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Каражанов, Смагул Жангабергенович

Организационные подразделения

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Цель ИЯФиТ и стратегия развития - создание и развитие научно-образовательного центра мирового уровня в области ядерной физики и технологий, радиационного материаловедения, физики элементарных частиц, астрофизики и космофизики.

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Каражанов

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Смагул Жангабергенович

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In-situ composition analysis of photochromic yttrium oxy-hydride thin films under light illumination
(2019) Moro, M. V.; You, C. C.; Baba, E. M.; Primetzhofer, D.; Moldarev, D.; Karazhanov, S. Z.; Wolff, M.; Каражанов, Смагул Жангабергенович
© 2019 Elsevier B.V.In this work, we investigate the chemical composition of a reactively sputtered photochromic YHxOy thin film by non-destructive ion beam-based techniques, i.e., Rutherford Backscattering Spectrometry, Particle-Induced X-Ray Emission, Time-of-Flight/Energy coincidence Elastic Recoil Detection Analysis and Elastic Backscattering Spectrometry. To enhance the accuracy of the analysis, the set of spectra was evaluated in an iterative self-consistent approach. This procedure resulted in high-resolution depth profiles of the chemical composition and revealed a thin oxygen-rich-layer on the surface, which apparently does not act as a self-passivation layer. In the film, the concentration of Y remains practically constant, whereas O replaces H during the oxidation process. In-situ light illumination was performed during the compositional analysis in a high vacuum setup. The results from these measurements demonstrate that, for these samples, the induced reversible photochromism is not linked to any detectable change in the bulk composition of the film and can thus take place even in a vacuum environment.
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Carbon-dioxide as annealing atmosphere to retain the electrical properties of indium-tin oxide
(2020) Mayandi, J.; Finstad, T. G.; Venkatesan, R.; Ponniah, V.; Karazhanov, S.; Venkatachalapathy, V.; Каражанов, Смагул Жангабергенович; Венкатачалапатху, Вишнукантхан
© 2020 Elsevier B.V.In practical applications of indium-tin-oxide (ITO), annealing at temperatures ~400 °C without degrading its electrical and optical properties is an important challenge. In the present work, commercial Indium-tin oxide (ITO) coated on glass was subjected to post-annealing treatment in the range of 200–400 °C at different annealing atmospheres; oxygen, nitrogen and carbon-dioxide. The annealed samples were characterized by X-ray diffraction, UV–visible spectroscopy and Hall measurements to evaluate the structural, optical and electrical properties. Both oxygen and nitrogen treated samples demonstrate degradation in structural, optical and conducting properties of ITO, while carbon-dioxide atmosphere inhibits the degradation of ITO at 400 °C. The obtained results suggest that carbon-dioxide can be well utilized as annealing ambient to retain opto-electronic and structural properties of ITO and thereby improve the efficiency of ITO based solar cells.
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Preferential Orientation of Photochromic Gadolinium Oxyhydride Films
(2020) Baba, E. M.; Montero, J.; Moro, M. V.; Primetzhofer, D.; Moldarev, D.; Wolff, M.; Karazhanov, S.; Каражанов, Смагул Жангабергенович
We report preferential orientation control in photochromic gadolinium oxyhydride (GdHO) thin films deposited by a two-step process. Gadolinium hydride (GdH2-x) films were grown by reactive magnetron sputtering, followed by oxidation in air. The preferential orientation, grain size, anion concentrations and photochromic response of the films were strongly dependent on the deposition pressure. The GdHO films showed a preferential orientation along the [100] direction and exhibited photochromism when synthesized at deposition pressures of up to 5.8 Pa. The photochromic contrast was larger than 20% when the films were deposited below 2.8 Pa with a 0.22 H2/Ar flow ratio. We argue that the relation of preferential orientation and the post deposition oxidation since oxygen concentration is known to be a key parameter for photochromism in rare-earth oxyhydride thin films. The experimental observations described above were explained by the decrease of the grain size as a result of the increase of the deposition pressure of the sputtering gas, followed by a higher oxygen incorporation.
