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Dive into the research topics where N. N. Kononov is active.

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Featured researches published by N. N. Kononov.


Semiconductors | 2014

On the application of thin films of silicon nanoparticles for increasing solar cell efficiency

S. G. Dorofeev; N. N. Kononov; V. M. Zverolovlev; K. V. Zinoviev; V. N. Sukhanov; N. M. Sukhanov; B. G. Gribov

The effect of thin films of silicon nanoparticles (nc-Si), deposited onto the front surface of single-crystal silicon solar cells, on their conversion efficiency is studied. The thin films are grown using non-luminescent silicon nanoparticles with an average diameter of 12 nm with SiOx (0 ≤ x ≤ 2) shells and silicon nanoparticles 2 nm in diameter with organic shells of octadecene, which exhibit photoluminescence in the red spectral region. It was found that nc-Si film deposition increases the solar-cell conversion efficiency by 12% with respect to the initial value. An analysis of the current-voltage characteristics and reflectance spectra of solar cells allows the conclusion that the increase in the conversion efficiency is controlled by the passivation of defects on the front surface of the solar cell by nanoparticles and a decrease in the light reflectance of this surface.


Russian Journal of Physical Chemistry B | 2010

Immobilization of luminescent nanosilicon in a microfine polytetrafluoroethylene matrix by means of supercritical carbon dioxide

V. N. Bagratashvili; S. G. Dorofeev; A. A. Ischenko; V. V. Koltashev; N. N. Kononov; A. A. Krutikova; A. O. Rybaltovskii; G. V. Fetisov

With the use of supercritical carbon dioxide (SC-CO2), the matrix immobilization of photoluminescent silicon nanocrystals (nc-Si) in polytetrafluoroethylene microparticles (mp-PTFE) is performed, which leads to the formation of mp-PTFE/nc-Si photoluminescent nanocomposite containing ∼103–104 nc-Si particles per mp-PTFE particle (1–2 μm in size). This approach is based on the effect of polymer swelling in SC-CO2, efficient SC-CO2-assisted transport of nanoparticles into the internal free volume of the polymer, and contraction of the nanocomposite after the release of CO2, an effect that prevents the subsequent agglutination of nanoparticles. Particles of nc-Si photoluminescent in the visible spectrum were synthesized from silicon suboxide powder (SiOx, x ≈ 1) heated at various temperatures within 25–950°C and then etched in concentrated hydrofluoric acid. The hydrosilylation procedure was used to graft 1-octadecene molecules to the surface of nc-Si particles. As a result, the photoluminescence intensity of nc-Si increased substantially. According to TEM images and small angle X-ray scattering data, the maximum size of nc-Si particles did not exceed 5 nm and 7 nm, respectively, and the core of these nanoparticles consisted of crystalline silicon. The structure and spectral properties of the initial nc-Si particles and synthesized mp-PTFE/nc-Si photoluminescent nanocomposite microparticles were studied.


Journal of Analytical Chemistry | 2009

Gas sensitivity of etioporphyrin metal complexes in thin films

M. A. Goldshtrakh; N. N. Kononov; S. G. Dorofeev; A. A. Ischenko

It is shown that porphyrin metal complexes have the potential for the creation of various gas sensors; the gas sensing properties of the materials on their basis change upon the replacement of the central metal atom and substituents in the porphyrin core. Films of etioporphyrin-II were prepared by vacuum deposition onto a front shaft system of electrodes on a pyroceramic support. Calibration dependences of the analytical signal (conductivity) on the concentration of ammonia were obtained. It was found that UV irradiation on the sensor layer enhances the sensitivity of ammonia determination. Relative sensitivities of thin films based on Co(II), Ni(II), Cu(II), Zn(II), Pd(II) and Pt(II) etioporphyrin complexes in the temperature range from 303 K to 423 K and ammonia concentrations from 1.5 to 75 mg/m3 were determined. The relative sensitivity attains a maximum (0.8) at an ammonia concentration of 7.5 mg/m3 for the Co(II) etioporphyrin at 333 K in a dark mode, or at 303 K and under UV irradiation (λ = 406 nm, P = 1 mW). An experimental setup was assembled that allowed measurements at the controlled temperature and humidity of the gas and its mixtures with inert gases or air. The conditions of ammonia detection were optimized.


