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.

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.

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.

In this paper, we proposed the method for profiling of the components of the effective mobility of charge carriers μeff defined by their scattering by surface phonons and by roughness at the film/insulator interfaces. The method is based on the controlled localization of charge carriers relative to the interface under study due to the coupling effect. The proposed method allows us to independently determine mobility components near different interfaces of films. The use of the proposed method for studying the mobility has allowed us to obtain information on the roughness of the interface and on the structural quality of the ultrathin (1–3-nm) layer of Si near the Si/buried oxide interface.

A method for profiling the components of effective carrier mobility μeff determined by scattering at surface phonons and the roughness of thin film/dielectric interfaces is proposed. The method is based on controlled carrier localization relative to the tested heterointerface due to the interrelation of potentials on opposite film sides (the coupling effect). The method makes it possible to independently separate mobility components near different film heterointerfaces. Its use when studying the electron mobility in silicon-on-insulator films makes it possible to acquire information on the interface roughness and structural perfection of an ultrathin (1–3 nm) silicon layer near the buried film/dielectric interface.

Issues concerning the detection of biomolecular targets by biosensors based on silicon nanowire field-effect transistors are discussed. We list and discuss steps in the surface preparation of silicon nanowires that lead to the efficient, highly sensitive, and selective detection of various analytes. The procedures for cleaning and activation of the surface of the silicon nanowires are addressed. Wet and dry methods for surface cleaning as well as surface-modification strategies applicable to transducers of biosensors are described. Surface modification by silane derivatives (i.e., silanization) and linker attachment is paid particular attention. The causes underlying the undesirable screening effect affecting a nanowire surface upon analyte detection in solutions are provided. The key requirements and strategies relevant to different steps in the preparation of biosensor surfaces that lead to improvement in their performance are mentioned.

A method for forming p-n -diode based silicon electro-optic modulators using local oxidation is tested. It is shown that the local oxidation of silicon allows forming a rib waveguide as a smoothed trapezoid, in contrast to the classical technique of creating a rib waveguide by plasma-chemical etching. The main advantages of the approach used are described: controllability and reproducibility of critical design parameters of the modulators (width and height of the waveguide rib), low surface roughness, and the possibility of using approaches to forming a modulating p-n -diode of combined type in a rib waveguide, which are standard for planar technologies.

Two different approaches to the integration of self-assembled Ge(Si) quantum dots into two-dimensional photonic crystals are considered. One approach includes the synthesis of an ordered array of Ge(Si) quantum dots on the textured surface of a substrate followed by the formation of a photonic crystal on this array. In the other approach, the photonic crystal itself serves as a template for the ordered growth of quantum dots. It is shown that, by varying the diameter of holes of photonic crystals in the second approach, it is possible to implement the growth of quantum dots in two modes, in which quantum dots are formed inside or outside the holes of the photonic crystal. For structures with ordered quantum dots incorporated into a photonic crystal, an increase in the photoluminescence signal intensity is detected at room temperature in the spectral range 0.9–1.2 eV. This increase is attributed to the interaction of emission from the structure with radiation modes of the photonic crystal.

Nanowire SOI biosensors are used to detect the Ebola virus VP40 protein by identifying its immune complexes with specific monoclonal antibodies (MCAs). It is shown that the reaction of specific interaction between VP40 and MCAs causes a more pronounced biosensor response than direct adsorption of VP40 or antibodies to their surface. The formation of antigen — antibody complexes leads to the accumulation of a negative charge on the biosensor surface. The protein and protein — antibody complexes are detected in real time (∼200–300 s per test sample).

Two approaches to the integration of ordered Ge(Si) self-assembled quantum dots (QDs) into two-dimensional photonic crystals (PhC) are considered in the paper. The first approach involves the synthesis on the structured silicon surface of the ordered Ge(Si) QD array, on which PhC is then formed. In the second approach, the PhC itself serves as the template for the ordered QD growth. It is shown that varying the diameter of PhC holes in the framework of the second approach, two growth modes of QDs can be realized, when they are formed inside or outside the PhC holes. For structures with ordered QDs built into PhC, an increase in the intensity of the photoluminescence signal was detected at room temperature in the spectral range of 0.9-1.2 eV, which is associated with the interaction of the emission with the radiation modes of PhC.

This work demonstrates the possibility of detection of DNA-oligonucleotide (oDNA) and microRNAs (miRNAs) extracted from blood plasma and associated with breast cancer (BC) in a buffer solution using the nanowire (NW) biosensor based on the silicon-on-insulator (SOI) structures. For biospecific detection, the NW surface was modified with oligonucleotide probes (oDNA-probes) complementary to the well-known miRNA sequence. It has been shown that the SOI-NW biosensor with immobilized oDNA-probes of this type can be used to detect complementary oDNA in a buffer solution with a concentration sensitivity of 10(-17) M. The study also demonstrates the use of such biosensor for detection of an increased level of miRNAs isolated from the plasma of breast cancer patients. Application of the NW biosensor enables to distinguish between patients with a diagnosis of breast cancer from those with ovarian cancer (OC) by the value of an increased miRNAs level in the blood plasma of breast cancer patients. (C) 2018 Elsevier B.V. All rights reserved.

