We report the growth of thin aluminum films on SiON layers by means of magnetron sputtering in the kinetically limited regime. The morphology and electrical resistance of the films were investigated as a function of the deposition time in continuous or multistep film deposition modes. It was found that the aluminum film growth on SiON layers proceeds by the Stranski-Krastanov mechanism. There is the time interval t(w), when the formation of films with columnar Al grain clusters and pores/pits up to 60 nm in size is observed. For the multistep mode, the smaller the Al deposition step is, the more the t(w) value and the longer the film retains its surface morphology. The optical properties of multilayer Al/SiON stacks with a thickness up to 320 nm show the absorption up to similar to 82 % in the range of 1.2-4.2 mu m and the absorption band broadening as the number of layers increases. The Al/SiON stacks show their long-term and thermal stability at the temperature of 200 degrees C.

The title compound was synthesized by Ullmann cross-coupling in low yield as the first representative of [n]phenylene containing hydrocarbon and fluorocarbon rings. Stille/Suzuki-Miyaura cross-coupling reactions, as well as substitution of fluorine in suitable starting compounds, failed to give the same product. The geometric and electronic structures of the title compound were studied by X-ray diffraction, cyclic voltammetry and density functional theory calculations, together with Hirshfeld surface and reduced density gradient analyses. The crystal structure features head-to-tail π-stacking and other fluorine-related secondary bonding interactions. From the nucleus-independent chemical shifts descriptor, the four-membered ring of the title compound is antiaromatic, and the six-membered rings are aromatic. The Janus molecule is highly polarized; and the six-membered fluoro- and hydrocarbon rings are Lewis π-acidic and π-basic, respectively. The electrochemically-generated radical cation of the title compound is long-lived as characterized by electron paramagnetic resonance, whereas the radical anion is unstable in solution. The title compound reveals electrical properties of an insulator. On expanding its molecular scaffold towards partially fluorinated [n]phenylenes (n≥2), the properties presumably can be transformed into those of semiconductors. In this context, the title compound is suggested as a prototype scaffold for ambipolar materials for organic electronics and spintronics.

Nanowire or nanobelt sensors based on silicon-on-insulator field-effect transistors (SOI-FETs) are one of the leading directions of label-free biosensors. An essential issue in this device construction type is obtaining reproducible results from electrochemical measurements. It is affected by many factors, including the measuring solution and the design parameters of the sensor. The biosensor surface should be charged minimally for the highest sensitivity and maximum effect from interaction with other charged molecules. Therefore, the pH value should be chosen so that the surface has a minimum charge. Here, we studied the SOI-FET sensor containing 12 nanobelt elements concatenated on a single substrate. Two types of sensing elements of similar design and different widths (0.2 or 3 μm) were located in the chips. The drain-gate measurements of wires with a width of 3 µm are sufficiently reproducible for the entire chip to obtain measurement statistics in air and deionized water. For the pH values from 3 to 12, we found significant changes in source-drain characteristics of nanobelts, which reach the plateau at pH values of 7 and higher. High pH sensitivity (ca. 1500 and 970 mV/pH) was observed in sensors of 3 μm and 0.2 μm in width in the range of pH values from 3 to 7. We found a higher “on” current to “off” current ratio for wide wires. At all studied pH values, Ion/Ioff was up to 4600 and 30,800 for 0.2 and 3 μm wires, respectively. In the scheme on the source-drain current measurements at fixed gate voltages, the highest sensitivity to the pH changes reaches a gate voltage of 13 and 19 V for 0.2 μm and 3 μm sensors, respectively. In summary, the most suitable is 3 μm nanobelt sensing elements for the reliable analysis of biomolecules and measurements at pH over 7.

Dielectrophoresis (the phenomenon in which particles in fluid polarize and move in response to spatial variations of an electric field) is an attractive tool for address analyte delivery to a sensor element. One of the key factors that determine the bioparticle movement under dielectrophoretic (DEP) forces is the gradient of the electric field square. In this study, the distribution of the electric field strength square gradient for SOI (silicon-on-insulator) FET (field effect transistor) sensors with DEP control was analyzed to optimize the design of sensor with dielectrophoretic delivery of target particles. The distribution of the electric field strength gradient for sensors was investigated as a function of a) the distance between the sensor element and DEP-electrodes, b) the sensor operation mode, and c) the voltage at DEP electrodes using TCAD modeling. Results showed that for the address delivery of target particles to the sensors, the following conditions are preferable: negative dielectrophoresis, subthreshold sensor mode, and distance to the DEP-electrode less than 1.2 µm.

