V. A. Krivchenko
Moscow State University
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Featured researches published by V. A. Krivchenko.
Journal of Applied Physics | 2010
V. A. Krivchenko; Andrey Pilevsky; A.T. Rakhimov; B.V. Seleznev; N. V. Suetin; M.A. Timofeyev; Bespalov Av; O. L. Golikova
Electron field emission properties of nanocrystalline graphite (NCG) films, grown by plasma enhanced chemical vapor deposition method on conductive Si substrates without using of any catalyst, were investigated. Current-voltage characteristics were measured in pulse-periodic regime. It was shown that grown NCG films can operate at field emission current density up to 10 A/cm2. It was found that NCG films contain, along with the normally oriented to the substrate nanoflakes, carbon whiskers consisted of graphene nanoribbons and nanowires with length considerably higher than of the nanoflakes.Electron field emission properties of nanocrystalline graphite (NCG) films, grown by plasma enhanced chemical vapor deposition method on conductive Si substrates without using of any catalyst, were investigated. Current-voltage characteristics were measured in pulse-periodic regime. It was shown that grown NCG films can operate at field emission current density up to 10 A/cm2. It was found that NCG films contain, along with the normally oriented to the substrate nanoflakes, carbon whiskers consisted of graphene nanoribbons and nanowires with length considerably higher than of the nanoflakes.
Scientific Reports | 2013
V. A. Krivchenko; Stanislav A. Evlashin; K. V. Mironovich; N. I. Verbitskiy; Alexei Nefedov; Christof Wöll; A. Ya. Kozmenkova; N. V. Suetin; S.E. Svyakhovskiy; D. V. Vyalikh; A.T. Rakhimov; A. V. Egorov; L. V. Yashina
The optical properties of carbon nanowall (CNW) films in the visible range have been studied and reported for the first time. Depending on the film structure, ultra-low total reflectance up to 0.13% can be reached, which makes the CNW films a promising candidate for the black body-like coating, and thus for a wide range of applications as a light absorber. We have estimated important trends in the optical property variation from sample to sample, and identified the presence of edge states and domain boundaries in carbon nanowalls as well as the film mass density variation as the key factors. Also we demonstrated that at much lower film thickness and density than for a carbon nanotube forest the CNWs yield one order higher specific light absorption.
Journal of Materials Chemistry | 2012
V. A. Krivchenko; Pavel Shevnin; Andrey Pilevsky; Aleksander Egorov; N. V. Suetin; Vasiliy Sen; Stanislav A. Evlashin; Aleksander Rakhimov
Nanocrystalline graphite films composed of carbon nanowalls and cone-shaped carbon nanotubes have been synthesized without the use of any catalyst by means of plasma enhanced chemical vapor deposition in the plasma of direct current glow discharge. The effect of growth temperature on the structural and field emission properties of the nanocrystalline graphite films has been studied. It was demonstrated that variation of the surface temperature during plasma synthesis dramatically affects carbon nanowall and nanotube structural features. Moreover, higher growth temperature results in higher stability of the electron field emission properties of nanocrystalline graphite films.
ACS Nano | 2015
Elmar Yu. Kataev; Daniil M. Itkis; Alexander Fedorov; Boris Senkovsky; D. Usachov; N. I. Verbitskiy; A. Grüneis; Alexei Barinov; Daria Yu. Tsukanova; A. A. Volykhov; K. V. Mironovich; V. A. Krivchenko; Maksim G. Rybin; Elena D. Obraztsova; C. Laubschat; D. V. Vyalikh; L. V. Yashina
Oxygen reduction reaction (ORR) plays a key role in lithium-air batteries (LABs) that attract great attention thanks to their high theoretical specific energy several times exceeding that of lithium-ion batteries. Because of their high surface area, high electric conductivity, and low specific weight, various carbons are often materials of choice for applications as the LAB cathode. Unfortunately, the possibility of practical application of such batteries is still under question as the sustainable operation of LABs with carbon cathodes is not demonstrated yet and the cyclability is quite poor, which is usually associated with oxygen reduced species side reactions. However, the mechanisms of carbon reactivity toward these species are still unclear. Here, we report a direct in situ X-ray photoelectron spectroscopy study of oxygen reduction by lithiated graphene and graphene-based materials. Although lithium peroxide (Li2O2) and lithium oxide (Li2O) reactions with carbon are thermodynamically favorable, neither of them was found to react even at elevated temperatures. As lithium superoxide is not stable at room temperature, potassium superoxide (KO2) prepared in situ was used instead to test the reactivity of graphene with superoxide species. In contrast to Li2O2 and Li2O, KO2 was demonstrated to be strongly reactive.
