25 research outputs found
HRXRD study of the effect of a nanoporous silicon layer on the epitaxial growth quality of GaN layer on the templates of SiC/por-Si/c-Si
Using High Resolution X-ray Diffraction (HRXRD) diagnostic techniques the influence of the transition layer of nanoporous silicon on the practical implementation and certain features of the epitaxial growth of GaN layers with the use of molecular beam epitaxy were investigated by means of plasma activation of nitrogen (MBE PA) on the templates of SiC/por-Si/c-Si. For the first time it was shown that introducing of the transition layer of nanoporous silicon in the template of SiC/por-Si/c-Si where the layer of 3C-SiC was obtained by substitution of the atoms had a number of indisputable advantages as compared with conventional silicon substrates. Particularly, such an approach, in fact, enabled a 90% reduction in the level of stresses in the crystalline lattice of the epitaxial GaN layer which was synthesized on SiC surface of SiC/por-Si/c-Si template by means of MBE PA technique as well as to decrease some of vertical dislocations within GaN layer. © 2020 The AuthorsRussian Science Foundation, RSFThe work was executed under support of the grant of Russian Science Foundation 19-72-10007 . Access to KNMF equipment was obtained under the grant of the President of the Russian Federation MD-42.2019.2
Рентгенофункциональная диагностика легочных осложнений у больных хроническим лимфолейкозом
Results of complex radiological examination of 102 patients with chronic lymphocytic leukemia are presented. Traditional (X-ray examination, electroroentgenotomography, computed tomography) and original (zone roentgenodensitometry using computed densitometer "Densigraph-2" of own construction, zone inspiratory and expiratory CT densitometry and planimetry, quantitative evaluation of emphysematous lung tissue using CT) methods were applied in all the patients. Results of radiological and functional evaluation of regional lung ventilation in the patients are analyzed. Diagnostic algorithms are shown allowing not only effective detection the thoracic complications in chronic lymphocytic leukemia patients but also determination their risk factors.В работе представлены результаты комплексного лучевого обследования 102 больных хроническим лимфолейкозом (ХЛ). Всем больным были выполнены как традиционные методы лучевой диагностики (рентгенография, электрорентгенотомография, компьютерная томография), так и оригинальные (зональная рентгеноденситометрия с помощью компьютеризированного денситометра "Денсиграф-2", собственной конструкции; зональная инспираторно-экспираторная КТ-денситометрия и планиметрия; количественное определение эмфизематозно трансформированной легочной ткани при компьютерной томографии). Проанализированы результаты рентгенофункционального исследования регионарной вентиляции легких у больных ХЛ. Представлены диагностические алгоритмы, позволяющие не только эффективно диагностировать торакальные осложнения у больных лимфолейкозом, но и определять факторы риска развития этих осложнений
Investigations of Nanoscale Columnar AlxGa1-xN/AlN Heterostructures Grown on Silicon Substrates with Different Modifications of the Surface
The growth of nanoscale columnar AlxGa1-xN/AlN heterostructures on the surface of silicon substrates using plasma-activated nitrogen molecular-beam epitaxy was investigated in this work. Silicon substrates include atomic-smooth cSi substrate, Si substrate with a transition layer of porous silicon porSi/cSi and a hybrid substrate involving a silicon carbide layer grown with matched substitution of the atoms on the surface of porous silicon SiC/porSi/cSi. A complex analysis performed using a set of structural and spectroscopic techniques demonstrated that the epitaxial growth of the nuclear AlN layer on all types of the substrates in a N-enriched environment resulted in the formation of AlxGa1-xN/AlN heterostructures with a Ga-polar surface, which was realized only on the SiC/porSi/cSi substrate. The layer of AlxGa1-xN on cSi and porSi/cSi substrates was in the state of disordered alloy with an excess of gallium atom content. It was shown that a great difference in the lattice parameters of a substrate–film pair resulted not only in the appearance of a number of various defects but also in a considerable effect on the chemical process of the formation of the alloys, in our case, the AlxGa1-xN alloy. It was shown that nanoscale columns of AlxGa1-xN formed on SiC/porSi/cSi substrate were inclined relative to the c-axis, which was connected with the features of the