The condition of the same distribution of free carriers in thin films is necessary for comparing the mobility and analyzing the scattering mechanisms of carriers near semiconductor film/insulator interfaces. In thin film/insulator systems with different design parameters, it is difficult to ensure the same distribution of free carriers due to physical phenomenon such as the coupling effect. In this study, TCAD simulations of thin-film transistors, which have been used to monitor Si film properties, were applied to find parameters that allow tuning the potential distribution and, accordingly, the distribution of free carriers in films. It was found that such parameters are the film regime, the density of induced carriers, the gate voltage or threshold voltage of transistors. The conditions for the selection of parameters were found that ensure the same distribution of free carriers in thin-film structures for the cases of different thicknesses of films and the surrounding dielectrics. It was shown that the proposed approach can be used for a comparative analysis of the mobility in thin films and makes it possible to eliminate errors associated with different distributions of carriers in the films due to the coupling effect.

Silicon-on-insulator (SOI) nanowire or nanoribbon field-effect transistor (FET) biosensors are versatile platforms of electronic detectors for the real-time, label-free, and highly sensitive detection of a wide range of bioparticles. At a low analyte concentration in samples, the target particle diffusion transport to sensor elements is one of the main limitations in their detection. The dielectrophoretic (DEP) manipulation of bioparticles is one of the most successful techniques to overcome this limitation. In this study, TCAD modeling was used to analyze the distribution of the gradient of the electric fields E for the SOI-FET sensors with embedded DEP electrodes to optimize the conditions of the dielectrophoretic delivery of the analyte. Cases with asymmetrical and symmetrical rectangular electrodes with different heights, widths, and distances to the sensor, and with different sensor operation modes were considered. The results showed that the grad E-2 factor, which determines the DEP force and affects the bioparticle movement, strongly depended on the position of the DEP electrodes and the sensor operation point. The sensor operation point allows one to change the bioparticle movement direction and, as a result, change the efficiency of the delivery of the target particles to the sensor.

Quick label-free virus screening and highly sensitive analytical tools/techniques are becoming extremely important in a pandemic. In this study, we developed a biosensing device based on the silicon nanoribbon multichannel and dielectrophoretic controlled sensors functionalized with SARS-CoV-2 spike antibodies for the use as a platform for the detection and studding of properties of viruses and their protein components. Replicatively defective viral particles based on vesicular stomatitis viruses and HIV-1 were used as carrier molecules to deliver the target SARS-CoV-2 spike S-proteins to sensory elements. It was shown that fully CMOS-compatible nanoribbon sensors have the subattomolar sensitivity and dynamic range of 4 orders. Specific interaction between S-proteins and antibodies leads to the accumulation of the negative charge on the sensor surface. Nonspecific interactions of the viral particles lead to the positive charge accumulation. It was shown that dielectrophoretic controlled sensors allow to estimate the effective charge of the single virus at the sensor surface and separate it from the charge associated with the binding of target proteins with the sensor surface.

In thin films, we deal with such a physical phenomenon as the coupling-effect. In this study, this effect was used to redistribute charge carriers in silicon-on-insulator thin films to determine the effective mobility near the interface under study. Temperature dependences of mobility were applied to experimental results to extract components of effective mobility related to phonon and interface roughness scattering of the carriers. These components are more suitable to show differences in the interface quality of films than values of effective mobility. The suggested approach can be used for the non-destructive analysis of interface quality in films.

The analysis of nucleic acids remains to be a topical trend in the development of medical diagnostics. Contemporary ultrasensitive diagnostic systems provide the conversion of a specific interaction into a hardwarely-detectable signal in the course of analysis. An example of such diagnostic devices is silicon-on-insulator (SOI) biosensors of field-effect transistors (FET). In this study, glass surfaces are used (as a Si/SiO2 surface for a SOI biosensor) for the optimization and validation of all analysis stages. The efficient immobilization of electroneutral analogs of oligonucleides onto a Si/SiO2 surface after the activation of Si-OH groups with 3-glycidoxypropyltrimethoxysilane or carbonyldiimidazole is demonstrated. In the presence of salt at a low concentration or with no salt, the possibility of detecting an RNA target on model glass surfaces in the parallel analysis regime is shown. The regeneration of the Si/SiO2 surface of sensors for repeated analysis and the stability of sensors under long-term storage are also demonstrated.

