Liquid crystals can exhibit structural orientational order. The creation of a mixture with the addition of chiral molecules to the nematic liquid crystal induces helical twisting, the axis of which is directed perpendicular to the cell surfaces. When some cholesteric mixtures with a sufficiently short spiral pitch (up to 400-500 nm) are heated to a temperature close to, but still lower than, the temperature of the main transition to the isotropic state, in some cases the so-called blue phases can be formed. We carried out a study on the detection of structural manifestations of the blue phase under the action of vapors of chemical substances, in particular acetone. The main dependences of effect of acetone on the liquid crystal mixture depending on the concentration were also revealed. The two-stage phase transformation from cholesteric liquid crystal to the isotropic liquid via the intermediary blue phase could be clearly recorded by changes in optical transmission. Possible applications are discussed.

В роботі наведено результати схемотопологічного проектування і ком'ютерного моделювання операційного підсилювача на основі комплементарних (КМОН)-структур за стандартною промисловою планарною КМОН-технологією на кремнієвих пластинах КДБ-40 з кишенями n-типу провідності. Операційний підсилювач розроблявся для реалізації інтегрального перетворювача сигналів (ІПС) фотоплетизмографії, особливістю якого є можливість регулювання та фільтрація амплітуди постійної складової у підсиленому сигналі від діодного фоточутливого елементу в діапазоні хвиль 400 - 1040 нм. Розроблений ІПС є придатним для створення реальних пристроїв в інтегральному виконанні, як елемент сенсорних мікросистем-на-кристалі або інтелектуальних сенсорів.

In this paper, a theoretical analysis and a practical study of the transient processes occurring when the LED modules are switched on are carried out. Light-emitting diode (LED) modules are a parallel, serial or mixed connection of individual light-emitting diodes in a discrete or integrated design. The non-uniformity of the voltage drop at the moment of switching on series-connected LEDs or series-connected LED cells containing parallel-connected LEDs is shown. This may be the reason for a short-term electrical breakdown of their p-n junctions. The obtained results can be useful for predicting the durability and reliability of LED devices.

The paper investigates the properties of an antireflective film for a photodetector made of indium antimonide (InSb), configured for transmission in the infrared range (3.5-5.0 mu m), which coincides with the absorption peak of carbon dioxide (CO2). The film is a four-layer coating formed by the following materials: silicon dioxide (SiO2), silicon monoxide (SiO), silicon suboxide (SiO1

The paper presents the results of circuit topological design and layout simulation of the operational amplifier based on complementary (CMOS) structures using the standard industrial planar CMOS technology on KDB-40 silicon wafers with n-type conductivity wells. The operational amplifier was developed for the implementation of an integral converter signals (ICS) of photoplethysmography, the feature of which is the amplitude regulation and filtering of the constant component in the amplified signal from the diode photosensitive element in the wave range of 400 divided by 1040 nm. The developed ICS is suitable for creating real devices in an integrated implementation, as an element of sensor microsystems-on-a-crystal or smart sensors.

The work of an optical sensor for determining the concentration of alcohols, in particular methanol, ethanol and isopropanol, based on a liquid crystal sensitive element, was studied. The sensitive element is a mixture of cholesteric liquid crystal CB15 and nematic impurity E7. The detection and reaction of the sensitive element to the presence of alcohol vapors is investigated.

A theoretical analysis of the initial charge and discharge processes in consecutive connected sections of the battery under the action of rectangular pulses was carried out, in particular, their influence on the uniformity of energy accumulation and return. The non-uniformity of energy accumulation and return between sections is shown. The equivalent electrical circuit of both single and serially connected battery sections is given. On the basis of equivalent electrical circuits, computer simulation of charge-discharge processes was carried out in the LT SPICE application program package.

