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an innovative application of deep barrier silicon structures for sensory devices with photoelectrical transformation has been suggested. The principal possibility of the photovoltaic transducer implementation for identification of metallic and semiconductor single-wall carbon nanotubes covered with surfactant in water solution was analyzed in detail. The obtained results are qualitatively explained by local electrostatic influence on the parameters of recombination centers at the silicon surface. This influence can be associated with the dipole moment of molecules absorbed at the surface of the nanotube from surfactant sodium dodecylbenzene sulfonate (SDBS). Moreover, the spatial configuration of charged fragments near the defects at the silicon surface can occur. Another possible reason for carbon nanotubes identification is due to the different polarizability of metallic and semiconductor nanotubes. These results are explained in the frame of Stevenson-Keyes's theory. The reported effect can be further applied as the basis for the control and selection of carbon nanotubes with different conductivity types.

International audience; In the paper, combined bi-modal microscopic visualization of biological objects based on reflection-mode optical and photoacoustic measurements was presented. Gas-microphone configuration was chosen for the registration of photothermal response. Precise positioning of the scanning laser beam with modulated intensity was performed employing acousto-optic deflectors. Photoacoustic images are shown to give complementary details to the optical images obtained in the reflected light. Specifically, the photoacoustic imaging mode allows much better visualization of the features with enhanced heat localization due to the reduced heat outflow. For example, the application of the photoacoustic imaging mode was especially successful to visualize Drosophila fly's micro-hairs. Furthermore, the photoacoustic image quality was shown to be adjusted through modulation frequency.

We identified different nano-carbon species such as graphene nanoplatelets, graphite flakes and carbon nanotubes dispersed in N-methyl-2-pyrrolidone using a novel sensor structure based on a “deep” silicon barrier working as a photoelectrical transducer. Each nano-carbon particle has specific signature in both 2D photocurrent distribution and photocurrent dependencies on bias changing surface band-bending. Additionally, all nano-carbon particles have characteristic features in the time-dependent evolution of photocurrent. The obtained results can be explained by the influence of nano-carbon molecules' local electric field on the recombination parameters of defect centers on the silicon surface.

The possibility of application of silicon wafer surface treatment by iron (III) chloride solution as the instrument to determine charge carriers’ lifetime is investigated. The measured lifetimes demonstrated essential growth with increase of Fe3+ ions concentration. The observed effect can be further applied as the basis for heterogeneous chemical passivation of sensor array system on a single silicon wafer.

A capability to produce effective sensor structures on the basis of “deep”silicon junction has been substantiated. If the incident light is strongly absorbed by this junction, the photocurrent through it is shown to substantially depend on the recombination characteristics and the charge state of the illuminated surface, provided that the junction parameters are optimal. The depth of the illuminated region is demonstrated to exceed the diffusion length of minority charge carriers. It is found that the larger diffusion length of minority charge carriers corresponds to stronger changes of the photocurrent generated by the illuminated surface area. A possibility to transform the junction from a photodetector into an effective chemical sensor is verified by numerical calculations. The physical mechanisms relating the changes in the effective surface recombination rate and the absorption of polar molecules are discussed. The sensor properties of suggested silicon junctions are analyzed for a number of analytes. Their suitability for the creation of selective chemical sensors (electronic noses) is demonstrated experimentally., В роботi обґрунтовано можливiсть використання кремнiєвого переходу для ефективних сенсорних структур. Показано, що в умовах опромiнення свiтлом з областi сильного поглинання фотострум суттєво залежить вiд рекомбiнацiйних характеристик та зарядового стану поверхнi у випадку оптимальних параметрiв переходу. Визначено, що товщина освiтлюваної областi для такої структури повинна перевищувати довжину дифузiї неосновних носiїв заряду. Визначено також, що бiльшiй довжинi дифузiї вiдповiдають бiльшi змiни фотоструму при адсорбцiї на робочiй поверхнi. З використанням числового моделювання проаналiзовано можливiсть змiни областi застосування переходу вiд фотоперетворювача до сенсорної структури при певному виборi його параметрiв. Обговорено фiзичнi механiзми, якi можуть пов’язувати змiни ефективної швидкостi iз процесами адсорбцiї полярних молекул. Cенсорнi властивостi запропонованих структур дослiджено для декiлькох аналiтiв. Експериментально продемонстровано придатнiсть такої структури для створення хiмiчних сенсорiв, якi мають функцiю селективностi та пiдтримують концепцiю електронного носу.

