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In humans, respiratory disorders are common. Today, rapid, risk-free, and potentially low-cost diagnostics of respiratory disorders detected in the patient's exhaled air are critical. Fractional exhaled nitric oxide (FENO), volatile organic molecules, carbon monoxide, hydrocarbons, and hydrogen peroxide are among the inhaled biomarkers mentioned. Breathomics from exhaled volatile organic compounds and oximeters are also shortly discussed. The use of WO3 in FENO monitors is discussed. They large-scale produced and widely used in medical centers and clinics for diagnostics of respiratory diseases. Promising semiconductor sensors are manufactured from SnO2, doped with Pd, Au, or Pt or multi walls carbon nanotubes, gold nanoparticle with single wall carbon nanotubes, quartz microbalance devices with porphyrin, ITO –Zno-Pt films, and surface acoustic wave devices with isobutylene. A combination of VOCs is considered as a “molecular fingerprint” of breath. The electronic nose on metal oxide detectors allows investigating lung cancer and tuberculous.

Thick-film VOCs sensors based on ruthenated multi-walled carbon nanotubes coated with tin-dioxide nanoparticles (MWCNTs/SnO2) nanocomposite structures are prepared using three methods: hydrothermal synthesis, sol–gel technique and their combined method. It is shown that the optimal conditions for applications as acetone and toluene as well as ethanol and methanol vapors sensors in view of high response and selectivity relative to each other depend on choice of material synthesis method, mass ratio of the nanocomposite components and selected operating temperature. Selective sensitivity to acetone and toluene vapors at 150oC operating temperature MWCNTs/SnO2 are shown sensor structures with the mass ratio of the components 1:4 and 1:24, respectively. The samples with 1:200 mass ratio of the nanocomposite components are shown the selective response to acetone vapor exposure in the range of 200-250oC operating temperatures. The high sensitivity to ethanol and methanol vapors at 200oC operating temperature was revealed for the sensor structures made by different methods with the 1:8, 1:24, 1:50 and 1:66 ratios of the components, respectively. The results of research works related to the study of thick-film multiwall carbon nanotube–tin oxide nanocomposite sensors of propylene glycol (PG), dimethylformamide (DMF) and formaldehyde (FA) vapors are also presented in this paper. Investigations of response–recovery characteristics in the 50–300oC operating temperature range reveal that the optimal operating temperature for PG, DMF and FA vapor sensors, taking into account both high response and acceptable response and recovery times are about 200 and 220oC, respectively. The dependence of the sensor response on gas concentration is linear in all cases. Minimal propylene glycol, dimethylformamide and formaldehyde gas concentrations, where the perceptible signal was noticed, were 13, 5 and 115 ppm, respectively.

Thick-film VOCs sensors based on ruthenated multi-walled carbon nanotubes coated with tin-dioxide nanoparticles (MWCNTs/SnO2) nanocomposite structures are prepared using three methods: hydrothermal synthesis, sol–gel technique and their combined method. It is shown that the optimal conditions for applications as acetone and toluene as well as ethanol and methanol vapors sensors in view of high response and selectivity relative to each other depend on choice of material synthesis method, mass ratio of the nanocomposite components and selected operating temperature. Selective sensitivity to acetone and toluene vapors at 150oC operating temperature MWCNTs/SnO2 are shown sensor structures with the mass ratio of the components 1:4 and 1:24, respectively. The samples with 1:200 mass ratio of the nanocomposite components are shown the selective response to acetone vapor exposure in the range of 200-250oC operating temperatures. The high sensitivity to ethanol and methanol vapors at 200oC operating temperature was revealed for the sensor structures made by different methods with the 1:8, 1:24, 1:50 and 1:66 ratios of the components, respectively. The results of research works related to the study of thick-film multiwall carbon nanotube– tin oxide nanocomposite sensors of propylene glycol (PG), dimethylformamide (DMF) and formaldehyde (FA) vapors are also presented in this paper. Investigations of response–recovery characteristics in the 50–300oC operating temperature range reveal that the optimal operating temperature for PG, DMF and FA vapor sensors, taking into account both high response and acceptable response and recovery times are about 200 and 220oC, respectively. The dependence of the sensor response on gas concentration is linear in all cases. Minimal propylene glycol, dimethylformamide and formaldehyde gas concentrations, where the perceptible signal was noticed, were 13, 5 and 115 ppm, respectively.

