M. K. Sheinkman

National Academy of Sciences of Ukraine, Kiev, Misto Kyyiv, Ukraine

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Publications (89)69.08 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: To reveal recombination centers responsible for ZnO UV photosensitivity, combined investigations of photoconductivity (PC) and photoluminescence (PL) spectra were performed in nominally undoped ZnO single crystals. In PL spectra, green (500 nm), orange (620 nm) and red (720 nm) bands related to deep levels were present, the greater the relative intensity of orange band the higher the photosensitivity. After removal of exciting light, PL afterglow as well as PC “tail” took place at 77 K. It was found that decay time of PC “tail” coincided with that of orange band afterglow and was essentially longer than the afterglow decay times of green and red bands. The conclusion was made that recombination centers responsible for the orange band were the centers of photosensitivity. In addition, a strong influence of electron traps on steady-state PC was shown.
    Solid State Communications 11/2007; · 1.53 Impact Factor
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    ABSTRACT: The process of thermal decomposition of SiO x layers prepared by magnetron sputtering is studied with the use of photoluminescence and Auger and SIMS spectroscopies. From these measurements, we obtained the distributions of the emission properties and the chemical composition over the depth. The effect of the redistribution of silicon and oxygen over the depth is found after the high-temperature annealing which results in the formation of a Si nanocrystal. These redistributions result in the appearance of a Si-depleted region near the layer-substrate interface. The formation of a depletion layer is dependent on the excess of Si. A decrease of the silicon content over the depth of annealed layers is accompanied by a decrease of the Si nanocrystal size, as it is evidenced by the blue shift of the photoluminescence maximum. The mechanism of decomposition of SiO x and the possible reasons for the appearance of a Si-depleted region are discussed.
    Semiconductor Physics, Quantum Electronics & Optoelectronics. 10/2007; 10(4):21-25.
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    ABSTRACT: The change in the diffusion barrier for anion vacancies in polar crystals is calculated in the case where one electron (F centers) or two electrons (F′ centers) are captured. The lowest singlet and triplet states are considered for the two-electron system. It is shown that the capture of two electrons on the lowest metastable triplet state (which is possible under nonequilibrium conditions, for example, in the case of either exchange scattering of band electrons or thermal refilling of energy levels) leads to a decrease in the diffusion barrier for the system. However, for the two-electron center in the lowest singlet state, the potential barrier to migration, as a rule, is higher than that for a vacancy without electrons. Calculations are carried out for Gaussian functions with the inclusion of the effects of interelectron correlations and electron-phonon interactions.
    Physics of the Solid State 04/2007; 49(5):818-823. · 0.77 Impact Factor
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    ABSTRACT: The photoluminescence spectra of porous silicon and their temperature dependences and transformations on aging are studied. It is shown that the infrared band prevailing in the spectra of as-prepared samples is due to exciton recombination in silicon crystallites. On aging, a well-pronounced additional band is observed at shorter wavelengths of the spectra. It is assumed that this band is due to the recombination of carriers that are excited in silicon crystallites and recombine via some centers located in oxide. It is shown that the broad band commonly observable in oxidized porous silicon is a superposition of the above two bands. The dependences of the peak positions and integrated intensities of the bands on time and temperature are studied. The data on the distribution of oxide centers with depth in the porous layer are obtained.
    Semiconductors 05/2006; 40(5). · 0.60 Impact Factor
  • V. E. Lashkarev, M. K. Sheinkman
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    ABSTRACT: New stationary and kinetic methods are proposed for determining the parameters of sensitizing recombination r-centres in high resistivity monopolar photoconductors. These methods are based on thermal and optical quenching of the photocurrent. These methods and those described previously [1 to 5] enable all the parameters of r-centres in CdS, CdSe, and partially Cd(S, Se) to be determined. These parameters include the concentration and energy of the centres, and their cross sections for electron and hole capture. The method also gives the cross sections for absorption of photons with energies of 0.9 and 1.4 eV, these photons transfering a hole from an r-centre to an excited level, and to the valence band respectively. The occupation of r-centres by holes under weak illumination and the probabilities of hole capture by r- and s-centres can be obtained.[Russian Text Ignore].