A concept of new photovoltaic transducer, combining properties of planar p–n solar cell and light-addressable potentiometric sensor (LAPS) is considered for chemical sensor application. The proposed photovoltaic transducer operation principle based on change of surface recombination velocity during gas adsorption. As compared with typical LAPS, the considered sensor has no reference electrode, it is not necessary to apply DC bias voltage and such sensor is applicable not only for liquid but for gas detection also. The influence of p–n junction depth, doping level, diffusion length on photocurrent of planar silicon junction for different value of surface recombination is studied by numerical simulation. It allows optimizing the junction parameters from point of view of its efficient application as a chemical sensor with photovoltaic transducer. The proposed chemical sensor concept was verified by LBIC method on modified industrial solar cell.

The MIS-type humidity sensor and alcohol — meter based on metal-organic layer-porous silicon (PS) — silicon were elaborated. The influence of the adsorption of ethanol /water mixture on conductivity and capacity voltage (C-V) characteristics was analyzed theoretically and investigated experimentally. The highest response is reached at about 40% concentration of ethanol in water. Such a form of the dependence can be explained by the fact that the adsorption of ethanol and water vapors influences the PS in different ways. The adsorption of donor-type water molecules on the PS surface results in an increase of the conductivity due to the injection of free electrons. The adsorbed on the PS surface the ethanol molecules, on the one hand, prevent the water molecules adsorption and, on the other hand, change the surface recombination rate. The MIS structures with complex dielectric interface (PS + organic layer) show the increased response to the presence of water and ethanol in comparison with structures of metal-PS-Si. To estimate the effect of pores filling/empting on sensors response/recovery time the test PS Bragg mirror was formed and time-depended reflectivity during the adsorption/desorption process was measured.

Impedance and optical properties of pressed composites based on microcrystalline and nanoporous silicon powders were studied. Porous silicon crystallites were obtained by stain etching of initial microcrystalline silicon powder. Oxygen passivation of the surface during porous-powder formation provided stability of composite characteristics. An analysis of experimental dependences of the impedance in a frequency range of 1–106 Hz allowed separation of contributions of grain bulk and crystallite interfaces to the total composite conductivity. The results of the study of the time dependences of the impedance were used to determine the variation rates of electrical parameters of composite structures under dynamic adsorption-desorption influence of external reactants (H2O and C2H5OH).

Hydrogen reservoirs based on porous silicon (PS) nanostructures are considered. Silicon-based hydrogen tanks are believed to be applicable for portable device energy supply and compatible with micro-sources of energy of new generation. Stain etching of silicon powder to produce PS is studied as a technology alternative to conventional electrochemical etching and application of the PS powder for hydrogen production is also described. Size selection of initial Si micro-particles constituting the powders was carried out by sedimentation technique. Hydrogen content in PS was investigated by FTIR spectroscopy. Extraction of hydrogen in water environment in presence of small amount of NH3 as catalyst was shown to have advantages such as safety and tunability, additional production of hydrogen from water dissociation, and a possibility to characterize PS as a hydrogen source material in terms of hydrogen effective shell and crystalline core conception.

Stretching of the m. triceps surae (TS) of decerebrated cats evokes reflex shifts of the membrane potential (MP) in spinal motoneurons resulting from summation of EPSPs. We carried out model analysis of summation of a great number of EPSPs and compared the respective results with changes in the MP observed in real experiments using intrasomatic microelectrode recording. Simulation was based on the supposition of the proximity of the time course of an excitatory postsynaptic current to the positive part of the EPSP derivative. Transformation of EPSPs was performed using low-frequency filtration with two values of the time constant, 7 and 20 msec, (models M1 and M2, respectively). The models obtained provided sufficiently adequate reflection of the ascending phase of the real EPSP but inadequately reflected the rate of its decline and slow components of the MP changes. The disagreement of simulations with the real MP shifts shows that, most probably, final postsynaptic effects are to a considerable extent provided by summation of a great number of EPSPs generated in distal dendrites, and EPSPs immediately recorded in trasomatically cannot provide one with adequate information on the entire pattern of natural synaptic activation of the neuron. In addition, simulation analysis demonstrated a high probability of the contribution of active inhibitory processes to the formation of resulting MP changes under conditions of the stretch reflex.