A technology was developed for manufacturing solid-state semiconductor sensor sensitive to hydrogen peroxide vapors. Gas sensitive nanostructured films made of doped metal oxide SnO2 were manufactured by the high-frequency magnetron sputtering method. The chemical composition of prepared SnO2 targets was analyzed and the thickness of the deposited doped metal oxide film was measured. The morphology of the deposited Co-doped SnO2 film was studied by scanning electron microscopy. The gas sensing characteristics to the different concentrations of hydrogen peroxide vapors at various operating temperatures were also studied. The Co-doped SnO2 sensor showed enough sensitivity to very low concentration of hydrogen peroxide vapors (875 ppb) at the operating temperature of 100 °C. The SnO2 based sensor can be successfully used in medical diagnostic apparatus for determining low concentration of hydrogen peroxide vapors in exhaled air.

Results of the characterization and numerical analysis of InAsSbP composition strain-induced micro- and nanostructures shape transition are presented. Nucleation is performed from In-As-Sb-P quaternary composition liquid phase in Stranski–Krastanow growth mode. Geometric features and the shape transformation chronology of truncated pyramidal islands, lens-shape and pyramidal quantum dots (QDs) are under consideration, which opens up new possibilities at nanoscale engineering and nanoarchitecture of several types of nanostructures. High-resolution scanning electron (HR-SEM) and transmission electron (TEM) microscopes are used for micro- and nanostructures characterization. We show that as the islands volume decreases, the following succession of shape transitions are detected: truncated pyramid, {111} facetted pyramid, {111} and partially {105} facetted pyramid, completely unfacetted ‘pre-pyramid’, which gradually evolve to hemisphere and then again to pyramidal QD but with higher facet indexes. Critical sizes of islands shape transformation from ‘pre-pyramid’ to hemisphere (500–550 nm) and then from lens-shape again to pyramidal QDs (5–7 nm) are experimentally detected and theoretically evaluated. It is shown that theoretically calculated values coincide with experimentally obtained data.

A technology has been developed for obtaining a semiconductor solid solution SnO2 + Nb2O5 (80 : 20 wt %) and for manufacturing a thin-film nanoscale resistive sensor. The gas-sensitive characteristics of the sensor to various concentrations of liquefied petroleum gas (LPG) have been investigated. The SnO2❬Nb❭ sensor detects sensitivity to LPG from an operating temperature of 250°C when exposed to ultraviolet radiation. The temperature of 250°C was selected as the working temperature, at which the investigated sensor showed high sensitivity, operation speed and repeatability over time to the target gas. The SnO2❬Nb❭ structure can be used in security systems to detect LPG and determine its concentration.

A sensor sensitive to acetone vapors based on a Fe2O3❬Sn❭ metal oxide solid solution was fabricated by high-frequency magnetron sputtering. The gas-sensitivity of the manufactured sensor are investigated. The Fe2O3❬Sn❭ sensor shows sensitivity to acetone vapors starting from a temperature of 150°C under the influence of ultraviolet rays. The increase in operating temperature was accompanied by a linear increase in the sensor response. Exposure to ultraviolet rays not only improved the sensitivity of the sensor under study, but also increased its performance. A sensor based on Fe2O3❬Sn❭ can be successfully applied in acetone detectors.

The paper presents and discusses works carried out both at Yerevan State University and abroad on non-invasive metal oxide sensors (chemiresistors) for acetone exhaled by a diabetic. The technologies and parameters of chemiresistors based on tin dioxide, tungsten trioxide, zinc oxide, Fe2O3, In2O3 and TiO2 developed at YSU and in the world are presented. Most likely, it makes sense to start investigations start with concentration 1 ppm acetone, non-invasive metal oxide sensors, diabetes, response. The response of the MWCNT-doped SnO2 chemiresistors was measured at a concentration of acetone from 1 to 12 ppm, characteristic of diabetics at a relatively early stage of the disease.

