Investigation into the Influence of a Buffer Layer of Nanoporous Silicon on the Atomic and Electronic Structure and Optical Properties of AIIIN/por-Si Heterostructures Grown by Plasma-Activated Molecular-Beam Epitaxy

Semiconductors - The influence of using a buffer sublayer of nanoporous por-Si on the morphological, physical, and structural properties of nanocolumnar InxGa1 –xN structures fabricated by...     

A Spectroscopic Study of Changes in the Secondary Structure of Proteins of Biological Fluids of the Oral Cavity by Synchrotron Infrared Microscopy

Optics and Spectroscopy - On the basis of the data of infrared spectroscopy with synchrotron radiation, the secondary structure of proteins of the dentinal and gingival fluids during the...     

Structural and optical properties of GaAs(100) with a thin surface layer doped with chromium

The aim of this study is to explore the structural and optical properties of single-crystal GaAs(100) doped with Cr atoms by burning them into the substrate at high temperatures. The diffusion of chromium into single-crystal GaAs(100) substrates brings about the formation of a thin (~20–40 μm) GaAs:Cr transition layer. In this case, chromium atoms are incorporated into the gallium-arsenide crystal lattice and occupy the regular atomic sites of the metal sublattice. As the chromium diffusion time is increased, such behavior of the dopant impurity yields changes in the energy structure of GaAs, a decrease in the absorption at free charge carriers, and a lowering of the surface recombination rate. As a result, the photoluminescence signal from the sample is significantly enhanced.     

Local study of fissure caries by Fourier transform infrared microscopy and X‐ray diffraction using synchrotron radiation

Investigations of intact dental enamel as well as carious‐affected human dental enamel were performed using infrared spectromicroscopy and X‐ray diffraction applying synchrotron radiation. Caries of enamel was shown to be characterized by an increase in the number of deformation and valence vibrations for N—C—O, N—H and C=O bonds, a decrease of the crystallinity index, and by the absence of the preferable orientation of hydroxyapatite crystals within the affected enamel. This indicates the presence of destructive processes in the organic matrix of hard tooth tissues.     

The mechanism of electroreduction of nitrate ions on a hybrid electrode nanodispersed copper-MK-40 membrane

Based on a MK-40 sulfocation-exchange membrane, a hybride electrode material containing nanodispersed copper is prepared. The methods of scanning electron microscopy and X-ray diffraction (XRD) analysis reveal the formation of copper agglomerates measuring 250–470 nm and consisting of individual particles of 20–30 nm. The procedure of multistage chemical deposition of copper into the ion-exchange carrier makes it possible to obtain a continuous cluster of metal particles which determines the electron conducting properties of the resulting hybrid material. The electrochemical activity of the nanocomposite electrode is studied in the reaction of nitrate ion electroreduction. Nanodispersed copper deposited into the membrane is shown to intensify the electroreduction of nitrate ions by a factor of 1.5–2 as compared with a compact copper electrode. The electroreduction of nitrate ions on compact copper is shown to involve 6 electrons, whereas the electroreduction on the nanocomposite involves 8 electrons. The electroreduction products of nitrate ions are identified by the IR spectroscopy method.     

Phase formation under the effect of spinodal decomposition in epitaxial alloys of Ga x In1 − x P/GaAs(100) heterostructures

The effect of instability of alloys of Ga _x In_{1 − x} P/GaAs(100) semiconductor epitaxial heterostructures in the composition region x ≈ 0.50 is studied by X-ray diffraction and electron microscopy. The possibility of emergence of modulated relaxation structures on the surface of a Ga _x In_{1 − x} P alloy is shown. This phenomenon is accompanied by the emergence of satellites of main X-ray reflections corresponding to a single-phase structure.     

Features in the kinetics of lateral zone crystallization of semiconductor crystals in a temperature gradient field

Theoretical and experimental investigations of the kinetics of a lateral zone crystallization process in a temperature gradient field are given. Kinetic rules for the method are established which allow one to control the rate of the process and the configuration of the crystallization channel.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 67–71, January, 1996.     

Photoluminescence properties of heavily doped heterostructures based on (Al x Ga1 − x As)1 − y Si y solid solutions

It has been established that the photoluminescence spectra of heavily doped heterostructures based on Al _x Ga_{1 ? x} As)_{1 ? y} Si _y solid solutions exhibit quenching of the main exciton bands of Al _x Ga_{1 ? x} As ternary solid solutions and appearance of other maxima. The quenching of the main exciton bands can be associated both with the DX-center formation and with the change in the character of the band structure of (Al _x Ga_{1 ? x} As)_{1 ? y} Si _y quaternary solid solutions.     

XANES and IR spectroscopy study of the electronic structure and chemical composition of porous silicon on <Emphasis Type="Italic">n</Emphasis>- and <Emphasis Type="Italic">p</Emphasis>-type substrates

The differences in the electronic structure and composition of porous silicon samples obtained under identical conditions of electrochemical etching on the most commonly used n- and p-type substrates with different conductivities are demonstrated by X-ray absorption near-edge spectroscopy (XANES) and Fourier transform IR spectroscopy (FTIR) methods. It is shown that significantly higher oxidation and saturation with hydrogen is observed for the porous layer on n-type substrates.