Proceedings of the National Academy of Sciences of Belarus. Series of Physical-Mathematical Sciences / Известия Национальной академии наук Беларуси. Серия физико-математических наук
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Светоизлучающие структуры на основе нестехиометрического нитрида кремния
Get PDFThe two triple-layered SiO2 /SiNx /SiO2 structures with Si-rich and N-rich silicon nitride active layer were fabricated on p-type Si-substrates by chemical vapour deposition. The SiNx layer of different composition (x = 0.9 and x = 1.4) was obtained by changing the ratio of the SiH2 Cl2 /NH3 flow rates during deposition of a silicon nitride active layer (8/1 and 1/8, respectively). The spectroscopic ellipsometry and photoluminescence (PL) measurements showed that the refractive index, the absorbance and luminescence properties depend on a chemical composition of silicon nitride layers. The structures with Si-rich and N-rich SiNx active layers emit in the red (1.9 eV) and blue (2.6 eV) spectral ranges, respectively. The PL intensities of different structures are comparable. The rapid thermal annealing results in the intensity decrease and in the PL spectra narrowing in the case of SiN1,4 active layer, whereas the increase in the emission intensity and the PL spectra broadening are observed in the case of the annealed sample with a SiN0,9 active layer. The PL origin and the effect of annealing treatment have been discussed, taking into account the band tail mechanism of radiative recombination. Multilayered (SiO2 /SiNx )n /Si structures are of practical interest for creation of effective light sources on the basis of current Si technology.Методом химического газофазного осаждения на кремниевых подложках p-типа изготовлены две трехслойные структуры SiO2 /SiNx /SiO2 с нестехиометрическими пленками нитрида кремния, обогащенными кремнием (x = 0,9) или азотом (x = 1,4), в качестве активных слоев. Активные слои SiNx нестехиометрического состава (x = 0,9 и x = 1,4) получены при различном соотношении реагирующих газов (SiH2 Cl2 /NH3 ) в процессе осаждения (8/1 и 1/8 соответственно). Методами спектральной эллипсометрии и фотолюминесценции показано, что показатель преломления, поглощение и люминесцентные свойства зависят от стехиометрического состава нитрида кремния. Структуры с активными слоями нитрида с избытком кремния и азота излучают в красной (1,9 эВ) и синей (2,6 эВ) областях спектра соответственно, причем интенсивность свечения сравнима для двух образцов. Быстрая термическая обработка приводит к уменьшению интенсивности и сужению спектра фотолюминесценции образца с активным слоем SiN1,4 , тогда как для образца с активным слоем SiN0,9 наблюдается возрастание интенсивности люминесценции с уширением спектра в коротковолновую область после отжига. Природа видимого свечения и влияние термообработки объясняются c учетом существования протяженной зоны хвостовых состояний.Структуры с чередующимися слоями оксида и нитрида кремния представляют практический интерес для создания эффективных источников света на базе кремниевой технологии
Когомологии Тейта специальных норменных модулей, связанных с гензелевыми алгебрами с делением
Get PDFFor central division algebras D over Henselian fields K with unitary K/k-involutions the Tate cohomology groups of Z/(2)-modules A = NZ̅ /K̅(NrdD̅(D̅*)), where K̅ , D̅ are the residue algebras of K and D, respectively, Z̅ is the center of D̅ , and NZ̅ / K̅ is the norm map from Z̅ to K̅ , are computed. Moreover, D is assumed to be tamely ramified K-algebra and a field k̅ belongs either to the class of C1 -fields, or to the class of totally imaginary global fields
ПРЕОБРАЗОВАТЕЛЬ ИК-ИЗЛУЧЕНИЯ НА БАЗЕ МИКРОРЕЗОНАТОРОВ ФАБРИ – ПЕРО
Get PDFThe method of transformation of information from one spectral range to another based on Fabry – Perot microresonators is offered. The method uses incident radiation of an object as affecting a microresonator material (a microresonator material must absorb this radiation), and visible radiation of the optical part of the spectrum as sensing, or reading radiation (a microresonator material should not absorb this radiation). The absorbed energy of incident radiation leads to a change in a microcavity temperature, which results in a change in the optical base of the resonator. The high sensitivity of the Fabry – Perot microcavities is a consequence of the fact that the principle of their operation is based on the physical phenomenon of multipath interference. A common shortcoming of the Fabry – Perot standards is their sensitivity to operating conditions, for example, to a change in the ambient temperature, which also leads to a change in the optical base of the resonator, as well as the influence of IR radiation. This leads to a shift in the spectral characteristics of transmittance or reflection of the Fabry – Perot standards, which worsens their performance characteristics. The method allows one to minimize the environmental temperature fluctuation influence on characteristics of the Fabry – Perot microresonator, which is an element that transforms the information from one spectral range to another. Minimization is performed when the starting temperature point of the microresonator corresponds to a maximum change in the probing radiation intensity due to the temperature
Отражение от космологического барьера в осциллирующей вселенной де Ситтера частиц Дирака, Майораны и Вейля
Get PDFIt is known that the geometry of the Lobachevsky space acts on the fields of particles with spins 0, 1/2, 1 as an ideal mirror distributed in space. The depth of penetration of the field in such a medium increases with increasing field energy. Since the Lobachevsky model is a constituent element in some cosmological models, this property means that in such models it is necessary to take into account the effect of the presence of a “cosmological mirror”; it must lead to a redistribution of the particle density in space. The earlier analysis assumed the static nature of the space-time geometry. In this article, we generalize the research of the spin 1/2 field in the case of the oscillating model of the de Sitter universe. The Dirac equation is solved in the non-static quasi-Cartesian coordinates. At this, we substantially use the diagonalization of a generalized helicity operator. The wave functions of the particle are nontrivially time-dependent; however the effect of a complete reflection of the particles from an effective potential barrier is preserved. For the real Majorana 4-spinor field, the similar results are valid. For the solutions describing the reflection effect to be constructed, we must use linear combinations of solutions with opposite helicities. Such combinations are forbidden for 2-component Weyl particles, for this reason such particles cannot be reflected by the cosmological barrier
НОВЫЕ ПРОЕКТЫ ОИЯИ И СОТРУДНИЧЕСТВО С БЕЛОРУССКИМИ УЧЕНЫМИ
Get PDFThe issues of the international cooperation of Belarusian organizations with the Joint Institute for Nuclear Research within the framework of international projects with the participation of scientists and specialists of Belarus are considered. Рассматриваются вопросы международного сотрудничества белорусских организаций с Объединенным институтом ядерных исследований в рамках международных проектов с участием белорусских ученых и специалистов.