The pseudobinary HgTe–CdTe, ZnTe–CdTe and HgTe–ZnTe systems were studied and Gibbs energy of mixing were determined at 400–1000 K temperature range. Miscibility gap analysis for CdZnHgTe quaternary material system is also performed by the Gibbs free energy calculations. Quantitative explorations show that there is no immiscibility gap for CdTe–HgTe material system in the mentioned above temperature range. In spite of that system, for the Cd1 – xZnxTe solid solutions, an immiscibility gap within x = 0.4–0.6 at T = 400 K already revealed. For the ZnTe–HgTe material system the situation is more complicated. Here, mutual incorporation of components is energetically favorable only up to impurity levels and an immiscibility gap occurs at entire compositions range starting from T = 800 K temperature and below. In addition, our calculations show that for the CdZnHgTe quaternary material system the immiscibility gap exists at the mentioned above temperature range and decreases at temperature increasing. Presented results can be useful at the growth of multicomponent bulk crystals, epitaxial thin films and nanostructures based on CdZnHgTe material system.

The review discusses the results of studies of gas sensors based on zinc oxide. Possibilities and technologies for the manufacture of such sensors are mentioned. ZnO sensors undoped, doped with impurities and carbon nanotubes, as well as sensors based on nanowires and quantum dots are considered. Possibilities of decreasing the operating (working) temperature of heating the working body of the sensors while maintaining a sufficiently high sensitivity to gases are shown. Recently developed ZnO sensors operate today at room temperature (without preheating their working body) in the absence of and under UV light from the sensor.

The interaction of H2O2 with the stoichiometric surface of (110) SnO2 was studied by first principle methods. Relaxed geometries, adsorption energies, and charge transfer between the molecule and the surface were calculated for several starting configurations of the H2O2 molecule and the SnO2 surface. The most probable adsorption sites and their optimized geometries are presented.

The sensitivity of gas sensors made of doped SnO2:Co metal oxide for the detection of hydrogen peroxide vapors in the environment was studied using current-voltage, frequency-capacitance, and transient characteristics. Their measurements were carried out at room temperature under the influence of ultraviolet light and without it. It is shown that the influence of ultraviolet rays on the active surface of the sensor increases the gas sensitivity of the sensor. Studies of transient characteristics have also shown that the resistance of the sensor when it is exposed to ultraviolet rays, already at room temperature, after the feeding-off of hydrogen peroxide vapors is almost completely restored.

Results of investigations of metal oxide chemical sensors for the detection of acetone made of tin dioxide were discussed in this review paper. There are several possibilities and technologies to manufacture of such sensors. Pure (without impurities) SnO2 and other metal oxide have low sensitivity to gases at its rather high pre-heating (operation) temperature. Doping of tin dioxide with some metals or carbon nanotubes is one way of improving the sensitivity of such metal oxide sensors. Another way is the preparation of nanosensors.

A ceramic target based on cobalt doped SnO2 metal oxide was synthesized by the solid-phase reaction method. The target was used in the process of high-frequency magnetron sputtering. A thin SnO2:Co film was deposited, which is sensitive to hydrogen peroxide vapor. The current-voltage characteristics of the SnO2:Co sensor were measured in the presence of hydrogen peroxide vapor in the environment while ultraviolet light was exposed to the sensor at room temperature. It was shown that the sensitivity of the SnO2:Co film increases by about 1.6 times when exposed to ultraviolet rays.

The continuum elasticity model is applied to investigate quantitatively the growth features and nucleation mechanism of quantum dots, nanopits, and joint QD-nanopits structures in CdZnHgTe quasyternary material system. We have shown that for the CdZnHgTe solid solution deposited on the CdTe substrate, the sign of the critical energy and volume of island is changed at the critical strain of ɛ* = 0.006 and ɛ* = 0.009 (ɛ = Δa/a), It is assumed that the mechanism of the nucleation is changed from the growth of quantum dots to the nucleation of nanopits at ɛ = ɛ*. Obviously, at the small mismatch (ɛ ɛ*, when the energy barrier becomes negative and a large mismatch provides a low-barrier path for the formation of dislocations, the nucleation of pits becomes preferable energetically.

Usually semiconductor gas sensors made from metal oxides need in high pre-heating of work body. Advantages for nanoscale sensors are possibilities to work at remarkable lower than 300°C temperature of its work body up to room temperature (practically without pre-heating of the sensor). Todays' experimental results obtained for gas sensors made from metal oxides are reported in this review.

Defects in the tin dioxide determine its main characteristics, which are widely used in gas sensors. In the tin dioxide, the native and impurity defects were investigated using the density functional theory. It was shown that the oxygen vacancies dominate between the uncharged defects and the cobalt atoms occupy the places of tin atoms in the case of the cobalt doping. The found defects structures explain the contradictory experimental results obtained previously.