    physica status solidi (b) 03/2006; 11(1):429 - 441. · 1.49 Impact Factor
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    ABSTRACT: The electron concentration n in CdS single crystals was studied as a function of temperature (T = 300 to 1200 K) and Cd vapour pressure (pCd = 0.1 to 0.9 atm). It is found that at pCd = const the value of n non-monotonically depends on T and passes through a maximum. This points to a retrograde solubility of Cd in CdS; its dependence on pCd is determined. It is concluded that with decreasing temperature a part of the excess Cd forms agglomerates; the degree of dissociation of these agglomerates depends on T and is independent of pCd. The charge of the dominant electrically active defects changes within the investigated temperature range: these defects are singly charged at lower temperatures and doubly charged at higher temperatures.Es wurde die Elektronenkonzentration n in CdS-Einkristallen in Abhängigkeit von Temperatur (T = 300 bis 1200 K) und Cd-Dampfdruck (pCd = 0,1 bis 0,9 Atm) untersucht. Bei konstantem Cd-Dampfdruck hängt n von T nicht-monoton ab und durchläuft ein Maximum, was auf eine rückläufige Löslichkeit von Cd in CdS hindeutet, deren pCd-Abhängigkeit bestimmt wurde. Es wird geschlossen, daß ein Teil des überschüssigen Kadmiums mit abnehmender Temperatur agglomeriert. Der Dissoziationsgrad der Agglomerate ist temperaturabhängig und unabhängig von pCd. Die Ladung der dominierenden elektrisch aktiven Defekte ändert sich im untersuchten Temperaturbereich: Die Defekte sind bei niedrigen Temperaturen einfach und bei höheren doppelt geladen.
    physica status solidi (a) 02/2006; 33(2):765 - 771. · 1.21 Impact Factor
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    ABSTRACT: Electroluminescence, electrical and noise properties are investigated of ZnS metal-semiconductor light-emitting diodes which exhibit blue emission under forward voltage bias U ⪆ ⪆ 1.8 V; the external efficiency of such diodes attains 0.1%. A conclusion is drawn that such electroluminescence may be due to the injection of holes excited in the contact by Auger processes into the semiconductor. It is found that the forward current and, as a result, the electroluminescence intensity are limited by effect of surface levels being filled with electrons in the course of forward current passing.Elektrolumineszenz sowie elektrische und Rauscheigenschaften von lichtemittierenden ZnS-Metall-Halbleiterdioden, die bei Vorspannungen in Durchlaßrichtung von U ≧ 1,8 V blaue Emission zeigen, werden untersucht. Die äußere Ausbeute dieser Dioden erreicht 0,1%. Es wird angenommen, daß die Elektrolumineszenz durch Injektion von Löchern in den Halbleiter, die im Kontakt durch Augerprozesse angeregt werden, hervorgerufen wird. Es wird gefunden, daß der Durchlaßstrom und damit die Elektroiumineszenzintensität durch den Einfluß von Oberflächen-niveaus begrenzt wird, die während des Stromdurchgangs in Durchlaßrichtung mit Elektronen gefüllt werden.
    physica status solidi (a) 02/2006; 41(1):299 - 305. · 1.21 Impact Factor
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    ABSTRACT: The model of electroluminescence in forward-biased MS and MIS light-emitting diodes based on the Auger recombination on the contact surface of the semiconductor is developed. Such a model may provide a light emission with the threshold voltage Uth = (Eg/2e) – (Efs/2e) < hνmax/e or even Uth = (hνmax/2e) – (Efs/e), depending on the physical processes involved. Here Eg, is the energy gap of the semiconductor, Efs the Fermi energy level in the semiconductor with respect to the c-band edge, hνmax the maximum of the electroluminescence band, e the electron charge. Experimental results obtained on ZnS MS and MIS diodes essential for this model are presented and analysed. It is found that the spectral distribution of diode emission remains practically unchanged at biases close to the threshold voltage Uth. The conclusion is drawn that the electroluminescence and the forward current have typical tunnel characteristics even in the case of ZnS MIS diodes with i-layers several thousand angstroms thick. The main physical properties of zinc chalcogenide light-emitting diodes are explained by means of the model developed.[Russian Text Ignored]
    physica status solidi (a) 02/2006; 64(2):697 - 706. · 1.21 Impact Factor
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    ABSTRACT: Possible reasons of the photorcurrent decrease under illumination are discussed by comparison of all experimental data obtained in the previous studies of the photosensitivity degradation in CdS:Cu single crystals. By further studies a photosensitivity decrease is found to be due to vanishing of the shallow donors which compensate the r-centres. A degradation mechanism consisting in transformation of the shallow donors into rapid recombination s-centres, due to their association, is suggested. On heating in darkness these s-centres dissociate to recover both, the initial density of the shallow donors and the high photosensitivity.Mögliche Gründe für die Verringerung des Photostromes mit Belichtung werden durch den Vergleich aller experimentellen Daten früherer Untersuchungen der Degradation der Photoempfindlichkeit in CdS:Cu-Finkristallen diskutiert. Bei weiteren Untersuchungen wird ein Abfall der Photoempfindlichkeit gefunden, der auf das Verschwinden der flachen Donatoren, die die r-Zentren kompensieren, zurückzuführen ist. Ein Degradationsmechanismus, der in der Umwandlung der flachen Donatoren in schnelle Rekombinations-s-Zentren infolge ihrer Assoziation besteht, wird vorgeschlagen. Beim Tempern im Dunklen dissoziieren diese s-Zentren und stellen sowohl die ursprüngliche Dichte der flachen Donatoren als auch die hohe Photoempfindlichkeit wieder her.
