Energy spectrum of a multicomponent flux of accelerated ions

We have experimentally studied the energy spectrum of an accelerated ion beam moving in a drift gap upon separation by a grid electrode system from a metal plasma jet of a pulsed high-current vacuum arc. It is established that the average energy per unit ion charge in the beam is below the value corresponding to the accelerating voltage. The width of the energy spectrum of accelerated ions is close to their average energy and significantly exceeds the width of the energy spectrum of the initial beam. The results of model calculations show that the observed phenomena can be explained by the action of a nonstationary electric field of the space charge of the ion beam transported via the drift gap.     

Generation of accelerated electrons in a gas diode with hot channel

Generation of fast electrons in an inhomogeneous medium composed of a hot channel (spark channel, laser plume, etc.) surrounded by air under normal conditions has been numerically analyzed. The model used makes it possible to carry out consistent calculation of the formation of subnanosecond gas discharge and generation of accelerated electrons under these conditions. The fast-electron current is found to consist of two pulses. One of them has an amplitude of 50 A, width of 30 ps, and electron energy of more than 100 keV. These electrons are generated in the hot channel. The other pulse has an amplitude of 170 A, width of 20 ps, and electron energy in the range of 8–50 keV. These electrons are generated in cold air. Since these pulses pass successively and barely overlap, the total width of fast-electron pulse is almost 50 ps.     

1.5–1.6 μm photoluminescence of silicon layers with a high density of lattice defects

This study is concerned with photoluminescence of nanostructured silicon layers that emit radiation in the wavelength range 1.5–1.6 μm due to optical transitions to deep levels of recombination centers produced by crystal lattice defects. It is shown that the dependence of the photoluminescence intensity on the excitation power density is adequately described by the model of deep levels of one type. A shift of the photoluminescence peak to shorter wavelengths with increasing excitation power density is observed. The shift is indicative of changes in the occupancy of deep levels in the conditions of transfer of charge carriers between recombination centers.     

Observation and nucleation control of Ge nanoislands on Si(111) surfaces using scanning reflection electron microscopy

Using a high-resolution scanning reflection electron microscope with multifunctions, we investigate Ge nucleation processes on clean Si(111) surfaces and form Ge islands on them by controlling step arrangements of Si(111) surfaces and by using focused electron beam (EB)-induced surface reactions. It is found that three-dimensional (3D) Ge islands grow selectively at step band areas on the surfaces without growth of the islands at terrace areas. Three-dimensional Ge nanoislands are formed at given points by stimulating the Ge wetting layer using focused electron beams and scanning tunnelling microscopy. Ge nanoislands are also formed by depositing Ge on Si windows in ultrathin SiO2 films and subsequent annealing of the sample. The islands are formed only at the window positions. These results imply new methods for forming Ge quantum dots or nanostructures at given areas.     

Simulating gas-discharge processes at a single cold microscopic point

The development of ionization avalanches in nitrogen at atmospheric pressure near a single cold microscopic point on a cathode surface has been simulated under the conditions of E/P ≫ 1 kV/(cm Torr), where E is the electric field strength and P is the gas pressure. It is established that a layer of dense gas-discharge plasma with a density of ∼10¹⁶ cm⁻³ is formed within a period of ∼1 ps as a result of the gas ionization by electrons emitted from the cathode. The current of fast electrons, which appears due to gas ionization is more than ten times greater than the field emission current and can reach I ∼ 1 A for one microscopic point.     

Structural Changes in Nanometer-Thick Silicon-on-Insulator Films During High-Temperature Annealing

Semiconductors - The thermal stability of silicon-on-insulator films with a thickness of 4.7  and 2.2 nm is studied as a function of annealing temperature in the range of...     

An energy-saving overload-control technology based on a computerized training-machine system

Energy-efficient control of electric drives of an overload machine and operator training for a computerized practice-machine system (CPMS) are considered. The energy consumption of an overload machine depends on the kind of control actions taken by the operator and dynamic characteristics and modes of use of the drives, which has to do with the level of the operator’s professional training. Unreasonably abrupt accelerations and hard braking increase the wear of electromechanical equipment and lead to additional electricity consumption. The energy-saving technology of overload machine control is based on presenting the operator’s work as a functionally complete set of tasks (practice exercises) formally presented as a set of tasks for optimal electric-drive control. The solution of these tasks forms a system of wanted paths and controls used as advising actions in the practice-machine system when doing a set of practices. The results of designing a computerized simulator system (CPMS) for overload machine operators are presented. The training in this system makes it possible to form skills of energy-saving control over process equipment. The operator forms his sensory motor skills in the CPMS by doing a set of practices to simulate the actual technological operations of the overload process. The CPMS is designed to accumulate, store, and process data on the acquisition of professional skills and expertise by a trainee. The structure of the skill-formation control system is given as a component of the CPMS, and its connection with the computerized simulator (overload modeling unit) is also considered.