In this work, the impedance spectroscopy is presented as a promising method for the investigation of the sensitivity of gas semiconductor sensors. The sensor made of the ZnO nanosize film doped with the 1 at.% La was manufactured and its sensitivity investigated to the hydrogen peroxide vapors. The advantages of impedance spectroscopy compared with the studies of current-voltage characteristics are shown.

A technique for recording a matrix of ring-shaped microstructures due to the postpolymerization of an already oriented layer of liquid crystal polymer under the influence of a focused intensive light radiation is developed. Using this technique, a microstructures matrix patterned element is realized. The reorientation process of the microstructure with the twist orientation in a homogeneously planar-oriented medium when an electric field is applied is investigated.

We present the results of studies of the nanocomposite MWCNTs/SnO2 hydrogen peroxide vapor sensors. The technology of manufacturing of these sensors has been developed. Because of the measurements of the temperature characteristics, the 100°C optimal operating temperature of the studied sensors has been found. The response and recovery curves of the sensors were investigated in the presence of different concentrations of hydrogen peroxide vapor in the atmosphere. A sufficiently high response was registered already at close to the threshold low concentrations of the target gas present in the air. In a double logarithmic scale, the linear dependence of the sensors response on the concentration of hydrogen peroxide vapor was observed in a certain concentration range. The minimal registered gas concentration is less than 1 ppm.

This study aimed to develop a high-performance hydrogen flexible sensor based on multi-walled carbon nanotube (MWCNT):SnO2 material. The MWCNT:SnO2 thin film was deposited onto a flexible polyimide substrate by the electron-beam deposition method to perform the low temperature detection of hydrogen. The thickness and surface morphology of the sensing layers have been determined by the thickness measuring profilometer and the scanning electron microscope (SEM), respectively. The flexible MWCNT:SnO2 sensor exhibited excellent sensitive characteristics to hydrogen in a range of 25–3000 ppm. H2 sensing parameters like sensor response, recovery, and response times were investigated at different operating temperatures. The minimum response and recovery times of the sensor corresponding to 1000 ppm H2 concentrations were found to be 37 and 554 s, respectively. The investigated sensing parameters demonstrate that this work can provide the possibility of a versatile route to fabricate flexible hydrogen sensor with high sensitivity and selectivity, which demonstrates its great potential in hydrogen leakage monitoring.

The microcrystalline Si layers with grain sizes of up to several tens of micrometers were grown. The physical vapor deposition (PVD), amorphous–liquid–crystalline (ALC) transition technique and a steady-state liquid phase epitaxy (SSLPE) are used for the fabrication of three different samples. The first sample under consideration was prepared first by deposition of a-Si onto glass substrates by PVD at room temperature, followed by heating from the front side to ~300°C and deposition of an indium metallic solvent. At the preparation of the second sample, an additional silicon layer with the thickness of 400 nm was deposited. A sample, when after that a c-Si was grown on the seed layer by SSLPE from indium solution is referred as a third sample. The resulting samples have a strong absorption edge in the mid-infrared region around 1960 cm−1. Six well-resolved oscillations with an average period of δB = 0.1214 T are revealed on the third sample’s magnetoresistance curve at gradually increasing of the magnetic field from zero up to 1.6 T. It is assumed that either Aharonov–Bohm effect or kinetic phenomena taking place in the grains boundaries at lateral current flow are responsible for those oscillations. Quantitative evaluations show that due to the strong absorption in mid-infrared region, enlargement of the photoresponse spectrum will occur and the efficiency of solar and other thermal energy conversion should be around ~10–15% higher than that of traditional PV cells based on silicon on glass structures.

Thin-film hydrogen peroxide vapor sensors made from Co-doped SnO2 and La-doped ZnO were manufactured using the high-frequency magnetron sputtering method. Thicknesses of deposited doped metal oxide films were measured and their morphology was investigated. The gas sensing characteristics of the prepared sensors were measured at different concentrations of hydrogen peroxide vapors and different operating temperatures of the sensor. It was found that both sensors made from doped metal oxides SnO2 and ZnO exhibit a sufficient response to 10 ppm of hydrogen peroxide vapors at the 200 and 220 ∘C operating temperature, respectively. It was established that the dependencies of the response on hydrogen peroxide vapor concentration have a linear character for prepared structures at the 150 ∘C operating temperature and can be used for determination of hydrogen peroxide vapor concentration.

