M. Yu. Presniakov

Erratum to: “Structural and electrical properties of InAlAs/InGaAs/InAlAs HEMT heterostructures on InP substrates with InAs inserts in quantum well”

A complex study of the influence of nanoscale InAs inserts with thicknesses from 1.7 to 3.0 nm introduced into In0.53Ga0.47As quantum wells (QWs) on the structural and electrical properties of In0.52Al0.48As/In0.53Ga0.47As/In0.52Al0.48As heterostructures with one-sided δ-Si-doping has been performed. The structural quality of a combined QW was investigated by transmission electron microscopy. A correlation between the electron mobility in QW with the thickness of InAs insert and the technology of its fabrication is established. Specific features of the InP(substrate)/InAlAs(buffer) interface are investigated by transmission electron microscopy and photoluminescence spectroscopy. A relationship between the energy positions of the peak in the photoluminescence spectra in the range of photon energies 1.24 eV < ħω < 1.38 eV, which is due to the electronic transitions at the InP/InAlAs interface, and the structural features revealed in the interface region is established. It is found that an additional QW is unintentionally formed at the InP/InAlAs interface; the parameters of this QW depend on the heterostructure growth technology.

High temperature magnetism and microstructure of ferromagnetic alloy Si1−x Mn x

The results of a detailed study of magnetic properties and of the microstructure of SiMn films with a small deviation from stoichiometry are presented. The aim was to reveal the origin of the high temperature ferromagnetic ordering in such compounds. Unlike SiMn single crystals with the Curie temperature ~30 K, considered Si1-x Mn x compounds with x  =  0.5  +Δx and Δx in the range of 0.01-0.02 demonstrate a ferromagnetic state above room temperature. Such a ferromagnetic state can be explained by the existence of highly defective B20 SiMn nanocrystallites. These defects are Si vacancies, which are suggested to possess magnetic moments. The nanocrystallites interact with each other through paramagnons (magnetic fluctuations) inside a weakly magnetic manganese silicide matrix giving rise to a long range ferromagnetic percolation cluster. The studied structures with a higher value of Δx  ≈  0.05 contained three different magnetic phases: (a)-the low temperature ferromagnetic phase related to SiMn; (b)-the above mentioned high temperature phase with Curie temperature in the range of 200-300 K depending on the growth history and

Growth of AlGaN under the conditions of significant gallium evaporation: Phase separation and enhanced lateral growth

The growth kinetics of AlGaN in NH3 MBE under significant Ga desorption was studied. It was found that the addition of gallium stimulates 2D growth and provides better morphology of films compared to pure AlN. The effect was experimentally observed at up to 98% desorption of the impinging gallium. We found that under the conditions of significant thermal desorption, larger amounts of gallium were retained at lateral boundaries of 3D surface features than at flat terraces because of the higher binding energy of Ga atoms at specific surface defects. The selective accumulation of gallium resulted in an increase in the lateral growth component through the formation of the Ga-enriched AlGaN phase at boundaries of 3D surface features. We studied the temperature dependence of AlGaN growth rate and developed a kinetic model analytically describing this dependence. As the model was in good agreement with the experimental data, we used it to estimate the increase in the binding energy of Ga atoms at surface defects...

High-resolution X-ray diffractometry and transmission electron microscopy as applied to the structural study of InAlAs/InGaAs/InAlAs multilayer transistor nanoheterostructures

InAlAs/InGaAs/InAlAs nanoheterostructures with different structures of metamorphic buffer layer and quantum well, which were grown by means of molecular-beam epitaxy on GaAs and InP substrates, are investigated. The laboratory technology of the growth of the given nanoheterostructures with predicted properties is perfected. The potential of an approach based on the comprehensive analysis of experimental data obtained via different techniques, namely, X-ray diffractometry, electron diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, and atomic-force microscopy is studied. The metamorphic buffer layer design is improved on the basis of the results of the performed investigations. A method whereby balanced-mismatched superlattices are introduced directly inside the metamorphic buffer layer is proposed. It is established that the technological parameters of the growth of nanoheterostructures affect their structural perfection and electrophysical properties.

Structure of One-Dimensional Rubidium and Silver Iodide Crystals in the Channels of Single-Walled Carbon Nanotubes

The structures of one-dimensional (1D) RbI, AgI, and RbAg4I5 crystals inside single-walled carbon nanotube (SWCNT) channels of 1D crystal@SWCNT nanocomposites formed by the capillary technique have been studied by high-resolution (scanning) transmission electron microscopy and computer modeling. 1D RbI crystals form a cubic lattice in a limited space, while 1D AgI crystals form a hexagonal lattice, as in their ternary compounds. The 1D RbAg4I5 structure differs from known bulk analogs and can be described by a distorted cubic lattice formed in two different directions.

On the Growth of High-Temperature Epitaxial AlN (AlGaN) Layers on Sapphire Substrates by Ammonia Molecular Beam Epitaxy

The growth of high-temperature AlN and AlGaN layers on (0001) sapphire substrates by ammonia based molecular-beam epitaxy is studied. Factors affecting the formation of inverted domains in high-temperature AlN films are examined. The density of inverted domains is found to correlate with the density of nucleation islands during the initial stages of growth. The denser coverage of a surface by nucleation islands suppresses the formation of inverted domains. It is possible to increase the density of surface coating at the nucleation growth stage by increasing the degree of substrate nitriding, reducing the deposition temperature, and using intense ammonia fluxes during deposition of the initial layers. The kinetic model in the mean field approximation is developed to explain the observed effects of growth parameters on the density of nucleation islands. The growth features of AlN and its structure are taken into account. The obtained results are used to grow AlN/AlGaN layers with improved structural quality. The grown films have a root-mean-square surface roughness of 2 Å and 120 arc s FWHM of X-ray diffraction peaks for the AlN 0002 reflection. The density of inverted domains is decreased to below 105 cm-2. Improvement in the quality of the AlN films is achieved by using two-step growth and by the application of gallium as a surfactant.

Crystal structure of stacking faults in InGaAs/InAlAs/InAs heterostructures

Stacking faults and dislocations in InGaAs/InAlAs/InAs heterostructures have been studied by electron microscopy. The use of different techniques of transmission electron microscopy (primarily, highresolution dark-field scanning transmission electron microscopy) has made it possible to determine the defect structure at the atomic level.

Electron microscopy study of the microstructure of Ni–W substrate surface

The surface microstructure of Ni–W alloy tapes, which are used as substrates to form films of high-temperature superconductors and photovoltaic devices, has been studied. Several samples of a Ni95W5 tape (Evico) annealed under different conditions were analyzed using scanning electron microscopy, energy-dispersive X-ray microanalysis, electron diffraction, and electron energy-loss spectroscopy. NiWO4 precipitates are found on the surface of annealed samples. The growth of precipitates at a temperature of 950°С is accompanied by the formation of pores on the surface or under an oxide film. Depressions with a wedge-shaped profile are found at the grain boundaries. Annealing in a reducing atmosphere using a specially prepared chamber allows one to form a surface free of nickel tungstate precipitates.