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Photochromic properties of yttrium oxyhydride thin films: Surface versus bulk effect
(2020) Baba, E. M.; Moro, M. V.; You, C. C.; Primetzhofer, D.; Moldarev, D.; Wolff, M.; Karazhanov, S. Z.; Каражанов, Смагул Жангабергенович
© 2020Photochromic yttrium oxyhydride (YHO) films of different thicknesses but similar chemical composition were grown by reactive magnetron sputtering. Photochromic response of the films defined as the relative change in transmittance upon illumination increases almost linearly with thickness for films below 600 nm and saturates (≈ 50%) for thicker ones. These results suggest that the photochromic effect on YHO films has a bulk nature and might be limited by material transport on the microscale.
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Visible light-assisted instability of kesterite Cu2ZnSnS4: What are the implications?
(2020) Kois, J.; Polivtseva, S.; Samieipour, A.; Mamedov, D.; Karazhanov, S. Z.; Каражанов, Смагул Жангабергенович
© 2019The development of efficient photovoltaic devices utilizing durable and cost-effective materials such as CZTS and similar ones represents a big challenge. Here, the comparison of thermodynamic calculations and electrochemical experiments reveals detrimental degradation of CZTS regardless of pH values and potentials applied. Cathodic polarization yields to the full decomposition of CZTS, while anodic polarization stabilizes partly CZTS by passivation of its surface with less-active phases. The presence of water, in general, provokes the decomposition of CZTS to various undesired phases which most likely affect the device parameters. The possible mechanism for the degradation of CZTS is proposed considering its electronic structure. Certain similarities on unfavorable processes occurring with analogous materials are expected.
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Influence of Si-nanoparticles on PEDOT:PSS properties for hybrid solar cells
(2019) Mamedov, D.; You, C. C.; Karazhanov, S. Z.; Marstein, E. S.; Каражанов, Смагул Жангабергенович
Hole-conducting poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) is a material receiving increasing interest for use in photovoltaic devices. In this work, we present the results of study of the degradation of the optical and electrical properties of pure PEDOT:PSS and PEDOT:PSS doped with Si-nanoparticles. The PEDOT:PSS has been deposited on top of Si wafers by spin coating. We found that incorporation of Si nanoparticles into PEDOT:PSS enhances the surface passivation of the surface of the Si wafer by increasing the carrier lifetime measured by the photoluminesence quasi-steady state photoconductance (PL QSS-PC) method from about 320 ms to 420 ms at a minority carrier injection level of 2*10(15) cm(-3). Analysis showed that incorporation of the Si nanoparticles does not change the kinetics of degradation of lifetime considerably. (c) 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the E-MRS Fall Meeting, 2019. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
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Electrical and optical properties of composite PEDOT:PSS-based thin films with NiO nanoparticles
(2019) Moldarev, D.; Taeno, M.; Maestre, D.; Cremades, A.; Karazhanov, S. Z.; Каражанов, Смагул Жангабергенович
Due to the combination of low cost materials deposition and device fabrication methods as well as competitive efficiency compared to the other Si solar cell architectures, the hybrid organic-silicon solar cells have attracted attention of the scientific community. It has recently been demonstrated that spin-coated poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (hereafter PEDOT:PSS) on a silicon wafer is a promising material due to its good optical and electrical properties. However, degradation caused by atmospheric exposure and relatively poor passivation properties limits implementation of PEDOT:PSS- silicon devices. Functionalization of PEDOT:PSS by inorganic nanoparticles might provide a possible solution as was shown for TiO2 and SnO2 nanoparticles. In this contribution, we present our results on spincoated PEDOT:PSS thin-films with NiO nanoparticles. We show that PEDOT:PSS mixed with Triton X-100 and dimethyl sulfoxide (DMSO) or ethylene glycol (EG) form a homogenous film and passivates the Si surface with charge carrier lifetimes of 300-400 ms with good reproducibility. Time-resolved measurements revealed continuous degradation of the passivation properties in air, however saturation of the degradation at approximately 150 ms was observed in N-2 atmosphere. The influence of the NiO nanoparticles on the optical properties of PEDOT:PSS is negligible, whereas the surface passivation properties are worsened due probably to the formation of large size agglomerates exceeding thickness of PEDOT:PSS film. (c) 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the E-MRS Fall Meeting, 2019.