The structure and defects of cobalt doped tin dioxide were investigated using the density functional theory and empirical force fields. The computations were carried out for different concentrations of cobalt (3.125, 6.25, 12.5, and 18.75 at%). It is shown that at the cobalt doping less than 4 at%, the oxygen vacancy occurs at the place of the oxygen bounded by cobalt. The electron density of states is computed when cobalt creates the states near a conduction band. By further increase in the cobalt concentration, the order of the structure begins to destroy.

A technique is developed for recording the centrally-symmetric liquid crystal phase plates with the anisotropic orientation of molecules providing a smooth change of the optical axis in a thin film of liquid crystal polymer. The technique enables one to record the elements with the cylindrically-symmetric and planar-symmetric distributions. Such structures can be used to develop the optical elements with the new functional possibilities. Using the developed techniques, the polarization-sensitive Fresnel lens is realized which is functioning either as a collecting or as a scattering lens for the light beams with the orthogonal circular polarizations.

The results of investigations of mid-infrared photodetectors based on InAsSbP quantum dot (QD) grown on InAs(100) substrate by modified liquid phase epitaxy are presented. The atomic force microscope measurements have shown that the surface density of grown QDs is (4–8) × 109 cm−2. Also, the morphology and crystalline quality of grown QDs are investigated by a scanning tunneling microscope. Photodetectors based on n-InAs(100) substrate with InAsSbP QDs on its surface were fabricated in the form of a photoconductor cell. The photoresponse spectrum extended up to 4 μm was observed. The optical properties of fabricated structures were investigated under He–Ne laser irradiation with wavelength of 1.15 μm. It was found that the relative surface conductance increases by 16% at power density of 0.15 W/cm2. Capacitance hysteresis with maximal remnant capacitance of 2.17 nF at 103 Hz was observed as well.

Gas sensing characteristics of multi-walled carbon nanotubes coated with tin dioxide nanoparticles nanocomposite thick-film structures (MWCNTs/SnO2) prepared using hydrothermal synthesis, sol–gel technique and their combined process were investigated. Gas response test measurements of all studied nanocomposite structures carried out in air/target gas mixture showed that the most and at one time selective response to butanol vapor exposure in comparison to other mainly toxic and harmful gases such as acetone, toluene, formaldehyde, dimethylformamide, and others is observed for samples obtained by hydrothermal synthesis with 1:4 and 1:200 weight ratios of the nanocomposite components, respectively. These sensors are characterized by relatively short response and recovery times about 12 and 100 s, respectively, as well as low operating temperatures in the range of 150–200°C.

The results of research works related to the study of thick-film multiwall carbon nanotube–tin oxide nanocomposite sensors of propylene glycol (PG), dimethylformamide (DMF) and formaldehyde (FA) vapors are presented in this paper. These sensors were derived using hydrothermal synthesis and sol–gel methods. Investigations of response–recovery characteristics in the 50–300 °C operating temperature range reveal that the optimal operating temperature for PG, DMF and FA vapor sensors, taking into account both high response and acceptable response and recovery times are about 200 and 220 °C, respectively. The dependence of the sensor response on gas concentration is linear in all cases. Minimal propylene glycol, dimethylformamide and formaldehyde gas concentrations, where the perceptible signal was noticed, were 13, 5 and 115 ppm, respectively.

Gas sensors made of carbon nanotubes without their doping and functionalization have serious shortcomings. Analysis of physics and technics of functionalization of carbon nanotubes by organic polymers, impurities, metalic nanoparticles/nanoclusters and use of nanotube in metaloxide nanocomposites for realization of detectors of different important gases with dramatically improved response, better time characteristics and smaller consumed power is carried out.

Technique for real-time spectropolarimetry is developed. An embedded system for circular dichroism registration is designed based on National Instruments single board reconfigurable I/O platform for ultraviolet and visible spectroscopic needs. The basic functional unit of the proposed device is liquid crystal polarization diffraction grating. In order to expand the dynamic range the control of data accumulation time is provided. Two NMOS sensor linear arrays provide an excellent linearity of response.