formation of a SiC layer by the matched substitution of the atoms on the porous Si substrate, resulting in the formation of the inclined (111) SiC facets at the boundary of the (111) Si surface and pores in Si. Optical studies of the grown samples demonstrated that the optical band-to-band transition for the AlxGa1-xN alloy with Eg = 3.99 eVB was observed only for the heterostructure grown on the SiC/porSi/cSi substrate. A qualitative model is proposed to explain the difference in the formation of AlxGa1-xN layers on the substrates of cSi, porSi/cSi and SiC/porSi/cSi. The results obtained in our work demonstrate the availability of using SiC/porSi/cSi substrates for the integration of silicon technology and that used for the synthesis of nanoscale columnar AlxGa1-xN heterostructures using plasma-activated molecular-beam epitaxy with a nitrogen source. © 2023 by the authors.Russian Science Foundation, RSF: 19-72-10007; Ministry of Science and Higher Education of the Russian Federation: 075-15-2021-1351, FSRM-2023-0006, FZGU-2023-0006This work was carried out under the financial support of the Russian Science Foundation, grant 19-72-10007. Adjustment of the formation of the hybrid substrate was performed under the support of the Ministry of Science and Higher Education of Russia (grant No. FZGU-2023-0006). Synthesis of the samples using the MBE PA technique, as well as the study of heterostructures polarity were completed under the support of the Ministry of Science and Higher Education of Russia No. FSRM-2023-0006. As for access to scientific equipment and methodology of measurements and analysis, this study was carried out under the support of the Ministry of Science and Higher Education of Russia, contract No. 075-15-2021-1351
НАНОЧАСТИЦЫ ОКСИДОВ МЕТАЛЛОВ, ПОЛУЧЕННЫЕ НА ПОДЛОЖКАХ ПОРИСТОГО КРЕМНИЯ
Tin, iron and nickel oxides were prepared in micro porous silicon from sols. The morphology of the samples was studied using atomic force microscopy. The сross−sections of porous silicon were investigated using scanning electron microscopy. The electrical properties were investigated by impedance spectroscopy in a changing environment and temperature of gas detection reagents. The dependencies of real and imaginary components of the complex impedance were constructed in the semi−logarithmic coordinates. The method of complex plane was used for processing the experimental impedance data. Hodographs of impedance were analyzed using programs writteng in the LabVIEW environment. The experimental impedance spectroscopy data were interpreted in terms of «equivalent electrical circuit». Сonstant phase element was used to describe the resistive− capacitive properties of nanocomposite materials in the equivalent electrical circuit. The characteristic charge accumulation time in air and in the presence of reducing gases was calculated. The sensitivity to reducing gases for the real and imaginary components of the complex impedance was calculated using two methods at 300 °C in the frequency range from 1 Hz to 500 kHz. The sensor characteristics of metal oxide films grown on single−crystal substrates, porous silicon and glass substrates were compared. Из золей в микрообъемах пористого кремния получены оксиды олова, железа и никеля. Морфология образцов изучена с помощью атомно−силовой микроскопии. Поперечные срезы пористого кремния исследованы с помощью метода сканирующей электронной микроскопии. Электрические свойства изучены методом спектроскопии импеданса в условиях изменения газовой среды и температуры детектирования газов−реагентов. В полулогарифмических координатах построены зависимости реальных и мнимых компонент комплексного сопротивления. Для обработки экспериментальных данных импеданса использован метод комплексной плоскости. Годографы импеданса проанализированы с помощью программ, написанных в среде LabVIEW. Экспериментальные данные спектроскопии импеданса интерпретированы в терминах «эквивалентной электрической схемы». Для описания резистивно− емкостных свойств нанокомпозиционных материалов в эквивалентной схеме использован элемент постоянной фазы. Рассчитано характеристическое время накопления заряда в атмосфере воздуха и в присутствии восстанавливающих газов. Значения чувствительности к восстанавливающим газам при температуре детектирования 300 °С в диапазоне частот от 1 Гц до 500 кГц рассчитаны двумя способами по реальной и мнимой компонентам комплексного сопротивления. Сопоставлены сенсорные характеристики металлооксидных пленок, полученных на подложках монокристаллического и пористого кремния, а также на стеклянных подложках.