    physica status solidi (a) 02/2006; 60(2):565 - 572. · 1.21 Impact Factor
  • T. V. Torchinskaya, A. A. Shmatov, M. K. Sheinkman
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    ABSTRACT: In commercial red light-emitting diodes (LED), produced by the LPE of AlGaAsGaAs heterostructures the process of transformation of deep centers at their degradation is studied by deeplevel transient spectroscopy technique. The change of LED electroluminescence spectra as well as of light–current and current–voltage characteristics in the course of degradation is monitored concurrently. The process of degradation of red AlGaAs LEDs is found to feature a complex kinetics and to consist of several characteristic stages. An interrelation between the change in phenomenologic characteristics of the LEDs and the appearance of certain types of deep centres is established.[Russian Text Ignored].
    physica status solidi (a) 02/2006; 110(1):213 - 220. · 1.21 Impact Factor
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    ABSTRACT: In this work the aging processes of magnetron-sputtered Si–SiOx structures with silicon quantum dots are investigated by photoluminescence, electronic paramagnetic resonance, infrared absorption, and Raman-scattering methods. It is observed that oxidation of the silicon dots, change in the defect concentration in the oxide matrix, and oxidation of the silicon amorphous phase occur during storage in air at room temperature. A comparison of the variation of parameters of sputtered structures and porous silicon layers caused by the aging process is made. It is shown that the rate of oxidation of silicon dots and the decrease of their sizes in sputtered structures are essentially less than that in porous silicon. It is also shown that in Si–SiOx, layers in contrast to porous silicon, the intensity and spectral position of the emission band caused by exciton recombination in Si crystallites do not change practically during aging.
    Journal of Applied Physics 12/2005; 98(11):113515-113515-5. · 2.21 Impact Factor
  • Solid State Phenomena. 01/2005;
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    ABSTRACT: Photoluminescence and its temperature dependence, Raman scattering and photoluminescence excitation spectra for porous silicon, as well as their transformation during keeping in ambient air, have been investigated. The competition of different radiative channels was observed. It is shown that only one of them, that causes infrared emission band and dominates in as-prepared samples, is connected with excitonic recombination in Si nanocrystals. It is found that aging leads to an appearance of second radiative channel that causes red emission. Peculiarities of photoluminescence excitation and Raman scattering spectra, as well as of thermal quenching processes in porous silicon and the conditions for two radiative channel competitions are discussed.
    Journal of Luminescence 01/2005; 115:117-121. · 2.14 Impact Factor
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    ABSTRACT: The energy of the lowest singlet and triplet terms of shallow-level D − centers (two electrons bound at a singly charged Coulomb center) in semiconductors with ion bonding is theoretically analyzed. Electron-phonon interaction is described by the Fröhlich Hamiltonian. The D −-center energy is calculated by the Bu $\overset{\lower0.5em\hbox{$\overset{\lower0.5em\hbox{ mistrov-Pekar method of canonical transformations for an arbitrary coupling force with phonons. It was shown that, for the entire range of electron-phonon interaction parameters, the Bu $\overset{\lower0.5em\hbox{$\overset{\lower0.5em\hbox{ mistrov-Pekar method gives the lowest values of the ground-state energy of the D − centers and the free bipolaron in comparison with the best available numerical computations of these values which were performed using direct variational methods. The calculations showed the absence of both bound metastable triplet states, corresponding to the lowest triplet term of a D − center, and a bipolaron for the entire range of parameters of electron-phonon interaction. This is consistent with the Hill theorem concerning the absence of bound excited states of an H− ion.
