Исследование сильно легированных эпитаксиальных пленок n-3C-SiC, выращенных методом сублимации на основе полуизолирующих подложек 6H-SiC

Heavily doped 3C-SiC films based on semi-insulating 6H-SiC substrates were obtained by sublimation epitaxy. The structural perfection of the obtained samples was monitored by X-ray diffractometry. The measurements of the photoluminescence and Hall effect spectra have confirmed the rather high perfection of the obtained epitaxial layers.

Гетероструктура квантово-каскадного детектора частотного диапазона 2.5 ТГц

The design of the heterostructure of a 2.5 THz range quantum-cascade detector is proposed and heterostructure is grown by molecular-beam epitaxy technique. To optimize the thicknesses of the layers of the heterostructure cascades, a numerical method for iterative solution of the Schrodinger ¨ −Poisson equation in the k · p formalism was used. The grown heterostructure of the quantum-cascade detector showed a high structural perfection, confirmed by the small values of the average FWHM of the high-order satellite peaks on the X-ray diffraction rocking curves, which were (8.3 ± 0.5)′′. Analysis of dark-field images obtained by transmission electron microscopy showed that the total thickness of the layers in the cascade is (137.3 ± 6.9) nm, which corresponds to the calculated thickness of the layers in the cascade of the heterostructure of the quantum-cascade detector.

Laue X-ray diffraction studies of the structural perfection of Al-doped thermomigration channels in silicon

Si(111) wafers patterned with an array of vertical 100 µm-wide Al-doped (1 × 1019 cm−3) p-channels extending through the whole wafer were studied by X-ray Laue diffraction techniques. The X-ray techniques included projection topography, and measurement of rocking curves and cross sections in the vicinity of the 02\overline 2 reciprocal space node in the double- and triple-crystal geometry, respectively. The channels are uniform along the depth of the wafer, and their structural perfection is comparable to that of the silicon matrix between the channels. Simulation of the rocking curves was performed using the methods of the dynamical theory of X-ray diffraction. The rocking-curve calculations both taking into account and neglecting the effect of the instrumental function were carried out using the Takagi–Taupin equations. The calculated angular dependences of intensities of both diffracted and transmitted X-rays correspond well to the experimentally obtained rocking curves and demonstrate their high sensitivity to the structural distortions in the channel. An unambiguous reconstruction of strain and structural distortions in the Si(Al) channel using the Laue diffraction data requires further development of the theoretical model.

The process of preparation of tellurium epitaxial films and layers with high structural perfection during vapor-deposition process in the pure hydrogen environment

The work is devoted to studying a new methodology for epitaxial films preparation on the mi-ca (muscovite) plates and based on carrying out the tellurium vapor-deposition process in the pure hydrogen environment. The formation of Н2Te molecules during reaction of H2 with sol-id Te in the hot zone, diffusion of Н2Te towards the cold surface with efficient thermalization due to high thermal conductivity of H2, Н2Te dissociative adsorption on the growth surface followed by H2 desorption and atomic Te accumulation are considered as key steps of crystal-line epitaxial films formation. Atomic Te assists the appearance and growth of directional liquid nucleuses at cold plate temperatures near Te melting point (about 450C). During coa-lescence of these liquid nucleuses the gradual formation of a liquid film is observed with a mosaic of voids of various size. After continuous liquid sheet formation, auto-epitaxial film growth begins also taking place according to vapor-liquid-crystal process described. The structural perfection of films formed is closed to three-dimensional monocrystalline samples. As a result, Te films with such characteristics may be put to use in various branches of micro-, opto-, acoustoelectronics.

PASSIVE SAFETY OF MOTOR TRANSPORT DEPENDING ON THE

The interrelation of thermal modes of brake units of transport vehicles on their reliability and durability depending on operational factors of transport is considered. It is assumed that all the kinetic energy of rotating and translationally moving masses in the brake nodes is converted into thermal energy. In this regard, a criterion is used that characterizes the thermal energy released in the brakes and the operational criterion of transport vehicles. Comparison of these criteria makes it possible to evaluate the performance and durability of brake components, as well as to outline ways of their structural perfection depending on heat dissipation.

Формирование и структура термомиграционных кремниевых каналов, легированных Ga

We have produced through-wafer vertical Si (Ga) p-channels by thermal migration of local gallium zones in c-Si (111) wafers. To achieve this, a method for the formation of local zone was proposed and implemented, which consists in filling linear grooves etched in a silicon wafer with fine-dispersed Ga powder. The grooves were 100 um wide and 30-50um deep. It was shown that a high yield of suitable zones occurs when the grain size of the powder is 5 um and the temperature is 290 K. The obtained Si (Ga) thermomigration p-channels were studied by X-ray methods of double-crystal rocking curves and projection topography. The characterization of structural perfection of Ga p-channels was performed by their comparison with the structural features of the Si (Al) thermomigration channels. Typical structural defects at the boundaries of both thermomigration channels were shown to be dislocation half-loops fixed by their ends at those boundaries. The concentrations of Al and Ga in the obtained channels were estimated as С(Al) ~ 1E19 и С(Ga) ~ 1.9 E19cm-3, the deformation e~(2–5)E-5 and tilt ~ 15–30 ʹʹ of crystal planes near the channel-matrix interface of the plate were determined.

Образование дендритной структуры в кристаллах NiFeGaCo при выращивании способом Степанова

The process of growing crystals of the Ni-Fe-Ga-Co alloy by the Stepanov method has been developed. It was found that the structural perfection is disturbed by the formation of dendrites, which are distributed inhomogeneously both along the length and in the cross sections of the crystals. The blocking effect on the dendrites of crystals of the martensite phase, which appears when the samples are cooled to the temperature of the transition of the crystal to the martensite state, is found. The elemental composition of dendritic formations was studied and it was shown that the iron content in the dendrite is approximately 30% higher, and the gallium content is 40% lower than in the matrix. Based on the modeling of heat transfer processes in the real growth zone, taking into account the experiments performed, recommendations were obtained for suppressing the formation of dendrites

Multilayer Diffraction Reveals That Colloidal Superlattices Approach the Structural Perfection of Single Crystals

Colloidal superlattices are fascinating materials made of ordered nanocrystals, yet they are rarely called “atomically precise.” That is unsurprising, given how challenging it is to quantify the degree of structural order in these materials. However, once that order crosses a certain threshold, constructive interference of X-rays diffracted by the nanocrystals dominates the diffraction pattern, offering a wealth of structural information. By treating nanocrystals as scattering sources forming a self-probing interferometer, we developed a multilayer diffraction method that enabled the accurate determination of nanocrystal size, interparticle spacing, and their fluctuations for samples of self-assembled CsPbBr₃ and PbS nanomaterials. The average nanocrystal displacement of 0.32-1.4 Å in the studied superlattices provides a figure of merit for their structural perfection and approaches the atomic displacement parameters found in traditional crystals. The method requires a laboratory-grade diffractometer and an open-source fitting algorithm for data analysis, providing a competitive alternative to resource-intensive synchrotron experiments.