ВЛИЯНИЕ ОБРАБОТКИ ПОВЕРХНОСТИ ПОРИСТОГО КРЕМНИЯ В РАСТВОРЕ ПОЛИАКРИЛОВОЙ КИСЛОТЫ НА ЕГО ФОТОЛЮМИНЕСЦЕНТНЫЕ СВОЙСТВА
Porous silicon (por-Si) has a unique set of physic−chemical properties of characteristics — well-developed surface and consequently, a high sorption activity. In a dependence of the fabrication technique it is possible to form pores and clusters of nanometer size that makes this material rather prospective for elaborations in optoelectronics and sensors production. However, high surface activity stipulates porous silicon instability in the atmosphere. The work is concerned with the study of the influence of por-Si surface treatment in the aqueous solution of polyacrylic acid on the composition and photoluminescence of this material. It was found that this treatment can either enhance and stabilize PL of the material or change spectral position of PL band and also enhance its total intensity in a dependence of the fabrication technique.Пористый кремний обладает уникальным набором физико-химических характеристик — развитой поверхностью и, как следствие, существенной сорбционной активностью. В зависимости от технологии изготовления в нем можно сформировать поры и кластеры нанометровых размеров, что делает этот материал перспективным для разработок в области оптоэлектроники и сенсорики. Однако высокая активность поверхности обуславливает нестабильность пористого кремния при его контакте с атмосферой. Исследовано влияние обработки поверхности пористого кремния в водном растворе полиакриловой кислоты на состав и фотолюминесценцию материала. Установлено, что такая обработка, в зависимости от технологии получения пористого кремния, может усиливать и стабилизировать фотолюминесценцию этого материала или изменять положение полосы фотолюминесценции и значительно увеличивать ее интегральную интенсивность
Study of semi-polar gallium nitride grown on m-sapphire by chloride vapor-phase epitaxy
In this study, we analyzed the result of the influence of the non-polar plane of a sapphire substrate on the structural, morphological, and optical properties and Raman scattering of the grown epitaxial GaN film.
It was found that selected technological conditions for the performed chloride-hydride epitaxy let us obtain the samples of structurally qualitative semi-polar wurtzite gallium nitride with (11¯22) orientation on m-sapphire. Using a set of structural and spectral methods of analysis the structural, morphological, and optical properties of the films were studied and the value of residual bi-axial stresses was determined. A complex of the obtained results means a high structural and optical quality of the epitaxial gallium nitride film.
