi melts leads to recovery of crystal structure. This supposition is based on the increase of fine and hype fine interaction of residual Mn2+, ions with the simultaneous decrease of the EPR signals line width and the decrease of the F-center line. Furthermore, the band with λmax=520 nm disappears, while exciton band I1 (λmax=445 nm) and edge band Q0 – DAP (λmax=460,2 nm), involving AlZn – LiZn, pairs, become more revealed. At the same time, band narrowing of the TRPL spectra was observed. The annealing in Zn melt causes the increase of the number of F-center. From WMT spectra the energy position of local centers and the dominant influence on impurities and defects of the crystal structure were investigated.