89 research outputs found
Global transition path search for dislocation formation in Ge on Si(001)
Global optimization of transition paths in complex atomic scale systems is
addressed in the context of misfit dislocation formation in a strained Ge film
on Si(001). Such paths contain multiple intermediate minima connected by
minimum energy paths on the energy surface emerging from the atomic
interactions in the system. The challenge is to find which intermediate states
to include and to construct a path going through these intermediates in such a
way that the overall activation energy for the transition is minimal. In the
numerical approach presented here, intermediate minima are constructed by
heredity transformations of known minimum energy structures and by identifying
local minima in minimum energy paths calculated using a modified version of the
nudged elastic band method. Several mechanisms for the formation of a 90{\deg}
misfit dislocation at the Ge-Si interface are identified when this method is
used to construct transition paths connecting a homogeneously strained Ge film
and a film containing a misfit dislocation. One of these mechanisms which has
not been reported in the literature is detailed. The activation energy for this
path is calculated to be 26% smaller than the activation energy for half loop
formation of a full, isolated 60{\deg} dislocation. An extension of the common
neighbor analysis method involving characterization of the geometrical
arrangement of second nearest neighbors is used to identify and visualize the
dislocations and stacking faults
Test of the RF system for damping ring
RF system for VEPP-5 damping ring is described. The system consists of RF power supply, waveguide section, and 700 MHz cavity. Results of computer simulations and measurements of HOM spectrum and damping efficiency are presented together with the results of cavity testing at operating power level
Spin-Momentum Correlations in Quasi-Elastic Electron Scattering from Deuterium
We report on a measurement of spin-momentum correlations in quasi-elastic
scattering of longitudinally polarized electrons with an energy of 720 MeV from
vector-polarized deuterium. The spin correlation parameter was
measured for the reaction for missing
momenta up to 350 MeV/ at a four-momentum transfer squared of 0.21
(GeV/c). The data give detailed information about the spin structure of the
deuteron, and are in good agreement with the predictions of microscopic
calculations based on realistic nucleon-nucleon potentials and including
various spin-dependent reaction mechanism effects. The experiment demonstrates
in a most direct manner the effects of the D-state in the deuteron ground-state
wave function and shows the importance of isobar configurations for this
reaction.Comment: 4 pages, 3 figures, submitted to Phys. Rev. Lett. for publicatio
Measurement of the branching fraction of at KEDR
We present the study of the decay . The results
are based on of 5.2 million events collected by the KEDR detector at
VEPP-4M collider. The branching fraction is measured to be
where the first uncertainty is statistical, the second one
is systematic. This is the most precise single measurement of this quantity at
the moment
Compact Source of Electron Beam for Facility of Electron-Beam Welding with the Location of the Electron Gun and the Source of High Voltage in a Single Monoblock. Concept and Bench Tests of the Monoblok Prototype
Представлен прототип компактного источника электронного пучка для
установок электронно-лучевой
сварки с расположением электронной пушки и источника
высоковольтного напряжения в едином моноблоке. Размещение электронной пушки, источника
высоковольтного напряжения, электроники управления пучком и питания накала катода
источника электронного пучка для электронно-лучевой
сварки в едином корпусе-моноблоке
снижает вес и стоимость (за счёт уменьшения количества используемых материалов), объём
и занимаемые производственные площади. Это существенно расширяет возможности
применения представляемого типа источников электронного пучка в разнообразных областях
деятельности человека, в том числе в космических технологиях в открытом пространстве
космоса. Цель работы – показать целесообразность концепции компоновки источника электронного пучка в едином корпусе-моноблоке
на примере стендовых испытаний прототипа
источника-моноблока.
Спроектирован и изготовлен прототип источника-моноблока.
Проведены
его предварительные стендовые испытания с лазерным подогревом катода. Обсуждаются
возможные применения. Получен электронный ток источника до 70 мА с энергией 90 кэВ.
Данный результат демонстрирует возможность практической реализации нового способа
компоновки источника электронного пучкаA prototype of an electron beam compact source for electron-beam welding is presented. The electron gun and a high-voltage source are united in a single monoblock. The placement of the electron gun, the high-voltage source, the beam control electronics and the power supply of the cathode heating of the electron beam source for electron beam welding in a single monoblock housing reduces weight and cost by reducing the amount of materials used, volume and occupied production areas. This significantly expands the possibilities of using the presented type of electron beam sources in various fields of human activity, including space technologies in the open space of space. The purpose of the work is to show the expediency of the concept of arranging the electron beam source in the single monoblock housing as the example of bench tests of the source prototype. The prototype of the
monoblock was designed and manufactured. Its preliminary bench tests with laser cathode heating
were carried out. Its possible applications are discussed. An electron source current up to 70 mA
with an energy of 90 keV was obtained. The result obtained demonstrates the possibility of practical
implementation of a new method of arranging an electron beam sourc
Dislocation reduction of InAs nanofins prepared on Si substrate using metal-organic vapor-phase epitaxy
Using the phase-field crystal method in the multi-scale modeling of microstructure evolution
Molecular beam epitaxy of silicon : germanium nanostructures
The current status of the research in the field of synthesis and application of silicon and germanium-based nanostructures formed by the process of 3D island self-organization is reviewed in the present paper. There was an obvious conclusion that elastic deformations in epitaxial films and 3D islands are the key factor which is not only the reason of the transition from planar to Stranski-Krastanow mechanism of growth, but also influences the next stages of islands evolution including their shape, size and spatial distributions. There are many cases when this factor makes crucial changes to the classical set of phase-formation mechanisms right up to an equilibrium coexistence of islands on a surface. Various types of ordering were classified in the nanocluster systems under consideration: in cluster shape, in its size, in the distance between nearest islands, as well as ordering through vertical, i.e. in successively growing multilayer structures containing quantum dots. The results of recent original investigations of electrical and optical properties of self-assembled arrays of Ge quantum dots are presented. (C) 2000 Elsevier Science S.A. All rights reserved
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