Langmuir | 2015
Natal’ya S. Komarova; A. G. Krivenko; E. V. Stenina; L. N. Sviridova; K. V. Mironovich; Yuri M. Shulga; V. A. Krivchenko
The effects of electrochemical oxidation and surfactant adsorption on behavior of vertically oriented carbon-nanowall (CNW)-based electrodes are studied. Electrochemical oxidation is carried out by the electrode polarization in aqueous solutions at high anodic potentials corresponding to water electrolysis, whereas the modification of surface by surfactants is accomplished by the adsorption of molecules characterized by the cage-like structure. Using the methods of cyclic voltammetry and impedancemetry, it is shown that a substantial increase in the capacitance of CNW-based electrodes is observed in both cases (30-50-fold and 3-5-fold, respectively). The as-grown and modified electrodes are characterized by scanning electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. A substantial increase in a number of oxygen-containing functional groups is observed on the CNW surface after the electrode polarization at high anodic potentials. The kinetics of redox reactions on the CNW film surface is studied by comparing the behavior of systems [Ru(NH3)6](2+/3+), [Fe(CN)6](4-/3-), Fe(2+/3+), and VO3(-)/VO(2+). It is demonstrated that oxidation of nanowalls makes the electron transfer in the redox reaction VO3(-)/VO(2+) and the redox system Fe(2+/3+) considerably easier due to coordination of discharging ions of these systems with the functional groups; however, no such effect is observed for the redox-systems [Fe(CN)6](3-/4-) and [Ru(NH3)6](2+/3+).
Journal of Vacuum Science & Technology. B. Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena | 2012
Stanislav A. Evlashin; Yuri A. Mankelevich; Vladimir V. Borisov; Andrey A. Pilevskii; A.S. Stepanov; V. A. Krivchenko; N. V. Suetin; A.T. Rakhimov
For the past two decades various methods of carbon nanostructures growth have been proposed. Special substrate pretreatment methods are generally used to grow carbon nanowalls on silicon substrates and among them are mechanical and catalytic methods and ion bombardment in an rf discharge with bias. This work describes the possibility of growing carbon structures on porous silicon in a dc discharge without any additional pretreatment of the substrate surface. Carbon structures were grown on n- and p-type (100) porous silicon substrates produced by using standard photoelectrochemical etching. The analysis of these carbon structures revealed nanocrystalline carbon with multilayer carbon nanotubes and fibers. All samples demonstrated low field emission thresholds (Etr < 3 V/μm) and high current densities, showing an achieved current density of more than 6 A/cm2 for an electric field of E ∼ 15 V/μm. The authors investigated various modifications of porous silicon samples and carbon structures and demonstrated ...
Technical Physics | 2008
V. A. Krivchenko; D. V. Lopaev; P. V. Pashchenko; V. G. Pirogov; A.T. Rakhimov; N. V. Suetin; A.S. Trifonov
Nanocrystalline films of zinc oxide deposited by rf magnetron sputtering are used as a working material of UV detectors. The photoelectric performance of UV detectors versus ZnO deposition conditions is studied. The influence of the surface topology of the UV detectors on their efficiency is examined with an atomic force microscope.
Technical Physics | 2007
V. A. Krivchenko; D. V. Lopaev; P. V. Minakov; V. G. Pirogov; A.T. Rakhimov; N. V. Suetin
The effect of the degree of doping polycrystalline diamond films by boron on their Raman and absorption spectra has been studied in the visible region (from 200 to 1000 nm). As the boron concentration increases in a polycrystalline diamond film, its Raman spectrum exhibits a number of new specific features caused by the effect of boron atoms on the diamond lattice. The dependences that relate these features to the boron concentration in the films are given. Moreover, the absorption spectra of the films have revealed a peak whose maximum corresponds to photons with an energy near 2 eV.
Technical Physics Letters | 2012
Pavel V. Voronin; V. A. Krivchenko; Daniil M. Itkis; Dmitry A. Semenenko; A.T. Rakhimov
Films of nanocrystalline graphite were synthesized in dc discharge plasma in an atmosphere of methane and hydrogen. Studies of the structural properties show that the films consist of a dense set of nanowalls with a thickness of 10–15 nm oriented perpendicularly to the support surface. The synthesized films were used as an active electrode material in supercapacitors. It is shown that the specific electrochemical capacitance of the synthesized material reaches about 38 mF/cm2.
Russian Journal of Electrochemistry | 2015
A. G. Krivenko; Natal’ya S. Komarova; E. V. Stenina; L. N. Sviridova; K. V. Mironovich; Yu. M. Shul’ga; R. A. Manzhos; S. V. Doronin; V. A. Krivchenko
The original and modified vertically oriented carbon nanowalls (CNWs) were applied onto conducting substrates by the plasma-chemical method. Their electrochemical behavior was studied by the methods of cyclic voltammetry and impedance measurements. The modified and original electrodes were characterized by using the methods of scanning and transmitting electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. The nanowalls were modified with the functional groups (FG) via the electrolysis of aqueous solutions at the anodic potentials. Their adsorption properties were studied in the solutions of organic surfactants with the skeleton structure. It is shown that, in the first case, the number of oxygen-containing FG on the CNW surface significantly increases and, in both cases, the electrode capacitance considerably increases (by 30–50 and 3–5 times, respectively). A correlation between the rate constants k0 of [Ru(NH3)6]2+/3+, [Fe(CN)6]4–/3–, and Fe2+/3+ redox reactions and a degree of nanowall surface functionalization is revealed. The values of k0 were estimated in the automatic mode using a specially developed program by comparing the potential differences between the peaks of cyclic voltammograms ΔE, which were measured in a wide range of potential scan rate v, and the calculated ΔE (k0, v) dependences, which were obtained by solving the corresponding diffusion equations. It is shown that the functionalization of CNWs leads to a substantial (by ~103 times) increase in k0 for the Fe2+/3+ redox system and has almost no effect on the electron transfer in the [Fe(CN)6]3–/4– and [Ru(NH3)6]2+/3+ systems.