Table of contents

Electrostatically actuated MEMS switch with the active contact breaking mechanism is tested in a "hot" regime. In this mode the lifetime of the switch is sufficiently restricted by the electrical failure mechanisms occurring at the contacts. Input DC voltage is applied to the source electrode during the actuation, output voltage at the drain electrode is registered. Measurements of the working characteristics of the switch including actuation voltage, contact resistance and lifecycle are performed. Experimental data is compared with the results of finite element simulation.

The results of the simulation of an ultrashort pulse generator with a 4H-SiC diode avalanche shaper implemented as a superfast closing switch are presented. The possibility of shaping a voltage pulse with an amplitude of 3300 V and 19 picosecond rise time is demonstrated.

Induction heating and oxidation of cp-Ti samples surface using high frequency currents are studied. The dependency of heating up to the temperature from 800 to 1500 °C is determined depending on the current values from 1.5 to 3 kA on the inductor at 90 kHz. Experimental results are compared to the data of numerical simulation of heat transfer in titanium samples.

The measurement results for power consumption and current in the inductor and heating temperature of titanium disc-shaped and cylindrical samples when treated with high frequency currents within 90 to 120 kHz have been presented. The influence of the current in the inductor in the range of 0.3 to 8.5 kA on the heating kinetics of disc-shaped samples within 800 °C to 1500 °C in the air has been identified. A regression model describing the temperature change depending on the power consumed by the heat treatment device as well as its duration has been built.

Features of transmission at analog intermediate frequency signals on fiber – optical communication lines are considered. In view of these features the technique for check of developed optical transmission systems at analog intermediate frequency signals is offered. The results of experimental investigations are presented.

An actuator based on water electrolysis with a fast change of voltage polarity is presented. It demonstrates a new actuation principle allowing significant increase the operation frequency of the device due to fast termination of the produced gas. The actuator consists of a working chamber with metallic electrodes and supplying channels filled with an electrolyte. The chamber is formed in a layer of SU-8 and covered by a flexible polydimethylsiloxane membrane, which deforms as the pressure in the chamber increases. Design, fabrication procedure, and first tests of the actuator are described.

This paper presents design and technology optimization of RF MEMS switch based on the silicon carbide film. The universal optimization criterion for electromechanical parameters was calculated. The experimental results of determination of the technological critical factors are discussed. Recommendations for the subsequent technology improvement are presented.

We have created an ionization type Vacuum gauge with sensor element based on an array of vertically aligned carbon nanotubes. Obtained asymmetrical current-voltage characteristics at different voltage polarity on the electrode with the CNTs. It was found that when applying a negative potential on an electrode with the CNTs, the current in the gap is higher than at a positive potential. In the pressure range of 1 ÷ 10³ Torr vacuum gauge sensitivity was 6 mV/Torr (at a current of 4.5·10^-5 A) and in the range of 10^-5 ÷ 1 Torr was 10 mV/Torr (at a current of 1.3·10^-5 A). It is shown that the energy efficiency of vacuum gauge can be increased in the case where electrode with CNT operates as an emitter of electrons.

The paper deals with electrical properties of polycrystalline materials (GeSe)_x(CuAsSe₂)_1-x (x = 0.5 and 0.7) under high pressure (up to 45 GPa) conditions. The phenomenon of negative magnetoresistance was observed for studied materials.

On the base of the physical analytical models based on Poisson's equation, drift–diffusion and continuity equations the forward current–voltage characteristics of 6H-SiC and 4H-SiC type Schottky diode with Ni and Ti Schottky contact have been simulated. It is shown on the base of analysis of current–voltage characteristics in terms of classical thermionic emission theory it is shown that the proposed simulation model of Schottky diode corresponds to the almost "ideal" diode with ideality factor n equals 1.1. Because of this it is determined that the effective Schottky barrier height φ_B equals 1.57 eV and 1.17 eV for Ni/6H and Ti/4H silicon carbide Schottky diode type, respectively.

The effect of temperature on static and dynamic magnetization in Co-based amorphous microwires was investigated with the aim of potential applications in miniature temperature sensors. The wires of two compositions with different magnetostriction and Curie temperature in glass-cover and after removing the glass layer demonstrated very different temperature behaviour of the magnetization loops and magnetoimpedance. The mechanisms of the temperature effects are related to the residual stress distribution due to fast solidification, the difference in thermal expansion coefficient of metal and glass and the proximity to the Curie temperature. The interplay of these factors may result in a very strong temperature dependence of magnetoimpedance in a moderate temperature range (room temperature −373K). Such elements may be incorporated in various composite materials for a local temperature monitoring.

Adaptive behavior of resistive state in response to electrical stimulation has been studied for the silicon oxide based memristive nanostructures subjected to electroforming in the conditions of current compliance. The limitation of current and temperature during electroforming affects the parameters of growing conductive filaments and reduction-oxidation reactions resulting in a higher dynamic range of gradual resistance change important for neuromorphic applications.

The static mechanical properties of a bistable electromechanical drive with arcuate suspension is investigated. The behaviour of an arcuate suspension and the influence of the beam thickness modulation on the stability of both stationary states is studied experimentally and theoretically. The influence of the beam shape modulation on its potential energy was determined with finite element analysis. The simulation results were verified experimentally. In the study, the optimal modulation configuration is determined. With help of this modification the sustainability of both mechanically stable states is significantly improved.

HEMT transistors based on the structures of the AlGaN/SiC were created. All the basic characteristics of the transistors were studied and their operating parameters were determined, including power, leakage current, current saturation, etc. The influence of surface traps on the characteristics of the transistors by optical activation was investigated. The method for the passivation of traps based on thermal stabilization was developed.

Self-heating has an adverse effect on characteristics of gallium nitride (GaN) high electron mobility transistors (HEMTs). Various solutions to the problem have been proposed, however, a temperature rise due to dissipated electrical power still hinders the production of high power and high speed GaN devices. In this paper, thermal management of GaN HEMT via few-layer graphene (FLG) heat spreading elements is investigated. It is shown that integration of the FLG elements on top of the device structure considerably reduces the maximum temperature and improves the DC and small signal AC performance.

Effect of undoped GaAs spacer layer between AlGaAs emitter layer and C-doped GaAs base layer on DC characteristics of AlGaAs/GaAs HBTs with ledge structure was investigated. Devices with spacer layer thickness (∼3-5 nm) and optimal ledge geometry demonstrate stable high current gain (β_max = 120-140) combined with collector-emitter breakdown voltage of 23-25V.

We proposed a numerical model of the Gunn diode and resonant diode based on a single nitride nanowire. Important model parameters needed for development of the considered devices, namely layers thickness, composition and doping level were evaluated. It has been shown theoretically that the single GaN nanowire based Gunn diode is capable to operate in over 1 THz frequency regime.