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Methods of estimations of the band gap for kesterite Cu2ZnSnS(Se)(4)
(2019) Mamedov, D.; Yakubov, K.; Bazarbaev, R. B.; Ismailov, K.; Karazhanov, S.; Каражанов, Смагул Жангабергенович
This paper presents a study related to methods of estimation of the band gap for kesterite-type Cu2ZnSnS (Se)(4) based on their electronic structure and optical properties driven by the first-principles calculations within the hybrid functional. The estimations have been performed by four different methods. The first one is based on the band structure estimated as the difference of the energy corresponding to the conduction band and valence band edges. The rest three methods are based on the spectral distribution of the absorption coefficient a(hx) driven from the first-principles calculations: (i) Tauc plot, (ii) first derivative of a(hx) on photon energy hx in the energy range around the fundamental absorption edge, and (iii) linear combination of the methods (i) and (ii). We show that the band gap estimated by different methods can deviate each from other drastically and the large difference is not only relayed to defects, impurities and other lattice imperfections. We show also, that the influence of lattice anisotropy on optical properties of CZTS and CZTSe is negligible. We have pointed out importance of the dependence of dielectric constant on surface texture. The equation describing dependence of dielectric constant on the experimentally observed surface texture is derived. (c) 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the E-MRS Fall Meeting, 2019.
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Thin Ta/Ta oxide core-shell nanoparticle film size-dependent energy structure
(2021) Borisyuk, P. V.; Vasilyev, O. S.; Lebedinskii, Y. Y.; Bortko, D. V.; Karazhanov, S.; Борисюк, Петр Викторович; Васильев, Олег Станиславович; Лебединский, Юрий Юрьевич; Бортко, Диана Владимировна; Каражанов, Смагул Жангабергенович
© 2020 Elsevier B.V.The paper presents the research of thin films, consisting of spherical monodisperse Ta particles. For different samples particle sizes varied from 1.3 nm to 5.8 nm. The films were also exposed to the atmosphere for oxidation, which resulted in formation of a core-shell particle structure, where core was metal and shell was Ta oxide (Ta2O5). Dependency of bandgap Egap and valence band offset (VBO) on particle size has been investigated for the structure by using the X-ray photoelectron spectroscopy (XPS) and reflected electron energy loss spectroscopy (REELS) methods. We have found, that Egap decreases from 4.72 eV to 4.47 eV whereas VBO decreases from 3.50 eV to 2.95 eV with increasing the particle size. A new method of a fine regulation of the electronic structure is suggested, particularly for the application in ultraviolet (UV) photodetector design for low-lying nuclear and electron transitions detection.
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Comparative analysis of photothermal boiling of water enhanced by nano- and micro-particles of carbon black
(2021) Ulset, E. T.; Kosinski, P.; He, Y.; Struchalin, P. G.; Karazhanov, S. Z.; Balakin, B. V.; Стручалин, Павел Геннадьевич; Каражанов, Смагул Жангабергенович
© 2020 Elsevier B.V.The paper describes the effect of sodium dodecyl sulfate (SDS) on the steam generation during photothermal boiling of carbon nanofluids. The considered process finds promising applications for e.g. solar desalination where SDS may boost steam generation. Our study was carried out in a lab system boiling aqueous suspensions of carbon by means of artificial thermal radiation. The experiments demonstrate that the newly-produced nanofluids turn into suspension when no SDS is present in the fluid. The agglomeration of nanoparticles reduces the stability of the system yet degrades the steam generation by no more than 8.2%. The optimum particle concentration was about 2% wt. independently of whether SDS was present in samples. The steam was superheated by up to 12 K when using the surfactant which was 5–7 K higher than without SDS. The experimental data was supported by a theoretical analysis.