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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.

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.