Reversible superstructural transitions on the GaAs(001) surface under the selective effect of iodine and cesium

The selective interaction of the iodine and cesium atoms with the GaAs(001) surface, which leads to a decrease in the bond energy of the Ga and As surface atoms, respectively, owing to the redistribution of the electron density in the near-surface region under the effect of electronegative and electropositive adsorbates, has been experimentally investigated. This selective interaction makes it possible to remove alternately the Ga and As monolayers in the iodine and cesium adsorption followed by heating at T ≤ 450°C and, thus, to implement reversible low-temperature transitions between the Ga-and As-stabilized superstructures, as well as the atomic layer etching of the semiconductor with the physically ultimate monolayer accuracy.     

Diphilic carbosilane dendrimers with different densities of the hydrophilic layer

A universal method for the synthesis of hydrophilic dendrimers was considered. The method is based on a combination of carbosilane dendrimers with different molecular organizations and hydrophilizing agents, viz., substituted hydride silanes containing one and three protected hydroxyl groups. The combination of a limited set of the mentioned reagents makes it possible to control the ratio of hydrophilic and hydrophobic moieties of the molecular structure in wide limits. A simple and convenient method for the removal of trimethylsilyl protection of hydroxyl groups in the surface layer of dendrimers was developed.     

Energy distributions of photoelectrons emitted from <Emphasis Type="Italic">p</Emphasis>-GaN(Cs,O) with effective negative electron affinity

Energy distributions of photoelectrons emitted into vacuum from the valence band and the localized states in the energy gap of p-GaN(Cs, O) with effective negative electron affinity were studied. It is shown that the photothermal electron excitation from the localized states lying below the Fermi level in the energy gap of p-GaN(Cs, O) is the dominant photoemission mechanism at the low-energy photoemission threshold.     

Optical properties of azo-based poly(azomethine)s with aromatic fluorinated fragments,ether linkages and aliphatic units in the backbone

Abstract

The aim of this work is to study the optical properties of the core-fluorinated azo-containing polyazomethines with 1,4-tetrafluorobenzene or 4,4′-octafluorobiphenylene dioxyphenylene units and aliphatic fragments in the chain. Due to the reorganization process at the nanometer-scale under UV/Vis irradiation, azo-containing polymers (APs) have attracted much attention as materials for biology, optoelectronics, nano-manipulation field, etc. Moreover, the introduction of azomethine group into these polymers enhances not only their optical properties but also expands their practical application. APs polymers have the useful combination of chemical and physical properties such as liquid crystalline states, high nonlinearity and an ability to form metal complexes. It was shown that the optical properties of such polymers could be improved by the inclusion of fluorine. Fluorinated polymers demonstrate high thermal stability and have low dielectric constant and dielectric losses. It should be noted that the presence of flexible moieties in a polymer backbone allows regulating the different properties (solubility, thermostability, optical and liquid crystalline properties) of the final materials.     

Effect of Ionosphere and Inhomogeneity of the Earth Structure on the Polarization Characteristics of Magnetic Field at Frequencies of 0.2–200 Hz in the Near-Field Zone of a Horizontal Grounded Antenna

Technical Physics - Polarization characteristics of the field of an on-Earth emitter located at the Kola Peninsula are experimentally measured at a distance that is no greater than the height of an...     

Evolution of Surface Morphology of Anthracene Single Crystals Under Annealing

Russian Physics Journal - In this work, the effect of formation of macrosteps under dissolution of the anthracene single crystal surface is shown for the first time. Under standard conditions (room...     

Electronic Structure of Magnetic Topological Insulators Mn(Bi1 – xSbx)2Te4 with Various Concentration of Sb Atoms

JETP Letters - Intrinsic magnetic topological insulator MnBi2Te4 provides a promising platform to implement the quantum anomalous Hall effect at increased temperatures and other unique topological...     

Thermodynamic analysis of the decomposition of a supersaturated solid solution of the Fe-Cu system

The structure of Fe-5.5% Cu alloy is studied after eutectoid reaction and aging of the martensite. The thermodynamic analysis of decomposition of the supersaturated solid solution with copper release is peformed for different types of crystal lattice. The free energy of solid solutions and phase separation diagrams of the BCC and FCC phases of copper is calculated. Barriers for the nucleation of copper particles with BCC and FCC lattices are evaluated. The factors that favor the appearance of intermediate structural forms of copper preceding the formation of stable FCC phase are discussed.     

Structure of porphyrin-fullerene dyad monolayer on the water surface and solid substrate

Monolayers of porphyrin-fullerene dyad TBD6a were formed on the surface of a water subphase and then transported on a solid substrate by the Langmuir-Schaefer method. A simulation was performed for the structure of a single molecule and for a molecular monolayer, according to the area per molecule in the monolayer formed, which was calculated based on an analysis of the π-A isotherm. A unit cell was chosen for the proposed molecular packing (a = 1.54 nm, b = 1.50 nm, c = 1.75 nm, α = 80.0°, β = 90.0°, and γ = 90.0°), and the atomic coordinates were calculated. A comparison of the interplanar spacings and diffraction peak intensities in the experimental and calculated (for the unit cell proposed) diffraction patterns indicates that a platelike texture is formed in the monolayer and that the crystal structure of the domains corresponds to the model chosen.     

Kinetics of austenite decomposition upon cooling of low-alloy pipe steel from the intercritical temperature range

High-rate dilatometry is used to study the kinetics of decomposition of undercooled austenite of low-alloy pipe steel 13KhFA obtained upon heating into the single-phase γ field and the intercritical temperature range. The complex effect of the austenitizing in the intercritical temperature range on the decomposition of the undercooled austenite is revealed (the initial temperature of decomposition falls while the temperature of decomposition termination rises).