A method for creation of Ge/Si structures with space-arranged nanoislands by heteroepitaxy on the pre-patterned Si(001) substrates with a square grid of the etched pits is developed. The influence of depth and inter-pit spacing on the nucleation and growth of Ge(Si) nanoislands is studied. It is shown, that the nanoislands are formed either inside pits or at their periphery depending on the pit depth. It is found that the size of the nanoislands grown inside the pits goes up with the increase of the inter-pit distance from 1 to 4 μm. The pronounced photoluminescence signal related with the space-arranged arrays of quantum dots with a period of 1 μm is observed in the range of energies from 0.9 to 1.0 eV.

SOI-FET sensors are high-sensitivity analytical devices used for qualitative and quantitative analyses of biological and chemical substances. Decreasing and monitoring of the state density at surface of sensors are the key tasks to increase their sensitivity and reproducibility of parameters of devices. This study aims to apply the threshold voltage method to the SOI-FET sensor/electrolyte systems to determine the density of states in the sensors. For this aim: 1) a dependency between the sensor threshold voltage and the voltage on the electrode immersed in the electrolyte solution was derived, 2) the analytical and experimental dependencies were used to determine the density of states at the sensor surface Dit, 3) errors in Dit related to the uncertainty of values of components of the electrolyte capacitance were determined. It was shown that the uncertainty in the Dit values can be estimated in the process of measuring in solutions with various salt concentrations (1-100 mM). The maximal error in Dit related to the uncertainty of capacitance associated with the charge adsorbed on the sensor surface Qad can be estimated using the well-known design parameters of sensor, the salt concentration in solution and Qad=0. In particular, it was shown that for sensors with typical parameters (the buried oxide thickness of 200 nm, sensor thickness of 30 nm and top-oxide thickness of 2 nm) this error in Dit2 does not exceed 40% in the 100 mM buffer solutions. The threshold voltage method can be successfully applied for monitoring Dit at the stage of cleaning and activation of the sensor surface.

AbstractA method for creation of Ge/Si structures with space-arranged nanoislands by heteroepitaxy on the pre-patterned Si(001) substrates with a square grid of the etched pits is developed. The influence of depth and inter-pit spacing on the nucleation and growth of Ge(Si) nanoislands is studied. It is shown, that the nanoislands are formed either inside pits or at their periphery depending on the pit depth. It is found that the size of the nanoislands grown inside the pits goes up with the increase of the inter-pit distance from 1 to 4 μm. The pronounced photoluminescence signal related with the space-arranged arrays of quantum dots with a period of 1 μm is observed in the range of energies from 0.9 to 1.0 eV.

Исследована подвижность электронов mueff в инверсионных слоях двухзатворных полностью обедняемых КНИ (кремний-на-изоляторе) МОП транзисторов в зависимости от плотности индуцированных носителей заряда Ne и температуры T при разных режимах пленки КНИ со стороны одного из затворов (инверсия-обогащение). Показано, что при большой плотности индуцированных носителей заряда (Ne>6·1012 cм-2) зависимости mueff(T) позволяют выделить компоненты подвижности mueff, связанные с рассеянием на поверхностных фононах и микрорельефе границы раздела пленка/диэлектрик. Зависимости mueff(Ne) могут быть аппроксимированы степенными функциями mueff(Ne) propto Ne-n. Определены значения показателей n зависимостей и доминирующие механизмы рассеяния электронов, индуцированных вблизи границы раздела пленки КНИ со скрытым диэлектриком, для различных интервалов Ne и режимов пленки со стороны поверхности. DOI: 10.21883/FTP.2017.04.44334.8369

The dependences of the electron mobility μeff in the inversion layers of fully depleted double–gate silicon-on-insulator (SOI) metal–oxide–semiconductor (MOS) transistors on the density N e of induced charge carriers and temperature T are investigated at different states of the SOI film (inversion–accumulation) from the side of one of the gates. It is shown that at a high density of induced charge carriers of N e > 6 × 1012 cm–2 the μeff(T) dependences allow the components of mobility μeff that are related to scattering at surface phonons and from the film/insulator surface roughness to be distinguished. The μeff(N e ) dependences can be approximated by the power functions μeff(N e) ∝ N e −n . The exponents n in the dependences and the dominant mechanisms of scattering of electrons induced near the interface between the SOI film and buried oxide are determined for different N e ranges and film states from the surface side.

Nanowire field-effect transistors are highly sensitive sensor elements used for qualitative and quantitative analyses of biological and chemical substances. Optimization of the operation of the sensor is one of the key ways of increasing their sensitivity. An algorithm for choosing the operation mode of sensors based on silicon-on-insulator transistors is proposed which provides their maximum response during conductivity monitoring in the detection of target particles.

A method for detection of cancer-associated protein D-NFATc1 in serum using nanowire (NW) biosensor based on field-effect nanotransistor is developed. Field-effect nanotransistor was fabricated on the basis of «silicon-on-insulator» structures. For the biospecific detection of target protein, the NW surface was modified with aptamers against the target protein. Using the 3 um-NW enabled to obtain stable source-drain characteristics and to register D-NFATc1 in serum at concentration of 2.5 x 1014 M in the mode of drain-source current vs. gate voltage characteristics measurements. Data collection in the mode of drain-source current vs. gate voltage characteristics measurements was carried out with the use of high-speed data collection system running TURBO NBS software.