In CMOS inverters, the main part of the power supply is spent on charging the parasitic capacitance of the transistor gates and the load capacitance. Associated with this portion of energy is dynamic power consumption, which has two components—transient power consumption and capacitive-load power consumption. When the logic states of the inverter change in a short period of time, when the PMOS and NMOS transistors are switched simultaneously, a short-circuit current flows. Power losses from short-circuit current are only a small part of dynamic power consumption. For this reason, more attention is paid to reducing transient power consumption and capacitive-load power consumption. However, with the reduction in the size of the inverter transistors and the lowering of their threshold voltage, the short-circuit power losses must also be taken into account. Also, when the size of inverter transistors increases in powerful output buffers, the short-circuit current increases, which, in addition to increasing short-circuit power losses, can cause errors in the output logic. Therefore, the purpose of this work is to reduce short-circuit current and dynamic power consumption of the CMOS inverter. For this purpose, it is proposed to limit the short-circuit current by changing the state of additional PMOS and NMOS transistors included in the path of the short-circuit current. The state of additional transistors is changed by an additional clock signal with a special wave-form during the rising and falling edges of the main clock signal.

The paper proposes a model of an electromagnetic radiation sensor that uses the precession of the magnetization vector in a ferromagnet (ferromagnetic resonance) as a result of absorbing the energy of an incident electromagnetic wave, the generation of a spin current as a result of this precession, the generation of a spin-polarized current as a result of the passage of a spin current in a non-magnetic metal, and a change in the direction of magnetization of a ferromagnetic layer with a low coercive force (free layer) due to the passage of a spin-polarized current. Then the radiation will be detected by its effect on the electrical resistance of the entire structure, which depends on the mutual directions (parallel or antiparallel) of magnetization of the free and fixed (with a large coercive force) ferromagnetic layers (phenomenon of giant magnetic resistance). The dependence of the spin-polarized current in the device on the frequency and amplitude of the incident electromagnetic wave with linear polarization was calculated. A method of calculating the range of amplitude and frequency values of radiation that can be detected by the sensor has been developed. The parameters of this model are the detection time and the number of spin gates in one sensor. Calculations are given for a ferromagnetic layer made of permalloy and for spin valves with four different critical current values that determine the process of remagnetization of the free layer: 20, 50, 100, and 200 microamps.

The paper presents the results of computer modeling of the proposed functional-electrical circuit of integrated signal converters (ISC) from photosensitive elements based on CMOS operational amplifiers, which is intended for the construction of an element base of hybrid sensor microsystems for biomedical applications. A feature of this ISC is the regulation and filtering of the amplitude of the constant component in the amplified signal from the diode photosensitive element in the wave range of 400 - 1040 nm. Computer simulation of the functioning of the device was carried out, the constituent components were determined and their parametric optimization was carried out. The results of experimental studies and computer modeling agree well, which confirms the correct functioning of the proposed signal converter from photosensitive elements. The developed ISC is suitable for creating real devices, both on the basis of discrete components and in an integrated design, as an element of sensor microsystems-on-a-chip or intelligent sensors.

The process of detailed research of the transient process, which takes place in the sensitive element of the liquid crystal sensor during interaction with acetone vapors, is described. The abrupt transition of the liquid crystal to the isotropic state is one of the main obstacles which prevents the construction of an acetone liquid crystal sensor. A mixture of nematic liquid crystal E7 and cholesteric impurity CB15 was used as a sensitive element.

The article deals with to the study of the peculiarities of charge carrier transfer in polycrystalline films of SOI-structures, doped with boron to concentrations corresponding to the metal-insulator transition. The magnetoresistance of polysilicon in SOI-structures under the action of magnetic fields up to 14 T at temperatures of 4.2 K was studied. A detailed analysis of the results of studies of the magnetic transport properties of poly-Si was performed. It is established that at low-temperature transfer of charge carriers in polycrystalline films there is a hopping conductivity, the parameters of which can be estimated by strong spin-orbit interaction within the framework of the theory of weak localization.