International audience; The electronic tongue based on the array of low selective photovoltaic (PV) sensors and principal component analysis is proposed for detection of various alcohol solutions. A sensor array is created at the forming of p-n junction on silicon wafer with porous silicon layer on the opposite side. A dynamical set of sensors is formed due to the inhomogeneous distribution of the surface recombination rate at this porous silicon side. The sensitive to molecular adsorption photocurrent is induced at the scanning of this side by laser beam. Water, ethanol, iso-propanol, and their mixtures were selected for testing. It is shown that the use of the random dispersion of surface recombination rates on different spots of the rear side of p-n junction and principal component analysis of PV signals allows identifying mentioned liquid substances and their mixtures.

In this paper we analyse the passivation of the front surface of p-Si interdigitated rear contacts solar cell (IBC) by a thin porous silicon (PS) layer. Effectively, an efficiency improvement of 87% in relative was observed after porous silicon layer formation on the front surface of the IBC cell. The origin of surface passivation by the PS layer was studied by Laser Beam Induced Current (LBIC) method. The front surface of rear contacts cell with thin porous silicon layer was scanned by a modulated red laser beam in presence of a permanent light with different wavelengths and intensities. It was shown that without permanent illumination, the photocurrent of the cell with PS layer is very low, even lower than for a cell with unpassivated surface. However with short permanent wavelength illumination a strong increase of photocurrent was observed (8–10 times!). The light-dependent porous silicon passivation phenomenon is explained by a significant negative charge accumulation at the PS/p-Si interface traps under illumination. This leads to the formation of a hi-low (p + /p) junction at the front surface of the cell and to the reduction of the front surface recombination rate, like in Front Surface Field Solar Cell.

The possibility of surface recombination losses reduction on the rear side of interdigitated back-contact solar cells by field-effect passivation is investigated. To provide field-effect passivation, an additional biased metal/insulator/semiconductor (MIS) structure is formed between n ++ and p + -doped regions. The source of the bias is the potential that appears in the solar cell under illumination. Two-dimensional (2D) numerical simulations were performed to determine the best passivation conditions. In particular, the influence of symmetric and asymmetric capture cross sections for electrons and holes at the rear side of the cell is simulated and the advantage of symmetric capture cross section for this type of passivation is discussed. Experimental and calculated data are compared for Si/SiO 2 interface.

The distributed properties of solar cell emitters and p–n junctions such as sheet resistance, local potential and shunt resistance were studied by original methods based on the laser scanning technique. To study the shunt resistance defects the dynamical optical reflectance thermography technique has been developed thanks to new possibilities of signal treatment and 2D scanning. The experimental factors that influence on PV LBIC-like signal are analyzed. It is shown that the information about the local potential and sheet resistance distribution is contained in the LBIC-like signal measured in the galvanostatic circuit and extracted by comparison of the signal distributions obtained under different applied voltage and laser beam parameters. The samples of the mapping of the resistive properties are presented for multicrystalline silicon solar cells without and with selective porous silicon antireflection coating.

A novel technique named Dynamical Optical Reflection Thermography (DORT) able to detect the dark current inhomogeneities in semiconductor devices such as solar cells, have been proposed. It is based on the principles of dynamical heating of defect dots by the pulse dark current and registration of the temperature alteration by the measurement of the external reflection from the semiconductor surface. Lock-in technique and statistical evaluation of the modulated reflectance data were used to improve the method sensitivity. A temperature waves process is proved to be a reason of reflectance modulation under impulse current applied to the tested solar cells. Spatial distributions for the DORT signal were obtained.

International audience; An electronic tongue concept based on 2D mapping of photogenerated charge carrier lifetimes in silicon put in contact with different liquids is reported. Such method based on intrinsic sensitivity of the silicon surface states to the surrounding studied liquids allows creation of their characteristic electronic fingerprints. To increase recognition reliability, a set of characteristic fingerprints for a given liquid/silicon interface is proposed to be recorded at different bias voltages. The applicative potential of our sensing concept was demonstrated for different spirits and water samples.