    Semiconductors 02/2003; 37(3):302-306. · 0.60 Impact Factor
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    ABSTRACT: In CdS crystals, the influence of ultrasound (US) pulses on photocurrent, thermally stimulated current and edge emission spectra was observed. The effect was found to intensify with dislocation density. The analysis of obtained results showed that US treatment resulted in the decrease of shallow donor density in crystal bulk and its increase in near dislocation regions. This process of donor gettering by dislocations was shown to be one of the mechanisms of electron-beam-pumped CdS-based lasers degradation.
    Physica B Condensed Matter 01/2003; 340:258-262. · 1.28 Impact Factor
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    ABSTRACT: The theoretical consideration of the energy of the lowest singlet and triplet terms of shallow D – -centers (two electrons, bound with one-charge Coulomb center) in semiconduc-tors with an ionic and covalent binding has been carried out. The electron-phonon interaction is described by a Fröhlich Hamiltonian . The energy of D – -center is described with the use of a Buimistrov-Pekar method of canonical transformations for arbitrary electron-phonon cou-pling. It is shown, that for all area of electron-phonon interaction parameters the Buimistrov-Pekar method yields the lowest values of the ground state energy of D – -centers and free bipolaron in comparison with the best, for today, numerical calculations of the relevant values which have been carried out within the framework of the direct variation methods. The calculations have shown the lack of the bound metastable triplet states corresponding to the lowest triplet energy term of D – -center and bipolaron for all the area of electron-phonon interaction parameters, in complete analogy to the Hill theorem about the lack of the bound excited states of H – ion. It is shown that the account of interaction with acoustic phonons can produce considerable lowering the ground state energy of D – -center in comparison with the magnitude 1.0555Ry (where , 2 2 0 4 2 * * D ε e m Ry = m – is the effective mass of an electron, ε 0 – is a static permittivity of a crystal).
    Quantum Electronics & Optoelectronics. PACS. 01/2003; 6382080(73):269-273.
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    ABSTRACT: Diffusion of Li, Cu and Ag in CdS crystals was investigated in different crystallographic directions by means of a technique based on defect drift in an electric field. A considerable diffusion anisotropy was observed for Cu and Ag: perpendicular to the c-axis diffusion of the former about one order faster and diffusion of the latter is several times slower than parallel to the c-axis. A similar diffusion anisotropy was also found in CdSSe and ZnCdS crystals. Peculiarities of Cu and Ag diffusion are discussed.
    physica status solidi (b) 01/2002; 229:269-273. · 1.49 Impact Factor
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    ABSTRACT: Copper and silver related local centres in CdS crystals were investigated by means of technique based on drift of defects in external electric field. The impurities were first introduced in crystals and then extracted from them under electric field 100–300V/cm at 600–750K. Acceptors CuCd and AgCd responsible for emission bands 1000 and 610nm correspondingly were found to be the only local centres created after impurity incorporation. Local centres related to interstitials Cui and Agi were not revealed. Different photo-enhanced defect reactions were observed in the crystals before and after impurity incorporation. A transformation of the type of reaction as a result of impurity incorporation took place.
    Physica B Condensed Matter 01/2001; 308:967-970. · 1.28 Impact Factor
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    ABSTRACT: The enhancement of the Raman intensity from a porous layer compared to the signal from the silicon substrate was observed. It is assumed that this phenomenon is due to the specific form of pores that leads to the optical effect of focusing of scattered light near the bottom of the macropores. It was shown that the peak position and shape of the Raman line depend on the nanostructure of the pore bottom
    Advanced Semiconductor Devices and Microsystems, 2000. ASDAM 2000. The Third International EuroConference on; 02/2000
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    ABSTRACT: Photoluminescence excitation spectra consisted of two ultraviolet and one visible bands were observed. The spectra shape dependence on preparation regimes and aging in different environment show that visible excitation band is connected with light absorption by some adsorbed species, while two ultraviolet ones are due to defects in silicon oxide
    Semiconductor Conference, 1999. CAS '99 Proceedings. 1999 International; 02/1999

Publication Stats

119 Citations
69.08 Total Impact Points

Institutions

  • 1998–2005
    • National Academy of Sciences of Ukraine
      • V. E. Lashkaryov Institute of Semiconductor Physics
      Kiev, Misto Kyyiv, Ukraine
  • 1998–2003
    • Institute of Physics of the National Academy of Science of Ukraine
      Kievo, Kyiv City, Ukraine
  • 1992–1998
    • Ukrainian Academy of Agrarian Sciences
      Kievo, Kyiv City, Ukraine