The article is devoted to modelling the growth of thin films on the surfaces of crystals having a similar crystal structure with a small parameter of mismatch of the lattice of substances from which the film and the crystal substrate are formed. A review of modelling methods based on both analytical expressions and computational methods is made. A number of methods for modelling the most typical processes: surface formation in the form of pyramidal formations (so-called needle crystals), two-dimensional with initial islands of growth and three-dimensional uneven growth processes. To model the process of growth of needle crystals, it is proposed to use a method based on Gaussian statistics of surface height increments. The model of three-dimensional growth of the crystal surface, which uses the iterative algorithm of Foss, and which makes it possible to investigate the processes of stepped, uneven growth of crystals, is also considered. In contrast to stepwise growth, a model of submonolayer growth of a film based on the Monte Carlo method is considered. For submonolayer growth of the film, pseudo-random sequences are used, which simulate the initial arrangement of the nuclei of the nucleus of the next layer on the crystal surface. The computational characteristics of this method are determined, namely the dependence of the number of iterations on the initial surface filling coefficient.

Стаття присвячена вивченню особливостей перенесення носіїв заряду полікристалічних плівках в КНІ-структурах, легованих бором до концентрацій, які відповідають переходу метал-діелектрик. Досліджено магнетоопір полікремнію в КНІ-структурах під дією магнітних полів до 14 Тл за температур 4,2 К. Проведено детальний аналіз результатів досліджень магніто–транспортних властивостей полі-Si. Встановлено, що за низькотемпературного перенесення носіїв заряду в полікристалічних плівках присутня стрибкова провідність, параметри якої можуть бути оцінені за сильної спін-орбітальної взаємодії в рамках теорії слабкої локалізації.

The article considers the physical processes associated with the propagation of electromagnetic oscillations in a long line, the size of which is the same or slightly greater than the length of the electromagnetic wave (not more than ten times). As a research method, the differential-symbolic method is used, which is applied to the modified equation of the telegraph line. The boundary conditions for the two-point problem as well as additional parameters that are coefficients for the first derivatives in terms of coordinate and time in comparison with the classical equation of the telegraph line are considered as parameters for controlling the process of propagation of electromagnetic oscillations. Based on the differential-symbolic method, the boundary conditions of the two-point problem are found, under which the most characteristic oscillatory processes are realized in a long line. Based on the research, it is possible to draw conclusions about the effectiveness of analytical methods for the analysis of specific technical objects and control of the processes that take place in them.

The article shows the results of modeling the electrical circuits of integrated sensor as part of the CMOS inverter. Capacitor, inductor and MOS transistor were used as the integrated sensor. The change of sensor values is detected by a circuit containing three stages: input buffer, amplifier and repeater. The integral sensor is connected to the gate of one of the MOS transistors of input buffer. Shows how the change in the value of the integrated sensor affects the shape of the output signal of the measuring circuit.

The use of an integrated sensor element as an addition of inverter, which converts the resistance of a sensitive element into the level of the output pulse signal, is investigated. Inverter circuits with different control options for sub-channel areas of MOS transistors are modeled in the LTSpice program. Based on the simulation results, dependencies graphs of the output signal amplitude on the resistance of a sensitive element and sensor’s sensitivity are drawn, and the shapes of the output signals are shown.

The work is based on research magnetotoconductance polysilicon layer in SemOI-structures, which are under the influence of a magnetic field up to 14 T at temperatures of liquefied helium. The samples were subjected to deformation to determine the effect of material dispersion on low-temperature conductivity. Considered occurrence from capacitive relative magnetic conductivity at liquefied helium temperatures is caused by superposition of charge carriers at low temperatures in magnetic fields with Bcr ~ 3T in the framework of the quantum transfer mechanism model. The determined concentration of polysilicon samples must be used in the development of sensors of mechanical quantities, operational in difficult operating conditions, namely under the influence of deformation in strong magnetic fields up to 14T at temperatures of 4.2 K.

This article presents the results of circuit-technical modeling of integral sensor capacitive elements built directly into the microsystem-on-crystal for the research and evaluation of changes in the capacities of elements in the ranges of their small values within 0.1-1.0 pF. The capacitive elements under study are integrated into a circuit containing an input inverter, a trigger type amplifier and an output signal cascade. The investigated capacities elements were connected in parallel to the gate capacities of the input CMOS inverter. Such switching changes the capacities gates of the transistors of the input CMOS inverter, which affects the period and amplitude of the output pulses, which is detected and amplified by the trigger and the output cascade.