We have developed a method for synthesis of N-(3-clzloro-2-quinoxalyl)sulfonamides by reaction of 2,3-dichloroquinoxaline with substituted arylsufonamides. Based on the IR spectra, we have established that in the solid state, the synthesized compounds exist in the form of amide tautomers. Alkylation of these compounds leads to N-metliyl-N-(3-chloro-2-quinoxalyl)arylsulfonamides. We demonstrate the possibility of nucleophilic substitution of the halogen upon treatment with O- and N-nucleophiles. The use of bifunctional nucleophiles leads to condensed quinoxalines.

The interaction of α-substituted 2-(3-chloro)quinoxalylacetonitriles with azines to give condensed indolizino [2,3-b]quinoxalines has been studied. A mechanism for the reaction has been proposed which includes an intramolecular vicarious substitution of hydrogen in the azolium salt nucleus. The limits of utility of the reaction have been determined and some chemical properties of the compounds synthesized have been studied.

The reaction of α-substituted 2-quinoxalylacetonitriles with 1-alkyl(aryl)imidazoles, -benzimidazoles, -1,2,4-triazoles and 5,6-dihydroimidazo[i,j]quinoline was studied. It was found that during the course of the reaction an unusually easy dealkylation of the azole ring takes place, while the aryl substituent is not split off. A reaction mechanism has been proposed including the formation of an ylide intermediate, followed by subsequent electrophilic attack on the C(2) position of the azolium ring. The applicability boundaries of the reaction studied and the spectral characteristics of the synthesized compounds were investigated.

Theoretical model of how LBIC signal from p-n junction being scanned by two laser beams is formed was proposed. Physical effects which make impact in overall phase of the LBIC signal were pointed out. Experimental research of illuminating surface of laser diode was conducted. Experimental dependencies of the phase of LBIC signal on the coordinate of scanning laser beams were obtained. Possibilities of how differential-phase method can be used to inspect semiconductor surfaces with p-n junctions were analyzed.

A new method for the synthesis of pseudo-cross-conjugated mesomeric betainic heterocyclic compounds with an angular nitrogen atom has been developed consisting in the reaction of 1,4-dielectrophile — α-carbethoxy-2-(3-chloro)quinoxalylacetonitrile with azoles. Experimental regularities have been studied and a reaction mechanism has been proposed including the stage of formation of an ylide from a quaternary azolium salt. A pseudo-crossconjugated mesomeric betainic heterocyclic compound containing a thiazole ring compound has been synthesized for the first time.

An x-ray crystallographic investigation of 3-methyl-5-cyanoimidazolio[1′,2′∶1,6]pyrido[2,3 -b]quinoxalin-4-olate, which is a representative of a previously unknown type of polynuclear heterocyclic pseudo-crossconjugated mesomeric betaine, was undertaken.

A study was carried out on the reaction of 2,3-dichloropyrazine with compounds containing an activated methylene group. The reaction course and structure of the final products are a function of the nucleophile.

A comparative study is performed of Schottky barrier structures based on Si and GaAs as photoelements and detectors of electrons with energies of 40 and 60 keV. It is shown that introduction of a dielectric interlayer between the metal and semiconductor 1.5–3 nm thick permits increase in ic and Vx of the structures in both the photodetector and electron count regimes. A complex temperature dependence of structure properties in the electron count regime was found, depending on barrier metal thickness and electron energy.

Advanced scanning technique on the base of laser microscope and evaluation of the induced photovoltaic (PV) signal is discussed. It is able to obtain non-destructively the 2D distribution of the several important parameters of semiconductor PV devices such as surface potential, sheet resistance, efficiency and losses of energy conversion, nanosize deviations of their layers.

A theoretical analysis is performed herein of the spectrum sensitivity of a solar cell with a metal-tunnel dielectric-semiconductor structure on the properties of the interfacial boundaries and conditions for maximal collection of charge by the photocarriers are determined. The photosensitivity of structures with different tunnel-dielectric thickness is measured experimentally in a broad spectrum range. Comparison of the computed and experimental dependences permitted proving the influence of departure of the majority charge carriers in the metal on the photosensitivity in the shortwave spectrum band and also determining certain contact parameters governing the structure photosensitivity, and therefore, the efficiency of the solar cells.