Optimization of the applied technological technique in the future can be a promising approach for the growth of the qualitative GaN structures on m-sapphire substrates
Особенности применения сорбционного анализа для исследования различных наноматериалов электроники в зависимости от состава и технологических условий получения
Introduction. At present, sorption methods of analysis, including the thermal desorption of inert gases, are widely adopted to characterize the porous structure parameters of nanomaterials having a wide range of applications. Nitrogen thermal desorption belongs to the group of nondestructive techniques that provide a rapid analysis of the following parameters exhibited by nanomaterials: specific surface area, average particle size, mesopore size distribution, as well as the presence or absence of micropores in the system. In this work, mesoporous silicon and calcium hydroxyapatite powders are selected as the objects of research. Since modern interference optical filters are cumbersome and expensive to use, meso- and nanoporous silicon nanostructures are of interest in the implementation of filters for fiberoptic communication systems. Hydroxyapatite can potentially provide high corrosion resistance while posing no risk of toxicity to the environment. In addition, anticorrosion hydroxyapatite coatings are of decisive importance for the practical application of magnesium alloys used to reduce the weight of vehicles, aircraft, and electronics housings.Aim. To consider the application of the thermal desorption of inert gases, specifically nitrogen thermal desorption, in the study of the porous structure parameters of nanomaterials having various compositions on the example of mesoporous silicon and hydroxyapatite.Materials and methods. In this work, the thermal desorption of inert gases and capillary condensation were applied to study the porous structure parameters of hydroxyapatite and porous silicon powders. In particular, the nitrogen thermal desorption method was implemented using a Sorbi MS instrument equipped with a Sorbi Prep sample preparation station.Results. Recommendations are provided on choosing the mass of the adsorbent material required for the study, the sample preparation conditions, as well as the relative partial pressure range of the gas adsorbate. The selected sample types were found to lack a micropore system in the structure. Finally, the dependence of the specific surface area of hydroxyapatite powders and the parameters of its mesoporous structure on heat treatment conditions was analyzed.Conclusion. The study of nitrogen adsorption and capillary condensation allows the porous structure parameters of hydroxyapatite and porous silicon to be reproduced, which is of great importance for their use in medicine and radio electronics as anticorrosion coatings, as well as for the implementation of optical filters.Введение. В настоящее время сорбционные методы анализа, включая метод тепловой десорбции инертных газов, широко применяются для характеризации параметров пористой структуры наноматериалов широкого спектра функционального назначения. Тепловая десорбция азота относится к группе неразрушающих методик, обеспечивающих экспресс-анализ таких параметров наноматериалов, как удельная поверхность, средний размер частиц, распределение мезопор по размерам, наличие или отсутствие микропор в системе. В данной статье в качестве объектов исследования выбраны порошки мезопористого кремния и гидроксиапатита кальция. Наноструктуры на основе мезо- и нанопористого кремния представляют интерес при реализации фильтров для систем волоконнооптической связи, поскольку современные интерференционные оптические фильтры громоздки в использовании и дороги. Гидроксиапатит потенциально обеспечивает высокую коррозионную стойкость и не токсичен для окружающей среды. Антикоррозионные покрытия на его основе имеют решающее значение для практического применения магниевых сплавов, которые используются для уменьшения массы транспортных средств, самолетов, корпусов электроники.Цель работы. Рассмотрение особенностей применения метода тепловой десорбции инертных газов, в частности азота, для исследования параметров пористой структуры наноматериалов различного состава на примере мезопористого кремния и гидроксиапатита.Материалы и методы. Применение метода тепловой десорбции инертных газов и капиллярной конденсации для исследования параметров пористой структуры порошков гидроксиапатита и пористого кремния. Метод тепловой десорбции азота реализован с помощью прибора Сорби МС, оснащенного станцией пробоподготовки Сорби Преп.Результаты. Предложены рекомендации по выбору массы материала-адсорбента, требуемой для исследования, выбору условий пробоподготовки и диапазона изменения относительного парциального давления газаадсорбата. Установлено, что выбранные типы образцов характеризуются отсутствием системы микропор в структуре. Проанализирована зависимость удельной поверхности порошков гидроксиапатита и параметров его мезопористой структуры от условий термообработки.Заключение. Исследование процессов адсорбции и капиллярной конденсации азота позволяет воспроизводить параметры пористой структуры гидроксиапатита и пористого кремния, что является важным показателем для их применения в медицине и электронике в качестве антикоррозионных покрытий и для реализации оптических фильтров