This work presents the results of investigations of a low bias mid-infrared(IR) photoconductive cell (PCC) with InAsSbP quantum dots (QDs). The self-assembled nanostructures were grown on an InAs(100) substrate by modified liquid phase epitaxy. The coarsening of the QDs due to Ostwald ripening was discussed. Hysteresis with a remnant capacitance of 0.483 pF and contra-directional oscillations on the PCC's capacitance–voltage characteristic at 78 K were observed. Additionally, peaks at 3.48, 3.68 and 3.89 μm on the room temperature photoresponse spectrum of a quantum dot photoconductive cell were detected. Room temperature photo-sensing properties were investigated under an irradiation of 3.39 μm as well. At a power density of 0.07 W cm−2, the surface resistance of quantum dot PCC was reduced by up to 7 %. A current responsivity of 0.2 mA W−1 was measured at an applied voltage of 8 mV.

Influence of humidity on properties of graphene was investigated and a comparison of graphene and polymer humidity sensors was carried out. It is shown the graphene sensors have higher response in comparison with nanoporous polymer membranes. The resistance of the latter ones is 150 GOhm and decreases in 7.5 times in case of 60% relative humidity. The resistance of graphene decreases in 4 times from 100 kOhm. This was shown to be due to the expanding of band gap of graphene caused by the adsorbed water that may create the defects in the lattice or transfer the charge, the sign of which depends on the relative position of HOMO and LOMO of water and the Dirac point of graphene.

Thin film ethanol sensors made from alpha-Fe2O3 decorated with multiwall carbon nanotubes (MWCNTs) were manufactured by the electron beam deposition method. The morphology of the decorated alpha-Fe2O3/MWCNTs (25:1 weight ratios) nanocomposite powder was investigated using the scanning electron microscopy and X-ray diffraction techniques. The thickness of thin films has been determined from ellipsometric measurements. The response of manufactured sensors was investigated at different temperatures of the sensor work body and concentration of gas vapors. Good response of prepared sensors to ethanol vapors already at work body temperature of 150 degrees C was shown.

The structure represents symmetrical metal electrode (gate 1) - front SiO2 layer - n-Si nanowire FET - buried SiO2 layer - metal electrode (gate 2). At the symmetrical gate voltages high conductive regions near the gate 1 - front SiO2 and gate 2 - buried SiO2 interfaces correspondingly, and low conductive region in the central region of the NW are formed. Possibilities of applications of nanosize FETs at the deep inversion and depletion as a distributed capacitance are demonstrated. Capacity density is an order to ⁄ . The charge density, it distribution and capacity value in the nanowire can be controlled by a small changes in the gate voltages. at the non-symmetrical gate voltages high conductive regions will move to corresponding interfaces and low conductive region will modulate non-symmetrically. In this case source- drain current of the FET will redistributed and change current way. This gives opportunity to investigate surface and bulk transport processes in the nanosize inversion channel.

The numerical finite difference time domain (FDTD) model of liquid crystal diffraction phase grating is developed and the possibility to use this grating for the spatial-time control of radiation in the mid IR wavelength range is shown.

In liquid crystal devices (LCDs) the indium tin oxide (ITO) films are traditionally used as transparent and conductive electrodes. However, today, due to the development of multichannel optical communication, the need for flexible LCDs and multilayer structures has grown. For this application ITO films cannot be used in principle. For this problem, graphene (an ultrathin material with unique properties, e.g., high optical transparency, chemical inertness, excellent conductivity) is an excellent candidate. In this work, the electro-optical and dynamic characteristics of a liquid crystal (LC) cell with graphene and ITO transparent conducting layers are investigated. To insure uniform thickness of the LC layer, as well as the same orientation boundary conditions, a hybrid LC cell containing graphene and ITO conductive layers has been prepared. The characteristics of LC cells with both types of conducting layers were found to be similar, indicating that graphene can be successfully used as a transparent conductive layer in LC devices.

By the method of metal-organic chemical vapor deposition we have epitaxially grown effective samples of InAs/p-GaSb/n-GaSb/n-GaAs/InxGa1−xAs/Ge/Si(113) photovoltaic cells and investigated their photoelectric properties. The suitability of application of quality heterojunction diode structures in termophotovoltaic cells is experimentally proved.

Thin film gas sensors based on nanocomposite In2O3·Ga2O3·SnO2 (70:20:10) have been manufactured by the high-frequency magnetron sputtering method. The technological cycle of sensor fabrication processes is described. Sensitivity of the prepared sensors at the temperature of working body 250°C and low-frequency noises within the 1–300 Hz range were investigated. The response of sensors to vapors of ethanol and acetone was investigated using resistive and noise methods. It is shown that the value of the sensitivity measured by the noise method exceeds the value of sensitivity measured by the resistive method. Sensors show appreciable sensitivity to the ethanol vapors already at working body temperature 150°C. Sensors can be used for the detection of low concentrations of ethanol vapors. The monotonous increase in the sensitivity of these sensors with increase in the ethanol and acetone vapors content allows applying nanosensors also for fast determination of gases concentration in air.