Recently, porous silicon has demonstrated the attractive physical properties which offer a potential to design antireflection coatings for solar cells [1,2,3], light emitting diodes [4], for generating of metal impurities [5], as electro- and thermoinsulating material and other applications. It is also considered a material for gas sensors due to its adsorptional ability, strong dependence of luminescence, and conductivity on the gas ambient. In spite of such advantages of the material, it has not yet been applied widely for the gas sensing perhaps because the nature of the adsorption mechanisms has not been studied enough.

The paper presents a comparative assessment of the quality characteristics of computers available at the market for X-ray image visualization by using by the generally accepted criteria and gives recommendations for choosing these means for completing X-ray fluorographic complexes.

We have designed a series of original techniques able to obtain non-destructively the 2D distribution of the several important parameters. Laser scanning of dynamically loaded solar cell has been shown to give a distribution of the dark current density since this value determines the local heat power and the reflectivity of the cell surface. An additional positive voltage bias at local laser irradiation and typical working conditions applies to the solar cell due to the concentration of current lines within the illuminated spot and due to the voltage drop depending of the local emitter resistivity. Quantitative comparison of the resistance sensitive photocurrent distribution and such distribution in the resistance independent conditions gives an information about local resistivity. The analysis of LBIC signal obtained from the whole battery at the different bias voltage and illumination conditions has shown to investigate the contribution of each cell to the total efficiency and the energy losses, switching to the output contacts ofthe battery only. This approach makes it possible to monitor the cell characteristics in encapsulated modules directly in loading conditions and without their destruction.

Laser beam scanning was applied for evaluating the distribution of sheet resistance of solar cell emitter. It was shown that the voltage drop around the illuminated spot has an information about the local sheet resistance since the most part of the voltage drop occurs near the illuminated area. The current under local illumination in reverse direction depends on the local quantum efficiency while in forward direction it depends on the same local properties and on the local sheet resistance. The processing of laser beam induced current images at different bias voltage gives a map of local sheet resistance complementing other techniques for investigation the electron devices. We investigated one and dual-beam technique for amplitude and phase LBIC measurement by means of universal laser scanning microscope worked in amplitude and differential-phase regimes. Acousto-optical scanning results in 2D distribution of amplitude or phase LBIC. For convenience of image processing and visualization, TV type scanning is applied to laser beams.

A series of alpha-sulfonyl-2-(3-chloro)hetarylacetonitriles was prepared by the interaction of dichlorodiazines and R-sulfonylacetonitriles. Reaction of nucleophilic substitution of chlorine by different N-H-azoles has been studied. The compounds obtained showed 3 types of activity on cardiac papillary muscles: 1. a biphasic activity with increase in cardiac contractility at low concentration and inhibition in high concentration (1, 2, 4, 12-15), 2. a monophasic inhibitory activity (3, 5, 8-10), 3. non-active compounds (6, 7, 11). The preliminary SAR studies indicate the importance of chlorine atom at position 3 in diazine nucleus and of alkyl substituents in benzimidazole moiety for positive inotropic effects.

The paper contains the results of the research of the mechanism of "shuttle" self-discharge determined by the manganese and titanium ions in the electrolyte of a PbO 2 |H 2 SO 4 |C heterogeneous electrochemical supercapacitor (HES). Research was made with respect to the effect of the shuttle self-discharge determined by the manganese and titanium ions on the energy, capacity parameters, and the charge and discharge voltage of HESs. Using the methods of the research of the energy, capacity parameters, self-discharge of the capacitors, and optical spectra of their electrolytes, it was established that, in the process of the shuttle, self-discharge of the capacitors with the electrolytes containing manganese and titanium, mostly MnO - 4 , Mn 2+ and Ti 3+ and TiO 2+ ions, respectively, is involved. It is shown that the shuttle self-discharge determined by the manganese ions brings about the self-discharge of an HES down to the minimal allowable voltage, and the titanium ions to the voltage of 1.62 V. It was established experimentally that the self-discharge current and the power of energy losses during the self-discharge related to the manganese ions in the electrolyte depend nonlinearly on the concentration of the manganese ions. When the concentrations of iron, titanium, and manganese are identical in the electrolyte of HES, the value of the capacitors' self-discharge decreases during the transition from the iron to the manganese. In the spectra of the optical density of HESs electrolyte containing manganese and titanium in the wave band of 200-1100 nm, absorption bands are discovered which are related to the ions of the manganese, titanium, and the level of the capacitors' state of charge. During the charge and discharge of an HES with the electrolyte which contains the titanium, Ti 2+ ions whose concentration is substantially lower than the concentration of Ti 3+ ions are also formed in the electrolyte.