The results of identifying the vaccinia virus with the use of nanowire biosensors manufactured on the basis of silicon-on-insulator (SOI) films were presented. In our experiments, the vaccinia virus, the LIVP strain from the collection of the State Research Center of Virology and Biotechnology VECTOR of the Federal Service for Surveillance on Consumer Rights Protection and Human Wellbeing, and the rabbit blood serum containing specific polyclonal antibodies to the vaccinia virus were used. As shown by our studies, the polyvalent blood serum was electrically neutral at the sensor surface–viral suspension phase interface, the vaccinia virus was positively charged, and polyvalent blood serum–vaccinia virus vaccine complexes had a negative effective charge.

The recent outbreak of coronavirus disease caused by the respiratory syndrome coronavirus 2 (SARS-CoV-2) has highlighted the urgent need to develop fast and highly sensitive analytical tools and diagnostic devices to detect and study of the fundamental properties viruses and their nucleic acid and protein components [1]. Silicon-on-insulator field-effect transistors (SOI-FETs) based sensors provide the versatile platform for direct detection of biological species as excellent electrical signal converters. These devices have demonstrated applications for label-free, ultra-sensitive, and selective real-time detection of a wide range of biological species, including nucleic acids, proteins and viruses in either single-element or multiplexed formats [2-5]. Dielectrophoresis (DEP) and electro-hydrodynamic techniques are well known as the methods of selection and delivery of analytes to overcome limitations of diffusive transport to sensor elements without additional processing or labeling steps [6]. The aim of this study was to investigate the features of the behavior of the viruses when they are indicated by SOI-FET sensors with DEF-control. For this, SOI-FET sensors with lateral DEP-electrodes and multichannel sensors, for comparison, were used. Top-down technology with using optical lithography was applied for sensor fabrication. Devices manufacturing details are described elsewhere [3]. As an analyte, we used nuclear polyhedrosis viruses (NPVs), coronavirus virus-like particles (CVP) and suspension of specific antibodies to the virus created in the Federal research center of Virology and biotechnology "Vector" of Rospotrebnadzor. The results showed that the sensors used in the study provide the subatomolar level of virus detection. DEP-concentration of viruses increase the response of the sensors by factors of 2 to 9 (compared to the response of sensors without DEP control) and allows the false positives can be eliminated. NPVs lose their mobility with prolonged exposure to an alternating field in the sub-MHz range. The DEP-concentration of CVP leads to the formation of crystal-like structures (Fig.1). This study was supported by grant no. 18-29-02091 of the Russian Foundation for Basic Research. Sample preparation of biological materials was done within the framework of the State Task of Rospotrebnadzor. Referencies: WHO Director-General's opening remarks at the media briefing on COVID-19 – 23 April 2021 23 апреля 2021 г.https://www.who.int/director-general/speeches/detail/who-director-general-s-opening-remarks-at-the-media-briefing-on-covid-19-23-april-2021. Patolsky F., Zheng G., Hayden O., Lakadamyali M., Zhuang X., Lieber C. M. Electrical detection of single viruses // Proc. Natl. Acad. Sci. 2004, v. 101. p. 14017-14022. O. V. Naumova, V. M. Generalov, E. G. Zaitseva, A. V. Latyshev, A. L. Aseev, S. A. Pyankov, I. V. Kolosov, G. G. Ananko, A. P. Agafonov, E. V. Gavrilova, R. A. Maksyutov, and A. S. Safatov. Biosensors Based on Soi Nanowire Transistors for Biomedicine and Virusology. Russian Microelectronics, 2021, v. 50, N3, p. 137–145. Ivanov Y.D., Pleshakova T.O., Kozlov A.F., Malsagova K.A., Krohin N.V., Shumyantseva V.V., Shumov I.D., Popov V.P., Naumova O.V., Fomin B.I., Nasimov D.A., Aseev A.L., Archakov A.I. SOI nanowire for the high-sensitive detection of HBsAg and a-fetoprotein. Lab Chip. 2012, v. 12, p. 5104-5111. Dmitrienko E., Naumova O., Fomin B., Kupryushkin M., Volkova A., Amirkhanov N., Semenov D., Pyshnaya I., Pyshnyi D. Surface modification of SOI FET sensors for label-free and specific detection of short RNA analyte. Nanomedicine 2016, v. 11, N 16, p. 2073-2082. Lee S., Roh S.M., Lee E., Park Y., Lee B.C., Kwon Y., Kim H.J., Kim J. Applications of converged various forces for detection of biomolecules and novelty of dielectrophoretic force in the applications(Review). Sensors, 2020, v.20, p.3242. Fig.1 – Optical image of sensor with lateral DEP electrodes after CVP detection. In the left - CVP organized in crystal-like structures under DEP-concentration, in the right (green dots on dark field) - viruses with luminescent labels. S - source, D - drain. G1, G2 - lateral DEP electrodes. Figure 1