A modified liquid phase epitaxy was applied to grow InAsSbP quantum dots on InAs (1 0 0) substrate. Low bias and room temperature photoconductive cells with InAsSbP nanostructures were developed. In comparison with InAs based photoconductive cell, a red shift and additional peaks at 3.4 μm, 3.68 μm and 3.89 μm on photoresponse spectrum of quantum dot photoconductive cell were observed. Additionally, the spectrum dependence on bias voltage at room temperature is presented. Under irradiation of 3.39 μm, the surface resistance was reduced up to 7% at power density of 0.07 W/cm 2 . At the bias of 8 mV current responsivity of 0.2 mA/W was measured.

The InAsSbP quantum dots were grown on InAs(100) substrate by modified version of liquid phase epitaxy. The morphology, dimensions and distribution density of the quantum dots were investigated by an atomic force microscope. Two mid-infrared photodetectors made of InAs(100) substrate with and without InAsSbP quantum dots are fabricated and investigated. Current-voltage characteristics are measured and a deviation from linearity is detected for the quantum dot photodetector. Room temperature photoresponse spectra at low applied voltages are investigated. An anomalous photovoltaic effect is detected. Open circuit voltage and short circuit current generated in the quantum dot photodetector under irradiation of He-Ne laser operating at 3.39 microm are measured. Our measurements showed that voltage and current responsivities at room temperature are equal to 2 V/W and 82 mA/W, respectively. Specific dips in the quantum dot photodetector's room temperature capacitance-voltage characteristics are observed. Magnetic field up to 1.6 T was applied to measure the magnetoresistance at room temperature. Specific oscillations on magnetoresistance curve for the quantum dot photodetector are observed.

International audience; We present the results of growth of quasi-ternary InAsSbP spherical and ellipsoidal quantum dots (QDs) on InAs (100) surface by the method of liquid-phase epitaxy. Coarsening of QDs due to coalescence and Ostwald ripening was investigated by atomic-force and scanning electron microscopy. Ellipsoidal QDs prolated in [010] and oblated in [001] directions have been grown. Elongation ratios for the ellipsoidal QDs were measured in all three directions. It is shown that elongation of spherical QDs to ellipsoidal is started at QDs diameter of ∼50 nm. Shape transformation of the QDs’ size distribution function from the Gram-Charlier-like to the Gaussian and then to the Lifshits-Slezov-like distribution was revealed at increasing the nucleation time.

Gas sensors made from carbon nanotubes without their doping and functionalization have serious shortcomings. Analysis of physics and techniques of decoration (functionalization) of carbon nanotubes using organic polymers, doping with impurities, metallic nanoparticle/nanoclusters is carried out. The development of metal oxide nanocomposite sensors decorated with carbon nanotubes is very promising for realization of detectors of different important gases with dramatically improved response, better time characteristics and smaller consumed power.

Nanocomposite SnO2/multiwall-carbon-nanotubes were prepared by the sol-gel method. The morphology of prepared nanocomposite powder was investigated by scanning electron microscopy. Energy-dispersive X-ray and X-ray diffraction analyses were carried out, the element structure of a nanocomposite has been determined. Ceramic and thick film gas sensors made of the nanocomposite multiwall-carbon-nanotube/SnO2/Pd structure were manufactured and investigated. After the sensitization in the Ru(OH)Cl-3 water solution, these sensors have rather high response to isobutane already at 120 degrees C. The response of prepared sensors was measured at different gas concentrations and at different temperatures of the work body. (C) 2012 Elsevier B.V. All rights reserved.

We investigated the dependence of angular dispersion of replica on its distance from the master polarization diffraction grating (PDG). The distribution of field diffracted on master PDG was calculated using the method of finite-difference time-domain. According to the numerical model, within the transition region, conditioned by interference of secondary waves with the same polarization state, the angular dispersion of replica changes depending on the distance between master and replica. Outside the transition region, the angular dispersions of replica and master completely coincide. The experimental investigation was also carried out, the results of which are in good agreement with the calculated data.