Semiconductors | 2011

Dielectric and transport properties of thin films precipitated from sols with silicon nanoparticles

N. N. Kononov; S. G. Dorofeev; A. A. Ishchenko; R. A. Mironov; V. G. Plotnichenko; Evgenii M Dianov

Dielectric properties of thin films precipitated on solid substrates from colloidal solutions containing silicon nanoparticles (average diameter is 10 nm) are studied by optical ellipsometry and impedance-spectroscopy. In the optical region, the values of real ɛ′ and imaginary ɛ″ components of the complex permittivity ɛ vary within 2.1–1.1 and 0.25–0.75, respectively. These values are significantly lower than those of crystalline silicon. Using numerical simulation within the Bruggeman effective medium approximation, we show that the experimental ɛ′ and ɛ″ spectra can be explained with good accuracy, assuming that the silicon film is a porous medium consisting of silicon monoxide (SiO) and air voids at a void ratio of 0.5. Such behavior of films is mainly caused by the effect of outer shells of silicon nanoparticles interacting with atmospheric oxygen on their dielectric properties. In the frequency range of 10–106 Hz, the experimentally measured ɛ′ and ɛ″ spectra of thin nanoscale silicon films are well approximated by the semi-empirical Cole-Cole dielectric dispersion law with the term related to free electric charges. The experimentally determined power-law frequency dependence of the ac conductivity means that the electrical transport in films is controlled by electric charge hopping through localized states in the unordered medium of outer shells of silicon nanoparticles composing films. It is found that the film conductivity at frequencies of ≤2 × 102 Hz is controlled by proton transport through Si-OH groups on the silicon nanoparticle surface.


Semiconductors | 2009

Optical and structural properties of thin films precipitated from the sol of silicon nanoparticles

S. G. Dorofeev; N. N. Kononov; A. A. Ishchenko; R. B. Vasil’ev; M. A. Goldschtrakh; K. V. Zaitseva; V. V. Koltashev; V. G. Plotnichenko; O. V. Tikhonevich

A new technique of growing nanocrytalline silicon (nc-Si) thin films is suggested. The technique involves the centrifuge-assisted size-selective deposition of nanoparticles from a colloidal solution (sol) containing nc-Si powders. The structural and optical parameters of the initial nc-Si powders and films deposited by the newly suggested procedure are studied by transmission electron microscopy and analysis of absorption spectra and Raman spectra. The absorption coefficient of the nc-Si films increases with decreasing dimensions of the constituent nanoparticles. The experimentally measured band gap of the films, Eg, is widened from 1.8 to 2.2. eV on etching the nc-Si powders used for deposition of the corresponding films. On the basis of the analysis of the Raman spectra, it is suggested that the amorphous component is involved in the nc-Si powders and films due to oxygen atoms arranged at the nanoparticle surface.


Semiconductors | 2005

Optical and electrical properties of thin wafers fabricated from nanocrystalline silicon powder

N. N. Kononov; G. P. Kuz’min; A. N. Orlov; A.A. Surkov; O. V. Tikhonevich

The infrared transmittance spectra and dark conductivity of wafers fabricated from nanocrystalline silicon powder (nc-Si) have been studied. The initial nc-Si powder is first synthesized by laser-induced silane dissociation, with the temperature of the surrounding buffer gas varied from 20 to 250°C, and then compacted at pressures from 108 to 109 Pa. It is found that compaction of the nc-Si powder results in formation of Si-H, Si-CHx, and Oy-Si-Hx structures (x, y=1–3). The formed structures break down under annealing, with the Si-H and Si-CHx complexes disintegrating at the lowest annealing temperature (t = 160°C). The dark conductivityof the nc-Si wafers is shown to increase along with the buffer gas temperature at which the starting powder was prepared. Two temperature regions are found in which the dark conductivity behaves in radically different ways. At wafer temperatures T ≥ 270 K, conductivity is mediated by free carriers, whereas, at lower temperatures, electron transport is governed by hopping conduction over localized states in the band gap.


Russian Journal of Physical Chemistry A | 2009

A comparative analysis of the influence of photo- and thermal activation on the sensor properties of cobalt(II) etioporphyrin films

M. A. Gol’dshtrakh; S. G. Dorofeev; A. A. Ishchenko; Yu. M. Kiselev; N. N. Kononov

A comparative analysis of dark conductivity and photoconductivity of cobalt(II) etioporphyrin, Co(II)EP, thin films in the presence of various gases was performed. The major contribution to conductivity of both types was made by oxygen molecules adsorbed on the surface of the gas sensitive layer. The concentration of adsorbed oxygen molecules increased under light action on the surface of films, which increased film conductivity at the given temperature. Light action could be used to reach maximum sensor sensitivity of Co(II)EP films toward ammonia at room temperature.