This article contains the results of research on the topical problem of highly sensitive express registration of biological objects using field-effect transistors with the surface open for analyte access, which are made based on silicon-on-insulator (SOI) films. The possibilities of dielectrophoretic effects for controlling the concentration of the analyte in the area of sensory elements are considered on the example of the indication of viruses of nuclear polyhedrosis and vaccinia. It is shown that the use of the dielectrophoresis (DEPh) effect makes it possible to solve (1) the key tasks for creating sensor systems: increasing the detecting ability, as well as exrtacting and verifying the signal from the target particles; and (2) the fundamental task: determining the charge state of the analyte in solutions without modifying the sensors’ surface. The problems and prospects of the mass application of nanowire (NW) biosensors, including those with the dielectrophoretic effect, in biotechnology, virology, etc., are discussed.

Работа посвящена исследованию распределения потенциалов в системах сенсор - электролит с управлением концентрацией аналита переменным электрическим полем и исследованию особенностей поведения аналита в таких устройствах.

The presented results indicate virus-like particles of the coronavirus (CVP) using a nanowire (NW) biosensor based on silicon-on-insulator technology. In the experiment, we used suspensions of CVP and of specific antibodies to the virus. Measurements of the current value of the field-effect transistor before and after the introduction of the CVP on the surface of the nanowire were performed. Results showed antibody + CVP complexes on the phase section with the surface of the nanowire modulate the current of the field-effect transistor; CVP has an electrically positive charge on the phase section "nanowire surface-viral suspension»; antibody + CVP complexes have an electrically negative charge on the phase section "nanowire surface-viral suspension"; the sensitivity of the biosensor is made up of 10−18 M; the time display was 200–300 s.

Abstract A new type of surface modification of multichannel sensors on a silicon-on-insulator base, which includes the use of a carbonyldiimidazole bifunctional reagent for the formation of an interfacial layer instead of modified silanes and probes for the specific detection of fragments of matrix troponin ribonucleic acid (analyte) as a marker of the cardiac infarction, is proposed. The influence of passivating the sensor surface activated by carbonyldiimidazole with glycine and aminoethanol at the final modification state on the response of sensors and the level of the background signal is investigated. It is shown that the proposed type of surface modification with glycine treatment provides a highly specific response of ~60% in the case of a picomolar analyte concentration in the solution. Different mechanisms are responsible for an increase in the response and sensor specificity during analyte detection after passivation by glycine and aminoethanol.

This study aims to development of basic elements of silicon biosensors with an analyte concentration by an alternating electric field and investigate the behavior of viruses in devices.

A new type of surface modification of multichannel sensors on a silicon-on-insulator base, which includes the use of a carbonyldiimidazole bifunctional reagent for the formation of an interfacial layer instead of modified silanes and probes for the specific detection of fragments of matrix troponin ribonucleic acid (analyte) as a marker of the cardiac infarction, is proposed. The influence of passivating the sensor surface activated by carbonyldiimidazole with glycine and aminoethanol at the final modification state on the response of sensors and the level of the background signal is investigated. It is shown that the proposed type of surface modification with glycine treatment provides a highly specific response of 60% in the case of a picomolar analyte concentration in the solution. Different mechanisms are responsible for an increase in the response and sensor specificity during analyte detection after passivation by glycine and aminoethanol.