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The structures comprising three epitaxial InP layers—buffer (n[sup ++]), active (n), and contact (n[sup +])— were grown by liquid phase epitaxy on porous and compact (control) InP(100) substrates. High quality of the active n-InP layer obtained on a porous substrate (in comparison to the control samples) is confirmed by the values of the halfwidths of the (311) X-ray diffraction reflections (54″ versus 76″), dislocation concentration (5 × 10² - 5 × 10³ cm[sup -2] versus 5 × 10[sup 4] - 5 × 10[sup 5] cm[sup -2]), and electron mobility (4000 cm²/V s versus 30003500 cm²/V s). Using these homoepitaxial InP structures, Au-Ti Schottky diodes with a working mesastructure area of ∼1.8 × 10[sup -6] cm² were prepared. It was found that diodes based on the porous substrates are characterized by significantly smaller leak currents and higher breakdown voltages as compared to those of the control diodes: 1 nA, 27 V versus 200 nA, 15 V. [ABSTRACT FROM AUTHOR]

The effect of hot-filament chemical vapor deposition conditions on the phase composition of diamond films grown on a silicon substrate was studied. The growth conditions providing the highest content of diamond phase at a growth rate of about 1 µm/h were ascertained. [ABSTRACT FROM AUTHOR]

The paper reports on a study of the effect of annealing in hydrogen on the structural phase transition in clusters of ultradisperse diamond (UDD) obtained by the detonation method. The samples studied were of two types, namely, prepared by the “dry” and “wet” techniques, which differ in the cooling rate of the detonation products and, accordingly, in the structure of the diamond nanocluster shell. It is shown that, irrespective of the type of synthesis, the relative content of the diamond (sp3) phase increases within the anneal temperature range of 450 to 750°C, the increase being more pronounced in the samples prepared by “dry” synthesis. A model accounting for the observed structural transformation processes is discussed. A hypothesis of the possibility of compacting UDD clusters into bulk single crystals is put forward. © 2000 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

A model describing the structure of diamond nanoclusters produced by explosive shocks is proposed. The model is based on experimental data obtained from x-ray diffraction and smallangle x-ray scattering. This model considers the diamond nanocluster as a crystalline diamond core coated by a carbon shell having a fractal structure. The shell structure depends both on the cooling kinetics of the detonation products and on the method used to extract from them the diamond fraction. [ABSTRACT FROM AUTHOR]

Lasing is discovered in the direction perpendicular to the surface in quantum-size InGaN/GaN multilayer heterostructures grown by vapor-phase epitaxy. At high excitation densities one of the modes in the luminescence spectrum, which is modulated by modes of the Fabry-Pérot cavity formed by the GaN/air and GaN/sapphire-substrate interfaces, is sharply amplified and begins to dominate the spectrum. The dependence of the luminescence intensity on pump density has a clearly expressed threshold character. The threshold excitation density in the vertical direction is 5-6 times greater than the stimulated-emission threshold for observation from an end surface of the structure. The gain coefficient in the active region at the threshold for surface-emitting lasing is estimated as 2 × 10[sup 5] cm[sup -1]. The interaction between the cavity modes and the gain spectrum is detected in the form of displacement (by up to 2.6 nm) of modes on the short-wavelength edge of the luminescence spectrum toward higher photon energies. The characteristic temperature (T[sub 0]) measured in the range from 16 to 120 K is 480 K. At higher temperatures T[sub 0] = 70 K. [ABSTRACT FROM AUTHOR]

The influence of C[sub 60] additive in industrial oil on the structure of the friction surface of copper foil in a steel-copper sliding friction pair is investigated by wide-angle x-ray diffraction, scanning electron microscopy, and hardness testing. The presence of C[sub 60] in the lubricant leads to the formation of a thin film (of thickness < 1000 Å) on the friction surface of the copper, where it protects the surface layers of the latter against major structural changes and helps to improve the tribological characteristics. [ABSTRACT FROM AUTHOR]

Ultradisperse-diamond clusters are shown to be fractal objects, and the character of variation of the fractal dimension in the course of the diamond-graphite phase transition under annealing in an inert atmosphere is studied. [ABSTRACT FROM AUTHOR]

A systematic study of the diamond-graphite structural phase transition in ultradisperse-diamond clusters obtained by the detonation technique is reported. Samples of two types, differing in the kinetics of detonation-product cooling, were investigated. The phase transition was achieved under heating in an inert atmosphere in the temperature range 720-1400 K. The transition was identified by Raman scattering and x-ray diffraction data. Raman and x-ray characterization showed the ultradisperse diamond, irrespective of the cooling rate used, to be cluster material possessing diamond structure with a characteristic nanocrystal size of 43 Å. The diamondgraphite phase transition in ultradisperse diamond is shown to start from the cluster surface inwards at T[sub pt] ≈ 1200 K, i.e. at substantially lower temperatures than is the case with bulk diamond single crystals. [ABSTRACT FROM AUTHOR]

The films of amorphous hydrogenated carbon containing cobalt nanoparticles are studied by small-angle X-ray scattering (SAXS). The SAXS pattern structure reveals the presence of two types of scattering centers, one of which represents cobalt particles. It is suggested that the second type of scattering centers can represent the groups of nanoparticles possessing a localized electron wavefunction and forming a cluster electron state. [ABSTRACT FROM AUTHOR]

Multi-technique structural and electro-physical investigations of VO[sub 2] films on SiO[sub 2]/Si substrates are carried out to study the microscopic nature of fluctuator defects — sources of low-frequency flicker noise. It is established that the noise intensity is determined by the magnitude of the microstress fluctuations 〈ε〉={〈(δc/c)[sup 2]〉}, where c is the lattice parameter along the c-axis parallel to [011] direction in the blocks of which the film is formed. The dimensions of the blocks were determined in the direction of the c-axis (t[sub c]∼1000 Å). The suggestion is put forward that the samples contain two types of fluctuator defects: 1) V atoms jumping between the two nearest interstitial sites and 2) V atoms jumping between these interstitial sites near lattice defects. [ABSTRACT FROM AUTHOR]