RSC Advances | 2018

Diffusion doping route to plasmonic Si/SiOx nanoparticles

Sergei S. Bubenov; S. G. Dorofeev; A. A. Eliseev; N. N. Kononov; A.V. Garshev; Natalia E. Mordvinova; Oleg I. Lebedev

Semiconductor nanoparticles (SNPs) are a valuable building block for functional materials. Capabilities for engineering of electronic structure of SNPs can be further improved with development of techniques of doping by diffusion, as post-synthetic introduction of impurities does not affect the nucleation and growth of SNPs. Diffusion of dopants from an external source also potentially allows for temporal control of radial distribution of impurities. In this paper we report on the doping of Si/SiOx SNPs by annealing particles in gaseous phosphorus. The technique can provide efficient incorporation of impurities, controllable with precursor vapor pressure. HRTEM and X-ray diffraction studies confirmed that obtained particles retain their nanocrystallinity. Elemental analysis revealed doping levels up to 10%. Electrical activity of the impurity was confirmed through thermopower measurements and observation of localized surface plasmon resonance in IR spectra. The plasmonic behavior of etched particles and EDX elemental mapping suggest uniform distribution of phosphorus in the crystalline silicon cores. Impurity activation efficiencies up to 34% were achieved, which indicate high electrical activity of thermodynamically soluble phosphorus in oxide-terminated nanosilicon.


Semiconductors | 2017

Characteristics of the Schottky barriers of two-terminal thin-film Al/nano-Si film/ITO structures

N. N. Kononov; S. G. Dorofeev

The temperature dependence of the Schottky-barrier height and series resistance of two-terminal thin-film Al/nano-Si film/ITO structures are determined from the current—voltage (I–V) characteristics in the temperature range of 20–150°C. It is found that the form of the I–V characteristic at all investigated temperatures can be described by a model of two Schottky diodes connected back-to-back. For these diodes, the general formula is obtained, which allows the construction of functions approximating experimental curves with high accuracy. Based on this formula, a computational model is built, which generalizes the theoretical data obtained by S.K. Cheung and N.W. Cheung widely used for analyzing the I–V characteristics of single Schottky diodes. A technique is developed for calculating the Schottky-barrier heights in a system of two Schottky diodes connected back-to-back, their ideality factors, and the series resistance of the system. It is established that the barrier heights in the investigated temperature range are ~1 eV. According to the temperature dependence of the barrier height, such large values result from the presence of a SiOx (0 ≤ x ≤ 2) oxide layer at the nanoparticle boundaries. Charge carriers can overcome this layer by means of thermal excitation or tunneling. It is established that the intrinsic Schottky-barrier height of the Al/nc-Si film and nc-Si film/ITO junctions is ~0.1 eV. The activation dependences of the series resistance of the Al/nc-Si film/ITO structures and impedance spectra show that combined electric-charge transport related to ionic and electronic conductivity takes place in the structures under study. It is shown that the contribution of the electronic conductivity to the total transport process increases as the sample temperature is raised.


Semiconductors | 2017

Production of Silicon Nanoparticles for Use in Solar Cells

B. G. Gribov; K. V. Zinov’ev; O. N. Kalashnik; N. N. Gerasimenko; D. I. Smirnov; V. N. Sukhanov; N. N. Kononov; S. G. Dorofeev

The technological process of the production of silicon nanoparticles from silicon monoxide and methods of the deposition of nanosilicon coatings onto solar cells are developed. The process makes it possible to control the particle dimensions in the range from 2 to 10 nm. The effect of such nanosilicon coatings on the efficiency of solar cells is studied. It is shown that nanosilicon films possess good antireflection and passivation properties and can be successfully used in the technology of the production of solar cells.

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O. V. Tikhonevich

Russian Academy of Sciences

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A.A. Surkov

Russian Academy of Sciences

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V. G. Plotnichenko

Russian Academy of Sciences

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V. N. Sukhanov

National Research University of Electronic Technology

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V. V. Koltashev

Russian Academy of Sciences

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A. N. Orlov

Russian Academy of Sciences

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