ВЗАИМОДЕЙСТВУЮЩЕЕ СКАЛЯРНОЕ ПОЛЕ В ТЕОРИИ ГРАВИТАЦИИ
Get PDFIn the framework of the scalar-tensor theory of gravitation, a scalar field is considered, whose source is the trace of own energy-momentum tensor and the trace of the energy-momentum tensor of matter. The potential that enters the Lagrangian of a scalar field depends on three parameters: scalar interaction constant, scalar field mass, and constant that determines the minimum of the field energy. The representation of the scalar-tensor theory on the Minkowski background with a linear connection between the metric and the tensor gravitational potential is considered, and the additional conditions for field equations are obtained that restriction a tensor field over its spin states. For a cosmological problem, it is shown that additional conditions lead to a spatially flat universe according to observations. Numerical solutions of field equations are obtained and on their basis it is shown that the cosmological parameters of the model well describe modern observational data and the scalar field under consideration can then successfully simulate dark energy. The area of variation of parameters of the cosmological solution was studied and a cosmological scalar-tensor solution was compared with the ΛCDM-model of General Relativity. Depending on the model parameters for cosmological evolution, possible scenarios are analyzed.
ФОРМАЛИЗОВАННОЕ ПОЛУЧЕНИЕ КОММУНИКАЦИОННЫХ ОПЕРАЦИЙ ПАРАЛЛЕЛЬНЫХ ЗЕРНИСТЫХ АЛГОРИТМОВ
Get PDFAlgorithms designed for implementation on parallel computers with distributed memory consist of computational macro operations (calculation grains) and communication operations specifying the data arrays exchange between computing nodes. The major difficulty is how to find an efficient way to organize the data exchange. To solve this problem, it is first necessary to identify information dependences between macro operations and then to generate the communication operations caused by these dependences. To automate and simplify the process of code generation, it is necessary to formalize communication operations. The formalization is known for the case of homogeneous information dependences. Such formalization uses the vectors of global dependences as a representation of dependences between the calculation grains. Also, there is a way that makes it possible to obtain the data arrays exchange, but it requires the usage of tools to work with polyhedra and does not formalize communication operations. This article presents a formalization method and a method of inclusion of communication operations into the algorithm structure (receiving and sending data arrays) in case of a parallel algorithm with affine dependences. The usage of functions determining the relationship between macro operations allowed obtaining explicit representations of communication operations. This work is a generalization of the formalization of the operations of sending data in a parallel algorithm, where operations are not divided into macro operations, as well as a generalization of some aspects of obtaining the communication operation method.
УПРАВЛЕНИЕ АНСАМБЛЕМ ЛИНЕЙНЫХ ДВУХПАРАМЕТРИЧЕСКИХ ДИСКРЕТНЫХ СИСТЕМ1
Get PDFThe controllability of discrete systems with uncertainties is considered in this article. The concept of the ensemble of linear two-parameter discrete systems is introduced as a set of systems, whose coefficients belong to some given sets. The following problem is considered: for any initial state from the pre-assigned sets, one and the same control (universal control) is found for all ensemble systems reducing all solutions of these systems to a minimum zero neighborhood for finite time. In the case of interval uncertainty, finding the control is reduced to solving a nonlinear programming problem formulated in terms of the coefficients of the ensemble systems and the interval set of initial states. A constructive algorithm for building a desired control is proposed, an example is given.Данная статья посвящена исследованию задачи управляемости дискретной системы с неопределенностями. Введено понятие ансамбля дискретных двухпараметрических линейных систем – как совокупности систем, коэффициенты которых принадлежат некоторым заданным множествам. Рассмотрена задача: для любого начального состояния из наперед заданного множества найти одно и то же управление (универсальное управление) для всех систем ансамбля, переводящее все решения этих систем в минимальную окрестность нуля за конечное время. В случае интервальной неопределенности нахождение управления сведено к решению задачи нелинейного программирования, сформулированной по коэффициентам систем ансамбля и интервальному множеству начальных состояний. Предложен конструктивный алгоритм построения искомого управления, приведен пример.