Alexander Butenko - Academia.edu (original) (raw)

Papers by Alexander Butenko

Small, May 31, 2023

Oil‐in‐water emulsion droplets spontaneously adopt, below some temperature Td, counterintuitive f... more Oil‐in‐water emulsion droplets spontaneously adopt, below some temperature Td, counterintuitive faceted and complex non‐spherical shapes while remaining liquid. This transition is driven by a crystalline monolayer formed at the droplets' surface. Here, we show that ppm‐level doping of the droplet's bulk by long‐chain alcohols allows tuning Td by >50 °C, implying formation of drastically different interfacial structures. Furthermore, “magic” alcohol chain lengths maximize Td. This we show to arise from self‐assembly of mixed alcohol:alkane interfacial structures of stacked alkane layers, co‐crystallized with hydrogen‐bonded alcohol dimers. These structures are accounted for theoretically and resolved by direct cryogenic transmission electron microscopy (cryoTEM), confirming the proposed structures. The discovered tunability of key properties of commonly‐used emulsions by minute concentrations of specific bulk additives should benefit these emulsions' technological applicability.

Graphene, 2015

Gradual localization of charge carriers was studied in a series of micro-size samples of monolaye... more Gradual localization of charge carriers was studied in a series of micro-size samples of monolayer graphene fabricated on the common large scale film and irradiated by different doses of C + ions with energy 35 keV. Measurements of the temperature dependence of conductivity and magnetoresistance in fields up to 4 T showed that at low disorder, the samples are in the regime of weak localization and antilocalization. Further increase of disorder leads to strong localization regime, when conductivity is described by the variable-range-hopping (VRH) mechanism. A crossover from the Mott regime to the Efros-Shklovskii regime of VRH is observed with decreasing temperature. Theoretical analysis of conductivity in both regimes showed a remarkably good agreement with experimental data.

Physical Review B, 2015

Raman scattering (RS) spectra and current-voltage characteristics at room temperature were measur... more Raman scattering (RS) spectra and current-voltage characteristics at room temperature were measured in six series of small samples fabricated by means of electron-beam lithography on the surface of a large size (5x5 mm) industrial monolayer graphene film. Samples were irradiated by different doses of C + ion beam up to 10 15 cm −2. It was observed that at the utmost degree of disorder, the Raman spectra lines disappear which is accompanied by the exponential increase of resistance and change in the current-voltage characteristics. These effects are explained by suggestion that highly disordered graphene film ceases to be a continuous and splits into separate fragments. The relationship between structure (intensity of RS lines) and sample resistance is defined. It is shown that the maximal resistance of the continuous film is of order of reciprocal value of the minimal graphene conductivity πh/4e 2 ≈ 20 kOhm.

Applied Physics Letters, 1999

... In order to increase the EFE in the Bi films it is neces-sary to break the near equality and ... more ... In order to increase the EFE in the Bi films it is neces-sary to break the near equality and to make p / n gn /gp in Eq. 2. There are several ways to achieve this: 1 modi-fying the scattering mechanism, or more exactly, changing the dependence of p / n on the effective masses. ...

Physical Review B

The conductivity and Hall effect were measured in CVD-grown monolayer graphene as a function of t... more The conductivity and Hall effect were measured in CVD-grown monolayer graphene as a function of the gate voltage, Vg, at temperatures down to T = 2 K and in magnetic fields up to B = 8 T. The minimal conductivity was observed at positive Vg which shows the position of the charge neutrality point, VNP. With decreasing T , VNP first decreases, but stop to decrease at low T. Hysteresis of conductivity shows similar behavior: it decreases with decreasing T and disappears at low T. A significant asymmetry was observed at low density of charge carriers |n| = (n, p): mobility of holes was less than mobility of electrons. The asymmetry decreases with increasing |n|. It was observed that the value of |n| determined from the Hall effect is less than the full value induced by Vg. In strong perpendicular B, Shubnikov-de Haas (SdH) oscillations were observed in the longitudinal conductivity, σxx, together with half-integer quantum Hall plateaus. It was found that |n| determined from SdH oscillations is equal to the full value induced by Vg as opposed to the Hall effect. Explanatory models for all observed phenomena are discussed.

