Use of Wear-Resistant Materials in the Kazakhstani Metallurgical Industry

Metallurgist - We provide an overview of requirements for wear-resistant materials in the Kazakhstani ore mining and smelting industry, and describe the basic variety of metallurgical parts and...     

Quantum Hall effect in a single-mode wire

The quantum Hall effect in a single-mode wire is studied for the first time. It is established that a well-expressed quantum Hall resistance for filling factors i=1 and 2 is observed in magnetic fields in which the magnetic length becomes less than the width of the wire. Breakdown of proportionality with respect to the magnetic field in the arrangement of the Hall quantization plateau and the dissipative conductivity minima is observed. Fiz. Tekh. Poluprovodn. 33, 1369–1371 (November 1999)     

Photon-Assisted Electron Transmission through a Quantum Point Contact

The theory of coherent photon-assisted electron transmission through a one-dimensional smooth barrier is successfully used to model the results of measuring the terahertz photoconductivity of a tunneling point contact in a two-dimensional electron gas. For this barrier in a deeper tunneling mode, photon steps in the curve of the transmission coefficient versus initial electron energy were found. Their position is determined by the terahertz photon energy.     

Synthesis of Hydroxylamine Sulfate via NO Hydrogenation over Pt/Graphite Catalysts,Part 2: Effect of the Reaction Conditions and the Physicochemical State of a Catalyst on the Yield of Products

The selectivity toward products is studied for the industrially important process of NO hydrogenation in a H2SO4 solution as a function of process parameters: the hourly space velocity of the NO + H2 gas mixture through the reactor, the speed of stirring and the concentration of the Pt catalyst/graphite suspension, and the temperature. It is found that the first or zero order with respect to the catalyst can be observed for this process in the regime of external diffusion limitation for the gas reagents, depending on the concentration of the catalyst in the suspension, and the selectivity toward solid products (hydroxylamine sulfate (HAS) and ammonium sulfate) is greatest in the region of transition. It is shown that the selectivity towards HAS can be improved by functionalizing graphite surface with nitrogen-containing groups that modify the adsorption and catalytic properties of supported platinum nanoparticles. Some views are presented on specific features of the functioning of platinum catalysts in concentrated suspensions with a limited supply of the reaction gases.     

Wave Structure of Liquid Films during the Transition to the Turbulent Flow Mode

Technical Physics Letters - The results of an experimental study of the waves on the surface of a vertically falling liquid film in the range of the Reynolds numbers of film flow 80 < Re...     

Growing HgTe/Cd<Subscript>0.735</Subscript>Hg<Subscript>0.265</Subscript>Te quantum wells by molecular beam epitaxy

HgTe/Cd_0.735Hg_0.265Te nanostructures with HgTe quantum wells 16.2 and 21.0 nm thick are grown without additional doping on (013)CdTe/ZnTe/GaAs substrates by the method of molecular beam epitaxy. The compositions and thicknesses of the wide-gap layer and quantum well in the course of growth are performed by means of ellipsometry. The accuracy is Δx ? ±0.002 mole fractions of cadmium telluride in determining the composition and Δd ? 0.5 nm in determining the thickness of the wide-gap layer and quantum well. The central fragments of the wide-gap layers ≈ 10 nm thick are additionally doped by indium for a ～ 10¹⁵ cm^?3 volume concentration of charge carriers to be reached. Galvanomagnetic research in a wide range of magnetic field intensities at liquid helium temperatures reveals dimensional quantization levels and the presence of a two-dimensional electron gas in grown nanostructures. High mobility of the two-dimensional electron gas μ _e is obtained: 2 · 10⁵ and 5 · 10⁵ cm²/V · s for electron densities N _s equal to 1.5 · 10¹¹ and 3.5 · 10¹¹ cm^?2, respectively.     

Effect of the reverse bias between channel and substrate on the effective mobility of electrons in a Ge i.g.f.e.t.

An analysis of the behaviour of the electron effective mobility under reverse bias between the channel and substrate in a germanium i.g.f.e.t. is presented. It is shown that the experimentally observed decrease in the effective mobility of the electrons in the channel is mainly caused by the decrease in the electron drift mobility in the channel, rather than by surface-state capture.     

Introscopy in nano- and mesoscopic physics: Single electronics and quantum ballistics

A method is presented to be used in a computational experiment aimed at studying the internal structure of nano- and mesoscopic objects, i.e., conducting subsystems and quantum phenomena in solid submicron objects, which demonstrate an individual behavior of low-temperature resistance.     

Rivulet dynamics at isothermal film flow

Averaged fields of thickness of an isothermal vertically flowing liquid film, obtained by the laserinduced fluorescence method, have been analyzed. The chosen minimum averaging time interval, at which the wave motion is completely averaged, allows one to observe rivulet dynamics in a transverse direction. It is found that short-lived rivulets, which are chains of no less than five to eight waves with similar transverse coordinates, are dominant structures on the film surface at Reynolds number Re > 50.     

Properties of 2D electron gas in AlGaAs/GaAs heterojunctions with thin AlGaAs layers

Transport properties of a 2D electron gas located at a short distance from the surface (15–32.5 nm) in an AlGaAs/GaAs heterojunction were studied. A pronounced effect of the surface on the behavior of the conductivity of the 2D electron gas, as well as metallic gate screening of the scattering of two dimensional electrons by charged centers, were observed.