MODELING AND ANALYSIS OF MOLECULAR DYNAMICS OF SILICON-SOLVENT-VINPOCETIN SYSTEMS AND SILICON-SOLVENT-VINPOCETIN DIOXIDE
The process of desorption of vinpocetine on the surface of crystalline silicon and silicon oxide in various media has been studied by molecular dynamics modeling. The desorption of vinpocetine in water has been established both from the surface of silicon and from the surface of silicon oxide. The character of the desorption of vinpocetine from silicon and silicon oxide at pH 6.8 and pH 7 differs insignificantly (within the error of the simulation results). The desorption of vinpocetine in acidic medium (pH 2) from silicon and silicon oxide occurs more efficiently and at a higher rate, compared to pH 6.8 and pH 7
Importance of defect nanocrystalline calcium hydroxyapatite characteristics for developing the dental biomimetic composites
Applying a set of structural-spectroscopic methods of analysis we have studied the relationships between the structure, morphology and sorption characteristics of the samples of nanocrystalline carbonate-substituted hydroxyapatite (C-HAP) synthesized with the use of biogenic calcium source (poultry eggshell) obtained by the chemical deposition from a solution. With the use of X-ray diffractometry and X-ray microanalysis it was found that the appearance of impurities in the structure of synthesized material was due to their presence in calcium carbonate of the poultry eggshell and this could result in the changes of parameters in the elementary crystal cell of hydroxyapatite without formation of the additional phosphate phases. Optical and ESR spectroscopy allowed us to find that in the presence of the inherited set of impurities inclusion of carbonate ions into the structure of our synthesized hydroxyapatite takes place with the formation of C-HAP of B-type. An increase in the content of phosphate groups PO 4 in the process of the materials synthesis in the atmosphere results in the reduction of that of one of structurally bound CO 3 groups. A decrease in the pH value in the solution during the synthesis connected with the increase in the PO 4 3− anions content leads to the change of morphology of the C-HAP samples due to the increase in the size of intracrystalline defects – nanopores at the surface of C-HAP nanocrystals. Such a change in the morphology of the materials resulted in the changes of the sorption characteristics of the samples that were measured by means of thermal desorption of nitrogen technique. The specific surface area of C-HAP powders determined by means of the BET technique was ∼55.5 ± 0.9 m 2 /g, exceeding by several times that of the known analogs. Meanwhile, despite the developed surface the C-HAP samples remained rather stable in the atmosphere of the saturated water vapour and the main losses under polarization are related to Maxwell-Wagner losses. Analysis of characteristics for the C-HAP samples obtained from a biogenic source of calcium demonstrated their potential significance for obtaining of biomimetic materials imitating structure, morphology and anisotropy of the native hard tissues of the human tooth. © 2019 The AuthorsThe study was performed under the support of the grant Russian Foundation for Basic Research (RFBR) № 18-29-11008 mk. The work was partly supported by Ministry of Education, Youth and Sport of the Czech Republic (grant numbers LM2015088 , LO1409 ) and Contract No. 02.A03.21.0006 of the Government of the Russian Federation . Appendix
Microstructure and electrical transport properties of nanoscale [(CO
We investigated the role of microstructure and In2O3/C interlayer thickness on the electrical transport properties of [(Co40Fe40B20)34(SiO2)66/(In2O3)/C]46 multilayers prepared using ion-beam sputtering. These multilayers were characterized using an X-ray diffraction, X-ray reflectivity, impedance spectroscopy, and magnetoresistive measurements. The X-ray diffraction data showed that regardless of the layer thickness, all components of the multilayers are X-ray amorphous. Fitting X-ray reflectivity data, multilayer periodicities are extracted and layers thicknesses, densities and roughnesses are determined. Impedance spectroscopy has shown a resistive-capacitive coupling between electrically conductive ferromagnetic CoFeB clusters which corresponds to the model of a prepercolation composite. For the thinnest multilayer with nonmagnetic In2O3/C interlayer thickness of about 1.6 nm, we managed to achieve a magnetoresistance of about 0.8% at room temperature and 3.2% at cryogenic temperature