Langmuir : the ACS journal of surfaces and colloids, Jan 21, 2017

Confocal microscopy is widely used for three-dimensional (3D) sample reconstructions. Arguably, t... more Confocal microscopy is widely used for three-dimensional (3D) sample reconstructions. Arguably, the most significant challenge in such reconstructions is posed by the resolution along the optical axis being significantly lower than in the lateral directions. In addition, the imaging rate is lower along the optical axis in most confocal architectures, prohibiting reliable 3D reconstruction of dynamic samples. Here, we demonstrate a very simple, cheap, and generic method of multiangle microscopy, allowing high-resolution high-rate confocal slice collection to be carried out with capillary-contained colloidal samples in a wide range of slice orientations. This method, realizable with any common confocal architecture and recently implemented with macroscopic specimens enclosed in rotatable cylindrical capillaries, allows 3D reconstructions of colloidal structures to be verified by direct experiments and provides a solid testing ground for complex reconstruction algorithms. In this paper...

Journal of Applied Physics, 1997

The electrical field effect (EFE) was used to investigate and to characterize the electrical prop... more The electrical field effect (EFE) was used to investigate and to characterize the electrical properties of Bi films. The samples were prepared in a capacitor configuration with Al as the gate electrode, Al2O3 as the dielectric and the thin (∼1300 Å) thermal-evaporation deposited Bi film sample serving as the other electrode. The dependence of EFE on the electrical field (up

We report here the first observation of a pyroelectric effect in a non-polar semiconductor. This ... more We report here the first observation of a pyroelectric effect in a non-polar semiconductor. This effect originates in the temperature dependent electric dipole of the p-n junction. The junction was illuminated by a chopped CO2 laser beam, and periodic and single-pulse pyroelectric signals were observed and measured as a function of temperature, reverse bias voltage and chopper frequency. The measured

Springer Proceedings in Physics, 1988

Physica B: Condensed Matter, 2000

The quantum-size state (QSS) of semimetal Bi "lms has been studied by electric "eld e!ect (EFE), ... more The quantum-size state (QSS) of semimetal Bi "lms has been studied by electric "eld e!ect (EFE), namely, the change of the conductance at the electrical charging of the "lm. The ratio of the electron and hole density of states g /g has been measured by EFE. The thickness dependence of this ratio exhibits a characteristic oscillation pattern, which is an unique label of QSS. This method allows a rather precise determination of the "lm thickness period of the oscillations. The result is in excellent agreement with the value derived from the dispersion law of bulk Bi.

Journal of Low Temperature Physics, 1983

Journal of Physics: Condensed Matter, 2000

The electric field-effect magnetoconductance (EFE-MC) method was applied to study the quantum-siz... more The electric field-effect magnetoconductance (EFE-MC) method was applied to study the quantum-size effect in semimetal Bi films. This method uses a magnetic field to adjust the quantum-size characteristics of a semimetal film - in particular, the ratio of the mobilities of the electrons and holes. We present a theoretical analysis of the EFE-MC method and demonstrate its strength experimentally. The

Japanese Journal of Applied Physics, 2003

Abstract Current-voltage characteristics of micro-Schottky contacts fabricated on Epitaxial later... more Abstract Current-voltage characteristics of micro-Schottky contacts fabricated on Epitaxial lateral overgrowth (ELO) GaN have been measured. The obtained characteristics are classified into two groups; good contacts with small ideality factor (n-value) and poor ...

Proceedings of the National Academy of Sciences of the United States of America, Jan 5, 2016

Liquid droplets, widely encountered in everyday life, have no flat facets. Here we show that wate... more Liquid droplets, widely encountered in everyday life, have no flat facets. Here we show that water-dispersed oil droplets can be reversibly temperature-tuned to icosahedral and other faceted shapes, hitherto unreported for liquid droplets. These shape changes are shown to originate in the interplay between interfacial tension and the elasticity of the droplet's 2-nm-thick interfacial monolayer, which crystallizes at some T = Ts above the oil's melting point, with the droplet's bulk remaining liquid. Strikingly, at still-lower temperatures, this interfacial freezing (IF) effect also causes droplets to deform, split, and grow tails. Our findings provide deep insights into molecular-scale elasticity and allow formation of emulsions of tunable stability for directed self-assembly of complex-shaped particles and other future technologies.

We describe the preparation of high-temperature PbTe diodes. Satisfactory rectification was obser... more We describe the preparation of high-temperature PbTe diodes. Satisfactory rectification was observed up to 180-200 K. Two types of diodes, based on a p-PbTe single crystal, were prepared: (1) by In ion-implantation, and (2) by thermodiffusion of In.