This work contains the results of research on the mechanism of the shuttle self-discharge determined by Fe 2+ and Fe 3+ ions in the electrolyte of a heterogeneous electrochemical supercapacitor (HES) of a PbO 2 |H 2 SO 4 |C system, as well as the results of the measurements of the effect of the shuttle self-discharge current on the energy, capacity, and operation parameters of HES capacitors. It is shown that the presence of the iron ions in the electrolyte of a HES capacitor brings about shuttle self-discharge, which continues until the voltage decreases to the value of 1.05 V. The shuttle mechanism is related to oxidation and reduction of Fe 2+ and Fe 3+ ions in the positive and negative electrodes, respectively. An analytical expression is obtained for the calculations of the shuttle self-discharge current determined by different types of impurity ions in the electrolyte of HES capacitors. Analysis is made with respect to the obtained experimental and theoretical data of the self-discharge current, energy, and capacity parameters, as well as their dependence on the concentration of iron ions in the electrolyte, the separator's thickness, and modes of the capacitors' charge. It is established that the processes of oxidation and reduction of iron ions take place in the near-surface layers of the capacitor electrodes. It is shown that the linear increase of the separator thickness does not bring about any linear decrease of the shuttle self-discharge current determined by Fe 2+ and Fe 3+ ions.

A mathematical model of heterogeneous electrochemical supercapacitors (HES) is proposed which makes it possible to develop capacitors with optimal designs and make calculations of their energy, capacity, and power parameters. Special attention is paid to the processes which occur in electrodes with double electric layer (DEL) of HES capacitors during their charge and discharge by different currents. It is demonstrated theoretically that in the efficiency of HES capacitors' operation, an important role is played by distribution of the potential along the thickness of electrodes with DEL. In order to build capacitors with improved parameters and optimal design, it is of paramount importance to take account of the type and value of conductivity of the material of the electrode with DEL and conductivity of the electrolyte in its pores. Analysis is performed to determine the efficiency of PbO 2 |H 2 SO 4 |C system capacitors' operation subject to thickness, conductivity, and specific capacitance of the electrode with DEL. It is established that energy and capacity parameters of the capacitors depend to a great extent on conductivity of their negative electrodes and electrolytes. It is demonstrated that there are different mechanisms of losses of energy and charge of the capacitors during their charge, discharge, and storage.

Comparative studies, by the method of IR spectroscopy, of the reflection-absorption properties of oxide layers and the electrophysical characteristics of Ti-SiOx-Si contacts were performed. It is shown that electron-beam deposition of Ti on a heated SiOx-Si substrate gives a thinner layer of silicon oxide and leads to the formation of titanium oxide at the interface. The changes observed, based on the IR spectra, in the properties of the oxide layers as a function of the substrate temperature and the method of oxidation permit drawing conclusions regarding the predominant mechanisms for the passage of majority and minority charge carriers in the contact.

The problem of silicon substrate selection for the sensor structure based on deep junction barrier has been investigated. The described sensor is functioning on photoelectrical conversion principle for the illumination with has high absorption coefficient in the silicon. The method of substrate pre-selection with the measurement of capacitance-voltage characteristics has been suggested. As shape of the capacitance-voltage curves in the system liquid analyte/silicon substrate (with or without chemically modified silicon surface) highly depends on charge state of the interface and near-surface band bending, some recommendation for silicon substrate choosing can be used. The obtained results indicate that the shift of the saturation voltage of the capacitance-voltage curves correlates with peculiarities of photocurrent distribution in the deep silicon barrier structure. Based on the results of the research the effective recombination sensors with reproducible characteristics can be fabricated.