arXiv subjects

Yu. N. Morokov

Publications and source records attributed to Yu. N. Morokov.

8 recordsLinked to original sources

arXiv2019

Simple mathematical model of aging

A simple mathematical model of the aging process for long-lived organisms is considered. The key point in this model is the assumption that the body does not have internal clocks that count out the chronological time at scales of decades. At these scales, we may limit ourselves by empirical consideration only the background (smoothed, averaged) processes. The body is dealing with internal biological factors, which can be considered as the biological clocks in suitable parameterization of corresponding variables. The dynamics of these variables is described using a system of autonomous ODEs. A particular representation of the right-hand side of equations in the form of quadratic polynomials is considered. In the simplest case of one variable we deal with a logistic equation, which has an analytical solution. Such quadratic model is justified if it is used to predict the dynamic of aging process for relatively small time intervals. However, since a well-defined biological interpretation can be given for the quadratic right-hand side of the equations, we can expect that the area of applicability of this simplified empirical model can extend to relatively large time intervals. The considered model is, in our opinion, a good and simple mathematical framework for organizing experimental data. The model may be useful to quantify and arrange the chains of causal relationships that may appear significant for the development of the aging process.

q-bio.OT↗

arXiv2017

Elastic Strain Fields In Lateral Double Ge/Si Quantum Dots

Simulations of the elastic strain fields for double Ge/Si quantum dots located on the same wetting layer are carried out. The cluster approximation is used for the atomistic model based on the Keating potential. The spatial distributions of the strain energy density and electron potential energy are calculated using clusters containing atoms of 150 coordination spheres. It is shown that the used cluster boundary conditions are close to the periodic boundary conditions.

cond-mat.mes-hall↗

arXiv2016

Calculation of Elastic Strain Fields for Single Ge/Si Quantum Dots

An atomistic model based on the Keating potential and the conjugate gradient method are used for simulation of the strain fields for single Ge/Si quantum dots. Calculations are performed in the cluster approximation using clusters containing about three million atoms belonging to 150 coordination spheres. The spatial distributions of the strain energy density and electron potential energy are calculated for different valleys forming the bottom of the silicon conduction band. It is shown that the strain field in silicon decreases sufficiently rapidly with distance from the center of the quantum dot, so the influence of the cluster boundary is observed only for very large quantum dots.

cond-mat.mes-hall↗

arXiv2016

Structures with Vertically Stacked Ge/Si Quantum Dots for Logical Operations

Ge/Si structures with vertically stacked quantum dots are simulated to implement the basic elements of a quantum computer for operation with electron spin states. Elastic-strain fields are simulated using the conjugate gradient method and an atomistic model based on the Keating potential. Calculations are performed in the cluster approximation using clusters containing about three million atoms belonging to 150 coordination spheres. The spatial distributions of the strain energy density and electron potential energy are calculated for different valleys forming the bottom of the silicon conduction band. It is shown that the development of multilayer structures with vertically stacked quantum dots makes it possible to fabricate deep potential wells for electrons with vertical tunnel coupling.

cond-mat.mes-hall↗

arXiv2000

Memory Effect in Silicon Nitride in Silicon Devices

The dominant dielectric used currently in silicon devices is silicon oxide. Its application for future devices will be impeded by several fundamental limitations which lead to low reliability of semiconductor devices and to the necessity of alternative dielectrics. Amorphous silicon nitride and oxynitride are considered now as alternative to silicon oxide in future devices. One of the unique property of amorphous silicon nitride is the electron and hole capture by the deep traps with extremely long life time (10 years) in the captured state (the memory effect). This property is employed in memory devices and microprocessors in computers. Despite numerous efforts the nature of traps responsible for the memory effect in this material is so far unclear. In this paper we discuss the nature of such traps using the quantum-chemical simulation. The calculations show that the defects responsible for the electron and hole capture in amorphous silicon nitride can be the Si-Si defects created by excess silicon atoms.

cond-mat↗

arXiv2000

Nature of traps responsible for failure of MOS devices

A failure of chips in a huge amount of modern electronic devices is connected as a rule with the undesirable capturing of charge (electrons and holes) by traps in a thin insulating film of silicon oxide in transistors. It leads to a breakdown of transistors or to a destructive change of their characteristics. It is suggested that silicon oxide will be replaced in the next generation of nanoscale devices by silicon oxynitride. Therefore, it is very important to understand the nature of traps in this material. We discuss this nature using the quantum-chemical simulation.

cond-mat↗

arXiv1999

The Schwarz-Hora effect: present-day situation

The electron-diffraction pattern at a nonfluorescent target was observed by Schwarz under attempts to modulate an electron beam by laser light. The pattern was of the same color as the laser light. The analysis of the literature shows there are the unresolved up to now significant contradictions between the theory and the Schwarz experiments. To resolve these contradictions, the interpretation of the Schwarz-Hora effect is considered, which is a development of the idea formulated by Schwarz and Hora. It is supposed that the interaction of electrons with the laser field inside a thin dielectric film is accompanied not only by the processes of absorption and stimulated emission of photons but also by formation of some metastable electron states in which the captured photons can be transferred with a following emission at the target.

quant-ph↗

arXiv1998

Long beating wavelength in the Schwarz-Hora effect

Thirty years ago, H.Schwarz has attempted to modulate an electron beam with optical frequency. When a 50-keV electron beam crossed a thin crystalline dielectric film illuminated with laser light, electrons produced the electron-diffraction pattern not only at a fluorescent target but also at a nonfluorescent target. In the latter case the pattern was of the same color as the laser light (the Schwarz-Hora effect). This effect was discussed extensively in the early 1970s. However, since 1972 no reports on the results of further attempts to repeat those experiments in other groups have appeared, while the failures of the initial such attempts have been explained by Schwarz. The analysis of the literature shows there are several unresolved up to now contradictions between the theory and the Schwarz experiments. In this work we consider the interpretation of the long-wavelength spatial beating of the Schwarz-Hora radiation. A more accurate expression for the spatial period has been obtained, taking into account the mode structure of the laser field within the dielectric film. It is shown that the discrepancy of more than 10% between the experimental and theoretical results for the spatial period cannot be reduced by using the existing quantum models that consider a collimated electron beam.

quant-ph↗